BIOL-04. FROM MSWI/SNF’S ROLES IN PROTEIN SYNTHESIS TO NEW THERAPEUTIC OPPORTUNITIES

Abstract

Abstract The chromatin remodeler complexes mammalian SWI/SNF (SWItch/Sucrose Non-Fermentable) are altered in more than 40% of cancers and are involved in therapeutic resistance. In children, SMARCB1 is mutated in 95% of rhabdoid tumors, and the remaining 5% present mutations in SMARCA4. These tumors are typically identified in children younger than three years old and have a very poor prognosis with a survival under one year following diagnosis. SMARCB1 expression is also lost in more than 90% of epithelial sarcomas, a rare and aggressive tumor affecting young adults, and in 50% of pediatric chordomas. Additional mSWI/SNF subunits are also highly mutated in childhood cancers such as ARID1A and ARID1B in neuroblastomas, the most common solid tumor in children, and the ARID subunits and SMARCA4 in medulloblastomas, the most common brain cancer in children. To date, mSWI/SNF roles in normal and cancer cells are still largely undetermined and focus on nuclear functions. However, our assessment of genetic dependencies and drug sensitivity screens revealed that cancer cells mutated for mSWI/SNF are genetically dependent and exclusively sensitive to translation factors and translation pathway inhibitors. We demonstrate that mSWI/SNF complexes are extensively localized in the cytoplasm and that they interact with the translation initiation machinery. Furthermore, short-term inhibition, depletion and cancer mutations of specific subunits alter protein synthesis and increase sensitivity to translation inhibitors. Most mutations in these complexes being considered loss of function, these results suggest a potential therapeutic opportunity for diseases presenting mutations in these complexes. In conclusion, our work demonstrates the chromatin remodelers mSWI/SNF have direct roles in translation that will not only be relevant for the molecular understanding of cancer but also lead to new therapeutic opportunities.