Imbalance between Matrix Metalloproteinase 9 and Tissue Inhibitor of Metalloproteinases 1 Expression by Tumor Cells Implicated in Liver Metastasis from Colorectal Carcinoma.

We have evaluated the degree of MMP-9 and TIMP-1 messenger RNA (mRNA) expressions according to cell types in tumor tissues, and evaluated the implication of balance between the MMP-9 mRNA and the TIMP-1 mRNA expression in liver metastasis using orthotopic-implanted colon cancer in nude mouse, and also in 47 patients with colorectal cancer. The grade of MMP-9 or TIMP-1 mRNA expression was classified into 4 categories according to positive cell ratio. A higher grade of MMP-9 mRNA expression in tumor cells was correlated with liver metastasis in the experimental colon cancer, but was not statistically correlated in the clinical colorectal cancer. In contrast, the expression of TIMP-1 mRNA in the stromal cells of human colorectal cancer was correlated with liver metastasis. In both experimental and clinical colorectal cancer, a balance between the expression of MMP-9 mRNA and that of TIMP-1 mRNA was correlated with the occurrence of liver metastasis. The imbalance of MMP-9 dominance in tumor cells was implicated in liver metastasis. However, there was no significant relationship between the incidence of liver metastasis and the expression patterns of MMP-9 and TIMP-1 mRNA in the stromal cells. These results suggest that the balance between the expressions of MMP-9 and TIMP-1 in the tumor cells is more closely related to tumor biological behavior rather than the balance in the stromal cells.