Elevated furin expression in aggressive human head and neck tumors and tumors cell lines

Pro-protein convertases (PCs) are proteases that recognize and cleave precu rsor proteins. Furin, a well-studied PC, is ubiquitously expressed, and it has been implicated in many physiological and pathological processes. Some substrates for furin, such as membrane type 1 (MT1) matrix metalloproteinas e (MMP), an MMP that activates gelatinase, a collagen-degrading enzyme, are associated with the advanced malignant phenotype. This report examines the expression of furin in carcinoma cell lines of different invasive ability. The levels of furin mRNA and protein correlated with the aggressiveness of tumor cell lines derived from head and neck and lung cancers. Furin expres sion also was investigated in primary head and neck squamous cell carcinoma s (HNSCCs). Furin mRNA was not detected in nonmetastasizing carcinomas. In contrast, furin mRNA was expressed in metastasizing HNSCCs. Immunohistochem istry and Western blot analysis confirmed these results at the protein leve l. Furin activity was investigated indirectly by evaluating the expression of the pro-form and the processed form of MT1-MMP. Metastasizing HNSCCs sho wed increased expression of MT1-MMP. Furthermore, pro-MT1-MMP expression wa s noted in most of the nonmetastasizing HNSCCs analyzed by Western blot, an d it was absent in the metastasizing HNSCCs, This finding suggests a lower level of furin-mediated MT1-MMP activation in the less aggressive cancers. These observations indicate that furin plays a role in tumor progression. I ts overexpression in more aggressive or metastasizing cancers resulted in i ncreased MMP processing. (C) 2001 Wiley-Liss, Inc.