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

The 72 kDa matrix metalloproteinase (MMP-2) and the 92 kDa matrix metallopr oteinase (MMP-9), are type IV collagenases that have been implicated as imp ortant factors in cancer invasion and metastasis formation. We have used qu antitative zymography and computer-assisted image analysis to measure the l evels 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 ele vated 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 s ignificantly in these two groups. However, there was no significant correla tion between serum MMP-9 activity and the disease stage. We found that circ ulation 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 dir ect reflection of MMP-9 over-production by tumour cells.