BACKGROUND Expression and enzymatic activity of gelatinases were examined in biopsy specimens from patients with colon and rectal neoplasms. The objective of this study was to determine whether the activity of these enzymes is altered between tumor areas compared with areas of noninvolved, normal mucosa and between colon and rectal carcinoma. METHODS Matrix metalloproteinase (MMP) production was analyzed by Western immunoblot analysis and gelatin zymography. mRNA was determined by quantitative, real‐time polymerase chain reaction analysis. RESULTS Patients with colon carcinoma (n = 20 patients) showed a significant increase in levels of MMP‐9 (92 kDa and 88 kDa) and MMP‐2 (72 kDa and 62 kDa) in tumor areas compared with noninvolved regions. In contrast, patients with rectal carcinoma (n = 10 patients) had revealed the same high activity of MMP‐9 in tumor regions and corresponding healthy tissue. Confirming activity measurements, in colon tumors, but not in rectal tumors, there was significant up‐regulation of MMP‐9 transcription compared with healthy tissue in the same patients. There were no significant changes in the tissue inhibitor of metalloproteinase‐1 protein when colon and rectal tumor tissues were compared with the corresponding noninvolved regions. Cell culture experiments revealed fibroblasts as the cellular origin of MMPs. The findings showed that the secretion and activation of gelatinases depend on soluble factors secreted by tumor cells and are influenced by extracellular matrix components. CONCLUSIONS This is the first report showing differences in MMP‐9 activity between rectal carcinoma and colon carcinoma. Previous results indicating an active involvement of stromal cells in the generation of MMPs during tumor invasion are extended. Because the abundance of gelatinases increases in colorectal carcinoma, inhibitors of these proteases may be of therapeutic value. Cancer 2001;92:2680–91. © 2001 American Cancer Society.

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Taking into account our earlier studies, we conclude that most cases of colorectal carcinogenesis are characterized by enhanced expression of MMP-7, -13, -3 and the gelatinases, whereas MMP-1-expression is very inconsistent and not overexpressed in many cases. MMP-7 inhibition as well as inhibition of MMP-13 and MMP-3 may be a useful preventive or therapeutic adjunct in colorectal cancer.