Postmenopause as a key factor in the composition of the Endometrial Cancer Microbiome (ECbiome)

Analysing endometrial microbiome: methodological considerations and recommendations for good practice

There is growing evidence that the upper female genital tract is not sterile, harbouring its own microbial communities. However, the significance and the potential effect of endometrial microorganisms on reproductive functions remain to be fully elucidated. Analysing the endometrial microbiome, the microbes and their genetic material present in the endometrium, is an emerging area of study. The initial studies suggest it is associated with poor reproductive outcomes and with different gynaecological pathologies. Nevertheless, studying a low-biomass microbial niche as is endometrium, the challenge is to conduct well-designed and well-controlled experiments in order to avoid and adjust for the risk of contamination, especially from the lower genital tract. Herein, we aim to highlight methodological considerations and propose good practice recommendations for future endometrial microbiome studies.

Porphyromonas somerae Invasion of Endometrial Cancer Cells

Recent evidence suggests an association between endometrial cancer and the understudied bacterial species Porphyromonas somerae. This association was demonstrated in previous work that indicated a significantly enriched abundance of P. somerae in the uterine microbiome of endometrial cancer patients. Given the known associations of the Porphyromonas genus and oral cancer, we hypothesized that P. somerae may play a similar pathogenic role in endometrial cancer via intracellular activity. Before testing our hypothesis, we first characterized P. somerae biology, as current background data is limited. These novel characterizations include growth curves in liquid medium and susceptibility tests to antibiotics. We tested our hypothesis by examining growth changes in response to 17β-estradiol, a known risk factor for endometrial cancer, followed by metabolomic profiling in the presence and absence of 17β-estradiol. We found that P. somerae exhibits increased growth in the presence of 17β-estradiol of various concentrations. However, we did not find significant changes in metabolite levels in response to 17β-estradiol. To study direct host-microbe interactions, we used in vitro invasion assays under hypoxic conditions and found evidence for intracellular invasion of P. somerae in endometrial adenocarcinoma cells. We also examined these interactions in the presence of 17β-estradiol but did not observe changes in invasion frequency. Invasion was shown using three lines of evidence including visualization via differential staining and brightfield microscopy, increased frequency of bacterial recovery after co-culturing, and in silico methods to detail relevant genomic and transcriptomic components. These results underscore potential intracellular phenotypes of P. somerae within the uterine microbiome. Furthermore, these results raise new questions pertaining to the role of P. somerae in the progression of endometrial cancer.

Diet and gut microbiome interactions in gynecologic cancer

Over the last decade, there has been a dramatic surge in research exploring the human gut microbiome and its role in health and disease. It is now widely accepted that commensal microorganisms coexist within the human gastrointestinal tract and other organs, including those of the reproductive tract. These microorganisms, which are collectively known as the "microbiome", contribute to maintaining host physiology and to the development of pathology. Next generation sequencing and multi-'omics' technology has enriched our understanding of the complex and interdependent relationship that exists between the host and microbiome. Global changes in the microbiome are known to be influenced by dietary, genetic, lifestyle, and environmental factors. Accumulating data have shown that alterations in the gut microbiome contribute to the development, prognosis and treatment of many disease states including cancer primarily through interactions with the immune system. However, there are large gaps in knowledge regarding the association between the gut microbiome and gynecologic cancers, and research characterizing the reproductive tract microbiome is insufficient. Herein, we explore the mechanisms by which alterations in the gut and reproductive tract microbiome contribute to carcinogenesis focusing on obesity, hyperestrogenism, inflammation and altered tumor metabolism. The impact of the gut microbiome on response to anti-cancer therapy is highlighted with an emphasis on immune checkpoint inhibitor efficacy in gynecologic cancers. We discuss dietary interventions that are likely to modulate the metabolic and immunologic milieu as well as tumor microenvironment through the gut microbiome including intermittent fasting/ketogenic diet, high fiber diet, use of probiotics and the metabolic management of obesity. We conclude that enhanced understanding of the microbiome in gynecologic cancers coupled with thorough evaluation of metabolic and metagenomic analyses would enable us to integrate novel preventative strategies and adjunctive interventions into the care of women with gynecologic cancers.

New Opportunities for Endometrial Health by Modifying Uterine Microbial Composition: Present or Future?

Current knowledge suggests that the uterus harbours its own microbiota, where the microbes could influence the uterine functions in health and disease; however, the core uterine microbial composition and the host-microbial relationships remain to be fully elucidated. Different studies are indicating, based on next-generation sequencing techniques, that microbial dysbiosis could be associated with several gynaecological disorders, such as endometriosis, chronic endometritis, dysfunctional menstrual bleeding, endometrial cancer, and infertility. Treatments using antibiotics and probiotics and/or prebiotics for endometrial microbial dysbiosis are being applied. Nevertheless there is no unified protocol for assessing the endometrial dysbiosis and no optimal treatment protocol for the established dysbiosis. With this review we outline the microbes (mostly bacteria) identified in the endometrial microbiome studies, the current treatments offered for bacterial dysbiosis in the clinical setting, and the future possibilities such as pro- and prebiotics and microbial transplants for modifying uterine microbial composition.