Potential contribution of the uterine microbiome in the development of endometrial cancer

Abstract

Background: Endometrial cancer studies have led to a number of well-defined but mechanistically unconnected genetic and environmental risk factors. One of the emerging modulators between environmental triggers and genetic expression is the microbiome. We set out to inquire about the composition of the uterine microbiome and its putative role in endometrial cancer.

Methods: We undertook a study of the microbiome in samples taken from different locations along the female reproductive tract in patients with endometrial cancer (n = 17), patients with endometrial hyperplasia (endometrial cancer precursor, n = 4), and patients afflicted with benign uterine conditions (n = 10). Vaginal, cervical, Fallopian, ovarian, peritoneal, and urine samples were collected aseptically both in the operating room and the pathology laboratory. DNA extraction was followed by amplification and high-throughput next generation sequencing (MiSeq) of the 16S rDNA V3-V5 region to identify the microbiota present. Microbiota data were summarized using both α-diversity to reflect species richness and evenness within bacterial populations and β-diversity to reflect the shared diversity between bacterial populations. Statistical significance was determined through the use of multiple testing, including the generalized mixed-effects model.

Results: The microbiome sequencing (16S rDNA V3-V5 region) revealed that the microbiomes of all organs (vagina, cervix, Fallopian tubes, and ovaries) are significantly correlated (p < 0.001) and that there is a structural microbiome shift in the cancer and hyperplasia cases, distinguishable from the benign cases (p = 0.01). Several taxa were found to be significantly enriched in samples belonging to the endometrial cancer cohort: Firmicutes (Anaerostipes, ph2, Dialister, Peptoniphilus, 1-68, Ruminococcus, and Anaerotruncus), Spirochaetes (Treponema), Actinobacteria (Atopobium), Bacteroidetes (Bacteroides and Porphyromonas), and Proteobacteria (Arthrospira). Of particular relevance, the simultaneous presence of Atopobium vaginae and an uncultured representative of the Porphyromonas sp. (99 % match to P. somerae) were found to be associated with disease status, especially if combined with a high vaginal pH (>4.5).

Conclusions: Our results suggest that the detection of A. vaginae and the identified Porphyromonas sp. in the gynecologic tract combined with a high vaginal pH is statistically associated with the presence of endometrial cancer. Given the documented association of the identified microorganisms with other pathologies, these findings raise the possibility of a microbiome role in the manifestation, etiology, or progression of endometrial cancer that should be further investigated.

Keywords: 16S rDNA; Atopobium; Endometrial cancer; Microbiome; Porphyromonas; Uterus.

Fig. 1

Endometrial microbiome across cohorts. Only taxa present at a minimum of 5 % relative frequency in at least one participant are shown for graphical clarity. Taxa color scheme reflects abundance relative to each patient (darker coloration represents higher abundance). Meno/Menometrorrhagia menorrhagia/menometrorrhagia, Dysme dysmenorrhagia/pelvic pain, W/Aty with atypia, Muci mucinous, Squa squamous, Carcino carcinosarcoma, Hyper hyperplasia

Fig. 2

Vaginal/cervical (lower tract) microbiome across cohorts. Only taxa present at a minimum of 5 % relative frequency in at least one participant are shown for graphical clarity. Taxa color scheme reflects abundance relative to each patient (darker coloration represents higher abundance). Dysme dysmenorrhagia/pelvic pain, W/Aty with atypia, Muci mucinous, Squa squamous, Hyper hyperplasia

Fig. 3

Fallopian tube microbiome across cohorts. Only taxa present at a minimum of 5 % relative frequency in at least one participant are shown for graphical clarity. Taxa color scheme reflects abundance relative to each patient (darker coloration represents higher abundance). Meno/Menometrorrhagia menorrhagia/menometrorrhagia, Dysme dysmenorrhagia/pelvic pain, W/o Aty without atypia, W/Aty with atypia, Muci mucinous, Squa squamous, Hyper hyperplasia

Fig. 4

Ovarian microbiome across cohorts. Only taxa present at a minimum of 5 % relative frequency in at least one participant are shown for graphical clarity. Taxa color scheme reflects abundance relative to each patient (darker coloration represents higher abundance). Dysme dysmenorrhagia/pelvic pain, W/Aty with atypia, Squa squamous, Hyper hyperplasia

Fig. 5

α-diversity comparison between different disease states in the endometrial microbiome. Error bars represent the standard errors. a Observed OTU number. b Shannon index

Fig. 6

Ordination plot based on unweighted UniFrac distance depicting the relationship between different disease states. Each point represents a sample and is colored by sample group

Fig. 7

Maximum likelihood phylogenetic tree of the V3-V5 16S rDNA region of the recovered Porphyromonas sp. ^a Recovered from children with atopic dermatitis. ^b Recovered from buffaloes with postpartum endometritis. ^c Recovered from Holstein dairy cows with postpartum metritis. Produced with FASTTREE

Fig. 8

ROC curve for Atopobium vaginae and Porphyromonas sp. presence in the lower reproductive tract (vagina/cervix) and disease status (benign vs. endometrial cancer)

Fig. 9

Example collections. Only taxa present at more than 5 % relative frequency per sample are shown for graphical clarity. a Patient B02. b Patient H72. c Patient EC19