CDK4 and hepatocellular carcinoma: Less profound, statistically not significant effects were observed for Cdk4 and Pcna. For comparison, exposure of human hepatoma cells HuH7 to WY14,643 induced only PCNA. While transfection of PPARα-wt had no augmenting effect on any proliferative gene, PPARα-tr overexpression significantly inhibited MYC expression and prevented induction of PCNA (Fig. 5a bottom).