Infection by Cx43 adenovirus increased chemotherapy sensitivity in human gastric cancer BGC-823 cells: not involving in induction of cell apoptosis

Background and objective: There is a lower basal expression of Connexin43 (Cx43) in human gastric cancer BGC-823 cells. In the present study, BGC-823 cells were transfected with recombinant Cx43 adenovirus plasmid vector, and we explored the influences of Cx43 expression on cell proliferation, chemo-sensitivity, colony forming ability, invasion ability and apoptosis. Moreover, we also determined the expression of Pgp, Cx43, as well as apoptosis-related proteins (bcl-2, box, caspase3 and caspase 9). Methods: MTT assay was performed to determine the proliferation of BGC-823 cells before and after Cx43 transfection. The influences of Cx43 infection on sensitivity of chemotherapy (including Doxorubicin, fluorouracil, oxaliplatin) were detected by MTT assay. Expression levels of Pgp, Cx43, as well as apoptosis-related proteins (bcl-2, bax, caspase-3 and caspase-9) in BGC-823 cells were determined by Western blotting analysis before and after the infection with Cx43 adenovirus. MDR expression was determined by RT-PCR before and after Cx43 infection. Invasive ability was detected by invasion chamber. Influence of Cx43 adenovirus infection on apoptosis of BGC-823 cells was determined by flow cytometry. Results: After infection by Cx43 adenovirus, colony forming rate and invasive ability of BGC-823 cells were decreased. Flow cytometry results revealed that cell apoptosis were insignificantly increased. The data of MTT assay revealed that infection with Cx43 adenovirus, cell proliferation ability decreased and sensitivity to chemotherapy drugs (including doxorubicin, fluorouracil, oxaliplatin) increased. Results of Western blotting analysis revealed that increasing expression levels of Cx43, decreasing expression levels of Pgp, and insignificant changes of bc1-2, bax, caspase3 and caspase 9 were detected. RT-PCR revealed the expression of MDR1 gene, the gene encoding Pgp, decreased significantly (p < 0.05). Conclusion: The human gastric cancer BGC-823 cells were infected with Cx43-IRES2-EGFP recombinant adenovirus vector. Colony formation, invasive ability and cell proliferation all decreased, whereas chemo-sensitivity increased in Cx43 infected BGC-823 cells. The increasing Cx43 expression was accompanied by decreasing Pgp expression and MDR1 m RNA levels. However, apoptosis-related proteins (bc1-2, bax, caspase3 and caspase 9) and cell apoptosis increased insignificantly. All results demonstrated that Cx43 may be negatively regulated the development, invasion and metastasis of gastric cancers, however, it had no obvious relationship with tumor cell apoptosis. (C) 2015 Elsevier B.V. All rights reserved.