Therapeutic Targeting of the p300/CBP Bromodomain Enhances the Efficacy of Immune Checkpoint Blockade Therapy
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ABSTRACT:
PROVIDER: PRJNA1232709 | ENA |
REPOSITORIES: ENA
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Project description:Blockade of immune checkpoints, such as programmed death-ligand 1 (PD-L1), has shown promise in cancer treatment; however, clinical response remains limited in many cancer types. Our previous research demonstrated that p300/CBP mediates the acetylation of the PD-L1 promoter, regulating PD-L1 expression. In this study, we further investigated the role of the p300/CBP bromodomain in regulating PD-L1 expression using CCS1477, a selective bromodomain inhibitor developed by our team. We found that the p300/CBP bromodomain is essential for H3K27 acetylation at PD-L1 enhancers. Inhibiting this modification significantly reduced enhancer activity and PD-L1 transcription, including exosomal PD-L1, which has been implicated as key contributors to resistance against PD-L1 blockade therapy in various cancers. Furthermore, CCS1477 treatment resulted in a marked reduction of myeloid-derived suppressor cells (MDSCs) in the tumor microenvironment (TME) by inhibiting key cytokines such as IL6, CSF1, and CSF2, which are crucial for MDSC differentiation and recruitment. By reducing PD-L1 expression and modulating the immunosuppressive TME, CCS1477 creates a more favorable environment for tumor-infiltrating lymphocytes, significantly enhancing the efficacy of immune checkpoint blockade (ICB) therapy. Notably, these effects were observed in both prostate cancer and melanoma models, underscoring the broad therapeutic potential of p300/CBP bromodomain inhibition in improving ICB outcomes.
2025-08-27 | GSE291279 | GEO
Project description:The acetyltransferases CBP and p300 are multifunctional transcriptional co-activators; however, their acetylation targets, site-specific acetylation kinetics, and function in proteome regulation are incompletely understood. We combined quantitative proteomics with novel CBP/p300-specific catalytic inhibitors, bromodomain inhibitor, and gene knockout to show that CBP/p300 acetylates thousands of sites, including signature histone sites, as well as a multitude of sites on signaling effectors and enhancer-associated transcriptional regulators. Kinetic analysis identified a subset of CBP/p300-regulated sites with very rapid (<30min) acetylation turnover, revealing a dynamic balance between acetylation and deacetylation. Quantification of acetylation, mRNA, and protein abundance after CBP/p300 inhibition reveals a kinetically competent network of gene expression that strictly depends on CBP/p300-catalyzed rapid acetylation. Collectively, our in-depth acetylome analyses reveal systems attributes of CBP/p300 targets, and the resource dataset provides a framework for investigating CBP/p300 functions, as well as for understanding the impact of small molecule inhibitors targeting its catalytic and bromodomain activities.
2018-06-10 | PXD005252 | Pride
Project description:Histone acetylation is important for the activation of gene transcription but little is known about its direct ‘read/write’ mechanisms. Here, we report cryo-electron microscopy structures in which a p300/CBP multidomain monomer recognizes histone H4 N-terminal tail (NT) acetylation (ac) in a nucleosome and acetylates non-H4 histone NTs within the same nucleosome. p300/CBP not only recognized H4NTac via the bromodomain pocket responsible for ‘reading’, but also interacted with the DNA minor grooves via the outside of that pocket. This directed the catalytic center of p300/CBP to one of the non-H4 histone NTs. The primary target that p300 ‘writes’ by ‘reading’ H4NTac was H2BNT, and H2BNTac promoted H2A-H2B dissociation from the nucleosome. We propose a model in which p300/CBP ‘replicates’ histone NT acetylation within the H3-H4 tetramer to inherit epigenetic storage, and ‘transcribes’ it from the H3-H4 tetramer to the H2B-H2A dimers to activate context-dependent gene transcription through local nucleosome destabilization.
2023-05-08 | PXD040835 | Pride
Project description:Comparison of CBP/p300 gene knock-out, bromodomain inhibitor, and acetyltransferase inhibitors Cmpd-R and A-485 in the same cell line (MEF).
2018-06-13 | GSE92613 | GEO
Project description:The acetyltransferases CBP and p300 are multifunctional transcriptional co-activators; however, their acetylation targets, site-specific acetylation kinetics, and function in proteome regulation are incompletely understood. We combined quantitative proteomics with novel CBP/p300-specific catalytic inhibitors, bromodomain inhibitor, and gene knockout to show that CBP/p300 acetylates thousands of sites, including signature histone sites, as well as a multitude of sites on signaling effectors and enhancer-associated transcriptional regulators. Kinetic analysis identified a subset of CBP/p300-regulated sites with very rapid (<30min) acetylation turnover, revealing a dynamic balance between acetylation and deacetylation. Quantification of acetylation, mRNA, and protein abundance after CBP/p300 inhibition reveals a kinetically competent network of gene expression that strictly depends on CBP/p300-catalyzed rapid acetylation. Collectively, our in-depth acetylome analyses reveal systems attributes of CBP/p300 targets, and the resource dataset provides a framework for investigating CBP/p300 functions, as well as for understanding the impact of small molecule inhibitors targeting its catalytic and bromodomain activities.
| MSV000095981 | MassIVE
Project description:The bromodomain and extraterminal (BET) protein Brd4 is a validated drug target in leukemia, yet its regulatory function in this disease is not well understood. Here, we show that Brd4 chromatin occupancy in acute myeloid leukemia closely correlates with the hematopoietic transcription factors (TFs) Pu.1, Fli1, Erg, C/EBPα, C/EBPβ, and Myb at nucleosome-depleted enhancer and promoter regions. We provide evidence that these TFs, in conjunction with the lysine acetyltransferase activity of p300/CBP, facilitate Brd4 recruitment to their occupied sites to promote transcriptional activation. Moreover, chemical inhibition of BET bromodomains is found to suppress the functional output each hematopoietic TF, thereby interfering with essential lineage-specific transcriptional circuits in this disease. These findings reveal a chromatin-based signaling cascade comprised of hematopoietic TFs, p300/CBP, and Brd4, which supports leukemia maintenance and is suppressed by BET bromodomain inhibition. PolyA selected RNA-Seq for drug treated or shRNA-expressing MLL-AF9 transformed acute myeloid leukemia cells (RN2)
2015-05-01 | E-GEOD-66068 | biostudies-arrayexpress
Project description:The bromodomain and extraterminal (BET) protein Brd4 is a validated drug target in leukemia, yet its regulatory function in this disease is not well understood. Here, we show that Brd4 chromatin occupancy in acute myeloid leukemia closely correlates with the hematopoietic transcription factors (TFs) Pu.1, Fli1, Erg, C/EBPα, C/EBPβ, and Myb at nucleosome-depleted enhancer and promoter regions. We provide evidence that these TFs, in conjunction with the lysine acetyltransferase activity of p300/CBP, facilitate Brd4 recruitment to their occupied sites to promote transcriptional activation. Moreover, chemical inhibition of BET bromodomains is found to suppress the functional output each hematopoietic TF, thereby interfering with essential lineage-specific transcriptional circuits in this disease. These findings reveal a chromatin-based signaling cascade comprised of hematopoietic TFs, p300/CBP, and Brd4, which supports leukemia maintenance and is suppressed by BET bromodomain inhibition. ChIP-Seq for regulatory factors of Brd4 in MLL-AF9 transformed acute myeloid leukemia cells (RN2)
2015-05-01 | E-GEOD-66122 | biostudies-arrayexpress
Project description:p300 and CBP are highly related histone acetyltransferase (HAT) enzymes that regulate gene expression, and their dysregulation has been linked to cancer and other diseases. p300/CBP is composed of a number of domains including a HAT domain which is inhibited by the small molecule A-485 and an acetyl-lysine binding bromodomain which was recently found to be selectively antagonized by the small molecule I-CBP112. Here we show that the combination of I-CBP112 and A-485 can synergize to inhibit prostate cancer cell proliferation. We find that the combination confers a dramatic reduction in p300 chromatin occupancy compared to the individual effects of blocking either domain alone. Accompanying this loss of p300 on chromatin, combination treatment predominantly leads to the reduction of specific mRNAs including androgen-dependent and pro-oncogenic prostate genes such as KLK3 (PSA) and c-Myc. Consistent with p300 chromatin binding directly affecting gene expression, mRNAs that are significantly reduced by combination treatment also exhibit a strong reduction in p300 chromatin occupancy at their gene promoters. The relatively few mRNAs that are up-regulated upon combination treatment show no correlation with p300 occupancy. These studies provide support for the pharmacologic advantage of concurrent targeting of two domains within one key epigenetic modification enzyme.
2019-12-31 | GSE124643 | GEO