PSA secretion and cell proliferation are affected by NCoR1 silencing in prostate cancer cells

Introduction: The androgen receptor (AR) plays an important role in normal development of the prostate gland, as well as in prostatic neoplasms. Transcriptional regulation by AR is modulated by its interaction with co-activators or co-repressors, such as NCoR1 (nuclear receptor co-repressor 1), which is involved in reducing AR activity over the target gene transcription. Methods: To identify the role of NCoR1 in the prostate cancer androgen independence in a cell line model, we aimed to evaluate the effects of silencing NCoR1 on prostate-specific antigen (PSA) gene expression, the proliferative response and PSA secretion on the supernatant of C4-2B and LNCaP cells that were submitted to small interfering RNAs (siRNAs) transfection, and to treatments with different androgen dosages. Results: In LNCaP and C4-2B cells with no dihydrotestosterone (DHT) treatment, a decrease in PSA mRNA expression was observed 48 hours and 72 hours after gene silencing in the siNCoR group when compared to the control and siNC groups. The LNCaP and C4-2B cells showed a biphasic pattern in response to dihydrotestosterone treatment in transfected groups (siNCoR and siNC) as well as in the control condition (without transfection). The secretion of PSA in cell supernatant of LNCaP and C4-2B cells was higher in the siNCoR group, and, in relation to hormonal treatment, higher in the 10-8 M DHT group. Conclusions: A reduction in the NCoR1 levels seems to have a double influence on the activity of AR in PCa cells. These results suggest that NCoR may act as an AR co-repressor depending upon hormonal stimulation.(AU)

Androgen receptor CAG polymorphism and the risk of benign prostatic hyperplasia in a Brazilian population

Benign prostatic hyperplasia (BPH) is a very frequent age-related proliferative abnormality in men. Polymorphic CAG repeat in the androgen receptor (AR) can alter transactivation of androgen-responsive genes and potentially influence BPH risk. We investigated the association between CAG repeat length and risk of BPH in a case-control study of a Brazilian population. We evaluated 214 patients; 126 with BPH and 88 healthy controls. DNA was extracted from peripheral leucocytes and the AR gene was analyzed using fragment analysis. Hazard ratio (HR) and 95% confidence interval were estimated using logistic regression models. Mean CAG length was not different between patients with BPH and controls. The CAG repeat length was examined as a categorical variable (CAG < 21 vs. CAG > 21 and CAG < 22 vs. CAG > 22) and did not differ between the control vs. the BPH group. We found no evidence for an association between AR CAG repeat length in BPH risk in a population-based sample of Brazilians.