To further test whether MMP9 expression correlated with aggressive behavior of prostate cancer cells and to test whether a correlation existed between MMP9 and PDEF expression in human prostate cancer specimens, we evaluated MMP9 expression in the same tissue microarray slides containing 40 cores of prostate cancer and 9 cores of normal prostate that were used for PDEF expression analysis. The gene discussed is SPDEF; the disease is prostate cancer.