E2F1 and hepatocellular carcinoma: Moreover, celecoxib was found to inhibit the growth of hepatocellular carcinoma cells by activating retinoblastoma protein (pRb) through its hypophosphorylation, thus repressing the DP1/E2F1 complex, and inducing apoptosis through the activation of caspase-3 and caspase-9 [23].