Differential cooperation of oncogenes with p53 and Bax to induce apoptosis in rhabdomyosarcoma
© Taylor et al; licensee BioMed Central Ltd. 2006
Received: 19 May 2006
Accepted: 02 November 2006
Published: 02 November 2006
Deregulated expression of oncogenes such as MYC and PAX3-FKHR often occurs in rhabdomyosarcomas. MYC can enhance cell proliferation and apoptosis under specific conditions, whereas PAX3-FKHR has only been described as anti-apoptotic.
In order to evaluate how MYC and PAX3-FKHR oncogenes influenced p53-mediated apoptosis, rhabdomyosarcoma cells were developed to independently express MYC and PAX3-FKHR cDNAs. Exogenous wild-type p53 expression in MYC transfected cells resulted in apoptosis, whereas there was only a slight effect in those transfected with PAX3-FKHR. Both oncoproteins induced BAX, but BAX induction alone without expression of wild-type p53 was insufficient to induce apoptosis. Data generated from genetically modified MEFs suggested that expression of all three proteins; MYC, BAX and p53, was required for maximal cell death to occur.
We conclude that cooperation between p53 and oncoproteins to induce apoptosis is dependent upon the specific oncoprotein expressed and that oncogene-mediated induction of BAX is necessary but insufficient to enhance p53-mediated apoptosis. These data demonstrate a novel relationship between MYC and p53-dependent apoptosis, independent of the ability of MYC to induce p53 that may be important in transformed cells other than rhabdomyosarcoma.
Rhabdomyosarcoma is the most common pediatric soft-tissue sarcoma. The two main subtypes, embryonal and alveolar, are characterized by specific morphologic features and chromosomal translocations. Alveolar rhabdomyosarcomas contain t(2;13) or t(1;13) translocations that generate fusion genes encoding either PAX3 or PAX7 and forkhead (FKHR or FOXO1a) transcription factors [1, 2]. The resulting fusion proteins are much stronger transcriptional activators than either PAX3 or PAX7 alone ; such increased activity is thought to contribute to the aggressive nature of alveolar rhabdomyosarcoma tumors . PAX3-FKHR expression enhances the proliferation rate and invasiveness of rhabdomyosarcoma tumors , and enhances expression of the anti-apoptotic protein BCL-XL . However, tumors with PAX3-FKHR often express other deregulated oncogenes [7, 8], and Pax3-FKHR knock-in mice do not develop tumors  suggesting that the oncogenic potential of this fusion protein is weak.
Deregulated expression of members of the MYC family of genes is the most common oncogenic change, other than generation of PAX fusion proteins, observed in this tumor type [7, 8, 10–12]. MYC proteins are involved in the regulation of the cell cycle, proliferation, and apoptosis [13–18]. MYC proteins dimerize with MAX  and act as sequence-specific transcriptional activators . By activating the p14ARF/p53 pathway, MYC proteins induce apoptosis . Specifically, c-MYC activates ARF, which then binds MDM2; thereby releasing p53 which induces apoptosis . In this manner, cells in which the ARF pathway is functional are protected from the potential transforming effects of MYC protein. However, MYC can induce apoptosis through mechanisms independent of p53 and ARF; for example, MYC can directly induce expression of BAX  and ornithine decarboxylase , induce release of cytochrome c from the mitochondria , and play a role in the FAS apoptotic pathway . ARF has also been shown to regulate MYC-mediated apoptosis independent of p53  but to date no relationship between MYC and p53-dependent apoptosis has been described independent of ARF induction.
The goal of the present study was to evaluate how p53-mediated apoptosis is influenced by the expression of two different oncogenes, c-MYC and PAX3-FKHR. We demonstrate that apoptosis can be enhanced in cells that express c-MYC together with wild-type p53 and BAX, but that no similar cooperation exists between PAX3-FKHR and p53 or BAX. In addition, data demonstrate that although c-MYC can induce apoptosis in a p53-independent manner, all three proteins, c-MYC, p53 and BAX are required to induce maximal cell death.
To evaluate whether the PAX3-FKHR cells were more resistant to apoptosis induced by exposure to a genotoxic agent, the three cell lines; control, c-MYC and PAX3-FKHR expressing cells were exposed to 10 μM doxorubicin for 24 hours prior to analysis of cell viability by a propidium iodide exclusion assay. Figure 4B demonstrates that the PAX3-FKHR cells were slightly more sensitive to the cytotoxic effects of doxorubicin compared to the MYC expressing cells.
To evaluate whether expression of the pro-apoptotic protein BAX was induced upon exogenous expression of either MYC or p53, the same Western membrane used to evaluate PARP cleavage was incubated with anti-BAX antibodies. Elevated BAX expression was observed in all cells that expressed exogenous wild-type p53 or the c-MYC or PAX3-FKHR oncogenes, including samples in which PARP cleavage was not detected (Figure 4). Therefore, induction of BAX is insufficient to induce apoptosis in the oncogene-expressing cells. Significant apoptosis was only observed in the c-MYC-expressing cells when co-expressed with p53. The same Western membrane was also incubated with antibodies against p53 and p21Waf1/Cip1. High-level expression of mutant p53 was observed in all clones, and expression of functional exogenous wild-type p53 was demonstrated by the induction of the p53 target genes, p21 and BAX.
Rhabdomyosarcoma cells expressing one of the two oncoproteins (c-MYC or PAX3-FKHR) responded in a different manner to exogenous wild-type p53 expression (Figures 2 and 3). PAX3-FKHR has been previously characterized as a relatively weak oncoprotein , with an anti-apoptotic phenotype . However in this study no anti-apoptotic effects of PAX3-FKHR expression were observed. Instead PAX3-FKHR weakly enhanced p53-mediated apoptosis.
The oncogenic potential of c-MYC is well characterized [16–18], and an apoptotic phenotype has been described [14, 34]. Data presented here demonstrate that c-MYC expression alone does not enhance apoptosis of JR1 cells; co-expression with wild-type p53 is required, and this combination resulted in the death of approximately 90% of cells (Figures 2 and 3). A cooperation of wild-type p53 with MYC proteins to induce apoptosis has previously been shown to be ARF-dependent  and ARF-independent . ARF binds MDM2 and sequesters it to the nucleolus; thus, MDM2 releases control of p53, and p53 is no longer targeted for degradation by the proteasomal pathway. As a result, p53 protein levels increase . MYC induction of p53 by an ARF-independent mechanism can be mediated through the induction of p53 phosphorylation . However, in the experiments described here p53 and MYC are expressed exogenously and therefore cooperate to induce apoptosis in a manner that is independent of ARF and the ability of MYC to induce p53 expression.
BAX, a proapoptotic member of the BCL-2 family, is a transcriptional target of p53  and MYC . However, Figure 4 shows that elevated BAX expression was observed in the PAX3-FKHR-expressing cells as well as those expressing MYC, demonstrating that BAX can also be induced by PAX3-FKHR. In the control cells that did not express either MYC or PAX3-FKHR, elevated BAX expression was observed only after Ad-p53 transduction. In the cell lines expressing each of the oncoproteins, Ad-p53 transduction only minimally enhanced BAX protein expression above the level induced by the oncogenes. MYC reportedly cooperates with BAX to induce apoptosis , and loss of BAX in a transgenic mouse model impairs MYC-induced apoptosis and circumvents the selection for p53 mutations during MYC-mediated lymphomagenesis . However, the results presented in Figures 2, 3, 4 demonstrate that in the JR1 rhabdomyosarcoma cells increased BAX expression induced by either c-MYC or PAX3-FKHR was insufficient to induce apoptosis. The observation that elevated BAX protein together with expression of wild-type p53 did not significantly induce the death of PAX3-FKHR-expressing cells demonstrated that a MYC component is required for the induction of apoptosis by p53 in these cells. We confimed that these results were oncogene specific by demonstrating that the cells expressing either c-MYC or PAX3-FKHR responded in a similar manner when exposed to genotoxic damage (Figure 4B).
Caspase 3 has been shown to be involved in MYC-induced apoptosis . Indeed, our finding that cleavage of the caspase 3 substrate, PARP, was associated with apoptosis of JR1 cells suggested that caspase 3 also played a role in MYC and p53-mediated cell death observed here. Although BCL-2 has been previously shown to inhibit MYC-induced apoptosis [29, 30], BCL-2 expression in the MYC-expressing cells did not decrease the proportion of cells that died upon expression of p53 (Figure 5). These data demonstrate that BCL-2 expression only minimally affected the apoptosis of JR1 cells and together with the observation that PAX3-FKHR induced BAX in the same cells with minimal effects on apoptosis suggests that BAX involvement in the MYC and p53-induced cell death is limited. The lower level of p21 induced by p53 in the MYC-expressing cells (Figure 4) is consistent with the published report that MYC downregulates transcription of the p21 promoter [31–33]. MYC suppression of p21 activity has been suggested as a mechanism by which p53 function can be switched from cytostatic to apoptotic [40, 41]. This hypothesis is consistent with the results presented in Figure 3, which demonstrate that the proportion of the cell population undergoing apoptosis increased when the G1 checkpoint was attenuated. However, p21 expression was elevated in Bax-/- MEFs in response to c-MYC expression (Figure 6). This result does not support previously published data and suggests differences in the response of the rhabdomyosarcoma cells compared to MEFs with respect to MYC expression.
Despite inherent differences in the cell types we evaluated the relative contributions of MYC, p53 and BAX to the induction of apoptosis in MEFs. Only by the use of genetically modified cells, such as Bax-null MEFs, can the effects of each of the three proteins be analyzed independently (Figure 6). In the MEFs, MYC induced cell death independent of wild-type p53. However, maximal cell killing was observed only when all three proteins were expressed together.
The process of immortalization often deregulates cellular apoptotic pathways, for example MYC expression had no effect on survival of JR1 rhabdomyosarcoma cells yet its expression in Bax +/+ MEFs induced cell death. Nevertheless, the cooperation between p53 and MYC to induce apoptosis was observed in both cell types demonstrating that this apoptotic pathway remained intact in rhabdomyosarcoma cells.
From the data presented here we conclude that the ability of wild-type p53 to induce apoptosis in any given cell type is dependent upon the oncoprotein expressed and that even though different oncoproteins may induce BAX, for example PAX3-FKHR and MYC as shown here, elevated BAX expression is insufficient to induce apoptosis.
Cell lines and transfections
JR1 embryonal rhabdomyosarcoma cells, which contain a p53 Arg248Trp mutation , were established at the Institute of Child Health, London, UK . These cells were grown in RPMI-1640 cell culture media supplemented with 10% fetal bovine serum (FBS) in a humidified environment at 37°C and 5% CO2, 95% air. The BAX-/- and BAX+/+ mouse embryo fibroblasts (MEFs) were obtained from John Cleveland (St. Jude Children's Research Hospital, Memphis TN) and grown in DMEM media supplemented with 10% FBS, 2% glutamine, 1% non-essential amino acids and 1% β-mercaptoethanol under the same conditions. These cells were grown to at least passage 20 before use in the experiments described in this paper in order to inactivate endogenous p53 activity.
The c-MYC cDNA was subcloned into the pIRESneo mammalian expression vector (Clontech, Palo Alto, CA), and the resulting construct was transfected into JR1 cells using the Profectin Mammalian Transfection System (Promega, Madison WI). Individual clones resistant to 200 μg/ml G418 were expanded, and their c-MYC mRNA expression was evaluated by Northern blot analysis (Figure 1). Control cells that contained the parental vector were developed by transfection with the pIRESneo plasmid that did not contain the c-MYC cDNA. Transcriptional activity of c-MYC in the transfected clones was analyzed using a MYC-responsive promoter reporter plasmid  and a dual luciferase assay (Promega). We have previously described the generation and characterization of JR1 cells expressing the PAX3-FKHR cDNA . RT-PCR showed that these cells express PAX3-FKHR, and luciferase assays of cells that had been transfected with a PAX-responsive luciferase reporter plasmid demonstrated that PAX transcriptional activity in the transfected clones was increased .
Viral vectors and cell transduction
Ad-p53 (Av1p53) was provided by Genetic Therapy Inc. (a Novartis Company, Gaithersburg MD) . Ad-VC and Ad-Bcl2 were provided by Dr. Janet Houghton (St. Jude). Cells were transduced with adenoviral vectors at the multiplicity of infection (m.o.i.) as described in the Results. Retroviral plasmids; MSCV-IRES-MYC-ER-GFP and MSCV-IRES-GFP, were obtained from John Cleveland (St. Jude) and have previously been described . These plasmids were independently transiently transfected with an ecotropic helper retroviral plasmid into 293T packaging cells in order to generate retroviral particles. Retroviral supernatant was harvested from the 293T cells at 24 and 48 h following transfection. This supernatant was filtered and added to MEFs (at a dilution of 1:2) together with hexadimethrinebromide (Polybrene, Sigma) at a final concentration of 1 μg/ml. After 24 h 4-hydroxytamoxifen (Sigma) was added to a final concentration of 1 μM to induce MYC expression. Cells were harvested after a further 24 h for Western and PI exclusion analyses.
Cytotoxicity assay and cell cycle analysis
Cells were plated in triplicate at a density of 1 × 105 per well in 6-well plates. After a 24-h period of attachment, cells were exposed to adenoviral vectors whose m.o.i. ranged from 0.2 to 20. The total number of cells in each well was counted after the untreated cells had doubled 3 times. Data are presented as a percentage of untreated cells.
Cell cycle analysis was carried out on cells transduced with virus (m.o.i. = 10) for 24 h. Cells were suspended at a concentration of 1 × 106/ml in a solution of propidium iodide, and their DNA content was analyzed as previously described . Propidium iodide cell exclusion assays were also carried out as a measure of cell death. Pelleted cells were resuspended in the propidium iodide solution used for DNA content analysis that did not contain any Triton X-100, and analyzed by flow cytometry.
Northern and Western blot analyses
Northern blot analysis was conducted as described by Sambrook et al. . Cells for Western blot analysis were transduced for 24 h with the adenoviral vectors at an m.o.i. of 10. Cell extracts were prepared, and Western blot analyses were performed as previously described . The p53 antibody (DO1-HRP) and the antibodies against BAX, BCL-2, c-MYC and p21 were obtained from Santa Cruz Biotechnology (Santa Cruz, CA). The poly (ADP ribose) polymerase (PARP) antibody was purchased from PharMingen (San Diego, CA), and the β-tubulin antibody was obtained from ICN Biomedicals, Inc (Aurora, OH).
mouse embryo fibroblast
multiplicity of infection
poly (ADP ribose) polymerase
This work was supported by grants from the National Cancer Institute CA92401 and CA21765, and by the American Lebanese Syrian Associated Charities (ALSAC).
We thank Misty Cheney for excellent technical assistance. Also we thank Julia Cay Jones and the St. Jude Scientific Editing Department for editing the manuscript, the St. Jude Department of Biomedical Communications for preparing the figures.
- Trent J, Casper J, Meltzer P, Thompson F, Fogh J: Nonrandom chromosomal alterations in rhabdomyosarcoma. Cancer Genet Cytogenet. 1985, 16: 189-197. 10.1016/0165-4608(85)90045-7View ArticlePubMedGoogle Scholar
- Galili N, Davis RJ, Fredericks WJ, Mukohopadhyay S, Rauscher FJ, Emanual BS, Rovera G, Barr FG, Rauscher FJ: Fusion of a fork head domain gene to Pax3 in the solid tumor alveolar rhabdomyosarcoma. Nat Genet. 1993, 5: 230-235. 10.1038/ng1193-230View ArticlePubMedGoogle Scholar
- Bennicelli JL, Edwards RH, Barr FG: Mechanism for transcriptional gain of function resulting from chromosomal translocation in alveolar rhabdomyosarcoma. Proc Natl Acad Sci USA. 1996, 93: 5455-5459. 10.1073/pnas.93.11.5455PubMed CentralView ArticlePubMedGoogle Scholar
- Anderson J, Gordon T, McManus A, Mapp T, Gould S, Kelsey A, McDowell H, Pinkerton R, Shipley J, Pritchard-Jones K: Detection of the PAX3-FKHR fusion gene in paediatric rhabdomyosarcoma: a reproducible predictor of outcome?. Br J Cancer. 2001, 85 (6): 831-835. 10.1054/bjoc.2001.2008PubMed CentralView ArticlePubMedGoogle Scholar
- Anderson J, Ramsay A, Gould S, Pritchard-Jones K: PAX3-FKHR induces morphological change and enhances cellular proliferation and invasion in rhabdomyosarcoma. Am J Pathol. 2001, 159 (3): 1089-1096.PubMed CentralView ArticlePubMedGoogle Scholar
- Margue CM, Bernasconi M, Barr FG, Schafer BW: Transcriptional modulation of the anti-apoptotic protein BCL-XL by the paired box transcription factors PAX3 and PAX3/FKHR. Oncogene. 2000, 19 (25): 2921-2929. 10.1038/sj.onc.1203607View ArticlePubMedGoogle Scholar
- Dias P, Kumar P, Marsden HB, Gattamaneni HR, Heighway J, Kumar S: N-myc gene is amplified in alveolar rhabdomyosarcomas (RMS) but not in embryonal RMS. Int J Cancer. 1990, 45 (4): 593-596.View ArticlePubMedGoogle Scholar
- Driman D, Thorner PS, Greenberg ML, Chilton-MacNeill S, Squire J: MYCN gene amplification in rhabdomyosarcoma. Cancer. 1994, 73 (8): 2231-2237. 10.1002/1097-0142(19940415)73:8<2231::AID-CNCR2820730832>3.0.CO;2-EView ArticlePubMedGoogle Scholar
- Lagutina I, Conway SJ, Sublett J, Grosveld GC: Pax3-FKHR knock-in mice show developmental aberrations but do not develop tumors. Mol Cell Biol. 2002, 22 (20): 7204-7216. 10.1128/MCB.22.20.7204-7216.2002PubMed CentralView ArticlePubMedGoogle Scholar
- Dias P, Kumar P, Marsden HB, Gattamaneni HR, Kumar S: N- and c-myc oncogenes in childhood rhabdomyosarcoma [letter]. J Natl Cancer Inst. 1990, 82 (2): 151-View ArticlePubMedGoogle Scholar
- Kouraklis G, Triche TJ, Wesley R, Tsokos M: Myc oncogene expression and nude mouse tumorigenicity and metastasis formation are higher in alveolar than embryonal rhabdomyosarcoma cell lines. Pediatr Res. 1999, 45 (4 Pt 1): 552-558.View ArticlePubMedGoogle Scholar
- Toffolatti L, Frascella E, Ninfo V, Gambini C, Forni M, Carli M, Rosolen A: MYCN expression in human rhabdomyosarcoma cell lines and tumour samples. J Pathol. 2002, 196 (4): 450-458. 10.1002/path.1068View ArticlePubMedGoogle Scholar
- Luscher B, Eisenman RN: New light on Myc and Myb. Part I. Myc. Genes Dev. 1990, 4 (12A): 2025-2035.View ArticlePubMedGoogle Scholar
- Packham G, Cleveland JL: c-Myc and apoptosis. Biochim Biophys Acta. 1995, 1242 (1): 11-28.PubMedGoogle Scholar
- Thompson EB: The many roles of c-myc in apoptosis. Annu Rev Physiol. 1998, 60: 575-600. 10.1146/annurev.physiol.60.1.575View ArticlePubMedGoogle Scholar
- Pelengaris S, Rudolph B, Littlewood T: Action of Myc in vivo - proliferation and apoptosis. Curr Opin Genet Dev. 2000, 10 (1): 100-105. 10.1016/S0959-437X(99)00046-5View ArticlePubMedGoogle Scholar
- Levens D: Disentangling the MYC web. Proc Natl Acad Sci U S A. 2002, 99 (9): 5757-5759. 10.1073/pnas.102173199PubMed CentralView ArticlePubMedGoogle Scholar
- Pelengaris S, Khan M, Evan G: c-MYC: more than just a matter of life and death. Nat Rev Cancer. 2002, 2: 764-776. 10.1038/nrc904View ArticlePubMedGoogle Scholar
- Blackwood EM, Luscher B, Eisenman RN: Myc and Max associate in vivo. Genes Dev. 1992, 6 (1): 71-80.View ArticlePubMedGoogle Scholar
- Wagner AJ, Kokontis JM, Hay N: Myc-mediated apoptosis requires wild-type p53 in a manner independent of cell cycle arrest and the ability of p53 to induce p21waf1/cip1. Genes and Development. 1994, 8: 2817-2830.View ArticlePubMedGoogle Scholar
- Zindy F, Eischen CM, Randle DH, Kamijo T, Cleveland JL, Sherr CJ, Roussel MF: Myc signaling via the ARF tumor suppressor regulates p53-dependent apoptosis and immortalization. Genes and Devel. 1998, 12: 2424-2433.View ArticleGoogle Scholar
- Sherr CJ: Tumor surveillance via the ARF-p53 pathway. Genes and Development. 1998, 12: 2984-2991.View ArticlePubMedGoogle Scholar
- Mitchell KO, Ricci MS, Miyashita T, Dicker DT, Jin Z, Reed JC, El-Deiry WS: Bax is a transcriptional target and mediator of c-myc-induced apoptosis. Cancer Res. 2000, 60 (22): 6318-6325.PubMedGoogle Scholar
- Packham G, Cleveland JL: The role of ornithine decarboxylase in c-Myc-induced apoptosis. Curr Top Microbiol Immunol. 1995, 194: 283-290.PubMedGoogle Scholar
- Juin P, Hueber AO, Littlewood T, Evan G: c-Myc-induced sensitization to apoptosis is mediated through cytochrome c release. Genes Dev. 1999, 13 (11): 1367-1381.PubMed CentralView ArticlePubMedGoogle Scholar
- Hueber AO, Zornig M, Lyon D, Suda T, Nagata S, Evan GI: Requirement for the CD95 receptor-ligand pathway in c-Myc-induced apoptosis. Science. 1997, 278: 1305-1309. 10.1126/science.278.5341.1305View ArticlePubMedGoogle Scholar
- Qi Y, Gregory MA, Li Z, Brousal JP, West K, Hann SR: p19ARF directly and differentially controls the functions of c-Myc independently of p53. Nature. 2004, 431: 712-717. 10.1038/nature02958View ArticlePubMedGoogle Scholar
- Shetty S, Taylor AC, Harris LC: Selective chemosensitization of rhabdomyosarcoma cell lines following wild-type p53 adenoviral transduction. Anti-Cancer Drugs. 2002, 13: 881-889. 10.1097/00001813-200209000-00015View ArticlePubMedGoogle Scholar
- Bissonnette RP, Echeverri F, Mahboubi A, Green DR: Apoptotic cell death induced by c-myc is inhibited by bcl-2. Nature. 1992, 359 (6395): 552-554. 10.1038/359552a0View ArticlePubMedGoogle Scholar
- Fanidi A, Harrington EA, Evan GI: Cooperative interaction between c-myc and bcl-2 proto-oncogenes. Nature. 1992, 359 (6395): 554-556. 10.1038/359554a0View ArticlePubMedGoogle Scholar
- Mitchell KO, El-Deiry WS: Overexpression of c-Myc inhibits p21WAF1/CIP1 expression and induces S-phase entry in 12-O-tetradecanoylphorbol-13-acetate (TPA)-sensitive human cancer cells. Cell Growth Differ. 1999, 10 (4): 223-230.PubMedGoogle Scholar
- Gartel AL, Ye X, Goufman E, Shianov P, Hay N, Najmabadi F, Tyner AL: Myc represses the p21(WAF1/CIP1) promoter and interacts with Sp1/Sp3. Proc Natl Acad Sci U S A. 2001, 98 (8): 4510-4515. 10.1073/pnas.081074898PubMed CentralView ArticlePubMedGoogle Scholar
- Herold S, Wanzel M, Beuger V, Frohme C, Beul D, Hillukkala T, Syvaoja J, Saluz HP, Haenel F, Eilers M: Negative regulation of the mammalian UV response by Myc through association with Miz-1. Mol Cell. 2002, 10 (3): 509-521. 10.1016/S1097-2765(02)00633-0View ArticlePubMedGoogle Scholar
- Packham G, Porter CW, Cleveland JL: c-Myc induces apoptosis and cell cycle progression by separable, yet overlapping, pathways. Oncogene. 1996, 13 (3): 461-469.PubMedGoogle Scholar
- Lindstrom MS, Wiman KG: Myc and E2F1 induce p53 through p14ARF-independent mechanisms in human fibroblasts. Oncogene. 2003, 22 (32): 4993-5005. 10.1038/sj.onc.1206659View ArticlePubMedGoogle Scholar
- Miyashita T, Reed JC: Tumor suppressor p53 is a direct transcriptional activator of the human bax gene. Cell. 1995, 80: 293-299. 10.1016/0092-8674(95)90513-8View ArticlePubMedGoogle Scholar
- Juin P, Hunt A, Littlewood T, Griffiths B, Swigart LB, Korsmeyer S, Evan G: c-Myc functionally cooperates with Bax to induce apoptosis. Mol Cell Biol. 2002, 22 (17): 6158-6169. 10.1128/MCB.22.17.6158-6169.2002PubMed CentralView ArticlePubMedGoogle Scholar
- Eischen CM, Roussel MF, Korsmeyer SJ, Cleveland JL: Bax loss impairs Myc-induced apoptosis and circumvents the selection of p53 mutations during Myc-mediated lymphomagenesis. Mol Cell Biol. 2001, 21 (22): 7653-7662. 10.1128/MCB.21.22.7653-7662.2001PubMed CentralView ArticlePubMedGoogle Scholar
- Kangas A, Nicholson DW, Holtta E, Hottla E: Involvement of CPP32/Caspase-3 in c-Myc-induced apoptosis. Oncogene. 1998, 16 (3): 387-398. 10.1038/sj.onc.1201779View ArticlePubMedGoogle Scholar
- Seoane J, Le HV, Massague J: Myc suppression of the p21(Cip1) Cdk inhibitor influences the outcome of the p53 response to DNA damage. Nature. 2002, 419 (6908): 729-734. 10.1038/nature01119View ArticlePubMedGoogle Scholar
- Vousden KH: Switching from life to death: the Miz-ing link between Myc and p53. Cancer Cell. 2002, 2 (5): 351-352. 10.1016/S1535-6108(02)00186-1View ArticlePubMedGoogle Scholar
- Taylor AC, Shu L, Danks MK, Poquette CA, Shetty S, Thayer MJ, Houghton PJ, Harris LC: P53 mutation and MDM2 amplification frequency in pediatric rhabdomyosarcoma tumors and cell lines. Med Pediatr Oncol. 2000, 35 (2): 96-103. 10.1002/1096-911X(200008)35:2<96::AID-MPO2>3.0.CO;2-ZView ArticlePubMedGoogle Scholar
- Clayton J, Pincott JR, van den Berghe JA, Kemshead JT: Comparative studies between a new human rhabdomyosarcoma cell line, JR-1 and its tumor of origin. Br J Cancer. 1986, 58: 83-90.View ArticleGoogle Scholar
- Iyengar RV, Pawlik CA, Krull EJ, Phelps DA, Burger RA, Harris LC, Potter PM, Danks MK: Use of a modified ornithine decarboxylase promoter to achieve efficient c-MYC- or N-MYC-regulated protein expression. Cancer Res. 2001, 61 (7): 3045-3052.PubMedGoogle Scholar
- Pirollo KF, Hao Z, Rait A, Jang YJ, Fee Jr WE, Ryan P, Chiang Y, Chang EH: p53 mediated sensitization of squamous cell carcinoma of the head and neck to radiotherapy. Oncogene. 1997, 14: 1735-1746. 10.1038/sj.onc.1201116View ArticlePubMedGoogle Scholar
- McKenzie PP, Guichard SM, Middlemas DS, Ashmun RA, Danks MK, Harris LC: Wild-type p53 can induce p21 and apoptosis in neuroblastoma cells but the DNA damage-induced G1 checkpoint function is attenuated. Clin Cancer Res. 1999, 5 (12): 4199-4207.PubMedGoogle Scholar
- Sambrook J, Fritsch EF, Maniatis T: Molecular Cloning: A Laboratory Manual. 1989, Cold Spring Harbor, NY , Cold Spring Harbor Press, 2nd.Google Scholar
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