As predicted, and consistent with the observation that most of the liver tumor cells expressed GFP and the Cdk9 shRNA (Fig. 3B), Dox treatment reduced the expression of CDK9 and pSer2 in HCC cells (Fig. 3 B and C and SI Appendix, Fig. S3 B–D), which correlated with a robust reduction of HCC tumor burden as gauged by liver weight after 2 wk on Dox (Fig. 3D and SI Appendix, Fig. S3A). Here, CDK9 is linked to hepatocellular carcinoma.