In vivo regulation of hTERT expression and telomerase activity by androgen

Purpose: The most effective therapy for metastatic prostate cancer is androgen deprivation. Genes activated directly or possibly even indirectly by this steroid hormone represent potential targets for anticancer therapy. One such gene may be hTERT, which encodes the catalytic subunit of telomerase. In prostate cancer cells telomerase is activated, permitting sustained proliferation. Therefore, we tested whether hTERT gene expression is modulated in prostate cancer cells in vitro and in vivo by androgens. Materials and Methods: Transcriptional activation of hTERT during androgen stimulation was assayed by luciferase assays using the hTERT promoter fused to the luciferase gene and by reverse transcriptase-polymerase chain reaction to detect endogenous hTERT mRNA in LNCaP cells. hTERT mRNA levels and telomerase activity were also measured in CWR22 prostate cancer cells implanted in mice that were subsequently castrated and left untreated or administered androgen. Results: We report that the endogenous hTERT promoter is activated during the administration of androgen to androgen sensitive LNCaP prostate cancer cells. However, this effect was indirect since an hTERT promoter construct was not activated by androgens and transcription of the endogenous gene was not stimulated early enough in cultured cells to be considered a direct target of this steroid hormone. Importantly in an in vivo model of human prostate cancer androgen deprivation led to a decrease in hTERT expression, followed by a decrease in telomerase activity, which was reversed by a single administration of androgen. Conclusions: The hTERT gene is regulated in human prostate cancer cells in vivo by androgens.