Breakthrough Study: Probiotic Bacteria Obliterates 43% of Colon Tumors

Scientists have achieved a significant breakthrough in cancer research. They have successfully engineered a common probiotic bacterium into a precision drug-delivery system. This system is capable of attacking colorectal tumors from the inside. The study, published in Science Translational Medicine, used Escherichia coli Nissle 1917—a well-known, non-harmful probiotic strain—to deliver a potent combination of chemotherapy and immunotherapy directly into tumor tissue.

When injected into mice with colorectal cancer, the bacteria bypassed major organs and accumulated inside tumors. Within just five days, there were populations of over one billion bacterial cells per gram of tumor tissue. The researchers engineered the microbes with a “synchronized lysis circuit”. This caused them to burst open once reaching a critical density, releasing their cancer-fighting cargo directly into the tumor environment.

Inside the tumor, the bacteria converted the prodrug 5-fluorocytosine into 5-fluorouracil (a standard chemotherapy agent). At the same time, they released an IL-15 immune stimulant and a PD-L1-blocking nanobody. This supercharged the body’s own immune attack. The results were striking: the treatment caused complete regression in 3 out of 7 colorectal tumors. It also slowed overall tumor growth and even appeared to trigger a broader immune response against untreated tumors.

While this research is still in the early animal-stage, scientists believe that this approach could dramatically reduce the systemic side effects of traditional cancer treatments. This is due to its ability to target tumors with pinpoint precision. Further human trials will be needed to confirm safety and efficacy.

Source: Medical Dialogues – Medical Bulletin, September 25, 2026