Your Gut Microbes May Help Fight Cancer, New Research Reveals

If you already have have a fever, a festering cut, or a particularly unpleasant case of strep throat, most often your health care provider will have you take antibiotics for a few days. Once you get better, you don’t think about it except your instincts.

According to a study presented this month at a meeting of the American Society for Bone and Mineral Research, researchers found that for melanoma – a serious form of skin cancer that can spread to other organs – taking broad-spectrum antibiotics can accelerate its growth by disrupting the gut microbiota and its influence on the immune system, in particular two types of immune cells called natural killer (NK) cells and T helper (Th1) cells. This research highlights a growing body of evidence that making our gut bugs worse – whether through antibiotics, other medications or lifestyle choices such as diet – is not beneficial to our health and our general well-being.

Here’s the background — A popularized representation or notion of Cancer is that it is ruthless, stubborn and hard to beat and that without medical intervention we are completely defenseless. While not without merit, our bodies are, to some extent, equipped to fight off these renegade mutant cells.

The immune system constantly monitors the body not only for pathogens in the form of viruses or bacteria, but also for anything programmed to do harm, such as cancer. A class of white blood cells called T cells can spot cancer head-on or by organizing a kind of hunting party (Th1 cells are involved in the latter).

NK cells also play a huge role in being the first line of defense against tumor development, says Manoj Chelvanambi, postdoctoral fellow in surgical oncology at the University of Texas MD Anderson Cancer Center. Reverse.

“It’s very well established if you eliminate NK cells, tumors take off and grow extremely quickly,” says Chelvanambi, who was not involved in the study.

NK killer cells, visualized above in white, target virus-infected and cancerous cells. Shutterstock

But cancer cells have an arsenal of evasive maneuvers up their sleeve, like usurping immune cells and reprogramming them or wrapping themselves in stealth camouflage. These tactics make it difficult to remove a tumor without outside help, but that’s where the gut microbiome can step in, says Nadim Ajami, director of scientific research for MD Anderson’s program for innovative microbiome and translational research. . Reverse.

“We also know that one of the functions of the microbiome [what] I call it the sparring partner of the immune system. It’s like a trainer for the immune system,” says Ajami, who was also not involved in the study.

Studies show that the gut microbiome can increase the effectiveness of cancer treatments or lessen the serious side effects of immunotherapy through fecal microbial transplants. On the other hand, when the delicate balance or homeostasis of good and bad bacteria is upset – called dysbiosis – it favors harmful microbes that promote cancer growth.

How they did — Gut microbiome research is still relatively uncharted territory. So what the Emory University researchers, who conducted the new study, wanted to understand is how this vast microbial ecosystem influences tumor growth in bone, which can occur in aggressive melanoma, breast , prostate and many other types of cancer, Subhashis Pal, a postdoctoral fellow at Emory University and the paper’s first author, says Reverse.

“Bone metastases are a common condition where cancer [spreads] down to the bone, and we wanted to explore the possibility that our gut microbiome could regulate the process,” says Pal. “We started exploring all these angles like if we deplete the gut microbiome or create a gut dysbiosis condition by using antibiotics, how does that affect tumor growth?”

To do this, Pal and his colleagues took 12-week-old mice and fed them a cocktail of water containing broad-spectrum antibiotics (which included ampicillin, vancomycin, neomycin sulfate, and metronidazole) for two weeks. They then injected melanoma cells — derived from mice and genetically modified with a bioluminescent protein (meaning the cancer lights up on imaging) — into the hearts of some mice and the bones of others. Broad-spectrum antibiotics were again given for another week for a total of three weeks.

To confirm that the observed effects were strictly associated with the gut microbiome and nowhere else, Emory researchers asked another group of 12-week-old mice to drink water containing two antibiotics that act locally in the gut. and are not absorbed by the rest. of the body – neomycin and bacitracin – for two weeks before injecting melanoma into their mouse hearts and bones. (There was also a control group of mice that drank plain, antibiotic-free water.)

Although antibiotics are important in fighting bacterial infections, taking just one treatment can negatively impact the gut microbiome. Shutterstock

What they found – The researchers found that with prolonged use of broad-spectrum antibiotics scrambling the gut microbiomes of mice, NK and Th1 cell counts were depleted compared to mice that did not receive antibiotics.

“The [number of these] the cells are really shrinking, especially in the gut-associated lymphoid tissues,” says Pal. “The mice’s tumor defense was really weakened, and eventually, we [saw] greater tumor growth.

Sounds interesting, you might be thinking, but what connection do immune cells in the gut have to bone?

Pal and his team saw in mice without antibiotics, there was a spike in the number of NK and Th1 cells in the bone marrow that was not present in mice fed antibiotics. This indicated that in response to melanoma making itself at home where it is not wanted, the gut microbiome recruited and dispatched immune cells to fight in the bone marrow. The researchers found further proof of this when they discovered that well-known immune proteins called CXCL9 and CXCR3 were secreted by bone marrow cells, apparently inviting NK and Th1 cells to come here.

Dig into the details — These findings are just the tip of the microbiome and immune system iceberg, Pal, Chelvanambi and Ajami explain. Much remains to be discovered before we can say whether what is observed in mice will necessarily be the same in humans or in other cancers, let alone the involvement of other immune cells or proteins.

“A more detailed clinical study or using human stool samples or humanized mice would be more beneficial,” Pal says. “We are doing it, but we are still in the preliminary stages.”

Why is it important – Broad spectrum antibiotics are often the mainstay of medical treatment for many cancer patients because therapies such as radiation or chemotherapy weaken the immune system, making patients more susceptible and putting them at high risk for infections bacteria and others.

How long a person needs to take antibiotics may depend on their type of cancer, says Jonathan Peled, a medical oncologist at Memorial Sloan Kettering Cancer Center, who was not involved in the study. For cancer that is easily treated with surgery, patients only need to take antibiotics for a short time, usually before surgery. Medium exposure would occur when a patient undergoing chemotherapy for breast or lung cancer develops fever and infection due to low blood count; to treat the infection, doctors use a week’s worth of antibiotics.

“At the most intense end of things [with] the patients I’ve cared for…may be hematological malignancies for which we’re getting treatments like bone marrow transplants,” Peled says. “These patients sometimes receive weeks of very broad-spectrum antibiotics, they have prolonged hospitalizations for nutritional disorders, and all of this is accompanied by dramatic disturbances in the composition of the microbiome that are essentially different from all the microbiome disturbances observed. in any human context.”

As you can imagine, if broad-spectrum antibiotics carry a cancer risk, we wouldn’t want these life-saving drugs to be part of the problem. Peled says that in recent years, with a better understanding of the gut microbiome, clinicians have reassessed when antibiotics should be used and how to minimize microbial collateral damage.

“[These findings] adding to the feeling that we in clinical practice should always be judicious in our use of antibiotics and use the most targeted antibiotics that are appropriate for that clinical situation for the shortest period of time,” he says.

The fact that it is prolonged we must keep in mind the use of antibiotics which is worrying (these drugs remain our best bet against pathogenic bacteria). In recent years, studies from a group of hospitals in the United States and another from Umeå University in Sweden examining the association between antibiotics and colorectal cancer have found that exposure of killers bacteria for too long (two months or more in the US study, six months or more in the Swedish study) led to an increased risk of cancer in the women studied, most likely through gut dysbiosis.

And after – While this study continues to support the immense promise and potential of the microbiome, there is a long way to go before it goes from the lab bench to the clinic, Golnaz Morad, postdoctoral fellow in surgical oncology also at MD Anderson Cancer Center and not involved in the studies, tells Reverse.

“We really need to focus on the components that are clinically involved in these [cancer] patients, especially since bone metastases are usually a late event,” says Morad. “So the question is how all of these previous treatments affect the microbiome and how is the current treatment [patients] receive [affecting] the microbiome, in addition to all the usual lifestyles and other factors.

In the future, Pal and his colleagues at Emory hope to see what they found in mouse traces with the human gut microbiome and with other malignancies like breast cancer. A longer-term research plan in the next two years is to study the impact of diet on the microbiome and whether we can improve our chances of fighting cancer by changing what we pile on our plates.

Fine dining and cancer-free, indeed.

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