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P53-mediated senescence impairs the apoptotic response to chemotherapy and clinical outcome in breast cancer.

ABSTRACT: Studies on the role of TP53 mutation in breast cancer response to chemotherapy are conflicting. Here, we show that, contrary to dogma, MMTV-Wnt1 mammary tumors with mutant p53 exhibited a superior clinical response compared to tumors with wild-type p53. Doxorubicin-treated p53 mutant tumors failed to arrest proliferation, leading to abnormal mitoses and cell death, whereas p53 wild-type tumors arrested, avoiding mitotic catastrophe. Senescent tumor cells persisted, secreting senescence-associated cytokines exhibiting autocrine/paracrine activity and mitogenic potential. Wild-type p53 still mediated arrest and inhibited drug response even in the context of heterozygous p53 point mutations or absence of p21. Thus, we show that wild-type p53 activity hinders chemotherapy response and demonstrate the need to reassess the paradigm for p53 in cancer therapy.

SUBMITTER: Jackson JG

PROVIDER: S-EPMC3376352 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature

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p53-mediated senescence impairs the apoptotic response to chemotherapy and clinical outcome in breast cancer.

Jackson James G JG Pant Vinod V Li Qin Q Chang Leslie L LL Quintás-Cardama Alfonso A Garza Daniel D Tavana Omid O Yang Peirong P Manshouri Taghi T Li Yi Y El-Naggar Adel K AK Lozano Guillermina G

Cancer cell 20120601 6

Studies on the role of TP53 mutation in breast cancer response to chemotherapy are conflicting. Here, we show that, contrary to dogma, MMTV-Wnt1 mammary tumors with mutant p53 exhibited a superior clinical response compared to tumors with wild-type p53. Doxorubicin-treated p53 mutant tumors failed to arrest proliferation, leading to abnormal mitoses and cell death, whereas p53 wild-type tumors arrested, avoiding mitotic catastrophe. Senescent tumor cells persisted, secreting senescence-associate ...[more]

PMID: 22698404

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Project description:BACKGROUND: P53 activation can trigger various outcomes, among them reversible growth arrest or cellular senescence. It is a live debate whether these outcomes are influenced by quantitative or qualitative mechanisms. Furthermore, the relative contribution of p53 to Ras-induced senescence is also matter of controversy. METHODOLOGY/PRINCIPAL FINDINGS: This study compared situations in which different signals drove senescence with increasing levels of p53 activation. The study revealed that the levels of p53 activation do not determine the outcome of the response. This is further confirmed by the clustering of transcriptional patterns into two broad groups: p53-activated or p53-inactivated, i.e., growth and cellular arrest/senescence. Furthermore, while p53-dependent transcription decreases after 24 hrs in the presence of active p53, senescence continues. Maintaining cells in the arrested state for long periods does not switch reversible arrest to cellular senescence. Together, these data suggest that a Ras-dependent, p53-independent, second signal is necessary to induce senescence. This study tested whether PPP1CA (the catalytic subunit of PP1alpha), recently identified as contributing to Ras-induced senescence, might be this second signal. PPP1CA is induced by Ras; its inactivation inhibits Ras-induced senescence, presumably by inhibiting pRb dephosphorylation. Finally, PPP1CA seems to strongly co-localize with pRb only during senescence. CONCLUSIONS: The levels of p53 activation do not determine the outcome of the response. Rather, p53 activity seems to act as a necessary but not sufficient condition for senescence to arise. Maintaining cells in the arrested state for long periods does not switch reversible arrest to cellular senescence. PPP1CA is induced by Ras; its inactivation inhibits Ras-induced senescence, presumably by inhibiting pRb dephosphorylation. Finally, PPP1CA seems to strongly co-localize with pRb only during senescence, suggesting that PP1alpha activation during senescence may be the second signal contributing to the irreversibility of the senescent phenotype.

Project description:Due to their ability to preferentially induce cell death in tumor cells, while sparing healthy cells, TNF-related apoptosis-inducing ligand (TRAIL) and agonistic anti-TRAIL-R1 or anti-TRAIL-R2-specific antibodies are under clinical investigations for cancer-treatment. However, TRAIL-Rs may also induce signaling pathways, which result in malignant progression. TRAIL receptors are transcriptionally upregulated via wild-type p53 following radio- or chemotherapy. Nevertheless, the impact of p53 status on the expression and signaling of TRAIL-Rs is not fully understood. Therefore, we analyzed side by side apoptotic and non-apoptotic signaling induced by TRAIL or the agonistic TRAIL-R-specific antibodies Mapatumumab (anti-TRAIL-R1) and Lexatumumab (anti-TRAIL-R2) in the two isogenic colon carcinoma cell lines HCT116 p53+/+ and p53-/-. We found that HCT116 p53+/+ cells were significantly more sensitive to TRAIL-R-triggering than p53-/- cells. Similarly, A549 lung cancer cells expressing wild-type p53 were more sensitive to TRAIL-R-mediated cell death than their derivatives with knockdown of p53. Our data demonstrate that the contribution of p53 in regulating TRAIL-R-induced apoptosis does not correlate to the levels of TRAIL-Rs at the plasma membrane, but rather to p53-mediated upregulation of Bax, favouring the mitochondrial amplification loop. Consistently, stronger caspase-9 and caspase-3 activation as well as PARP-cleavage was observed following TRAIL-R-triggering in HCT116 p53+/+ compared to HCT116 p53-/- cells. Interestingly, HCT116 p53+/+ cells showed also a more potent activation of non-canonical TRAIL-R-induced signal transduction pathways like JNK, p38 and ERK1/ERK2 than p53-/- cells. Likewise, these cells induced IL-8 expression in response to TRAIL, Mapatumumab or Lexatumumab significantly stronger than p53-/- cells. We obtained similar results in A549 cells with or without p53-knockdown and in the two isogenic colon cancer cell lines RKO p53+/+ and p53-/-. In both cellular systems, we could clearly demonstrate the potentiating effects of p53 on TRAIL-R-mediated IL-8 induction. In conclusion, we found that wild-type p53 increases TRAIL-R-mediated apoptosis but simultaneously augments non-apoptotic signaling.

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P53-mediated senescence impairs the apoptotic response to chemotherapy and clinical outcome in breast cancer.

Publications

p53-mediated senescence impairs the apoptotic response to chemotherapy and clinical outcome in breast cancer.

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