Gene therapy for prostate cancer targeting transcription factor E2F/DRTF

The heterodimeric transcription factor E2F/DRTF plays a key role in integrating the transactivation of DNA replication-associated genes with cell cycle progression. Strictly regulated in a tissue-specific manner, the prostate-specific antigen promoter (PSAP) can be used to direct prostate-specific gene therapy. Employing PSAP and taking advantage of dominant negative suppression and antisense counteraction, we constructed three PSAP-driven plasmids targeting E2F/DRTF: PSAP-E2FL, PSAP-E2FS, and PSAP-antiE2F-1, which, upon induction, would express two truncated E2F-1 proteins lacking the DNA-binding domain and an antisense E2F-1 transcript. Lipofection-mediated gene transfers were performed in three prostate cancer cell lines (DU-145, PC-3 and LNCaP) and six cell lines of other origin (HL-60, KG-1: Hep G2, Cos-l, NCI H460, and SW480). In DU-145, PC-3, and LNCaP, PSAP-E2FL exhibited a growth inhibition of >99%, 94.8%, and 36.9%, respectively; PSAP-E2FS induced growth inhibition at 48.3%, 43.7%, and 34%; PSAP-antiE2F-1 suppressed the growth by 9.5%, 16.3%, and 46.8%. None of these constructs showed significant growth inhibition in cells of hematopoietic (HL-60, KG-1), hepatic (Hep G2), renal (Cos-l), pulmonary (NCI H460) or colon (SW480) origin. Examination on DU-145 transfectants by RT-PCR revealed that PSAP-E2FL suppressed the expression of c-myc and DNA polymerase-alpha by 82.5% and 65.8%, respectively. The inhibition of DNA synthesis was further confirmed by an ill situ BrdU incorporation analysis in DU-145 and PC-3 transfectants. Without damaging other cells, the PSAP-driven genetic constructs targeting E2F/DRTF proved to be potent in inducing tissue-specific cytotoxicity solely in cells of prostate origin.