By methylation-sensitive arbitrarily-primed PCR (MSe-AP-PCR) we have detected abnormal methylation of a fragment of BIN1 promoter region CGI in BC and studied its methylation patterns in primary breast and prostate cancer samples as well as in the MCF7 and T47D BC cell lines and DU145 and LNCaP prostate cancer cell lines. The gene discussed is BIN1; the disease is Familial prostate cancer.