The comparison of the expressions of four MMPs in prostate adenocarcinoma (PRAD) and normal tissues was analyzed in Gene expression profiling interactive analysis (GEPIA), and it was found that the expression of MMP2 in normal tissues was higher than that in PRAD, while the expression of MMP7 and MMP9 in PRAD was higher than that in normal tissues, and no significant difference was observed in MMP1 (http://gepia.cancer-pku.cn/) (Fig. 2 c-f). The gene discussed is MMP9; the disease is prostate adenocarcinoma.