Purpose: Membrane-type matrix metalloproteinases are recently described proteolytic enzymes belonging to the matrix metalloproteinase family. Initial studies have indicated that membrane-type matrix metalloproteinases are involved in tumor invasion and metastasis. Membrane-type 1 matrix metalloproteinase is the first membrane-type matrix metalloproteinase to be described. The aim of this study was to investigate the expression of membrane-type 1 matrix metalloproteinase mRNA in colorectal cancer.
Methods: Samples were collected from surgical specimens of patients with colorectal adenocarcinoma and were immediately frozen in liquid nitrogen and stored at -80 degrees C until processed. Both normal and cancer tissue was taken from each patient. TNM stage, tumor differentiation, mucin production, and vascular invasion were assessed. Northern blotting was used to quantify membrane-type 1 matrix metalloproteinase mRNA levels in the samples using a membrane-type 1 matrix metalloproteinase cDNA clone. X-ray film images were digitized and densitometry was used to quantify bands. All samples were normalized against 18S rRNA levels. Results are expressed as the ratio of cancer to normal tissue levels. Statistical analysis was performed using analysis of variance, with P < 0.05 accepted as the level of significance.
Results: A total of 32 samples were prospectively analyzed. The correlation between TNM stage and increased expression of membrane-type 1 matrix metalloproteinase mRNA in cancer tissue over normal tissue is expressed in the mean ratio of cancer to normal tissue expression for Stages I through IV, respectively: 1.4 +/- 0.2 (12 patients); 4.1 +/- 2.6 (8 patients); 3.4 +/- 3 (7 patients); and 4.5 +/- 5 (5 patients). Stage I is significantly different from Stages II and IV (P < 0.05). These preliminary results show an overall increasing trend in membrane-type 1 matrix metalloproteinase expression with increasing tumor stage. However, there was no correlation between membrane-type 1 matrix metalloproteinase expression and mucin production, degree of tumor differentiation, or vascular invasion.
Conclusion: Preliminary results indicate that membrane-type 1 matrix metalloproteinase levels correlate with increasing tumor stage.