Pharmacologic p53 Activation Blocks Cell Cycle Progression but Fails to Induce Senescence in Epithelial Cancer Cells

Huang, Baoying; Deo, Dayanand; Xia, Mingxuan; Vassilev, Lyubomir T.

doi:10.1158/1541-7786.mcr-09-0144

Cited by 64 publications

(66 citation statements)

References 35 publications

(73 reference statements)

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“…These findings are also in agreement with published studies of other cancer cell lines with functional apoptotic pathways (35). This suggests that apoptotic pathways are intact in all 6 wild-type p53 Ewing sarcoma cell lines used in this study, consistent with previous studies (4).…”

Section: Discussionsupporting

confidence: 93%

Nutlin-3a Is a Potential Therapeutic for Ewing Sarcoma

Pishas

Al-Ejeh

Zinonos

et al. 2011

Clinical Cancer Research

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Purpose: Although mutations in the TP53 gene occur in half of all cancers, approximately 90% of Ewing sarcomas retain a functional wild-type p53. The low frequency of TP53 alterations in Ewing sarcoma makes this tumor type an ideal candidate for p53-targeted therapies. In this study, we have examined the molecular and cellular responses of cultured Ewing sarcoma cell lines following exposure to Nutlin-3a, a recently developed MDM2 antagonist.Experimental Design: The ability of Nutlin-3a to impart apoptosis or cell cycle arrest in a p53-dependent manner was determined in a comprehensive panel of Ewing sarcoma cell lines. The capacity of Nutlin-3a to augment the antitumor activity of MDM4 antagonists and cytotoxic agents currently used in the clinical treatment of Ewing sarcoma was also investigated.Results: Apoptosis was the primary response of wild-type p53 expressing Ewing sarcoma cell lines. The cytotoxicity of Nultin-3a was also synergistic with the chemotherapeutic agents, vincristine, actinomycin D, doxorubicin, and etoposide in a concentration-dependent manner. Significant MDM4 protein overexpression was observed in Ewing sarcoma cell lines of wild-type p53 status, providing a mechanism through which Ewing sarcomas can develop in the absence of TP53 alterations. This study provides the first evidence of synergism between targeted inhibition of MDM2 and MDM4.Conclusion: Our findings suggest that p53-dependent apoptosis is the primary cellular response of Ewing sarcoma cell lines following exposure to Nutlin-3a. Furthermore, Nutlin-3a can synergize with the current Ewing sarcoma chemotherapy protocols, suggesting p53 activation as a novel systemic therapeutic approach for this disease.

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Section: Discussionsupporting

confidence: 93%

Nutlin-3a Is a Potential Therapeutic for Ewing Sarcoma

Pishas

Al-Ejeh

Zinonos

et al. 2011

Clinical Cancer Research

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“…Although reports have suggested that nutlin induces senescence, a state of irreversible arrest, recent findings 24,25 and our results suggest that nutlin-3 treatment induces reversible growth arrest, but not senescence, in normal epithelial cells and cancer cells expressing wild-type p53. The nongenotoxic activation of p53 by nutlin-3 in vivo is well tolerated in nude mice without significant adverse side effects, 8 and studies using a myc inhibitor have shown that the blocking of cell division in normal tissues for up to a week is reversible without pathology.…”

Section: Discussioncontrasting

confidence: 83%

Combination of nutlin-3 and VX-680 selectively targets p53 mutant cells with reversible effects on cells expressing wild-type p53

et al. 2010

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Chemotherapeutics (e.g., aurora kinase inhibitors) designed to target proliferative cells are often nonspecific for tumor cells as normal cycling cells are also susceptible. Indeed, one of the major dose-limiting toxicities of aurora kinase inhibitors is a dangerous depletion of neutrophils in patients. In this study we proposed a strategy to selectively target p53 mutant cells while sparing normal ones. The strategy is based on the understanding that normal cells have an intact p53 pathway but not tumor cells carrying p53 mutations. Nongenotoxic activation of p53 using nutlin led to a reversible activation of G1 and G2 arrest in normal cells, which prevents them from entering mitosis, thus protecting them from the side effects of aurora kinase inhibition (VX-680), namely endoreduplication and apoptosis. Cells carrying mutant p53 are selectively killed by the nutlin/VX-680 combination, whereas p53 wild-type cells retain their proliferative capacity. The major implications drawn from these results are:(1) reversible nongenotoxic activation of p53 may be used as a strategy for the chemoprotection of normal tissues, and (2) aurora kinase inhibitors may have alleviated side effects when used in combination with nutlin-like inhibitors. We highlight the distinct roles of p53 and p73 in mediating the cellular responses to VX-680 and suggest that dual protection by p53 and p73 are needed to guard against endoreduplication and polyploidy.

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“…Specifically, exposure to 10 M Nutlin-3a for up to 6 days induced a senescent-like arrest that included expression of senescenceassociated ␤-galactosidase in multiple p53 wild-type cancer cell lines (13,14). Despite this arrest, nearly 100% of Nutlin-3a-treated cells were reported to resume cycling after Nutlin removal, as determined by their ability to incorporate BrdUrd.…”

Section: Discussionmentioning

confidence: 99%

“…Nutlin-3a was reported to cause permanent, irreversible arrest (senescence) in fibroblasts and fibrosarcoma cells that was dependent in some cases on the length of Nutlin-3a exposure (11,12). However, recent studies have reported that cell cycle arrest induced by prolonged Nutlin-3a treatment in p53 wild-type cells is largely if not entirely reversible (13,14). Specifically, exposure to 10 M Nutlin-3a for up to 6 days induced a senescent-like arrest that included expression of senescence-associated ␤-galactosidase in multiple p53 wild-type cancer cell lines.…”

mentioning

confidence: 99%

Persistent p21 Expression after Nutlin-3a Removal Is Associated with Senescence-like Arrest in 4N Cells

Maki

2010

Journal of Biological Chemistry

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Nutlin-3a is a preclinical drug that stabilizes p53 by blocking the interaction between p53 and MDM2. In our previous study, Nutlin-3a promoted a tetraploid G 1 arrest in two p53 wild-type cell lines (HCT116 and U2OS), and both cell lines underwent endoreduplication after Nutlin-3a removal. Endoreduplication gave rise to stable tetraploid clones resistant to therapy-induced apoptosis. Prior knowledge of whether cells are susceptible to Nutlin-induced endoreduplication and therapy resistance could help direct Nutlin-3a-based therapies. In the present study, Nutlin-3a promoted a tetraploid G 1 arrest in multiple p53 wildtype cell lines. However, some cell lines underwent endoreduplication to relatively high extents after Nutlin-3a removal whereas other cell lines did not. The resistance to endoreduplication observed in some cell lines was associated with a prolonged 4N arrest after Nutlin-3a removal. Knockdown of either p53 or p21 immediately after Nutlin-3a removal could drive endoreduplication in otherwise resistant 4N cells. Finally, 4N-arrested cells retained persistent p21 expression; expressed senescence-associated ␤-galactosidase; displayed an enlarged, flattened phenotype; and underwent a proliferation block that lasted at least 2 weeks after Nutlin-3a removal. These findings demonstrate that transient Nutlin-3a treatment can promote an apparently permanent proliferative block in 4N cells of certain cell lines associated with persistent p21 expression and resistance to endoreduplication.

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Pharmacologic p53 Activation Blocks Cell Cycle Progression but Fails to Induce Senescence in Epithelial Cancer Cells

Cited by 64 publications

References 35 publications

Nutlin-3a Is a Potential Therapeutic for Ewing Sarcoma

Nutlin-3a Is a Potential Therapeutic for Ewing Sarcoma

Combination of nutlin-3 and VX-680 selectively targets p53 mutant cells with reversible effects on cells expressing wild-type p53

Persistent p21 Expression after Nutlin-3a Removal Is Associated with Senescence-like Arrest in 4N Cells

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