Development of a multiplex assay to assess activated p300/CBP in circulating prostate tumor cells

• Published in: Oncotarget Vol. 14; no. 1; pp. 738 - 746
• Main Authors: Filon, Mikolaj, Yang, Bing, Purohit, Tanaya A., Schehr, Jennifer, Singh, Anupama, Bigarella, Marcelo, Lewis, Peter, Denu, John, Lang, Joshua, Jarrard, David F.
• Format: Journal Article
• Language: English
• Published: United States Impact Journals LLC 20.07.2023
• Subjects: Acetylation; Histones - metabolism; Humans; Male; Neoplastic Cells, Circulating; p300-CBP Transcription Factors - metabolism; Prostatic Neoplasms, Castration-Resistant; Research Paper; Sirtuin 2; circulating tumor cells; p300/CBP; prostate cancer
• DOI: 10.18632/oncotarget.28477
• ISSN: 1949-2553

Reduced SIRT2 deacetylation and increased p300 acetylation activity leads to a concerted mechanism of hyperacetylation at specific histone lysine sites (H3K9, H3K14, and H3K18) in castration-resistant prostate cancer (CRPC). We examined whether circulating tumor cells (CTCs) identify patients with altered p300/CBP acetylation. CTCs were isolated from 13 advanced PC patients using Exclusion-based Sample Preparation (ESP) technology. Bound cells underwent immunofluorescent staining for histone modifying enzymes (HMEs) of interest and image capture with NIS-Elements software. Using the cBioPortal PCF/SU2C dataset, the response of CRPC to androgen receptor signaling inhibitors (ARSI) was analyzed in 50 subjects. Staining optimization and specificity revealed clear expression of acetyl-p300, acetyl-H3K18, and SIRT2 on CTCs (CK positive, CD45 negative cells). Exposure to A-485, a selective p300/CBP catalytic inhibitor, reduced p300 and H3K18 acetylation. In CRPC patients, a-p300 strongly correlated with its target acetylated H3k18 (Pearson's R = 0.61), and SIRT2 expression showed robust negative correlation with a-H3k18 (R = -0.60). A subgroup of CRPC patients (6/11; 55%) demonstrated consistent upregulation of acetylation based on these markers. To examine the clinical impact of upregulation of the CBP/p300 axis, CRPC patients with reduced deacetylase SIRT2 expression demonstrate shorter response times to ARSI therapy (5.9 vs. 12 mo; = 0.03). A subset of CRPC patients demonstrate increased p300/CBP activity based on a novel CTC biomarker assay. With further development, this biomarker suite may be used to identify candidates for CBP/p300 acetylation inhibitors in clinical development.