OPN1SW and hepatocellular carcinoma: Interestingly, these BCP mutations also affect the overlapping coding sequence of the multifunctional HBx (hepatitis B virus regulatory protein X) protein, causing amino acid exchanges in HBx that lead to changes in transactivation activity of HBx, which might contribute to carcinogenesis and development of hepatocellular carcinoma in genotypes C [42] and D [43].