How does your Vaginal Microbiome Affect your Cancer Risk?

When you hear about the vaginal microbiome (VMB), your first thought may be the role it plays in stuff like yeast infections or bacterial vaginosis (BV). But with improved research, we’re uncovering more of the VMB’s long-term effects, like its role in a healthy pregnancy and delivery. The complex community of organisms living in your vagina even plays a part in your risk of developing certain non-infectious conditions—like cancer. 

That sounds scary, but it’s actually pretty simple. Your vaginal microbiome is a natural line of defense that fends off pathogens, stuff like sexually transmitted infections (STIs). That includes viruses like Human Papillomavirus (HPV). 

What is HPV?

HPV is a viral infection most commonly acquired sexually… In fact, it’s the most common STI. It actually isn’t just one virus, but a whole group of them, and not all of them are particularly dangerous. Almost 100% of sexually active people will acquire a kind of HPV at some point, and most of these infections will just be cleared away naturally by the immune system. Some types of this virus cause no symptoms, some cause genital warts, but some may trigger changes to cell behavior. These types of HPV are known as ‘high-risk’, because they make changes to regulation of host cell replication. Those altered cells will keep dividing and multiplying long after they’re supposed to shut down and die off. 

This is what can eventually lead to cancer, including anal, vulval, vaginal, penile and even head and neck cancers. But most commonly, infection with a particular kind of HPV can lead to cervical cancer. (Check out this article for more details on how to look out for and handle HPV infection). Not only does a VMB imbalance lead to a higher likelihood of becoming infected with a high-risk HPV in the first place, but it’s also associated with HPV sticking around longer, giving it more of a chance to cause cellular changes. 

How to protect yourself

The good news is that we’ve got some pretty good solutions to keep us safe. One is, of course, taking good care of your vaginal health. That includes practicing safe sex and disturbing your protective vaginal microbiome as little as possible—no douching required! But we all know that sometimes, no matter how hard you try, something just crops up. Stress, a laundry detergent change, a course of antibiotics, and BAM! We’re dealing with BV. This is the point at which I am always grateful for my additional piece of protection: my HPV vaccine. This vaccine can be given to anyone regardless of gender, and is most effective when given proactively—that is, before someone becomes sexually active. In countries where HPV vaccination is widespread we see a substantial reduction in HPV-caused cervical cancer, so it really does work to keep you safe.

Your vaginal microbiome and other forms of cancer

While HPV is currently the most well-studied genital microbe with a link to cancer, new research is uncovering more relationships between our VMB and cancer risks. Some studies have found a tentative link between certain species in the VMB—Atopobium vaginae and Porphyromonas species, and the development of endometrial cancer or cancer of the lining of the uterus. These bacteria were found in the upper reproductive tract of study participants with either benign or cancerous endometrial growths, and found that people with those two bacterial species, plus a less acidic vagina than normal, were at higher risk of their growths being cancerous. While we’re not sure yet why exactly this is the case, this kind of work does provide a useful potential tool for future screening for this kind of cancer. 

The organisms in your vaginal microbiome are also always producing chemicals—it’s part of what helps them fight off bad bacteria and viruses. But in cases where the VMB is thrown out of balance, these products will change. These chemicals are interacting with the cells in your reproductive tract, and may also influence the way these cells talk to each other, called cell-signaling behavior. Your VMB products can have an impact outside of the vagina, too—we used to think the ovaries and the uterus were sterile areas of the body, but they actually have their own microbiomes too, connected to and influenced by the VMB. So if these bacteria and their products change, cell-signalizing changes can happen in the uterus or the ovaries. Your ovaries especially play a large role in hormone regulation, so if cell behavior changes here, it could cause a hormonal shift. Hormones play a big role in overall health, but can also in the development of gynecological cancers. Long-term elevated levels of estrogen and progesterone, which are made by the ovaries, are known to increase the risk of breast cancer, for example. Although all of these relationships are still just beginning to be explored, it’s clear that the link between your good bugs and long term health is significant. 

Take care of your vaginal microbiome and it will take care of you

This relationship between your VMB, its products, and the health of your reproductive tissues is a pretty big deal. Research has found that when the reproductive tract’s healthy acidity is lowered and species take over that aren’t normal, inflammation increases. The reasons an altered VMB leads to inflammation are complex, but put simply, it’s because your immune system is reacting to those less familiar bacteria and trying to ‘fix’ the problem. This is the same reason a cut gets red and puffy around the edges as its healing—inflammation is your body’s response to injury and infection. 

We know from decades of research that inflammation plays a key role in the development of many kinds of cancers—there are lots of different pathways for this, but generally it comes down to the fact that your body’s inflammatory response is really just a bunch of different kinds of chemicals. These chemicals are interacting with your cells to alter their behavior to help you heal—making them divide faster to repair damaged tissue or killing them off faster if they’re not behaving properly. This is mostly a really good thing! But if inflammation becomes long-term this behavior modification can go a little too far, changing cell behavior enough that those cells become precancerous or cancerous. Pelvic inflammatory disease (PID), for example, results from long-term infection of the reproductive tract and may increase your risk of ovarian cancer.

The flip side of all this is that just as disturbances to the VMB can leave you vulnerable, a robust and well-balanced VMB can protect you, and even bolster your resilience to other health issues. Those healthy bacteria and their good, acidic chemical products help keep reproductive tissues functioning as they should, and decrease inflammation. 

When it comes to something like cancer treatment, the medical community is starting to involve the microbiome much more. Research has shown that the body’s various microbial communities can interfere with chemotherapy, altering the way your body processes certain drugs. But this also means that the interactions of bacteria and therapeutic drugs can be leveraged to make cancer therapies more effective, more targeted, and less damaging to healthy cells. It’s possible that in the future, treatment of gynaecological cancers could include a probiotic aspect, or the addition of good bacteria to the reproductive tract, to supplement chemotherapy or radiation, but this hasn’t yet been tested in humans. 

Aside from the very well-studied relationship between the vaginal microbiome, HPV infection, and cancer risk, all of these connections are just in the very early stages of being explored. Especially as we learn more, it’s becoming increasingly obvious how important it is to:

1. Get acquainted with your own microbiome’s balance
2. Understand how your VMB contributing to your vagina’s pH and inflammation levels
3. Become informed on how you may be able to support your VMB
   

This knowledge can empower you with the tools you need to help your VMB protect you, keep your reproductive tissue nice and healthy, and even potentially help your healthcare team personalize any treatments you may need.