Abstract 5049: Targeting the Notch and mTOR pathways in diffuse intrinsic pontine glioma.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Diffuse intrinsic pontine glioma (DIPG) is a universally fatal pediatric brain tumor which is known to have frequent alteration of mTOR signaling. Analysis of DIPG tissue obtained through the Mid-Atlantic DIPG Consortium (MADC) also shows high level activation of Notch pathway effectors HES4 and HES5. We have established JHH DIPG1, a human DIPG xenograft and neurosphere cell line from a rapid autopsy specimen obtained through the MADC. Notch 1 and 3 and Notch downstream effectors, Hes1, Hes5 and Hey1, are highly expressed in JHH DIPG1 and a second DIPG line, SU DIPG1. These DIPG cell lines also express high level phospho-S6 and phospho-AKT 473, indicating activation of TORC1 and TORC2. Notch and mTOR pathway signaling is equal to or exceeding that observed in glioblastoma neurosphere cell lines. Notch targeting using a gamma-secretase inhibitor leads to a dose-dependent reduction in cell proliferation of up to 30% (p=0.05) as well as inhibition of phospho-AKT 473, suggesting that inhibition of the NOTCH pathway targets TORC2 complexes. BrdU incorporation also showed that treatment of DIPG cell lines with a TORC1 inhibitor also has up to a 60% attenuation of cell proliferation (p<0.005) in treated DIPG cells compared to non-treated cells and a dose-dependent reduction in phospho-S6, with concomitant upregulation of phospho-AKT 473 indicating TORC2 activation. Dual TORC1 and TORC2 inhibition by combining a rapalog and a gamma-secretase inhibitor may prove to be synergistic in DIPG. Simultaneous treatment with a rapalog and gamma-secretase inhibition suppresses TORC1 and TORC2, as measured by western blot. We are currently investigating the possible mechanism of action of these drugs in DIPG. Our laboratory is investigating additional metabolic inhibitors that can be used with TORC1 and TORC2 inhibitors to further improve treatment options for DIPG. We are currently exploring the role of the Notch and mTOR pathways in DIPG in pre-clinical studies in mice, with the goal of moving targeted inhibitors into clinical trials for these currently highly lethal tumors. Citation Format: Marianne Hutt, Wendy Goldstein, Javad Nazarian, Antoinette Price, Kah Jing Lim, Katherine Warren, Howard Chang, Charles Eberhart, Eric Raabe. Targeting the Notch and mTOR pathways in diffuse intrinsic pontine glioma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5049. doi:10.1158/1538-7445.AM2013-5049