NSD2 drives t(4;14) myeloma cell dependence on adenylate kinase 2 by diverting one-carbon metabolism to the epigenome

Chromosomal translocation (4;14), an adverse prognostic factor in multiple myeloma (MM), drives overexpression of the histone methyltransferase NSD2. A genome-wide CRISPR screen in MM cells identified adenylate kinase 2 (AK2), an enzyme critical for high energy phosphate transfer from the mitochondria, as an NSD2-driven vulnerability. AK2 suppression in t(4;14) MM cells decreased NADP(H) critical for conversion of ribonucleotides to deoxyribonucleosides, leading to replication stress, DNA damage and apoptosis. Driving a large genome-wide increase in chromatin methylation, NSD2 overexpression depletes S-adenosylmethionine (SAM), compromising synthesis of creatine from its precursor guanidinoacetate. Creatine supplementation restored NADP(H) levels, reduced DNA damage and rescued AK2-deficient t(4;14) MM cells. As the creatine phosphate shuttle constitutes an alternative means for mitochondrial high energy phosphate transport, these results indicate that NSD2-driven creatine depletion underlies the hypersensitivity of t(4;14) MM cells to AK2 loss. Furthermore, AK2 depletion in t(4;14) cells impaired protein folding in the endoplasmic reticulum consistent with impaired utilization of mitochondrial ATP. Accordingly, AK2 suppression increased sensitivity of MM cells to proteasome inhibition. These findings delineate a novel mechanism in which aberrant transfer of carbon to the epigenome creates a metabolic vulnerability, with direct therapeutic implications for t(4;14) MM.

KDM6A Regulates Immune Response Genes in Multiple Myeloma

The histone H3K27 demethylase KDM6A is a tumor suppressor in multiple cancers, including multiple myeloma (MM). We created isogenic MM cells disrupted for KDM6A and tagged the endogenous protein to facilitate genome wide studies. KDM6A binds genes associated with immune recognition and cytokine signaling. Most importantly, KDM6A binds and activates NLRC5 and CIITA encoding regulators of Major Histocompatibility Complex (MHC) genes. Patient data indicate that NLRC5 and CIITA, are downregulated in MM with low KDM6A expression. Chromatin analysis shows that KDM6A binds poised and active enhancers and KDM6A loss led to decreased H3K27ac at enhancers, increased H3K27me3 levels in body of genes bound by KDM6A and decreased gene expression. Reestablishing histone acetylation with an HDAC3 inhibitor leads to upregulation of MHC expression, offering a strategy to restore immunogenicity of KDM6A deficient tumors. Loss of Kdm6a in murine RAS-transformed fibroblasts led to increased growth in vivo associated with decreased T cell infiltration.

Statement of significance

We show that KDM6A participates in immune recognition of myeloma tumor cells by directly regulating the expression of the master regulators of MHC-I and II, NLRC5 and CIITA. The expression of these regulators can by rescued by the HDAC3 inhibitors in KDM6A-null cell lines.

HDAC8-mediated inhibition of EP300 drives a transcriptional state that increases melanoma brain metastasis

Melanomas can adopt multiple transcriptional states. Little is known about the epigenetic drivers of these cell states, limiting our ability to regulate melanoma heterogeneity. Here, we identify stress-induced HDAC8 activity as driving melanoma brain metastasis development. Exposure of melanocytes and melanoma cells to multiple stresses increases HDAC8 activation leading to a neural crest-stem cell transcriptional state and an amoeboid, invasive phenotype that increases seeding to the brain. Using ATAC-Seq and ChIP-Seq we show that increased HDAC8 activity alters chromatin structure by increasing H3K27ac and enhancing accessibility at c-Jun binding sites. Functionally, HDAC8 deacetylates the histone acetyltransferase EP300, causing its enzymatic inactivation. This, in turn, increases binding of EP300 to Jun-transcriptional sites and decreases binding to MITF-transcriptional sites. Inhibition of EP300 increases melanoma cell invasion, resistance to stress and increases melanoma brain metastasis development. HDAC8 is identified as a mediator of transcriptional co-factor inactivation and chromatin accessibility that drives brain metastasis.

Histone mutations in cancer

Genes encoding histone proteins are recurrently mutated in tumor samples, and these mutations may impact nucleosome stability, histone post-translational modification, or chromatin dynamics. The prevalence of histone mutations across diverse cancer types suggest that normal chromatin structure is a barrier to tumorigenesis. Oncohistone mutations disrupt chromatin structure and gene regulatory mechanisms, resulting in aberrant gene expression and the development of cancer phenotypes. Examples of oncohistones include the histone H3 K27M mutation found in pediatric brain cancers that blocks post-translational modification of the H3 N-terminal tail and the histone H2B E76K mutation found in some solid tumors that disrupts nucleosome stability. Oncohistones may comprise a limited fraction of the total histone pool yet cause global effects on chromatin structure and drive cancer phenotypes. Here, we survey histone mutations in cancer and review their function and role in tumorigenesis.

SMYD3 represses tumor-intrinsic interferon response in HPV-negative squamous cell carcinoma of the head and neck

Cancers often display immune escape, but the mechanisms are incompletely understood. Herein, we identify SMYD3 as a mediator of immune escape in human papilloma virus (HPV)-negative head and neck squamous cell carcinoma (HNSCC), an aggressive disease with poor response to immunotherapy with pembrolizumab. SMYD3 depletion induces upregulation of multiple type I interferon (IFN) response and antigen presentation machinery genes in HNSCC cells. Mechanistically, SMYD3 binds to and regulates the transcription of UHRF1, encoding for a reader of H3K9me3, which binds to H3K9me3-enriched promoters of key immune-related genes, recruits DNMT1, and silences their expression. SMYD3 further maintains the repression of immune-related genes through intragenic deposition of H4K20me3. In vivo, Smyd3 depletion induces influx of CD8+ T cells and increases sensitivity to anti-programmed death 1 (PD-1) therapy. SMYD3 overexpression is associated with decreased CD8 T cell infiltration and poor response to neoadjuvant pembrolizumab. These data support combining SMYD3 depletion strategies with checkpoint blockade to overcome anti-PD-1 resistance in HPV-negative HNSCC.

First-in-class multifunctional TYMS nonclassical antifolate inhibitor with potent in vivo activity that prolongs survival

Although thymidylate synthase (TYMS) inhibitors have served as components of chemotherapy regimens, the currently available inhibitors induce TYMS overexpression or alter folate transport/metabolism feedback pathways that tumor cells exploit for drug resistance, limiting overall benefit. Here we report a small molecule TYMS inhibitor that i) exhibited enhanced antitumor activity as compared with current fluoropyrimidines and antifolates without inducing TYMS overexpression, ii) is structurally distinct from classical antifolates, iii) extended survival in both pancreatic xenograft tumor models and an hTS/Ink4a/Arf null genetically engineered mouse tumor model, and iv) is well tolerated with equal efficacy using either intraperitoneal or oral administration. Mechanistically, we verify the compound is a multifunctional nonclassical antifolate, and using a series of analogs, we identify structural features allowing direct TYMS inhibition while maintaining the ability to inhibit dihydrofolate reductase. Collectively, this work identifies nonclassical antifolate inhibitors that optimize inhibition of thymidylate biosynthesis with a favorable safety profile, highlighting the potential for enhanced cancer therapy.

Abstract 3935: CRISPR/Cas9 screens to identify proliferation and resistance mechanisms in uveal melanoma

Purpose: Uveal (ocular) melanoma (UM) is a highly aggressive and frequently fatal cancer of the eye. While only 2-4% of patients have metastases at diagnosis, up to 50% of develop metastatic disease, overwhelmingly to the liver. Almost all UM harbor an initiating mutation in the Gαq signaling pathway, most commonly in GNAQ. Most UM also contain secondary mutations that drive tumor progression, the most common being BAP1 loss. Targeted therapies such as MEK inhibitors have been utilized in UM, but tumors rapidly become refractory. The aims of this study were to identify novel mechanisms specifically activated in UM cells that drive proliferation and escape from MEK inhibitor therapy.

Procedures: We performed CRISPR-Cas9 mediated gene disruption screening of UM cell lines 92.1, Mel202 and Mel270 using the Brunello sgRNA library targeting the whole genome. Cells were transduced at 0.3 MOI and 500X coverage then split into two groups to compare treatment with the MEK inhibitor (MEKi) trametinib (6nM) vs. untreated control cells. Cell pellets were collected at day 2 (baseline) and after every 3 cell divisions for 21 cell divisions (treated and control). In addition, we generated 92.1 and Mel270 cell lines stably expressing Cas9 and transduced cells at 1000x coverage with a sgRNA library targeting either 192 epigenetic regulators or 482 kinases. At least two replicates for each screen were performed. sgRNA representation between samples was compared using MAGeCK. Genes specifically essential in UM cell lines were distinguished from commonly essential genes using the Broad institute dependency map (DepMap). These hits were validated by individual sgRNAs and pharmacological inhibition.

Results: Whole genome screens revealed a set of 84 genetic dependencies unique for UM cells that were required for proliferation. Among these genes were those required for the lipoic acid biosynthesis pathway: MCAT, MECR, LIPT2, LIAS as well as genes encoding the MITF-SOX10-TFAP2 transcription factors, the H3K9 methyltransferase SETDB1, and members of the MLL3/4 complex. Screening of UM cell lines with a focused guide RNA library targeting epigenetic regulators revealed that BRD2, TRIM28, KMT2D, SETD1B and HDAC1 were specifically required for UM survival. Screens with a sgRNA library targeting the kinome revealed CDK2, CDK4 and TRRAP were required for UM survival. After 1 week of treatment with MEKi trametinib, we identified 112 genes whose disruption increased the anti-proliferative effects of trametinib in Mel202 and Mel270 cells and 10 of these genes were essential only in UM. These genes included metabolic enzymes critical for fatty and lipoic acid synthesis such as MECR, MCAT and TAZ. By contrast disruption of TP53, NF1, or PTEN led to MEKi resistance.

Conclusions: These results identify novel mechanisms of proliferation and therapy resistance specifically required in GNAQ mutant UM cells that may represent new therapeutic targets.

Citation Format: Richard L. Bennett, Darby Monagle, Katelyn R. Raburn Smith, Amin Sobh, Keiran S. Smalley, J William Harbour, Jonathan D. Licht. CRISPR/Cas9 screens to identify proliferation and resistance mechanisms in uveal melanoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3935.

Abstract 4747: NSD2 mutation drives oncogenic programming in mantle cell lymphoma

Background: NSD2, a histone methyltransferase, is an oncoprotein first characterized by its overexpression in multiple myeloma (MM). NSD2 mutations within the catalytic SET domain are found in acute lymphoblastic leukemia (ALL) and mantle cell lymphoma (MCL). We previously demonstrated that NSD2 p.E1099K mutation caused an imbalance of H3K36me2/H3K27me3 and drove glucocorticoid resistance in ALL. NSD2 mutations, especially p.E1099K and p.T1150A, were identified in 10-15% of cases of MCL and are enriched in patients who relapse from targeted therapies such as ibrutinib. However, the activity of NSD2 mutations in MCL remains unexplored.

Aim: To demonstrate the role of NSD2 mutations in MCL progression due to aberrant chromatin modification.

Methods: We created isogenic MCL cell lines by knock-in NSD2 p.E1099K mutation into Z138 and Jeko-1 cell lines using CRISPR/Cas9 gene editing. We then determined the effect of the mutation on H3K36me2/H3K27me3 levels and biological activities including cell growth (IncuCyte), apoptosis (Annexin V/PI Staining), and cell cycle (BrdU incorporation). We determined transcriptome (RNA-Seq) and histone modification profiles (ChIP-Seq) in isogenic Z138 cell lines. Finally, we integrated analysis of RNA-Seq of human patients and our human MCL cell lines to comprehensively disclose the epigenetic landscape in MCL with NSD2 mutation.

Results: We successfully created isogenic Z138 cell lines with heterozygous and homozygous NSD2 p.E1099K mutation and a Jeko-1 cell line with heterozygous NSD2 p.E1099K mutation. Insertion of NSD2 p.E1099K by CRISPR/Cas9 gene editing led to a striking increase of H3K36me2 and concomitant decrease of H3K27me3 in both Z138 and Jeko-1 cell lines. NSD2 mutation significantly increased cellular growth with enhanced S phase entry, decreased number of cells in G0/G1 phase and decreased spontaneous apoptosis. RNA-Seq analysis demonstrated striking changes in gene expression with 1794 genes upregulated and 1492 genes downregulated in NSD2 mutant MCL cells. Among them, anti-apoptotic genes BCL2 and BCL2L2 were upregulated while pro-apoptotic genes BAX, BID, and BIK were downregulated in NSD2 mutant cells, which was consistent with the biological phenotypes. Surprisingly, CCND1, CCNE1, CCNE2, TP53, and CDKN2C (p21) were downregulated while CDKN2D, CDKL3, and CDKL5 were upregulated in NSD2 mutant cells. Altered gene expression in isogenic Z138 cells were compared with patient expression profiles, with gene ontology revealing significant overlap and enrichment of cell adhesion, neural pathways, and evidence of activated signaling. Aberrant histone modification H3K27ac contributed to many of differentially expressed genes pattern.

Conclusions: The NSD2 mutation led to increased tumor cell growth but decreased apoptosis due to the dysregulation of epigenetic landscape and transcriptome, suggesting an oncogenic reprogramming driven by an activated NSD2 mutation in MCL.

Citation Format: Jianping Li, Marta Kulis, Alberto Riva, Heidi Casellas Román, Daphne Dupere-Richer, Amin Sobh, Charlotte Leonie Kaestner, Richard L. Bennett, Inaki Martin, Jonathan D. Licht. NSD2 mutation drives oncogenic programming in mantle cell lymphoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4747.

Abstract 3484: Oncohistone H2B-E76K alters gene expression & cellular phenotype in a bronchial epithelial cell line

The nucleosome is the basic unit of chromatin, comprising 147 bp of DNA wrapped around an octamer of core histone proteins H2A, H2B, H3 and H4. Compact chromatin acts as a barrier to gene expression and is a key property governing DNA replication and gene expression. Analyzing over 46,000 in cancer patient samples in cBioPortal, we characterized mutations located in canonical histone genes and found several recurrent missense mutations. Foremost among the identified mutations was a glutamate to lysine missense mutation at amino acid 76 of histone H2B (H2B-E76K) that disrupts histone H2B-H4 interaction. Previously, we demonstrated that exogenous expression of H2B-E76K disrupted nucleosome stability, altered chromatin accessibility, and gene expression. We developed a new model utilizing CRISPR “knock-in” technology to integrate the E76K mutation into the endogenous H2BC4 gene of the lung epithelial cell line BEAS-2B to create a homozygous and heterozygous H2B-E76K cell line. Although the mutant histone only accounts for about 2-5% of total histone H2B, expression of H2B-E76K catalyzed distinct changes in cell migration, proliferation, colony formation and gene expression. CUT&RUN technology revealed mutant histones broadly incorporate throughout the genome. Gene set enrichment analysis (GSEA) revealed that H2B-E76K homozygous cells displayed expression changes similar to polycomb repressive complex 1 (PRC1) disruption or oncogenic KRAS expression. Using available datasets, we discovered that expression of H2B-E76K caused increased expression of PTN, PKIB, and CDH2, genes important in migration, epithelial-mesenchymal transition (EMT), and adhesion pathways. Furthermore, analysis of chromatin accessibility changes indicated that increased accessibility was significant in and around genes governing cell migration. Notably, H2B-E76K significantly increased heterogeneity of gene expression as measured using scRNA-seq. Together these results indicate that mutations disrupting histone structure may create millions of dysfunctional nucleosomes and new sites of “open” chromatin, resulting in loss of nucleosome-mediated gene repression and/or altered interactions with regulators of chromatin, fundamentally changing cell growth and migration properties to favor tumorigenesis.

Citation Format: Kimberly Espinoza Pereira, Richard L. Bennett, Jixiu Shan, Jay Sarthy, Jonathan D. Licht. Oncohistone H2B-E76K alters gene expression & cellular phenotype in a bronchial epithelial cell line [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3484.

Evaluation of mRNA-1273 Vaccine in Children 6 Months to 5 Years of Age

BACKGROUND

The safety, reactogenicity, immunogenicity, and efficacy of the mRNA-1273 coronavirus disease 2019 (Covid-19) vaccine in young children are unknown.

METHODS

Part 1 of this ongoing phase 2-3 trial was open label for dose selection; part 2 was an observer-blinded, placebo-controlled evaluation of the selected dose. In part 2, we randomly assigned young children (6 months to 5 years of age) in a 3:1 ratio to receive two 25-μg injections of mRNA-1273 or placebo, administered 28 days apart. The primary objectives were to evaluate the safety and reactogenicity of the vaccine and to determine whether the immune response in these children was noninferior to that in young adults (18 to 25 years of age) in a related phase 3 trial. Secondary objectives were to determine the incidences of Covid-19 and severe acute respiratory syndrome coronavirus 2 infection after administration of mRNA-1273 or placebo.

RESULTS

On the basis of safety and immunogenicity results in part 1 of the trial, the 25-μg dose was evaluated in part 2. In part 2, 3040 children 2 to 5 years of age and 1762 children 6 to 23 months of age were randomly assigned to receive two 25-μg injections of mRNA-1273; 1008 children 2 to 5 years of age and 593 children 6 to 23 months of age were randomly assigned to receive placebo. The median duration of follow-up after the second injection was 71 days in the 2-to-5-year-old cohort and 68 days in the 6-to-23-month-old cohort. Adverse events were mainly low-grade and transient, and no new safety concerns were identified. At day 57, neutralizing antibody geometric mean concentrations were 1410 (95% confidence interval [CI], 1272 to 1563) among 2-to-5-year-olds and 1781 (95% CI, 1616 to 1962) among 6-to-23-month-olds, as compared with 1391 (95% CI, 1263 to 1531) among young adults, who had received 100-μg injections of mRNA-1273, findings that met the noninferiority criteria for immune responses for both age cohorts. The estimated vaccine efficacy against Covid-19 was 36.8% (95% CI, 12.5 to 54.0) among 2-to-5-year-olds and 50.6% (95% CI, 21.4 to 68.6) among 6-to-23-month-olds, at a time when B.1.1.529 (omicron) was the predominant circulating variant.

CONCLUSIONS

Two 25-μg doses of the mRNA-1273 vaccine were found to be safe in children 6 months to 5 years of age and elicited immune responses that were noninferior to those in young adults. (Funded by the Biomedical Advanced Research and Development Authority and National Institute of Allergy and Infectious Diseases; KidCOVE ClinicalTrials.gov number, NCT04796896.).

Abstract 3719: Loss of Kmt2c, of the COMPASS-like complex, cooperates with oncogenic signaling in cancer

In mammals, the histone methyltransferase KMT2C is one of the major regulators of gene expression and is one of the most commonly lost epigenetic regulators across all cancers. Studies in mice demonstrated that Kmt2c is a haploinsufficient tumor suppressor in AML and inoculation of mammary fat pads with breast cancer cells that lack KMT2C had significantly larger tumor growth and reduced survival compared to mice injected with isogenic wild-type cells. Analysis of cBioportal’s curated set of non-redundant cancer patient studies indicates that loss of function KMT2C mutations significantly co-occur with RAS gain of function mutations. Our lab previously discovered that cells expressing oncogenic RAS displayed altered activation of enhancer gene regulator elements. We will test how loss of KMT2C cooperates with oncogenic Ras by: 1) characterizing the impact of KMT2C loss, with or without expression of oncogenic RAS, on biological properties of cells and global chromatin architecture and 2) characterizing how KMT2C loss may cooperate with oncogenic RAS to alter hematopoiesis and the global enhancer landscape in animal models. MEFs expressing heterozygous loss of Kmt2c have a proliferative advantage relative to WT littermate controls. Interestingly, WT MEFs demonstrate enhanced migration in a wound assay, but heterozygotes demonstrate an advantage in a transwell membrane assay. Heterozygotes further display greater EdU incorporation, indicating a greater propensity for entering S-phase and undergoing cell-division. RNA-seq experiments have indicated an upregulation of MAPK & Ras signaling pathway genes in heterozygotes, whilst simultaneously downregulating gene pathways critical for proper extra-cellular matrix organization. Therefore, loss of Kmt2c disrupts biological cell phenotypes, in a manner relatable to the hallmarks of cancer, demonstrating how Kmt2c loss may promote malignancy. Further studies must now be performed to elucidate the molecular mechanisms altered by loss of KMT2C and how they cause changes in cellular phenotypes.

Citation Format: Gabriel Prado, Richard L. Bennett, Jonathan D. Licht. Loss of Kmt2c, of the COMPASS-like complex, cooperates with oncogenic signaling in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3719.

Abstract 4055: First in class multifunctional non classical antifolates inhibits thymidylate synthase and extends survival in pancreatic cancer model

Thymidylate synthase (TS) inhibitors are an integral component of chemotherapy regimens for difficult to treat cancer subtypes. Despite initial therapeutic benefit, current inhibitors induce TS overexpression or alter folate transport metabolism feedback pathways that tumor cells exploit for drug resistance. Here we report a small molecule TS inhibitor that exhibits i) enhanced antitumor activity as compared to current fluoropyrimidines and antifolates without inducing TS overexpression, ii) is structurally distinct from classical antifolates, iii) extends survival in a pancreatic tumor mouse model, iv) and is well tolerated with equal efficacy using either intraperitoneal or oral administration. Mechanistically, we confirm the compound is a multifunctional non classical antifolate and through a series of analogues identify structural features allowing direct TS inhibition while also maintaining the ability to inhibit dihydrofolate reductase (DHFR). Collectively, this work identifies new non classical antifolate inhibitors that optimize inhibition of thymidylate biosynthesis with a favorable safety profile highlighting potential for enhanced cancer therapy.

Citation Format: Maria V. Guijarro, Patrick C. Kellish, Peter E. Dib, Nicholas G. Paciaroni, Akbar Nawab, Jacob Andring, Lidia Kulemina, Nicholas V. Borrero, Carlos Modenutti, Richard L. Bennett, Daniil Shabashvili, Jonathan D. Licht, Robert McKenna, Adrian Roitberg, Robert W. Huigens, Frederic J. Kaye, Maria Zajac-Kaye. First in class multifunctional non classical antifolates inhibits thymidylate synthase and extends survival in pancreatic cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4055.

PRC2 Inhibitors Overcome Glucocorticoid Resistance Driven by NSD2 Mutation in Pediatric Acute Lymphoblastic Leukemia

Mutations in epigenetic regulators are common in relapsed pediatric acute lymphoblastic leukemia (ALL). Here, we uncovered the mechanism underlying the relapse of ALL driven by an activating mutation of the NSD2 histone methyltransferase (p.E1099K). Using high-throughput drug screening, we found that NSD2-mutant cells were specifically resistant to glucocorticoids. Correction of this mutation restored glucocorticoid sensitivity. The transcriptional response to glucocorticoids was blocked in NSD2-mutant cells due to depressed glucocorticoid receptor (GR) levels and the failure of glucocorticoids to autoactivate GR expression. Although H3K27me3 was globally decreased by NSD2 p.E1099K, H3K27me3 accumulated at the NR3C1 (GR) promoter. Pretreatment of NSD2 p.E1099K cell lines and patient-derived xenograft samples with PRC2 inhibitors reversed glucocorticoid resistance in vitro and in vivo. PRC2 inhibitors restored NR3C1 autoactivation by glucocorticoids, increasing GR levels and allowing GR binding and activation of proapoptotic genes. These findings suggest a new therapeutic approach to relapsed ALL associated with NSD2 mutation. SIGNIFICANCE: NSD2 histone methyltransferase mutations observed in relapsed pediatric ALL drove glucocorticoid resistance by repression of the GR and abrogation of GR gene autoactivation due to accumulation of K3K27me3 at its promoter. Pretreatment with PRC2 inhibitors reversed resistance, suggesting a new therapeutic approach to these patients with ALL.This article is highlighted in the In This Issue feature, p. 1.

DNMT3A Harboring Leukemia-Associated Mutations Directs Sensitivity to DNA Damage at Replication Forks

PURPOSE

In acute myeloid leukemia (AML), recurrent DNA methyltransferase 3A (DNMT3A) mutations are associated with chemoresistance and poor prognosis, especially in advanced-age patients. Gene-expression studies in DNMT3A-mutated cells identified signatures implicated in deregulated DNA damage response and replication fork integrity, suggesting sensitivity to replication stress. Here, we tested whether pharmacologically induced replication fork stalling, such as with cytarabine, creates a therapeutic vulnerability in cells with DNMT3A(R882) mutations.

EXPERIMENTAL DESIGN

Leukemia cell lines, genetic mouse models, and isogenic cells with and without DNMT3A(mut) were used to evaluate sensitivity to nucleoside analogues such as cytarabine in vitro and in vivo, followed by analysis of DNA damage and signaling, replication restart, and cell-cycle progression on treatment and after drug removal. Transcriptome profiling identified pathways deregulated by DNMT3A(mut) expression.

RESULTS

We found increased sensitivity to pharmacologically induced replication stress in cells expressing DNMT3A(R882)-mutant, with persistent intra-S-phase checkpoint activation, impaired PARP1 recruitment, and elevated DNA damage, which was incompletely resolved after drug removal and carried through mitosis. Pulse-chase double-labeling experiments with EdU and BrdU after cytarabine washout demonstrated a higher rate of fork collapse in DNMT3A(mut)-expressing cells. RNA-seq studies supported deregulated cell-cycle progression and p53 activation, along with splicing, ribosome biogenesis, and metabolism.

CONCLUSIONS

Together, our studies show that DNMT3A mutations underlie a defect in recovery from replication fork arrest with subsequent accumulation of unresolved DNA damage, which may have therapeutic tractability. These results demonstrate that, in addition to its role in epigenetic control, DNMT3A contributes to preserving genome integrity during replication stress.

Abstract 2117: Immunomodulatory functions of SMYD3 in HPV-negative head and neck squamous cell carcinoma

Background: Head and neck squamous cell carcinoma (HNSCC) causes approximately 10,000 deaths annually in the United States, with human-papilloma-virus (HPV)-negative patients having a particularly poor prognosis. Pembrolizumab, a programmed-death-1 (PD-1) antibody, was recently approved as a first-line therapy for patients with relapsed disease, however response rates are as low as 19%, underscoring the need for an improved understanding of immunotherapy resistance mechanisms. We have previously shown that HPV-negative HNSCC tumors with higher mRNA levels of SET and MYND Domain Containing 3 (SMYD3), a chromatin modifier known to trimethylated H3K4 (H3K4me3), have significantly lower mRNA levels of CD8 and CD8+ T-cell attracting chemokines, and that SMYD3 depletion in HNSCC cells in vitro leads to upregulation of CD8+ T-cell attracting chemokines. The goal of this work was to elucidate epigenetic mechanisms of immune evasion mediated by SMYD3 in HPV-negative HNSCC.

Methods: siRNA- mediated SMYD3 knockdown was performed for 3 days to investigate immuno-modulatory epigenetic mechanisms mediated by SMYD3. RT-qPCR for immune-related genes, Western blotting for histone marks, ChIP-sequencing for H3K4me3, ChIP-qPCRs to determine genomic interactions of SMYD3 and ATAC-sequencing were performed. SMYD3 and CD8 immunohistochemical staining (IHC) of normal squamous, dysplastic epithelium and HPV-negative HNSCC tumors was also performed.

Results: siRNA mediated knockdown of SMYD3 resulted in enrichment of inflammatory pathways and upregulation of type 1 interferon response and antigen presentation machinery genes in HNSCC cell lines. Immunoblotting for histone marks showed no reduction in H3K4me3 following SMYD3 depletion for 3 days. ChIP-sequencing for H3K4me3 showed differential distribution pattern with an increase of H3K4me3 peaks on immune-related genes, and a decrease of H3K4me3 on UHRF1, a reader of the repressive histone mark H3K9me3. RNA-seq, RT-PCR and ChIP-qPCR showed that SMYD3 may regulate the transcription of UHRF1 by binding to its promoter. SMYD3 depletion also led to decreased protein levels of UHRF1. ChIP for UHRF1 and H3K9me3 showed that UHRF1 binds directly on the promoters of CXCL9 and CXCL10 which are enriched for H3K9me3. IHC on Normal Squamous Epithelium and Squamous Cell Carcinoma tissues of increasing cancer stages showed increase in SMYD3 levels with the higher stage of cancer, and an inverse correlation with CD8+ T cell infiltration within the tumors.

Conclusion: This is the first study reporting that the chromatin modifier SMYD3 may attenuate type I IFN responses in HPV-negative HNSCC by regulating the expression of a major epigenetic regulator, UHRF1, which may silence the expression of immune-related genes through H3K9me3.

Citation Format: Nupur Nigam, Benjamin Jonah Bernard, Kyunghee Burkitt, Sohyoung Kim, Yvette Robbins, Richard L. Bennett, Jonathan D. Licht, Vassiliki Saloura. Immunomodulatory functions of SMYD3 in HPV-negative head and neck squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2117.

Leveraging epigenetics to enhance the efficacy of immunotherapy

Background

Epigenetic mechanisms regulate chromatin accessibility patterns that govern interaction of transcription machinery with genes and their cis-regulatory elements. Mutations that affect epigenetic mechanisms are common in cancer. Because epigenetic modifications are reversible many anticancer strategies targeting these mechanisms are currently under development and in clinical trials.

Main body

Here we review evidence suggesting that epigenetic therapeutics can deactivate immunosuppressive gene expression or reprogram tumor cells to activate antigen presentation mechanisms. In addition, the dysregulation of epigenetic mechanisms commonly observed in cancer may alter the immunogenicity of tumor cells and effectiveness of immunotherapies.

Conclusions

Therapeutics targeting epigenetic mechanisms may be helpful to counter immune evasion and improve the effectiveness of immunotherapies.

Targeting epigenetic mechanisms to overcome venetoclax resistance

The BH-3 mimetic venetoclax overcomes apoptosis and therapy resistance caused by high expression of BCL2 or loss of BH3-only protein function. Although a promising therapy for hematologic malignancies, increased expression of anti-apoptotic MCL-1 or BCL-XL, as well as other resistance mechanisms prevent a durable response to venetoclax. Recent studies demonstrate that agents targeting epigenetic mechanisms such as DNA methyltransferase inhibitors, histone deacetylase (HDAC) inhibitors, histone methyltransferase EZH2 inhibitors, or bromodomain reader protein inhibitors may disable oncogenic gene expression signatures responsible for venetoclax resistance. Combination therapies including venetoclax and epigenetic therapies are effective in preclinical models and the subject of many current clinical trials. Here we review epigenetic strategies to overcome venetoclax resistance mechanisms in hematologic malignancies.

1044 Adequate Sleep is Associated with Improved Diabetes Knowledge and HbA1c

Introduction

Although 55 % of the people with T2DM have low quality of sleep that may affect their physical and emotional wellbeing, and present challenges to the management of their condition, many Diabetes Self-Management Education Programs (DSME) that aim to improve knowledge of T2DM, don’t include information on healthy sleep. This study will examine the relationship between adequate sleep on improved T2DM knowledge and diabetes maintenance (HbA1c).

Methods

The Sleep Integrated with Diabetes Education (SLIDE) Trial tests whether including four brief healthy sleep hygiene sessions within an existing traditional Diabetes Self-Management Education Program improves healthy sleep, motivation for change, and biopsychosocial outcomes for 50 patients with DM who are under and uninsured. This study uses descriptive and ANOVAs to examine the relationship between adequate sleep and change in diabetes knowledge (Diabetes Knowledge Test) using self-report. EMR was used to link HbA1c and other biological measures.

Results

Fifty patients with T2DM (mean HbA1c = 8.79 ± 2.42) participating in a DSME Program at a southern urban community nonprofit hospital were randomly assigned to DSME classes or DSME classes + four 15-minute presentations (video and powerpoint) highlighting healthy sleep hygiene practices. The majority of these patients were obese (mean BMI=38.56±8.20). Only 11% reported normal sleep, with 41% reporting short sleep (<6 hours) and 7% long sleep (>8 hours). Patients who reported adequate sleep were more likely to improve diabetes knowledge (81% score vs. 68% score, p<.001) and HbA1c (1.1 vs. -.03, p<.001).

Conclusion

There is a relationship between adequate sleep and improving diabetes knowledge and maintenance for patients with T2DM. Future research could further explore this relationship and determine barriers and facilitators to adequate sleep and what role adequate sleep plays in improving T2DM knowledge and maintenance.

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Bon Sequor Foundation

A Mutation in Histone H2B Represents a New Class of Oncogenic Driver

By examination of the cancer genomics database, we identified a new set of mutations in core histones that frequently recur in cancer patient samples and are predicted to disrupt nucleosome stability. In support of this idea, we characterized a glutamate to lysine mutation of histone H2B at amino acid 76 (H2B-E76K), found particularly in bladder and head and neck cancers, that disrupts the interaction between H2B and H4. Although H2B-E76K forms dimers with H2A, it does not form stable histone octamers with H3 and H4 in vitro, and when reconstituted with DNA forms unstable nucleosomes with increased sensitivity to nuclease. Expression of the equivalent H2B mutant in yeast restricted growth at high temperature and led to defective nucleosome-mediated gene repression. Significantly, H2B-E76K expression in the normal mammary epithelial cell line MCF10A increased cellular proliferation, cooperated with mutant PIK3CA to promote colony formation, and caused a significant drift in gene expression and fundamental changes in chromatin accessibility, particularly at gene regulatory elements. Taken together, these data demonstrate that mutations in the globular domains of core histones may give rise to an oncogenic program due to nucleosome dysfunction and deregulation of gene expression. SIGNIFICANCE: Mutations in the core histones frequently occur in cancer and represent a new mechanism of epigenetic dysfunction that involves destabilization of the nucleosome, deregulation of chromatin accessibility, and alteration of gene expression to drive cellular transformation.See related commentary by Sarthy and Henikoff, p. 1346.This article is highlighted in the In This Issue feature, p. 1325.

Defining the NSD2 interactome: PARP1 PARylation reduces NSD2 histone methyltransferase activity and impedes chromatin binding

NSD2 is a histone methyltransferase that specifically dimethylates histone H3 lysine 36 (H3K36me2), a modification associated with gene activation. Dramatic overexpression of NSD2 in t(4;14) multiple myeloma (MM) and an activating mutation of NSD2 discovered in acute lymphoblastic leukemia are significantly associated with altered gene activation, transcription, and DNA damage repair. The partner proteins through which NSD2 may influence critical cellular processes remain poorly defined. In this study, we utilized proximity-based labeling (BioID) combined with label-free quantitative MS to identify high confidence NSD2 interacting partners in MM cells. The top 24 proteins identified were involved in maintaining chromatin structure, transcriptional regulation, RNA pre-spliceosome assembly, and DNA damage. Among these, an important DNA damage regulator, poly(ADP-ribose) polymerase 1 (PARP1), was discovered. PARP1 and NSD2 have been found to be recruited to DNA double strand breaks upon damage and H3K36me2 marks are enriched at damage sites. We demonstrate that PARP1 regulates NSD2 via PARylation upon oxidative stress. In vitro assays suggest the PARylation significantly reduces NSD2 histone methyltransferase activity. Furthermore, PARylation of NSD2 inhibits its ability to bind to nucleosomes and further get recruited at NSD2-regulated genes, suggesting PARP1 regulates NSD2 localization and H3K36me2 balance. This work provides clear evidence of cross-talk between PARylation and histone methylation and offers new directions to characterize NSD2 function in DNA damage response, transcriptional regulation, and other pathways.

Targeting Epigenetics in Cancer

Alterations of genes regulating epigenetic processes are frequently found as cancer drivers and may cause widespread alterations of DNA methylation, histone modification patterns, or chromatin structure that disrupt normal patterns of gene expression. Because of the inherent reversibility of epigenetic changes, inhibitors targeting these processes are promising anticancer strategies. Small molecules targeting epigenetic regulators have been developed recently, and clinical trials of these agents are under way for hematologic malignancies and solid tumors. In this review, we describe how the writers, readers, and erasers of epigenetic marks are dysregulated in cancer and summarize the development of therapies targeting these mechanisms.

Targeting Epigenetics in Cancer

Alterations of genes regulating epigenetic processes are frequently found as cancer drivers and may cause widespread alterations of DNA methylation, histone modification patterns, or chromatin structure that disrupt normal patterns of gene expression. Because of the inherent reversibility of epigenetic changes, inhibitors targeting these processes are promising anticancer strategies. Small molecules targeting epigenetic regulators have been developed recently, and clinical trials of these agents are under way for hematologic malignancies and solid tumors. In this review, we describe how the writers, readers, and erasers of epigenetic marks are dysregulated in cancer and summarize the development of therapies targeting these mechanisms.

The Role of Nuclear Receptor-Binding SET Domain Family Histone Lysine Methyltransferases in Cancer

The nuclear receptor-binding SET Domain (NSD) family of histone H3 lysine 36 methyltransferases is comprised of NSD1, NSD2 (MMSET/WHSC1), and NSD3 (WHSC1L1). These enzymes recognize and catalyze methylation of histone lysine marks to regulate chromatin integrity and gene expression. The growing number of reports demonstrating that alterations or translocations of these genes fundamentally affect cell growth and differentiation leading to developmental defects illustrates the importance of this family. In addition, overexpression, gain of function somatic mutations, and translocations of NSDs are associated with human cancer and can trigger cellular transformation in model systems. Here we review the functions of NSD family members and the accumulating evidence that these proteins play key roles in tumorigenesis. Because epigenetic therapy is an important emerging anticancer strategy, understanding the function of NSD family members may lead to the development of novel therapies.

Sabotaging of the oxidative stress response by an oncogenic noncoding RNA

Overexpression of the multiple myeloma set domain (MMSET) Wolf-Hirschhorn syndrome candidate 1 gene, which contains an orphan box H/ACA class small nucleolar RNA, ACA11, in an intron, is associated with several cancer types, including multiple myeloma (MM). ACA11 and MMSET are overexpressed cotranscriptionally as a result of the t(4;14) chromosomal translocation in a subset of patients with MM. RNA sequencing of CD138⁺ tumor cells from t(4;14)-positive and -negative MM patient bone marrow samples revealed an enhanced oxidative phosphorylation mRNA signature. Supporting these data, ACA11 overexpression in a t(4;14)-negative MM cell line, MM1.S, demonstrated enhanced reactive oxygen species (ROS) levels. In addition, an enhancement of cell proliferation, increased soft agar colony size, and elevated ERK1/2 phosphorylation were observed. This ACA11-driven hyperproliferative phenotype depended on increased ROS levels as exogenously added antioxidants attenuate the increased proliferation. A major transcriptional regulator of the cellular antioxidant response, nuclear factor (erythroid-derived 2)-like 2 (NRF2), shuttled to the nucleus, as expected, in response to ACA11-driven increases in ROS; however, transcriptional up-regulation of some of NRF2's antioxidant target genes was abrogated in the presence of ACA11 overexpression. These data show for the first time that ACA11 promotes proliferation through inhibition of NRF2 function resulting in sustained ROS levels driving cancer cell proliferation.-Mahajan, N., Wu, H.-J., Bennett, R. L., Troche, C., Licht, J. D., Weber, J. D., Maggi, L. B., Jr., Tomasson, M. H. Sabotaging of the oxidative stress response by an oncogenic noncoding RNA.

Abstract 194: Increased PKR expression inhibits differentiation of hematopoietic stem cells

Acute myelogenous leukemia (AML) is characterized by a differentiation block at an early stage of hematopoiesis that results in the accumulation of immature myeloid cells and an impaired production of blood cells. This parallels findings in solid tumors that demonstrate differentiation stage is often associated with tumor behavior and generally an immature tumor is more aggressive than the more differentiated counterpart. Thus, new

research designed to more fully understand the mechanisms of cellular differentiation may improve our understanding of neoplastic transformation and identify new therapeutic targets. Recently our laboratory has determined that increased expression and activation of the interferon-inducible, dsRNA-activated kinase (PKR) is associated with shorter remission duration and worse survival for patients with AML. PKR is a key mediator of the cellular response to inflammatory stress that has been found to be upregulated by chronic inflammation and aging. Since we have previously reported that mice expressing a PKR transgene (TgPKR) in hematopoietic cells have a reduced number of bone marrow (BM) Lin-, Sca1+, cKit+ hematopoietic stem/progenitor cells (HSPCs) and develop a dysplastic BM with an increased frequency of BM blasts, we investigated whether PKR may affect HSPC differentiation. Results indicate that BM of TgPKR mice contains a significantly reduced number of multipotent progenitor cells (MPPs) that are more frequently arrested in G0/G1 than wild type (WT) mice. In contrast, BM of PKR knockout mice (PKRKO) have an increased frequency of proliferating MPPs (S+G2/M) but a decreased frequency of both Long-term (LT) and Short-term (ST) HSCs compared to either WT or TgPKR mice. Although LT-HSCs of TgPKR mice are more frequently quiescent in vivo they remain functional in vitro as demonstrated by nearly double the colony forming capacity compared to BM of PKRKO mice after >4 weeks in long term culture initiating cell (LTC-IC) assays. In addition, when differentiation of the myeloid cell line K562 is induced by PMA treatment, cells with reduced PKR expression by siRNA knockdown display an increased rate and extent of megakaryocyte differentiation compared to control cells. These findings suggest that increased PKR expression has a previously unrecognized function to inhibit hematopoietic cell differentiation. This may account for why TgPKR mice accumulate quiescent LT-HSCs and develop BM dysplasia with age. Furthermore, these results suggest that increased PKR expression/activation as observed in high-risk MDS, AML and other hematologic malignancies may contribute to leukemogenesis, at least in part, by blocking hematopoietic cell differentiation. In addition, these new findings may be applicable to solid tumors since increased PKR signaling has also been reported to be associated with a more rapid and aggressive course of tumor progression in breast cancer, melanoma and colon cancer.

Citation Format: Richard L. Bennett, Xiaodong Cheng, Michael T. Byrne, Amalin Asous, Mohini Patel, Zeel Patel, W. Stratford May. Increased PKR expression inhibits differentiation of hematopoietic stem cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 194.

Audit feedback on reading performance of screening mammograms: An international comparison

Objective

Providing feedback to mammography radiologists and facilities may improve interpretive performance. We conducted a web-based survey to investigate how and why such feedback is undertaken and used in mammographic screening programmes.

Methods

The survey was sent to representatives in 30 International Cancer Screening Network member countries where mammographic screening is offered.

Results

Seventeen programmes in 14 countries responded to the survey. Audit feedback was aimed at readers in 14 programmes, and facilities in 12 programmes. Monitoring quality assurance was the most common purpose of audit feedback. Screening volume, recall rate, and rate of screen-detected cancers were typically reported performance measures. Audit reports were commonly provided annually, but more frequently when target guidelines were not reached.

Conclusion

The purpose, target audience, performance measures included, form and frequency of the audit feedback varied amongst mammographic screening programmes. These variations may provide a basis for those developing and improving such programmes.

Progressive genomic instability in the Nup98-HoxD13 model of MDS correlates with loss of the PIG-A gene product

The Nup98-HoxD13 (NHD13) fusion gene was identified in a patient with therapy-related myelodysplastic syndrome (MDS). When transgenically expressed in hematopoietic cells, mice faithfully recapitulate human disease with serial progression from peripheral blood (PB) cytopenias and increased bone marrow (BM) blasts to acute leukemia. It is well accepted that genomic instability in dysplastic hematopoietic stem/progenitor cells (HSPC) drives the evolution of MDS to acute leukemia. Findings here demonstrate that reticulocytes, myeloid and lymphoid PB cells of NHD13 mice, display an increase in the age-associated loss of glycosylphosphatidylinositol-linked surface proteins versus wild type controls. These data correlate with a progressive increase in the DNA damage response as measured by γ-H2AX activity, accumulating BM blasts as the disease progresses and finally development of acute leukemia. These findings clearly demonstrate a state of progressive genomic instability that increases the likelihood of a “second hit” or complimentary mutation later in the disease to trigger development of acute leukemia and underscores the mechanistic nature of how the NUP98-HoxD13 transgene induces progression of MDS to acute leukemia. Additionally, these data support the use of the PIG-A assay as an efficient, real-time surrogate marker of the genomic instability that occurs in the MDS HSPCs.

Key Point

The PIG-A assay is a sensitive, nonlethal method for the serial assessment of genomic instability in mouse models of MDS.

Genetic Counseling for Fragile X Syndrome: Recommendations of the National Society of Genetic Counselors

The National Society of Genetic Counselors' (NSGC) recommendations for fragile X syndrome (FXS) genetic counseling are intended to assist health care professionals who provide genetic counseling for individuals and families in whom the diagnosis of FXS is strongly suspected or has been made. The recommendations are the opinions of genetic counselors with expertise in FXS counseling and are based on clinical experience, a review of pertinent English language medical articles, and reports of expert committees. These recommendations should not be construed as dictating an exclusive course of management, nor does use of such recommendations guarantee a particular outcome. These recommendations do not displace a health care provider's professional judgment based on the clinical circumstances of a particular client.

Cardiovascular safety of the glucagon-like peptide-1 receptor agonist taspoglutide in people with type 2 diabetes: an individual participant data meta-analysis of randomized controlled trials

AIMS

To study the short-term cardiovascular effects of the once-weekly glucagon-like peptide-1 receptor agonist taspoglutide.

METHODS

We conducted a meta-analysis of individual-participant data from nine randomized controlled trials in the T-Emerge programme, which assessed the efficacy and safety of taspoglutide in type 2 diabetes. Our primary outcome was a composite of death from cardiovascular disease (CVD) and acute myocardial infarction, stroke and hospitalization for unstable angina.

RESULTS

Overall, 7056 individuals were included in the analysis, and there were 67 primary endpoint events during 7478 person-years of follow-up (40 vs 27 events in the intervention vs control groups, respectively). The odds ratio for the composite endpoint among people randomized to taspoglutide was 0.94 (95% confidence interval 0.57-1.56), which was robust across multiple subgroups. Longer-term data were not available as the development of taspoglutide was stopped because of gastrointestinal intolerance and serious hypersensitivity reactions.

CONCLUSIONS

The available data suggest that short-term, once-weekly administration of taspoglutide was not associated with an excess risk of CVD, and provide insights relevant to the development of other novel once-weekly incretin mimetics.

Abstract 75: PKR cooperates with an MDS driver mutation to worsen cytopenias and promote acute leukemia

The interferon-inducible, dsRNA-dependent protein kinase, PKR, is activated by cellular stresses to inhibit protein synthesis and initiate apoptosis. Recently, we reported that expressing human PKR (TgPKR) in mouse hematopoietic tissues induced peripheral blood cytopenias and dysplastic changes in the bone marrow. Additionally, these findings were associated with reduced numbers of hematopoietic stem/progenitor cells (HSPCs) consistent with a myelodysplastic syndrome (MDS)-like phenotype. We have now tested whether TgPKR expression in HSPCs may cooperate with the Nup98-HoxD13 (NHD13) driver transgene. This NHD13 transgene induces a highly penetrant form of MDS with progression to acute leukemia in mice. TgPKR or PKR knockout (PKRKO) mice were crossed with the NHD13 transgenic mouse to generate TgPKR-NHD13 and PKRKO-NHD13 mice that were aged. The development of pancytopenia/MDS and evolution to acute leukemia were compared to NHD13 mice or to normal WT control mice.

Beginning at 5 months and persisting through 8 months of age, the TgPKR-NHD13 mice developed reduced WBC and platelet counts compared to NHD13 controls (WBC mean 2.6 vs. 3.5 x103 cells/µl, [p: < 0.01], and mean platelet counts of 576.9 vs. 814.3 x103 platelets/µl). Both cell types were significantly lower than WT controls. By contrast, PKRKO-NHD13 mice maintained higher WBC counts beginning at age 6 months (n=4) compared to NHD13 controls (n=13) (mean 7 vs. 2.5 x103 cells/µl, [6 mos.], 11.6 vs. 3.7 x103 cells/µl [7 mos.], 9.62 vs. 3.5 x103 cells/µl [8 mos.], p: <0.05).

To date, 1 of 13 of the NHD13 mice, aged 7-10 months, has developed acute leukemia. Of the TgPKR-NHD13 mice, 7 of 18 have died due to either acute leukemia (4/7), MDS with anemia requiring euthanasia (1/7), or due to unknown causes (2/7). By contrast, none of the PKRKO-NHD13 (n = 19) or WT mice (n= 11), both aged up to 9 months, have developed symptomatic MDS requiring euthanasia or acute leukemia

These data indicate that PKR may cooperate with the NHD13 driver oncogenic mutation to create a more aggressive MDS-like phenotype characterized by deeper peripheral blood cytopenias and an increased rate of evolution to AML. Alternatively, inhibition of PKR expression/activation may delay or forestall evolution of MDS/AML in the NHD13 background.

These findings suggest that PKR may be a potential novel therapeutic target in the treatment of MDS and its evolution to acute leukemia.

Citation Format: Michael T. Byrne, Richard L. Bennett, Xiaodong Cheng, W. Stratford May. PKR cooperates with an MDS driver mutation to worsen cytopenias and promote acute leukemia. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 75. doi:10.1158/1538-7445.AM2014-75

The need for developing standardized family pedigree nomenclature

To assess the variation in usage of symbols used in recording a genetic family history, full members of the National Society of Genetic Counselors were surveyed by questionnaire. The questionnaire return rate was 55.3% and genetic counselors from a broad range of clinical experience, genetic counseling training programs and geographic regions responded. There was striking variation in symbols used for recording routine medical information in a genetic family history (i.e., pregnancy, spontaneous abortion, termination of pregnancy). There was even less consensus in recording situations representing new reproductive technologies (i.e., artificial insemination by donor semen, donor ovum, surrogate motherhood). The results of this survey document the need for developing standardized nomenclature in recording genetic family histories as a quality assurance measure in the delivery of genetic services. Such standardization will reduce the chance of incorrect interpretation of patient and family medical and genetic information.

Abstract 5673: Novel inhibitors of the interferon-inducible, dsRNA-activated kinase PKR for myelodysplastic syndrome

In hematopoietic stem/progenitor cells, the interferon-inducible, dsRNA-activated protein kinase, PKR, is a central mediator for the anti-proliferative effects of a wide variety of hematopoietic, inflammatory or cytotoxic stresses such as deprivation of IL-3, IL-5 or GM-CSF from hematopoietic factor-dependent cells. Once activated, PKR inhibits protein synthesis by phosphorylation of eIF2alpha, inhibits mitochondrial function by activating PP2A-dependent Bcl2 dephosphorylation, and activates signaling pathways such as NF-kappaB, p53 and STAT1 to regulate proliferation and apoptosis in response to cellular stress. Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal hematologic malignancies characterized by peripheral cytopenias, a hypercellular marrow with ineffective hematopoiesis and risk of transformation to acute myeloid leukemia (AML). Significantly, PKR is highly activated in myeloid progenitor cells from MDS patients and inhibition of PKR activity or siRNA-knockdown partially reverses the suppressive effects of IFN-gamma and TNF-alpha on hematopoietic colony formation using normal or MDS-derived CD34+ cells. Thus, increased PKR activity in hematopoietic stem cells may cooperate with driver/founder mutations to promote bone marrow failure and apoptosis characteristic of MDS, and inhibitors of PKR may be therapeutically useful to delay the onset and/or reduce the severity of MDS and its evolution to AML. Since there is only one commercially available pharmacologic PKR inhibitor that targets ATP binding and has been reported to have off target effects, we performed studies to identify novel small molecule compounds that specifically inhibit PKR-substrate association. Using the crystal structure of the PKR kinase domain-eIF2alpha complex, we employed a molecular docking strategy to screen in silico the NIH Developmental Therapeutic Program's repository of over 300,000 small molecules for compounds that interact with and inhibit PKR. The top 195 scoring small molecule compounds identified were obtained and validated in vitro using a LanthaScreen PKR kinase assay and 32P PKR assay. In addition, we screened the NIH/DTP Diversity and Challenge Compound Sets for inhibitors of PKR (2047 compounds total). Using these methods, we have identified 27 novel PKR inhibitors with an IC50 < 100 μM. Significantly, five are competitive inhibitors for eIF2alpha binding to PKR while the remaining inhibit ATP binding. These results identify a novel class of PKR inhibitors that specifically disrupt association of PKR with its substrate, eIF2alpha, and lay the groundwork for future studies that test whether these PKR inhibitors may be therapeutically useful to delay the onset of cytopenias and bone marrow failure associated with MDS and MDS evolution to AML.

Citation Format: Richard L. Bennett, David A. Ostrov, W. Stratford May. Novel inhibitors of the interferon-inducible, dsRNA-activated kinase PKR for myelodysplastic syndrome. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5673. doi:10.1158/1538-7445.AM2013-5673

Abstract 2042: The RAX/PACT-PKR stress-signaling pathway promotes p53 sumoylation and stability to induce G1 arrest

Cellular stresses including IL-3 withdrawal from factor-dependent hematopoietic cells, inflammatory cytokine treatment or viral infection promote RAX/PACT-dependent activation of the interferon-induced, double-stranded RNA activated protein kinase PKR. Previously, we and others demonstrated that activated PKR phosphorylates the alpha subunit of eIF2 to inhibit protein synthesis and initiate apoptosis. In addition, recent reports indicate that PKR may regulate the transcription factors p53, STAT1 and NF-κB. Now we find that RAX/PACT interacts with the SUMO E2 ligase Ubc9 to stimulate p53-Ubc9 association and reversible p53 sumoylation on lysine 386. In addition, stable or transient expression of RAX/PACT in a variety of cell lines promotes p53 stability and activity to increase p53 target gene expression. Significantly, while expression of RAX/PACT, PKR or p53 alone has little effect on the cell cycle of p53-null H1299 cells, co-expression of p53 with either RAX/PACT or PKR promotes a 25 - 35% increase of cells in G1. In contrast, co-expression of RAX/PACT with the sumoylation-deficient p53 (K386R) mutant or with p53 and the desumoylase SENP1 fails to induce such a G1 arrest. Furthermore, RAX/PACT-induced, p53-dependent G1 growth arrest is inhibited by expressing the dominant-negative PKR (K296R) mutant, and expression of RAX/PACT in pkr+/+ but not pkr-/- MEF cells promotes p53 and p21 expression following gamma irradiation. Significantly, expression of exogenous RAX/PACT promotes phosphorylation of wild-type but not p53 (K386R) on serine 392, and p53 stability is decreased in cells with reduced RAX/PACT or PKR following doxorubicin treatment. Collectively, results indicate that in response to stress the RAX/PACT-PKR signaling pathway may promote p53 translational activation leading to G1 cell cycle arrest by a mechanism dependent on p53 sumoylation and phosphorylation that regulates protein turnover. Importantly, these novel findings may indicate a wider role for the RAX/PACT-PKR signaling pathway to direct sumoylation-dependent subcellular localization, protein stability or protein-protein interactions of downstream targets in response to cellular stress.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2042. doi:1538-7445.AM2012-2042

Abstract 1350: Transgenic expression of PKR induces a myelodysplastic syndrome/pre-leukemia-like condition in mice

Double stranded (ds) RNA activated protein kinase PKR was discovered over 30 years ago as a downstream mediator of the interferon signal pathway. Initial studies focused on PKR's anti-virus and pro-inflammatory effects. More recently, PKR has been found to be involved in signal transduction pathways critical for the negative regulation of cell growth and initiation of apoptosis. Significantly, loss of PKR expression/activity has been associated with increased growth of human breast carcinoma, B-cell CLL, and T-cell ALL using patient samples. Furthermore, PKR activity is increased in bone marrow progenitor cells isolated from patients with myelodysplastic syndrome (MDS) which undergo significant apoptosis compared to normal marrow progenitors not observed when evolved to AML. Thus, in the process of MDS evolution to leukemia, PKR expression/activity may be downregulated by a process that is currently unclear. To explore the role of PKR in MDS/AML we have constructed a transgenic mouse model expressing human PKR (TgPKR) under control of vav regulatory elements to drive expression specifically in hematopoietic-tissue. We hypothesized transgenic expression of human PKR would exert an inhibitory effect on mouse hematopoiesis, cause ineffective blood cell production, and thus simulate a disease process similar to human MDS. In our preliminary data, quantitative PCR and immunoblotting results confirm that human PKR is specifically expressed in spleen, thymus and bone marrow (BM) but not in liver, kidney, intestine, muscle and other tissues outside hematopoiesis in TgPKR mice. Aberrant activation of transcription factor STAT1 and MAPKinases ERK1/2 occurs in hematopoietic cells from the TgPKR mice. In addition, inhibitory cytokines including interferon gamma, CXCL9 and 10 are overexpressed. Initial characterization of BM cells from TgPKR mice indicates a higher level of uninduced/basal apoptosis in growth medium and increased apoptosis upon withdrawal of growth factors compared to cells from wild type (WT) littermates. Furthermore, BM cells from TgPKR mice display >20% reduced colonies (CFU-GM and CFU-GEMM) which contain 40% less cells than those from WT littermates. Significantly, histopathological analysis of BM and spleen from TgPKR mice reveals a ∼20% increase in bone marrow cellularity with a striking increase in dysplastic megakaryocytes that are either small without nuclear lobation or of normal size but with hypolobation or separated nuclear lobes. Taken together our results demonstrate that transgenic expression of hPKR induces an MDS-like condition in mice characterized by reduced BM cell survival, increased apoptosis and reduced proliferation and differentiation of BM progenitor/stem cells. Thus, increased PKR expression in patients may, at least in part, lead to a BM failure state similar to MDS. Thus, future anti-MDS therapies that inhibit PKR may be clinically useful.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1350. doi:1538-7445.AM2012-1350

Abstract 2009: PKR induces apoptosis via PP2A activation and Bcl-2 dephosphorylation in IL-3 dependent murine bone marrow stem/progenitor cells

The Interferon-induced double-stranded RNA-activated protein kinase (PKR) was originally found to be activated by viral infection leading to inhibition of new protein synthesis and apoptosis. Recently multiple studies have reported decreased expression and function of PKR in leukemia cells, although the exact role of PKR in the process of oncogenesis remains unclear. Since leukemias are clonal disorders originating in a primitive pluripotent leukemic stem cell (LSC) which is regulated by multi-potential hematopoietic growth factors including interleukin-3 (IL-3). Thus, studying how PKR regulates apoptosis in IL-3 dependent (CD123+) pluripotent stem/progenitor cells is expected to reveal PKR's role in leukemia. PKR expression was either knocked down (by 78%) using a specific ShRNA or directly inhibited (57%) by treating cells with a specific PKR inhibitor. Results revealed that inhibition of PKR was associated with a reduction of PP2A activity, a 2.3 fold increase in Bcl-2 phosphorylation and inhibition of apoptosis following treatment with 100uM hydrogen peroxide for 48 hours. In addition, okadaic acid (an inhibitor of PP2A) had a similar effect to PKR inhibition on both Bcl-2 phosphorylation (1.74 fold increase) and stress-induced apoptosis. By contrast, treatment of cells with the PP2A activator, FTY 720, resulted in decreased Bcl-2 phosphorylation (by 2.24 fold) and enhanced apoptosis in response to treatment of cells with chemotherapy (etoposide or doxorubicin) or hydrogen peroxide. To test the role of PKR in growth factor- withdrawal mediated apoptosis in bone marrow stem/progenitor cells, CD123+(IL-3R[[Unsupported Character - Symbol Font ]]+) bone marrow cells from wild type, PKR transgenic (over-expressed) and PKR null(-/-) mice were exposed to different stresses including IL-3 deprivation or hydrogen peroxide. CD123+ cells isolated from PKR null mice had a significantly lower percentage of apoptosis while CD123+ cells from PKR transgenic mice had increased apoptosis compared to cells from wild type littermate mice. These results demonstrate that PKR negatively affects hematopoietic cell survival by enhancing apoptosis following stress in a mechanism that involves PP2A activation and Bcl2 dephosphorylation. Taken together these results may indicate that inhibition of PKR's pro-apoptotic function in bone marrow pluripotent stem/progenitor cells may contribute to tumorigenesis in hematopoietic malignancies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2009. doi:1538-7445.AM2012-2009

Screening outcomes in women over age 70 who self-refer in the NHSBSP in England

SETTING

The NHS breast screening programme (NHSBSP) in England currently invites women aged 50-70 every three years. Whilst screening is acknowledged as efficacious for women aged 50-69, several countries routinely invite women up to the age of 74. The NHSBSP in England is beginning to invite women up to the age of 73. Although the incidence of breast cancer increases with age, the possible benefits of screening older women must be balanced against shorter life expectancies and possible overdiagnosis. In England women can self-refer after reaching the invitation upper age limit.

OBJECTIVE

We examined the extent to which older women in England self-referred over a three-year period and studied the screening outcomes in these women.

METHODS

Routinely collected data from screening units in England were used to calculate screening performance measures for women who self-referred between 1 April 2005 and 31 March 2008. The tumour characteristics of all screen-detected cancers were examined by previous screening history and age group (71-74 and ≥75 years).

RESULTS

During the three-year period 139,910 women aged over 70 self-referred; equivalent to 4% of the female population aged over 70 having been screened. The majority of women who self-referred had been screened within the previous five years (76% of those aged 71-74 and 65% of those aged 75 or over). Approximately 4% of these women were recalled for assessment and cancer detection rates were similar in both age groups.

CONCLUSION

Only a small proportion of all women aged over 70 utilize the self-referral policy of the NHSBSP, and most such women are aged below 80.

The RAX/PACT-PKR stress response pathway promotes p53 sumoylation and activation, leading to G₁ arrest

Cellular stresses, including growth factor deprivation, inflammatory cytokines or viral infection promote RAX/PACT-dependent activation of the double-stranded RNA-dependent protein kinase, PKR, to phosphorylate eIF2α, resulting in translation inhibition and apoptosis. In addition, PKR has been reported to regulate p53, STAT1 and NFκB. Here, we report that RAX/PACT interacts with the SUMO E2 ligase Ubc9 to stimulate p53-Ubc9 association and reversible p53 sumoylation on lysine 386. In addition, expression of RAX/PACT in a variety of cell lines promotes p53 stability and activity to increase p53 target gene expression. Significantly, while the expression of RAX/PACT, PKR or p53 alone has little effect on the cell cycle of p53-null H1299 cells, co-expression of p53 with either RAX/PACT or PKR promotes a 25-35% increase of cells in G₁. In contrast, co-expression of RAX/PACT with the sumoylation-deficient p53(K386R) mutant or with the desumoylase SENP1 fails to induce such a G₁ arrest. Furthermore, co-expression of p53, RAX/PACT and the dominantnegative PKR(K296R) mutant inhibits RAX/PACT-induced, p53-dependent G₁ growth arrest and expression of RAX/PACT in pkr(+/+) but not pkr(-/-) MEF cells promotes p53 and p21 expression following gamma irradiation. Significantly, p53 stability is decreased in cells with reduced RAX/PACT or PKR following doxorubicin treatment, and expression of exogenous RAX/ PACT promotes phosphorylation of wild-type but not p53(K386R) on serine 392. Collectively, results indicate that, in response to stress, the RAX/PACT-PKR signaling pathway may inhibit p53 protein turnover by a sumoylation-dependent mechanism with promotion of p53 phosphorylation and translational activation leading to G₁ cell cycle arrest.

An observational study to evaluate the performance of units using two radiographers to read screening mammograms

AIM

To examine the performance of screening units in which a proportion of mammograms were double read using "non-discordant radiographer only (double) reading" (NDROR).

MATERIALS AND METHODS

NDROR was used by seven pilot units between 2006 and 2009, and six further units in 2009 only. There were 51 comparison units. Screening performance outcome measures were calculated, and logistic regression was used to compare performance between the pilot and comparison units.

RESULTS

Phase 1 pilot units read between on average 15 and 48% of mammograms per year using NDROR between 2006 and 2009 (median, 33%) and in 2009, phase 2 pilot units used NDROR to read between 4 and 77% of mammograms (median, 34%). The results showed an increase in recall rates in the phase 1 pilot units relative to the comparison units at both prevalent and incident screens (adjusted OR 1.09, 95% CI 1.05, 1.14; and adjusted OR 1.10, 95% CI 1.07, 1.14, respectively). There were also increases in the phase 2 pilot units relative to the comparison units; adjusted OR 1.08 (95% 1.00, 1.17) at prevalent screens, and adjusted OR 1.07 (95% CI 1.02, 1.14) at incident screens. There was no evidence to suggest a difference in cancer-detection rates between the pilot units and the comparison units.

CONCLUSIONS

Evidence from the present study suggests that recall rates may increase as a result of units using radiographers to double read a proportion of their mammograms. However, there is little evidence to suggest that NDROR, as practiced by the pilot units in the present study, is likely to have major impacts on performance in the UK National Health Service Breast Screening Programme (NHSBSP), particularly if it is fully supported and closely monitored (particularly recall rates).

Abstract 203: PKR is a doxorubicin sensitivity biomarker for breast cancer

Breast cancer is the second most frequently diagnosed cancer in U. S. women with >200,000 new cases estimated for 2010. Resistance to standard chemotherapy remains a significant clinical challenge. Thus, the identification of novel molecular biomarkers that predict response to treatment may improve therapeutic decision making and outcomes. Recently it has been reported that the level and activity of the dsRNA-dependent protein kinase, PKR, is increased in mammary carcinoma cell lines and more aggressive primary tumor specimens. Previously, our laboratory has determined that PKR is a key regulator of cell proliferation, apoptosis and transformation. PKR is activated by diverse cellular stresses including growth factor withdrawal from hematopoietic cells, inflammatory cytokine treatment or viral infection to initiate apoptosis presumably as a result eIF2α phosphorylation and inhibition of protein synthesis. However, activated PKR may also promote apoptosis by inhibiting Bcl2 phosphorylation and regulate cell proliferation by mechanisms dependent on p53, STAT1 or NF-κB. In order to gain insight into how PKR signaling may affect breast cancer development and sensitivity to chemotherapy, we measured the level of PKR in primary breast cancer (and paired, normal adjacent tissue) by immunohistochemical staining of a breast tumor tissue microarray containing 50 cases. Increased PKR staining was observed in all tumor types tested (infiltrating ductal carcinoma, mucinous adenocarcinoma, medullary carcinoma, Paget's disease, carcinosarcoma, cystosarcoma phyllodes and benign fibroadenoma) compared to normal adjacent tissue. Furthermore, elevated PKR expression directly correlates with increased tumor grade indicating a more aggressive phenotype. To determine whether PKR may be required for tumor response to doxorubicin, we employed a siRNA strategy to knock-down PKR by >75% in several breast cell lines. Interestingly, basal PKR activity is dramatically higher in those cell lines derived from human mammary carcinoma (i.e. MCF7 and T-47D) compared to a “nontransformed” mammary epithelial cell line (MCF10A). Furthermore, timecourse and dose response studies with doxorubicin, a frequently used and effective chemotherapy, revealed that cells with reduced PKR are significantly less sensitive to the drug compared to control siRNA cells with higher PKR. Interestingly, phosphorylation of eIF2α is unaffected by reduced PKR expression in MCF7 cells even with the highest dose of doxorubicin. This indicates that the mechanism by which PKR promotes doxorubicin sensitivity may be independent of eIF2α phosphorylation and protein synthesis inhibition. Together, these results suggest that increased PKR expression may be a useful biomarker for more aggressive breast tumors and for predicting response to doxorubicin treatment. Based on this model, aggressive tumors that do not display elevated PKR are predicted to be resistant to doxorubicin.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 203. doi:10.1158/1538-7445.AM2011-203

Interval cancers in the NHS breast cancer screening programme in England, Wales and Northern Ireland

BACKGROUND

The United Kingdom NHS Breast Screening Programme was established in 1988, and women aged between 50 and 70 are routinely invited at three yearly intervals. Expected United Kingdom interval cancer rates have been calculated previously, but this is the first publication from an exercise to collate individual-based interval cancer data at a national level.

METHODS

Interval cancer case ascertainment is achieved by the regular exchange of data between Regional Breast Screening Quality Assurance Reference Centres and Cancer Registries. The present analysis includes interval cancers identified in women screened between 1st April 1997 and 31st March 2003, who were aged between 50 and 64 at the time of their last routine screen.

RESULTS

In the periods >0-<12 months, 12-<24 months and 24-<36 months after a negative screen, we found overall interval cancer rates and regional ranges of 0.55 (0.43-0.76), 1.13 (0.92-1.47) and 1.22 (0.93-1.57) per 1000 women screened, respectively. Rates in the period 33-<36 months showed a decline, possibly associated with early re-screening or delayed presentation.

CONCLUSIONS

Interval cancer rates were higher than the expected rates in the 24-month period after a negative screen, but were similar to published results from other countries. Increases in background incidence may mean that the expected rates are underestimated. It is also possible that, as a result of incomplete case ascertainment, interval cancers rates were underestimated in some regions in which rates were less than the expected.

Abstract 1090: The RAX-PKR signaling axis enhances p53-mediated cell cycle arrest by a SUMOylation-dependent mechanism

Cellular stresses including IL-3 withdrawal from factor-dependent hematopoietic cells, inflammatory cytokine treatment or viral infection promote RAX-dependent activation of the double-stranded RNA dependent protein kinase PKR. Previously, our laboratory and others have demonstrated that upon activation PKR phosphorylates the alpha subunit of eIF2 to inhibit protein synthesis and initiate apoptosis. In addition, recent findings also indicate that PKR may regulate the transcription factors p53, STAT1 and NF-κB. Now, we report that stable or transient expression of RAX in a variety of cell lines induces increased protein stability and transcriptional activity of p53 to promote cell cycle arrest. Significantly, reporter assays demonstrate a RAX-dosage dependent increase in p53 activity by as much as 5 fold compared to control cells. Furthermore, western blotting and qPCR indicate that exogenous RAX expression promotes increased levels of the p53 downstream target p21 in normal but not in p53-/- MEF cells. Significantly, genotoxic damage by cisplatin or gamma irradiation is additive to RAX for upregulation of p53 and p21. Consistent with p53's effect on the cell cycle, expression of exogenous RAX promotes an almost 2-fold increase in the G1 population of MEF cells compared to control cells. Furthermore, while the expression of RAX, PKR or p53 alone has little effect on the cell cycle of H1299 cells, co-expression of p53 with either RAX or PKR promotes a 25 − 35% increase in the population of cells in G1. Importantly, RAX-induced p53 activation is PKR dependent since exogenous RAX expression fails to promote upregulation of p53 or p21 in pkr-/- cells even following gamma irradiation. Furthermore, RAX-dependent p53 activation can be inhibited by expression of the dominant negative RAX(S18A) mutant, and siRNA knockdown of endogenous RAX reduces p21 expression by 5 fold following stress. RAX expression does not affect p53-MDM2 interaction, p53 ubiquitination, or the level of p53 mRNA. Mechanistically, RAX interacts and co-localizes with the SUMO E2 conjugating enzyme, Ubc9, to promote p53 SUMOylation on lysine 386 in a RAX-dosage dependent manner. This is followed by G1 cell cycle arrest which can be reversed by the desumoylase SENP1. In addition, co-expression of RAX with the SUMOylation deficient p53(K386R) mutant inhibits RAX-induced, p53-dependent G1 growth arrest. Significantly, phosphorylation of p53(K386R) on serine 392 is also reduced compared to wt p53, indicating that SUMOylation of p53 may be necessary for p53 phosphorylation on serine 392. Taken together, our findings indicate that RAX-PKR stress signaling is a modulator of the p53 response, RAX-induced p53 SUMOylation may facilitate p53 tumor suppression activity, and functional crosstalk between RAX-PKR dependent translation inhibition and p53-dependent cell cycle arrest may occur in response to stress.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1090.

Gunshot wounds to the head: Gang- and non-gang-related injuries and outcomes

PRIMARY OBJECTIVE

This study examined the differences between gang and non-gang-related incidents of penetrative missile injuries in terms of demographics, motivation, intra-cranial pathology, transit time, injury time and clinical outcome.

RESEARCH DESIGN

Retrospective and prospective chart review.

METHODS AND PROCEDURES

Between 1985-1992, 349 patients with penetrating missile injuries to the brain presenting to LAC-USC were studied.

EXPERIMENTAL INTERVENTIONS

Inclusion criteria were implemented to keep the cohort as homogenous as possible. Patients excluded were those with multiple gunshot wounds, non-penetrating gunshot wounds to the head, systemic injuries and cases in which the motivation for the incident was unknown.

MAIN OUTCOMES AND RESULTS

Gang-related shooting slightly out-numbered non-gang-related incidents. Demographic analysis showed both a male and Hispanic predominance for both gang- and non-gang-related victims and significant differences in gender, race and age. Occipital entrance sites were more common in the gang-related vs temporal entrance sites in the non-gang-related. Mean transit time to the emergency department for gang-related shootings was less than non-gang-related shootings (24.4 vs 27.8 minutes). Most shooting incidents took place between 6pm and 3am. No difference between survival and outcome was noted between gang and non-gang victims.

CONCLUSIONS

Significant differences were found between gang- and non-gang-related shooting victims in terms of demographics, entrance site and transit time. No difference was found between injury time, survival and outcome between gang and non-gang populations.

RAX is required for fly neuronal development and mouse embryogenesis

RAX was originally discovered as the unique cellular activator for the dsRNA-dependent, interferon-inducible protein kinase PKR. Recent findings indicate that RAX is also a critical component of the RNA-induced silencing complex and a regulator of transcription. Here we report novel phenotypes for both fruit flies carrying a transposon insertion in the 5' UTR of dRax (independently identified as loqs/R3D1) and mice with a deletion of the entire Rax gene. In Drosophila we observe a high level of dRax expression in the developing nerve cord. Mutant fly embryos homozygous for the insertion dRax[f00791] display highly abnormal commissural axon structure of the CNS and 70% of the flies homozygous for the mutant allele die prior to adulthood. Surviving male flies have reduced fertility and female flies are sterile. Furthermore, these flies appear to have a severe defect in nervous system coordination or neuromuscular function resulting in significantly reduced locomotion. Mice were also generated that are heterozygous for a deletion of the entire Rax gene (exons 1-8). While mice that are heterozygous for the mutant allele are viable and appear normal, we are unable to obtain mice homozygous for this mutant allele. Furthermore, we have not observed any embryo obtained by mating heterozygous mice at either E3.5, 7, or 14 that is nullizygous for the Rax gene. Since Rax is expressed in preimplantation blastocysts, these data indicate that deletion of the entire Rax gene is embryonic lethal in mice at a preimplantation stage of development. Collectively, these findings in two different species illustrate the importance of RAX for embryonic development.

c-Myc and caspase-2 are involved in activating Bax during cytotoxic drug-induced apoptosis

Activation of Bax following diverse cytotoxic stress has been shown to be an essential gateway to mitochondrial dysfunction and activation of the intrinsic apoptotic pathway characterized by cytochrome c release with caspase-9/-3 activation. Interestingly, c-Myc has been reported to promote apoptosis by destabilizing mitochondrial integrity in a Bax-dependent manner. Stress-induced activation of caspase-2 may also induce permeabilization of mitochondria with activation of the intrinsic death pathway. To test whether c-Myc and caspase-2 cooperate to activate Bax and thereby mediate intrinsic apoptosis, small interfering RNA was used to efficiently knock down the expression of c-Myc, caspase-2, and Apaf-1, an activating component in the apoptosome, in two human cancer cell lines, lung adenocarcinoma A-549 and osteosarcoma U2-OS cells. Under conditions when the expression of endogenous c-Myc, caspase-2, or Apaf-1 is reduced 80-90%, cisplatin (or etoposide)-induced apoptosis is significantly decreased. Biochemical studies reveal that the expression of c-Myc and caspase-2 is crucial for cytochrome c release from mitochondria during cytotoxic stress and that Apaf-1 is only required following cytochrome c release to activate caspases-9/-3. Although knockdown of c-Myc or caspase-2 does not affect Bax expression, caspase-2 is important for cytosolic Bax to integrate into the outer mitochondrial membrane, and c-Myc is critical for oligomerization of Bax once integrated into the membrane.

Does the accuracy of single reading with CAD (computer-aided detection) compare with that of double reading?: A review of the literature

AIM

To examine current evidence to determine whether the accuracy of single reading with computed-aided detection (CAD) compares with that of double reading.

METHODS

We performed a literature review to identify studies where both protocols had been investigated and compared. We identified eight studies that compared single reading with CAD against double reading, of which six reported on comparisons of both sensitivity and specificity.

RESULTS

Of the six studies identified, three showed no differences in either sensitivity or specificity. One showed single reading with CAD had a higher sensitivity at the same specificity, another that single reading with CAD had a higher specificity at the same sensitivity. However, one study, in a real-life setting, showed that single reading with CAD had a higher sensitivity but a lower specificity.

CONCLUSION

As the majority of the studies were not in a real-life setting, used test sets, lacked sufficient training in the use of CAD and simulated double reading (using a protocol of recall if one suggests), current evidence is therefore limited as to the accuracy, in terms of sensitivity and specificity, of single reading with CAD in comparison with the most common practice in the UK of double reading using a protocol of consensus or arbitration.

The effect of data quality at the time of introduction of population-based screening on the estimate of programme impact using surrogate outcome measures

OBJECTIVE

The aim of this study was to examine the availability and quality of surrogate outcome measure data to enable the evaluation of the breast screening programme. As the observed effect on mortality of a screening programme occurs many years after the introduction of screening, surrogate outcome measures offer an attractive alternative, allowing estimates of the effect to be calculated earlier.

METHODS

The exercise was undertaken by the Oxford Cancer Intelligence Unit and the Cancer Screening Evaluation Unit in collaboration with cancer registries in England, Scotland and Wales.

RESULTS

The conclusion of the exercise was that, in general, the available data quality was insufficient to allow a precise estimate of the overall mortality reduction from breast screening to be made using surrogate measures.

CONCLUSIONS

When a screening programme is started, it is vital that forward planning is undertaken to ensure that the necessary information is ready to be collected before the start of the programme. The use of surrogate measures is dependent on high-quality data in the uninvited group of women (pre-screening or from a staggered start over areas), and improving data quality over time after the start of the programme is of very limited value for a surrogate measures approach. The collection of appropriate high-quality information before the programme starts is, therefore, critical to measuring the success of the programme. Cancer registries and staff within the screening programme need to be ready to collect the appropriate data before the introduction of a screening programme. The exercise undertaken therefore has important implications where new screening programmes are being considered.

RAX, the PKR activator, sensitizes cells to inflammatory cytokines, serum withdrawal, chemotherapy, and viral infection

While the interferon (IFN)-inducible double-stranded RNA (dsRNA)-dependent protein kinase PKR is reported to initiate apoptosis in some instances, the mechanism by which diverse stress stimuli activate PKR remains unknown. Now we report that RAX, the only known cellular activator for PKR, initiates PKR activation in response to a broad range of stresses including serum deprivation, cytotoxic cytokine or chemotherapy treatment, or viral infection. Thus, knock-down of RAX expression by 80% using small interfering RNA (siRNA) prevents IFNgamma/tumor necrosis factor alpha (TNFalpha)-induced PKR activation and eIF2alpha phosphorylation, IkappaB degradation, IRF-1 expression, and STAT1 phosphorylation, resulting in enhanced murine embryonic fibroblast (MEF) cell survival. In contrast, expression of exogenous RAX, but not of the nonphosphorylatable, dominant-negative RAX(S18A) mutant, sensitizes cells to IFNgamma/TNFalpha, mitomycin C (MMC), or serum deprivation in association with increased PKR activity and apoptosis. Furthermore, RAX(S18A) expression in Fanconi anemia complementation group C-null MEF cells not only prevents PKR activation but also blocks hypersensitivity to IFNgamma/TNFalpha or mitomycin C that results in enhanced apoptosis. In addition, reduced RAX expression facilitates productive viral infection with vesicular stomatitis virus (VSV) and promotes anchorage-independent colony growth of MEF cells. Collectively, these data indicate that RAX may function as a negative regulator of growth that is required to activate PKR in response to a broad range of apoptosis-inducing stress.