CD44 expression and hyaluronic acid binding of malignant glioma cells

The mechanisms leading to rapid invasive growth of malignant gliomas are po orly understood. Expression of the hyaluronic acid (HA) receptor CD44 and a dhesion to HA are involved in invasive properties. Our previous studies hav e shown that malignant glioma cells are able to adhere to extracellular HA. Here we investigated expression of the hyaluronic acid receptor CD44 prote in in five human (T98G, A172, U87MG, 86HG39, 85HG66) and two rat (C6, 9L) g lioma cell lines. Influence of anti-CD44 antibody and hyaluronidase-preincu bation on the HA-binding was determined using HA/BSA (bovine serum albumin) -coated culture plates. While all gliomas were highly positive for CD44 wit h no differences in the number of positive staining cells, median fluoresce nce intensity decreased as follows: C6>T98G>9L>85HG66> 86HG39>A172> U87MG. Using HA/BSA coated culture plates the relative levels of specific adhesion to HA were determined as T98G>A172>9L>86HG39>U87MG>85HG66. C6 cells failed to bind HA specifically. Incubation with anti-human-CD44 MAb significantly decreased HA-adhesion of T98G, A172, 85HG66 and U87MG human glioma cells. However the binding capacity was completely blocked only in 85HG66 cells. T he three other cell lines kept a specific HA-adhesion after saturation of t he receptor. Hyaluronidase pretreatment markedly enhanced HA-adhesion of C6 and 9L rat glioma cells. These results suggest that (i) HA-adhesion of mal ignant glioma cells is mainly, but not only, mediated by CD44, (ii) express ion of CD44 does not correspond with adhesion capacity and (iii) cell-bound glycosaminoglycans may influence glioma cell adhesion to extracellular HA.