Correlation of expression of NCAM and GD3 ganglioside to motile behaviour in neoplastic glia

Studies of developing mammalian tissues have established that certain neural cell adhesion molecules (NCAMs) may be down-regulated during the migratory phase concurrent with an increase in levels of matrix metalloproteinases. In addition, there is evidence that simple gangliosides such as GD3 are transiently present on the surface of such migratory cells. Since migration, or motility, is a prerequisite for diffuse local invasion of brain by neoplastic cells, the expression of NCAM and GD3 on brain tumour cells was studied in order to establish their possible role in the invasive process. An astrocytoma parent cell line (IPSB-18) and two morphologically distinct, cloned cell lines (clone 1 and 12) derived from it, were used in in vitro motility assays using 8 microns porosity polycarbonate filters in "Transwell" modified Boyden chambers. Immunocytochemical staining with anti-NCAM monoclonal antibodies (UJ13A and ERIC-1) and with the anti-ganglioside monoclonal antibodies LB1 (which recognises GD3) and A2B5 (which recognises a range of simple gangliosides) showed that some cells in culture from the parent line were positive for either NCAM or GD3; clone 1 was NCAM positive but GD3 negative, while clone 12 was NCAM negative but ganglioside positive. Motility assays showed that although clone 12 migrated more efficiently than either clone 1 or the parent line, this was not statistically significant. Moreover, similar assays were conducted on two further sub populations of cells which were evolved from the immunomagnetic separation of the parent cell line, IPSB-18, according to NCAM expression (i.e. NCAM positive and NCAM negative). The results indicated that the NCAM negative cells migrated more efficiently than the NCAM positive cells, in a time-dependent manner, when incubated for 4, 12 and 18 hours in Boyden chambers. These findings suggest that during the migratory phase of brain tumour invasion, NCAM expression is down-regulated whereas ganglioside expression is up-regulated.