Basic Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Feb 14, 2015; 21(6): 1804-1813
Published online Feb 14, 2015. doi: 10.3748/wjg.v21.i6.1804
Overexpression of B7-H3 augments anti-apoptosis of colorectal cancer cells by Jak2-STAT3
Ting Zhang, Bo Jiang, Shi-Tao Zou, Fen Liu, Dong Hua
Ting Zhang, Shi-Tao Zou, Fen Liu, Institute of Cancer, Affiliated hospital of Jiangnan University, Wuxi 214062, Jiangsu Province, China
Bo Jiang, Dong Hua, Department of Oncology, Affiliated hospital of Jiangnan University, Wuxi 214062, Jiangsu Province, China
Author contributions: Zhang T and Jiang B contributed equally to this work and should be considered as co-first authors; Jiang B and Hua D designed the research; Zhang T, Zou ST and Liu F performed the research; Zhang T analyzed the data and wrote the paper; Jiang B and Hua D revised the paper.
Supported by Project of Natural Science Foundation of Jiangsu Province, No. BK2012542; and the Project of Hospital Management Center of Wuxi City, No. YGZ1108.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Dong Hua, MD, PhD, Department of Oncology, Affiliated hospital of Jiangnan University, No. 200 Huihe Road, Binhu District, Wuxi 214062, Jiangsu Province, China. wx89211@163.com
Telephone: +86-510-88682109 Fax: +86-510-85808820
Received: July 25, 2014
Peer-review started: July 26, 2014
First decision: August 27, 2014
Revised: September 19, 2014
Accepted: October 21, 2014
Article in press: October 21, 2014
Published online: February 14, 2015
Abstract

AIM: To investigate the role of the overexpression of B7-H3 in apoptosis in colorectal cancer cell lines and the underlying molecular mechanisms.

METHODS: SW620 cells that highly overexpressed B7-H3 (SW620-B7-H3-EGFP) and HCT8 cells stably transfected with B7-H3 shRNA (HCT8-shB7-H3) were previously constructed in our laboratory. Cells transfected with pIRES2-EGFP were used as negative controls (SW620-NC and HCT8-NC). Real-time PCR and western blotting analysis were used to detect the mRNA and protein expressions of the apoptosis regulator proteins Bcl-2, Bcl-xl and Bax. A cell proliferation assay was used to evaluate the survival rate and drug sensitivity of the cells. The effect of drug resistance was detected by a cell cycle assay. Active caspase-3 western blotting was used to reflect the anti-apoptotic ability of cells. Western blotting was also performed to determine the expression of proteins associated with the Jak2-STAT3 signaling pathway and the apoptosis regulator proteins after the treatment with AG490, a Jak2 specific inhibitor, in B7-H3 overexpressing cells. The data were analyzed by GraphPad Prism 6 using a non-paired t-test.

RESULTS: Whether by overexpression in SW620 cells or downregulation in HCT8, B7-H3 significantly affected the expression of anti- and pro-apoptotic proteins, at both the transcriptional and translational levels, compared with the negative control (P < 0.05). A cell proliferation assay revealed that B7-H3 overexpression increased the drug resistance of cells and resulted in a higher survival rate (P < 0.05). In addition, the results of cell cycle and active caspase-3 western blotting proved that B7-H3 overexpression inhibited apoptosis in colorectal cancer cell lines (P < 0.05). B7-H3 overexpression improved Jak2 and STAT3 phosphorylation and, in turn, increased the expression of the downstream anti-apoptotic proteins B-cell CLL/lymphoma 2 (Bcl-2) and Bcl-xl, based on western blotting (P < 0.05). After treating B7-H3 overexpressing cells with the Jak2-specific inhibitor AG490, the phosphorylation of Jak2 and STAT3, and the expression of Bcl-2 and Bcl-xl, decreased accordingly (P < 0.05). This finding suggested that the Jak2-STAT3 pathway is involved in the mechanism mediating the anti-apoptotic ability of B7-H3.

CONCLUSION: The overexpression of B7-H3 induces resistance to apoptosis in colorectal cancer cell lines by upregulating the Jak2-STAT3 signaling pathway, potentially providing new approaches to the treatment of colorectal cancer.

Keywords: B7-H3, Overexpression, Colorectal cancer, B-cell CLL/lymphoma 2, Apoptosis, Signaling pathway, Jak2-STAT3

Core tip: The expression of B7-H3 has been positively correlated with poor prognosis in colorectal cancer. Previous studies revealed the relationship between B7-H3 and tumor invasion and metastasis. In the present study, the role of B7-H3 in apoptosis in colorectal cancer was investigated. Our results showed that overexpression of B7-H3 induced resistance to apoptosis in colorectal cancer cell lines by upregulating the Jak2-STAT3 signaling pathway. These results provide a new vision for designing therapeutics targeting B7-H3 and its associated signaling pathways in the treatment of colorectal cancer.