626. A Novel Prostate-Specific Adenovirus for Gene Expression in Hormone-Sensitive and Hormone-Refractory Prostate Cancer Cells

Abstract

To develop a transcriptional regulatory sequence for prostate-specific transgene expression that is more potent then the ones currently used in experimental and clinical prostate cancer gene therapy, we constructed various recombinant expression control sequences comprising the TARP promoter (TARPp) and the PSA enhancer (PSAe) and/or the PSMA enhancer (PSMAe). Transcriptional activities of the expression control sequences were examined by luciferase reporter gene assays on transiently transfected cells. We found that gene expression controlled by a chimeric regulatory sequences comprising PSAe linked to PSMAe, in turn linked to TARPp (PPT) is highly prostate-specific and active in prostate cancer cells both in the presence and absence of testosterone. Since prostate cancer patients are often treated by androgen withdrawal, it may be beneficial to the patient to use a regulatory sequence that results in high transgene expression also in the absence of testosterone. Recombinant adenoviruses with the PPT sequence in the E1 position of an E1/E3-deleted adenovirus serotype 5 vectors were constructed. A DNA insulator from the mouse H19 imprinting control region was inserted directly upstream of the expression cassette to protect the transcriptional integrity of PPT from interfering adenoviral sequences. The produced viruses confer prostate-specific transgene expression when screened on cell lines of various origins. We believe that an adenovirus with E1A and/or other therapeutic gene expression, controlled by the H19 insulator-shielded PPT regulatory sequence, is a promising candidate for prostate cancer gene therapy.