Researchers at The University of Texas MD Anderson Cancer Center announced on July 31 that they have identified a method to reshape the gut microbiome, potentially enhancing the delivery of certain chemotherapies to tumors. The study, published in Nature Materials and led by Betty Kim, M.D., Ph.D., Wen Jiang, M.D., Ph.D., and Jennifer Wargo, M.D., found that altering gut bacteria with a short course of antibiotics in preclinical models roughly doubled the circulation time of nanoparticle-based chemotherapy. This approach increased drug accumulation in tumors and improved survival across multiple cancer types.
The research was conducted as part of a collaborative project through the Platform for Innovative Microbiome and Translational Research (PRIME-TR). According to Jiang, "For decades, scientists have tried to address how aggressively the liver filters out nanomedicine by redesigning the drugs themselves. Our research shows that the host's biology, specifically the gut microbiome, is just as important as the particle design. This is the first study to demonstrate that the gut microbiome can directly impact chemotherapy, opening up an entirely new strategy for boosting cancer treatment."
Nanoparticle-based chemotherapy involves drugs packaged inside microscopic carriers such as liposomes or albumin particles and is used for cancers including breast, ovarian, and pancreatic. Most therapy does not reach tumors because immune cells in the liver known as Kupffer cells clear drug particles from circulation. The study found that chemical signals from gut bacteria influence these liver cells via bile acids—molecules produced when bacteria process bile.
When researchers administered metronidazole—an antibiotic—to selectively reduce certain gut bacteria in preclinical models, bile acid levels dropped and Kupffer cells shifted into a "quiet" state. As a result, fewer nanomedicine particles were cleared by these cells; this extended circulation time allowed more drug accumulation in tumors and led to significantly slowed tumor growth with prolonged survival across colon, breast, melanoma, and pancreatic cancers.
To confirm whether changes were due to alterations in microbiota rather than residual antibiotic effects alone, fecal microbiota transplantation (FMT) was performed using microbial communities from antibiotic-treated donors into germ-free recipients; these recipients showed similar improvements without detectable antibiotic presence. Wargo said, "Hepatic clearance is not a fixed physiological constraint but a dynamic state that can be modulated through the microbiome... By understanding how the microbiome shapes drug delivery we can begin thinking about chemotherapy not just as a drug-tumor interaction but as a drug-microbiome-host interaction which changes how we might design treatment plans for patients in future."
