Scientists at Japan’s Advanced Institute of Science and Technology have found a tiny living organism that can fight cancer. The bacterium lives in the gut of the Japanese tree frog (Dryophytes japonicus) and showed strong anti‑cancer effects when injected into mice.
Instead of changing a person’s gut bacteria or using fecal transplants, the researchers grew the bacteria in the lab and delivered them directly into the bloodstream. They tested 45 bacterial strains from frogs, fire‑belly newts, and grass lizards. Nine of these strains slowed tumor growth, and one – Ewingella americana – worked best.
Single Dose Erased Tumors
In mice with colon cancer, one intravenous dose of E. americana removed all visible tumors. The treatment gave a 100 % complete‑response rate, beating the standard drugs they compared it to, such as anti‑PD‑L1 antibodies and liposomal doxorubicin.
How the Bacteria Attack Cancer
The bacterium uses two tactics. First, it grows fast inside the low‑oxygen pockets that are common in tumors. In just 24 hours, its numbers rose about 3,000‑fold, directly damaging cancer cells.
Second, the bacteria call in the body’s immune soldiers. T cells, B cells, and neutrophils rush to the tumor, releasing signals like TNF‑α and IFN‑γ that help kill cancer cells.
Why It Targets Tumors, Not Healthy Tissue
E. americana mostly stays inside tumors for three reasons:
- Tumors have little oxygen, which the bacterium loves.
- Cancer cells make a protein called CD47 that blocks local immune attacks, giving the bacteria a safe spot.
- Leaky blood vessels in tumors let the bacteria slip from the bloodstream into the tumor.
- Changes in tumor metabolism provide extra food for the bacteria.
Safety Checks
After injection, the bacteria cleared from the blood quickly—about a 1.2‑hour half‑life—and disappeared completely within a day. No bacteria were found in the liver, spleen, lungs, kidneys, or heart.
Only mild, short‑lived inflammation was seen, and it returned to normal after three days. Over a 60‑day watch period, the mice showed no long‑term toxicity.
Looking Ahead
This study proves that a naturally occurring bacterium can be used as a cancer therapy in animals. Future work will test the approach on other solid tumors such as breast, pancreatic, and melanoma. Researchers also plan to try different dosing schedules, direct injections into tumors, and combinations with existing chemotherapy or immunotherapy.
Glossary
- Facultative anaerobic: Bacteria that can grow with or without oxygen, allowing them to thrive in tumor‑low‑oxygen zones.
- Complete response (CR): When a treatment makes all detectable tumors disappear.
- Immune checkpoint inhibitor: Drugs that lift the “brakes” cancer puts on the immune system, letting immune cells attack tumors.
- CD47: A “don’t eat me” signal on many cancer cells that helps them avoid immune destruction.