However, data from genome-wide genetic perturbation screensusing shRNA have revealed a selective requirement for PRMT5 activityin MTAP-deleted (MTAP-null) cancer cell lines.1−3 The accumulation of MTA caused by MTAP deletionin these cell lines partially inhibits PRMT5, rendering those cellsparticularly sensitive to additional PRMT5 inhibition. Here, MTAP is linked to cancer.