Immunotherapy has helped treat many cancers, but pancreatic cancer still resists most treatments. The tumor creates a cold environment that blocks immune cells.
Scientists at the University of Chicago built a special strain of the friendly gut bacterium Bifidobacterium longum. They named it BifidoSumIL-2 and programmed it to bring an immune‑boosting protein straight into the tumor.
In mouse experiments, the bacteria slowed tumor growth. The effect grew stronger when the researchers added chemotherapy, radiation, or other immunotherapy drugs.
Using Bacteria to Deliver Cancer Therapy
"Pancreatic cancer is a big unmet need," said Dr. Ralph Weichselbaum, a cancer specialist at Chicago. The team gave the bacteria a version of interleukin‑2 (IL‑2), a molecule that tells T cells to attack cancer.
Normal IL‑2 can cause harmful side effects and can also wake up cells that calm the immune response. To avoid this, they used a tweaked form called SumIL‑2, which mainly activates the cancer‑fighting T cells.
They placed SumIL‑2 inside the bacterium so the drug stays inside the tumor instead of spreading through the whole body.
Creating this therapy needed experts in microbiology, synthetic biology, oncology, and immunology to work together.
Why Bifidobacterium Can Target Tumors
Bifidobacterium loves places with little oxygen. Tumors, especially pancreatic ones, have low‑oxygen zones, while healthy tissue has more oxygen. This makes the bacteria grow mainly inside tumors.
When injected into the bloodstream, the bacteria disappear from oxygen‑rich healthy areas but thrive in the tumor’s dark spots, turning the tumor into a tiny drug factory.
The bacterium is already known to be safe in foods like yogurt, so it has a good safety record in early tests.
Engineering Challenges
Working with Bifidobacterium is tough. It grows slowly, hates oxygen, and has fewer genetic tools than common lab bacteria such as E. coli. The researchers spent much time just learning how to edit its DNA reliably.
Stronger Results With Combination Treatments
Animal studies showed that BifidoSumIL‑2 gathered inside tumors, woke up immune cells, and slowed cancer growth. It also increased the number of CD8+ T cells that kill cancer.
The biggest improvements happened when the bacteria were used together with standard chemo, radiation, or anti‑PD‑L1 drugs. The combined approach gave better tumor control and longer survival.
Although promising, the therapy has not yet been tried in people. Future work will check long‑term safety, possible effects outside the tumor, how long the immune boost lasts, and whether the bacteria could be given as a pill instead of an injection.
The Growing "Bugs as Drugs" Approach
This study adds to a rising interest in using engineered microbes as tiny medicine factories. By sending probiotics straight to tumors, scientists hope to concentrate powerful treatments where they are needed most while lowering side effects.
The research was funded by the Ludwig Foundation and the National Institutes of Health.