Synergistic effects of metformin and curcumin on cytotoxicity of chemotherapy drugs using a gastric cancer cell line model

Gastric cancer has a weak prognosis and its usual treatments depend on surgery and chemotherapy. These treatments suffer from some drawbacks such as high rates of local recurrence and metastasis, low survival rates, and significantly decreased life quality. Therefore, new therapeutic methods for improved gastric cancer care with minimal side effects seem necessary. Currently, combinatorial treatments for cancer are preferred and recently, metformin (Met) and curcumin (Cur) have been interesting options for this type of therapy. The aim of the present study was to investigate anticancer effects of metformin and curcumin in both single and combinatorial treatment forms on AGS gastric cancer cell line. In comparison to single treatments with each substance, the results of co-treatments with metformin and curcumin indicated synergistic inhibitory effects on cell viability, wound healing, cell migration and invasion, and primary tumor formation. To determine the selective effect of combination of “Met + Cur” on cancerous cells, very low doses of 8 anticancer drugs (cisplatin, carboplatin, oxaliplatin, epirubicin, doxorubicin, docetaxel, paclitaxel, and methotrexate) used in MTT assay were comparatively tested on AGS cancer cells and normal HDF cells for 48 and 72 hours. The results indicated that the combination of “Met + Cur” significantly increased cytotoxic effects of all anticancer drugs of AGS cells. It is while in normal HDF cells, combination of “Met + Cur” along with anticancer drugs had no effect. This can be inferred as selectively additive effect.