Unlike the compounds from which they derived, meriolins exerted anti-cancer effects in vivo and showed pro-apoptotic activity in vitro selectively inhibiting CDKs, including the CDK9-dependent phosphorylation RNA Pol II on Ser2, thus leading to consequent down-regulation of MCL1 and tumor cell death (Bettayeb et al., 2007). This evidence concerns the gene CDK9 and cancer.