Restoration of tissue factor pathway inhibitor inhibits invasion and tumor growth in vitro and in vivo in a malignant meningioma cell line.

Tissue factor pathway inhibitor 2 (TFPI-2) is a 32-kDa extracellular matrix-associated kunitz-type serine proteinase inhibitor. It is secreted by all vascular cells and plays a role in tumor invasion and metastasis, presumably by plasmin-mediated matrix remodeling. Previous studies have shown high expression of TFPI-2 by benign tumors and low or absent expression in highly malignant tumors. Malignant meningiomas constitute 10-15% of all meningiomas and our previous studies revealed loss of expression of TFPI-2 in malignant gliomas. To investigate the role of TFPI-2 in the invasiveness of malignant meningiomas, we stably transfected the human meningioma cell line, IOMM-Lee, with a vector capable of expressing a transcript complementary to the full length of TFPI-2 mRNA in a sense orientation. Restoration of TFPI-2 led to decreased invasiveness of transfected cells compared to parental and vector controls in Matrigel and spheroid assays and inhibition of angiogenesis in in vitro co-cultures with human umbilical vein endothelial cells (HUVEC) and in vivo dorsal skin assay studies. As assessed by Western blotting, we also observed increased expression of BAX, cytochrome c and caspase 3 as well as decreased expression of XIAP (X-linked inhibitor of apoptosis). Finally, TFPI-2 overexpression inhibited intracranial tumor formation in nude mice. Our data substantiate our previous observation that TFPI-2 plays an important role in tumor progression and has potential in anti-cancer therapy.