Recombinant oncolytic adenovirus combined with cyclophosphamide induces synergy in the treatment of breast cancer

Abstract Purpose: Oncolytic virus therapy has gradually become an important approach in cancer treatment. We intend to explore the therapeutic effects of the combination of a dual cancer-selective anti-tumor recombinant adenovirus (Ad-Apoptin-hTERTp-E1a) and cyclophosphamide on breast cancer cells.Methods: The inhibition of Ad-Apoptin-hTERTp-E1a (Ad-VT), cyclophosphamide, and Ad-VT + Cyclophosphamide on MCF-7 and MDA-MB-231 cells were investigated by the CCK-8 assay. According to the inhibition rate of different treatment combinations, the combination index (CI) was analyzed and calculated using the CalcuSyn software to determine the best combination. The CCK-8 assay and crystal violet staining were used to detect the cytotoxicity of the combination Ad-VT and cyclophosphamide in breast cancer cells and breast epithelial cells. Subsequently, hoechst staining, Annexin V flow cytometry and JC-1 staining were used to analyze the inhibitory pathway of the combination Ad-VT and cyclophosphamide on breast cancer cells. Cell migration and invasion of breast cancer cells were detected using cell-scratch and Transwell assays. The antitumor effect of different treatment groups on tumor-bearing nude mouse model were also analyzed. Results: The results showed that the treatment combination of Ad-VT (40 MOI) and cyclophosphamide (400 µM) significantly inhibited MCF-7 and MDA-MB-231 cells and reduces the toxicity of cyclophosphamide in normal cells. Ad-VT mainly induces breast cancer cell apoptosis through the endogenous apoptotic pathway. This apoptotic effect is significantly increased after Ad-VT and cyclophosphamide combined treatment. This combination significantly inhibited the migration and invasion of MCF-7 and MDA-MB-231 cells. Then in vivo experiments showed that treatment combination of Ad-VT and cyclophosphamide significantly inhibited tumor growth and extended the survival time of mice.Conclusions: The results showed that the combination of Ad-VT and cyclophosphamide had the effects of reducing toxicity and increasing efficiency in the treatment of breast cancer cells.