Ashley Lira-Rivera

Background/Objectives: SCCOHT is an aggressive and often fatal cancer that belongs to the ~20% of cancers defined by mutations to subunits of the SWI/SNF chromatin remodeling complex. In SCCOHT, mutations to the SMARCA4 gene, which encodes the SWI/SNF ATPase BRG1, are sufficient to impair SWI/SNF function. This single genetic lesion leads to a cascade of events that promote tumorigenesis, some of which may involve the intersection of SWI/SNF with oncogenic pathways such as those regulated by the MYC oncogene. In SCCOHT tumors and other cancers marked by SWI/SNF subunit mutation, MYC target genes are recurrently activated, pointing to a relationship between SWI/SNF and MYC that has yet to be fully explored. Methods: In this study, we investigate the contribution of MYC to SCCOHT biology by performing a combination of chromatin binding and transcriptome assays in genetically engineered SCCOHT cell lines, with subsequent validation using patient tumor expression data. Results: We find that MYC binds to thousands of active promoters in the BIN-67 SCCOHT cell line and that the depletion of MYC results in a broad range of gene expression changes with a notable effect on the expression of genes related to DNA repair. We uncover an MYC-regulated DNA repair gene expression program in BIN-67 cells that is antagonized by BRG1 reintroduction. Finally, we identify a DNA repair gene signature that is upregulated in SCCOHT tumors and in tumors defined by loss of the SWI/SNF subunit SNF5. Conclusions: Collectively, these data implicate MYC as a robust regulator of DNA repair gene expression in SCCOHT and lay a foundation for future studies focused on interrogating the relationship between BRG1 and MYC.