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.
|Original language||English (US)|
|Number of pages||12|
|State||Published - Aug 1 2022|
Bibliographical notePublisher Copyright:
© 2022 The Author(s). Published by Oxford University Press on behalf of the Society for Neuro-Oncology. All rights reserved.
- histone acetylation
- RBB4/p300 complex
- Retinoblastoma-Binding Protein 4/genetics
- Promoter Regions, Genetic
- E1A-Associated p300 Protein/genetics
- Cell Survival
- Drug Resistance, Neoplasm
- Xenograft Model Antitumor Assays
- Glioblastoma/drug therapy
- Cell Line, Tumor
- Brain Neoplasms/drug therapy
PubMed: MeSH publication types
- Research Support, Non-U.S. Gov't
- Journal Article
- Research Support, N.I.H., Extramural