CYP3A4 and hepatocellular carcinoma: In contrast, reduced expression of the phase 1 sorafenib metabolizing enzyme CYP3A4 (porcine homologue CYP3A39) [18, 19] and increased expression of CRB1, which is involved in doxorubicin metabolism [20] were observed in Oncopig cell lines compared to human HCC cell lines (Figure 2A).