A research team of Prof. Eijiro Miyako at the Japan Advanced Institute of Science and Technology (JAIST) has discovered that the bacterium Ewingella americana , isolated from the intestines of Japanese tree frogs ( Dryophytes japonicus ), possesses remarkably potent anticancer activity. This groundbreaking research has been published in the international journal Gut Microbes .
While the relationship between gut microbiota and cancer has attracted considerable attention in recent years, most approaches have focused on indirect methods such as microbiome modulation or fecal microbiota transplantation. In contrast, this study takes a completely different approach: isolating, culturing, and directly administering individual bacterial strains intravenously to attack tumors—representing an innovative therapeutic strategy.
The research team isolated a total of 45 bacterial strains from the intestines of Japanese tree frogs, Japanese fire belly newts ( Cynops pyrrhogaster ), and Japanese grass lizards ( Takydromus tachydromoides ). Through systematic screening, nine strains demonstrated antitumor effects, with E. americana exhibiting the most exceptional therapeutic efficacy.
Remarkable Therapeutic Efficacy
In a mouse colorectal cancer model, a single intravenous administration of E. americana achieved complete tumor elimination with a 100% complete response (CR) rate. This dramatically surpasses the therapeutic efficacy of current standard treatments, including immune checkpoint inhibitors (anti-PD-L1 antibody) and liposomal doxorubicin (chemotherapy agent) ( Figure 1 ).
Dual-Action Anticancer Mechanism
E. americana attacks cancer through two complementary mechanisms ( Figure 2 ):
Tumor-Specific Accumulation Mechanism
E. americana selectively accumulates in tumor tissues with zero colonization in normal organs. This remarkable tumor specificity arises from multiple synergistic mechanisms:
Excellent Safety Profile
Comprehensive safety evaluation revealed that E. americana demonstrates:
This research has established proof-of-concept for a novel cancer therapy using natural bacteria. Future research and development will focus on:
This research demonstrates that unexplored biodiversity represents a treasure trove for novel medical technology development and holds promise for providing new therapeutic options for patients with refractory cancers.
###
Facultative Anaerobic Bacteria : Bacteria capable of growing in both oxygen-rich and oxygen-depleted environments, enabling selective proliferation in hypoxic tumor regions.
Complete Response (CR) : Complete tumor elimination confirmed by diagnostic examination following treatment.
Immune Checkpoint Inhibitor : Drugs that release cancer cell-mediated immune suppression, enabling T cells to attack cancer cells.
CD47 : A cell surface protein that emits "don't eat me" signals; cancer cells overexpress this to evade immune attack.
Title : Discovery and characterization of antitumor gut microbiota from amphibians and reptiles: Ewingella americana as a novel therapeutic agent with dual cytotoxic and immunomodulatory properties
Authors : Seigo Iwata, Nagi Yamashita, Kensuke Asukabe, Matomo Sakari, Eijiro Miyako*
Journal : Gut Microbes
DOI : 10.1080/19490976.2025.2599562
This research was supported by:
Gut Microbes
Discovery and characterization of antitumor gut microbiota from amphibians and reptiles: Ewingella americana as a novel therapeutic agent with dual cytotoxic and immunomodulatory properties
10-Dec-2025