BCL2 expression is enriched in advanced prostate cancer with features of lineage plasticity
Daniel Westaby, et al.
Daniel Westaby, et al.
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Research Article Oncology

BCL2 expression is enriched in advanced prostate cancer with features of lineage plasticity

Abstract

The widespread use of potent androgen receptor signaling inhibitors (ARSIs) has led to an increasing emergence of AR-independent castration-resistant prostate cancer (CRPC), typically driven by loss of AR expression, lineage plasticity, and transformation to prostate cancers (PCs) that exhibit phenotypes of neuroendocrine or basal-like cells. The anti-apoptotic protein BCL2 is upregulated in neuroendocrine cancers and may be a therapeutic target for this aggressive PC disease subset. There is an unmet clinical need, therefore, to clinically characterize BCL2 expression in metastatic CRPC (mCRPC), determine its association with AR expression, uncover its mechanisms of regulation, and evaluate BCL2 as a therapeutic target and/or biomarker with clinical utility. Here, using multiple PC biopsy cohorts and models, we demonstrate that BCL2 expression is enriched in AR-negative mCRPC, associating with shorter overall survival and resistance to ARSIs. Moreover, high BCL2 expression associates with lineage plasticity features and neuroendocrine marker positivity. We provide evidence that BCL2 expression is regulated by DNA methylation, associated with epithelial-mesenchymal transition, and increased by the neuronal transcription factor ASCL1. Finally, BCL2 inhibition had antitumor activity in some, but not all, BCL2-positive PC models, highlighting the need for combination strategies to enhance tumor cell apoptosis and enrich response.

Authors

Daniel Westaby, Juan M. Jiménez-Vacas, Ines Figueiredo, Jan Rekowski, Claire Pettinger, Bora Gurel, Arian Lundberg, Denisa Bogdan, Lorenzo Buroni, Antje Neeb, Ana Padilha, Joe Taylor, Wanting Zeng, Souvik Das, Emily Hobern, Ruth Riisnaes, Mateus Crespo, Susana Miranda, Ana Ferreira, Brian P. Hanratty, Daniel Nava Rodrigues, Claudia Bertan, George Seed, Maria de Los Dolores Fenor de La Maza, Christina Guo, Juliet Carmichael, Rafael Grochot, Khobe Chandran, Anastasia Stavridi, Andreas Varkaris, Nataly Stylianou, Brett G. Hollier, Nina Tunariu, Steven P. Balk, Suzanne Carreira, Wei Yuan, Peter S. Nelson, Eva Corey, Michael Haffner, Johann de Bono, Adam Sharp

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Figure 9

Targeting BCL2 in BCL2-positive PC.

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Targeting BCL2 in BCL2-positive PC. (A) Dose-response curves for PC cell...
(A) Dose-response curves for PC cell lines treated with venetoclax. Cell viability was compared with vehicle (DMSO) in each cell line and evaluated at 72 hours using the CellTiter-Glo assay (Promega). (B) Caspase-3/7 activity (Caspase Glo-3/7 assay) was measured at 6 hours after treatment with venetoclax (1 μM) and compared with vehicle (DMSO). Experiments were performed in 3 biological replicates, each with 3 technical replicates. SEM is shown. The impact of venetoclax was compared against vehicle (DMSO) for each cell line by unpaired, 2-tailed t test. (C) IHC for cytoplasmic BCL2 and nuclear AR-NTD was performed on LuCaP 70CR and 136CR PDXs. Scale bar: 50 μm. LuCaP 70CR (PDX-O) and 136CR (primary cell culture) were treated with venetoclax (125, 250, and 500 nM and 1 μM) for 96 hours. Viability was determined by CellTiter-Glo 3D assay. Dunnett’s multiple-comparison test was used to determine statistical significance of each concentration versus the vehicle. (D) Transcriptome analyses associating BCL2 mRNA expression (<90th percentile vs. ≥90th percentile) with MCL1, BCLXL, and AR mRNA expression (ICR/RMH CRPC RNA sequencing cohort, n = 95). Medians and IQRs are shown. Mann-Whitney U test was used to determine statistical significance. (E and F) CP336c PDX-organoids (PDX-O) were treated with vehicle (DMSO), venetoclax (1 μM), A-1331852 (100 nM), navitoclax (1 μM), AZD5991 (1 μM), and a combination of AZD5991 (1 μM) and navitoclax (1 μM). (E) The impact on caspase-3/7 activity (6 hours) and organoid viability (24 and 96 hours) was determined by Caspase Glo-3/7 3D and CellTiter-Glo 3D assays, respectively. The experiment was performed in biological triplicate with 5 technical replicates. SEM is shown. Dunnett’s multiple-comparison test was used to determine statistical significance of each drug versus the vehicle. (F) Representative microscopy images of CP336c PDX-O on day 4 after treatment. Scale bar: 50 μm.