This is to be expected, since apart from disparities in Raf/MEK/ERK activity [23] and in COX-2 expression levels [21], the two HCC cell lines also display other significant differences, such as alterations in β-catenin, K-Ras, p16ink, p53, p21, FANCD2 and other genes. This evidence concerns the gene PTGS2 and hepatocellular carcinoma.