Matrix metalloproteinase (MMP) inhibition selectively decreases type II MMP activity in a murine model of pancreatic cancer.

Basement membrane degradation is a critical component of tumor invasion and metastasis that is facilitated by the family of enzymes known as matrix metalloproteinases (MMPs). MMP-2 and MMP-9 are two subtypes that have specifically been identified in tumors of gastrointestinal origin. We have previously shown that broad inhibition of these enzymes with the MMP inhibitor BB-94 improves survival in a murine model of pancreatic cancer. The purpose of this study was to determine MMP-2 and MMP-9 activity in orthotopic tumors from mice treated with and without BB-94. Ten million cells of a moderately differentiated pancreatic cancer cell line (HPAC) were implanted orthotopically into Balb/c nu/nu mice. The mice were treated with BB-94 or vehicle control for 70 days or until death. At necropsy, tumors were harvested, total protein was extracted, and MMPs were purified from 400 microgram of crude protein extract by gelatin-Sepharose affinity chromatography. Relative enzyme levels and activity of MMP-2 and MMP-9 were determined by Western blot and gelatin zymography. Tumors from treated animals were significantly smaller than those from nontreated animals. MMP-2 was present in greater amounts in both treated and nontreated animals than MMP-9. Active MMP-2 was present in both groups but significantly decreased in animals treated with BB-94. Active MMP-9 was absent in both groups, whereas levels of latent MMP-9 appeared lower than those of MMP-2 in all samples. Activated MMP-2 and not MMP-9 in HPAC cells grown in nude mice suggests that this MMP subtype is more critical in the phenotypic behavior of such tumors. Furthermore, attenuated levels of active MMP-2 in animals treated with the enzyme inhibitor BB-94 suggest that previously observed improvements in survival correlate with the level of MMP-2 activity.