RBBP4-p300 axis modulates expression of genes essential for cell survival and is a potential target for therapy in glioblastoma. Issue 8 (1st March 2022)

• Record Type: Journal Article
• Authors: Mladek, Ann C; Yan, Huihuang; Tian, Shulan; Decker, Paul A; Burgenske, Danielle M; Bakken, Katrina; Hu, Zeng; He, Lihong; Connors, Margaret A; Carlson, Brett L; Wilson, Jonathan; Bommi-Reddy, Archana; Conery, Andy; Eckel-Passow, Jeanette E; Sarkaria, Jann N; Kitange, Gaspar J
• Is Part Of: Neuro-oncology. Volume 24:Issue 8(2022)
• Page Start: 1261
• Page End: 1272
• Publication Date: 2022-03-01
• Subjects: glioblastoma -- histone acetylation -- RBB4/p300 complex -- temozolomide; Brain Neoplasms -- Periodicals; Brain -- Tumors -- Periodicals; Brain -- Cancer -- Periodicals; Nervous system -- Cancer -- Periodicals; 616.99481
• DOI: 10.1093/neuonc/noac051
• Languages: English
• ISSNs: 1522-8517

Abstract

Abstract: Background: RBBP4 activates transcription by histone acetylation, but the partner histone acetyltransferases are unknown. Thus, we investigated the hypothesis that RBBP4 interacts with p300 in a complex in glioblastoma (GBM). Methods: shRNA silencing of RBBP4 or p300 and RNAseq was used to identify genes co-regulated by RBBP4 and p300 in GBM43 patient-derived xenograft (PDX). RBBP4/p300 complex was demonstrated using proximity ligation assay (PLA) and ChIPseq delineated histone H3 acetylation and RBBP4/p300 complex binding in promoters/enhancers. Temozolomide (TMZ)-induced DNA double strand breaks (DSBs) were evaluated by γ-H2AX and proliferation by CyQuant and live cell monitoring assays. In vivo efficacy was based on survival of mice with orthotopic tumors. Results: shRBBP4 and shp300 downregulated 4768 genes among which 1485 (31%) were commonly downregulated by both shRNAs, while upregulated genes were 2484, including 863 (35%) common genes. The pro-survival genes were the top-ranked among the downregulated genes, including C-MYC . RBBP4/p300 complex was demonstrated in the nucleus, and shRBBP4 or shp300 significantly sensitized GBM cells to TMZ compared to the control shNT in vitro ( P < .05). Moreover, TMZ significantly prolonged the survival of mice bearing GBM22-shRBBP4 orthotopic tumors compared with control shNT tumors (median shNT survival 52 days vs. median shRBBP4 319 days; P = .001). CREB-binding protein (CBP)/p300 inhibitor CPI-1612 suppressed H3K27Ac and RBBP4/p300 complex target proteins, including C-MYC, and synergistically sensitized TMZ in vitro. Pharmacodynamic evaluation confirmed brain penetration by CPI-1612 supporting further investigation to evaluate efficacy to sensitize TMZ. Conclusions: RBBP4/p300 complex is present in GBM cells and is a potential therapeutic target.