MMP-1 (collagenase-1) expression in primary colorectal cancer and its metastases

The role of MMP-1 (collagenase-1) in the development of a metastatic phenotype in colorectal cancer (CRC) has not been fully studied. The aim of this study was to investigate the mechanisms involved in the dissemination of CRC by examining the expression of MMP-1 in the primary tumours and their metastases, with special reference to standard clinicopathological features and disease outcome.

Surgical specimens from the primary tumours (P) and their metastatic (M) lesions were available from 30 patients with Stage II, III and IV CRC, and were subjected to immunohistochemical (IHC) staining for MMP-1. Both cytoplasmic expression in cancer cells (CC) and stromal (ST) expression were related to pertinent clinical and follow-up data.

In a pairwise comparison of P-M pairs, CC expression (but not ST expression) in P and M was significantly different (Wilcoxon rank test, p=0.037). Strong CC expression in P was significantly related to the presence of lymph node involvement at diagnosis (p=0.008). CC expression in M was intense only in metachronous metastases (Stage II/III disease) but never in synchronous metastases (Stage IV) (p=0.034). There was a significant down-regulation of CC (p=0.004) in liver metastasis (n=9) in comparison with all other metastatic sites (n=21). ST expression in P (but not in M) showed a linear decrease in parallel with increasing stage (p=0.028 for linear trend). MMP-1 expression was not significantly associated with any other clinicopathological variables, including age, gender, carcinoembryonic antigen (CEA) or patients' disease-free or overall survival.

These data suggest that MMP-1 may play an important role in tumour invasion and metastasis of CRC.