NF-κB is also a transcriptional regulator of cyclooxygenase-2 (COX-2) (63), whose activity showed a strong correlation with P-gp expression in hepatocellular carcinoma (64) and colorectal cancer (65), and with multidrug resistance protein 4 (MRP4) in lung cancer (66). This evidence concerns the gene PTGS2 and hepatocellular carcinoma.