CYP2E1 deficit mediates cholic acid-induced malignant growth in hepatocellular carcinoma cells

<title>Abstract</title> Background An increased serum cholic acid (CA) is concurrently appeared with a decreased CYP2E1 expression in hepatocellular carcinoma (HCC). However, whether and how CA may be involved in promoting hepatocarcinogenesis has not been elucidated. This study was aimed to investigate the role of CYP2E1 on CA-induced HCC cell growth and its underlying mechanism. Methods Our proteomic analysis of liver tumor tissues from DEN-induced male SD rats treated with CA administration revealed that CA downregulated CYP2E1 level. The proliferative ability of CA-treated HCC cells was examined by colony formation assays. Autophagic flux was detected by immunofluorescence and confocal microscopy. The protein levels of CYP2E1, mTOR, AKT, p62 and LC3Ⅱ were detected by Immunoblotting. The effect of CYP2E1 on CA-induced hepatocellular carcinogenesis was explored in vivo by establishing a xenograft tumor model in nude mice. We also investigated the clinical value of CYP2E1 in HCC patients. Results CA increased the clonogenicity of HCC cells and promoted the growth of xenograft tumors with a simultaneous reduction of CYP2E1 expression. Further studies revealed that both in vitro and in vivo, upregulating CYP2E1 could effectively inhibit cell growth of HCC with a blockage of autophagic flux, downregulation of AKT phosphorylation and upregulation of mTOR phosphorylation. CYP2E1 was involved in CA-activated autophagy through the AKT/mTOR signaling, which promoted CA-stimulated HCC cell growth. Finally, a decreased CYP2E1 expression was observed in the tumor tissues of HCC patients and the CYP2E1 level in tumor was negatively correlated with the serum level of total bile acids (TBA) and gamma-glutamyltransferase (GGT). Conclusions CYP2E1 deficit contributes to CA-induced HCC development with the mechanisms involving regulation of autophagy, thus CYP2E1 may serve as a potential target for HCC drug development.