The 72-kd type IV
collagenase is a member of the
collagenase enzyme family that has been closely linked with the invasive phenotype of
cancer cells. Previous studies have shown that both normal cells and highly invasive
tumor cells produce the 72-kd type IV
procollagenase enzyme in a complexed form consisting of the
proenzyme and a novel
tissue inhibitor of metalloproteinases,
TIMP-2. The balance between activated
enzyme and available inhibitor is thought to be a critical determinant of the matrix proteolysis associated with a variety of
pathologic processes, including
tumor cell invasion. In the present study, we demonstrate that alteration of the
metalloproteinase-
metalloproteinase-inhibitor balance in favor of excess inhibitor blocks human
fibrosarcoma HT-1080
tumor cell invasion of a reconstituted basement membrane. The HT-1080 cell line produces both the 72-kd and the 92-kd type IV
collagenases. Alteration of the type IV
collagenase-inhibitor balance was achieved by addition of free
TIMP-2 or
antibodies to 72-kd type IV
collagenase. Native, purified
TIMP-2 was inhibitory in the range of 1-25 micrograms/mL. Addition of specific antiserum against the 72-kd type IV
collagenase, which did not cross-react with the 92-kd type IV
collagenase, inhibited HT-1080 cell invasion to the same extent. These results suggest that
metalloproteinases, in particular the 72-kd type IV
collagenase, are critical for
tumor cell invasion of the reconstituted basement membrane. Our findings demonstrate that addition of the endogenous inhibitor
TIMP-2 is able to block invasion. Thus, we recommend initiation of in vivo studies of the therapeutic potential of
TIMP-2 to block
tumor cell invasion and intravasation into the circulation.