Study reveals how diet and probiotics boost melanoma immunotherapy response
Source: Medical Xpress, April 2023
In mice with melanoma, probiotic bacteria travel from the gut and establish in tumors, where they directly stimulate immune cells to make cancer immunotherapy more effective, according to a new study led by University of Pittsburgh researchers.
Published today (April 6) in Cell, the study showed that Lactobacillus reuteri stimulates cancer-killing T cells by secreting a compound called indole-3-aldehyde, or I3A. When the researchers gave mice a diet rich in the amino acid tryptophan—which the bacteria convert to I3A—immunotherapy drugs had a stronger effect on restraining tumor size and prolonging survival. The findings lay the groundwork for clinical trials to test whether I3A treatments or combining probiotics and diet could improve outcomes in melanoma patients undergoing immunotherapy.
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We knew that gut microbes influence immunotherapy response, but there were still big questions about how they do this and whether they act from the gut or if they have to be at the tumor site," said senior author Marlies Meisel, Ph.D., assistant professor in the Department of Immunology at Pitt’s School of Medicine and member of the Cancer Immunology and Immunotherapy Program (CIIP) at UPMC Hillman Cancer Center. “Our study is the first to show that orally administered bacteria increase efficacy of cancer immunotherapy by moving to tumors outside of the gut where they directly impact immune cells in the tumor."