Research in mouse models indicates that by improving the immune response two prebiotics — mucin and inulin — may inhibit the growth of melanoma tumors. Nevertheless, there is still a long way to go until the scientists can validate this approach’s efficacy in humans.
Prebiotics are natural substances, which promote beneficial bacteria’s growth and development.
For this reason, researchers have recently stepped up their efforts to find out more about how prebiotics might influence various biological mechanisms.
Some research suggests that if used correctly, these compounds could even help to combat different types of health problems.
A new study published in Cell Reports this month indicates that the mucin and inulin prebiotics can help boost the immune response to melanoma tumours.
The research comes from researchers associated with the La Jolla, CA Sanford Burnham Prebys Medical Discovery Institute. Researchers used mouse models to explore the possibility of using prebiotics to treat melanoma.
Prebiotics slowed down tumor growth
“Earlier studies have shown that prebiotics inhibit tumor growth, but the mechanism by which they do so has not been clear until now,” explains senior author Prof. Ze’ev Ronai.
“Our study shows for the first time that prebiotics limit cancer growth by enhancing anti-tumor immunity,” he adds, adding also that it “supports further exploration of the potential benefits of prebiotics in treating cancer or increasing current therapies.”
As the team had gaged from previous in vitro studies, mucin and inulin showed some promise to stimulate immune responses to tumors.
In the current study, the authors conducted a series of experiments in which they first delivered healthy mice via their food or drink, either inulin or mucin.
They then transplanted melanoma or colon cancer cells into the mice to see if the prebiotics had any effect on the development of tumours.
Both mucin and inulin appeared to slow growth of melanoma tumors, they found. Even mice who had obtained inulin, however, displayed a decrease in growth in colon cancer.
As for the mechanism behind tumor growth slowing, the mice with melanoma— whichever prebiotic they had got — saw an rise in immune cells that defended against tumours.
These cells have been able to infiltrate the tumors of melanoma, suggesting that the prebiotics were the source of the boost in immune response.
The researchers also found that prebiotic mice had shown improvements in their microbiota. More precisely, inulin boosted bacterial populations of Barnesiella and Bacteroides, while mucin boosted bacteroid, parabacteroid, olsenella, and clostridium populations.
Promising ‘scientific advances’
One research line included considering the impact of prebiotics on the treatment of NRAS-mutant melanoma, which is a highly aggressive type of melanoma.
Doctors are currently taking MEK inhibitors to treat NRAS-mutant melanoma. These are medications that block an overactive cellular signaling pathway in some cancers, allowing them to proliferate.
The main issue with this treatment line is that many tumors receiving MEK inhibitor drug treatment become resistant to it, the researchers explain.
But the mice that had eaten a diet containing inulin NRAS-mutant melanoma showed delayed resistance to MEK inhibitor drugs.
From experiments with mice with “cold” BRAF-mutant melanoma tumors— tumors that did not manage to penetrate T cells (specialized immune cells) — they found that rodents responded to prebiotics as well as standard immune control point therapy.
“Prebiotics are a powerful tool for reforming gut microbiomas and recognizing bacteria that contribute to the defense against cancer,” says co-author Prof. Scott Peterson.
“The scientific advances we are making here are getting us closer to the idea of implementing prebiotics in cutting-edge cancer treatments.”– Prof. Scott Peterson
While current findings suggest that the two prebiotics are promising as a new therapeutic avenue for cancer, Prof. Ronai emphasizes that researchers are still a long way from assessing their efficacy in humans.
“In our understanding of how certain prebiotics affect tumor growth, our findings are a step forward, but we are far from applying them to humans,” says Prof. Ronai.
Still, he adds,”[ f]our future studies need to be carried out in more complex animal models of different genetic backgrounds and ages to address the complex nature of human tumors before we can consider evaluating these prebiotics in humans.”