@science: Researchers at Columbia turned a gut probiotic into a living drug factory — and it eliminated tumors in 43% of treated mice with a single injection.   Chemotherapy and immunotherapy each have a fundamental flaw: chemotherapy floods the entire body, not just the tumor, while immunotherapy can trigger dangerous, body-wide inflammation. Immunologist Nicholas Arpaia's team at Columbia engineered Escherichia coli Nissle, a bacterium already used as a probiotic, to solve both problems at once by concentrating the attack directly inside the tumor.   The bacteria were built to do three things simultaneously. First, they convert a harmless prodrug called 5-FC into active chemotherapy, but only once inside the tumor — turning the tumor itself into the site of drug production rather than exposing the whole body. Second, they produce an IL-15 superagonist, a compound that recruits and activates cancer-fighting immune cells. Third, they release a nanobody that blocks PD-L1, a protein tumors use to disable incoming immune attacks — a localized version of the same mechanism behind major checkpoint-inhibitor cancer drugs.   In mice with established colorectal tumors, a single injection of the engineered bacteria, followed by doses of the prodrug, outperformed either the chemotherapy-producing or immune-stimulating bacteria used alone. Three of seven tumors disappeared completely — a 43% full-response rate — and researchers saw early signs the effect wasn't staying confined to the treated tumor alone.   The approach remains preclinical, tested only in mice, with no human trial data yet. But colorectal cancer rates are climbing, especially among younger adults, for reasons still under investigation — and a treatment engineered to attack only where the tumor lives, rather than the whole body, addresses exactly the tradeoff current therapies still can't avoid.   source: Arpaia, N., et al. (2026). Engineered bacterial consortium for localized chemo-immunotherapy of colorectal cancer. Science Translational Medicine.

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Monday 21 September 2026 20:18:57 GMT