The present invention provides diagnostic and therapeutic methods for cancer. The invention provides methods of determining whether a patient having a cancer is likely to respond to treatment comprising an inhibitor of H3K27 methylation, methods of predicting responsiveness of a patient having a cancer to treatment comprising one or more inhibitors of H3K27 methylation, methods of selecting a therapy for a patient having a cancer, and methods of treating cancer based on expression levels of biomarkers of the invention (e.g., the expression level of SIV1ARCA2 or the occupancy level of H3K27 at a SMARCA2 promoter).
