All-Trans Retinoic Acid Combination with Cisplatin and 5-Fluorouracil Enhance Cytotoxic Effect on AGS and KYSE-30 Cell Lines

All-trans retinoic acid (ATRA), a derivative of vitamin A, exerts fundamental effects on regulation of cell growth, differentiation and apoptosis. Recent studies have shown an increase in resistance of gastric adenocarcinoma and squamous cell carcinoma to cisplatin and 5 fluorouracil. In this study, we investigated a combination treatment of ATRA with cisplatin and 5-fluorouracil on gastric (AGS) and esophageal (KYSE-30) cancer cell lines. KYSE-30 and AGS cell lines were cultured in RPMT-1640, including sub-toxic concentration of ATRA (13.6 and 3.6µM respectively) for 6 days and then they were treated with cisplatin and 5-fluorouracil for 72h. The effects of combination treatment were tested by MTT assay, ethidium bromide/acridine orange (EB/AO) staining and flow cytometry. Determination of IC50 (Inhibitory concentration of 50%) with MTT assay showed that combination treatment had cytotoxic effect on both cell lines. IC50 value of the combined drugs was lower than the IC50 of drugs alone (p<0/05). The percentage of apoptotic cells increased in comparison to drugs alone in EB/AO staining (p<0/05). Furthermore, there was an indication that the combination of ATRA with cisplatin caused increased cell cycle arrest at G2/M in AGS and KYSE-30 cells. Also, ATRA and 5FU induced enhanced cell cycle arrest at G1/S phase in KYSE-30 and AGS cells (p<0/001). Our findings demonstrate that sub-toxic concentration of combination treatment of ATRA with cisplatin and 5-fluorouracil induces further cytotoxic effects on KYSE-30 and AGS cancer cell lines.