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 9

CDK9 inhibition prevents Ser81 phosphorylation of AR-V7 and impairs AR-V7–mediated metastasis.

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CDK9 inhibition prevents Ser81 phosphorylation of AR-V7 and impairs AR-V...
(A) Immunoblotting for p-S81 of AR-V7, V5, and SOX9 in LN-tet-ARV7 cells treated with CDK9 inhibitors for 24 hours. (B) qRT-PCR for AR-V7 target genes in LN-tet-ARV7 cells treated with 2 CDK9 inhibitors for 24 hours. (C and E) Immunoblotting for p-S81 of AR-V7 and SOX9 in C4-2-tet-ARV7 (C) and 35CR (E) cells treated with or without 0.1 μM AZD4573 for 24 hours. (D and G) Zebrafish embryo metastasis assays in GFP-labeled C4-2-tet-ARV7 cells cultured under doxycycline (D) and 35CR cells (G) pretreated with or without 0.1 μM AZD4573 for 24 hours. (F) qRT-PCR for AR-V7 target genes in 35CR cells treated with 0.1 μM AZD4573 for 24 hours. (H) C4-2-tet-ARV7 cells were injected into the tibias of castrated male mice, which were then fed with a doxycycline-supplemented diet and treated with (n = 12) or without AZD4573 (n = 8, 15 mg/kg) via i.p. injection every other day. The bone lesion area was monitored and quantified. (I) IHC staining for SOX9 in tumor samples. Scale bars: 100 μm. All the cell lines were hormone depleted before experiments. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001 by unpaired, 2-sided Student’s t test (bar graphs) or χ2 test (D and G). Data are represented as mean ± SD.