Anti-proliferative and Anti-metastatic Potential of High Molecular Weight Secretory Molecules from Probiotic Lactobacillus Reuteri Cell-Free Supernatant Against Human Colon Cancer Stem-Like Cells (HT29-ShE)

Cancer stem cells population are necessary for cancerous invasion. Previous studies have indicated anti-tumor properties of probiotic Lactobacillus reuteri. At the current study, the effect of heat-killed sonicated (HK-SON) fraction and defined molecular weight secreted fractions from L. reuteri cell-free supernatant (CFS) on invasion and apoptosis levels of HT29-ShE cells was investigated. HT29-ShE cells were treated with a range of defined molecular weight fractions derived from CFS and HK-SON. A group of the cells was treated with uninoculated sterile bacterial growth media (MRS) as the negative control for 24 h. Afterward, real-time PCR analysis was done for investigating the relative production level of MMP-9, TIMP-1, and COX-2 mRNA. Matrigel-coated insert plates were used to evaluate cell invasion. The pro-apoptotic effect of CFS and HK-SON was determined using flowcytometry, and the gelatinolytic role of MMP-9 was analyzed via gelatin zymography. HK-SON treatment and defined fractions of CFS significantly decreased the cell invasion versus the MRS group (p < 0.05). Moreover, expression level and activity of MMP-9 was considerably reduced after processing with 10-50 kD, 50-100 kD, and > 100 kD, and HK-SON fractions (p < 0.05). Furthermore, crude CFS, and > 100 kD fraction significantly up-regulated the production level of TIMP-1 (p < 0.05) and HK-SON and > 100 kD fractions significantly increased the apoptosis percentage of HT29-ShE cells. Our results indicate the anti-metastatic and anti-proliferative properties of CFS derived from L. reuteri. Findings suggest that a secretory macromolecule (s) such as a polysaccharide, nucleic acid, or protein might exert these inhibitory effects on colon cancer stem-like cells. In conclusion, our results indicated that cell-free supernatant components can be used as the anti-metastatic agent. However, this study must be performed in experimental and in vivo models for further results.