PTGS2 and hepatocellular carcinoma: These results are in line with other data recently collected in a model of ovarian carcinoma cells (Denkert et al, 2003) and in a model of human hepatocellular carcinoma cells (Park et al, 2005) based on siRNA-mediated COX-2 downregulation, suggesting that COX-2 itself is not decisively involved in the proliferation of human cancer cells as well.