CREB5 promotes resistance to androgen-receptor antagonists and androgen deprivation in prostate cancer

Inhibition of androgen-receptor (AR)signaling is the foundation of therapeutic regimens for advanced prostate cancers. However, nearly all patientsdevelop resistance and some never respond. To identify genes that mediate resistance to androgen ablation therapy, we performed an open reading frame (ORF) expression screen of17,255 ORFs and found that the transcription factorCREB5robustly conferred resistance to androgen deprivation and AR inhibition by enzalutamide. CREB5 overexpressionincreased enzalutamide-resistance 45-fold, enhanced resistance of tumor xenografts. CREB5 expression was also essential for enzalutamide-resistance patient-derived organoids. In clinical mCRPC, CREB5is frequently amplified and itsoverexpression positively correlated with castration resistance gene signatures including those of MYC and cell cycle. Mechanistically, CREB5 directly interacted at AR binding sites andenhanced site-specific AR bindingin enzalutamide. This dysregulated expression of 393 AR target genes including MYC and CDK1.These observations identifyCREB5asadriver of enzalutamide-resistance in a subset of advancedprostate cancer. Overall design: To perform ChIpseq (H3K27Ac, AR, FoxA1 or CREB5 antibody), ATAC seq or RNAseq in LNCaP cells expressing either luciferase or CREB5 after treatment either enzalutamide or DMSO control.