The Female Reproductive Tract Microbiome and Cancerogenesis: A Review Story of Bacteria, Hormones, and Disease Original paper

What was studied?

This review paper explores the relationship between the female reproductive tract microbiome and cancerogenesis. It highlights how bacterial communities within the female reproductive system, especially in the cervix and vagina, influence the development of gynecological cancers, including endometrial, cervical, and ovarian cancers. The study discusses the dynamic changes in the microbiome, its association with carcinogenesis, and the potential role of dysbiosis—an imbalance in the microbiota—in cancer development. Specific bacteria, such as Lactobacillus species, and their protective roles in maintaining a healthy microbiome are emphasized. Conversely, microbial dysbiosis with an overgrowth of pathogenic bacteria may facilitate the progression of cancer by promoting chronic inflammation and genetic alterations in cells.

Who was studied?

The review addresses various studies that include both human and animal models. It incorporates research on the microbial composition of the lower and upper female reproductive tracts, including the vagina, cervix, endometrium, and ovaries. The studies also discuss the effects of microbial imbalances on women of different age groups and health conditions, including those with gynecological cancers, endometriosis, and those undergoing treatments like chemotherapy and radiotherapy. Additionally, the paper refers to molecular techniques like 16S ribosomal sequencing, which has enabled researchers to categorize the vaginal microbiome into distinct community state types, shedding light on the relationship between specific microbial populations and disease states.

Most important findings

Several significant findings emerged from this review. First, a healthy vaginal microbiome is predominantly composed of Lactobacillus species, which help maintain a low pH environment that prevents the overgrowth of harmful bacteria. However, dysbiosis, characterized by a decrease in Lactobacillus spp. and an increase in anaerobic bacteria, is linked to an increased risk of gynecological cancers. The paper also highlights the role of estrogen in modulating the microbiome, as higher estrogen levels promote the growth of Lactobacillus spp., while fluctuations in estrogen, such as those seen in menopause, can lead to microbial imbalances. Furthermore, specific bacteria like Chlamydia trachomatis, Mycoplasma genitalium, and Fusobacterium spp. are associated with the persistence of infections that increase cancer risk. Notably, Lactobacillus species seem to have a protective effect, with a higher prevalence in healthy women compared to those with gynecological cancers. However, bacteria such as Acinetobacter spp., Proteobacteria, and Brucella spp. have been found in ovarian cancer tissues, suggesting that they may play a role in carcinogenesis.

Key implications

The findings underscore the growing importance of the microbiome in the development and progression of gynecological cancers. Understanding the role of microbial communities in cancerogenesis could lead to new preventative and therapeutic strategies, such as microbiome modulation through probiotics, dietary interventions, or microbiome transplantation. The study also points to the potential of using the microbiome as a biomarker for early detection of cancer or assessing the efficacy of cancer treatments. Further research is needed to clarify the causal relationships between specific microbial species and cancer, as well as how treatments like chemotherapy or immunotherapy may influence the female reproductive tract microbiome.