Introduction: Numerous studies have evaluated the association between the matrix metalloproteinase 9 (MMP-9) and prostate cancer (PCa) risk. However, these studies have yielded conflicting results.
Evidence acquisition: A comprehensive search was conducted through researching MEDLINE, PubMed, Web of Science, and EMBASE, and a total of 10 studies including 1059 cases were included on the basis of inclusion criteria.
Evidence synthesis: A meta-analysis was performed to obtain a summary of estimated odds ratios (ORs) and 95% confidence intervals (CIs) of MMP-9 for PCa, with attention to study quality and publication bias. MMP-9 by immunohistochemistry was significantly associated with increased diagnosis of PCa (OR=7.91; 95% CI: 5.27-11.89; P<0.00001). Subgroup-analysis showed that findings did not substantially change when only Caucasians or Asians (OR=5.87; 95% CI: 3.38-10.20; P<0.00001) or (OR=11.80; 95% CI: 6.60-21.08; P<0.00001) were considered. There was also no significant publication bias observed.
Conclusions: Our findings provide further evidence that the expression of MMP-9 contribute to PCa risk. MMP-9 protein overexpression was found in prostate cancers, low expression in any of the normal tissues or in benign prostatic tissue. MMP-9 is potentially an important prostate tumor marker.