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


OBJECTIVE
We hypothesized that blocking of TF activity with the tick anticoagulant Ixolaris might interfere with glioblastoma progression.


RESULTS
TF was identified in U87-MG cells by flow-cytometric and functional assays (extrinsic tenase). In addition, flow-cytometric 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.


CONCLUSIONS
Our results suggest that Ixolaris might be a promising agent for anti-tumor therapy in humans.
Carneiro-Lobo
T C
TC
Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Konig
S
S
Machado
D E
DE
Nasciutti
L E
LE
Forni
M F
MF
Francischetti
I M B
IM
Sogayar
M C
MC
Monteiro
R Q
RQ
D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D018450:Disease Progression; D015536:Down-Regulation / Q000187:drug effects; D005909:Glioblastoma / Q000188:drug therapy* / Q000473:pathology; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009389:Neovascularization, Pathologic / Q000188:drug therapy*; D012471:Salivary Proteins and Peptides / Q000494:pharmacology* / Q000627:therapeutic use; D013925:Thromboplastin / Q000037:antagonists & inhibitors*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics
C455900:Ixolaris protein, Ixodes scapularis; D012471:Salivary Proteins and Peptides; D042461:Vascular Endothelial Growth Factor A; D013925:Thromboplastin