Identification of Lactobacillus Fermentum Strains with Potential against Colorectal Cancer by Characterizing Short Chain Fatty Acids Production, Anti-Proliferative Activity and Survival in an Intestinal Fluid: In Vitro Analysis

The use of probiotics as preventive agents in colorectal cancer (CRC) was widely suggested in many clinical and pre-clinical studies and often linked to affecting short chain fatty acids (SCFA) in the gut. However, the understanding of fatty-acid-producing activity of certain probiotics and their preventive and anti-cancer potential remains incomplete. Here, L. fermentum strains were investigated for a number of features that make them good candidates for use in CRC treatments. Using cell free extracts, L. fermentum NCIMB -5221, -2797 and -8829 were first compared based on SCFAs production and anti-proliferative activity against Caco-2 colon cancer cells. The corresponding SCFAs synthetic formulations, similar to the ones produced by the bacteria, were prepared then compared with the latter to determine the role an efficacy of naturally produced SCFAs in inhibiting the proliferation of colon cancer cells. Later, the bioactivity and stability of L. fermentum bacteria in a simulated intestinal fluid (SIF) were determined. Results showed that L. fermentum NCIMB -5221 and -8829 were the most potent in producing SCFAs, in particular, acetic (192.3 ± 4 mg/L minimum), propionic (69.2 ± 1.6 mg/L minimum), and butyric (35.4 ± 2.9 mg/L minimum) acids and were observed to better inhibit the growth of Caco-2 cells (53.4 ± 1.6%, 72 h, p=0.021) in comparison with L. acidophilus ATCC 314. They also showed resistance to SIF (16.3 ± 1.9% minimum, 72 h, p=0.006) and produced SCFAs in SIF at concentrations high enough to significantly inhibit Caco-2 proliferation (74.73 ± 2.1%, 72 h). Potentially, based on characteristics related to bacterial cell survival and SCFA production, and anti-proliferative activity, certain L. fermentum could be considered as biotherapeutic agent against CRC.