Acta Pharmacologica Sinica 2008 November; 29 (11): 1334-1341; doi: 10.1111/j.1745-7254.2008.00887.x

Aim: Studies of eukaryotes have yielded 2 translation initiation mechanisms: a classical cap-dependent mechanism and a cap-independent mechanism proceeding through the internal ribosomal entry site (IRES). We hypothesized that it might be possible to identify compounds that may distinguish between cap-dependent translation and cap-independent IRES-mediated translation.

Methods: Interleukin-6 (IL-6) is a pleiotropic cytokine that is associated with tumor metastasis and prostate cancer. We evaluated the mechanism and effect of 17-(allylamino)-17-demethoxygeldanamycin (17AAG), a novel inhibitor of heat shock protein 90 (Hsp90), on the IL-6 gene expression in human prostatic carcinoma (PC-3) cells.

Results: Although the IL-6R is ubiquitously expressed by prostatic epithelium cells, the IL-6 expression is only found in advanced prostatic carcinoma cells, such as PC-3 and DU145. Further studies using RT_PCR indicated that 17AAG downregulated the gene expression of IL-6. ELISA and the transient gene expression assay revealed that 17AAG blocked the stimulation of PMA of IL-6 gene expression in PC-3 cells. The PMA-induced IL-6 gene expression is dependent on the NF-κB response element. However, the effect of 17AAG appears to be mediated via a region located at _149 to +8 bp upstream of the transcriptional starting site of the IL-6 gene, and might not be through the NF-κB signaling pathway.

Conclusion: The present study reveals that IL-6 is transcriptionally downregulated in human prostatic carcinoma cells in response to 17AAG. This result suggests the presence of a novel Hsp90 mediation pathway that is involved in the deregulation on the transcription of the human IL-6 gene in human prostate cancer.

Keywords: prostate; interleukin-6; heat shock protein 90; 17-(allylamino)-17-demethoxygeldanamycin; phorbol 12-myristate 13-acetate; promoter; prostatic carcinoma cells