Matrix metalloproteinases 2 and 9 (gelatinases A and B) expression in malignant mesothelioma and benign pleura

Abstract

Matrix metalloproteinases (MMPs), in particular the gelatinases (MMP-2 and -9), play a significant role in tumour invasion and angiogenesis. The expression and activities of MMPs have not been characterised in malignant mesothelioma (MM) tumour samples. In a prospective study, gelatinase activity was evaluated in homogenised supernatants of snap frozen MM (n=35), inflamed pleura (IP, n=12) and uninflammed pleura (UP, n=14) tissue specimens by semiquantitative gelatin zymography. Matrix metalloproteinases were correlated with clinicopathological factors and with survival using Kaplan-Meier and Cox proportional hazard models. In MM, pro- and active MMP-2 levels were significantly greater than for MMP-9 (P=0.006, P<0.001). Active MMP-2 was significantly greater in MM than in UP (P=0.04). MMP-2 activity was equivalent between IP and MM, but both pro- and active MMP-9 activities were greater in IP (P=0.02, P=0.009). While there were trends towards poor survival with increasing total and pro-MMP-2 activity (P=0.08) in univariate analysis, they were both independent poor prognostic factors in multivariate analysis in conjunction with weight loss (pro-MMP-2 P=0.03, total MMP-2 P=0.04). Total and pro-MMP-2 also contributed to the Cancer and Leukemia Group B prognostic groups. MMP-9 activities were not prognostic. Matrix metalloproteinases, and in particular MMP-2, the most abundant gelatinase, may play an important role in MM tumour growth and metastasis. Agents that reduce MMP synthesis and/or activity may have a role to play in the management of MM.

Figure 1

Gelatin zymogram of malignant mesothelioma (MM), inflamed pleura (IP) and uninflamed pleura (UP). Snap-frozen samples were homogenised and the supernatant proteins resolved in a gelatin preimpregnated polyacrylamide gel. Gels were developed to show clear bands of gelatinolysis, correlating with the latent, pro- and active isoforms of MMP-2 and -9.

Figure 2

Boxplots showing the differences in MMP activity between MM (n=22), UP (n=12) and IP (n=15). Data are shown for pro-MMP-9 (A), active MMP-9 (B), pro-MMP-2 (C) and active MMP-2 (D). Horizontal bars represent the median values, boxes the interquartile range, vertical bars the 10–90% range and solid circles the outliers. MMP enzyme activity was measured with semiquantitative gelatin zymography and is expressed by arbitrary densitometry units per milligram protein.

Figure 3

Scatterplot showing the relation between survival and total MMP-2 activity (sum of pro-MMP-2 and active MMP-2 band arbitrary densitometry units). There was a trend towards worse survival in patients with increasing values (P=0.08, Cox proportional hazards).