There is growing evidence to suggest the gut microbiome may play an important role in the pathogenesis of both obesity and cancer. Two divisions of bacteria predominate in the gut in humans and mice, Bacteroidetes and Firmicutes, and the relative ratio of these two divisions is dramatically affected by obesity, such that Bacteroidetes levels decrease and Firmicutes levels increase.5 The change in the microbial environment leads to a greater ability to harvest dietary energy, which would be conducive to cancer development.
The microbiome and gynecologic cancers
Dr. Emma C. Rossi
The presence and relative abundance of bacterial species in the vagina are affected by unique factors such as hormonal contraception, pregnancy, and menopause. There are researchers investigating alterations in the microbiome of the vagina and implications in persistence of high-risk human papillomavirus infections and HPV-induced carcinogenesis. There were significant differences found in the composition of the vaginal microbiota in healthy women, compared with women with low-grade squamous intraepithelial neoplasm and high-grade squamous intraepithelial neoplasm.6
Conceivably, the subsequent clinical questions are: Can we apply this data to diagnose women at risk for dysplasia or can we alter the vaginal microbiome to impact the clearance rate of the HPV virus in susceptible or infected women to decrease the long-term risk of cervical dysplasia or malignancy?
The upper reproductive tract in women – the uterus, fallopian tubes, and ovaries – had been presumed to be a sterile environment. However, we know that bacteria have been isolated in the pre- and postmenopausal uterus of healthy women. Therefore, there also are investigators seeking to establish the microbiome of normal uteri to accurately compare it with malignant uteri. Notably, there also is interest in how treatments for cancer – chemotherapy and radiation – ultimately can affect a woman’s vaginal and gut microbiome.
Currently, microbiome research has an expansive range. Women will greatly benefit from research seeking to define improved prevention, diagnosis, and treatment based on alterations of the microbiome for common gynecologic premalignant and malignant conditions.
Dr. Hawkins is a fellow of gynecologic oncology and Dr. Rossi is an assistant professor in the division of gynecologic oncology at the University of North Carolina at Chapel Hill. They had no conflicts of interest to disclose.
References
1. “ ’Ome Sweet ’Omics – a genealogical treasury of words,” by Joshua Lederberg, The Scientist, Apr 2, 2001.
2. Genome Res. 2009 Dec;19(12):2317-23.
3. “Normal Human Microbiota,” Jawetz, Melnick & Adelberg’s Medical Microbiology, 27th edition (New York, NY: McGraw-Hill, 2016).
4. Nature. 2012 Jun 13;486(7402):207-14.