Abstract 177: Disruption of the MDM2-p53 interaction strongly potentiates p53-dependent apoptosis in cisplatin resistant human testicular carcinoma cells via the Fas/FasL pathway

Abstract

Abstract A major role for p53 in the response and execution of apoptosis after chemotherapy has been described for many cancers. Although testicular cancer (TC) often express high levels of p53 and almost no TP53 mutations are found, resistance to chemotherapy is still observed in a subgroup of TC patients. Therefore, the involvement of wild-type p53 in cisplatin sensitivity and resistance of human TC is not clear. In the present study, we demonstrate that in resistant human TC cells (Tera2-CP, Scha, 2102EP) p53 resides in a complex with murine double minute 2 (MDM2) even at higher cisplatin concentrations compared to cisplatin sensitive human TC cells (Tera2). Hyper-activation of the p53 pathway using the MDM2 antagonist Nutlin-3 in TC cells leads to nuclear localization of p53 and effective apoptosis induction as single agent. Targeting MDM2 with short interfering RNA extremely sensitizes TC cells in a similar way. The observed effects are dependent on the presence of wild-type p53, since mutant p53 expressing TC cells (NCCIT) or wild-type p53 suppressed TC cells are resistant to Nutlin-3. Specifically, we show that the Fas death receptor pathway, i.e. enhanced Fas expression (3-fold) and the induction of Fas/FasL interactions, plays an important role in MDM2 antagonist-induced apoptosis in TC cells as demonstrated by using FasL blocking antibodies and FasL small interfering RNA. Importantly, we have identified a similar mechanism in Hodgkin lymphoma cells (KM-H2 and L540) and acute myeloid leukaemia cells (MOLM-13), suggesting a common profile for Nutlin-3-induced apoptosis, which involves the Fas death receptor pathway. Finally, we combined nutlin-3 with cisplatin, which strongly sensitized TC cells, including cisplatin-resistant TC cells, to apoptosis via Fas pathway activation and reduced cell survival more than 8-fold. These results indicate that targeting the p53/MDM2 axis, in combination with standard treatment, appears to be a powerful strategy to pursue in cisplatin-resistant or -refractory testicular cancers. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 177. doi:10.1158/1538-7445.AM2011-177