['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.', 'Quantitative IL-6 and IL-6 receptor (IL-6R) expressions were assessed using RT-PCR. The deregulation of 17AAG and phorbol 12-myristate 13-acetate (PMA) on the IL-6 gene was determined by ELISA and transient gene expression assays using an IL-6 reporter vector.', '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-kappaB 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-kappaB signaling pathway.'] Is expression of interleukin-6 downregulated by 17- ( allylamino ) -17-demethoxygeldanamycin in human prostatic carcinoma cells?