Identification of androgen-responsive genes that are alternatively regulated in androgen-dependent and androgen-independent rat prostate tumors.

The vast majority of androgen-dependent prostate tumors progress toward incurable, androgen-independent tumors. The identification of androgen-responsive genes, which are still actively transcribed in the tumors of patients who have undergone androgen ablation, may shed light on the molecular mechanisms underlying this phenomenon. To address this question, we chose the Dunning R3327 rat model system, in which the progression from androgen-dependent to -independent tumors is represented by several transplantable prostate-derived tumors. Gene expression profiles were analyzed in normal rat prostates and in the prostates of rats 14 days after castration by use of microarrays containing approximately 5,000 oligonucleotides, together representing more than 4,800 known rat genes. These expression profiles were compared with similarly obtained expression profiles of androgen-dependent and androgen-independent rat prostate tumors. By doing so, a series of known and novel prostate cancer-associated androgen-responsive genes was identified. Within this series, we were able to identify several clusters of genes that are differentially regulated in the various prostate tumors. These genes may serve as (i) novel prognostic identifiers and (ii) novel therapeutic targets.