Amino-terminus domain of the androgen receptor as a molecular target to prevent the hormonal progression of prostate cancer

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Abstract
Prostate cancer has a propensity to metastasize to the bone. Currently the only effective systemic treatment for these patients is androgen ablation therapy. However, the tumor will invariably progress to an androgen‐independent stage and the patient will succumb to his disease within approximately 2 years. The earliest indication of hormonal progression is the rising titer of serum prostate specific antigen. Current evidence implicates the androgen receptor (AR) as a key factor in maintaining the growth of prostate cancer cells in an androgen‐depleted state. Under normal conditions, binding of ligand activates the receptor, allowing it to effectively bind to its respective DNA element. However, AR is also transformed in the absence of androgen (ligand‐independent activation) in prostate cells via multiple protein kinase pathways and the interleukin‐6 (IL‐6) pathway that converge upon the N‐terminal domain of the AR. This domain is the main region for phosphorylation and is also critical for normal coregulator recruitment. Here we discuss evidence supporting the role of the AR, IL‐6 and other protein kinase pathways in the hormonal progression of prostate cancer to androgen independence and the mechanisms involved in activation of the AR by these pathways. Receptor‐targeted therapy, especially potential drugs targeting the N‐terminal domain, may effectively prevent or delay the hormonal progression of AR‐dependent prostate cancer. J. Cell. Biochem. 98: 36–53, 2006.