Overexpression of tissue inhibitors of metalloproteinase-1 and -2 in the stroma of gastric cancer

The fundamental event of cancer invasion and metastasis is the complicated interaction of cancer cells with host cells, in which event, a number of proteases and their inhibitors are involved. Matrix metalloproteinases are the potent proteases in degrading the basement membrane and extra cellular matrix and are inhibited by specific endogeneous inhibitors, tissue inhibitors of metalloproteinases-1(TIMP-1) and TIMP-2. The expression of mRNA for TIMP-1 and -2 was investigated by Northern blot analysis in specimens taken from 27 patients with primary gastric adenocarcinoma; 25 samples from the primary site, six from the metastatic lymph nodes and two from the peritoneal fluids. The expression for TIMP-1 and -2 was compared in primary gastric cancer tissues, metastatic lymph nodes and normal gastric mucosae. TIMP-1 mRNA was overexpressed in 24 (96%) out of 25 primary cancer tissues compared with the paired normal mucosae, while TIMP-2 was in 10 (40%). In six specimens of metastatic lymph nodes, TIMP-1 and -2 were overexpressed in 6 (100%) and 4 (67%) specimens, respectively. Of two specimens prepared from the peritoneal fluids, all specimens overexpressed TIMP-1 compared with the those of primary cancer tissues, while one (50%) specimen overexpressed TIMP-2. Immunohistochemical staining was done to investigate the localization of TIMP-1 and -2, demonstrating that the immunoreactivity for TIMP-1 and -2 was clearly detected in the cytoplasm of the stromal cells. These results suggest that both TIMP-1 and -2 are overexpressed by stromal cells in most of primary and some metastatic gastric cancer tissues and that TIMP-1 and TIMP-2, produced by stromal cells, may play an important role in inhibiting the proteolytic activity of matrix metalloproteinases originated from cancer cells, in gastric cancer.