Human
tissue factor pathway inhibitor-2 (TFPI-2) is a Kunitz-type
serine protease inhibitor that inhibits
plasmin,
trypsin,
chymotrypsin,
cathepsin G, and
plasma kallikrein but not
urokinase-type plasminogen activator,
tissue plasminogen activator, or
thrombin. Preliminary findings in our laboratory suggested that the expression of
TFPI-2 is downregulated or lost during
tumor progression in human
gliomas. To investigate the role of
TFPI-2 in the invasiveness of
brain tumors, we stably transfected the human high-grade
glioma cell line SNB19 and the human low-grade
glioma cell line Hs683 with a vector capable of expressing a transcript complementary to the full-length
TFPI-2 mRNA in either sense (0.7 kb) or antisense (1 kb) orientations. Parental cells and stably transfected cell lines were analysed for
TFPI-2 protein by Western blotting and for
TFPI-2 mRNA by Northern blotting. The levels of
TFPI-2 protein and
mRNA were higher in the sense clones (SNB19) and decreased in the antisense (Hs683) clones than in the corresponding parental and vector controls. In spheroid and
matrigel invasion assays, the SNB19 parental cells were highly invasive, but the sense-transfected SNB-19 clones were much less invasive; the antisense-transfected Hs683 clones were more invasive than their parental and vector controls. After intracerebral injection in mice, the sense-transfected SNB19 clones were less able to form
tumors than were their parental and vector controls, and the antisense-Hs683 clones but not the parental or vector controls formed small
tumors. This is the first study to demonstrate that down- or upregulation of
TFPI-2 plays a significant role in the invasive behavior of human
gliomas.