Elevated level of circulating matrix metalloproteinase-9 in patients with lung cancer

The 72 kDa matrix metalloproteinase (MMP-2) and the 92 kDa matrix metalloproteinase (MMP-9), are type IV collagenases that have been implicated as important factors in cancer invasion and metastasis formation. We have used quantitative zymography and computer-assisted image analysis to measure the levels of MMP-9 and MMP-2 in 19 samples of serum of lung cancer patients and in 23 samples of normal serum. Mean levels of MMP-9 were significantly elevated in cancer samples compared with normal sera (1.33 +/- 0.61 muU mul(-1) vs. 0.37 +/- 0.10 muU mul(-1), P < 0.0001). MMP-2 levels did not differ significantly in these two groups. However, there was no significant correlation between serum MMP-9 activity and the disease stage. We found that circulation levels of MMP-9 in lung cancer patients is 3 .6-fold higher than in healthy volunteers, however, we do not consider this elevation to be a direct reflection of MMP-9 over-production by tumour cells.