CCL2 promotes integrin-mediated adhesion of prostate cancer cells in vitro

Chemokines undergo alterations during neoplasia. However, knowledge about their functional significance in prostate cancer (PCa) progression is still sparse. Since chemokine (C-C motif) ligand 2 (CCL2) is significantly up-regulated in patients with PCa, aim of the current study was to assess whether CCL2 contributes to invasive behavior of prostate cancer cells in vitro. The human PCa cell line PC3 was stimulated with CCL2. Cell growth was investigated by MTT dye reduction assay. Cell adhesion was analyzed by measuring attachment to a human endothelial cell (HUVEC) monolayer and immobilized collagen. Cell migration was assessed by a chemotactic assay. Integrin expression on the cell surface was evaluated by Western blot. Blocking studies were performed with anti-integrin alpha 3, anti-integrin alpha 6 and anti-integrin beta 4 monoclonal antibodies. PC3 cell growth 72 h after CCL2 exposure was significantly increased, compared to controls. Activation of tumor cells by CCL2 significantly enhanced tumor cell adhesion to HUVEC and immobilized collagen. CCL2, added for 4 or 24 h, elevated alpha 6 and beta 4 (4 > 24 h) integrin expression. alpha 3 was enhanced after 4 h, but reduced after 24 h. Blocking either alpha 3, alpha 6 or beta 4 led to significant suppression of tumor cell binding to immobilized collagen. CCL2 stimulates PCa cell adhesion and induces alterations in alpha 3-, alpha 6- and beta 4-integrin expression on the cell surface. Blocking these integrins leads to a significant reduction in cell adhesion.