CD44 CHONDROITIN SULFATE PROTEOGLYCAN AND ALPHA-2-BETA-1 INTEGRIN MEDIATE HUMAN-MELANOMA CELL-MIGRATION ON TYPE-IV COLLAGEN AND INVASION OFBASEMENT-MEMBRANES/

Tumor cell invasion of basement membranes (BM) represents one of the c ritical steps in the metastatic process. Tumor cell recognition of ind ividual BM matrix components may involve individual cell adhesion rece ptors, such as integrins or cell surface proteoglycans, or may involve a coordinate action of both types of receptors. In this study, we hav e focused on the identification of a cell surface CD44/chondroitin sul fate proteoglycan (CSPG) and alpha 2 beta 1 integrin on human melanoma cells that are both directly involved in the in vitro invasion of rec onstituted BM via a type IV collagen-dependent mechanism. Interfering with cell surface expression of human melanoma CSPG with either rho-ni trophenyl-beta-D-xylopyranoside treatment or anti-CD44 monoclonal anti body (mAb) preincubation inhibits melanoma cell invasion through recon stituted BM. These treatments also strongly inhibit melanoma cell migr ation on type IV collagen, however, they are ineffective at inhibiting cell adhesion to type IV collagen. Purified melanoma cell surface CD4 4/CSPG, or purified chondroitin sulfate, bind to type IV collagen affi nity columns, consistent with a role for CD44/CSPG-type TV collagen in teractions in mediating tumor cell invasion. In contrast, melanoma cel l migration on laminin (LM) does not involve CD44/CSPG, nor does CD44/ CSPG bind to LM, suggesting that CD44/CSPG-type IV collagen interactio ns are specific in nature. Additionally, anti-alpha 2 and anti-beta 1 integrin mAbs are capable of blocking melanoma cell invasion of recons tituted BM. Both of these anti-integrin mAbs inhibit melanoma cell adh esion and migration on type TV collagen, whereas only anti-beta 1 mAb inhibits cell adhesion to LM. Collectively, these results indicate tha t melanoma cell adhesion to type IV collagen is an important considera tion in invasion of reconstituted BM in vitro, and suggest that CD44/C SPG and alpha 2 beta 1 integrin may collaborate to promote human melan oma cell adhesion, migration, and invasion in vivo.