Distinct pattern of matrix metalloproteinase 9 and tissue inhibitor of metalloproteinase 1 mRNA expression in human colorectal cancer and liver metastases

The matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are perceived as essential for tumour invasion and metastasis. In the present study, we compare the topographical pattern of MMP-9 and TIMP-1 expression in colorectal cancer and liver metastasis by in situ hybridisation. TIMP-1 mRNA was detected in all 26 colorectal cancers examined, while only 18 out of 26 (69.2%) were positive for MMP-9. Both MMP-9 and TIMP-1 mRNA were observed in all ten liver metastases but were absent in three adenomas and in all normal colonic mucosa and liver. There was no association between MMP-9 or TIMP-1 mRNA expression and degree of differentiation or size of Tumours. MMP-9 and TIMP-1 mRNA were similarly observed in the peritumour stroma cells rather than in tumour cells themselves. MMP-9 mRNA positive cells were round and identified as macrophages by immunostaining with an anti-macrophage antibody (KP1), while TIMP-1, mRNA was detected in spindle-shaped stromal cells. In liver metastases, MMP-9 localised within peritumour stroma or at the interface between the tumour stroma and normal liver, whereas TIMP-1 mRNA was located throughout the malignant tumour stroma. Our data demonstrate a distinct pattern of MMP-9 and TIMP-1 mRNA expression in colorectal cancer and liver metastases suggesting distinct cellular origins as well as separate patterns of regulation.