Abstract: Objective：To study the effects of supernatant of Lactobacillus acidophilus (ATCC 4356) and Bifidobacteria longifolia (ATCC 15707) on the proliferation of human colon cancer cells HCT116 and SW480. Methods： HCT116， SW480， Lactobacillus acidophilus and bifidobacterium longum were cultured in vitro. The supernatants of Lactobacillus acidophilus and bifidobacterium longum were extracted respectively. The effects of different components of Lactobacillus acidophilus and Bifidobacterium longum on proliferation of human colon cancer cells were analyzed by MTT assay. Results： The inhibitory effect of Lactobacillus acidophilus supernatant on SW480 cells was weaker than that of MRS medium (F=7.24， P=0.043 3). There was no significant difference in the inhibitory effect of bifidobacterium longeum supernatant and BHI medium on SW480 cells (F=1.81， P=0.236 6)， while there was significant difference in the inhibitory rate of SW480 cells between different concentrations (F=18.07， P=0.003 2). The inhibitory effect of Lactobacillus acidophilus supernatant on HCT116 cells was stronger than that of MRS medium (F=10.33， P=0.023 6)， but there was no significant difference in cell inhibition rate between different concentrations (F=3.51， P=0.097 3).The effect of BHI medium on HCT116 cell proliferation was stronger than that of bifidobacterium longeum supernatant (F=41.12，P=0.001 4). Conclusion： The supernatant of Lactobacillus acidophilus can inhibit the proliferation of HCT116 cells in a certain concentration range， but has no inhibitory effect on SW480 cells. The supernatant of bifidobacterium longum has no inhibitory effect on SW480 and HCT116 cells.

Key words: font-size:medium, ">Lactobacillus acidophilus； Bifidobacterium longum； Cell proliferation； Human colon cancer cell