Regulation of human prostate-specific antigen gene expression in transgenic mice: evidence for an enhancer between the PSA and human glandular kallikrein-1 genes

The human prostate-specific antigen (PSA) and glandular kallikrein-1 (hGK-1, also known as hK2) genes are tandemly located on chromosome 19, separated by a 12-kb intergenic region. The coordinate regulation of these two genes suggests the presence of common regulatory elements responsible for tissue specificity and/or levels of expression within this region. To identify such regulatory elements, we generated two sets of transgenic mice, which had incorporated either the PSA gene alone or together with the intergenic region. Both sets of transgenics exhibit remarkably prostate-specific expression of the transgene. However, the presence of the intergenic region abrogates the dependence on high PSA gene copy-number for high levels of PSA expression. This suggests the existence of a positive regulatory element in the intergenic region. By using a previously identified distal enhancer element of PSA (termed DEE 1) as a probe, we identified a cross-hybridizing fragment, which we termed DEE 2, in the intergenic region. Sequence analysis shows that DEE 2 is 76% identical to DEE 1, and it includes a putative androgen-responsive element. Here, we propose a model to illustrate how the two enhancers may work to regulate the transcription of PSA and hK2.

A transgenic strategy for analyzing the regulatory regions of the human prostate-specific antigen gene: potential applications for the treatment of prostate cancer (Review)

Prostate-specific antigen (PSA) has been used clinically as a marker for the diagnosis and staging of prostate cancer due to its specific expression in prostate epithelial cells. In addition to its medical importance, its complex hormonal and tissue-specific regulation makes it an attractive model to study gene regulation. Two approaches have been applied to the identification of regulatory regions which confer this specific expression pattern. In vitro analysis of the regulatory regions of the human PSA gene using promoter reporter constructs and tumor cell lines has revealed a number of the DNA sequences involved in the hormone-dependent expression of PSA. We have pursued an alternative in vivo approach using transgenic animal technology, which is the focus of this review. Using this second approach, a transgenic mouse was generated using a 14 kilobase (kb) region of the human PSA gene encompassing the coding region and intervening sequences as well as 6 kb of upstream sequence and 2 kb of downstream sequence. This genomic DNA clone confers a PSA expression pattern in mice which appears to be very similar if not identical to that of humans, allowing us to investigate tissue-specificity and developmental regulation of PSA expression. In addition, these mice, for which PSA is a self-antigen, provide a model to test the feasibility and efficacy of PSA-directed immunotherapy for prostate cancer. The further identification of the PSA regulatory regions important for tissue-specificity may ultimately allow the design of new therapeutics for the treatment of prostate cancer.