CORRELATION OF EXPRESSION OF NCAM AND GD3 GANGLIOSIDE TO MOTILE BEHAVIOR IN NEOPLASTIC GLIA

Studies of developing mammalian tissues have established that certain neural cell adhesion molecules (NCAMs) may be down-regulated during th e migratory phase concurrent with an increase in levels of matrix meta lloproteinases. In addition, there is evidence that simple ganglioside s such as GD3 are transiently present on the surface of such migratory cells. Since migration, or motility, is a prerequisite for diffuse lo cal invasion of brain by neoplastic cells, the expression of NCAM and GD3 on brain tumour cells was studied in order to establish their poss ible role in the invasive process. An astrocytoma parent cell line (IP SB-18) and two morphologically distinct, cloned cell lines (clone I an d 12) derived from it, were used in in vitro motility assays using 8 m u m porosity polycarbonate filters in ''Transwell'' modified Boyden ch ambers. Immunocytochemical staining with anti-NCAM monoclonal antibodi es (UJ13A and ERIC-I) and with the antiganglioside monoclonal antibodi es LB1 (which recognises GD3) and A2B5 (which recognises a range of si mple gangliosides) showed that some cells in culture from the parent l ine were positive for either NCAM or GD3; clone 1 was NCAM positive bu t GD3 negative while clone 12 was NCAM negative but ganglioside positi ve. Motility assays showed that although clone 12 migrated more effici ently than either clone I ol the parent line, this was not statistical ly significant. Moreover; similar assays were conducted on two further sub populations of cells which were evolved from the immunomagnetic s eparation of the parent cell line, IPSB-18 according to NCAM expressio n (i.e. NCAM positive and NCAM negative). The results indicated that t he NCAM negative cells migrated more efficiently than the NCAM positiv e cells, in a time-dependent manner; when incubated for 4, 12 and 18 h ours in Boyden chambers. These findings suggest that during the migrat ory phase of brain tumour invasion, NCAM expression is down-regulated whereas ganglioside expression is up-regulated.