Prospective derivation of a living organoid biobank of colorectal cancer patients.

In Rspondin-based 3D cultures, Lgr5 stem cells from multiple organs form ever-expanding epithelial organoids that retain their tissue identity. We report the establishment of tumor organoid cultures from 20 consecutive colorectal carcinoma (CRC) patients. For most, organoids were also generated from adjacent normal tissue. Organoids closely recapitulate several properties of the original tumor. The spectrum of genetic changes within the "living biobank" agrees well with previous large-scale mutational analyses of CRC. Gene expression analysis indicates that the major CRC molecular subtypes are represented. Tumor organoids are amenable to high-throughput drug screens allowing detection of gene-drug associations. As an example, a single organoid culture was exquisitely sensitive to Wnt secretion (porcupine) inhibitors and carried a mutation in the negative Wnt feedback regulator RNF43, rather than in APC. Organoid technology may fill the gap between cancer genetics and patient trials, complement cell-line- and xenograft-based drug studies, and allow personalized therapy design. PAPERCLIP.

Single-cell RNA-seq supports a developmental hierarchy in human oligodendroglioma.

Although human tumours are shaped by the genetic evolution of cancer cells, evidence also suggests that they display hierarchies related to developmental pathways and epigenetic programs in which cancer stem cells (CSCs) can drive tumour growth and give rise to differentiated progeny. Yet, unbiased evidence for CSCs in solid human malignancies remains elusive. Here we profile 4,347 single cells from six IDH1 or IDH2 mutant human oligodendrogliomas by RNA sequencing (RNA-seq) and reconstruct their developmental programs from genome-wide expression signatures. We infer that most cancer cells are differentiated along two specialized glial programs, whereas a rare subpopulation of cells is undifferentiated and associated with a neural stem cell expression program. Cells with expression signatures for proliferation are highly enriched in this rare subpopulation, consistent with a model in which CSCs are primarily responsible for fuelling the growth of oligodendroglioma in humans. Analysis of copy number variation (CNV) shows that distinct CNV sub-clones within tumours display similar cellular hierarchies, suggesting that the architecture of oligodendroglioma is primarily dictated by developmental programs. Subclonal point mutation analysis supports a similar model, although a full phylogenetic tree would be required to definitively determine the effect of genetic evolution on the inferred hierarchies. Our single-cell analyses provide insight into the cellular architecture of oligodendrogliomas at single-cell resolution and support the cancer stem cell model, with substantial implications for disease management.

Chromothripsis from DNA damage in micronuclei.

Genome sequencing has uncovered a new mutational phenomenon in cancer and congenital disorders called chromothripsis. Chromothripsis is characterized by extensive genomic rearrangements and an oscillating pattern of DNA copy number levels, all curiously restricted to one or a few chromosomes. The mechanism for chromothripsis is unknown, but we previously proposed that it could occur through the physical isolation of chromosomes in aberrant nuclear structures called micronuclei. Here, using a combination of live cell imaging and single-cell genome sequencing, we demonstrate that micronucleus formation can indeed generate a spectrum of genomic rearrangements, some of which recapitulate all known features of chromothripsis. These events are restricted to the mis-segregated chromosome and occur within one cell division. We demonstrate that the mechanism for chromothripsis can involve the fragmentation and subsequent reassembly of a single chromatid from a micronucleus. Collectively, these experiments establish a new mutational process of which chromothripsis is one extreme outcome.

Genotype-targeted local therapy of glioma.

Aggressive neurosurgical resection to achieve sustained local control is essential for prolonging survival in patients with lower-grade glioma. However, progression in many of these patients is characterized by local regrowth. Most lower-grade gliomas harbor isocitrate dehydrogenase 1 (IDH1) or IDH2 mutations, which sensitize to metabolism-altering agents. To improve local control of IDH mutant gliomas while avoiding systemic toxicity associated with metabolic therapies, we developed a precision intraoperative treatment that couples a rapid multiplexed genotyping tool with a sustained release microparticle (MP) drug delivery system containing an IDH-directed nicotinamide phosphoribosyltransferase (NAMPT) inhibitor (GMX-1778). We validated our genetic diagnostic tool on clinically annotated tumor specimens. GMX-1778 MPs showed mutant IDH genotype-specific toxicity in vitro and in vivo, inducing regression of orthotopic IDH mutant glioma murine models. Our strategy enables immediate intraoperative genotyping and local application of a genotype-specific treatment in surgical scenarios where local tumor control is paramount and systemic toxicity is therapeutically limiting.

Integrated cistromic and expression analysis of amplified NKX2-1 in lung adenocarcinoma identifies LMO3 as a functional transcriptional target.

The NKX2-1 transcription factor, a regulator of normal lung development, is the most significantly amplified gene in human lung adenocarcinoma. To study the transcriptional impact of NKX2-1 amplification, we generated an expression signature associated with NKX2-1 amplification in human lung adenocarcinoma and analyzed DNA-binding sites of NKX2-1 by genome-wide chromatin immunoprecipitation. Integration of these expression and cistromic analyses identified LMO3, itself encoding a transcription regulator, as a candidate direct transcriptional target of NKX2-1. Further cistromic and overexpression analyses indicated that NKX2-1 can cooperate with the forkhead box transcription factor FOXA1 to regulate LMO3 gene expression. RNAi analysis of NKX2-1-amplified cells compared with nonamplified cells demonstrated that LMO3 mediates cell survival downstream from NKX2-1. Our findings provide new insight into the transcriptional regulatory network of NKX2-1 and suggest that LMO3 is a transcriptional signal transducer in NKX2-1-amplified lung adenocarcinomas.

Integrated single-cell genetic and transcriptional analysis suggests novel drivers of chronic lymphocytic leukemia.

Intra-tumoral genetic heterogeneity has been characterized across cancers by genome sequencing of bulk tumors, including chronic lymphocytic leukemia (CLL). In order to more accurately identify subclones, define phylogenetic relationships, and probe genotype-phenotype relationships, we developed methods for targeted mutation detection in DNA and RNA isolated from thousands of single cells from five CLL samples. By clearly resolving phylogenic relationships, we uncovered mutated LCP1 and WNK1 as novel CLL drivers, supported by functional evidence demonstrating their impact on CLL pathways. Integrative analysis of somatic mutations with transcriptional states prompts the idea that convergent evolution generates phenotypically similar cells in distinct genetic branches, thus creating a cohesive expression profile in each CLL sample despite the presence of genetic heterogeneity. Our study highlights the potential for single-cell RNA-based targeted analysis to sensitively determine transcriptional and mutational profiles of individual cancer cells, leading to increased understanding of driving events in malignancy.

Pharmacokinetics and derivation of an anticancer dosing regimen for the novel anti-cancer agent isobutyl-deoxynyboquinone (IB-DNQ), a NQO1 bioactivatable molecule, in the domestic felid species.

Isobutyl-deoxynyboquinone (IB-DNQ) is a selective substrate for NAD(P)H:quinone oxidoreductase (NQO1), an enzyme overexpressed in many solid tumors. Following activation by NQO1, IB-DNQ participates in a catalytic futile reduction/reoxidation cycle with consequent toxic reactive oxygen species generation within the tumor microenvironment. To elucidate the potential of IB-DNQ to serve as a novel anticancer agent, in vitro studies coupled with in vivo pharmacokinetic and toxicologic investigations in the domestic felid species were conducted to investigate the tractability of IB-DNQ as a translationally applicable anticancer agent. First, using feline oral squamous cell carcinoma (OSCC) as a comparative cancer model, expressions of NQO1 were characterized in not only human, but also feline OSCC tissue microarrays. Second, IB-DNQ mediated cytotoxicity in three immortalized feline OSCC cell lines were studied under dose-dependent and sequential exposure conditions. Third, the feasibility of administering IB-DNQ at doses predicted to achieve cytotoxic plasma concentrations and biologically relevant durations of exposure were investigated through pharmacokinetic and tolerability studies in healthy research felines. Intravenous administration of IB-DNQ at 1.0-2.0 mg/kg achieved peak plasma concentrations and durations of exposure reaching or exceeding predicted in vitro cytotoxic concentrations. Clinical adverse side effects including ptyalism and tachypnea exhibited during and post-IV infusion of IB-DNQ were transient and tolerable. Additionally, IB-DNQ administration did not produce acute or delayed-onset unacceptable hematologic, non-hematologic, or off-target oxidative toxicities. Collectively, the findings reported here within provide important safety and pharmacokinetic data to support the continued development of IB-DNQ as a novel anticancer strategy for NQO1 expressing cancers.

The tumor suppressor Cdc73 functionally associates with CPSF and CstF 3' mRNA processing factors.

The CDC73 tumor suppressor gene is mutationally inactivated in hereditary and sporadic parathyroid tumors. Its product, the Cdc73 protein, is a component of the RNA polymerase II and chromatin-associated human Paf1 complex (Paf1C). Here, we show that Cdc73 physically associates with the cleavage and polyadenylation specificity factor (CPSF) and cleavage stimulation factor (CstF) complexes that are required for the maturation of mRNA 3' ends in the cell nucleus. Immunodepletion experiments indicate that the Cdc73-CPSF-CstF complex is necessary for 3' mRNA processing in vitro. Microarray analysis of CDC73 siRNA-treated cells revealed INTS6, a gene encoding a subunit of the Integrator complex, as an in vivo Cdc73 target. Cdc73 depletion by siRNA resulted in decreased INTS6 mRNA abundance, and decreased association of CPSF and CstF subunits with the INTS6 locus. Our results suggest that Cdc73 facilitates association of 3' mRNA processing factors with actively-transcribed chromatin and support the importance of links between tumor suppression and mRNA maturation.

Allelic variation in class I HLA determines CD8+ T cell repertoire shape and cross-reactive memory responses to SARS-CoV-2.

Effective presentation of antigens by human leukocyte antigen (HLA) class I molecules to CD8+ T cells is required for viral elimination and generation of long-term immunological memory. In this study, we applied a single-cell, multiomic technology to generate a unified ex vivo characterization of the CD8+ T cell response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) across four major HLA class I alleles. We found that HLA genotype conditions key features of epitope specificity, TCRα/ß sequence diversity, and the utilization of pre-existing SARS-CoV-2-reactive memory T cell pools. Single-cell transcriptomics revealed functionally diverse T cell phenotypes of SARS-CoV-2-reactive T cells, associated with both disease stage and epitope specificity. Our results show that HLA variations notably influence the CD8+ T cell repertoire shape and utilization of immune recall upon SARS-CoV-2 infection.

Utilizing feline oral squamous cell carcinoma patients to develop NQO1-targeted therapy.

Developing effective therapies for the treatment of advanced head-and-neck squamous cell carcinoma (HNSCC) remains a major challenge, and there is a limited landscape of effective targeted therapies on the horizon. NAD(P)H:quinone oxidoreductase 1 (NQO1) is a 2-electron reductase that is overexpressed in HNSCC and presents as a promising target for the treatment of HNSCC. Current NQO1-targeted drugs are hindered by their poor oxidative tolerability in human patients, underscoring a need for better preclinical screening for oxidative toxicities for NQO1-bioactivated small molecules. Herein, we describe our work to include felines and feline oral squamous cell carcinoma (FOSCC) patients in the preclinical assessment process to prioritize lead compounds with increased tolerability and efficacy prior to full human translation. Specifically, our data demonstrate that IB-DNQ, an NQO1-targeted small molecule, is well-tolerated in FOSCC patients and shows promising initial efficacy against FOSCC tumors in proof-of-concept single agent and radiotherapy combination cohorts. Furthermore, FOSCC tumors are amenable to evaluating a variety of target-inducible couplet hypotheses, evidenced herein with modulation of NQO1 levels with palliative radiotherapy. The use of felines and their naturally-occurring tumors provide an intriguing, often underutilized tool for preclinical drug development for NQO1-targeted approaches and has broader applications for the evaluation of other anticancer strategies.

Chromatin Looping Shapes KLF5-Dependent Transcriptional Programs in Human Epithelial Cancers.

Activation of transcription factors is a key driver event in cancer. We and others have recently reported that the Krüppel-like transcription factor KLF5 is activated in multiple epithelial cancer types including squamous cancer and gastrointestinal adenocarcinoma, yet the functional consequences and the underlying mechanisms of this activation remain largely unknown. Here we demonstrate that activation of KLF5 results in strongly selective KLF5 dependency for these cancer types. KLF5 bound lineage-specific regulatory elements and activated gene expression programs essential to cancer cells. HiChIP analysis revealed that multiple distal KLF5 binding events cluster and synergize to activate individual target genes. Immunoprecipitation-mass spectrometry assays showed that KLF5 interacts with other transcription factors such as TP63 and YAP1, as well as the CBP/EP300 acetyltransferase complex. Furthermore, KLF5 guided the CBP/EP300 complex to increase acetylation of H3K27, which in turn enhanced recruitment of the bromodomain protein BRD4 to chromatin. The 3D chromatin architecture aggregated KLF5-dependent BRD4 binding to activate polymerase II elongation at KLF5 target genes, which conferred a transcriptional vulnerability to proteolysis-targeting chimera-induced degradation of BRD4. Our study demonstrates that KLF5 plays an essential role in multiple epithelial cancers by activating cancer-related genes through 3D chromatin loops, providing an evidence-based rationale for targeting the KLF5 pathway. SIGNIFICANCE: An integrative 3D genomics methodology delineates mechanisms underlying the function of KLF5 in multiple epithelial cancers and suggests potential strategies to target cancers with aberrantly activated KLF5.

Multi-Omics Analysis Identifies MGA as a Negative Regulator of the MYC Pathway in Lung Adenocarcinoma.

Genomic analysis of lung adenocarcinomas has revealed that the MGA gene, which encodes a heterodimeric partner of the MYC-interacting protein MAX, is significantly mutated or deleted in lung adenocarcinomas. Most of the mutations are loss of function for MGA, suggesting that MGA may act as a tumor suppressor. Here, we characterize both the molecular and cellular role of MGA in lung adenocarcinomas and illustrate its functional relevance in the MYC pathway. Although MGA and MYC interact with the same binding partner, MAX, and recognize the same E-box DNA motif, we show that the molecular function of MGA appears to be antagonistic to that of MYC. Using mass spectrometry-based affinity proteomics, we demonstrate that MGA interacts with a noncanonical PCGF6-PRC1 complex containing MAX and E2F6 that is involved in gene repression, while MYC is not part of this MGA complex, in agreement with previous studies describing the interactomes of E2F6 and PCGF6. Chromatin immunoprecipitation-sequencing and RNA sequencing assays show that MGA binds to and represses genes that are bound and activated by MYC. In addition, we show that, as opposed to the MYC oncoprotein, MGA acts as a negative regulator for cancer cell proliferation. Our study defines a novel MYC/MAX/MGA pathway, in which MYC and MGA play opposite roles in protein interaction, transcriptional regulation, and cellular proliferation. IMPLICATIONS: This study expands the range of key cancer-associated genes whose dysregulation is functionally equivalent to MYC activation and places MYC within a linear pathway analogous to cell-cycle or receptor tyrosine kinase/RAS/RAF pathways in lung adenocarcinomas.

Small-molecule targeting of brachyury transcription factor addiction in chordoma.

Chordoma is a primary bone cancer with no approved therapy1. The identification of therapeutic targets in this disease has been challenging due to the infrequent occurrence of clinically actionable somatic mutations in chordoma tumors2,3. Here we describe the discovery of therapeutically targetable chordoma dependencies via genome-scale CRISPR-Cas9 screening and focused small-molecule sensitivity profiling. These systematic approaches reveal that the developmental transcription factor T (brachyury; TBXT) is the top selectively essential gene in chordoma, and that transcriptional cyclin-dependent kinase (CDK) inhibitors targeting CDK7/12/13 and CDK9 potently suppress chordoma cell proliferation. In other cancer types, transcriptional CDK inhibitors have been observed to downregulate highly expressed, enhancer-associated oncogenic transcription factors4,5. In chordoma, we find that T is associated with a 1.5-Mb region containing 'super-enhancers' and is the most highly expressed super-enhancer-associated transcription factor. Notably, transcriptional CDK inhibition leads to preferential and concentration-dependent downregulation of cellular brachyury protein levels in all models tested. In vivo, CDK7/12/13-inhibitor treatment substantially reduces tumor growth. Together, these data demonstrate small-molecule targeting of brachyury transcription factor addiction in chordoma, identify a mechanism of T gene regulation that underlies this therapeutic strategy, and provide a blueprint for applying systematic genetic and chemical screening approaches to discover vulnerabilities in genomically quiet cancers.

Somatic Superenhancer Duplications and Hotspot Mutations Lead to Oncogenic Activation of the KLF5 Transcription Factor.

The Krüppel-like family of transcription factors plays critical roles in human development and is associated with cancer pathogenesis. Krüppel-like factor 5 gene (KLF5) has been shown to promote cancer cell proliferation and tumorigenesis and to be genomically amplified in cancer cells. We recently reported that the KLF5 gene is also subject to other types of somatic coding and noncoding genomic alterations in diverse cancer types. Here, we show that these alterations activate KLF5 by three distinct mechanisms: (i) Focal amplification of superenhancers activates KLF5 expression in squamous cell carcinomas; (ii) Missense mutations disrupt KLF5-FBXW7 interactions to increase KLF5 protein stability in colorectal cancer; (iii) Cancer type-specific hotspot mutations within a zinc-finger DNA binding domain of KLF5 change its DNA binding specificity and reshape cellular transcription. Utilizing data from CRISPR/Cas9 gene knockout screening, we reveal that cancer cells with KLF5 overexpression are dependent on KLF5 for their proliferation, suggesting KLF5 as a putative therapeutic target.Significance: Our observations, together with previous studies that identified oncogenic properties of KLF5, establish the importance of KLF5 activation in human cancers, delineate the varied genomic mechanisms underlying this occurrence, and nominate KLF5 as a putative target for therapeutic intervention in cancer. Cancer Discov; 8(1); 108-25. ©2017 AACR.This article is highlighted in the In This Issue feature, p. 1.

Scalable whole-exome sequencing of cell-free DNA reveals high concordance with metastatic tumors.

Whole-exome sequencing of cell-free DNA (cfDNA) could enable comprehensive profiling of tumors from blood but the genome-wide concordance between cfDNA and tumor biopsies is uncertain. Here we report ichorCNA, software that quantifies tumor content in cfDNA from 0.1× coverage whole-genome sequencing data without prior knowledge of tumor mutations. We apply ichorCNA to 1439 blood samples from 520 patients with metastatic prostate or breast cancers. In the earliest tested sample for each patient, 34% of patients have ≥10% tumor-derived cfDNA, sufficient for standard coverage whole-exome sequencing. Using whole-exome sequencing, we validate the concordance of clonal somatic mutations (88%), copy number alterations (80%), mutational signatures, and neoantigens between cfDNA and matched tumor biopsies from 41 patients with ≥10% cfDNA tumor content. In summary, we provide methods to identify patients eligible for comprehensive cfDNA profiling, revealing its applicability to many patients, and demonstrate high concordance of cfDNA and metastatic tumor whole-exome sequencing.

Kmt2a cooperates with menin to suppress tumorigenesis in mouse pancreatic islets.

The reported incidence of pancreatic neuroendocrine tumors (PanNETs) has increased, due in large part to improvements in detection and awareness. However, therapeutic options are limited and a critical need exists for understanding a more thorough characterization of the molecular pathology underlying this disease. The Men1 knockout mouse model recapitulates the early stage of human PanNET development and can serve as a foundation for the development of advanced mouse models that are necessary for preclinical testing. Menin, the product of the MEN1 gene, has been shown to physically interact with the KMT2A and KMT2B histone methyltransferases. Both the KMT2A and MEN1 genes are located on chromosome 11q, which frequently undergoes loss of heterozygosity (LOH) in PanNETs. We report herein that inactivation of Kmt2a in Men1-deficient mice accelerated pancreatic islet tumorigenesis and shortened the average life span. Increases in cell proliferation were observed in mouse pancreatic islet tumors upon inactivation of both Kmt2a and Men1. The Kmt2a/Men1 double knockout mouse model can be used as a mouse model to study advanced PanNETs.

Identification of focally amplified lineage-specific super-enhancers in human epithelial cancers.

Whole-genome analysis approaches are identifying recurrent cancer-associated somatic alterations in noncoding DNA regions. We combined somatic copy number analysis of 12 tumor types with tissue-specific epigenetic profiling to identify significant regions of focal amplification harboring super-enhancers. Copy number gains of noncoding regions harboring super-enhancers near KLF5, USP12, PARD6B and MYC are associated with overexpression of these cancer-related genes. We show that two distinct focal amplifications of super-enhancers 3' to MYC in lung adenocarcinoma (MYC-LASE) and endometrial carcinoma (MYC-ECSE) are physically associated with the MYC promoter and correlate with MYC overexpression. CRISPR/Cas9-mediated repression or deletion of a constituent enhancer within the MYC-LASE region led to significant reductions in the expression of MYC and its target genes and to the impairment of anchorage-independent and clonogenic growth, consistent with an oncogenic function. Our results suggest that genomic amplification of super-enhancers represents a common mechanism to activate cancer driver genes in multiple cancer types.

Integrated genomic approaches identify upregulation of SCRN1 as a novel mechanism associated with acquired resistance to erlotinib in PC9 cells harboring oncogenic EGFR mutation.

Therapies targeting the tyrosine kinase activity of Epidermal Growth Factor Receptor (EGFR) have been proven to be effective in treating a subset of non-small cell lung cancer (NSCLC) patients harboring activating EGFR mutations. Inevitably these patients develop resistance to the EGFR-targeted tyrosine kinase inhibitors (TKIs). Here, we performed integrated genomic analyses using an in vitro system to uncover alternative genomic mechanisms responsible for acquired resistance to EGFR-TKIs. Specifically, we identified 80 genes whose expression is significantly increased in the erlotinib-resistant clones. RNAi-based systematic synthetic lethal screening of these candidate genes revealed that suppression of one upregulated transcript, SCRN1, a secernin family member, restores sensitivity to erlotinib by enhancing inhibition of PI3K/AKT signaling pathway. Furthermore, immunohistochemical analysis revealed increased levels of SCRN1 in 5 of 11 lung tumor specimens from EGFR-TKIs resistant patients. Taken together, we propose that upregulation of SCRN1 is an additional mechanism associated with acquired resistance to EGFR-TKIs and that its suppression serves as a novel therapeutic strategy to overcome drug resistance in these patients.

Constitutive asymmetric dimerization drives oncogenic activation of epidermal growth factor receptor carboxyl-terminal deletion mutants.

Genomic alterations targeting the Epidermal Growth Factor Receptor (EGFR) gene have been strongly associated with cancer pathogenesis. The clinical effectiveness of EGFR targeted therapies, including small molecules directed against the kinase domain such as gefitinib, erlotinib and afatinib, have been proven successful in treating non-small cell lung cancer patients with tumors harboring EGFR kinase domain mutations. Recent large-scale genomic studies in glioblastoma and lung cancer have identified an additional class of oncogenic mutations caused by the intragenic deletion of carboxy-terminal coding regions. Here, we report that combinations of exonic deletions of exon 25 to 28 lead to the oncogenic activation of EGF receptor in the absence of ligand and consequent cellular transformation, indicating a significant role of C-terminal domain in modulating EGFR activation. Furthermore, we show that the oncogenic activity of the resulting C-terminal deletion mutants are efficiently inhibited by EGFR-targeted drugs including erlotinib, afatinib, dacomitinib as well as cetuximab, expanding the therapeutic rationale of cancer genome-based EGFR targeted approaches. Finally, in vivo and in vitro preclinical studies demonstrate that constitutive asymmetric dimerization in mutant EGFR is a key mechanism for oncogenic activation and tumorigenesis by C-terminal deletion mutants. Therefore, our data provide compelling evidence for oncogenic activation of C-terminal deletion mutants at the molecular level and we propose that C-terminal deletion status of EGFR can be considered as a potential genomic marker for EGFR-targeted therapy.

Dynamic epigenetic regulation by menin during pancreatic islet tumor formation.

UNLABELLED: The tumor suppressor gene MEN1 is frequently mutated in sporadic pancreatic neuroendocrine tumors (PanNET) and is responsible for the familial multiple endocrine neoplasia type 1 (MEN-1) cancer syndrome. Menin, the protein product of MEN1, associates with the histone methyltransferases (HMT) MLL1 (KMT2A) and MLL4 (KMT2B) to form menin-HMT complexes in both human and mouse model systems. To elucidate the role of methylation of histone H3 at lysine 4 (H3K4) mediated by menin-HMT complexes during PanNET formation, genome-wide histone H3 lysine 4 trimethylation (H3K4me3) signals were mapped in pancreatic islets using unbiased chromatin immunoprecipitation coupled with next-generation sequencing (ChIP-seq). Integrative analysis of gene expression profiles and histone H3K4me3 levels identified a number of transcripts and target genes dependent on menin. In the absence of Men1, histone H3K27me3 levels are enriched, with a concomitant decrease in H3K4me3 within the promoters of these target genes. In particular, expression of the insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2) gene is subject to dynamic epigenetic regulation by Men1-dependent histone modification in a time-dependent manner. Decreased expression of IGF2BP2 in Men1-deficient hyperplastic pancreatic islets is partially reversed by ablation of RBP2 (KDM5A), a histone H3K4-specific demethylase of the jumonji, AT-rich interactive domain 1 (JARID1) family. Taken together, these data demonstrate that loss of Men1 in pancreatic islet cells alters the epigenetic landscape of its target genes. IMPLICATIONS: Epigenetic profiling and gene expression analysis in Men1-deficient pancreatic islet cells reveals vital insight into the molecular events that occur during the progression of pancreatic islet tumorigenesis.