Our findings suggest that MT-MMP is indeed the tumor-specific activator of pro-gelatinase A in lung carcinomas and is important to initiate invasion of basement membranes.
Increased levels of pro-enzyme and active enzyme forms of gelatinase A (MMP-2) and increased cathepsin B activity were localized in regions of tumor invasion as compared with a matched number of normal epithelial cells from the same patient.
Gelatinase A (type-IV collagenase; M(r) 72,000) is produced by tumour stroma cells and is believed to be crucial for their invasion and metastasis, acting by degrading extracellular matrix macro-molecules such as type IV collagen.
Maximal expression of gelatinase A and TIMP-2 mRNAs occurs in malignant neoplasms as part of the host response to the presence of established neoplastic cells rather than as an initial response to invasion.
Matrix metalloproteinases (MMP), such as 72 kDa type IV collagenase (MMP-2) and 92 kDa type IV collagenase (MMP-9), play an important role in tumor invasion and metastasis.
Three types of membrane type-matrix metalloproteinases (MT-MMPs) have been identified as activators of pro-MMP2 (gelatinase A/72-kilodalton Type IV collagenase), which is believed to be crucial for tumor invasion and metastasis.
In the liver tissues, enhanced secretion of active forms of gelatinase A and matrilysin was associated with portal venous invasion (P < 0.05, respectively), intrahepatic metastasis (P < 0.05, respectively), and recurrence within the first postoperative year (P < 0.01 and P < 0.05, respectively).
One member of the matrixin family, gelatinase A, is regulated differently from other MMPs, suggesting that it may play a unique role in cell-matrix interactions, including cell invasion.
Ovcar-3 cell attachment, migration and in vitro invasion were significantly decreased after paclitaxel treatment (P = 0.02, P < 0.01 and P = 0.001, respectively) whereas no alteration in the secretion of latent MMP-2 was noted.
Expression of matrix metalloproteinase-2 (MMP-2), an enzyme involved in tumor-cell invasion, in SNB19 cells expressing p16 was significantly reduced compared to that of parental SNB19 and vector-infected cells.
MT1-MMP (membrane type 1-matrix metalloproteinase) is implicated in tumor-epithelial cell surface activation of latent pro-MMP-2, indicating a mechanism for tumor-stromal interaction in invasion.
We conclude that SPARC, and specifically its NH2-terminal domain, regulates the activation of MMP-2 at the cell surface and is therefore likely to contribute to the proteolytic pathways associated with tumor invasion.
These results suggest that both MT1-MMP and MT2-MMP play a key role in the activation of pro-MMP-2 in the human malignant astrocytic tumors and that the gelatinolytic activity is involved in the astrocytic tumor invasion.
Enhanced mRNA expression of gelatinase A or gelatinase B and of matrilysin showed trends toward presence of capsular invasion (P = 0.078) and intrahepatic metastasis (P = 0.064), respectively.