A Specific Gut Microbe Enhances Effectiveness of Cancer Immunotherapy

Recent research from the National Cancer Center Research Institute in Tokyo has identified a newly isolated gut bacterium, named Hominenteromicrobium strain YB328, that can significantly boost the body's response to cancer treatments like PD-1 blockade immunotherapy. This groundbreaking study demonstrates that individuals carrying this particular microbe show increased infiltration of activated T cells into tumors, correlating with longer progression-free survival across various cancer types.

The study involved analyzing fecal samples from 50 Japanese patients with cancers such as non-small cell lung cancer and gastric cancer, all undergoing PD-1-targeting therapies. Using advanced genetic sequencing, researchers identified that patients with higher levels of YB328 in their guts had better clinical outcomes and immune responses.

In laboratory experiments, mice colonized with YB328 exhibited enhanced tumor suppression and greater activity of tumor-fighting immune cells. In vitro tests showed that dendritic cells treated with YB328 displayed elevated levels of co-stimulatory molecules and increased ability to activate CD8+ T cells, which are crucial in attacking tumor cells.

Contrastingly, another microbe, P. vulgatus, was associated with poorer patient outcomes and reduced immune cell activity, suggesting that not all gut microbes have beneficial effects on immunotherapy. Interestingly, bacteria such as Faecalibacterium and Bifidobacterium, previously linked to positive outcomes, did not show significant differences in this context.

The findings suggest that colonization with YB328 promotes the migration and activation of dendritic cells, which in turn stimulate cytotoxic T cells within tumors, thereby amplifying the effects of PD-1 inhibitors. This discovery opens new avenues for enhancing cancer immunotherapy by manipulating the gut microbiome, making it a promising target for future treatments.

Published in Nature under the title "Microbiota-driven antitumour immunity mediated by dendritic cell migration," this research underscores the potential of targeting specific gut microbes to improve treatment responses in diverse cancer patients.