Loss of MHC class I (MHC-I) antigen presentation in cancer cells can elicit immunotherapy resistance. A genome-wide CRISPR/Cas9 screen identified an evolutionarily conserved function of polycomb ...repressive complex 2 (PRC2) that mediates coordinated transcriptional silencing of the MHC-I antigen processing pathway (MHC-I APP), promoting evasion of T cell-mediated immunity. MHC-I APP gene promoters in MHC-I low cancers harbor bivalent activating H3K4me3 and repressive H3K27me3 histone modifications, silencing basal MHC-I expression and restricting cytokine-induced upregulation. Bivalent chromatin at MHC-I APP genes is a normal developmental process active in embryonic stem cells and maintained during neural progenitor differentiation. This physiological MHC-I silencing highlights a conserved mechanism by which cancers arising from these primitive tissues exploit PRC2 activity to enable immune evasion.
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•PRC2 maintains bivalency at MHC-I antigen-processing genes silencing MHC-I expression•Cancer cells co-opt this conserved, lineage-specific PRC2 function to evade T cells•Pharmacological inhibition of PRC2 in MHC-I low cancers restores anti-tumor immunity•Immunotherapy resistance may arise via non-genomic routes that exploit PRC2 activity
Burr et al. show that cancer cells co-opt PRC2 to evade immune surveillance. PRC2 maintains bivalency at the promoters of MHC-I antigen-processing pathway (MHC-I APP) genes to repress their basal and cytokine-activated expression. Inhibition of PRC2 restores the MHC-I APP and T cell-mediated anti-tumor immunity.
The success of new therapies hinges on our ability to understand their molecular and cellular mechanisms of action. We modified BET bromodomain inhibitors, an epigenetic-based therapy, to create ...functionally conserved compounds that are amenable to click chemistry and can be used as molecular probes in vitro and in vivo. We used click proteomics and click sequencing to explore the gene regulatory function of BRD4 (bromodomain containing protein 4) and the transcriptional changes induced by BET inhibitors. In our studies of mouse models of acute leukemia, we used high-resolution microscopy and flow cytometry to highlight the heterogeneity of drug activity within tumor cells located in different tissue compartments. We also demonstrate the differential distribution and effects of BET inhibitors in normal and malignant cells in vivo. This study provides a potential framework for the preclinical assessment of a wide range of drugs.
Acetylation of histone lysine residues is one of the most well-studied post-translational modifications of chromatin, selectively recognized by bromodomain “reader” modules. Inhibitors of the ...bromodomain and extra terminal domain (BET) family of bromodomains have shown profound anticancer and anti-inflammatory properties, generating much interest in targeting other bromodomain-containing proteins for disease treatment. Herein, we report the discovery of I-BRD9, the first selective cellular chemical probe for bromodomain-containing protein 9 (BRD9). I-BRD9 was identified through structure-based design, leading to greater than 700-fold selectivity over the BET family and 200-fold over the highly homologous bromodomain-containing protein 7 (BRD7). I-BRD9 was used to identify genes regulated by BRD9 in Kasumi-1 cells involved in oncology and immune response pathways and to the best of our knowledge, represents the first selective tool compound available to elucidate the cellular phenotype of BRD9 bromodomain inhibition.
Background Multiple scoring systems have been devised to quantify angiographic coronary artery disease (CAD) burden, but it is unclear how these scores relate to each other and which scores are most ...accurate. The aim of this study was to compare coronary angiographic scoring systems (1) with each other and (2) with intravascular ultrasound (IVUS)–derived plaque burden in a population undergoing angiographic evaluation for CAD. Methods Coronary angiographic data from 3600 patients were scored using 10 commonly used angiographic scoring systems and interscore correlations were calculated. In a subset of 50 patients, plaque burden and plaque area in the left anterior descending coronary artery were quantified using IVUS and correlated with angiographic scores. Results All angiographic scores correlated with each other (range for Spearman coefficient ρ 0.79-0.98, P < .0001); the 2 most widely used scores, Gensini and CASS-70, had a ρ = 0.90 ( P < .0001). All scores correlated significantly with average plaque burden and plaque area by IVUS (range ρ 0.56-0.78, P < .0001 and 0.43-0.62, P < .01, respectively). The CASS-50 score had the strongest correlation ( ρ 0.78 and 0.62, P < .0001) and the Duke Jeopardy score the weakest correlation ( ρ 0.56 and 0.43, P < .01) with plaque burden and area, respectively. Conclusions Angiographic scoring systems are strongly correlated with each other and with atherosclerotic plaque burden. Scoring systems therefore appear to be a valid estimate of CAD plaque burden.
P300/CBP-associated factor (PCAF) and general control nonderepressible 5 (GCN5) are closely related epigenetic proteins, each containing an acetyltransferase domain and a bromodomain. Consistent with ...reported roles for these proteins in immune function, we find that PCAF-deficient macrophages exhibit a markedly reduced ability to produce cytokines upon stimulation with lipopolysaccharide (LPS). Investigating the potential to target this pathway pharmacologically, we show that chemical inhibition of the PCAF/GCN5 bromodomains is insufficient to recapitulate the diminished inflammatory response of PCAF-deficient immune cells. However, by generating the first PCAF/GCN5 proteolysis targeting chimera (PROTAC), we identify small molecules able to degrade PCAF/GCN5 and to potently modulate the expression of multiple inflammatory mediators in LPS-stimulated macrophages and dendritic cells. Our data illustrate the power of the PROTAC approach in the context of multidomain proteins, revealing a novel anti-inflammatory therapeutic opportunity for targeting PCAF/GCN5.
The bromo and extra C-terminal domain (BET) family of bromodomains are involved in binding epigenetic marks on histone proteins, more specifically acetylated lysine residues. This paper describes the ...discovery and structure–activity relationships (SAR) of potent benzodiazepine inhibitors that disrupt the function of the BET family of bromodomains (BRD2, BRD3, and BRD4). This work has yielded a potent, selective compound I-BET762 that is now under evaluation in a phase I/II clinical trial for nuclear protein in testis (NUT) midline carcinoma and other cancers.
Background Hybrid coronary revascularization (HCR) combines a minimally invasive (3-cm anterolateral thoracotomy), sternal-sparing, off-pump left internal mammary artery–left anterior descending ...(LIMA-LAD) coronary artery anastomosis with percutaneous coronary intervention (PCI) to non-LAD coronary arteries. We compared outcomes of HCR versus traditional off-pump coronary artery bypass grafting (OPCAB) for the treatment of multivessel coronary artery disease (CAD). Methods Between October 8, 2003 and April 23, 2010, 147 patients with multivessel coronary disease were treated with HCR at a US academic center. These were matched 4:1 to 588 contemporaneous patients treated with multivessel OPCAB by sternotomy using an optimal matching algorithm with 8 preoperative variables: age, gender, ejection fraction, presence of diabetes, myocardial infarction (MI), number of diseased vessels, left main coronary artery disease, and Society of Thoracic Surgeons (STS) predicted risk of mortality (PROM) score. In-hospital major adverse events (MACCE) and the need for repeated revascularization during follow-up were compared between groups. All-cause mortality was determined using the Social Security Death Index (SSDI). Results Matching produced groups with similar coronary anatomy and statistically similar preoperative risk factors. The incidence of MACCE was similar between groups (3/147 HCR versus 12/588 OPCAB). During a median 3.2 years of follow up, the need for repeated revascularization was higher for HCR than for OPCAB (18/147 12.2% versus 22/588 3.7%; p < 0.001). The incidence of blood transfusion was higher for the OPCAB group. Estimated 5-year survival was similar between groups (OPCAB, 84.3% versus HCR, 86.8%; p = 0.61). Conclusions Hybrid coronary revascularization is a minimally invasive treatment for multivessel CAD. Although repeated revascularization was greater with HCR, both in-hospital and midterm outcomes were comparable with those of traditional OPCAB. Further investigation into the comparative effectiveness of this alternative strategy is warranted.
We recently identified the splicing kinase gene SRPK1 as a genetic vulnerability of acute myeloid leukemia (AML). Here, we show that genetic or pharmacological inhibition of SRPK1 leads to cell cycle ...arrest, leukemic cell differentiation and prolonged survival of mice transplanted with MLL-rearranged AML. RNA-seq analysis demonstrates that SRPK1 inhibition leads to altered isoform levels of many genes including several with established roles in leukemogenesis such as MYB, BRD4 and MED24. We focus on BRD4 as its main isoforms have distinct molecular properties and find that SRPK1 inhibition produces a significant switch from the short to the long isoform at the mRNA and protein levels. This was associated with BRD4 eviction from genomic loci involved in leukemogenesis including BCL2 and MYC. We go on to show that this switch mediates at least part of the anti-leukemic effects of SRPK1 inhibition. Our findings reveal that SRPK1 represents a plausible new therapeutic target against AML.
Non-genetic drug resistance is increasingly recognised in various cancers. Molecular insights into this process are lacking and it is unknown whether stable non-genetic resistance can be overcome. ...Using single cell RNA-sequencing of paired drug naïve and resistant AML patient samples and cellular barcoding in a unique mouse model of non-genetic resistance, here we demonstrate that transcriptional plasticity drives stable epigenetic resistance. With a CRISPR-Cas9 screen we identify regulators of enhancer function as important modulators of the resistant cell state. We show that inhibition of Lsd1 (Kdm1a) is able to overcome stable epigenetic resistance by facilitating the binding of the pioneer factor, Pu.1 and cofactor, Irf8, to nucleate new enhancers that regulate the expression of key survival genes. This enhancer switching results in the re-distribution of transcriptional co-activators, including Brd4, and provides the opportunity to disable their activity and overcome epigenetic resistance. Together these findings highlight key principles to help counteract non-genetic drug resistance.
Latent reservoirs of HIV-1-infected cells are refractory to antiretroviral therapies (ART) and remain the major barrier to curing HIV-1. Because latently infected cells are long-lived, ...immunologically invisible, and may undergo homeostatic proliferation, a “shock and kill” approach has been proposed to eradicate this reservoir by combining ART with inducers of viral transcription. However, all attempts to alter the HIV-1 reservoir in vivo have failed to date. Using humanized mice, we show that broadly neutralizing antibodies (bNAbs) can interfere with establishment of a silent reservoir by Fc-FcR-mediated mechanisms. In established infection, bNAbs or bNAbs plus single inducers are ineffective in preventing viral rebound. However, bNAbs plus a combination of inducers that act by independent mechanisms synergize to decrease the reservoir as measured by viral rebound. Thus, combinations of inducers and bNAbs constitute a therapeutic strategy that impacts the establishment and maintenance of the HIV-1 reservoir in humanized mice.
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•bNAbs can be used for postexposure prophylaxis (PEP) in humanized mice•bNAb PEP efficacy requires Fc-receptor binding•bNAbs plus a single inducer of HIV-1 transcription do not reduce viral rebound•bNAbs plus a combination of inducers significantly reduce viral rebound
A combination of broadly neutralizing antibodies and viral inducers reduce the frequency of viral rebound in the humanized mouse model of HIV-1 infection.
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