Ancient Immune Protein Could Hold the Key to Better Cancer Immunotherapy

Nagoya University researchers reported in Nature Communications that complement C3 made inside tumors can boost anti-PD-1 immunotherapy.

This locally produced C3 helps by blocking immunosuppressive myeloid cells, while liver-derived C3 circulating in blood does not improve response.

In mice, reducing fibroblast-derived C3 weakened treatment, and a drug that mimicked C3’s local effect restored sensitivity in resistant tumors.

The study identifies a new tumor-level immune regulator that could help predict responders and improve cancer immunotherapy.