UChicago: Engineered Bacteria Slow Pancreatic Tumors
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- University of Chicago researchers published a study in Science Advances showing BifidoSumIL-2, an engineered strain of Bifidobacterium longum, selectively infiltrated pancreatic tumors, activated cancer-fighting CD8+ T cells, and slowed tumor growth in animal models.
- BifidoSumIL-2 was designed to release SumIL-2, a modified interleukin-2 engineered to preferentially stimulate cancer-killing T cells over regulatory T cells that suppress the antitumor immune response — sidestepping the serious side effects of conventional IL-2 therapy.
- Bifidobacterium longum is an obligate anaerobe that thrives in the low-oxygen core of solid tumors but gets cleared from oxygen-rich healthy tissues, allowing the bacteria to act as microscopic drug factories only where needed.
- Combining BifidoSumIL-2 with chemotherapy, radiotherapy, or anti-PD-L1 immunotherapy produced better tumor control and longer survival than any single treatment alone — a cross-modality synergy researchers called one of the study's most important findings.
- Ralph Weichselbaum, Chair of Radiation and Cellular Oncology at UChicago, framed pancreatic cancer as 'a big unmet medical need' and 'our mountain to climb,' with future plans to test the approach alongside newer treatments including KRAS inhibitors.
- The therapy has not entered human trials; researchers flagged open questions on long-term safety, off-target effects, durability of the immune response, and whether the bacteria could eventually be delivered orally rather than by injection, noting that engineering the anaerobic, slow-growing organism required building new genetic tools.
- The work was funded by the Ludwig Foundation and the National Institutes of Health, with collaborating institutions including UT Southwestern and Tsinghua University in Beijing.
Why it matters: Pancreatic cancer has resisted immunotherapy in part because its tumors create an 'immune-cold' microenvironment, and the UChicago team's BifidoSumIL-2 bypasses that barrier by producing an immune stimulant directly inside the tumor — with preclinical synergy across chemo, radiation, and immunotherapy offering a potential multi-modality weapon. The work remains entirely preclinical, and engineering the slow-growing, anaerobic Bifidobacterium required new genetic tools that don't exist off the shelf, meaning any human application is years away.
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