To determine the effects of PDCD4 knockdown on cell cycle regulators in hepatoma cells, we investigated the expression of retinoblastoma protein (Rb), phospho-Rb (p-Rb) and its controller cyclin-dependent kinases (CDKs) by Western blotting of the p2 and k603 PDCD4-specific siRNAs-treated cells. The gene discussed is PDCD4; the disease is hepatocellular carcinoma.