miR-1 has been described as a suppressor of prostate cancer.16, 17, 19 We previously reported the loss of AR-mediated activation of miR-1 and subsequent activation of SRC-stimulated prostate cancer bone metastasis.20 Although activated AR stimulates miR-1 transcription by binding to its promoter,20 our present results support a model where AR might function as a transcription factor that activates the KLF4-miR-1 signaling pathway to persist the tumor-suppressive role of miR-1. This evidence concerns the gene KLF4 and prostate carcinoma.