DU-145 and PC-3 human prostate cancer cell lines express androgen receptor: implications for the androgen receptor functions and regulation

The majority of human prostate cancer cell lines, including the two "classical" cell lines DU-145 and PC-3, are reported to be androgen receptor (AR)-negative. However, other studies have provided evidence that the DU-145 and PC-3 cell lines express AR mRNA. These contradictory observations prompted us to investigate whether DU-145 and PC-3 cell lines express the androgen receptor. Using antipeptide antibodies directed against three distinct regions of the human AR protein and an improved method to detect AR protein in immunoblotting, we report that DU-145 and PC-3 cell lines express AR protein. We found that the relative levels of the AR mRNA and protein that were detected in DU-145 and PC-3 cell lines were lower than the LNCaP, an AR-positive cell line. Moreover, the antibody directed against the non-variant region (amino acids 299-315), but not the variant N- or C-terminal region (amino acids 1-20 and 900-919, respectively) of the human AR protein, detected the expression of AR in all prostate cancer cell lines. Notably, treatment of these cell lines with dihydrotestosterone (DHT) resulted in measurable increases in the AR protein levels and considerable nuclear accumulation. Although, treatment of DU-145 and PC-3 cells with DHT did not result in stimulation of the activity of an AR-responsive reporter, knockdown of AR expression in PC-3 cells resulted in decreases in p21(CIP1) protein levels, and a measurable decrease in the activity of the p21-luc-reporter. Our observations demonstrate the expression of AR protein in DU-145 and PC-3 prostate cancer cell lines.     

Adapting genetic regulatory models by genetic programming

In this paper, we focus on the task of adapting genetic regulatory models based on gene expression data from microarrays. Our approach aims at automatic revision of qualitative regulatory models to improve their fit to expression data. We describe a type of regulatory model designed for this purpose, a method for predicting the quality of such models, and a method for adapting the models by means of genetic programming. We also report experimental results highlighting the ability of the methods to infer models on a number of artificial data sets. In closing, we contrast our results with those of alternative methods, after which we give some suggestions for future work.     

Nuclear exclusion of the androgen receptor by melatonin

Androgen receptors (AR) play a crucial role in androgen-mediated processes and prostate cancer progression. The pineal hormone melatonin attenuates the androgen-dependent growth of benign and cancer prostate epithelial cells in vitro and may reverse clinical resistance to androgen ablation therapy in patients progressing on gonadotropin releasing hormone (GnRH) analogue. Where along the AR cascade does melatonin act remains to be determined. The effects of melatonin on AR localization, level and activity were assessed using androgen-insensitive prostate carcinoma PC3 cells stably transfected with a wild-type AR-expressing vector (PC3-AR).AR was localized to the PC3-AR cell nucleus in the absence of dihydrotestosterone (DHT). Melatonin caused a robust exclusion of the AR from the cell nucleus to the cytoplasm. The nuclear export inhibitor, leptomycin B prevented this process. The exclusion was selective since melatonin had no such effect on the nuclear localization of estrogen receptors alpha (ERalpha) in these cells.Melatonin also caused nuclear exclusion of the AR in the presence of DHT. In addition, it attenuated androgen induced reporter gene activity in PC3 cells co-transfected with the human AR and AR reporter plasmids. Elevated androgen concentrations counteracted melatonin's effects. Melatonin did not decrease AR level or androgen binding in the cells.The nuclear localization of the AR is a hallmark of its cellular activity. These data point to AR nuclear exclusion as a possible mechanism to attenuate androgen responses in target tissues.     

ARA67/PAT1 functions as a repressor to suppress androgen receptor transactivation

The androgen receptor (AR) may recruit multiple coregulators for proper or optimal transactivation. Here we report the identification and characterization of ARA67/PAT1 as an AR coregulator from a prostate cDNA library. ARA67/PAT1 was screened out as an AR N terminus interacting protein. Interaction mapping shows that the cooperation of multiple domains within ARA67/PAT1 may be required for the maximal interaction with AR. ARA67/PAT1 functions as a repressor with better suppressive effects on AR compared to glucocorticoid receptor and estrogen receptor. Further mechanism dissection reveals that the interrupted AR cytoplasmic-nuclear shuttling may play a major role in ARA67/PAT1 mediated suppression on AR. Together, these results suggest that ARA67/PAT1 may function as a novel repressor that can modulate AR function in prostate cancer.