Abstract A9: Androgen-regulated miR-32 targets BTG2 and is overexpressed in castration-resistant prostate cancer

Abstract

Abstract The androgen receptor (AR) signaling pathway is central to the emergence of castration-resistant prostate cancer (CRPC). We set out to identify androgen-regulated microRNAs (miRNAs) that may contribute to the development of CRPC. We found miR-32 to be an androgen regulated miRNA which is differentially expressed in CRPC compared to benign prostate hyperplasia (BPH) according to microarray analyses. qRT-PCR analyses confirmed that miR-32 expression increases in CRPC compared to BPH, and that in untreated prostate cancer (PC) miR-32 expression is higher in tumors of stage pT3 compared to pT2. Transfection of pre-miR-32 to prostate cancer cell line LNCaP provided a significant growth advantage to the cells, and miR-32 was further demonstrated to reduce apoptosis. To identify target genes for miR-32, an mRNA microarray analysis was performed with LNCaP cells transfected with pre-miR-32. In this assay, B cell translocation gene 2 (BTG2) was identified as a novel putative target for miR-32. BTG2 was reduced both at mRNA and protein level in the cells transfected with pre-miR-32, and BTG2 was confirmed to be a miR-32 target by 3′-UTR-luciferase assay. Furthermore, BTG2 was able to partially rescue the growth advantage of miR-32 in LNCaP cells. Immunostainings of prostate cancer patient material showed a statistically significant (p < 0.0001) reduction of BTG2 protein in CRPCs compared to PC. The lack of BTG2 staining was also associated (p=0.0021) with a short progression-free time in patients who underwent prostatectomy and inversely correlated to miR-32 expression levels. In conclusion, we find that miR-32 is an androgen-regulated miRNA targeting BTG2 and overexpressed in CRPC. Thus, miR-32 is a potential marker for aggressive disease and is a putative drug target in PC. Citation Format: Sanni E. Jalava, Leena Latonen, Mauro Scaravilli, Kati K. Waltering, Janne Seppälä, Harri Lähdesmäki, Teuvo L.J. Tammela, Tapio Visakorpi. Androgen-regulated miR-32 targets BTG2 and is overexpressed in castrationresistant prostate cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr A9.