The use of far-ranging antibiotics in mice with malignant melanoma, a severe type of skin cancer, increased their metastatic bone growth. This is likely because the drugs lessened the intestinal flora in mice and weakened the immune response, finds a new study by researchers at Emory University
The findings emphasize the importance of gut microbiome in overall health, and suggests that gastrointestinal effects need to be carefully weighed when antibiotic therapies are used for treating cancer or other diseases, stated one of the authors of the study.
“Any disease or therapy that has downside on the gut microbiome could have a negative impact on health,” stated the researchers who presented the report at the annual meeting of American Society of Bone and Mineral.
“The study found that gut microbiome controls the advancement of melanoma bone lesions in mice by improving the number of intestinal natural-killer cells and T helper cells, and promotes their migration to the tumor site,” stated the researcher.
Meanwhile, the use of oral antibiotics reduced the gut microbiome and limits the population of intestinal Th1 cells and NK cells. This increased vulnerability of mice to tumor growth. The melanoma tumor burden was higher for this population than control mice with intact gut microbiomes.
Clinically, osteolytic bone metastasis develops as a complication of malignant melanoma. Using antibiotics to lessen the gut microbiome of mice would influence their intestinal immune cells, and thus alter immune response resulting in increased bone metastasis, hypothesized researchers. Injecting B16-F10 melanoma cells into the bones and hearts of mice that had been treated with far-ranging antibiotics resulted in increased bone metastatic growth, compared to control mice that did not receive, as predicted.