AI Insight
This study identifies cullin-associated NEDD8-dissociated protein 1 (CAND1) as a coactivator of both the androgen receptor (AR) and its splice variant ARv7, which drives castration-resistant prostate cancer by lacking the ligand-binding domain targeted by current therapies. Using a cell-free DNA pulldown assay combined with mass spectrometry, the researchers characterized AR and ARv7 coregulator complexes and showed that CAND1 knockdown reduces AR and ARv7 target gene expression. The study further demonstrates that DNA-dependent protein kinase (DNA-PK) phosphorylates both AR and ARv7, enhances their transcriptional activity, and stabilizes CAND1 interactions within these coregulator complexes, with CAND1 expression correlating with metastatic disease and poorer patient survival in clinical datasets.
Why it matters
These findings identify CAND1 and DNA-PK as potential new therapeutic targets in castration-resistant prostate cancer, a disease that remains largely incurable due to resistance to existing androgen-deprivation therapies. Targeting coregulator interactions or the enzymatic activity of DNA-PK could offer alternative treatment strategies for patients with ARv7-driven disease progression.
by Ross A. Hamilton, Basil Paul, Ping Yi, Kimal Rajapakshe, Anil K. Panigrahi, Sandra L. Grimm, Cristian Coarfa, Anna Malovannaya, Nancy L. Weigel, David M. Lonard, Charles E. Foulds
ARv7, the most prevalent androgen receptor (AR) variant in castration-resistant prostate cancer, lacks the ligand binding domain (LBD), rendering it resistant to LBD-targeted therapies. Identifying new therapeutic targets requires defining the coregulators and associated regulatory enzymes that govern AR and ARv7 transcriptional activity. Here, we have developed a cell-free DNA pulldown assay employing androgen response elements (AREs) to isolate and characterize the AR- and ARv7-associated coregulator complexes formed on DNA. Mass spectrometry analyses of ARE DNA pulldowns revealed previously unrecognized AR and ARv7 associating coregulators, such as cullin-associated NEDD8-dissociated protein 1 (CAND1), in addition to previously known coregulators. ARv7 showed enhanced recruitment of a subset of AR associating coregulators. Knockdown of CAND1 in prostate cancer cells reduced the expression of AR and ARv7 target genes, supporting its role as a coactivator. Bioinformatic analyses of human prostate cancer clinical datasets revealed that CAND1 mRNA level correlated with disease status, with higher expression correlated with metastatic prostate cancer and poorer patient survival. We further show that DNA-dependent protein kinase (DNA-PK) phosphorylates both AR and ARv7, enhances their transcriptional activities, and stabilizes the interaction of CAND1 with AR- and ARv7- coregulator complexes. Collectively, these findings suggest that DNA-PK stimulates the AR and ARv7 activity through its enzymatic function and by stabilizing (or reinforcing) coactivator interactions, including those involving CAND1. In sum, this work advances our understanding of AR isoform actions and identifies additional potential therapeutic targets for castration-resistant prostate cancer.