Original Article
Copyright ©2012 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Gastroenterol. Sep 14, 2012; 18(34): 4704-4713
Published online Sep 14, 2012. doi: 10.3748/wjg.v18.i34.4704
Emerging roles of the ribonucleotide reductase M2 in colorectal cancer and ultraviolet-induced DNA damage repair
Ai-Guo Lu, Hao Feng, Pu-Xiong-Zhi Wang, Ding-Pei Han, Xue-Hua Chen, Min-Hua Zheng
Ai-Guo Lu, Hao Feng, Pu-Xiong-Zhi Wang, Min-Hua Zheng, Shanghai Minimally Invasive Surgery Center, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
Ding-Pei Han, Department of Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China
Xue-Hua Chen, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China
Author contributions: Lu AG and Feng H contributed equally to this work; Feng H, Lu AG and Zheng MH designed the research; Feng H, Lu AG and Wang PXZ performed the research with Chen XH; Feng H and Han DP analyzed data; Feng H and Lu AG wrote the manuscript; Lu AG and Zheng MH revised and finally approved the article to be published.
Correspondence to: Dr. Hao Feng, Shanghai Minimally Invasive Surgery Center, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China. fengzi.x@163.com
Telephone: +86-21-63846590 Fax: +86-21-63846590
Received: February 11, 2012
Revised: June 11, 2012
Accepted: June 28, 2012
Published online: September 14, 2012
Abstract

AIM: To investigate the roles of the ribonucleotide reductase M2 (RRM2) subunit in colorectal cancer (CRC) and ultraviolet (UV)-induced DNA damage repair.

METHODS: Immunohistochemical staining of tissue microarray was performed to detect the expression of RRM2. Seven CRC cell lines were cultured and three human colon cancer cell lines, i.e., HCT116, SW480 and SW620, were used. Reverse transcription polymerase chain reaction and Western blotting were performed to determine the mRNA and protein expression levels of RRM2, respectively. Cell proliferation assay, cell cycle analysis were performed. Cell apoptosis was evaluated by double staining with fluorescein isothiocyanate-conjugated Annexin V and propidium iodide (PI) using Annexin V/PI apoptosis kit. The motility and invasion of CRC cells were assessed by the Transwell chamber assay. Cells were irradiated with a 254 nm UV-C lamp to detect the UV sensitivity after RRM2 depletion.

RESULTS: Immunohistochemical staining revealed elevated RRM2 levels in CRC tissues. RRM2 overexpression was positively correlated with invasion depth (P < 0.05), poorly differentiated type (P = 0.0051), and tumor node metastasis stage (P = 0.0015). The expression of RRM2 in HCT116 cells was downregulated after transfection, and HCT116 cell proliferation was obviously suppressed compared to control groups (P < 0.05). In the invasion test, the number of cells that passed through the chambers in the RRM2-siRNA group was 81 ± 3, which was lower than that in the negative control (289 ± 7) and blank control groups (301 ± 7.2). These differences were statistically significant (P < 0.01). Our data suggest that RRM2 overexpression may be associated with CRC progression. RRM2 silencing by siRNA may inhibit the hyperplasia and invasiveness of CRC cells, suggesting that RRM2 may play an important role in the infiltration and metastasis of CRC, which is a potential therapeutic strategy in CRC. In addition, RRM2 depletion increased UV sensitivity.

CONCLUSION: These findings suggest that RRM2 may be a facilitating factor in colorectal tumorigenesis and UV-induced DNA damage repair.

Keywords: Ribonucleotide reductase M2, Colorectal cancers, Tissue microarray, Ultraviolet irradiation, Cancinogenesis, Metabolic genes