Influences of probiotics and gut microbiota on immunomodulation for the treatment of patients with cancer: a systematic review

Introduction: Immunomodulation and immunostimulation are the main mechanisms of action of probiotics in the fight against cancer. Objective: It was to carry out a systematic review of the influences of probiotics and gut microbiota on immunomodulation for the treatment of cancer patients. Methods: The PRISMA Platform systematic review rules were followed. The research was carried out from September to October 2023 in the Web of Science, Scopus, PubMed, Science Direct, Scielo, and Google Scholar databases. The quality of the studies was based on the GRADE instrument and the risk of bias was analyzed according to the Cochrane instrument. Results and Conclusion: A total of 125 articles were found, and 35 articles were evaluated in full and 18 were included and developed in the present systematic review study. Considering the Cochrane tool for risk of bias, the overall assessment resulted in 45 studies with a high risk of bias and 15 studies that did not meet GRADE and AMSTAR-2. Most studies showed homogeneity in their results, with X2=55.4%>50%. It was concluded that probiotics suppress inflammation by inhibiting several signaling pathways and reducing the global activation of NF-κβ and the production of pro-inflammatory cytokines. Probiotics influence receptor antagonism, receptor expression, binding and expression of adapter proteins, expression of negative regulatory signal molecules, and mainly the induction of microRNAs. These microRNAs can modulate the gene expression of tumor cells together with regulatory T cells that have important functions in the tumor microenvironment, mainly in inducing immune evasion. Some modulatory effects of probiotics include the production of cytokines by epithelial cells, increased mucin secretion and phagocytosis and NK cell activity, activation of T and NKT cells, stimulation of IgA production, and decreased proliferation of T cells. The gut microbiota has a major impact on the systemic immune system. The specific microbiota controls cell differentiation in which CD4+ T cells (Th17 cells) secrete IL-17. The presence of Th17 cells and regulatory T cells is associated with the gut microbiota.