BRCA1, BRCA2, AR and IGF-I expression in prostate cancer: Correlation between RT-qPCR and immunohistochemical detection

Identification and characterization of biomarkers in prostate cancer are important for improving the diagnosis. The aim of this study was to determine differences in the expression of 4 genes according to the stage of malignancy in prostate cancer. We analyzed BRCA1, BRCA2, androgen receptor (AR) and IGF-I gene expression in a cohort of 98 prostate biopsies. We used TaqMan RT-qPCR for mRNA detection, and correlation with proteins was performed using immunohistochemistry. Among the 98 studied prostate biopsies, high heterogeneity in the expression of the 4 genes was detected among the different histological types. However, down-regulation of BRCA1 and BRCA2 mRNA was detected, particularly in the normal tissues. The expression of AR was dependent on the stage of the tumor. The IGF-I gene was specifically expressed in the tumor tissues. Upon comparison between protein and mRNA expression for BRCA1, BRCA2 and AR, we obtained a trend; however, this did not achieve statistical significance. Regarding IGF-I, a correlation between mRNA expression and staining intensity of the protein was found to be significant (p<0.012). The AR biomarker was found to be slightly correlated with the prostate cancer diagnosis (p=0.013). AR was found to be decreased in the tumors with a 43% sensitivity and 90% specificity. The relative risk of 2.05 (1.13-3.69) indicated a 2-fold higher chance of cancer occurence when AR was <= 0.206.