Home / News / World /  Antibiotics worsen skin cancer by depleting gut microbiome: What new study says

A new study conducted by researchers at Emory University in Atlanta states that the use of broad-spectrum antibiotics in mice with malignant melanoma, an aggressive form of skin cancer, accelerated their metastatic bone growth. The research noted that this likely happened due to the drugs depleting the mice's intestinal flora and weakening their immune response.

Subhashis Pal, Ph.D., a postdoctoral fellow in endocrinology at the Emory University School of Medicine said that the findings underscore the importance of the gut microbiome in overall health and suggest that doctors should carefully weigh the gastrointestinal effects when they use antibiotic therapies while treating cancer or other diseases. 

He said, “any disease or therapy that harms the gut microbiome could have a negative impact on our health. In our study we found that the gut microbiome restrains the progression of melanoma bone lesions in mice by promoting the expansion of intestinal natural-killer (NK) cells and T helper (Th1) cells and enhancing their migration to the tumor site."

Dr Pal highlighted that “using oral antibiotics depleted the gut microbiome and reduced the population of intestinal NK cells and Th1 cells. This made the mice more vulnerable for tumor growth. They had a higher melanoma tumor burden than control mice whose gut microbiomes were intact."

Impact of antibiotics on gut microbiome:

It is important to note that osteolytic bone metastasis is a complication of malignant melanoma. The researchers hypothesized that using antibiotics to deplete the gut microbiome of mice would affect their intestinal immune cells and thus alter their immune response, leading to accelerated bone metastasis. They injected B16-F10 melanoma cells into the hearts and bones of mice that had been treated with broad-spectrum antibiotics. As predicted, the antibiotic injections accelerated bone metastatic growth in those mice, compared with control mice that had not received the shots, as per ANI report.

The study revealed the mechanism for the metastatic growth of melanoma. Flow cytometric analysis of Peyer's patches and bone-marrow cells within tumor lesions revealed that microbiome depletion prevented the melanoma-induced expansion of intestinal NK and Th1 cells and their migration from the gut to tumor-bearing bones. Direct measurement of NK and Th1 cells migration using Kaede mice, a strain expressing a photo-convertible fluorescent protein that allows direct tracking of intestinal lymphocytes, revealed that antibiotics decreased by about eightfold the migration of NK and Th1 cells from the gut to the tumor site.

Why maintaining healthy gut microbiome matters:

This study strongly indicates that microbiome modifications induced by antibiotics might have negative clinical consequences not only with melanoma, but with other diseases as well, Dr. Pal said. “For example, inflammatory bowel disease, or other gut conditions that create inflammation, can lead to increased Th17 cells, TNF producing cell numbers in the gut, which ultimately has a negative impact on our bone health. Similarly, we have seen that in a murine model of surgical menopause, reduced levels of estrogen cause bacterial metabolites to pass more easily through the gut barrier and hyperactivate the immune system. As a result, the number of intestinal and bone marrow cytokine producing T cells rises, largely contributing to the development of bone loss."

In order to address the issue, Dr Pal said “we should be very much careful with our gut microbiome, and of the unforeseen adverse consequence of antibiotic regimens. Conversely, probiotics can play a major role to maintain healthy gut microbiome, and better overall health."

(With inputs from ANI)

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