The role of microbiota in epithelial ovarian cancer: a scoping review

Abstract

Objective: The objective of this review was to examine the comprehensive role of microbiota in epithelial ovarian carcinogenesis. Methods: A scoping review method was used, and relevant databases were searched using combinations of key terms. Human and animal studies were selected that met inclusion criteria and critical appraisal tools were used to assess study quality. Results: A total of 10 international studies (human n = 8; animal n = 2) were included with total samples sizes varying from 16 to 580. Mean/median ages of women with epithelial ovarian cancer (EOC) were 50.5 to 66 years, and controls were 47.3 to 56 years. Compared to the ovaries and fallopian tubes of women without disease, tissue collected from women with EOC were characterized by differing proportions of bacterial phyla including Actinobacteria, Bacteroidetes, Chlamydiae, Firmicutes, and Proteobacteria. Intestinal depletions and reduced diversity of genera Lactobacillus accelerated ovarian tumor growth in animal models. Cytomegalovirus and human papillomavirus types 6, 16, 18, and 45 had a significantly higher prevalence in women with disease and represented up to 70% of cases with high-grade serous ovarian carcinoma. Colonized bacteria were detected in fallopian tubes, peritoneal fluid, and ovarian tissue similar to that of commensal GI tract and vaginal bacteria. Conclusion: The EOC microenvironment harbors diverse microbes. Due to the heterogeneity of microbiota identified between studies, additional research is needed to reconcile findings and ascertain clinical applicability. Future investigations should also examine potential associations between EOC tumor, gut, and vaginal microbiota, patient symptoms throughout disease, chemotherapy response, recurrence, and survival.