C-Reactive Protein Facilitates Premetastatic Niche Formation in the Lungs.

C-reactive protein (CRP) has long been recognized as a marker of inflammation, but its evolving role in immunomodulation and cancer has increasingly been recognized. In recent years, multiple studies have explored CRP as a biomarker for prognosis and therapy response, particularly in the context of cancer immunotherapy. In this issue of Cancer Research, Feng and colleagues investigate the role of CRP in the development of lung metastasis. They provide evidence for a direct role of CRP acting together with commensal bacteria to instruct an immune-tolerant state of pulmonary macrophages through Fc gamma receptor IIb signaling. By suppressing immune surveillance in the lungs, CRP facilitates the formation of a premetastatic niche, allowing circulating tumor cells to establish metastases. See related article by Feng et al., p. 4184.