Influence of ganglioside GM3 and high density lipoprotein on the cohesion of mouse brain tumor cells.

Previous findings with various murine tumor cell lines suggest an association between ganglioside GM3 and cell cohesive properties. The influence of GM3 on cohesion was studied in two mouse brain tumor cell lines: ependymoblastoma (EPEN) and CT-2A. In culture, the EPEN cells grow as islands and contain GM3 as the only ganglioside, whereas the CT-2A cells grow as a fusiform cell monolayer and contain GM2, GM1, and GD1a as major gangliosides and low amounts of GM3. To examine the role of GM3 in cohesion, both cell lines were treated with 1) C. perfringens neuraminidase, 2) anti-GM3 monoclonal antibody (mAb DH2), or 3) were grown in serum-free medium. All three treatments caused a significant increase in the number of non-cohesive and protoplasmic process-bearing cells for the EPEN, but had no effect on the morphology of the CT-2A cells. The neuraminidase treatment removed GM3 from both cell lines and caused a significant accumulation of GM1 in the CT-2A cells. EPEN cell cohesion and GM3 content returned to control levels after removal of neuraminidase. EPEN cell cohesion was restored in serum-free medium with added high density lipoprotein (HDL). The HDL effect on the EPEN cell cohesion was dose-dependent and was not seen with other lipoproteins. We suggest that EPEN cell cohesion could involve an interaction between extracellular HDL, acting as a bridge, and GM3 molecules on opposing cell surfaces.