Laminin isoforms and their integrin receptors in glioma cell migration and invasiveness: Evidence for a role of alpha5-laminin(s) and alpha3beta1 integrin.

Glioma cell infiltration of brain tissue often occurs along the basement membrane (BM) of blood vessels. In the present study we have investigated the role of laminins, major structural components of BMs and strong promoters of cell migration. Immunohistochemical studies of glioma tumor tissue demonstrated expression of alpha2-, alpha3-, alpha4- and alpha5-, but not alpha1-, laminins by the tumor vasculature.

Megakaryocytic cells synthesize and platelets secrete alpha5-laminins, and the endothelial laminin isoform laminin 10 (alpha5beta1gamma1) strongly promotes adhesion but not activation of platelets.

Following vascular injury, basement membrane (BM) components of the blood vessels are exposed to circulating cells and may contribute to hemostasis and/or thrombosis. Laminins 8 (LN-8) (alpha4beta1gamma1) and 10 (LN-10) (alpha5beta1gamma1) are major laminin isoforms of the endothelial BM, and LN-8 is also secreted by activated platelets. In the present study, we demonstrate synthesis of alpha5-laminins LN-10 and LN-11 (alpha5beta2gamma1) by megakaryocytic cells, and intracellular expression of these laminin isoforms in blood platelets.