Remodeling the translatome in N-myc mediated medulloblastoma and its therapeutic implications

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Medulloblastoma is the most common malignant pediatric brain tumor. After surgery, radiation and chemotherapy, five-year survival is 60-70% overall. Survivors show severe physical and cognitive disabilities, often unable to live independently. Medulloblastoma exists in four distinct molecular subgroups (WNT, SHH, Group3, Group 4). An incurable subgroup of SHH driven tumors show amplification of the MYCN transcription factor. How can we target N-myc in medulloblastoma? N-myc’s ability to regulate protein synthesis is tied both to its oncogenic potential and to interactions with the mTOR serine-threonine kinase. We hypothesize that N- myc hijacks the translational machinery regulated by the mTOR serine threonine kinase to drive transformation; and that targeting translation control represents a therapeutic strategy for N-myc driven cancers. Employing ribosome profiling technology, we surprisingly found that in addition to roles as a global regulator of protein synthesis, N-myc interacts with mTOR to regulate translation of 13 mRNAs belonging to the folding machinery, functionally important for N-myc driven medulloblastoma. The mechanisms by which N-myc directs the translation of these specific subsets of mRNAs to drive tumorigenesis and whether these potential vulnerabilities can be leveraged to develop targeted therapies remain outstanding questions. In this proposal, we will mechanistically dissect how N-myc hijacks the translational machinery for its oncogenic activity. Using novel genetic approaches, we will separately evaluate the importance of eIF4E and eIF4A in our N-myc driven genetically engineered mouse (GEM) models. We will also test new clinical drugs against eIF4A and eIF4E, analyzing GEM models, and patient derived orthotopic xenografts. Successful completion of these aims will delineate how N-myc interacts with mTOR to regulate key subsets of translational targets, and elucidates druggable mechanisms in N-myc driven medulloblastoma.