Overexpression of B7-H3 augments anti-apoptosis of colorectal cancer cells by Jak2-STAT3.

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.

• Authors: Ting Zhang, Bo Jiang, Shi-Tao Zou, Fen Liu, Dong Hua
• Journal: World journal of gastroenterology (World J Gastroenterol) Vol. 21 Issue 6 Pg. 1804-13 (Feb 14 2015) ISSN: 2219-2840 [Electronic] United States
• PMID: 25684945 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antineoplastic Agents
• Apoptosis Regulatory Proteins
• B7 Antigens
• CD276 protein, human
• Protein Kinase Inhibitors
• STAT3 Transcription Factor
• STAT3 protein, human
• JAK2 protein, human
• Janus Kinase 2

Topics

• Antineoplastic Agents (therapeutic use)
• Apoptosis (drug effects)
• Apoptosis Regulatory Proteins (metabolism)
• B7 Antigens (genetics, metabolism)
• Cell Line, Tumor
• Cell Survival
• Colorectal Neoplasms (enzymology, genetics, pathology)
• Dose-Response Relationship, Drug
• Drug Resistance, Neoplasm
• Gene Expression Regulation, Neoplastic
• Humans
• Janus Kinase 2 (antagonists & inhibitors, metabolism)
• Phosphorylation
• Protein Kinase Inhibitors (pharmacology)
• RNA Interference
• STAT3 Transcription Factor (metabolism)
• Signal Transduction
• Transfection
• Up-Regulation