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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Research Article Oncology

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 8

Ser81 phosphorylation selectively enhances the AR-V7–regulated metastasis program.

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Ser81 phosphorylation selectively enhances the AR-V7–regulated metastasi...
(A) Immunoblotting for S81-phosphorylated (p-S81) AR-FL and AR-V7 in LN-tet-ARV7 and LN-tet-ARV7S81A cells (LNCaP cells expressing doxycycline-regulated V5-tagged AR-V7-S81A mutant). (B and C) RNA-seq analyses were conducted in these stable lines treated with or without 0.25 μg/mL doxycycline. GSEA using Hallmark gene sets (B) or predefined bone metastasis gene sets (C) was performed. (D) Relative fold change for AR-V7 regulation of indicated gene sets. (E) qRT-PCR for AR-V7–activated EMT/metastasis genes and lipid synthesis genes. (F) Immunoblotting for SOX9 and AR in LN-tet-ARFL, LN-tet-ARFLS81A, LN-tet-ARV7, and LN-tet-ARV7S81A cells, treated with 10 nM DHT or 0.25 μg/mL doxycycline. (G–I) ChIP-seq analysis of V5 was performed in LN-tet-ARV7S81A cells stimulated with or without 0.25 μg/mL doxycycline. The Venn diagram for AR-V7-WT bindings sites versus AR-V7-S81A binding sites (G), heatmap view for peak intensity at AR-V7-WT and AR-V7-S81A unique or common sites (H), and heatmap view for peak intensity at AR-V7 and AR-FL unique or common sites (I) are shown. All the cell lines were hormone depleted before experiments. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001 by Wilcoxon’s test (D) or unpaired, 2-sided Student’s t test (E). Data are represented as mean ± SD.