Identification of probiotic bacteria with anticancer activity against colorectal cancer in vitro

Abstract

Colorectal cancer is the third most common cause of cancer death worldwide. It is ranked third for new cancer patients in Thailand. Colorectal cancer is associated with multifactorial risk factors including the imbalance of gut microbiota. This project aimed to identify Lactobacillus strains isolated from Thai healthy populations that have anticancer activities against colorectal cancer in vitro. Lactobacillus cultured media (LCM) obtained from thirty-nine Lactobacillus strains, previously shown to have anti-inflammatory activity, were selected and used at different concentrations and/or pH adjustment to determine the anti-proliferative effect on HT-29 and Caco-2 colon cancer cells at 24, 48, and 72 h. The cell viability was analyzed by 2-(4,5-dimethyl-2-thiazolyl)-3,5-diphenyl-2H-tetrazolium bromide (MTT assay). LCM from 2 out of 39 strains, L. vaginalis L19 and L. gasseri L20, significantly reduced cell viability at certain concentrations and time-points. Due to weak anti-proliferative activity of LCM, viable L. vaginalis L19 and L. gasseri L20 were used to treat Caco-2 cells and cell viability was determined by flow cytometry. L. gasseri L20 at the MOI of 100 strongly and significantly reduced Caco-2 cell viability more than L. vaginalis L19 after 24 and 48 h incubation. Furthermore, L. vaginalis L19 and L. gasseri L20 could weakly adhere to polarized and differentiated Caco-2 cells, i.e., enterocyte-like epithelial cells, as demonstrated by the adhesion assay and scanning electron microscopy. Therefore, L. vaginalis L19 and L. gasseri L20 might be useful for prevention of colorectal cancer in the future.