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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Pharmacol. | doi: 10.3389/fphar.2019.01167

Anti-cancer effect of 3, 3’-diindolylmethane on human hepatocellular carcinoma cells is enhanced by calcium ionophore: The role of cytosolic Ca2+ and p38 MAPK

Yuanyue Jiang1,  Yanfei Fang1, Yang Ye1, Xinming Xu2, Bingfang Wang2,  Jie Gu3,  Michael Aschner4, Jian Chen2 and  Rongzhu Lu3*
  • 1School of Medicine, Jiangsu University, China
  • 2First People's Hospital of Kunshan, China
  • 3Jiangsu University, China
  • 4Department of Molecular Pharmacology, Albert Einstein College of Medicine, United States

Purpose: 3,3′-Diindolylmethane(DIM), derived from indole-3-carbinol (I3C) in the Brassica species of cruciferous vegetables, has anticancer effects, but its exact underlying mechanism of action remains unclear. We explored the roles of cytosolic free calcium ([Ca2+]i) and p38 MAPK in the anti-cancer effects of DIM in human hepatocellular carcinoma cells.
Methods: Cell proliferation was measured with a Cell Counting Kit-8(CCK-8) and the clonogenic formation assay. Cell apoptosis was examined by flow cytometric analysis and Hoechst dye staining. Cleaved-caspase3, cleaved-PARP, Bax, total and phosphorylated p38MAPK were assayed by western blotting. [Ca2+]i was measured with Fluo-3/AM by fluorescence microscopy. A23187, a calcium ionophore, was used to increase [Ca2+]i levels.
Results: DIM inhibited cell proliferation in both SMMC-7721 and HepG2 cells in a concentration- and time-dependent manner. DIM also enhanced phosphorylation of p38 MAPK(p-p38), which was attenuated by SB203580 and the proliferation inhibition and apoptosis induction by DIM were also blunted. In addition, DIM increased [Ca2+]i in hepatocellular carcinoma cells, and this effects was inhibited by the calcium chelator, BAPTA/AM, resulting in reduced p-p38 MAPK activation and apoptosis in DIM-treated cells, though the proliferation inhibition by DIM was unchanged. However, The DIM-induced cell proliferation inhibition and apoptosis were significantly enhanced by A23187, a selective calcium ionophore, which was attributed to exaggerated p-p38 MAPK.
Conclusions: Calcium ionophore enhanced DIM-induced anti-cancer effects in hepatocellular carcinoma cells, secondary to [Ca2+]i-dependent activation of p38 MAPK. Treatment with a combination of DIM and calcium ionophore may offer a new approach to enhance the chemotherapeutic efficacy in liver cancer.

Keywords: 3,3′-Diindolylmethane (DIM), cytosolic calcium, p38 MAPK, Hepatocellular Carcinoma cells (HCC cells), Apoptosis, proliferation, Calcium ionophore

Received: 22 Mar 2019; Accepted: 11 Sep 2019.

Copyright: © 2019 Jiang, Fang, Ye, Xu, Wang, Gu, Aschner, Chen and Lu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Rongzhu Lu, Jiangsu University, Zhenjiang, 212013, Jiangsu Province, China, lurz@ujs.edu.cn