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.
“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 Dr. Marlies Meisel,
member of the Cancer Immunology
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.
“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 Dr. Marlies Meisel,
member of the Cancer Immunology
and Immunotherapy Programme(CIIP).
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.
“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.”
