C-Met identifies a population of matrix metalloproteinase 9-producing monocytes in peritumoral stroma of hepatocellular carcinoma (TUM6P.966)

Abstract

Abstract Macrophages (Mφ) are prominent components of solid tumors and exhibit distinct phenotypes in different microenvironments. Previously, we found that tumors could alter the normal developmental process of Mφ to trigger transient activation of monocytes in the peritumoral stroma of human hepatocellular carcinoma (HCC). In the present study, we showed that a fraction of monocytes in the peritumoral stroma, but not in HCC cancer nests, expressed surface c-Met molecules. Monocytes exposed to tumors strongly expressed c-Met proteins with kinetics similar to their activation status, and significant correlations were found between c-Met levels and HLA-DR expression on tumor-infiltrating monocytes. NF-κB-mediated autocrine TNF-α stimulated the expression of c-Met on activated monocytes, and by interacting with its ligand HGF, c-Met regulated the retention, accumulation, and matrix metalloproteinase (MMP) 9-producing capacity of monocytes in the peritumoral stroma of HCC. The intensity of c-Met expression on tumor-infiltrating monocytes was associated with high mortality and reduced survival of patients with HCC. Therefore, the expression of c-Met on activated monocytes/Mφ may represent a novel mechanism by which a tumor actively and precisely regulates the distribution and functions of these cells to facilitate disease progression.