Hyaluronate receptors mediating glioma cell migration and proliferation

The extracellular matrix (ECM) of the central nervous system (CNS) is enric hed in hyaluronate (HA). Ubiquitous receptors for HA are CD44 and the Recep tor for HA-Mediated Motility known as RHAMM. In the present study, we have investigated the potential role of CD44 and RHAMM in the migration and prol iferation of human astrocytoma cells. HA-receptor expression in brain tumor cell lines and surgical specimens was determined by immunocytochemistry an d western blot analyses. The ability of RHAMM to bind ligand was determined through cetylpyridinium chloride (CPC) precipitations of brain tumor lysat es in HA-binding assays. The effects of HA, CD44 blocking antibodies, and R HAMM soluble peptide on astrocytoma cell growth and migration was determine d using MTT and migration assays. Our results show that the expression of t he HA-receptors, CD44, and RHAMM, is virtually ubiquitous amongst glioma ce ll lines, and glioma tumor specimens. There was a gradient of expression am ongst gliomas with high grade gliomas expressing more RHAMM and CD44 than d id lower grade lesions or did normal human astrocytes or non-neoplastic spe cimens of human brain. Specific RHAMM variants of 85- and 58-kDa size were shown to bind avidly to HA following CPC precipitations. RHAMM soluble pept ide inhibited glioma cell line proliferation in a dose-dependent fashion. F inally, while anti-CD44 antibodies did not inhibit the migration of human g lioma cells, soluble peptides directed at the HA-binding domain of RHAMM in hibited glioma migration both on and off an HA-based ECM. These data suppor t the notion that HA-receptors contribute to brain tumor adhesion, prolifer ation, and migration, biological features which must be better understood b efore more effective treatment strategies for these tumors can be found.