Effect of Lactobacillus acidophilus CICC 6074 S-layer protein on Colon Cancer HT-29 Cells Proliferation and Apoptosis

The purpose of this study was to investigate the effects of Lactobacillus acidophilus CICC 6074 S-layer protein on viability, adhesion, cell cycle and apoptosis of human colon cancer HT-29 cells, and to explore its molecular mechanism of tumor suppression. The S-layer protein at doses of 0, 25, 50 and 100 mg/L significantly inhibited proliferation of HT-29 cells. The S-layer protein exert their cytotoxic activities against colon-cancer HT-29 cells by arresting cell-cycle in the G1 phase through up-regulating the expression of p53, p21 and p16, down-regulating the expression of CDK1 (cyclin-dependent kinases) and Cyclin B. Morphological changes were further observed by TEM (transmission electron microscope) and the cells treated with S-layer protein showed obvious characteristic changes of apoptosis including chromatin condensation, nuclear fragmentation and vacuoles and so on. Furthermore, our mechanism studies indicated that S-layer protein may induce HT-29 cell apoptosis through the death receptor apopt...