Frog-derived bacteria offer dual-action anticancer effects and high safety: A groundbreaking discovery from Japan
A research team led by Professor Eijiro Miyako at the Japan Advanced Institute of Science and Technology (JAIST) has uncovered a remarkable discovery in the field of cancer treatment. The team's research, published in the international journal Gut Microbes, highlights the potential of a unique bacterium, Ewingella americana, isolated from the intestines of Japanese tree frogs (Dryophytes japonicus).
The focus on gut microbiota and its connection to cancer has grown significantly in recent years, with most studies focusing on indirect methods like microbiome modulation or fecal microbiota transplantation. However, this study takes a bold and innovative approach by directly administering individual bacterial strains to attack tumors. The team isolated 45 bacterial strains from the intestines of Japanese tree frogs, Japanese fire belly newts (Cynops pyrrhogaster), and Japanese grass lizards (Takydromus tachydromoides), and identified nine strains with antitumor effects, with E. americana showing the most promise.
Exceptional Therapeutic Efficacy
In a mouse colorectal cancer model, a single intravenous administration of E. americana resulted in complete tumor elimination with a 100% complete response (CR) rate. This outcome surpasses the efficacy of current standard treatments, including immune checkpoint inhibitors (anti-PD-L1 antibody) and liposomal doxorubicin (chemotherapy agent).
Dual-Action Anticancer Mechanism
E. americana employs two complementary mechanisms to combat cancer:
- Direct Cytotoxic Effect: As a facultative anaerobic bacterium, E. americana selectively accumulates in the hypoxic tumor microenvironment and directly destroys cancer cells. Within 24 hours, bacterial counts within tumors increase approximately 3,000-fold, efficiently targeting tumor tissue.
- Immune Activation Effect: The presence of E. americana stimulates the immune system, recruiting T cells, B cells, and neutrophils to the tumor site. Pro-inflammatory cytokines (TNF-α, IFN-γ) produced by these immune cells further amplify immune responses and induce cancer cell apoptosis.
Tumor-Specific Accumulation Mechanism
E. americana demonstrates remarkable tumor specificity, accumulating in tumor tissues without colonizing normal organs. This is achieved through multiple synergistic mechanisms:
- Hypoxic Environment: Tumor tissues' characteristic hypoxia promotes anaerobic bacterial proliferation.
- Immunosuppressive Environment: Cancer cells express CD47 protein, creating local immunosuppression, allowing bacterial survival.
- Abnormal Vascular Structure: Tumor vessels are leaky, facilitating bacterial extravasation.
- Metabolic Abnormalities: Tumor-specific metabolites support selective bacterial growth.
Excellent Safety Profile
Comprehensive safety evaluations revealed that E. americana exhibits:
- Rapid blood clearance (half-life of approximately 1.2 hours, undetectable at 24 hours).
- Zero bacterial colonization in normal organs, including the liver, spleen, lung, kidney, and heart.
- Only transient mild inflammatory responses, which normalize within 72 hours.
- No chronic toxicity observed during a 60-day extended observation period.
This research establishes the proof-of-concept for a novel cancer therapy using natural bacteria. Future research will focus on expanding the application to other cancer types, optimizing administration methods, and exploring combination therapy with existing immunotherapy and chemotherapy.
This discovery highlights the untapped potential of biodiversity in developing novel medical technologies and offers new therapeutic options for patients with refractory cancers.
