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Tumor surveillance via the ARF-p53 pathway

Tumor surveillance via the ARF-p53 pathway Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press PERSPECTIVE Tumor surveillance via the ARF–p53 pathway Charles J. Sherr Howard Hughes Medical Institute, Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105 USA INK4a The retinoblastoma (Rb) and p53 genes are not essential function of one of the two negative regulators (p16 for completion of the cell division cycle, but disruption or Rb) or from events leading to overexpression of one of of their functions is central to the life history of most, if the two proto-oncogenes (cyclin D1 or cdk4) (for review, not all, cancer cells (for review, see Weinberg 1995; Sherr see Weinberg 1995; Sherr 1996; Ruas and Peters 1998). 1996; Levine 1997). Surprisingly, Rb and p53 are them- The p53 protein is a transcription factor that can in- selves regulated by two proteins encoded by a single hibit cell cycle progression or induce apoptosis in re- genetic locus, INK4a/ARF, the products of which, sponse to stress or DNA damage, and inactivation of p53 INK4a ARF p16 and p19 , are also potent tumor suppressors. attenuates both of these cellular responses (for review, INK4a The role of p16 as an inhibitor of cyclin D-depen- see Ko and Prives 1996; Levine 1997; Giaccia and Kastan dent kinases has been appreciated since its discovery 1998). Elimination of functional p53 through various (Serrano et al. 1993). Now, emerging evidence is provid- mechanisms is the single most common event in human ing valuable insights into the molecular circuitry cancer, occurring in over half of all tumors (Hollstein et ARF through which p19 modulates p53 activity as part of al. 1994). The p53 protein is short-lived and expressed at a checkpoint response to oncogenic, hyperproliferative very low levels in normal cells but it is stabilized and signals. accumulates in cells that have sustained genotoxic dam- age (Fig. 1). Among the gene products induced by p53 is Cip1/Waf1 the cdk inhibitor p21 , which can effect cell Regulation of cell cycle progression by pRb and p53 cycle arrest (El-Deiry et al. 1993; Harper et al. 1993; Xiong et al. 1993). Another key target is Mdm2, which During most of G phase of the mammalian cell cycle, acts in a feedback loop to limit the action of p53 (Barak Rb in its hypophosphorylated form binds to several tran- et al. 1993; Wu et al. 1993), both by inhibiting its trans- scription factors of the E2F family, constraining their activating activity and by catalyzing its destruction activity on some promoters and actively repressing tran- (Haupt et al. 1997; Honda et al. 1997; Kubbutat et al. scription from others (see Dyson 1998). Phosphorylation 1997). Mutation of p53 compromises cell cycle arrest, of Rb by cyclin-dependent kinases (cdks) in the mid-to- attenuates apoptosis induced by DNA damage, predis- late G phase of the cycle untethers Rb from the E2Fs. In poses cells to drug-induced gene amplification, affects turn, this enables the E2Fs to activate a series of target centrosome duplication, and rapidly leads to changes in genes, the expression of which is required for cells to chromosome number and ploidy (Kastan et al. 1991, enter S phase, thereby stimulating proliferation (Fig. 1). 1992; Kuerbitz et al. 1992; Livingstone et al. 1992; Yin et The cyclin D-dependent kinases cdk4 and cdk6 trigger al. 1992; Clarke et al. 1993; Lowe and Ruley 1993; Lowe Rb phosphorylation, which is likely completed by cyclin et al. 1993; Fukusawa et al. 1996; Jacks and Weinberg E–cdk2 as cells approach the G -to-S phase transition. 1996; Hermeking et al. 1997; Paulovich et al. 1997; Gu- Because induction and assembly of cyclin D-dependent alberto et al. 1998; Lanni and Jacks 1998). The resulting kinases is dependent on mitogenic signaling, cancella- genomic instability greatly increases the probability that tion of Rb’s growth-suppressive activity is coupled to p53-null cells will evolve toward malignancy. extracellular stimuli. By inhibiting cdk4 and cdk6, a Cooperation between the Rb and p53 pathways has family of INK4 proteins can prevent cells with func- been amply demonstrated. Classic examples involve on- tional Rb from entering S phase. The prototypic member, coproteins encoded by the DNA tumor viruses, which INK4a p16 (Serrano et al. 1993), is distinguished from its both cancel Rb function to drive cells into S phase and INK4b INK4c INK4d close relatives (p15 , p18 , and p19 )inits neutralize p53 to prevent host cell suicide (for review, role as a potent tumor suppressor. Disruption of the see White 1996). Loss of function by Rb and related fam- INK4a p16 –cyclin D1/cdk4–Rb pathway is a common ily members can bypass p53-mediated G arrest (Demers event in human cancer, either resulting from loss of et al. 1994; Slebos et al. 1994), but Rb loss induces E2F and p53-dependent apoptosis (Lowe and Ruley 1993; E-MAIL [email protected]; FAX (901) 495-2381. Howes et al. 1994; Morgenbesser et al. 1994; Pan and 2984 GENES & DEVELOPMENT 12:2984–2991 © 1998 by Cold Spring Harbor Laboratory Press ISSN 0890-9369/98 $5.00; www.genesdev.org Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press ARF tumor suppression Figure 1. ARF checkpoint control. ARF re- sponds to proliferative signals that are nor- mally required for cell proliferation. When these signals exceed a critical threshold, the ARF-dependent checkpoint (gray vertical bar- rel) is activated, and ARF triggers a p53-depen- dent response that induces growth arrest and/ or apoptosis. Signals now known to induce sig- naling via the ARF–p53 pathway include Myc, E1A, and E2F-1. In principle, ‘upstream’ onco- proteins, such as products of mutated Ras alle- les, constitutively activated receptors, or cyto- plasmic signal transducing oncoproteins, might also trigger ARF activity via the cyclin D– cdk4–Rb–E2F or Myc-dependent pathways, both of which are normally necessary for S- phase entry. In inhibiting cyclin D-dependent INK4a kinases, p16 can dampen the activity of mitogenic signals. E1A is shown to work, at least in part, by canceling Rb function, although its ability to inhibit p300 contributes to the response by interfering with mdm2 expression. Again for simplicity, Myc and E2F-1 are only shown to activate p53 via ARF. However, highly overexpressed levels of these proteins can activate p53 in ARF-negative cells, albeit with an attenuated efficiency. ARF activation of p53 likely depends on inactivation of some Mdm2-specific function (implied by the unfilled box bracketing the latter two proteins). DNA damage signals (ionizing and UV radiation, hypoxic stress, genotoxic drugs, etc.) access p53 through multiple signaling pathways shown, again for simplicity, as a single DNA damage checkpoint (gray horizontal barrel). Signals through the ARF and DNA damage pathways can synergize in activating p53. Griep 1994; Qin et al. 1994; Shan et al. 1994; Symonds et frame (ARF) of exon 2 (Quelle et al. 1995). The human al. 1994; Wu and Levine 1994). In short, mutational protein terminates farther upstream in exon 2 and it has INK4a ARF events that disable the p16 –cyclin D1/cdk4–Rb a predicted molecular mass of only 14 kD. Mouse p19 ARF pathway and enforce cell proliferation are counterbal- and human p14 are highly basic nuclear proteins that anced by a p53-dependent apoptotic response that can induce G - and G -phase arrest when introduced into a 1 2 eliminate incipient cancer cells. The ability of E2F to variety of different cell types (Quelle et al. 1995; Stott et trigger p53-dependent cell suicide implies that a bio- al. 1998). INK4a/ARF-null cells are susceptible to ARF- ARF chemical connection links their functions. Other cellu- induced arrest, so this activity of p19 does not depend INK4a lar oncogenes, such as myc, also induce p53-dependent upon p16 . apoptosis (Hermeking and Eick 1994; Wagner et al. Mutations that inactivate the cdk inhibitory function INK4a 1994). Hence, p53 is not only activated by DNA damage, of p16 occur frequently in a wide spectrum of hu- but it provides an ‘oncogene checkpoint’ function that man cancers (for review, see Ruas and Peters 1998). For guards cells against hyperproliferative signals (for re- example, certain inactivating point mutations impinge view, see Van Dyke 1994; Jacks and Weinberg 1996; on exon 1a, some of which are inherited in melanoma White 1996; Levine 1997). This is the setting in which kindreds (Kamb et al. 1994a,b; Gruis et al. 1995). Al- ARF p19 plays a key role. though many point mutations in exon 2 of INK4a are ARF also predicted to alter p19 , those that have been tested experimentally have been found to inactivate The INK4a/ARF locus and tumor suppression INK4a ARF p16 without affecting the ability of p19 to in- The manner by which a single genetic locus encodes duce cell cycle arrest. Moreover, the amino-terminal INK4a ARF both p16 and p19 is unprecedented in mammals moiety of ARF (amino acids 1–64), encoded entirely by INK4a (Quelle et al. 1995) (Fig. 2). p16 is encoded by three exon 1b, is sufficient to induce cell cycle arrest when overexpressed (Quelle et al. 1997; Zhang et al. 1998), closely linked exons (designated 1a, 2, and 3). An RNA segment arising from an alternative first exon (1b), although tumor-specific point mutations in this domain which maps 13–20 kb upstream in the human, mouse, have not been described (Stone et al. 1995; Ruas and INK4a and rat genomes, is spliced to exon 2, yielding a b tran- Peters 1998). Together, these data suggest that p16 script that is almost identical in size to the a transcript is disrupted frequently by point mutations in human INK4a ARF that encodes p16 (Duro et al. 1995; Mao et al. 1995; cancer, but p19 is not. However, the common occur- Quelle et al. 1995; Stone et al. 1995; Swafford et al. 1997). rence of homozygous deletions of INK4a/ARF in a wide The initiator codon in exon 1b is not in frame with se- range of human tumors leaves open the possibility that INK4a quences encoding p16 in exon 2, so the b transcript ARF plays an independent role as a tumor suppressor (see specifies a novel polypeptide. In the mouse, this 19-kD below). protein consists of 65 amino acids encoded by exon 1b, Functional ablation of INK4a/ARF in mice by elimi- and 105 amino acids arising from the alternative reading nation of exons 2 and 3 (Fig. 2) revealed that derived GENES & DEVELOPMENT 2985 Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press Sherr phenotype was indistinguishable from that attributed INK4a previously to p16 disruption (Kamijo et al. 1997). INK4a Importantly, functional p16 was expressed in nor- mal tissues of ARF-null mice, in cultured MEFs, and in cells from spontaneously arising tumors. Therefore, ARF functions as a bona fide tumor suppressor, and the phe- notype initially ascribed to INK4a loss is instead likely due to ARF inactivation. In turn, the phenotypic conse- Figure 2. The INK4a/ARF locus. Genomic sequences encod- INK4a INK4a quences of p16 loss in mice remain uncertain, and ing p16 are defined by completely filled regions within the construction of a pure INK4a knockout strain is war- boxes designating exons 1a, 2, and 3, whereas the segments of exons 1b and 2 that encode ARF are defined by shaded areas. ranted. Unfilled portions of the exons correspond to noncoding 58 and 38 regions. Splicing between the exons is indicated by the connect- The ARF–p53 pathway ing lines, and exons 1a and 1b are indicated to have separate promoters (→). In the mouse genome, the alternative first exons A cardinal feature of ARF-null MEFs is their capacity to are separated by ~13 kb of intervening sequences. Segments of grow as established cell lines and to be transformed by the genes that were disrupted by Serrano et al. (1996) and Ka- oncogenic ras genes alone (Kamijo et al. 1997). Approxi- mijo et al. (1997) are designated by horizontal lines below the mately 20% of spontaneously established fibroblast cell schematic. lines derived from MEFs of wild-type mice undergo bi- allelic ARF loss. MEF strains that are hemizygous for ARF lose their remaining functional ARF allele and nullizygous animals were highly prone to tumor devel- spontaneously immortalize at a faster rate than wild- opment (Serrano et al. 1996). Tumors arose early in life, type strains. In each case, established MEF cell lines that and their appearance was accelerated by irradiation of lacked ARF preserved p53 function, whereas those that newborn mice or by their treatment with chemical car- retained ARF had sustained p53 mutations. These re- ARF cinogens. Intriguingly, mouse embryo fibroblasts (MEFs) sults suggested that p19 and p53 might function in explanted from the INK4a/ARF knock-out mice did not the same biochemical pathway. Consistent with this hy- undergo replicative senescence in culture. Like many es- pothesis, cells lacking a functional p53 gene are resistant ARF tablished mouse cell lines, but unlike normal primary to p19 -induced cell cycle arrest, implying that p53 MEFs, they could be transformed by oncogenic ras alle- acts downstream of ARF (Kamijo et al. 1997). However, les without a requirement for so-called immortalizing ARF-null cells exhibit an intact p53 checkpoint follow- ARF oncogenes such as myc or adenovirus E1A. MEFs from ing ionizing or UV irradiation, so p19 does not relay p53-null mice exhibit similar properties (Harvey et al. signals to p53 in response to DNA damage (Fig. 1). Loss 1993), and p53-inactivating mutations are the most com- of p53 can occur in cancer cells that arise in ARF-null mon single events in the spontaneous conversion of MEF mice, again indicating that ARF plays a more specialized strains into continuously growing cell lines (Harvey and role in tumor suppression than p53, and that selection Levine 1991). Results with both INK4a/ARF-null or p53- against p53 can further contribute to malignancy (Ka- null MEFs directly contrast with those obtained with mijo et al. 1997). normal primary MEF strains, in which introduction of Evidence supporting direct biochemical interactions ARF oncogenic ras instead provokes a state of growth arrest between p19 and p53 is now in hand. Ectopic ARF resembling senescence, associated with accumulation of expression stabilizes p53 and induces p53-responsive INK4a both p53 and p16 (Serrano et al. 1997). Initially, it genes, Mdm2 among them. ARF can physically interact was reasoned that the phenotype observed in INK4a/ with Mdm2, and its binding blocks both Mdm2-induced INK4a ARF-null mice depended on the loss of p16 function p53 degradation and transactivational silencing (Kamijo INK4a (Serrano et al. 1996). It followed that both p16 and et al. 1998; Pomerantz et al. 1998; Stott et al. 1998; p53 acted as determinants of cell senescence in MEFs, Zhang et al. 1998). The interaction between Mdm2 and ARF with the loss of either leading to establishment and im- p19 depends on the carboxy-terminal half of Mdm2 mortalization. Release of the senescence block by dis- and on the ARF amino-terminus (i.e., the active exon INK4a ruption of p16 or p53 would be necessary for trans- 1b-coded segment) (Zhang et al. 1998). Because Mdm2 formation of mouse fibroblasts by oncogenic ras (Serrano binds to p53 through its amino-terminal domain, ARF et al. 1997; for review, see Weinberg 1997). A persistent can enter into ternary complexes with both Mdm2 and ambiguity is whether these mice lack ARF function p53. ARF completely. This is likely, because the targeting cassette Although human p14 appears not to interact with disrupted the mRNA polyadenylation signals as well as p53 directly (Pomerantz et al. 1998; Stott et al. 1998; the INK4a and ARF carboxy-terminal coding equences Zhang et al. 1998), there is some evidence that the (Fig. 2). However, the issue formally remains unresolved, mouse ARF protein can bind to p53 even in the absence because it is conceivable that a truncated ARF protein of Mdm2 (Kamijo et al. 1998). For example, in electro- might somehow arise from undisrupted exon 1b. phoretic mobility shift assays performed with purified, Surprisingly, when pure ARF-null mice were created activated p53 and a labeled oligonucleotide containing that lacked only the exon 1b sequences (Fig. 2), their tandem p53 consensus DNA-binding sites from the 2986 GENES & DEVELOPMENT Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press ARF tumor suppression Cip1 ARF p21 promoter, addition of recombinant p19 re- p53 complexes in the nucleolus, preventing their degra- tarded the mobility of the p53–oligonucleotide com- dation in the cytoplasm. plexes. In these assays, the otherwise latent DNA-bind- Finally, in cells lacking p53, ARF levels are signifi- ing capability of p53 needed to be activated by antibodies cantly elevated (Quelle et al. 1995; Stott et al. 1998), but ARF directed to a carboxy-terminal p53 epitope, and p19 reintroduction of wild-type p53 into p53-null MEFs can ARF was unable to substitute for the antibody in activating restore p19 to normal levels (Kamijo et al. 1998). DNA binding. These observations raise the possibility Similarly, in human Saos-2 osteosarcoma cells lacking ARF ARF that interactions between p19 endogenous p53 function, expression of p14 and p53 can occur on was chromatin, although there is no direct evidence that ARF down-regulated when cells were induced to express ei- plays any physiologic role as a p53 coactivator. ther tetracycline-regulated or temperature-sensitive p53 ARF requires p53 to induce growth arrest, but the di- (Stott et al. 1998). Therefore, not only can ARF stabilize ARF rect physical interactions among p19 , p53, and p53, but ARF expression is in turn controlled by p53 Mdm2 in various binary and ternary complexes suggest through negative feedback. Again, the underlying that some p53 functions may reciprocally depend on mechanism needs to be clarified. Among the possibili- ARF ARF. Overexpression of p19 in ARF-null NIH-3T3 ties is that the ARF gene might be repressed by p53, or Cip1 cells induced expression of a p21 promoter-driven re- the ARF protein could itself be a target of Mdm2-induced porter gene in a manner that depended on endogenous turnover. p53. Paradoxically, ectopic overexpression of wild-type p53 itself in ARF-null cells did not activate the reporter, indicating that simple increases in the amount of p53 Oncogenic signals induce ARF were insufficient to activate transcription in this setting. p53-Dependent reporter gene expression was restored The fact that ARF-null MEFs grow as established cell when subliminal amounts of ARF expression vector lines and can be transformed by oncogenic ras mimics were reintroduced together with increasing concentra- effects induced by so-called immortalizing oncogenes, ARF tions of p53,sop19 can provide some type of activat- like myc and E1A (Land et al. 1983; Ruley 1983). It there- ing signal that facilitates p53-dependent transcription fore seems paradoxical that myc and E1A are also potent (Kamijo et al. 1998). In this respect, the functions of p53 inducers of apoptosis (Askew et al. 1991; White et al. ARF and p19 are interdependent. 1991; Evan et al. 1992; Rao et al. 1992), a process aggra- Zhang and colleagues (1998) reported that ARF accel- vated by depriving MEFs of serum survival factors (Evan erated Mdm2 turnover in HeLa cells cotransfected with et al. 1992; Lowe et al. 1993). These contrasting out- vectors encoding ARF and Mdm2. They proposed that comes of Myc and E1A action—extended life versus ac- destabilization of Mdm2 by ARF was the mechanism celerated death—can be reconciled by observations that underlying p53 accumulation. However, experiments by their overexpression provides a strong selective pressure others have yielded conflicting results. The idea that for events that dismantle apoptotic signaling pathways, ARF destabilizes Mdm2 seems to be at odds with obser- with ARF being a key target. vations that ARF activation in MEFs induces endog- Overexpression of Myc, E1A, or E2F-1 in primary enous Mdm2 to accumulate in a p53-dependent manner MEFs rapidly induces ARF gene expression and leads to (de Stanchina et al. 1998; Kamijo et al. 1998; Zindy et al. p53-dependent apoptosis. However, ARF-null and p53- 1998). Stott and coworkers (1998) confirmed that in a null MEFs resist these effects (de Stanchina et al. 1998; variety of cell types cotransfected with Mdm2 and p53, Zindy et al. 1998). Similarly, wild-type or ARF hemizy- introduction of ARF overcame the ability of Mdm2 to gous MEFs that survive Myc overexpression generally induce p53 degradation. However, in the presence or ab- sustain either p53 mutation or ARF loss, but not both, sence of exogenous p53, ARF caused Mdm2 to accumu- rapidly yielding established cell lines that tolerate supra- late. Moreover, coexpression of the E6 protein of human physiologic Myc levels even in the absence of survival papilloma virus 16, which independently targets p53 for factors (Zindy et al. 1998). Myc and E1A can induce p53 degradation, did not interfere with the ability of ARF to through both ARF-dependent and ARF-independent pathways, but much higher levels of oncoprotein expres- stabilize cotransfected Mdm2. Minimally, it seems rea- sonable to conclude that ARF can antagonize Mdm2 sion are required to activate p53 when ARF is absent. function through a mechanism that does not depend on Under the latter conditions, the p53 response is attenu- increased Mdm2 turnover. ated and cells resistant to oncogene-induced killing rap- ARF How, then, does ARF stabilize p53? One possibility is idly emerge. Reintroduction of p19 into surviving that ARF interferes with Mdm2’s ability to trigger p53 ARF-null cells expressing either Myc or E1A resensitizes polyubiquitination. Supporting this idea, Mdm2 seems them to apoptosis, indicating that the attenuation of to induce the appearance of polyubiquitinated forms of death is a direct consequence of ARF loss and does not p53, which are much less abundant in cells that overex- result from other cryptic mutations. Therefore, Myc, ARF ARF press p19 (Pomerantz et al. 1998). Mdm2 and p19 E1A, and E2F-1 trigger a p53-dependent oncogene check- also colocalize in the nucleoli of cells transfected with point gated by ARF (Fig. 1). Although the ARF–p53 path- both genes (Pomerantz et al. 1998). Because p53 degra- way is not essential for normal proliferation, the check- dation depends upon its Mdm2-mediated nuclear export point could provide a fail-safe function during embryonic (Roth et al. 1998), ARF could conceivably retain Mdm2– development. For example, in a model of the developing GENES & DEVELOPMENT 2987 Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press Sherr murine lens, Rb deficiency triggers apoptosis in a p53- ARF in human cancer dependent manner (Morgenbesser et al. 1994), but the Much of the experimental work on ARF to date has in- process is attenuated in lenses from animals lacking volved murine systems. Senescence (and conversely, im- INK4a/ARF (Pomerantz et al. 1998). mortalization) of human cells is likely to be subject to One component of the E1A response involves its abil- additional and more stringent controls, particularly in ity to activate p300, a coactivator required for p53-de- light of our longer life span. Whereas p53 and Rb inacti- pendent mdm2 transcription (Thomas and White 1998). vation can endow human fibroblasts with increased pro- But the ability of E1A to induce ARF in MEFs is likely liferative potential, cells lacking these functions are not mediated by the E2Fs, as E1A mutants that bind p300 immortal, and chromosomal telomere shortening soon but do not interact with Rb are highly defective in this limits continued cell proliferation (Bodnar et al. 1998). In regard (de Stanchina et al. 1998) (Fig. 1). Conditional ex- contrast, mouse chromosomes have much longer telo- pression of E2F-1 in Saos-2 cells was followed temporally meres, and mice lacking telomerase activity must be by increased ARF mRNA and protein expression (Bates bred through many generations before the deleterious et al. 1998). Cotransfection experiments indicated that effects of telomere shortening are manifest (Blasco et al. wild-type E2F-1 activated transcription from a minimal 1997; Lee et al. 1998). ARF promoter, whereas an E2F-1 mutant defective in Despite fundamental differences of this type, ARF is transactivation was devoid of activity. Despite the fact likely to function as a tumor suppressor in humans. Cer- ARF that Myc also induces p19 to accumulate very rapidly tain cancers such as melanomas, biliary tumors, non- (Zindy et al. 1998), it is presently unclear whether Myc small cell lung carcinomas, pancreatic, and esophageal activates the ARF promoter directly. carcinomas frequently sustain INK4a point mutations. Cooperation between myc and oncogenic ras (Land et Other tumor types, however, such as T- and B-cell acute al. 1983; Ruley 1983) can be viewed to involve the ARF– lymphoblastic leukemias, bladder and nasopharyngeal p53 pathway indirectly. Cultured MEFs achieve replica- carcinomas, mesotheliomas, anaplastic astrocytomas, tive immortality by inactivating ARF or p53, and by pro- and glioblastoma multiforme routinely exhibit INK4a/ moting cell death, oncogenes such as E1A and myc pro- ARF deletions rather than point mutations (Ruas and vide a strong selective pressure for disabling ARF or p53 Peters 1998). Whether or not these homozygous dele- ARF function. Because enforced expression of p19 arrests tions target both ARF and INK4a or ARF alone, their wild-type MEFs but does not kill them (Quelle et al. high frequency of occurrence strongly argues that ARF 1995), other functions of Myc and E1A in addition to loss contributes significantly to human cancer. This ARF induction are required for this process. The growth makes good sense. If p53 is directly targeted in >50% of promoting properties of Myc and E1A are important be- human malignancies, then p53-positive tumors have cause without them, the selection for immortal cells likely sustained epistatic mutations such as Mdm2 am- would likely not occur. This is even more obvious in plification or ARF loss. The concept that ARF monitors other cell types in which transformation and tumorigen- proliferative signals rather than DNA damage helps to esis strongly depend upon Myc’s growth promoting func- expand our understanding of p53 action and provides a tions even in the absence of p53 (see, for example, Metz further rationale for ARF inactivation through chromo- et al. 1995). In turn, Myc and E1A seem to inactivate somal deletion in many forms of cancer. cellular responses that are normally required for Ras- mediated inhibition of cell proliferation, thereby con- verting ras into a growth-promoting gene (Franza et al. 1986; Hicks et al. 1991; Hirakawa et al. 1991; Lloyd et al. Acknowledgments 1997; Serrano et al. 1997). The fact that oncogenic ras I thank Martine F. Roussel, John Cleveland, Gerry Zambetti, alone can transform MEFs lacking ARF or p53 argues Tom Curran, A. Thomas Look, Suzy Baker, Peter McKinnon, that their inactivation is key. ARF Scott W. Lowe, Ron DePinho, Tyler Jacks, Manuel Serrano, and Because p19 addresses p53 through a pathway that Terry Van Dyke for stimulating and helpful discussions, and is distinct from those activated by DNA damage (Fig. 1), Dawn Quelle, Frederique Zindy, Takehiko Kamijo, Jason We- induction of ARF by oncogenes may sensitize cells to the ber, and Mangeng Cheng for contributing critical data pertinent effects of genotoxic drugs that are used to treat cancer. to the work from the Sherr and Roussel laboratories. C.J.S. is an Indeed, MEFs expressing E1A are significantly more sen- investigator of the Howard Hughes Medical Institute and also sitive to killing by adriamycin than their normal coun- acknowledges support from the American Lebanese Syrian As- terparts, whereas E1A-expressing ARF-null MEFs no sociated Charities (ALSAC) of St. Jude Children’s Research Hos- longer manifest this synergy (de Stanchina et al. 1998). pital. The ability of ARF to sense hyperproliferative stimuli must be important in tumor surveillance, because ARF loss strongly predisposes to spontaneous cancer develop- References ment and accelerates the frequency of tumor induction by irradiation or carcinogens (Serrano et al. 1996; Kamijo Askew, D.S., R.A. Ashmun, B.C. Simmons, and J.L. Cleveland. et al. 1997). Indeed, in the absence of ARF emergence of 1991. Constitutive c-myc expression in an IL3-dependent p53-negative tumor cells that are resistant to DNA dam- myeloid cell line suppresses cell cycle arrest and accelerates aging agents should still occur (Fig. 1). apoptosis. Oncogene 6: 1915–1922. 2988 GENES & DEVELOPMENT Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press ARF tumor suppression Barak, Y., T. Juven, R. Haffner, and M. Oren. 1993. Mdm2 ex- P. Pantazis, B.C. Giovanella, M.A. Tainsky, A. Bradley, and pression is induced by wild type p53 activity. EMBO J. L.A. Donehower. 1993. In vitro growth characteristics of em- 12: 461–468. bryo fibroblasts isolated from p53-deficient mice. Oncogene Bates, S., A.C. Phillips, P. Clarke, F. Stott, G. Peters, R.L. Lud- 8: 2457–2467. ARF wig, and K.H. Vousden. 1998. E2F-1 regulation of p14 Haupt, Y., R. Maya, A. Kazaz, and M. Oren. 1997. Mdm2 pro- links pRB and p53. Nature (in press). motes the rapid degradation of p53. Nature 387: 296–299. Blasco, M.A., H.-W. Lee, M.P. Hande, E. Samper, P.M. Lansdorp, Hermeking, H. and D. Eick. 1994. Mediation of c-Myc-induced R.A. DePinho, and C.W. Greider. 1997. Telomere shortening apoptosis by p53. Science 265: 2091–2093. and tumor formation by mouse cells lacking telomerase Hermeking, H., C. Lengauer, K. Polyak, T.-C. He, L. Zhang, S. RNA. Cell 91: 25–34. Thiagalingam, K.W. Kinzler, and B. Vogelstein. 1997. 14-3- Bodnar, A.G., M. Ouellette, M. Frolkis, S.E. Holt, C.-P. Chiu, 3s is a p53-regulated inhibitor of G2/M progression. Mol. G.B. Morin, C.B. Harley, J.B. Shay, S. Lichsteiner, and W.E. Cell 1: 3–11. Wright. 1998. Extension of life-span by introduction of Hicks, G.C., S.E. Egan, A.H. Greenberg, and M. Mowat. 1991. telomerase into normal human cells. Science 279: 349–352. Mutant p53 tumor suppressor alleles release ras-induced cell Clarke, A.R., C.A. Purdie, D.J. Harrison, R.G. Morris, C.C. Bird, cycle growth arrest. Mol. Cell. Biol. 11: 1344–1352. M.L. Hooper, and A.H. Wyllie. 1993. Thymocyte apoptosis Hirakawa, T. and H.E. Ruley. 1991. Rescue of cells from ras induced by p53-dependent and independent pathways. Na- oncogene-induced growth arrest by a second complementing ture 362: 849–852. oncogene. Proc. Natl. Acad. Sci. 85: 1519–1523. de Stanchina, E., M.E. McCurrach, F. Zindy, S.-Y. Shieh, G. Hollstein, M., K. Rice, M.S. Greenblatt, T. Soussi, R. Fuchs, T. Ferbeyre, A.V. Samuelson, C. Prives, M.F. Roussel, C.J. Sorlie, E. Hovig, B. Smith-Sorensen, R. Montesano, and C.C. Sherr, and S.W. Lowe. 1998. E1A signaling to p53 involves Harris. 1994. Database of p53 gene somatic mutations in ARF the p19 tumor suppressor. Genes & Dev. 12: 2435–2443. human tumors and cell lines. Nucleic Acids Res. 22: 3551– Demers, G.W., S.A. Foster, C.L. Halbert, and D.A. Galloway. 3555. 1994. Growth arrest by induction of p53 in DNA damaged Honda, R., H. Tanaka, and H. Yasuda. 1997. Oncoprotein keratinocytes is bypassed by human papillomavirus 16 E7. MDM2 is a ubiquitin ligase E3 for tumor suppressor p53. Proc. Natl. Acad. Sci. 91: 4382–4386. FEBS Lett. 420: 25–27. Duro, D., O. Bernard, V. Della Valle, R. Berger, and C.-J. Larsen. Howes, K.A., N. Ransom, D.S. Papermaster, J.G.H. Lasudry, INK4/MTS1 1995. A new type of p16 gene transcript expressed D.M. Albert, and J.J. Windle. 1994. Apoptosis or retinoblas- in B-cell malignancies. Oncogene 11: 21–29. toma: Alternative fates of photoreceptors expressing the Dyson, N. 1998. The regulation of E2F by pRb-family members. HPV-16 E7 gene in the presence or absence of p53. Genes & Genes & Dev. 12: 2245–2262. Dev. 8: 1300–1310. El-Deiry, W.S., T. Tokino, V.E. Velculescu, D.B. Levy, R. Par- Jacks, T. and R.A. Weinberg. 1996. Cell-cycle control and its sons, J.M. Trent, D. Lin, E. Mercer, K.W. Kinzler, and B. watchman. Nature 381: 643–644. Vogelstein. 1993. WAF1, a potential mediator of p53 tumor Kamb, A., N.A. Gruis, J. Weaver-Feldhaus, Q. Liu, K. Harshman, suppression. Cell 75: 817–825. S.V. Tavtigian, E. Stockert, R.S. Day, III, B.E. Johnson, and Evan, G.I., A.H. Wyllie, C.S. Gilbert, T.D. Littlewood, H. Land, M.H. Skolnick. 1994a. A cell cycle regulator involved in gen- M. Brooks, C.M. Water, L.Z. Penn, and D.C. Hancock. 1992. esis of many tumor types. Science 264: 436–440. Induction of apoptosis in fibroblasts by c-myc protein. Cell Kamb, A., D. Shattuck-Eidens, R. Eeles, Q. Liu, N.A. Gruis, W. 69: 119–128. Ding, C. Hussey, T. Tran, Y. Miki, J. Weaver-Feldhaus, M. Franza, B.R., K. Maruyama, J.I. Garrels, and H.E. Ruley. 1986. In McClure, J.F. Aitken, D.E. Anderson, W. Bergman, R. Frants, vitro establishment is not sufficient prerequisite for trans- D.E. Goldgar, A. Green, R. MacLennan, N.G. Martin, L.J. formation by activated ras oncogene. Cell 44: 409–418. Meyer, P. Youl, J.J. Zone, M.H. Skolnick, and L.A. Cannon- Fukusawa, K., T. Choi, R. Kuriyama, S. Rulong, and G.F. Vande Albright. 1994b. Analysis of the p16 gene (CDKN2) as a can- Woude. 1996. Abnormal centrosome amplification in the ab- didate for the chromosome 9p melanoma susceptibility lo- sence of p53. Science 271: 1744–1747. cus. Nature Genet. 8: 22–26. Giaccia, A.J. and M.B. Kastan. 1998. The complexity of p53 Kamijo, T., F. Zindy, M.F. Roussel, D.E. Quelle, J.R. Downing, modulation: Emerging patterns from divergent signals. R.A. Ashmun, G. Grosveld, and C.J. Sherr. 1997. Tumor sup- Genes & Dev. 12: (this issue). pression at the mouse INK4a locus mediated by the alterna- ARF Gruis, N.A., P.A. van der Velden, L.A. Sandkuijl, D.E. Prins, J. tive reading frame product p19 . Cell 91: 649–659. Weaver-Feldhaus, A. Kamb, W. Bergman, and R. Frants. Kamijo, T., J.D. Weber, G. Zambetti, F. Zindy, M.F. Roussel, 1995. Homozygotes for CDKN2 (p16) germline mutation in and C.J. Sherr. 1998. Functional and physical interactions of Dutch familial melanoma kindreds. Nat. Genet. 10: 351– the ARF tumor suppressor with p53 and Mdm2. Proc. Natl. 353. Acad. Sci. 95: 8292–8297. Gualberto, A., K. Aldape, K. Kozakiewicz, and T.D. Tlsty. 1998. Kastan, M.B., O. Onyekwere, D. Sidransky, B. Vogelstein, and An oncogenic form of p53 confers a dominant, gain-of-func- R.W. Craig. 1991. Participation of p53 protein in the cellular tion phenotype that disrupts spindle checkpoint control. response to DNA damage. Cancer Res. 51: 6304–6311. Proc. Natl. Acad. Sci. 95: 5166–5171. Kastan, M.B., Q. Zhan, W.S. El-Deiry, F. Carrier, T. Jacks, W.V. Harper, J.W., G.R. Adami, N. Wei, K. Keyomarsi, and S.J. Walsh, B.S. Plunkett, B. Vogelstein, and A.J. Fornace, Jr. Elledge. 1993. The p21 cdk-interacting protein Cip1 is a po- 1992. A mammalian cell cycle checkpoint pathway utilizing tent inhibitor of G1 cyclin-dependent kinases. Cell 75: 805– p53 and GADD45 is defective in ataxia-telangiectasia. Cell 816. 71: 587–597. Harvey, D.M. and A.J. Levine. 1991. p53 alteration is a common Ko, L.J. and C. Prives. 1996. p53: Puzzle and paradigm. Genes & event in the spontaneous immortalization of primary Dev. 10: 1054–1072. BALB/c murine embryo fibroblasts. Genes & Dev. 5: 2375– Kubbutat, M.H., S.N. Jones, and K.H. Vousden. 1997. Regula- 2385. tion of p53 stability by Mdm2. Nature 387: 299–303. Harvey, M., A.T. Sands, R.S. Weiss, M.E. Hegi, R.W. Wiseman, Kuerbitz, S.J., B.S. Plunkett, W.V. Walsh, and M.B. Kastan. 1992. GENES & DEVELOPMENT 2989 Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press Sherr Wild-type p53 is a cell cycle checkpoint determinant follow- EMBO J. 17: 554–564. INK4a ing irradiation. Proc. Natl. Acad. Sci. 89: 7491–7495. Ruas, M. and G. Peters. 1998. The p16 /CDKN2A tumor Land, H., L.F. Parada, and R.A. Weinberg. 1983. Tumorigenic suppressor and its relatives. Biochim. Biophys. Acta Rev. conversion of primary embryo fibroblasts requires at least Cancer (in press). two cooperating oncogenes. Nature 304: 596–602. Ruley, H.E. 1983. Adenovirus early region 1A enables viral and Lanni, J.S. and T. Jacks. 1998. Characterization of the p53-de- cellular transforming genes to transform primary cells in pendent postmitotic checkpoint following spindle disrup- culture. Nature 304: 602–606. tion. Mol. Cell. Biol. 18: 1055–1064. Serrano, M., G.J. Hannon, and D. Beach. 1993. A new regulatory Lee, H.-W., M.A. Blasco, G.J. Gottlieb, J.W. Horber, C.W. Gre- motif in cell cycle control causing specific inhibition of cy- ider, and R.A. DePinho. 1998. Essential role of mouse telom- clin D/CDK4. Nature 366: 704–707. erase in highly proliferative organs. Nature 392: 569–574. Serrano, M., H.-W. Lee, L. Chin, C. Cordon-Cardo, D. Beach, Levine, A.J. 1997. p53, the cellular gatekeeper for growth and and R.A. DePinho. 1996. Role of the INK4a locus in tumor division. Cell 88: 323–331. suppression and cell mortality. Cell 85: 27–37. Livingstone, L.R., A. White, J. Sprouse, E. Livanos, T. Jacks, and Serrano, M., A.W. Lin, M.E. McCurrach, D. Beach, and S.W. T.D. Tlsty. 1992. Altered cell cycle arrest and gene amplifi- Lowe. 1997. Oncogenic ras provokes premature cell senes- INK4a cation potential accompany loss of wild-type p53. Cell cence associated with accumulation of p53 and p16 . 70: 923–935. Cell 88: 593–602. Lloyd, A.C., F. Obermuller, S. Staddon, C.F. Barth, M. McMa- Shan, B. and W.-H. Lee. 1994. Deregulated expression of E2F-1 hon, and H. Land. 1997. Cooperating oncogenes converge to induces S-phase entry and leads to apoptosis. Mol. Cell. Biol. regulate cyclin/cdk complexes. Genes & Dev. 11: 663–667. 14: 8166–8173. Lowe, S.W. and H.E. Ruley. 1993. Stabilization of the p53 tumor Sherr, C.J. 1996. Cancer cell cycles. Science 274: 1672–1677. suppressor is induced by adenovirus-5 E1A and accompanies Slebos, R.J.C., M.H. Lee, B.S. Plunkett, T.D. Kessis, B.O. Willi- apoptosis. Genes & Dev. 7: 535–545. ams, T. Jacks, L. Hedrick, M.B. Kastan, and K.R. Cho. 1994. Lowe, S.W., H.E. Ruley, T. Jacks, and D.E. Housman. 1993. p53-dependent G1 arrest involves pRB-related proteins and p53-dependent apoptosis modulates the cytotoxicity of anti- is disrupted by the human papillomavirus 16 E7 oncopro- cancer agents. Cell 74: 957–966. tein. Proc. Natl. Acad. Sci. 91: 5320–5324. Mao, L., A. Merlo, G. Bedi, G.I. Shapiro, C.D. Edwards, B.J. Stone, S., P. Jiang, P. Dayananth, S.V. Tavtigian, H. Katcher, D. INK4a Rollins, and D. Sidransky. 1995. A novel p16 transcript. Parry, G. Peters, and A. Kamb. 1995. Complex structure and Cancer Res. 55: 2995–2997. regulation of the p16(MTS1) locus. Cancer Res. 55: 2988– Metz, T., A.W. Harris, and J.M. Adams. 1995. Absence of p53 2994. allows direct immortalization of hematopoietic cells by the Stott, F., S.A. Bates, M. James, B.B. McConnell, M. Starborg, S. myc and raf oncogenes. Cell 82: 29–36. Brookes, I. Palmero, E. Hara, K.H. Vousden, and G. Peters. Morgenbesser, S.D., B.O. Williams, T. Jacks, and R.A. DePinho. 1998. The alternative product from the human CDKN2A ARF 1994. p53-dependent apoptosis produced by Rb-deficiency in locus, p14 , participates in a regulatory feedback loop with the developing mouse lens. Nature 371: 72–74. p53 and MDM2. EMBO J. (in press). Pan, H. and A.E. Griep. 1994. Altered cell cycle regulation in the Swafford, D.S., S.K. Middleton, W.A. Palmisano, K.J. Nikula, J. lens of HPV-16 E6 or E7 transgenic mice: Implications for Tesfaigzi, S.B. Baylin, J.G. Herman, and S.A. Belinsky. 1997. INK4a tumor suppressor gene function in development. Genes & Frequent aberrant methylation of p16 in primary rat Dev. 8: 1285–1299. lung tumors. Mol. Cell. Biol. 17: 1366–1374. Paulovich, A.G., D.P. Toczyski, and L.H. Hartwell. 1997. When Symonds, H., L. Krall, L. Remington, M. Saenz-Robles, S. Lowe, checkpoints fail. Cell 88: 315–321. T. Jacks, and T. Van Dyke. 1994. p53-dependent apoptosis Pomerantz, J., N. Schreiber-Agus, N.J. Lie ´ geois, A. Silverman, L. suppresses tumor growth and progression in vivo. Cell Alland, L. Chin, J. Potes, K. Chen, I. Orlow, H.-W. Lee, C. 78: 703–711. Cordon-Cardo, and R. DePinho. 1998. The Ink4a tumor sup- Thomas, A. and E. White. 1998. Suppression of the p300-depen- ARF pressor gene product, p19 , interacts with MDM2 and dent mdm2 negative-feedback loop induces the p53 apop- neutralizes MDM2’s inhibition of p53. Cell 92: 713–723. totic function. Genes & Dev. 12: 1975–1985. Qin, X.Q., D.M. Livingston, W.G. Kaelin, Jr., and P.D. Adams. Van Dyke, T. 1994. Analysis of viral-host protein interactions 1994. Deregulated transcription factor E2F-1 expression and tumorigenesis in transgenic mice. Semin. Cancer Biol. leads to S-phase entry and p53-mediated apoptosis. Proc. 5: 47–60. Natl. Acad. Sci. 91: 10918–19022. Wagner, A.J., J.M. Kokontis, and N. Hay. 1994. Myc-mediated Quelle, D.E., F. Zindy, R.A. Ashmun, and C.J. Sherr. 1995. Al- apoptosis requires wild-type p53 in a manner independent of ternative reading frames of the INK4a tumor suppressor gene cell cycle arrest and the ability of p53 to induce p21 waf1/ encode two unrelated proteins capable of inducing cell cycle cip1. Genes & Dev. 8: 2817–2830. arrest. Cell 83: 993–1000. Weinberg, R.A. 1995. The retinoblastoma protein and cell cycle Quelle, D.E., M. Cheng, R.A. Ashmun, and C.J. Sherr. 1997. control. Cell 81: 323–330. Cancer-associated mutations at the INK4a locus cancel cell ———. 1997. The cat and mouse games that genes, viruses, and INK4a cycle arrest by p16 but not by the alternative reading cells play. Cell 88: 573–575. ARF frame protein p19 . Proc. Natl. Acad. Sci. 94: 3436–3440. White, E. 1996. Life, death, and the pursuit of apoptosis. Genes Rao, L., M. Debbas, P. Sabbatini, D. Hockenberry, S. Korsmeyer, & Dev. 10: 1–15. and E. White. 1992. The adenovirus E1A proteins induce White, E., R. Cipriani, P. Sabbatini, and A. Denton. 1991. The apoptosis which is inhibited by E1B 19K and Bcl-2 proteins. adenovirus E1B 19-kilodalton protein overcomes the cyto- Proc. Natl. Acad. Sci. 89: 7742–7746. toxicity of E1A proteins. J. Virol. 65: 2968–2978. Roth, J., M. Dobbelstein, D. Freedman, T. Shenk, and A.J. Wu, X. and A.J. Levine. 1994. p53 and E2F-1 cooperate to me- Levine. 1998. Nucleo-cytoplasmic shuttling of the hdm2 on- diate apoptosis. Proc. Natl. Acad. Sci. 91: 3602–3606. coprotein regulates the levels of the p53 protein via a path- Wu, X., J.H. Bayle, D. Olson, and A.J. Levine. 1993. The p53– way used by the human immunodeficiency virus rev protein. mdm–2 autoregulatory feedback loop. Genes & Dev. 7: 2990 GENES & DEVELOPMENT Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press ARF tumor suppression 1126–1132. Xiong, Y., G.J. Hannon, H. Zhang, D. Casso, R. Kobayashi, and D. Beach. 1993. p21 is a universal inhibitor of cyclin kinases. Nature 366: 701–704. Yin, Y., M.A. Tainsky, F.Z. Bischoff, L.C. Strong, and G.M. Wahl. 1992. Wild-type p53 restores cell cycle control and inhibits gene amplification in cells with mutant p53 alleles. Cell 70: 937–948. Zhang, Y., Y. Xiong, and W.G. Yarbrough. 1998. ARF promotes MDM2 degradation and stabilizes p53: ARF-INK4a locus de- letion impairs both the Rb and p53 tumor suppressor path- ways. Cell 92: 725–734. Zindy, F., C.M. Eischen, D. Randle, T. Kamijo, J.L. Cleveland, C.J. Sherr, and M.F. Roussel. 1998. Myc signaling via the ARF tumor suppressor regulates p53-dependent apoptosis and immortalization. Genes & Dev. 12: 2424–2434. GENES & DEVELOPMENT 2991 Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press Charles J. Sherr Genes Dev. 1998, 12: Access the most recent version at doi:10.1101/gad.12.19.2984 This article cites 76 articles, 35 of which can be accessed free at: References http://genesdev.cshlp.org/content/12/19/2984.full.html#ref-list-1 License Receive free email alerts when new articles cite this article - sign up in the box at the top Email Alerting right corner of the article or click here. Service Cold Spring Harbor Laboratory Press http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Genes & Development Unpaywall

Tumor surveillance via the ARF-p53 pathway

Sherr, C. J.
Genes & Development – Oct 1, 1998
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Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press PERSPECTIVE Tumor surveillance via the ARF–p53 pathway Charles J. Sherr Howard Hughes Medical Institute, Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105 USA INK4a The retinoblastoma (Rb) and p53 genes are not essential function of one of the two negative regulators (p16 for completion of the cell division cycle, but disruption or Rb) or from events leading to overexpression of one of of their functions is central to the life history of most, if the two proto-oncogenes (cyclin D1 or cdk4) (for review, not all, cancer cells (for review, see Weinberg 1995; Sherr see Weinberg 1995; Sherr 1996; Ruas and Peters 1998). 1996; Levine 1997). Surprisingly, Rb and p53 are them- The p53 protein is a transcription factor that can in- selves regulated by two proteins encoded by a single hibit cell cycle progression or induce apoptosis in re- genetic locus, INK4a/ARF, the products of which, sponse to stress or DNA damage, and inactivation of p53 INK4a ARF p16 and p19 , are also potent tumor suppressors. attenuates both of these cellular responses (for review, INK4a The role of p16 as an inhibitor of cyclin D-depen- see Ko and Prives 1996; Levine 1997; Giaccia and Kastan dent kinases has been appreciated since its discovery 1998). Elimination of functional p53 through various (Serrano et al. 1993). Now, emerging evidence is provid- mechanisms is the single most common event in human ing valuable insights into the molecular circuitry cancer, occurring in over half of all tumors (Hollstein et ARF through which p19 modulates p53 activity as part of al. 1994). The p53 protein is short-lived and expressed at a checkpoint response to oncogenic, hyperproliferative very low levels in normal cells but it is stabilized and signals. accumulates in cells that have sustained genotoxic dam- age (Fig. 1). Among the gene products induced by p53 is Cip1/Waf1 the cdk inhibitor p21 , which can effect cell Regulation of cell cycle progression by pRb and p53 cycle arrest (El-Deiry et al. 1993; Harper et al. 1993; Xiong et al. 1993). Another key target is Mdm2, which During most of G phase of the mammalian cell cycle, acts in a feedback loop to limit the action of p53 (Barak Rb in its hypophosphorylated form binds to several tran- et al. 1993; Wu et al. 1993), both by inhibiting its trans- scription factors of the E2F family, constraining their activating activity and by catalyzing its destruction activity on some promoters and actively repressing tran- (Haupt et al. 1997; Honda et al. 1997; Kubbutat et al. scription from others (see Dyson 1998). Phosphorylation 1997). Mutation of p53 compromises cell cycle arrest, of Rb by cyclin-dependent kinases (cdks) in the mid-to- attenuates apoptosis induced by DNA damage, predis- late G phase of the cycle untethers Rb from the E2Fs. In poses cells to drug-induced gene amplification, affects turn, this enables the E2Fs to activate a series of target centrosome duplication, and rapidly leads to changes in genes, the expression of which is required for cells to chromosome number and ploidy (Kastan et al. 1991, enter S phase, thereby stimulating proliferation (Fig. 1). 1992; Kuerbitz et al. 1992; Livingstone et al. 1992; Yin et The cyclin D-dependent kinases cdk4 and cdk6 trigger al. 1992; Clarke et al. 1993; Lowe and Ruley 1993; Lowe Rb phosphorylation, which is likely completed by cyclin et al. 1993; Fukusawa et al. 1996; Jacks and Weinberg E–cdk2 as cells approach the G -to-S phase transition. 1996; Hermeking et al. 1997; Paulovich et al. 1997; Gu- Because induction and assembly of cyclin D-dependent alberto et al. 1998; Lanni and Jacks 1998). The resulting kinases is dependent on mitogenic signaling, cancella- genomic instability greatly increases the probability that tion of Rb’s growth-suppressive activity is coupled to p53-null cells will evolve toward malignancy. extracellular stimuli. By inhibiting cdk4 and cdk6, a Cooperation between the Rb and p53 pathways has family of INK4 proteins can prevent cells with func- been amply demonstrated. Classic examples involve on- tional Rb from entering S phase. The prototypic member, coproteins encoded by the DNA tumor viruses, which INK4a p16 (Serrano et al. 1993), is distinguished from its both cancel Rb function to drive cells into S phase and INK4b INK4c INK4d close relatives (p15 , p18 , and p19 )inits neutralize p53 to prevent host cell suicide (for review, role as a potent tumor suppressor. Disruption of the see White 1996). Loss of function by Rb and related fam- INK4a p16 –cyclin D1/cdk4–Rb pathway is a common ily members can bypass p53-mediated G arrest (Demers event in human cancer, either resulting from loss of et al. 1994; Slebos et al. 1994), but Rb loss induces E2F and p53-dependent apoptosis (Lowe and Ruley 1993; E-MAIL [email protected]; FAX (901) 495-2381. Howes et al. 1994; Morgenbesser et al. 1994; Pan and 2984 GENES & DEVELOPMENT 12:2984–2991 © 1998 by Cold Spring Harbor Laboratory Press ISSN 0890-9369/98 $5.00; www.genesdev.org Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press ARF tumor suppression Figure 1. ARF checkpoint control. ARF re- sponds to proliferative signals that are nor- mally required for cell proliferation. When these signals exceed a critical threshold, the ARF-dependent checkpoint (gray vertical bar- rel) is activated, and ARF triggers a p53-depen- dent response that induces growth arrest and/ or apoptosis. Signals now known to induce sig- naling via the ARF–p53 pathway include Myc, E1A, and E2F-1. In principle, ‘upstream’ onco- proteins, such as products of mutated Ras alle- les, constitutively activated receptors, or cyto- plasmic signal transducing oncoproteins, might also trigger ARF activity via the cyclin D– cdk4–Rb–E2F or Myc-dependent pathways, both of which are normally necessary for S- phase entry. In inhibiting cyclin D-dependent INK4a kinases, p16 can dampen the activity of mitogenic signals. E1A is shown to work, at least in part, by canceling Rb function, although its ability to inhibit p300 contributes to the response by interfering with mdm2 expression. Again for simplicity, Myc and E2F-1 are only shown to activate p53 via ARF. However, highly overexpressed levels of these proteins can activate p53 in ARF-negative cells, albeit with an attenuated efficiency. ARF activation of p53 likely depends on inactivation of some Mdm2-specific function (implied by the unfilled box bracketing the latter two proteins). DNA damage signals (ionizing and UV radiation, hypoxic stress, genotoxic drugs, etc.) access p53 through multiple signaling pathways shown, again for simplicity, as a single DNA damage checkpoint (gray horizontal barrel). Signals through the ARF and DNA damage pathways can synergize in activating p53. Griep 1994; Qin et al. 1994; Shan et al. 1994; Symonds et frame (ARF) of exon 2 (Quelle et al. 1995). The human al. 1994; Wu and Levine 1994). In short, mutational protein terminates farther upstream in exon 2 and it has INK4a ARF events that disable the p16 –cyclin D1/cdk4–Rb a predicted molecular mass of only 14 kD. Mouse p19 ARF pathway and enforce cell proliferation are counterbal- and human p14 are highly basic nuclear proteins that anced by a p53-dependent apoptotic response that can induce G - and G -phase arrest when introduced into a 1 2 eliminate incipient cancer cells. The ability of E2F to variety of different cell types (Quelle et al. 1995; Stott et trigger p53-dependent cell suicide implies that a bio- al. 1998). INK4a/ARF-null cells are susceptible to ARF- ARF chemical connection links their functions. Other cellu- induced arrest, so this activity of p19 does not depend INK4a lar oncogenes, such as myc, also induce p53-dependent upon p16 . apoptosis (Hermeking and Eick 1994; Wagner et al. Mutations that inactivate the cdk inhibitory function INK4a 1994). Hence, p53 is not only activated by DNA damage, of p16 occur frequently in a wide spectrum of hu- but it provides an ‘oncogene checkpoint’ function that man cancers (for review, see Ruas and Peters 1998). For guards cells against hyperproliferative signals (for re- example, certain inactivating point mutations impinge view, see Van Dyke 1994; Jacks and Weinberg 1996; on exon 1a, some of which are inherited in melanoma White 1996; Levine 1997). This is the setting in which kindreds (Kamb et al. 1994a,b; Gruis et al. 1995). Al- ARF p19 plays a key role. though many point mutations in exon 2 of INK4a are ARF also predicted to alter p19 , those that have been tested experimentally have been found to inactivate The INK4a/ARF locus and tumor suppression INK4a ARF p16 without affecting the ability of p19 to in- The manner by which a single genetic locus encodes duce cell cycle arrest. Moreover, the amino-terminal INK4a ARF both p16 and p19 is unprecedented in mammals moiety of ARF (amino acids 1–64), encoded entirely by INK4a (Quelle et al. 1995) (Fig. 2). p16 is encoded by three exon 1b, is sufficient to induce cell cycle arrest when overexpressed (Quelle et al. 1997; Zhang et al. 1998), closely linked exons (designated 1a, 2, and 3). An RNA segment arising from an alternative first exon (1b), although tumor-specific point mutations in this domain which maps 13–20 kb upstream in the human, mouse, have not been described (Stone et al. 1995; Ruas and INK4a and rat genomes, is spliced to exon 2, yielding a b tran- Peters 1998). Together, these data suggest that p16 script that is almost identical in size to the a transcript is disrupted frequently by point mutations in human INK4a ARF that encodes p16 (Duro et al. 1995; Mao et al. 1995; cancer, but p19 is not. However, the common occur- Quelle et al. 1995; Stone et al. 1995; Swafford et al. 1997). rence of homozygous deletions of INK4a/ARF in a wide The initiator codon in exon 1b is not in frame with se- range of human tumors leaves open the possibility that INK4a quences encoding p16 in exon 2, so the b transcript ARF plays an independent role as a tumor suppressor (see specifies a novel polypeptide. In the mouse, this 19-kD below). protein consists of 65 amino acids encoded by exon 1b, Functional ablation of INK4a/ARF in mice by elimi- and 105 amino acids arising from the alternative reading nation of exons 2 and 3 (Fig. 2) revealed that derived GENES & DEVELOPMENT 2985 Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press Sherr phenotype was indistinguishable from that attributed INK4a previously to p16 disruption (Kamijo et al. 1997). INK4a Importantly, functional p16 was expressed in nor- mal tissues of ARF-null mice, in cultured MEFs, and in cells from spontaneously arising tumors. Therefore, ARF functions as a bona fide tumor suppressor, and the phe- notype initially ascribed to INK4a loss is instead likely due to ARF inactivation. In turn, the phenotypic conse- Figure 2. The INK4a/ARF locus. Genomic sequences encod- INK4a INK4a quences of p16 loss in mice remain uncertain, and ing p16 are defined by completely filled regions within the construction of a pure INK4a knockout strain is war- boxes designating exons 1a, 2, and 3, whereas the segments of exons 1b and 2 that encode ARF are defined by shaded areas. ranted. Unfilled portions of the exons correspond to noncoding 58 and 38 regions. Splicing between the exons is indicated by the connect- The ARF–p53 pathway ing lines, and exons 1a and 1b are indicated to have separate promoters (→). In the mouse genome, the alternative first exons A cardinal feature of ARF-null MEFs is their capacity to are separated by ~13 kb of intervening sequences. Segments of grow as established cell lines and to be transformed by the genes that were disrupted by Serrano et al. (1996) and Ka- oncogenic ras genes alone (Kamijo et al. 1997). Approxi- mijo et al. (1997) are designated by horizontal lines below the mately 20% of spontaneously established fibroblast cell schematic. lines derived from MEFs of wild-type mice undergo bi- allelic ARF loss. MEF strains that are hemizygous for ARF lose their remaining functional ARF allele and nullizygous animals were highly prone to tumor devel- spontaneously immortalize at a faster rate than wild- opment (Serrano et al. 1996). Tumors arose early in life, type strains. In each case, established MEF cell lines that and their appearance was accelerated by irradiation of lacked ARF preserved p53 function, whereas those that newborn mice or by their treatment with chemical car- retained ARF had sustained p53 mutations. These re- ARF cinogens. Intriguingly, mouse embryo fibroblasts (MEFs) sults suggested that p19 and p53 might function in explanted from the INK4a/ARF knock-out mice did not the same biochemical pathway. Consistent with this hy- undergo replicative senescence in culture. Like many es- pothesis, cells lacking a functional p53 gene are resistant ARF tablished mouse cell lines, but unlike normal primary to p19 -induced cell cycle arrest, implying that p53 MEFs, they could be transformed by oncogenic ras alle- acts downstream of ARF (Kamijo et al. 1997). However, les without a requirement for so-called immortalizing ARF-null cells exhibit an intact p53 checkpoint follow- ARF oncogenes such as myc or adenovirus E1A. MEFs from ing ionizing or UV irradiation, so p19 does not relay p53-null mice exhibit similar properties (Harvey et al. signals to p53 in response to DNA damage (Fig. 1). Loss 1993), and p53-inactivating mutations are the most com- of p53 can occur in cancer cells that arise in ARF-null mon single events in the spontaneous conversion of MEF mice, again indicating that ARF plays a more specialized strains into continuously growing cell lines (Harvey and role in tumor suppression than p53, and that selection Levine 1991). Results with both INK4a/ARF-null or p53- against p53 can further contribute to malignancy (Ka- null MEFs directly contrast with those obtained with mijo et al. 1997). normal primary MEF strains, in which introduction of Evidence supporting direct biochemical interactions ARF oncogenic ras instead provokes a state of growth arrest between p19 and p53 is now in hand. Ectopic ARF resembling senescence, associated with accumulation of expression stabilizes p53 and induces p53-responsive INK4a both p53 and p16 (Serrano et al. 1997). Initially, it genes, Mdm2 among them. ARF can physically interact was reasoned that the phenotype observed in INK4a/ with Mdm2, and its binding blocks both Mdm2-induced INK4a ARF-null mice depended on the loss of p16 function p53 degradation and transactivational silencing (Kamijo INK4a (Serrano et al. 1996). It followed that both p16 and et al. 1998; Pomerantz et al. 1998; Stott et al. 1998; p53 acted as determinants of cell senescence in MEFs, Zhang et al. 1998). The interaction between Mdm2 and ARF with the loss of either leading to establishment and im- p19 depends on the carboxy-terminal half of Mdm2 mortalization. Release of the senescence block by dis- and on the ARF amino-terminus (i.e., the active exon INK4a ruption of p16 or p53 would be necessary for trans- 1b-coded segment) (Zhang et al. 1998). Because Mdm2 formation of mouse fibroblasts by oncogenic ras (Serrano binds to p53 through its amino-terminal domain, ARF et al. 1997; for review, see Weinberg 1997). A persistent can enter into ternary complexes with both Mdm2 and ambiguity is whether these mice lack ARF function p53. ARF completely. This is likely, because the targeting cassette Although human p14 appears not to interact with disrupted the mRNA polyadenylation signals as well as p53 directly (Pomerantz et al. 1998; Stott et al. 1998; the INK4a and ARF carboxy-terminal coding equences Zhang et al. 1998), there is some evidence that the (Fig. 2). However, the issue formally remains unresolved, mouse ARF protein can bind to p53 even in the absence because it is conceivable that a truncated ARF protein of Mdm2 (Kamijo et al. 1998). For example, in electro- might somehow arise from undisrupted exon 1b. phoretic mobility shift assays performed with purified, Surprisingly, when pure ARF-null mice were created activated p53 and a labeled oligonucleotide containing that lacked only the exon 1b sequences (Fig. 2), their tandem p53 consensus DNA-binding sites from the 2986 GENES & DEVELOPMENT Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press ARF tumor suppression Cip1 ARF p21 promoter, addition of recombinant p19 re- p53 complexes in the nucleolus, preventing their degra- tarded the mobility of the p53–oligonucleotide com- dation in the cytoplasm. plexes. In these assays, the otherwise latent DNA-bind- Finally, in cells lacking p53, ARF levels are signifi- ing capability of p53 needed to be activated by antibodies cantly elevated (Quelle et al. 1995; Stott et al. 1998), but ARF directed to a carboxy-terminal p53 epitope, and p19 reintroduction of wild-type p53 into p53-null MEFs can ARF was unable to substitute for the antibody in activating restore p19 to normal levels (Kamijo et al. 1998). DNA binding. These observations raise the possibility Similarly, in human Saos-2 osteosarcoma cells lacking ARF ARF that interactions between p19 endogenous p53 function, expression of p14 and p53 can occur on was chromatin, although there is no direct evidence that ARF down-regulated when cells were induced to express ei- plays any physiologic role as a p53 coactivator. ther tetracycline-regulated or temperature-sensitive p53 ARF requires p53 to induce growth arrest, but the di- (Stott et al. 1998). Therefore, not only can ARF stabilize ARF rect physical interactions among p19 , p53, and p53, but ARF expression is in turn controlled by p53 Mdm2 in various binary and ternary complexes suggest through negative feedback. Again, the underlying that some p53 functions may reciprocally depend on mechanism needs to be clarified. Among the possibili- ARF ARF. Overexpression of p19 in ARF-null NIH-3T3 ties is that the ARF gene might be repressed by p53, or Cip1 cells induced expression of a p21 promoter-driven re- the ARF protein could itself be a target of Mdm2-induced porter gene in a manner that depended on endogenous turnover. p53. Paradoxically, ectopic overexpression of wild-type p53 itself in ARF-null cells did not activate the reporter, indicating that simple increases in the amount of p53 Oncogenic signals induce ARF were insufficient to activate transcription in this setting. p53-Dependent reporter gene expression was restored The fact that ARF-null MEFs grow as established cell when subliminal amounts of ARF expression vector lines and can be transformed by oncogenic ras mimics were reintroduced together with increasing concentra- effects induced by so-called immortalizing oncogenes, ARF tions of p53,sop19 can provide some type of activat- like myc and E1A (Land et al. 1983; Ruley 1983). It there- ing signal that facilitates p53-dependent transcription fore seems paradoxical that myc and E1A are also potent (Kamijo et al. 1998). In this respect, the functions of p53 inducers of apoptosis (Askew et al. 1991; White et al. ARF and p19 are interdependent. 1991; Evan et al. 1992; Rao et al. 1992), a process aggra- Zhang and colleagues (1998) reported that ARF accel- vated by depriving MEFs of serum survival factors (Evan erated Mdm2 turnover in HeLa cells cotransfected with et al. 1992; Lowe et al. 1993). These contrasting out- vectors encoding ARF and Mdm2. They proposed that comes of Myc and E1A action—extended life versus ac- destabilization of Mdm2 by ARF was the mechanism celerated death—can be reconciled by observations that underlying p53 accumulation. However, experiments by their overexpression provides a strong selective pressure others have yielded conflicting results. The idea that for events that dismantle apoptotic signaling pathways, ARF destabilizes Mdm2 seems to be at odds with obser- with ARF being a key target. vations that ARF activation in MEFs induces endog- Overexpression of Myc, E1A, or E2F-1 in primary enous Mdm2 to accumulate in a p53-dependent manner MEFs rapidly induces ARF gene expression and leads to (de Stanchina et al. 1998; Kamijo et al. 1998; Zindy et al. p53-dependent apoptosis. However, ARF-null and p53- 1998). Stott and coworkers (1998) confirmed that in a null MEFs resist these effects (de Stanchina et al. 1998; variety of cell types cotransfected with Mdm2 and p53, Zindy et al. 1998). Similarly, wild-type or ARF hemizy- introduction of ARF overcame the ability of Mdm2 to gous MEFs that survive Myc overexpression generally induce p53 degradation. However, in the presence or ab- sustain either p53 mutation or ARF loss, but not both, sence of exogenous p53, ARF caused Mdm2 to accumu- rapidly yielding established cell lines that tolerate supra- late. Moreover, coexpression of the E6 protein of human physiologic Myc levels even in the absence of survival papilloma virus 16, which independently targets p53 for factors (Zindy et al. 1998). Myc and E1A can induce p53 degradation, did not interfere with the ability of ARF to through both ARF-dependent and ARF-independent pathways, but much higher levels of oncoprotein expres- stabilize cotransfected Mdm2. Minimally, it seems rea- sonable to conclude that ARF can antagonize Mdm2 sion are required to activate p53 when ARF is absent. function through a mechanism that does not depend on Under the latter conditions, the p53 response is attenu- increased Mdm2 turnover. ated and cells resistant to oncogene-induced killing rap- ARF How, then, does ARF stabilize p53? One possibility is idly emerge. Reintroduction of p19 into surviving that ARF interferes with Mdm2’s ability to trigger p53 ARF-null cells expressing either Myc or E1A resensitizes polyubiquitination. Supporting this idea, Mdm2 seems them to apoptosis, indicating that the attenuation of to induce the appearance of polyubiquitinated forms of death is a direct consequence of ARF loss and does not p53, which are much less abundant in cells that overex- result from other cryptic mutations. Therefore, Myc, ARF ARF press p19 (Pomerantz et al. 1998). Mdm2 and p19 E1A, and E2F-1 trigger a p53-dependent oncogene check- also colocalize in the nucleoli of cells transfected with point gated by ARF (Fig. 1). Although the ARF–p53 path- both genes (Pomerantz et al. 1998). Because p53 degra- way is not essential for normal proliferation, the check- dation depends upon its Mdm2-mediated nuclear export point could provide a fail-safe function during embryonic (Roth et al. 1998), ARF could conceivably retain Mdm2– development. For example, in a model of the developing GENES & DEVELOPMENT 2987 Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press Sherr murine lens, Rb deficiency triggers apoptosis in a p53- ARF in human cancer dependent manner (Morgenbesser et al. 1994), but the Much of the experimental work on ARF to date has in- process is attenuated in lenses from animals lacking volved murine systems. Senescence (and conversely, im- INK4a/ARF (Pomerantz et al. 1998). mortalization) of human cells is likely to be subject to One component of the E1A response involves its abil- additional and more stringent controls, particularly in ity to activate p300, a coactivator required for p53-de- light of our longer life span. Whereas p53 and Rb inacti- pendent mdm2 transcription (Thomas and White 1998). vation can endow human fibroblasts with increased pro- But the ability of E1A to induce ARF in MEFs is likely liferative potential, cells lacking these functions are not mediated by the E2Fs, as E1A mutants that bind p300 immortal, and chromosomal telomere shortening soon but do not interact with Rb are highly defective in this limits continued cell proliferation (Bodnar et al. 1998). In regard (de Stanchina et al. 1998) (Fig. 1). Conditional ex- contrast, mouse chromosomes have much longer telo- pression of E2F-1 in Saos-2 cells was followed temporally meres, and mice lacking telomerase activity must be by increased ARF mRNA and protein expression (Bates bred through many generations before the deleterious et al. 1998). Cotransfection experiments indicated that effects of telomere shortening are manifest (Blasco et al. wild-type E2F-1 activated transcription from a minimal 1997; Lee et al. 1998). ARF promoter, whereas an E2F-1 mutant defective in Despite fundamental differences of this type, ARF is transactivation was devoid of activity. Despite the fact likely to function as a tumor suppressor in humans. Cer- ARF that Myc also induces p19 to accumulate very rapidly tain cancers such as melanomas, biliary tumors, non- (Zindy et al. 1998), it is presently unclear whether Myc small cell lung carcinomas, pancreatic, and esophageal activates the ARF promoter directly. carcinomas frequently sustain INK4a point mutations. Cooperation between myc and oncogenic ras (Land et Other tumor types, however, such as T- and B-cell acute al. 1983; Ruley 1983) can be viewed to involve the ARF– lymphoblastic leukemias, bladder and nasopharyngeal p53 pathway indirectly. Cultured MEFs achieve replica- carcinomas, mesotheliomas, anaplastic astrocytomas, tive immortality by inactivating ARF or p53, and by pro- and glioblastoma multiforme routinely exhibit INK4a/ moting cell death, oncogenes such as E1A and myc pro- ARF deletions rather than point mutations (Ruas and vide a strong selective pressure for disabling ARF or p53 Peters 1998). Whether or not these homozygous dele- ARF function. Because enforced expression of p19 arrests tions target both ARF and INK4a or ARF alone, their wild-type MEFs but does not kill them (Quelle et al. high frequency of occurrence strongly argues that ARF 1995), other functions of Myc and E1A in addition to loss contributes significantly to human cancer. This ARF induction are required for this process. The growth makes good sense. If p53 is directly targeted in >50% of promoting properties of Myc and E1A are important be- human malignancies, then p53-positive tumors have cause without them, the selection for immortal cells likely sustained epistatic mutations such as Mdm2 am- would likely not occur. This is even more obvious in plification or ARF loss. The concept that ARF monitors other cell types in which transformation and tumorigen- proliferative signals rather than DNA damage helps to esis strongly depend upon Myc’s growth promoting func- expand our understanding of p53 action and provides a tions even in the absence of p53 (see, for example, Metz further rationale for ARF inactivation through chromo- et al. 1995). In turn, Myc and E1A seem to inactivate somal deletion in many forms of cancer. cellular responses that are normally required for Ras- mediated inhibition of cell proliferation, thereby con- verting ras into a growth-promoting gene (Franza et al. 1986; Hicks et al. 1991; Hirakawa et al. 1991; Lloyd et al. Acknowledgments 1997; Serrano et al. 1997). The fact that oncogenic ras I thank Martine F. Roussel, John Cleveland, Gerry Zambetti, alone can transform MEFs lacking ARF or p53 argues Tom Curran, A. Thomas Look, Suzy Baker, Peter McKinnon, that their inactivation is key. ARF Scott W. Lowe, Ron DePinho, Tyler Jacks, Manuel Serrano, and Because p19 addresses p53 through a pathway that Terry Van Dyke for stimulating and helpful discussions, and is distinct from those activated by DNA damage (Fig. 1), Dawn Quelle, Frederique Zindy, Takehiko Kamijo, Jason We- induction of ARF by oncogenes may sensitize cells to the ber, and Mangeng Cheng for contributing critical data pertinent effects of genotoxic drugs that are used to treat cancer. to the work from the Sherr and Roussel laboratories. C.J.S. is an Indeed, MEFs expressing E1A are significantly more sen- investigator of the Howard Hughes Medical Institute and also sitive to killing by adriamycin than their normal coun- acknowledges support from the American Lebanese Syrian As- terparts, whereas E1A-expressing ARF-null MEFs no sociated Charities (ALSAC) of St. Jude Children’s Research Hos- longer manifest this synergy (de Stanchina et al. 1998). pital. The ability of ARF to sense hyperproliferative stimuli must be important in tumor surveillance, because ARF loss strongly predisposes to spontaneous cancer develop- References ment and accelerates the frequency of tumor induction by irradiation or carcinogens (Serrano et al. 1996; Kamijo Askew, D.S., R.A. Ashmun, B.C. Simmons, and J.L. Cleveland. et al. 1997). Indeed, in the absence of ARF emergence of 1991. Constitutive c-myc expression in an IL3-dependent p53-negative tumor cells that are resistant to DNA dam- myeloid cell line suppresses cell cycle arrest and accelerates aging agents should still occur (Fig. 1). apoptosis. Oncogene 6: 1915–1922. 2988 GENES & DEVELOPMENT Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press ARF tumor suppression Barak, Y., T. Juven, R. Haffner, and M. Oren. 1993. Mdm2 ex- P. Pantazis, B.C. Giovanella, M.A. Tainsky, A. Bradley, and pression is induced by wild type p53 activity. EMBO J. L.A. Donehower. 1993. In vitro growth characteristics of em- 12: 461–468. bryo fibroblasts isolated from p53-deficient mice. Oncogene Bates, S., A.C. Phillips, P. Clarke, F. Stott, G. Peters, R.L. Lud- 8: 2457–2467. ARF wig, and K.H. Vousden. 1998. E2F-1 regulation of p14 Haupt, Y., R. Maya, A. Kazaz, and M. Oren. 1997. Mdm2 pro- links pRB and p53. Nature (in press). motes the rapid degradation of p53. Nature 387: 296–299. Blasco, M.A., H.-W. Lee, M.P. Hande, E. Samper, P.M. Lansdorp, Hermeking, H. and D. Eick. 1994. Mediation of c-Myc-induced R.A. DePinho, and C.W. Greider. 1997. Telomere shortening apoptosis by p53. Science 265: 2091–2093. and tumor formation by mouse cells lacking telomerase Hermeking, H., C. Lengauer, K. Polyak, T.-C. He, L. Zhang, S. RNA. Cell 91: 25–34. Thiagalingam, K.W. Kinzler, and B. Vogelstein. 1997. 14-3- Bodnar, A.G., M. Ouellette, M. Frolkis, S.E. Holt, C.-P. Chiu, 3s is a p53-regulated inhibitor of G2/M progression. Mol. G.B. Morin, C.B. Harley, J.B. Shay, S. Lichsteiner, and W.E. Cell 1: 3–11. Wright. 1998. Extension of life-span by introduction of Hicks, G.C., S.E. Egan, A.H. Greenberg, and M. Mowat. 1991. telomerase into normal human cells. Science 279: 349–352. Mutant p53 tumor suppressor alleles release ras-induced cell Clarke, A.R., C.A. Purdie, D.J. Harrison, R.G. Morris, C.C. Bird, cycle growth arrest. Mol. Cell. Biol. 11: 1344–1352. M.L. Hooper, and A.H. Wyllie. 1993. Thymocyte apoptosis Hirakawa, T. and H.E. Ruley. 1991. Rescue of cells from ras induced by p53-dependent and independent pathways. Na- oncogene-induced growth arrest by a second complementing ture 362: 849–852. oncogene. Proc. Natl. Acad. Sci. 85: 1519–1523. de Stanchina, E., M.E. McCurrach, F. Zindy, S.-Y. Shieh, G. Hollstein, M., K. Rice, M.S. Greenblatt, T. Soussi, R. Fuchs, T. Ferbeyre, A.V. Samuelson, C. Prives, M.F. Roussel, C.J. Sorlie, E. Hovig, B. Smith-Sorensen, R. Montesano, and C.C. Sherr, and S.W. Lowe. 1998. E1A signaling to p53 involves Harris. 1994. Database of p53 gene somatic mutations in ARF the p19 tumor suppressor. Genes & Dev. 12: 2435–2443. human tumors and cell lines. Nucleic Acids Res. 22: 3551– Demers, G.W., S.A. Foster, C.L. Halbert, and D.A. Galloway. 3555. 1994. Growth arrest by induction of p53 in DNA damaged Honda, R., H. Tanaka, and H. Yasuda. 1997. Oncoprotein keratinocytes is bypassed by human papillomavirus 16 E7. MDM2 is a ubiquitin ligase E3 for tumor suppressor p53. Proc. Natl. Acad. Sci. 91: 4382–4386. FEBS Lett. 420: 25–27. Duro, D., O. Bernard, V. Della Valle, R. Berger, and C.-J. Larsen. Howes, K.A., N. Ransom, D.S. Papermaster, J.G.H. Lasudry, INK4/MTS1 1995. A new type of p16 gene transcript expressed D.M. Albert, and J.J. Windle. 1994. Apoptosis or retinoblas- in B-cell malignancies. Oncogene 11: 21–29. toma: Alternative fates of photoreceptors expressing the Dyson, N. 1998. The regulation of E2F by pRb-family members. HPV-16 E7 gene in the presence or absence of p53. Genes & Genes & Dev. 12: 2245–2262. Dev. 8: 1300–1310. El-Deiry, W.S., T. Tokino, V.E. Velculescu, D.B. Levy, R. Par- Jacks, T. and R.A. Weinberg. 1996. Cell-cycle control and its sons, J.M. Trent, D. Lin, E. Mercer, K.W. Kinzler, and B. watchman. Nature 381: 643–644. Vogelstein. 1993. WAF1, a potential mediator of p53 tumor Kamb, A., N.A. Gruis, J. Weaver-Feldhaus, Q. Liu, K. Harshman, suppression. Cell 75: 817–825. S.V. Tavtigian, E. Stockert, R.S. Day, III, B.E. Johnson, and Evan, G.I., A.H. Wyllie, C.S. Gilbert, T.D. Littlewood, H. Land, M.H. Skolnick. 1994a. A cell cycle regulator involved in gen- M. Brooks, C.M. Water, L.Z. Penn, and D.C. Hancock. 1992. esis of many tumor types. Science 264: 436–440. Induction of apoptosis in fibroblasts by c-myc protein. Cell Kamb, A., D. Shattuck-Eidens, R. Eeles, Q. Liu, N.A. Gruis, W. 69: 119–128. Ding, C. Hussey, T. Tran, Y. Miki, J. Weaver-Feldhaus, M. Franza, B.R., K. Maruyama, J.I. Garrels, and H.E. Ruley. 1986. In McClure, J.F. Aitken, D.E. Anderson, W. Bergman, R. Frants, vitro establishment is not sufficient prerequisite for trans- D.E. Goldgar, A. Green, R. MacLennan, N.G. Martin, L.J. formation by activated ras oncogene. Cell 44: 409–418. Meyer, P. Youl, J.J. Zone, M.H. Skolnick, and L.A. Cannon- Fukusawa, K., T. Choi, R. Kuriyama, S. Rulong, and G.F. Vande Albright. 1994b. Analysis of the p16 gene (CDKN2) as a can- Woude. 1996. Abnormal centrosome amplification in the ab- didate for the chromosome 9p melanoma susceptibility lo- sence of p53. Science 271: 1744–1747. cus. Nature Genet. 8: 22–26. Giaccia, A.J. and M.B. Kastan. 1998. The complexity of p53 Kamijo, T., F. Zindy, M.F. Roussel, D.E. Quelle, J.R. Downing, modulation: Emerging patterns from divergent signals. R.A. Ashmun, G. Grosveld, and C.J. Sherr. 1997. Tumor sup- Genes & Dev. 12: (this issue). pression at the mouse INK4a locus mediated by the alterna- ARF Gruis, N.A., P.A. van der Velden, L.A. Sandkuijl, D.E. Prins, J. tive reading frame product p19 . Cell 91: 649–659. Weaver-Feldhaus, A. Kamb, W. Bergman, and R. Frants. Kamijo, T., J.D. Weber, G. Zambetti, F. Zindy, M.F. Roussel, 1995. Homozygotes for CDKN2 (p16) germline mutation in and C.J. Sherr. 1998. Functional and physical interactions of Dutch familial melanoma kindreds. Nat. Genet. 10: 351– the ARF tumor suppressor with p53 and Mdm2. Proc. Natl. 353. Acad. Sci. 95: 8292–8297. Gualberto, A., K. Aldape, K. Kozakiewicz, and T.D. Tlsty. 1998. Kastan, M.B., O. Onyekwere, D. Sidransky, B. Vogelstein, and An oncogenic form of p53 confers a dominant, gain-of-func- R.W. Craig. 1991. Participation of p53 protein in the cellular tion phenotype that disrupts spindle checkpoint control. response to DNA damage. Cancer Res. 51: 6304–6311. Proc. Natl. Acad. Sci. 95: 5166–5171. Kastan, M.B., Q. Zhan, W.S. El-Deiry, F. Carrier, T. Jacks, W.V. Harper, J.W., G.R. Adami, N. Wei, K. Keyomarsi, and S.J. Walsh, B.S. Plunkett, B. Vogelstein, and A.J. Fornace, Jr. Elledge. 1993. The p21 cdk-interacting protein Cip1 is a po- 1992. A mammalian cell cycle checkpoint pathway utilizing tent inhibitor of G1 cyclin-dependent kinases. Cell 75: 805– p53 and GADD45 is defective in ataxia-telangiectasia. Cell 816. 71: 587–597. Harvey, D.M. and A.J. Levine. 1991. p53 alteration is a common Ko, L.J. and C. Prives. 1996. p53: Puzzle and paradigm. Genes & event in the spontaneous immortalization of primary Dev. 10: 1054–1072. BALB/c murine embryo fibroblasts. Genes & Dev. 5: 2375– Kubbutat, M.H., S.N. Jones, and K.H. Vousden. 1997. Regula- 2385. tion of p53 stability by Mdm2. Nature 387: 299–303. Harvey, M., A.T. Sands, R.S. Weiss, M.E. Hegi, R.W. Wiseman, Kuerbitz, S.J., B.S. Plunkett, W.V. Walsh, and M.B. Kastan. 1992. GENES & DEVELOPMENT 2989 Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press Sherr Wild-type p53 is a cell cycle checkpoint determinant follow- EMBO J. 17: 554–564. INK4a ing irradiation. Proc. Natl. Acad. Sci. 89: 7491–7495. Ruas, M. and G. Peters. 1998. The p16 /CDKN2A tumor Land, H., L.F. Parada, and R.A. Weinberg. 1983. Tumorigenic suppressor and its relatives. Biochim. Biophys. Acta Rev. conversion of primary embryo fibroblasts requires at least Cancer (in press). two cooperating oncogenes. Nature 304: 596–602. Ruley, H.E. 1983. Adenovirus early region 1A enables viral and Lanni, J.S. and T. Jacks. 1998. Characterization of the p53-de- cellular transforming genes to transform primary cells in pendent postmitotic checkpoint following spindle disrup- culture. Nature 304: 602–606. tion. Mol. Cell. Biol. 18: 1055–1064. Serrano, M., G.J. Hannon, and D. Beach. 1993. A new regulatory Lee, H.-W., M.A. Blasco, G.J. Gottlieb, J.W. Horber, C.W. Gre- motif in cell cycle control causing specific inhibition of cy- ider, and R.A. DePinho. 1998. Essential role of mouse telom- clin D/CDK4. Nature 366: 704–707. erase in highly proliferative organs. Nature 392: 569–574. Serrano, M., H.-W. Lee, L. Chin, C. Cordon-Cardo, D. Beach, Levine, A.J. 1997. p53, the cellular gatekeeper for growth and and R.A. DePinho. 1996. Role of the INK4a locus in tumor division. Cell 88: 323–331. suppression and cell mortality. Cell 85: 27–37. Livingstone, L.R., A. White, J. Sprouse, E. Livanos, T. Jacks, and Serrano, M., A.W. Lin, M.E. McCurrach, D. Beach, and S.W. T.D. Tlsty. 1992. Altered cell cycle arrest and gene amplifi- Lowe. 1997. Oncogenic ras provokes premature cell senes- INK4a cation potential accompany loss of wild-type p53. Cell cence associated with accumulation of p53 and p16 . 70: 923–935. Cell 88: 593–602. Lloyd, A.C., F. Obermuller, S. Staddon, C.F. Barth, M. McMa- Shan, B. and W.-H. Lee. 1994. Deregulated expression of E2F-1 hon, and H. Land. 1997. Cooperating oncogenes converge to induces S-phase entry and leads to apoptosis. Mol. Cell. Biol. regulate cyclin/cdk complexes. Genes & Dev. 11: 663–667. 14: 8166–8173. Lowe, S.W. and H.E. Ruley. 1993. Stabilization of the p53 tumor Sherr, C.J. 1996. Cancer cell cycles. Science 274: 1672–1677. suppressor is induced by adenovirus-5 E1A and accompanies Slebos, R.J.C., M.H. Lee, B.S. Plunkett, T.D. Kessis, B.O. Willi- apoptosis. Genes & Dev. 7: 535–545. ams, T. Jacks, L. Hedrick, M.B. Kastan, and K.R. Cho. 1994. Lowe, S.W., H.E. Ruley, T. Jacks, and D.E. Housman. 1993. p53-dependent G1 arrest involves pRB-related proteins and p53-dependent apoptosis modulates the cytotoxicity of anti- is disrupted by the human papillomavirus 16 E7 oncopro- cancer agents. Cell 74: 957–966. tein. Proc. Natl. Acad. Sci. 91: 5320–5324. Mao, L., A. Merlo, G. Bedi, G.I. Shapiro, C.D. Edwards, B.J. Stone, S., P. Jiang, P. Dayananth, S.V. Tavtigian, H. Katcher, D. INK4a Rollins, and D. Sidransky. 1995. A novel p16 transcript. Parry, G. Peters, and A. Kamb. 1995. Complex structure and Cancer Res. 55: 2995–2997. regulation of the p16(MTS1) locus. Cancer Res. 55: 2988– Metz, T., A.W. Harris, and J.M. Adams. 1995. Absence of p53 2994. allows direct immortalization of hematopoietic cells by the Stott, F., S.A. Bates, M. James, B.B. McConnell, M. Starborg, S. myc and raf oncogenes. Cell 82: 29–36. Brookes, I. Palmero, E. Hara, K.H. Vousden, and G. Peters. Morgenbesser, S.D., B.O. Williams, T. Jacks, and R.A. DePinho. 1998. The alternative product from the human CDKN2A ARF 1994. p53-dependent apoptosis produced by Rb-deficiency in locus, p14 , participates in a regulatory feedback loop with the developing mouse lens. Nature 371: 72–74. p53 and MDM2. EMBO J. (in press). Pan, H. and A.E. Griep. 1994. Altered cell cycle regulation in the Swafford, D.S., S.K. Middleton, W.A. Palmisano, K.J. Nikula, J. lens of HPV-16 E6 or E7 transgenic mice: Implications for Tesfaigzi, S.B. Baylin, J.G. Herman, and S.A. Belinsky. 1997. INK4a tumor suppressor gene function in development. Genes & Frequent aberrant methylation of p16 in primary rat Dev. 8: 1285–1299. lung tumors. Mol. Cell. Biol. 17: 1366–1374. Paulovich, A.G., D.P. Toczyski, and L.H. Hartwell. 1997. When Symonds, H., L. Krall, L. Remington, M. Saenz-Robles, S. Lowe, checkpoints fail. Cell 88: 315–321. T. Jacks, and T. Van Dyke. 1994. p53-dependent apoptosis Pomerantz, J., N. Schreiber-Agus, N.J. Lie ´ geois, A. Silverman, L. suppresses tumor growth and progression in vivo. Cell Alland, L. Chin, J. Potes, K. Chen, I. Orlow, H.-W. Lee, C. 78: 703–711. Cordon-Cardo, and R. DePinho. 1998. The Ink4a tumor sup- Thomas, A. and E. White. 1998. Suppression of the p300-depen- ARF pressor gene product, p19 , interacts with MDM2 and dent mdm2 negative-feedback loop induces the p53 apop- neutralizes MDM2’s inhibition of p53. Cell 92: 713–723. totic function. Genes & Dev. 12: 1975–1985. Qin, X.Q., D.M. Livingston, W.G. Kaelin, Jr., and P.D. Adams. Van Dyke, T. 1994. Analysis of viral-host protein interactions 1994. Deregulated transcription factor E2F-1 expression and tumorigenesis in transgenic mice. Semin. Cancer Biol. leads to S-phase entry and p53-mediated apoptosis. Proc. 5: 47–60. Natl. Acad. Sci. 91: 10918–19022. Wagner, A.J., J.M. Kokontis, and N. Hay. 1994. Myc-mediated Quelle, D.E., F. Zindy, R.A. Ashmun, and C.J. Sherr. 1995. Al- apoptosis requires wild-type p53 in a manner independent of ternative reading frames of the INK4a tumor suppressor gene cell cycle arrest and the ability of p53 to induce p21 waf1/ encode two unrelated proteins capable of inducing cell cycle cip1. Genes & Dev. 8: 2817–2830. arrest. Cell 83: 993–1000. Weinberg, R.A. 1995. The retinoblastoma protein and cell cycle Quelle, D.E., M. Cheng, R.A. Ashmun, and C.J. Sherr. 1997. control. Cell 81: 323–330. Cancer-associated mutations at the INK4a locus cancel cell ———. 1997. The cat and mouse games that genes, viruses, and INK4a cycle arrest by p16 but not by the alternative reading cells play. Cell 88: 573–575. ARF frame protein p19 . Proc. Natl. Acad. Sci. 94: 3436–3440. White, E. 1996. Life, death, and the pursuit of apoptosis. Genes Rao, L., M. Debbas, P. Sabbatini, D. Hockenberry, S. Korsmeyer, & Dev. 10: 1–15. and E. White. 1992. The adenovirus E1A proteins induce White, E., R. Cipriani, P. Sabbatini, and A. Denton. 1991. The apoptosis which is inhibited by E1B 19K and Bcl-2 proteins. adenovirus E1B 19-kilodalton protein overcomes the cyto- Proc. Natl. Acad. Sci. 89: 7742–7746. toxicity of E1A proteins. J. Virol. 65: 2968–2978. Roth, J., M. Dobbelstein, D. Freedman, T. Shenk, and A.J. Wu, X. and A.J. Levine. 1994. p53 and E2F-1 cooperate to me- Levine. 1998. Nucleo-cytoplasmic shuttling of the hdm2 on- diate apoptosis. Proc. Natl. Acad. Sci. 91: 3602–3606. coprotein regulates the levels of the p53 protein via a path- Wu, X., J.H. Bayle, D. Olson, and A.J. Levine. 1993. The p53– way used by the human immunodeficiency virus rev protein. mdm–2 autoregulatory feedback loop. Genes & Dev. 7: 2990 GENES & DEVELOPMENT Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press ARF tumor suppression 1126–1132. Xiong, Y., G.J. Hannon, H. Zhang, D. Casso, R. Kobayashi, and D. Beach. 1993. p21 is a universal inhibitor of cyclin kinases. Nature 366: 701–704. Yin, Y., M.A. Tainsky, F.Z. Bischoff, L.C. Strong, and G.M. Wahl. 1992. Wild-type p53 restores cell cycle control and inhibits gene amplification in cells with mutant p53 alleles. Cell 70: 937–948. Zhang, Y., Y. Xiong, and W.G. Yarbrough. 1998. ARF promotes MDM2 degradation and stabilizes p53: ARF-INK4a locus de- letion impairs both the Rb and p53 tumor suppressor path- ways. Cell 92: 725–734. Zindy, F., C.M. Eischen, D. Randle, T. Kamijo, J.L. Cleveland, C.J. Sherr, and M.F. Roussel. 1998. Myc signaling via the ARF tumor suppressor regulates p53-dependent apoptosis and immortalization. Genes & Dev. 12: 2424–2434. GENES & DEVELOPMENT 2991 Downloaded from genesdev.cshlp.org on November 12, 2021 - Published by Cold Spring Harbor Laboratory Press Charles J. Sherr Genes Dev. 1998, 12: Access the most recent version at doi:10.1101/gad.12.19.2984 This article cites 76 articles, 35 of which can be accessed free at: References http://genesdev.cshlp.org/content/12/19/2984.full.html#ref-list-1 License Receive free email alerts when new articles cite this article - sign up in the box at the top Email Alerting right corner of the article or click here. Service Cold Spring Harbor Laboratory Press

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