Probiotic strains modulate cytokine production and the immune interplay between human peripheral blood mononucear cells and colon cancer cells

Human health is tightly connected with a great number of gut microbial cells designated as microbiome or microbiota. We have examined the effect of six microbial strains (MS) included in a commercial probiotic on cytokine production by human peripheral blood mononuclear cells (PBMC) and on their immune dialog with colon carcinoma cells. Non-stimulated and lipopolysaccharide (LPS)-stimulated PBMC were incubated for 24 h with MS. The secretion of tumor necrosis factor alpha (TNFα), IL-1β, IL-6, interferon gamma, IL-10 and IL-1ra and the effect of MS on the immune interplay between PBMC and cells from HT-29 and RKO colon carcinoma lines were evaluated. MS incubated with non-stimulated PBMC induced high expression of all cytokines examined, whereas in those stimulated by LPS, variability in the results was observed. MS added to PBMC co-cultivated with HT-29 or RKO colon cancer cells resulted in downregulation of most cytokines except IL-6 and TNFα, and enhanced production of TNFα and IL-1β. The MS incorporated in the probiotic affected PBMC' cytokine production and altered the cross-talk between immune and colon cancer cells. The results may clarify the way by which probiotics modify the intestinal environment resulting in a decline of colon cancer development.