Background & Aims
Cholestasis contributes to hepatocellular injury and promotes liver carcinogenesis. We created a mouse model of chronic cholestasis to study its effects on progression of cholangiocarcinoma and the oncogenes involved.
Methods
To induce chronic cholestasis, Balb/c mice were given 2 weekly intraperitoneal injections of diethylnitrosamine (DEN); 2 weeks later, some mice also received left and median bile duct ligation (LMBDL), and then 1 week later, were fed DEN, in corn oil, weekly by oral gavage (DLD). Liver samples were analyzed by immunohistochemical and biochemical assays; expression of Mnt and c-Myc were reduced by injection of small inhibitor RNAs.
Results
Chronic cholestasis was induced by DLD and accelerated progression of cholangiocarcinoma, compared with mice given only DEN. Cystic hyperplasias, cystic atypical hyperplasias, cholangiomas, and cholangiocarcinoma developed in the DLD group at weeks 8, 12, 16 and 28, respectively. LMBDL repressed expression of microRNA (miR)-34a and Let-7a, upregulating Lin-28B, HIF-1α, HIF-2α, and miR-210. Upregulation of Lin-28B might inhibit let-7a, which is associated with development of cystic hyperplasias, cystic atypical hyperplasias, cholangiomas, and cholangiocarcinoma. Knockdown of c-Myc reduced progression of cholangiocarcinoma whereas knockdown of Mnt accelerated its progression. Downregulation of miR-34a expression might upregulate c-Myc. The upregulation of miR-210 via HIF-2α was involved in downregulation of Mnt. Activation of the miR-34a–c-Myc and HIF-2α–miR-210–Mnt pathways caused c-Myc to bind the E-box element of cyclin D1, instead of Mnt, resulting in cyclin D1 upregulation.
Conclusion
DLD induction of chronic cholestasis accelerated progression of cholangiocarcinoma, which is mediated by downregulation of miR-34a, upregulation miR-210, and replacement of Mnt by c-Myc in binding to cyclin D1.
