Effects of Lactobacillus strains on cancer cell proliferation and oxidative stress in vitro.

AIMS The objective of this study was to assess in vitro, whether heat-killed (HK) lactic acid bacteria cells and fractionations of HK cells could suppress the viability of human cancer cells and inhibit the cytotoxicity associated with oxidative stress. METHODS AND RESULTS Among the strains, the HK cells of Lactobacillus acidophilus 606 and Lactobacillus casei ATCC 393 exhibited the most profound inhibitory activity in all of the tested cell lines. HK cells of L. acidophilus 606 were determined to be less toxic to healthy human embryo fibroblasts (hEF cells) than were HK cells of L. casei ATCC 393. The soluble polysaccharides from L. acidophilus 606 evidenced the most effective anticancer activity, but inhibited hEF cell growth by only 20%. The soluble polysaccharides from L. acidophilus 606 were partly observed to induce apoptosis in the HT-29 cells by DNA fragmentation and propidium iodine staining. Both the HK cells of L. acidophilus 606 and the soluble polysaccharide components of this strain also exhibited potent antioxidative activity. CONCLUSIONS Our findings suggest that the soluble polysaccharide fraction from L. acidophilus 606 may constitute a novel anticancer agent, which manifests a high degree of selectivity for human cancer cells and antioxidative agent in the food industry. SIGNIFICANCE AND IMPACT OF THE STUDY These soluble polysaccharide components from Lactobacillus may be applied to various foods, and used as adjuncts for cancer therapy and prevention.