Malignant astrocytoma cell attachment and migration to various matrix proteins is differentially sensitive to phosphoinositide 3-OH kinase inhibitors

Phosphoinositide 3-OH kinase (PI3-K) has been shown to play an important ro le in the signaling pathway necessary for cytoskeletal reorganization in no n-astrocytic cells. We investigated the role of PI3-K in U-251 MC human mal ignant astrocytoma cell adhesion and migration. Attachment of U-251MG cells to vitronectin, fibronectin, laminin, and collagen was inhibited in a conc entration-dependent manner by two specific inhibitors of PI3-K (Wortmannin and LY294002). Attachment to vitronectin, fibronectin, and laminin was more sensitive to inhibition of PI3-K (45% inhibition at 10 nM Wortmannin) than attachment to collagen (25% inhibition at 100 nM Wortmannin). Similarly, m igration toward these substrates showed differential sensitivity to inhibit ion. Attachment of the cells to these matrix proteins resulted in an increa se in PI3-K activity, as compared to that of cells in suspension, with atta chment to vitronectin resulting in the greatest increase in PI3-K activity. p125 focal adhesion kinase (p125FAK) was found to co-immunoprecipitate wit h PI3-K from the NP40-soluble cell fraction of a 1% NP40 detergent lysate o f cells in the early stages of adhesion to vitronectin and fibronectin, but not during adhesion to collagen. The expression of p125FAK protein and lev el of phosphorylation were similar on adherence to all three substrates. Th ese data indicate that the sensitivity of U-251MG cell attachment and migra tion to PI3-K inhibitors is substrate-dependent, and that complex formation of PI3-K and p125FAK correlates with this sensitivity to PI3-K inhibitors. Our data suggest a role for PI3-K and p125FAK complex formation in PI3-K a ctivation. (C) 1999 Wiley-Liss, Inc.