We also discover a novel role of TRIM28 and its B box in the ORF2p-mediated cDNA synthesis, which is supported by measuring the length of cDNA products and de novo L1 inserts in transiently transfected cultured cells and by analysis of de novo tumor-specific L1 inserts in tumors of patients with endometrial cancer, prostate cancer, and ovarian cancer. This evidence concerns the gene TRIM28 and Familial prostate cancer.