Abstract: Objective:To investigate the biotransformation of n-3 PUFAs in HCT116 cells,and the tumoricidal action of the PUFAs metabolites such as LTB₄,PGE₂,LXA₄. Methods:Experiments in vitro were conducted on HCT116 cells supplemented with different concentration of ALA,EPA,DHA and 5-fluorouracil(5-FU)and the purposes were to investigate cell viability,apoptosis,lipid droplets,fatty acid composition,formation of PGE₂,LTB₄ and LXA₄ in HCT116 cells. Effects of PGE₂,LTB₄ and LXA₄ on cell viability were investigated by MTT assay. Results:It was observed that n-3 PUFAs(ALA,EPA,DHA)and 5-FU inhibited the growth of HCT116 colorectal carcinoma cells and produced significant apoptosis induction effect. The apoptosis rate of HCT116 cell was 7.9%,21.8%,29.2% when supplemented with ALA(200 μmol/L),EPA(160 μmol/L),DHA(120 μmol/L).N-3 PUFAs-treated cells showed an increased number of lipid droplets in their cytoplasm. As expected,higher ratio of unsaturated fatty acid was noted in the ALA,EPA,DHA treated groups compared to control. ALA,DHA and EPA supplementation to HCT116 cells suppressed production of LTB₄,but enhanced the ratio of LXA₄ to PGE₂ and then caused cancer cells to become anti-inflammatory. Conclusion:The toxicity of n-3 PUFAs(ALA,EPA,DHA)on colon cancer HCT116 cells in vitro was associated with inhibiting in the production of pro-inflammatory LTB₄ and enhancing formation of anti-inflammatory LXA₄.