Androgen receptor splice variants drive castration-resistant prostate cancer metastasis by activating distinct transcriptional programs
Dong Han, … , Xiaohong Li, Changmeng Cai
Dong Han, … , Xiaohong Li, Changmeng Cai
Published April 30, 2024
Citation Information: J Clin Invest. 2024;134(11):e168649. https://doi.org/10.1172/JCI168649.
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Androgen receptor splice variants drive castration-resistant prostate cancer metastasis by activating distinct transcriptional programs

Abstract

One critical mechanism through which prostate cancer (PCa) adapts to treatments targeting androgen receptor (AR) signaling is the emergence of ligand-binding domain–truncated and constitutively active AR splice variants, particularly AR-V7. While AR-V7 has been intensively studied, its ability to activate distinct biological functions compared with the full-length AR (AR-FL), and its role in regulating the metastatic progression of castration-resistant PCa (CRPC), remain unclear. Our study found that, under castrated conditions, AR-V7 strongly induced osteoblastic bone lesions, a response not observed with AR-FL overexpression. Through combined ChIP-seq, ATAC-seq, and RNA-seq analyses, we demonstrated that AR-V7 uniquely accesses the androgen-responsive elements in compact chromatin regions, activating a distinct transcription program. This program was highly enriched for genes involved in epithelial-mesenchymal transition and metastasis. Notably, we discovered that SOX9, a critical metastasis driver gene, was a direct target and downstream effector of AR-V7. Its protein expression was dramatically upregulated in AR-V7–induced bone lesions. Moreover, we found that Ser81 phosphorylation enhanced AR-V7’s pro-metastasis function by selectively altering its specific transcription program. Blocking this phosphorylation with CDK9 inhibitors impaired the AR-V7–mediated metastasis program. Overall, our study has provided molecular insights into the role of AR splice variants in driving the metastatic progression of CRPC.

Authors

Dong Han, Maryam Labaf, Yawei Zhao, Jude Owiredu, Songqi Zhang, Krishna Patel, Kavita Venkataramani, Jocelyn S. Steinfeld, Wanting Han, Muqing Li, Mingyu Liu, Zifeng Wang, Anna Besschetnova, Susan Patalano, Michaela J. Mulhearn, Jill A. Macoska, Xin Yuan, Steven P. Balk, Peter S. Nelson, Stephen R. Plymate, Shuai Gao, Kellee R. Siegfried, Ruihua Liu, Mary M. Stangis, Gabrielle Foxa, Piotr J. Czernik, Bart O. Williams, Kourosh Zarringhalam, Xiaohong Li, Changmeng Cai

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Figure 2

AR-V7 activates a unique transcription program in CRPC.

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AR-V7 activates a unique transcription program in CRPC. (A) Immunoblotti...
(A) Immunoblotting for AR (N-terminus) in LNCaP cells stably expressing doxycycline-regulated V5-tagged AR-FL (LN-tet-ARFL) or AR-V7 (LN-tet-ARV7) treated with 0–1 μg/mL doxycycline for 48 hours. (B) Immunoblotting for AR in LN-tet-ARV7 cells treated with or without low-dose doxycycline (0.1 μg/mL for 48 hours) or DHT (10 nM for 24 hours). (C) Immunoblotting for indicated proteins in LNCaP cells stably expressing cumate-regulated FLAG-tagged ARv567es (LN-cu-ARv567es) with the treatment of 0, 30, or 60 μg/mL cumate for 48 hours. (D and E) Immunoblotting for AR-V7 and N-terminal AR in CWR-22Rv1 (D) and LuCaP 35CR cells (E) transfected with siRNAs against nontarget control (NTC) or AR-V7 for 3 days. (F) RNA-seq analyses were conducted to compare the AR-V7 transcriptome (22Rv1 and 35CR transfected with siNTC or siARV7 for 3 days, LN-tet-ARV7 treated with or without 0.25 μg/mL doxycycline for 48 hours) with the ARv567es transcriptome (LN-cu-ARv567es treated with or without 30 μg/mL cumate for 48 hours) and DHT-stimulated AR-FL transcriptome (LNCaP/C4-2/VCaP stimulated with or without 10 nM DHT for 24 hours, LN-tet-ARFL treated with 0.25 μg/mL doxycycline and stimulated with or without 0.1 nM DHT for 24 hours). GSEA normalized enrichment scores (NES) of MSigDB Hallmark gene sets in each model were plotted (red, AR-V7– or AR-FL–activated pathways; blue, AR-V7– or AR-FL–repressed pathways). All the cell lines were hormone depleted prior to the experiments. (G and H) The expression of AR-V7–specific targets (17-gene signature) in these cell lines (G) and in human PCa cohorts: Normal (n = 52) and androgen-dependent primary PCa samples (n = 498) from TCGA data set versus metastatic CRPC samples from SU2C (n = 266) and UW data sets (n = 138) (H). P values are shown above the horizontal bars. (I) Kaplan-Meier survival analysis for the overall survival from the initiation of the first-line ARSi in mCRPC patients (SU2C cohort, n = 99) was conducted, comparing top 25th percentile of median score expression (red, n = 25) versus lower 75th percentile (blue, n = 74). P value was calculated using the log-rank test from the score test. Statistical analyses were conducted using unpaired, nonparametric 2-sample Wilcoxon’s test for box-and-whisker plots, with Bonferroni’s correction for multiple comparisons.