Histone deacetylase inhibitors suppress telomerase reverse transcriptase mRNA expression in prostate cancer cells

Telomerase activity is involved in cellular immortality. We have recently demonstrated that telomerase activity is closely associated with cell proliferation in prostate cancers. Telomerase is composed primarily of the catalytic subunit (hTERT) and the RNA template (hTERC), and hTERT expression is regulated by several factors such as c-MYC and p21(Waf1). Histone deacetylase (HDAC) inhibitors are known to modulate transcription and exhibit antiproliferative effects on cancer cells. The present study was designed to evaluate the effects of HDAC inhibitors on hTERT mRNA expression in prostate cancer cells. LNCaP and PC-3 cells were treated with HDAC inhibitors, trichostatin A (TSA) and sodium butyrate (NaB); mRNA expression and telomerase activity were evaluated by RT-PCR and the TRAP assay, respectively. In LNCaP cells, hTERT mRNA expression was suppressed at 1 and 3 hr after treatment with 1 microM TSA and 4 mM NaB, respectively, followed by inhibition of telomerase activity. The inhibition of hTERT mRNA expression preceded suppression of cell proliferation. In PC-3 cells, TSA and NaB also inhibited cell proliferation, hTERT mRNA expression and telomerase activity. In both cell lines, TSA and NaB had no effect on hTERC expression, or on expression of c-myc and p21(Waf1) mRNA. These effects of TSA and NaB were unlikely to be consequences of cell cycle arrest, apoptosis, or cell differentiation. Thus, HDAC inhibitors down-regulated telomerase activity via suppression of hTERT mRNA expression. Our study identified a novel mechanism for the antiproliferative effects of HDAC inhibitors on prostate cancer cells.