The miR-96 and RARγ signaling axis governs androgen signaling and prostate cancer progression

Abstract

Expression levels of retinoic acid receptor gamma (NR1B3/RARG, encodes RARγ) are commonly reduced in prostate cancer (PCa). Therefore, we sought to establish the cellular and gene regulatory consequences of reduced RARγ expression, and determine RARγ regulatory mechanisms. RARG shRNA approaches in non-malignant (RWPE-1 and HPr1-AR) and malignant (LNCaP) prostate models revealed that reducing RARγ levels, rather than adding exogenous retinoid ligand, had the greatest impact on prostate cell viability and gene expression. ChIP-Seq defined the RARγ cistrome, which was significantly enriched at active enhancers associated with AR binding sites. Reflecting a significant genomic role for RARγ to regulate androgen signaling, RARγ knockdown in HPr1-AR cells significantly regulated the magnitude of the AR transcriptome. RARγ downregulation was explained by increased miR-96 in PCa cell and mouse models, and TCGA PCa cohorts. Biochemical approaches confirmed that miR-96 directly regulated RARγ expression and function. Capture of the miR-96 targetome by biotin-miR-96 identified that RARγ and a number of RARγ interacting co-factors including TACC1 were all targeted by miR-96, and expression of these genes were prominently altered, positively and negatively, in the TCGA-PRAD cohort. Differential gene expression analyses between tumors in the TCGA-PRAD cohort with lower quartile expression levels of RARG and TACC1 and upper quartile miR-96, compared to the reverse, identified a gene network including several RARγ target genes (e.g., SOX15) that significantly associated with worse disease-free survival (hazard ratio 2.23, 95% CI 1.58 to 2.88, p = 0.015). In summary, miR-96 targets a RARγ network to govern AR signaling, PCa progression and disease outcome.

Retinoic acid receptor γ is a therapeutically targetable driver of growth and survival in prostate cancer

“…The poorly invasive, androgen‐dependent LNCaP cell line expresses RARA and RARG mRNA, and RARα and RARγ, but not RARβ protein 34,35 . There are conflicting data regarding expression of RARB mRNA in LNCaP cells 34‐37 . DU145 and PC3 cells exhibit androgen‐independent growth and express RARA and RARG , but RARG mRNA, and also RARα and RARγ, but not RARβ 34,35 .…”

“…DU145 and PC3 cells exhibit androgen‐independent growth and express RARA and RARG , but RARG mRNA, and also RARα and RARγ, but not RARβ 34,35 . Human prostate epithelial non‐neoplastic RWPE‐1 cells 38 express RARα and RARγ, but not RARβ 37 . Cell cultures were maintained under serum‐free conditions using the Prostate Epithelial Cell Growth Medium (PrEGM) BulletKit (Cat.…”

Identification of transcription factor co-regulators that drive prostate cancer progression

“…These findings were further supported when considering target genes that were bound by PGC1α and differentially expressed in the TCGA cohort. These genes distinguished aggressive tumors and included RARγ/TACC1 24 , which we have previously established to antagonize AR signaling, as well as genes associated PPARγ signaling. Furthermore, motif analyses revealed that basic helix-loop-helix (b-HLH) motifs were enriched in the PGC1α ChromHMM sites, as were sites for LXR binding.…”

“…This re-wiring of AR signaling is mirrored by disrupted functions of other members of the nuclear hormone receptor super-family 11 , 24 , and probably occurs more widely to alter how transcription factors (TFs) function. Re-wiring of TFs changes the consequences of cell signaling and contributes to changes in lineage plasticity that are also associated with aggressive PCa 25 – 27 .…”

The effect of Jiedu Huoxue decoction on rat model of experimental nonbacterial prostatitis via regulation of miRNAs

“…miR-96 governs androgen signalling and prostate cancer progression by regulating RARγ signal axis (Long et al. 2019 ). miR-205 can enhance radiation sensitivity of prostate cancer cells by impairing DNA damage repair through PKCε and ZEB1 inhibition (El Bezawy et al.…”