Abstract 4260: Sunitinib treatment induces Notch expression and activation in renal carcinoma cell lines

Abstract Introduction. Notch signaling is an evolutionary conserved pathway that plays a central role in stem cell biology, tumor formation, angiogenesis and cell fate decisions. Currently there is not any clear view as to whether Notch plays an oncogenic role in renal cell cancer (RCC). Notch-1 is activated after cytotoxic stimuli and may induce mTor pathway activation, leading to increased cell survival. We have investigated the role of Notch expression and activation in RCC cell lines in response to sunitinib treatment and the role of Notch in the activation of the mTor pathway. We elaborated three cell lines with a different VHL and PTEN mutation status: Caki-1 cells (VHL-wt, PTEN-wt), Caki-2 (VHL-mut, PTEN-wt) and 786-O (VHL-mut, PTEN-mut). Results: When Caki-1 and Caki-2 cells were exposed to sunitinib there was a marked upregulation in the expression of the Notch-1 mRNA and the target transcription factors RUNX1, RBPJ and HES1. The PI3K – mTor – S6K pathway was aslo upregulated. This upregulation was reversed when cells were pre-treated with a gamma-secretase inhibitor. However, both gamma secretase inhibitors and everolimus (an m-Tor inhibitor) had an antagonistic effect when combined with sunitinib (Combination Index >> 1.0). On the other hand, PTEN-mutant 786-O cells have a dysregulated mTor pathway and are more sensitive to inhinition of the m-Tor with everolimus. Sunitinib exposure did not result in further increase of the PI3K-mTor-S6K activation. Interestingly, combination of sunitinib with everolimus was synergistic in 786-O. Conclusions: VHL-wt and VHL-mutant RCC cells treated with sunitinib activate the Notch pathway. There are reports that Notch plays a tumor suppressor role in RCC and our results are on concert with that. Furthermore, Notch seems to regulate m-Tor pathway activation in cells with a wild-type PTEN. 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 4260. doi:10.1158/1538-7445.AM2011-4260