ATPS-58: COMBINATION TYROSINE KINASE INHIBITORS EFFECTIVELY OVERCOME THE APOPTOSIS RESISTANCE, INVASIVE POTENTIAL AND ANGIOGENIC CAPACITY OF GLIOBLASTOMA MULTIFORME CELLS

Despite the aggressive treatment of glioblastoma multiforme (GBM) patients have a poor survival of 14 months from diagnosis. Several factors contribute to the limited efficacy of current treatments including invasiveness, resistance to apoptosis and large inter- and intra-patient cellular heterogeneity. Tyrosine kinases are known to contribute to these parameters and are commonly mutated or overexpressed in GBM. Recent work has focused on tyrosine kinase inhibitors (TKIs) as promising treatment strategy. The cytotoxicity of 13 TKIs was evaluated against four human GBM cell lines (U87, LN-18, U373 and A172) and established crizotinib, a Met inhibitor, and dasatinib, a SRC inhibitor to be the most efficacious combination. While dasatinib treatment was cytostatic, crizotinib treatment induced apoptosis in all cell lines (from 24.3 to 47.8%). The combination synergistically increased apoptosis in the four cell lines (57.7 to 64.4%) and maintained apoptosis 72 hours following drug withdrawal (9.1-50.4%). In addition, crizotinib treatment induced polyploidy in all cell lines, 11.1 to 39.3% of cells had 4-fold the normal DNA content, the co-treatment with dasatinib attenuated polyploidy by 2 to 4-fold. The expression of proteins involved in cell survival, invasion and proliferation, such as Met, Src and AKT, were reduced by single treatments and effectively abolished by the combination treatment. Furthermore, using LN-18 cells, we showed that combination treatment abolished migration and reduced invasion by 80%. In vitro models of angiogenesis and vascular mimicry were also evaluated and showed that the combination was sufficient to abolish endothelial-tube formation as well as the vascular mimicry of GBM cells. The combination of crizotinib and dasatinib effectively overcomes several resistance factors known to hinder effective management of GBM and warrants further validation in animal models.