A research team led by Professor Eijiro Miyako at the Japan Advanced Institute of Science and Technology (JAIST) has identified Photobacterium angustum, a naturally occurring marine bacterium, as a powerful candidate for colorectal cancer therapy. The study, published in the Journal for ImmunoTherapy of Cancer, reveals that this non-engineered microbe offers high tumor specificity, strong antitumor activity, and an excellent safety profile.
Screening and Discovery
As reported by medicalxpress, the team screened several marine bacterium strains—including P. phosphoreum, P. aquimaris, A. logei, and P. indicum—in colorectal cancer mouse models. Among these, only P. angustum demonstrated marked antitumor efficacy and significantly extended survival. In contrast, the other strains caused rapid toxicity and death.
Exceptional Safety and Tumor Selectivity
Importantly, P. angustum showed minimal toxicity. Mice maintained stable body weight, while blood tests and organ histology revealed no abnormalities. Moreover, the bacterium rapidly cleared from vital organs, except for temporary retention in the liver. At the same time, intravenous administration resulted in strong tumor tropism, with abundant bacterial colonies forming only within tumor tissues.
Dual Antitumor Mechanisms
The therapeutic effect of P. angustum operates through two synergistic mechanisms. First, natural exotoxins, including hemolysins, directly lyse cancer cells. Second, the bacterium triggers robust immune activation, driving infiltration of T cells, B cells, and neutrophils, and elevating cytokines such as TNF-α and IFN-γ. Consequently, treated mice showed significantly prolonged survival, and some achieved complete remission.
Durable Immune Memory and Broader Applications
Strikingly, cancer-free mice completely rejected tumor rechallenge 120 days later, demonstrating long-lasting immune memory. Additionally, P. angustum exhibited strong effects in triple-negative breast cancer models, suggesting broad therapeutic potential.
Future Directions
Going forward, researchers aim to validate these findings across more cancer types, explore combinations with checkpoint inhibitors, and dissect the molecular basis of tumor colonization. This work highlights a promising new direction for safe, biocompatible, non-GMO cancer immunotherapy.