Pathway-based expression profiling of benign prostatic hyperplasia and prostate cancer delineates an immunophilin molecule associated with cancer progression

Aberrant restoration of AR activity is linked with prostate tumor growth, therapeutic failures and development of castrate-resistant prostate cancer. Understanding the processes leading to AR-reactivation should provide the foundation for novel avenues of drug discovery. A differential gene expression study was conducted using biopsies from CaP and BPH patients to identify the components putatively responsible for reinstating AR activity in CaP. From the set of genes upregulated in CaP, FKBP52, an AR co-chaperone, was selected for further analysis. Expression of FKBP52 was positively correlated with that of c-Myc. The functional cross-talk between c-Myc and FKBP52 was established using c-Myc specific-siRNA to LNCaP cells that resulted in reduction of FKBP52. A non-canonical E-box sequence housing a putative c-Myc binding site was detected on the FKBP4 promoter using in silico search. LNCaP cells transfected with the FKBP52 promoter cloned in pGL3 basic showed increased luciferase activity which declined considerably when the promoter-construct was co-transfected with c-Myc specific-siRNA. ChIP-PCR confirmed the binding of c-Myc with the conserved E-box located in the FKBP52 promoter. c-Myc downregulation concomitantly affected expression of FGF8. Since expression of FGF8 is controlled by AR, our study unveiled a novel functional axis between c-Myc, AR and FGF8 operating through FKBP52.