Colorectal cancer remains one of humanity's most formidable health adversaries, claiming approximately 900,000 lives globally each year out of nearly 1.9 million new cases. In the United States alone, over 150,000 individuals were diagnosed in 2024. The burden is rising sharply in low and middle-income nations, driven by ageing populations and limited access to screening programmes. Symptoms like bloody stool, unexplained weight loss, and persistent changes in bowel habits often appear late, underscoring the critical need for colonoscopic screening. While the overall survival rate is around 65%, it soars to 90% when the disease is caught early, highlighting the urgent demand for better detection and treatment options.
A Revolutionary Discovery from the Deep
In a breakthrough that could reshape cancer therapy, researchers from the Japan Advanced Institute of Science and Technology (JAIST) have turned to the ocean for answers. Led by Professor Eijiro Miyako, the team has identified a naturally occurring marine bacterium, Photobacterium angustum, as a potent and precise weapon against colorectal cancer cells. This discovery ignites new hope for a disease where conventional treatments like chemotherapy and surgery often fail, particularly in advanced stages.
The research journey involved testing various marine bacterial strains, including P. phosphoreum and A. logei, on mouse models. However, Photobacterium angustum stood out dramatically. It demonstrated a remarkable ability to shrink tumours significantly, improve survival rates, and cause minimal side effects, outperforming all other candidates.
How the Marine Bacterium Fights Cancer
The mechanism of action is what makes this discovery particularly exciting. Photobacterium angustum naturally seeks out and thrives in the low-oxygen environments characteristic of solid tumours. Once it accumulates in the colon cancer site, it directly bursts the cancer cells. Furthermore, it orchestrates a powerful immune response, rallying the body's own defences by increasing the production of protective T-cells. This dual attack not only tackles the existing tumour but also provides long-term protection against relapse. In studies, cured mice even rejected subsequent attempts to induce tumours weeks later.
Critically, this approach requires no genetic modification. When injected systemically, the bacterium selectively gathered in colon cancer tumours, sparing healthy organs like the liver and lungs. This targeted action is a major advantage over traditional chemotherapy, which often causes severe side effects by damaging healthy tissue. The pioneering study, published in the Journal for ImmunoTherapy of Cancer, provides the first evidence of this bacterium's efficacy against colon cancer.
Broad Potential and the Path Ahead
The promise of Photobacterium angustum extends beyond standard colon cancer. Further analysis showed it was effective in models of inflammation-driven colorectal cancer and even in drug-resistant cases like triple-negative breast cancer. Survival rates increased substantially compared to control groups, with some instances showing tumour regression exceeding 80%. Notably, while other tested bacteria caused immediate toxicity, P. angustum proved to be gentle and harmless to non-cancerous cells.
This marine-inspired therapy could offer a lifeline for patients weakened by aggressive treatments. Its two-pronged strategy—direct tumour killing and immune system activation—could overcome limitations of current immunotherapies, which don't work for all patients and can lead to drug resistance. The discovery continues a promising trend of marine-derived medicines, following compounds from sea sponges used in leukemia treatment.
While the preclinical success sets the stage for imminent human trials, challenges remain. Scientists must now tackle large-scale production, determine safe and effective human dosages, and prove its safety in larger, diverse populations. This innovation powerfully underscores the vast, untapped potential of nature's toolkit, especially the largely unexplored world of marine microbes. As patients and doctors watch closely, a new and formidable enemy for colorectal cancer may soon emerge from the depths of the ocean.
