title: Androgen-regulated miR-32 targets BTG2 and is overexpressed in castration-resistant prostate cancer.
abstract: The androgen receptor (AR) signaling pathway is involved in the emergence of castration-resistant prostate cancer (CRPC). Here, we identified several androgen-regulated microRNAs (miRNAs) that may contribute to the development of CRPC. Seven miRNAs, miR-21, miR-32, miR-99a, miR-99b, miR-148a, miR-221 and miR-590-5p, were found to be differentially expressed in CRPC compared with benign prostate hyperplasia (BPH) according to microarray analyses. Significant growth advantage for LNCaP cells transfected with pre-miR-32 and pre-miR-148a was found. miR-32 was demonstrated to reduce apoptosis, whereas miR-148a enhanced proliferation. Androgen regulation of miR-32 and miR-148a was confirmed by androgen stimulation of the LNCaP cells followed by expression analyses. The AR-binding sites in proximity of these miRNAs were demonstrated with chromatin immunoprecipitation (ChIP). To identify target genes for the miRNAs, mRNA microarray analyses were performed with LNCaP cells transfected with pre-miR-32 and pre-miR-148a. Expression of BTG2 and PIK3IP1 was reduced in the cells transfected with pre-miR-32 and pre-miR-148a, respectively. Also, the protein expression was reduced according to western blot analysis. BTG2 and PIK3IP1 were confirmed to be targets by 3'UTR-luciferase assays. Finally, immunostainings showed a statistically significant (P<0.0001) reduction of BTG2 protein in CRPCs compared with untreated prostate cancer (PC). The lack of BTG2 staining was also associated (P<0.01) with a short progression-free time in patients who underwent prostatectomy. In conclusion, androgen-regulated miR-32 is overexpressed in CRPC, leading to reduced expression of BTG2. Thus, miR-32 is a potential marker for aggressive disease and is a putative drug target in PC.
authors.affiliation: Institute of Biomedical Technology, Tampere University, Tampere, Finland.
authors.forename: S E
authors.initials: SE
authors.lastname: Jalava
authors.forename: A
authors.initials: A
authors.lastname: Urbanucci
authors.forename: L
authors.initials: L
authors.lastname: Latonen
authors.forename: K K
authors.initials: KK
authors.lastname: Waltering
authors.forename: B
authors.initials: B
authors.lastname: Sahu
authors.forename: O A
authors.initials: OA
authors.lastname: Jänne
authors.forename: J
authors.initials: J
authors.lastname: Seppälä
authors.forename: H
authors.initials: H
authors.lastname: Lähdesmäki
authors.forename: T L J
authors.initials: TL
authors.lastname: Tammela
authors.forename: T
authors.initials: T
authors.lastname: Visakorpi
mesh_terms: D000728:Androgens / Q000502:physiology; D001665:Binding Sites; D016022:Case-Control Studies; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics* / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009376:Neoplasms, Hormone-Dependent / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism*; D011944:Receptors, Androgen / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D015398:Signal Transduction; D059467:Transcriptome; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D000728:Androgens; D017874:Immediate-Early Proteins; D047908:Intracellular Signaling Peptides and Proteins; C550570:MIRN148 microRNA, human; C568529:MIRN32 microRNA, human; D008565:Membrane Proteins; D035683:MicroRNAs; C521076:PIK3IP1 protein, human; D011944:Receptors, Androgen; D025521:Tumor Suppressor Proteins; C070114:BTG2 protein, human