We speculated that knocking down of the expression of ESM1 could enhance the phenotypic changes, increase the abilities of migration and invasion by increasing over-expression of MMP-9 and down-expression of TIMP-1, and aggressiveness of distant metastasis of prostate cancer cells, which indicated a potential role of ESM1 in regulating the progress of prostate cancer. The gene discussed is MMP9; the disease is Familial prostate cancer.