Gastric cancer is the fourth most common cancer and the second case of death in the world. According to studies, gastric cancer is relatively sensitive to chemotherapy. The aim of this study was to investigate the association of oral administer PUFAs with Caspase enzymes in patients with gastric cancer under chemotherapy. The results of this study show that use of PUFAs as supplement with Cis-platinum may be useful to stimulate more caspase-3 and 9, pro-apoptotic, PPAR-Gamma gene expression and proteins and levels of DNA damage in gastric cancer cells. Consequently, this offers an effective treatment to patients with gastric cancer to respond to chemotherapy.