Cytotoxicity and Apoptosis Induction of Lactobacillus acidophilus Cell-free Supernatant against Human Colon Carcinoma Cell Line

Background: Lactobacillus acidophilus is one of the promising probiotics that attracts the attention of the scientific community to research its therapeutic characteristics that can provide an option to fight colon cancer. Methods: The cytotoxic effect of cell-free supernatant of Lactobacillus acidophilus (LACFS) was evaluated by using the MTT 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) test to measure cell viability and the high content screening assay (HCS) to detect apoptotic cell death. Result: LACFS was found to possess the highest anticancer activity on Caco-2 at 50 µg/ml. NCM425 cells were more tolerant toward LACFS than the Caco-2 when the Half-maximal inhibitory concentration (IC50) was 161.8 µg/ml on NCM425 compared to 30.63 µg/ml on Caco-2. When 6.25,12.5, 25 and 50 µg/ml concentrations of LACFS were applied, a substantial drop in mitochondrial membrane potential occurred. A significant rise in cytochrome C release and total nuclear intensity was recorded at 25 and 50 µg/ml concentrations and the viable cell count was decreased at 12.5, 25 and 50 µg /ml, while membrane permeability was dropped at 50 µg/ml. The expression of caspase 3 was observed at 50 µg/ml only while caspase 9 expression was seen at 25 and 50 µg/ml which further indicates that the harmful effect on the Caco2 cells causes them to die through apoptosis.