Androgen receptor represses the neuroendocrine transdifferentiation process in prostate cancer cells

Abstract

Androgen-ablation therapy is an effective method for treating prostate cancer. However, prostate tumors that survive long-term androgen-ablation therapy are classified as androgen-independent as they proliferate in the absence of androgens, and they tend to be enriched for neuroendocrine (NE) cells. Androgen withdrawal causes androgen-dependent prostate cancer cells to adopt a pronounced NE phenotype, suggesting that androgen receptor (AR) represses an intrinsic NE transdifferentiation process in prostate cancer cells. In this report we show that short interfering RNA-induced AR silencing induced a NE phenotype that manifested itself in the growth of dendritic-like processes in both the androgen-dependent LNCaP and androgen-independent LNCaP-AI human prostate cancer cells. Western blot analysis revealed that neuronal-specific enolase, a marker of the neuronal lineage, was increased by AR knockdown in LNCaP cells. The expression levels of the neuronal-specific cytoskeletal proteins β-tubulin III, nestin, and glial acidic fibrillary protein were also characterized in AR knockdown cells. Most interestingly, AR silencing induced β-tubulin III expression in LNCaP cells, while AR knockdown increased glial acidic fibrillary protein levels in both LNCaP and LNCaP-AI cells. Lastly, AR silencing reduced the proliferative capacity of LNCaP and LNCaP-AI cells. Our data demonstrate that AR actively represses an intrinsic NE transdifferentiation process in androgen-responsive prostate cancer cells and suggest a potential link between AR inactivation and the increased frequency of NE cells in androgen-independent tumors.