Taking into consideration the experiments performed in prostate cancer cell lines we reveal that hypomethylation of IGF2-DMR0 is a crucial point in deregulation of IGF2 in prostate cancer and that the transcription factor KLF4 is a potent co-factor involved in impairment of IGF2 expression during prostate carcinogenesis. This evidence concerns the gene KLF4 and Familial prostate cancer.