Cell-free extracts of Lactobacillus acidophilus and Lactobacillus delbrueckii display antiproliferative and antioxidant activities against HT-29 cell line

Many beneficial effects of probiotic Lactobacilli on cancer prevention and therapy were previously presented. So finding probiotics with proapoptotic activities is a promising approach for cancer drug discovery. Here, the antiproliferative and antioxidant activities of cell-free extracts of Lactobacillus acidophilus and Lactobacillus delbrueckii on HT-29 cell line were evaluated employing MTT and DPPH assays. The induction of apoptosis was assessed by Hoechst staining and flow cytometry analysis which was further confirmed by expression analysis of BCL-2, BAX, caspase-3, caspase-8, and caspase-9 genes using real-time quantitative PCR. Caspase-3 activity was also analyzed. Results showed that cell viability was significantly reduced to 42.2 +/- 0.01% and 19.40 +/- 0.01% by 5 and 8 mg ml(-1) of L. acidophilus and L. delbrueckii extracts, respectively. Apoptosis induction was shown with both bacterial extracts. Caspase-9 and caspase-3 overexpression as well as Bax/Bcl-2 ratio increase revealed the ability of both probiotics to induce intrinsic pathway-dependent apoptosis. The extrinsic pathway was also activated by L. acidophilus. At the concentration of 198 mu g ml(-1), L. acidophilus and L. delbrueckii had a DPPH scavenging activity of 59.37 +/- 3.97% and 71.19 +/- 3.64%, respectively. Taken together, these findings provide evidence for antiproliferative, proapoptotic, and antioxidant effects driven by these probiotic lactic acid bacteria (LAB) strains.