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 (uPA) or
tissue-type plasminogen activator and
thrombin. Earlier studies from our and other laboratories have shown that the production of
TFPI-2 is downregulated during the progression of various
cancers. To investigate the role of
TFPI-2 in the invasion and
metastasis of lung
tumors, the human
lung cancer cell line A549, which produces high levels of
TFPI-2, was stably transfected with a vector capable of expressing an antisense transcript complementary to the full-length
TFPI-2 mRNA. Northern blot analysis was used to quantify the
TFPI-2 mRNA transcript, and western blot analysis was used to measure
TFPI-2 protein levels in parental cells and stably transfected (vector and antisense) clones. The levels of
TFPI-2 mRNA and
protein were significantly less in antisense clones than in the parental and vector controls. The invasive potential of the parental cells and stably transfected vector clones in vitro, as measured by the
Matrigel invasion assay, was also markedly less than that of antisense clones. Further characterization of these clones showed that more cells migrated from antisense clones than from parental and vector clones. These data suggest that
TFPI-2 is critical for the invasion and
metastasis of
lung cancer and that the downregulation of
TFPI-2 production may be a feasible approach to increase invasiveness and
metastasis.