Targeting Galectin-1 in Carcinoma-Associated Fibroblasts Inhibits Oral Squamous Cell Carcinoma Metastasis by Downregulating MCP-1/CCL2 Expression

Purpose: Carcinoma-associated fibroblasts (CAFs) in tumor stroma play an important role in tumor progression and have been associated with a poor prognosis in oral squamous cell carcinoma (OSCC). However, how CAFs influence OSCC malignancy and whether normalizing CAFs inhibits cancer progression remain unclear. Experimental Design: The relationship between the expression of Galectin-1 (Gal-1) and alpha-smooth muscle actin (alpha-SMA, a CAF marker) in OSCC patient samples and primary cultured CAFs was examined by quantitative real-time PCR, Western blotting, and immunofluorescence. To examine the effect of Gal-1 on CAF activation and CAF-mediated tumor invasion and migration in vitro, Gal-1 expression was knocked down by small hairpin RNA. Finally, cancer cells and CAFs were coimplanted into SCID mice to evaluate the effect of Gal-1 on CAF-modulated tumor progression in vivo. Results: Gal-1 expression is positively associated with alpha-SMA in the stroma of OSCC specimens. Gal-1 knockdown decreases activated CAF characteristics, resulting in a decrease in alpha-SMA expression and extracellular matrix protein production. Notably, blocking Gal-1 expression significantly inhibits CAF-conditioned medium-induced tumor cell migration and invasion, possibly by reducing the production of monocyte chemotactic protein-1 (MCP-1/CCL2). MCP-1 induces the migration of OSCC cells by binding to the receptor CCR2; adding an MCP-1 antibody to CAF-conditioned medium that inhibits the interaction between MCP-1 and CCR2 abolishes migration. Finally, we found that Gal-1 knockdown in CAFs significantly reduces CAF-augmented tumor growth and metastasis in vivo. Conclusions: Our findings demonstrate that Gal-1 regulates CAF activation and indicate that targeting Gal-1 in CAFs inhibits OSCC metastasis by modulating MCP-1 expression. Clin Cancer Res; 17(6); 1306-16. (C)2011 AACR.