Differential Effects of FAK and FGFR Inhibitors on Motility and Proliferation of L1‐Positive versus L1‐Negative Glioblastoma Cells

Abstract

Glioblastoma multiforme (GBM), a highly invasive astrocytoma, is the deadliest form of brain cancer. Glioblastoma cells express the L1CAM cell adhesion protein (L1), which is cleaved at the cell surface and binds to both integrins and fibroblast growth factor receptors (FGFRs) in an autocrine/paracrine manner. Focal adhesion kinase (FAK), which is activated by L1‐integrin interactions, and FGFR are tyrosine kinases that initiate signaling cascades stimulating GBM motility and proliferation. We hypothesized that inhibitors of FGFR and FAK would have differential effects on the motility and proliferation of T98G glioblastoma cells expressing L1 compared to those with attenuated L1 expression. Short hairpin RNA delivered by a lentiviral vector was used to block L1 expression. Cell motility was measured through quantitative time‐lapse microscopy, and proliferation was measured by cell cycle analysis and quantified as the population of cells in S phase. FAK inhibitor Y15 had a greater effect in L1‐positive versus L1‐negative cells on motility (‐45.3% vs. ‐5.6%) and S phase population (‐6.5% vs. ‐3.5%). FAK inhibitor PF431396 also produced a greater reduction in motility (‐57.2% vs. ‐15.4%) and S phase population (‐11.7% vs. ‐6.2%) in L1‐positive versus L1‐negative cells. An inhibitor of FGFR, PD173074, reduced motility (‐37.8% vs. +2.3%) and S phase population (‐8.6% vs. ‐0.4%) in L1‐positive cells only. We conclude that inhibitors of FAK and FGFR drastically decrease L1‐stimulated motility and proliferation in glioblastoma cells, indicating that they have chemotherapeutic potential for GBM tumors expressing L1. Research support was provided by the Delaware Governor's Bioscience Fellowship and the Center for Advanced Technology.