Published online May 14, 2018. doi: 10.3748/wjg.v24.i18.1995
Peer-review started: March 7, 2018
First decision: April 3, 2018
Revised: April 13, 2018
Accepted: April 23, 2018
Article in press: April 23, 2018
Published online: May 14, 2018
Derangement in intestinal microbial composition impacts in mucosal inflammation, tumour promotion and neoplastic progression. Given that the intestinal microbiota can be modulated by several factors, and probiotic supplementation is an interesting alternative to re-establish intestinal eubiosis. Furthermore, in vitro studies and experiments with animal models demonstrated that several bacteria strains (probiotics) can modulate proliferative, apoptotic and inflammatory pathways; increase the innate immune response; produce anti-tumourigenic and anti-mutagenic compounds and destroy carcinogens; reduce genotoxicity; and increase intestinal barrier. Thus, probiotic modulation of intestinal microbiota has emerged as a potential chemopreventive agent.
Despite the idea that probiotic supplementation could prevent colorectal cancer (CRC), little is known about the supplementation of a mix of bacterial probiotic strains as well as its impact in the intestinal microbiota composition and neoplastic transformations of the intestinal mucosa. Our data can contribute to solve the gaps in the literature of whether this mix of probiotic, dose and time of supplementation used was able to alter the alpha and beta diversity of the intestinal microbiota, and how this treatment impact in colitis, serum cytokines and neoplastic development.
The aim of this work is to investigate the effect of supplementation of a Lactobacillus acidophilus, Lactobacillus rhamnosus and Bifidobacterium bifidum mixture on the intestinal microbiota composition, inflammation and neoplastic alterations in the colon during the development of an experimental model of colitis associated colon cancer (CAC). Overall, this study intents to strengthen data from preclinical studies, encouraging clinical trials to investigate their role in preventing colitis and CRC in humans.
We used an experimental model of CAC. C57BL/6 mice received intraperitoneal injection of Azoxymethane, followed by 3 cycles of 2.5% dextran sulphate sodium in drinking water, with an interval of 14 days between cycles. The intervention group received by gavage daily 0.6 billion CFU (colony forming units) each of Lactobacillus acidophilus, Lactobacillus rhamnosus and Bifidobacterium bifidum, diluted in 200 μL of drinking water, while the control group received 200 μL of drinking water daily. Colon tissues were collected for inflammatory index analysis in histological sheets and western blotting to assess inflammatory proteins expression. Cytokines expression in serum and tumour tissue was performed by multiplex immunoassay, and in tumour samples were also used Real Time-PCR. Microbiota analysis was done from colon faeces using 16S rRNA sequencing method.
Probiotic supplementation reduces tumour incidence in a colitis associated colorectal model, we found decreased tumour number and smaller tumour size in probiotic group. In parallel, probiotic supplementation changes the gut microbiota in the colon. We did not detect any change in alpha diversity of the intestinal microbiota, but a difference in beta diversity and in the microbial composition at the genus and phylum level. In addition, probiotic supplementation reduced 46% the inflammatory index compared to the control group. Overall, these results highlight the potential for use of these probiotics mixture to human colitis to reduce inflammation and prevent colon cancer. Thus, further clinical trials are needed to confirm these preclinical insights.
We found that supplementation with Lactobacillus acidophilus, Lactobacillus rhamnosus and Bifidobacterium bifidum during colitis associated colorectal carcinogenesis model changed intestinal microbiota, without altering richness and diversity of intestinal microbiota. Lactobacillus and Bifidobacterium increased in probiotic group and may be responsible for chemopreventive effect of probiotic supplementation on CRC. In summary, we suggest that probiotic supplementation could prevent CAC development by changes in microbiota composition which promotes intestinal homeostasis and regulates the inflammatory response, reducing inflammatory cell infiltration by lowering chemokine expression.
The present study made biological plausible that probiotic supplementation can reduce inflammation and prevent CRC in patients with colitis. Therefore, clinical trials are needed to confirm this hypothesis and increase the therapeutic arsenal against this haunted disease.