Bicyclol induces cell cycle arrest and autophagy in HepG2 human hepatocellular carcinoma cells through the PI3K/AKT and Ras/Raf/MEK/ERK pathways.

Yu Wang,Hao Nie,Xin Zhao,Yong Qin,Xingguo Gong

doi:10.1186/s12885-016-2767-2

Yu Wang, Hao Nie + Show 3 more

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https://doi.org/10.1186/s12885-016-2767-2

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Journal: BMC cancer	Publication Date: Sep 21, 2016
Citations: 100	License type: cc-by

Affiliation: Zhejiang University

Abstract

BackgroundBicyclol, a novel synthetic antihepatitis drug, is widely known to protect against liver injury. However, few reports have focused on the possible effect of bicyclol on anti-proliferation and autophagy induction in cancer cells, particularly hepatocellular carcinoma cells.MethodsIn this study, we investigated the antitumor efficacy of Bicyclol in HepG2 cells and the mechanism of cell growth inhibition. Cell proliferation was analyzed by MTT assay, and the cell cycle and apoptosis were assessed by flow cytometry. And we transfected the cells with the GFP-RFP-LC3 vector to detect the autophagy flux in the cells. Mechanisms of bicyclol-induced cell growth inhibition were probed by western blot analysis.ResultsBicyclol effectively inhibited HepG2 cell proliferation in a dose- and time-dependent manner. In addition, we found that bicyclol inhibited cell cycle progression at G1 phase and induced autophagy in HepG2 cells, which implied that the significant decrease in cell proliferation was mainly induced by autophagy and inhibition of cell proliferation. Furthermore, western blot showed that bicyclol inhibited phosphorylation of Akt and ERK, down-regulated the expressions of cyclin D1, cyclin E2, CDK2, CDK4, p-Rb and p-mTOR. Moreover, AKT or ERK knockdown by siRNA enhanced bicyclol-induced autophagy and inhibition of cell proliferation.ConclusionThese results suggest that bicyclol has potent anti-proliferative activity against malignant human hepatoma cells via modulation of the PI3K/AKT pathway and the Ras/Raf/MEK/ERK pathway, and indicate that bicyclol is a potential liver cancer drug worthy of further research and development.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2767-2) contains supplementary material, which is available to authorized users.

Highlights

Bicyclol, a novel synthetic antihepatitis drug, is widely known to protect against liver injury
ERK1/2 phosphorylation at Thr202 and Tyr 204 was inhibited, while the total protein level was constant. These results suggested that the synergy between the Phosphatidylinositide 3-kinases (PI3K)/v-akt murine thymoma viral oncogene homolog (AKT) pathway and the Ras/Raf/Mitogen/ extracellular signal-regulated kinase (MEK)/Extracellular signal-regulated kinases (ERK) pathway played an important role in the bicyclol-induced antiproliferative effect
We found that bicyclol induces cell cycle arrest at G1 phase and autophagy at more than 100uM, and we identified the molecular mechanism, showing that bicyclol suppresses both the PI3K/ AKT pathway and the Ras/Raf/MEK/ERK pathway and downregulates cyclin D, cyclin E and Mammalian target of rapamycin (mTOR), leading to Retinoblastoma protein (Rb) dephosphorylation and the conversion of LC3I to LC3II

Summary

Introduction

A novel synthetic antihepatitis drug, is widely known to protect against liver injury. Despite extensive research into treatments of liver cancer, such as chemotherapy, hepatectomy, liver transplantation, microspheres, and immunotherapy, survival rates are 3–5 % in cancer registries in developed countries, Bicyclol (4,4’-dimethoxy-5,6,5,’6’-Bis(dimethylene-dioxy)2-hydroxymethyl-2’-methoxy carbonyl biphenyl, Fig. 1a [5]) is a new synthetic antihepatitis drug. It has been widely used in the clinic to treat patients with chronic hepatitis B viral infections [6]. Bicyclol can improve liver function and partially inhibits hepatitis B virus replication in the clinic [10]

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