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 1

Overexpression of AR-V7, but not AR-FL, induces osteoblastic bone metastasis in PCa.

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Overexpression of AR-V7, but not AR-FL, induces osteoblastic bone metast...
(A and B) Immunoblotting for AR-V7 or AR-FL in C4-2–derived lentiviral stable lines overexpressing doxycycline-regulated, V5-tagged AR-V7 (C4-2-tet-ARV7) (A) or AR-FL (C4-2-tet-ARFL) (B). Cells were pretreated with or without 0.25 μg/mL doxycycline for 48 hours. (C and D) C4-2-tet-ARV7 (C) or C4-2-tet-ARFL (D) cells were injected into the tibias of castrated NSG mice, which were then fed with or without a doxycycline-supplemented diet. The bone lesion area was monitored and quantified. (E and F) Normalized bone volume (BV) and trabecular bone number (Tb.N) in C4-2-tet-ARV7 tumors (E) or C4-2-tet-ARFL tumors (F) were compared. TV, total volume. (G) Structural views of bones scanned by μCT and 3D reconstructed for the C4-2-tet-ARV7 model. (H and I) Immunohistochemistry (IHC) staining for SOX9 in tumor samples from the C4-2-tet-ARV7 model (H) and the C4-2-tet-ARFL model (I). Scale bars (H and I): 500 μm (left) and 100 μm (right). (J and K) Immunoblotting for AR (antibody against N-terminus) and SOX9 in C4-2-tet-ARV7 (J) and C4-2-tet-ARFL cells (K), which were treated with 0, 0.1, 0.5, or 1 μg/mL doxycycline for 48 hours. All the cell lines were hormone depleted prior to the experiments. Unpaired, 2-sided Student’s t test was used to determine statistical significance. *P < 0.05, **P < 0.01, ***P < 0.001.