Bacteria from Japanese tree frogs show promise against colorectal cancer in preclinical study
JAIST researchers identify Ewingella americana as a powerful anticancer candidate in mice, but human trials are needed.
A JAIST-led study published in Gut Microbes reports that a gut bacterium isolated from Japanese tree frogs may offer a powerful new approach to treating colorectal cancer in preclinical models. In mouse models of colorectal cancer, researchers administered specific bacteria intravenously and observed tumor responses that suggest potential against the disease, though human testing has not yet occurred.
Researchers screened the intestines of Japanese tree frogs, Japanese fire belly newts and Japanese grass lizards and identified nine bacterial strains with antitumor effects. Of these, Ewingella americana stood out as the most effective. In mice, a single intravenous dose of E. americana eliminated tumors, producing a 100% complete response rate in the study. The results appeared to surpass outcomes reported for several standard therapies in the same preclinical setups, including some forms of immunotherapy and chemotherapy.
The research describes a two-pronged mechanism: the bacteria directly destroy cancer cells and stimulate the immune system to induce apoptosis, the body’s programmed elimination of damaged cells, while avoiding significant inflammation. E. americana preferentially accumulates in tumor tissue and does not disseminate to other organs. In the mouse models, the bacteria were undetectable in the bloodstream after 24 hours, and the body’s inflammatory responses normalized within 72 hours.
Researchers emphasized the safety profile observed in the preclinical setting, noting the lack of the systemic side effects commonly associated with chemotherapy. They described E. americana as having an excellent safety profile within the context of their animal experiments.
Future work will explore delivering the bacteria safely in humans, test efficacy against other cancers such as breast and pancreatic cancer, and investigate whether E. americana can be combined with existing cancer therapies. The team also plans to refine delivery methods, including dose fractionation and direct injections into tumors.
As context, about 150,000 Americans are diagnosed with colorectal cancer each year; 20% of cases in 2019 were in people younger than 55, up from 11% in 1995. In response to this trend, the U.S. Preventive Services Task Force lowered the recommended starting age for average-risk colorectal cancer screening from 50 to 45 in 2021. By 2030, early-onset colorectal cancer is expected to become the leading cancer-related cause of death for people aged 20 to 49 unless major intervention is taken.
The study underscores biodiversity as a potential source of new medical therapies, but the authors cautioned that results in mice do not guarantee similar outcomes in humans. Additional research, including human clinical trials, will be required to determine whether E. americana can be developed into a safe and effective cancer therapy for people.