CDK9 and cancer: CDK9 is important for RNAPII-mediated transcription elongation, and the expression of specific gene sets has been shown to be highly sensitive to CDK9 inhibition in cancer cells, including genes encoding mRNA transcripts with high turnover rates for anti-apoptotic and pro-survival proteins (e.g., MYC, and MCL1), highly expressed genes, fusion chimeras (e.g., MYC, MLL1-AF9), and genes associated with super-enhancers [6].