STEM-06. TISSUE FACTOR SIGNALING IN GLIOBLASTOMA TUMOR-INITIATING CELLS

Abstract Glioblastoma (GBM) is an aggressive form of brain cancer with few treatment options, characterized by over-activation of receptor tyrosine kinases (RTKs). Brain tumor-initiating cells (BTICs) is a subpopulation of cells in GBM which have the unique capacity to self-renew, facilitating recurrence. Tissue Factor (TF), normally involved in blood coagulation, is elevated in GBM and strongly correlates with more aggressive behavior. We hypothesize that TF promotes malignant behavior in glioblastoma by activating protease-activated receptor 2 (PAR2), leading to RTK stimulation and the maintenance of brain tumor-initiating cells. Therefore, our approaches are to determine: the mechanisms by which TF-PAR2 stimulates RTK signaling in GBM; the role of RTKs in mediating TF-induced BTIC maintenance in GBM, and the effect of blocking TF signaling on RTK-based therapies against GBM. Our data indicate that TF can activate multiple classes of tumor-promoting RTKs, and sustains cell proliferation through its main receptor, PAR2, even in the presence of an RTK inhibitor. We also found that TF suppression impairs the BTIC phenotype in high TF-expressing, RTK-driven GBM. This project will advance our understanding of how TF promotes malignant behavior, identify a powerful means by which cancers can resist RTK inhibitors currently in clinical use, and demonstrate the therapeutic potential of blocking TF-PAR2 signaling in cancer.