Moreover, we provide the first evidence that hydrogen peroxide serves as a central mediator in regulating MMP-3 expression, with opposite results in the microenvironments of fibroblasts and prostate cancer cells, through the direct inhibition of mmp-3 promoter activity via nuclear factor-κB (NF-κB) signaling pathway in CAFs and downregulation of thrombospondin 2, an MMP-3 suppressor in prostate cancer cells through microRNA (miRNA) regulation. The gene discussed is NFKB1; the disease is prostate cancer.