Original Article
Copyright ©2013 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Gastroenterol. Apr 28, 2013; 19(16): 2481-2491
Published online Apr 28, 2013. doi: 10.3748/wjg.v19.i16.2481
Emodin regulating excision repair cross-complementation group 1 through fibroblast growth factor receptor 2 signaling
Gang Chen, Hong Qiu, Shan-Dong Ke, Shao-Ming Hu, Shi-Ying Yu, Sheng-Quan Zou
Gang Chen, Shan-Dong Ke, Shao-Ming Hu, Integration Traditional Chinese Medicine and Western Medicine Department, TongJi Hospital, Huazhong University of Science and Technology, Wuhan 430030, Hubei Province, China
Hong Qiu, Shi-Ying Yu, Department of Oncology, TongJi Hospital, Huazhong University of Science and Technology, Wuhan 430030, Hubei Province, China
Sheng-Quan Zou, Department of Surgery, TongJi Hospital, Huazhong University of Science and Technology, Wuhan 430030, Hubei Province, China
Author contributions: Chen G and Ke SD performed the majority of experiments; Qiu H and Zou SQ provided financial support for this work; Chen G, Qiu H, Hu SM and Yu SY designed the study and wrote the manuscript.
Supported by National Natural Sciences Foundation of China, No. 81001067; the Ministry of Science and Technology International Cooperation Project, No. 2010DFA31870; and the AstraZeneca Special Research Foundation for Targeted Therapy of the Wu Jieping Medical Foundation, No. 320.6700.09068
Correspondence to: Dr. Shao-Ming Hu, Integration Traditional Chinese Medicine and Western Medicine Department, TongJi Hospital, Huazhong University of Science and Technology, 1095 Jiefang Avenue, Qiaokou District, Wuhan 430030, Hubei Province, China. smhu@tjh.tjmu.edu.cn
Telephone: +86-27-83663532 Fax: +86-27-83663445
Received: October 3, 2012
Revised: March 15, 2013
Accepted: March 21, 2013
Published online: April 28, 2013
Processing time: 210 Days and 11.3 Hours
Abstract

AIM: To investigate the molecular mechanisms underlying the reversal effect of emodin on platinum resistance in hepatocellular carcinoma.

METHODS: After the addition of 10 μmol/L emodin to HepG2/oxaliplatin (OXA) cells, the inhibition rate (IR), 50% inhibitory concentration (IC50) and reversal index (IC50 in experimental group/IC50 in control group) were calculated. For HepG2, HepG2/OXA, HepG2/OXA/T, each cell line was divided into a control group, OXA group, OXA + fibroblast growth factor 7 (FGF7) group and OXA + emodin group, and the final concentrations of FGF7, emodin and OXA in each group were 5 ng/mL, 10 μg/mL and 10 μmol/L, respectively. Single-cell gel electrophoresis was conducted to detect DNA damage, and the fibroblast growth factor receptor 2 (FGFR2), phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2) and excision repair cross-complementing gene 1 (ERCC1) protein expression levels in each group were examined by Western blotting.

RESULTS: Compared with the IC50 of 120.78 μmol/L in HepG2/OXA cells, the IC50 decreased to 39.65 μmol/L after treatment with 10 μmol/L emodin; thus, the reversal index was 3.05. Compared with the control group, the tail length and Olive tail length in the OXA group, OXA + FGF7 group and OXA + emodin group were significantly increased, and the differences were statistically significant (P < 0.01). The tail length and Olive tail length were lower in the OXA + FGF7 group than in the OXA group, and this difference was also statistically significant. Compared with the OXA + FGF7 group, the tail extent, the Olive tail moment and the percentage of tail DNA were significantly increased in the OXA + emodin group, and these differences were statistically significant (P < 0.01). In comparison with its parental cell line HepG2, the HepG2/OXA cells demonstrated significantly increased FGFR2, p-ERK1/2 and ERCC1 expression levels, whereas the expression of all three molecules was significantly inhibited in HepG2/OXA/T cells, in which FGFR2 was silenced by FGFR2 shRNA. In the examined HepG2 cells, the FGFR2, p-ERK1/2 and ERCC1 expression levels demonstrated increasing trends in the OXA group and OXA + FGF7 group. Compared with the OXA group and OXA + FGF7 group, the FGFR2, p-ERK1/2, and ERCC1 expression levels were significantly lower in the OXA + emodin group, and these differences were statistically significant. In the HepG2/OXA/T cell line that was transfected with FGFR2 shRNA, the FGFR2, p-ERK1/2 and ERCC1 expression levels were significantly inhibited, but there were no significant differences in these expression levels among the OXA, OXA + FGF7 and OXA + emodin groups.

CONCLUSION: Emodin markedly reversed OXA resistance by enhancing OXA DNA damage in HepG2/OXA cells, and the molecular mechanism was related to the inhibitory effect on ERCC1 expression being mediated by the FGFR2/ERK1/2 signaling pathway.

Keywords: Hepatocellular carcinoma; Emodin; Fibroblast growth factor receptor 2; Excision repair cross-complementation group 1; Platinum resistance; Extracellular signal-regulated kinase

Core tip: In this study, our results indicated that emodin could significantly enhance the DNA damage caused by oxaliplatin (OXA) and induce OXA resistance reversal in HepG2/OXA cells. The molecular mechanism for this phenomenon is mediated by the inhibition of excision repair cross-complementing gene 1 expression by the fibroblast growth factor receptor 2/phosphorylated extracellular signal-regulated kinase 1/2 signaling pathway. The results for the reversal of platinum resistance by emodin and the emodin-based enhancement of the efficacy of platinum-based chemotherapy in hepatocellular carcinoma may provide an experimental basis for the further development and application of emodin in the reversal of platinum drug resistance in other types of malignant tumors.