Scientists at the University of Chicago have genetically rewired a probiotic bacterium to continuously pump an immune-boosting protein inside pancreatic tumors, suppressing cancer growth in mice and opening a new front against one of oncology's most lethal diseases.
Pancreatic ductal adenocarcinoma resists treatment partly because its tumor microenvironment silences the immune cells meant to attack it. Interleukin-2 could reawaken those T cells, but the cytokine degrades quickly in blood, inflames healthy tissue, and accidentally activates regulatory T cells that suppress immune responses rather than amplify them. A team led by Jaehyun Lee and Mark Mimee solved all three problems at once. They modified Bifidobacterium longum, an anaerobic probiotic that naturally colonizes the oxygen-poor cores of solid tumors, to secrete an engineered IL-2 variant called SumIL-2 that preferentially stimulates effector T cells over regulatory ones. The work fits a wider push toward treating disease with programmable living cells.
In mouse models, the bacteria homed to tumors and shrank them. Adding chemotherapy, radiation, or immunotherapy made the effect stronger. The protein engineering behind SumIL-2 is critical here: the variant must activate T cells locally without leaking into healthy tissue, something systemic IL-2 injections have never managed.
No human trials exist yet, and mouse tumors differ considerably from human ones in complexity. But deploying bacteria as in situ drug factories could eventually help reach cancers where conventional delivery systems fall short.