Gelatinase and inhibitor expression in soft tissue sarcomas: lack of correlation with distant metastasis

The predominant mode of death for most patients with soft tissue sarcomas (STS) remains distant metastasis (DM). Current clinical predictors of DM are unreliable. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) correlate with biologic aggression in other tumors. The gene expression of the gelatinase, MMP-2 and MMP-9, and their respective inhibitors, TIMP-1 and TIMP-2, in STS was evaluated. Twelve fresh-frozen surgical specimens from patients with large (>5 cm) STS were analyzed. Six patients developed DM while 6 survived disease-free (DFS) at a minimum follow-up of 13 months. Following mRNA isolation, reverse transcription-polymerase chain reaction was performed using primers for MMP-2, MMP-9, TIMP-1, and TIMP-2. Gene expression was determined by band densitometry. Ratios of MMP-9/TIMP-1 and MMP-2/ TIMP-2 gene expression as well as MMP-2 protein activation ratio (active/inactive enzyme determined by gelatin zymography) were analyzed for correlation with DM and DFS. MMP-2 gene was expressed in 12 specimens, while MMP-9 was detectable in 9. Relative levels of MMP-2 and MMP-9, MMP2/TIMP-2 ratio, and MMP-9/TIMP-1 ratio were not significantly correlated with DM. Poor DFS was significantly correlated with high MMP-9/TIMP-1 ratio (p = 0.02). Active MMP-2 protein was detected in 12 specimens, while active MMP-9 protein was detected in 2. No association was found between MMP-2 protein activation ratio and DM or DFS. While MMP-2 gene expression and protein activity occurred in these 12 specimens, gelatinase/inhibitor ratios (for both MMP-2 and MMP-9) appear to be poor predictors of DM in STS.