PROSTATE TISSUE-SPECIFICITY OF THE PROSTATE-SPECIFIC ANTIGEN PROMOTERISOLATED FROM A PATIENT WITH PROSTATE-CANCER

We have cloned and characterized a 620-bp fragment of DNA that flanks 5' of the prostate-specific antigen (PSA) gene from a prostate cancer patient, Using DNA transfection, the efficacy of this putative promote r in regulating gene expression was quantitated in several prostate an d nonprostate tissue cell lines, Our results demonstrated that the 620 -dp DNA fragment actively drives gene expression in LNCaP, a PSA-produ cing prostate tumor cell. line, No promoter activity was detected in t he non-PSA-producing prostate tumor lines, DU145 and PC-3, nor in a re nal (R11) or breast (MCF-7) cancer cell line, Furthermore, the promote r activity could be regulated in vitro by androgen stimulation, Dihydr otestosterone (DHT) concentrations between 3 and 30 nM induced the hig hest promoter activity in the transfected LNCaP cells, which parallels the expression profile of the androgen receptor in LNCaP cells, In ad dition, our PSA promoter exhibited competitive inhibition of the endog enous genomic PSA promoter in transfected LNCaP cells, suggesting that prostate cell-specific DNA-binding proteins are required to activate the PSA promoter, A cytomegalovirus IE1 promoter (CMV promoter) attach ed to the 5'-flanking region of the PSA promoter increased its potency four- to five-fold while retaining tissue specificity, Our data sugge st that a strong tissue-specific negative regulatory element capable o f overriding the nonspecific CMV promoter is present in the PSA promot er and confers its tissue specificity, The use of a highly specific pr omoter-driven gene vector will allow selective expression of therapeut ic genes within PSA-producing prostate cancer cells, providing a uniqu e strategy for prostate cancer gene therapy.