title: Overexpression of B7-H3 augments anti-apoptosis of colorectal cancer cells by Jak2-STAT3.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors: Ting Zhang, Shi-Tao Zou, Fen Liu, Institute of Cancer, Affiliated hospital of Jiangnan University, Wuxi 214062, Jiangsu Province, China.
authors: Ting
authors: T
authors: Zhang
authors: Ting Zhang, Shi-Tao Zou, Fen Liu, Institute of Cancer, Affiliated hospital of Jiangnan University, Wuxi 214062, Jiangsu Province, China.
authors: Bo
authors: B
authors: Jiang
authors: Ting Zhang, Shi-Tao Zou, Fen Liu, Institute of Cancer, Affiliated hospital of Jiangnan University, Wuxi 214062, Jiangsu Province, China.
authors: Shi-Tao
authors: ST
authors: Zou
authors: Ting Zhang, Shi-Tao Zou, Fen Liu, Institute of Cancer, Affiliated hospital of Jiangnan University, Wuxi 214062, Jiangsu Province, China.
authors: Fen
authors: F
authors: Liu
authors: Ting Zhang, Shi-Tao Zou, Fen Liu, Institute of Cancer, Affiliated hospital of Jiangnan University, Wuxi 214062, Jiangsu Province, China.
authors: Dong
authors: D
authors: Hua
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D060887:B7 Antigens / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival; D015179:Colorectal Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D053614:Janus Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection; D015854:Up-Regulation
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; D060887:B7 Antigens; C423237:CD276 protein, human; D047428:Protein Kinase Inhibitors; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C507924:JAK2 protein, human; D053614:Janus Kinase 2
keywords: Apoptosis; B-cell CLL/lymphoma 2; B7-H3; Colorectal cancer; Jak2-STAT3; Overexpression; Signaling pathway