In this month's Did You Know? series, Chief Science Officer Beth DuPriest, PhD discusses how the vaginal biome relates to ovarian or other reproductive cancers. Have a question about vaginal biome science? Submit yours here and your answer may be featured in an upcoming newsletter.
Q: How does the biome relate to ovarian or other reproductive cancers?
A: When people think of infections and cancer, the first to come to mind is the well-described and almost 100% causative role human papillomavirus (HPV) plays with cervical cancer. Viral genes E6 and E7 from HPV interfere with multiple aspects of cervical cell machinery, acting both to spur cell division and to destabilize the genome. Most people will be exposed to HPV at some point in their lives; most clear the virus on their own, but in those who do not, cervical cancer can occur. It is becoming understood that certain vaginal bacteria are associated with better or worse ability to clear HPV infections. Women with cervical intraepithelial neoplasia (CIN) or invasive cervical cancer have been shown to have lower Lactobacillus levels and increased diversity of the vaginal microbiome consistent with bacterial vaginosis (BV).
But did you know that bacterial infections and dysbioses are also associated with other types of female reproductive cancers? While research is in its infancy, there are multiple studies revealing associations between vaginal bacteria and certain types of cancer.
Analysis of several types of ovarian tumors showed that there are bacteria present in these tumors, and that the biome of cancerous tumors differs from those of benign tumors. Perhaps more useful is a study of Japanese women which showed that women with ovarian cancer had cervicovaginal microbiomes that were highly diverse, in contrast with the Lactobacillus-dominant microbiome of pre-menopausal healthy women1. This was detected as early as Stage I. While we don’t yet understand whether these changes are causative or simple associations, finding changes in the vaginal microbiome – as opposed to bacteria in ovarian tumors – means a relatively non-invasive screening tool for ovarian cancer may be developed in the future. Furthermore, another study also revealed that vaginal microbiomes high in Escherichia were more likely to be resistant to platinum-based chemotherapy, a mainstay treatment of metastatic ovarian cancer2.
Endometrial cancer – cancer of the lining of the uterus – is known to be associated with high levels of Atopobium vaginae and Porphyromonas species, especially when combined with high vaginal pH (>4.5)3 and some consider Atopobium to be able to modify host cells in a way favorable to carcinogenesis. Interestingly, use of a Lactobacillus rhamnosus probiotic was able to prevent attachment of biofilm-producing pathogens to endometrial cells in culture and to strongly acidify its environment, suggesting a potential future for probiotics in reducing endometrial cancer risk4.
In all, while our understanding of the connection between ovarian and other reproductive cancers is still in its infancy, it is becoming clear that maintaining a healthy vaginal microbiome can reduce risk.
1. Morikawa A, Kawabata A, Shirahige K, Akiyama T, Okamoto A, Sutani T. Altered cervicovaginal microbiota in premenopausal ovarian cancer patients. Gene. 2022;811:146083. doi:10.1016/j.gene.2021.146083
2. Jacobson D, Moore K, Gunderson C, et al. Shifts in gut and vaginal microbiomes are associated with cancer recurrence time in women with ovarian cancer. PeerJ. 2021;9:e11574. doi:10.7717/peerj.11574
3. Walther-António MRS, Chen J, Multinu F, et al. Potential contribution of the uterine microbiome in the development of endometrial cancer. Genome Med. 2016;8(1):122. doi:10.1186/s13073-016-0368-y
4. Chenoll E, Moreno I, Sánchez M, et al. Selection of New Probiotics for Endometrial Health. Front Cell Infect Microbiol. 2019;9:114. doi:10.3389/fcimb.2019.00114