Metformin inhibits tumorigenesis in HBV-induced hepatocellular carcinoma by suppressing HULC overexpression caused by HBX

We aimed to understand whether metformin imposes the inhibitory effect on the HBV-associated tumorigenesis by regulating the HULC and its downstream signaling pathway. Luciferase assay, RT-PCR, and Western-blot, MTT and flow cytometry analysis were performed to understand and the mechanism, by which metformin enhance the inhibitory effect on the HBV-associated tumorigenesis by regulating the HULC and its downstream signaling pathway. HBX promoted viability of three types of cell lines, while metformin inhibited apoptosis of above two cells. ZEB1 was a direct downstream of miR-200a, which was further confirmed that miR-200a reduced luciferase activity of wild-type but not mutant ZEB1 3UTR, and HULC was bound to region of miR-200a-3p using alignment prediction, but can't affect ZEB1 level. HULC transcription ability, HULC, ZEB1, and p18 levels were much higher in cell treated with HBX, while notably lower in cell treated with metformin, furthermore miR-200a level in cell showed an opposite trend as HULC, ZEB1, and p18 levels. HULC siRNA and miR-200a had no effect on HULC transcription ability, but decreased HULC, ZEB1, and p18 levels, and increased miR-200a expression. HBV (+) HCC +metformin exhibited a higher survival ratio and a lower recurrence rates than HBV (+) HCC group, HBV (-) HCC displayed an even higher survival ratio and an even lower recurrence rates than HBV (+) HCC+metformin groups. This study indicated that metformin imposed inhibitory effect on the HBV-associated HCC by negatively regulating the HULC/p18/miR-200a/ZEB1 signaling pathway.