Does Lactobacillus Exert a Protective Effect on the Development of Cervical and Endometrial Cancer in Women?

Simple Summary Cervical cancer is the fourth most common cancer in women worldwide. Tumour-related deaths are most frequent in low- and middle-income countries. Currently, most vaccines against human papillomavirus (HPV) are based on virus-like particles; they protect against HPV infection but have no therapeutic effects. Because dysbiosis has been shown to increase cancer risk, lactic acid bacteria (LAB)-based vaccines, which have been shown to have an immunomodulatory effect, have recently attracted attention. Mucosal immunization with viable colonies of Lactobacillus via intranasal, intravaginal, and oral routes to decrease the risk of cervical cancer seems promising; thus, such research is of high value. While advances have been made in understanding associations between microbiota dysregulation and carcinogenesis, further studies are required to identify the underlying cellular mechanisms and to confirm previous findings. This manuscript summarizes available data concerning the impact of microbiota on cancer risk and presents recent strategies to fight cervical and endometrial cancers. Cervical cancer is a significant health problem with increasing occurrence and mortality. This infection-associated tumour is caused by the human papillomavirus (HPV). HPV infection is cleared by the immune system within 6-18 months in most patients; however, persistent high-risk HPV (hrHPV) infections can lead to the development of cervical cancer. Virus persistence is promoted by immunodeficiency, Chlamydia trachomatis infection, smoking, and age, as well as the imbalance of cervicovaginal microbiota and inflammation. The abundance of bacteria in the vagina favours the maintenance of a dynamic balance; their coexistence influences health or disease states. The eubiotic vaginal microbiota of reproductive-aged women is composed mostly of various Lactobacillus species (spp.), which exert protective effects via the production of lactic acid, bacteriocins, polysaccharides, peptidoglycans, and hydrogen peroxide (H2O2), lowering pH, raising the viscosity of cervicovaginal mucus, and hampering both the adhesion of cells to epithelial tissue and the entry of HPV. The depletion of beneficial microorganisms could increase the risk of sexually transmitted infections. Emerging therapies involve mucosal, intranasal vaccines, which trigger systemic and mucosal immune responses, thus protecting against HPV-induced tumours. The use of probiotics has also been suggested to affect various biological processes associated with tumourigenesis (inflammation, oxidative stress, apoptosis, proliferation, and metastasis).