ECM Dependent and Integrin Mediated Tumor Cell Migration of Human Glioma and Melanoma Cell Lines Under Serum-free Conditions

Collagen IV, laminin and fibronectin are constituents of the cerebral extracellular matrix (ECM), which is critical in glioma cell invasion. The aim of the present study was to evaluate the integrin dependent cell-matrix interactions of two tumors with different invasive properties under matrixfree conditions. Two human glioma (GaMG, U373) and melanoma (MV3, BLM) cell lines were grown in serum free medium. Immunofluorescence microscopy of collagen IV, laminin, and fibronectin was performed. The adhesion of monolayer cells and their migration out of multicellular spheroids was quantified for these ECM components. Integrin chains known to act as laminin receptors were blocked by specific antibodies in additional migration assays. All cell lines expressed all the ECM components under serum free conditions. Tumor cell adhesion and migration in both glioma and melanoma cell lines was increased by all the ECM components, laminin being the strongest promotor of migration. However, migration was dose dependent in gliomas, whereas melanomas revealed a dose optimum of 10 micrograms/ml laminin. Antibodies against alpha 3 integrins significantly reduced migration on laminin in all cell lines, anti-beta 1 in all cell lines except U373. Anti-alpha 2 in BLM showed a strong effect, anti-alpha 6 was a stronger inhibitor in glioma than in melanoma cells. Integrins are functionally involved in tumor cell locomotion on laminin. The blocking of laminin related integrin chains markedly reduces cell motility in a varying manner between the cell lines. Moreover, different cell lines utilize different integrins as the laminin receptor.