Ixolaris, a tissue factor inhibitor, blocks primary tumor growth and angiogenesis in a glioblastoma model

Abstract

Summary. Background: The expression levels of the clotting initiator protein Tissue Factor (TF) correlate with vessel density and the histological malignancy grade of glioma patients. Increased procoagulant tonus in high grade tumors (glioblastomas) also indicates a potential role for TF in progression of this disease, and suggests that anticoagulants could be used as adjuvants for its treatment. Objectives: We hypothesized that blocking of TF activity with the tick anticoagulant Ixolaris might interfere with glioblastoma progression. Methods and results: TF was identified in U87-MG cells by flow-cytometric and functional assays (extrinsic tenase). In addition, flowcytometric analysis demonstrated the exposure of phosphatidylserine in the surface of U87-MG cells, which supported the assembly of intrinsic tenase (FIXa/FVIIIa/FX) and prothrombinase (FVa/FXa/prothrombin) complexes, accounting for the production of FXa and thrombin, respectively. Ixolaris effectively blocked the in vitro TF-dependent procoagulant activity of the U87-MG human glioblastoma cell line and attenuated multimolecular coagulation complexes assembly. Notably, Ixolaris inhibited the in vivo tumorigenic potential of U87-MG cells in nude mice, without observable bleeding. This inhibitory effect of Ixolaris on tumor growth was associated with downregulation of VEGF and reduced tumor vascularization. Conclusion: Our results suggest that Ixolaris might be a promising agent for anti-tumor therapy in humans.

Hypoxia regulates the expression of tissue factor pathway signaling elements in a rat glioma model

“…In vitro assays demonstrate that PAR2 activation mediates several pro-tumoral responses in GBM cell lines (20)(21)(22)(23)(24). Therefore, blocking the TF/PAR2 signaling axis has been identified as a feasible target for the treatment of GBM (45,47,48). As observed with PAR1, the P7 cell line expressed higher levels of PAR2 than ST1 under normoxia in the present study.…”

EGFP–EGF1-conjugated nanoparticles for targeting both neovascular and glioma cells in therapy of brain glioma

“…In addition, normal brain neuroglial cells are protected from the nanoparticles by functional BBB but glioma regions are characterized by impaired BBB, making TF highly expressed on glioma cells and neovascular cells a favorable dual-therapeutic target for glioma therapy [43,44] and accordingly reducing adverse effects to normal brain tissues. To the best of our knowledge, almost all the related study concentrated on inhibiting function of TF by applying TF inhibitor [45] or interfering with the signal transduction pathway TF involved [46] to suppress glioma growth. Here we present a strategy independently of TF's role on glioma progression and the therapeutic benefit would rely on TF's localization within the glioma region including glioma cells and neovascular cells rather than on inhibition of its function strictly.…”

99mTc-ixolaris targets glioblastoma-associated tissue factor: In vitro and pre-clinical applications

“…Ixolaris is a potent anticoagulant and antithrombotic molecule and displays a long half-life when administered to rodents [25]. It has been demonstrated that ixolaris blocks the primary in vivo growth of human GBM cells (U87-MG) and murine melanoma (B16F10) cells; this effect is accompanied by a significant decrease in VEGF expression and diminished tumor angiogenesis [26,27]. The antitumor activity of ixolaris is believed to derive from its ability to interact with tumorexpressed TF and the subsequent inhibition of PAR2 signaling [28].…”