2023-09-22 12:21:20
by Anna Fregonara
A new study shows that some postbiotics, in addition to making tumor cells recognizable to the immune system, also play a role in enhancing the effectiveness of immunotherapy
Some postbiotics, molecules released by the bacteria of the intestinal microbiota during the fermentation of foods, seem to be able to unmask tumor cells, making them recognizable by the immune system. As? Forcing them to show some receptors that identify them, called HLA from the English Human Leukocyte Antigen, without which the immune system cannot “see” them. The bacterial strain studied by the researchers, already known for its anti-inflammatory properties, is called Lactobacillus paracasei. Combining his postbiotics (they wouldn’t work alone) with immunotherapy drugs already approved in the clinic seems to help boost the effectiveness of immunotherapy. what emerges from a study financed by AIRC and the Alan Ghitis Association, led by Professor Maria Rescigno, head of the Laboratory of Mucosal Immunology and Microbiota of IRCCS Istituto Clinico Humanitas and vice-rector of Research of Humanitas University and published in the journal Cancer Cell.
How the microbiota works
The intuition to focus on postbiotics arose from the observation of the systemic effect of the intestinal microbiota, a complex ecosystem composed of trillions of microorganisms. anchored to the walls of the intestine, yet seen capable of acting remotely, continues the expert. Studies have also highlighted a role for melanoma, lung cancer and kidney cancer. Hence the idea that it could be the metabolic products of the intestinal microbiota that were acting. One of the most interesting aspects of postbiotics is, in fact, their ability to circulate through the blood and, thus, to influence the organism in a systemic way. In fact, this is their way of mediating the remote action of the intestinal microbiota in other areas of the body. The other interesting aspect of postbiotics concerns their role as a more precise and powerful therapeutic tool. Bacterial strains can release multiple substances, but some are not of therapeutic interest. Learning to select and exploit them allows, instead of transplanting or modifying the microbiota as is done in some studies, to administer only the “pure” mixture of beneficial metabolites.
The next steps
The silencing of HLA receptors, which allows tumors to escape the immune system, is one of the best known mechanisms of immunoevasion for decades. In order to no longer be recognized by T lymphocytes, our defense system responsible for many immune responses, the tumor cell reduces the expression of these receptors without turning them off completely because it would be counterproductive for the tumor cell itself. In this way, in fact, it would alert other cells of the immune system (the natural killer cells), concludes the expert. instead, it is the first time that the ability of postbiotics – and therefore of the microbiota – to influence the expression of HLA on tumor cells has been demonstrated, inducing them to show their receptors and thus become “visible” to the immune system. The research results are currently limited to a preclinical context because they were obtained in laboratory experiments on melanoma, colorectal and breast tumor models. The next step will be to start a clinical trial to verify whether the immunotherapy-postbiotic approach could constitute a new and effective therapeutic strategy. Postbiotics are products of bacterial origin, the study will therefore not be pharmacological and for this reason its process will be shorter.
September 22, 2023 (modified September 22, 2023 | 12:15)
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