Original Article
Copyright ©2014 Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jul 14, 2014; 20(26): 8572-8582
Published online Jul 14, 2014. doi: 10.3748/wjg.v20.i26.8572
Zinc protoporphyrin IX enhances chemotherapeutic response of hepatoma cells to cisplatin
Yang-Sui Liu, Huan-Song Li, Dun-Feng Qi, Jun Zhang, Xin-Chun Jiang, Kui Shi, Xiao-Jun Zhang, Xin-Hui Zhang
Yang-Sui Liu, Huan-Song Li, Dun-Feng Qi, Jun Zhang, Xin-Chun Jiang, Kui Shi, Xiao-Jun Zhang, Xin-Hui Zhang, The Central Hospital of Xuzhou City, Xuzhou Hospital Affiliated to Medical College of Southeast University, Xuzhou 221009, Jiangsu Province, China
Author contributions: Liu YS and Zhang XH performed the majority of experiments; Li HS, Zhang J and Zhang XJ provided vital reagents and analytical tools and were also involved in revising the manuscript; Qi DF, Jiang XC and Shi K analyzed the data; Liu YS, Zhang XJ and Zhang XH designed the study and wrote the manuscript.
Supported by Xuzhou City Health Bureau Project, China, No. XZZD1128; and Xuzhou City Municipal Science and Technology Bureau Project, China, No. XWJ2011040
Correspondence to: Xin-Hui Zhang, MD, The Central Hospital of Xuzhou City, Xuzhou Hospital Affiliated to Medical College of Southeast University, Jiefang Rd, Xuzhou 221009, Jiangsu Province, China. 88liuyin888@163.com
Telephone: +86-516-83956131 Fax: +86-516-83956131
Received: November 13, 2013
Revised: January 14, 2014
Accepted: April 2, 2014
Published online: July 14, 2014
Processing time: 242 Days and 18.4 Hours
Abstract

AIM: To investigate the effect of zinc protoporphyrin IX on the response of hepatoma cells to cisplatin and the possible mechanism involved.

METHODS: Cytotoxicity was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Apoptosis was determined by a flow cytometric assay. Western blotting was used to measure protein expression. Heme oxygenase (HO)-1 activity was measured by determining the level of bilirubin generated in isolated microsomes. Reactive oxygen species (ROS) production was monitored by flow cytometry. Caspase-3 activity was measured with a colorimetric assay kit. Mice were inoculated with 1 × 107 tumor cells subcutaneously into the right flanks. All mice were sacrificed 6 wk after the first treatment and tumors were weighed and measured.

RESULTS: Overexpression of HO-1 in HepG2 cell line was associated with increased chemoresistance to cis-diaminedichloroplatinum (cisplatin; CDDP) compared to other cell lines in vitro. Inhibition of HO-1 expression or activity by zinc protoporphyrin IX (ZnPP IX) markedly augmented CDDP-mediated cytotoxicity towards all liver cancer cell lines in vitro and in vivo. In contrast, induction of HO-1 with hemin increased resistance of tumor cells to CDDP-mediated cytotoxicity in vitro and in vivo. Furthermore, cells treated with ZnPP IX plus CDDP exhibited marked production of intracellular ROS and caspase-3 activity, which paralleled the incidence of cell apoptosis, whereas hemin decreased cellular ROS and caspase-3 activity induced by CDDP.

CONCLUSION: ZnPP IX increases cellular sensitivity and susceptibility of liver cancer cell lines to CDDP and this may represent a mechanism of increasing ROS.

Keywords: Zinc protoporphyrin IX; Heme oxygenase-1; Liver cancer cell lines; Cisplatin; Chemotherapy

Core tip: Overexpression of heme oxygenase (HO)-1 in HepG2 cell line was associated with increased chemoresistance to cis-diaminedichloroplatinum (cisplatin; CDDP) compared to other cell lines. Inhibition of HO-1 expression by zinc protoporphyrin IX (ZnPP IX) markedly augmented CDDP-mediated cytotoxicity towards other hepatoma cells. Induction of HO-1 with hemin increased resistance of tumor cells to CDDP-mediated cytotoxicity. Furthermore, cells treated with ZnPP IX plus CDDP exhibited marked production of intracellular reactive oxygen species (ROS) and caspase-3 activity, whereas hemin decreased cellular ROS and caspase-3 activity induced by CDDP. Therefore, administration of HO-1 inhibitors may evolve into a new liver cancer treatment strategy.