CDK9 and cancer: Finally, P-TEFb-dependent Pol II pause release is frequently dysregulated in cancers, particularly in those addicted to c-MYC and translocations of mixed-lineage leukemia gene (Dawson et al., 2011, Delmore et al., 2011, Liang et al., 2018), spurring interest in the development of highly specific CDK9 inhibitors for clinical use (Lu et al., 2015, Olson et al., 2018).