Abstract 3099: Dual targeting of mTOR and Notch disrupts growth and promotes apoptosis in diffuse intrinsic pontine glioma

Abstract

Abstract Diffuse intrinsic pontine gliomass (DIPGss) account for 10% of pediatric brain tumors and have a universally poor prognosis. Our laboratory has shown that targeting the NOTCH pathway in glioblastoma (GBM) with gamma secretase inhibitors (GSI), inhibits the growth and viability of tumor neurospheres. Primary DIPG as well as DIPG cell lines express have very high levels of NOTCH activity as measured by western blot and qPCR assays. AKT amplification is observed in primary DIPG, and TORC1/TORC2 activation occurs in DIPG cell lines as measured by western blot. The mTOR and NOTCH pathways are known to interact and alter cancer stem cell growth, stemness, and metabolism. We hypothesized that dual targeting of NOTCH and mTOR in DIPG would lead to decreased proliferation and increased apoptosis compared to targeting either pathway in isolation. In established DIPG cell lines, we observed that GSI treatment decreases NOTCH activity in a dose dependent manner as evidenced by decreased expression of NOTCH targets expression of Hes1 and Hey1 via as measured by western blot and qPCR assays. We also observed a dose-dependent reduction in DIPG proliferation and growth after gamma-secretase inhibition as measured by BrdU (Day 7, DMSO to 5 uM MRK003 had p value <0.05) and MTT assays (Day 5 and Day 7, DMSO to 2 uM and 5 uM MRK003 p value <0.05). However, inhibition of growth and increased apoptosis were not complete. We observed a similar decrease in proliferation and increase in apoptosis using the dual TORC1/TORC2 inhibitor PPT242. Combination therapy with MRK003 and PP242 led to significantly increased apoptosis compared to either treatment alone (cell cycle Sub-G1: DMSO 13.2% vs 1000nM PP242-5uM M003 28.9%). This data suggest that dual targeting of the mTOR and NOTCH pathways with GSI will decrease DIPG cell growth and proliferation, increase cell death, and reduce tumorigenicity. Citation Format: Isabella C. Taylor, Marianne Hutt-Cabezas, Melanie Weingart, Kathy Warren, Howard Chang, Javad Nazarian, Charles G. Eberhart, Eric H. Raabe. Dual targeting of mTOR and Notch disrupts growth and promotes apoptosis in diffuse intrinsic pontine glioma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3099. doi:10.1158/1538-7445.AM2014-3099