Abstract B78: Targeting the translational apparatus in MYCN-driven medulloblastoma

Amplification of MYCN is associated with high-risk SHH-driven and group 4 medulloblastoma, while mis-expression and amplification of MYC is associated with aggressive group 3 tumors. The biology of these tumors, particularly the group 3/4 tumors, is poorly understood, with no effective targeted therapies. We have recently developed a model of group 4 medulloblastoma in which high levels of mutationally-stabilized MYCN protein drive oncogenesis. We have shown in other tumor types that modulation of the translational apparatus downstream of the mammalian target of rapamycin (mTOR) is required for MYC-driven oncogenesis and that there is a synergistic relationship between MYC and the mTOR axis to promote tumor formation. mTOR signals through two primary outputs, rpS6 kinase (S6K) and the translation initiation factor eIF4E. A new class of clinical mTOR active site inhibitors disrupts signaling through both effectors, whereas the allosteric binder rapamycin disrupts only S6K. We describe genetic and therapeutic studies aimed at distinguishing the effects of S6K and eIF4E in both tumor formation and in therapy. These mechanistically distinct activities have enormous therapeutic implications, as in our medulloblastoma model, active site inhibitors of mTOR, but not rapamycin, demonstrate efficacy. Taken together, this supports the idea that signaling through S6K is dispensable, whereas eIF4E is required for MYC-driven oncogenesis. Citation Format: Justin G. Meyerowitz, W. Clay Gustafson, Erin Nekritz, Fredrik Swartling, Kevan M. Shokat, Davide Ruggero, William A. Weiss. Targeting the translational apparatus in MYCN-driven medulloblastoma. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr B78.