KLF5 and p53 comprise an incoherent feed-forward loop directing cell-fate decisions following stress.

In response to stress, cells make a critical decision to arrest or undergo apoptosis, mediated in large part by the tumor suppressor p53. Yet the mechanisms of these cell fate decisions remain largely unknown, particularly in normal cells. Here, we define an incoherent feed-forward loop in non-transformed human squamous epithelial cells involving p53 and the zinc-finger transcription factor KLF5 that dictates responses to differing levels of cellular stress from UV irradiation or oxidative stress. In normal unstressed human squamous epithelial cells, KLF5 complexes with SIN3A and HDAC2 repress TP53, allowing cells to proliferate. With moderate stress, this complex is disrupted, and TP53 is induced; KLF5 then acts as a molecular switch for p53 function by transactivating AKT1 and AKT3, which direct cells toward survival. By contrast, severe stress results in KLF5 loss, such that AKT1 and AKT3 are not induced, and cells preferentially undergo apoptosis. Thus, in human squamous epithelial cells, KLF5 gates the response to UV or oxidative stress to determine the p53 output of growth arrest or apoptosis.

A GATA6-centred gene regulatory network involving HNFs and ΔNp63 controls plasticity and immune escape in pancreatic cancer.

OBJECTIVE: Molecular taxonomy of tumours is the foundation of personalised medicine and is becoming of paramount importance for therapeutic purposes. Four transcriptomics-based classification systems of pancreatic ductal adenocarcinoma (PDAC) exist, which consistently identified a subtype of highly aggressive PDACs with basal-like features, including ΔNp63 expression and loss of the epithelial master regulator GATA6. We investigated the precise molecular events driving PDAC progression and the emergence of the basal programme. DESIGN: We combined the analysis of patient-derived transcriptomics datasets and tissue samples with mechanistic experiments using a novel dual-recombinase mouse model for Gata6 deletion at late stages of KRasG12D-driven pancreatic tumorigenesis (Gata6LateKO). RESULTS: This comprehensive human-to-mouse approach showed that GATA6 loss is necessary, but not sufficient, for the expression of ΔNp63 and the basal programme in patients and in mice. The concomitant loss of HNF1A and HNF4A, likely through epigenetic silencing, is required for the full phenotype switch. Moreover, Gata6 deletion in mice dramatically increased the metastatic rate, with a propensity for lung metastases. Through RNA-Seq analysis of primary cells isolated from mouse tumours, we show that Gata6 inhibits tumour cell plasticity and immune evasion, consistent with patient-derived data, suggesting that GATA6 works as a barrier for acquiring the fully developed basal and metastatic phenotype. CONCLUSIONS: Our work provides both a mechanistic molecular link between the basal phenotype and metastasis and a valuable preclinical tool to investigate the most aggressive subtype of PDAC. These data, therefore, are important for understanding the pathobiological features underlying the heterogeneity of pancreatic cancer in both mice and human.

Modeling post-translational modifications and cancer-associated mutations that impact the heterochromatin protein 1α-importin α heterodimers.

Heterochromatin protein 1α (HP1α) is a protein that mediates cancer-associated processes in the cell nucleus. Proteomic experiments, reported here, demonstrate that HP1α complexes with importin α (IMPα), a protein necessary for its nuclear transport. This data is congruent with Simple Linear Motif (SLiM) analyses that identify an IMPα-binding motif within the linker that joins the two globular domains of this protein. Using molecular modeling and dynamics simulations, we develop a model of the IMPα-HP1α complex and investigate the impact of phosphorylation and genomic variants on their interaction. We demonstrate that phosphorylation of the HP1α linker likely regulates its association with IMPα, which has implications for HP1α access to the nucleus, where it functions. Cancer-associated genomic variants do not abolish the interaction of HP1α but instead lead to rearrangements where the variant proteins maintain interaction with IMPα, but with less specificity. Combined, this new mechanistic insight bears biochemical, cell biological, and biomedical relevance.

Aurora kinase B-phosphorylated HP1α functions in chromosomal instability.

Heterochromatin Protein 1 α (HP1α) associates with members of the chromosome passenger complex (CPC) during mitosis, at centromeres where it is required for full Aurora Kinase B (AURKB) activity. Conversely, recent reports have identified AURKB as the major kinase responsible for phosphorylation of HP1α at Serine 92 (S92) during mitosis. Thus, the current study was designed to better understand the functional role of this posttranslationally modified form of HP1α. We find that S92-phosphorylated HP1α is generated in cells at early prophase, localizes to centromeres, and associates with regulators of chromosome stability, such as Inner Centromere Protein, INCENP. In mouse embryonic fibroblasts, HP1α knockout alone or reconstituted with a non-phosphorylatable (S92A) HP1α mutant results in mitotic chromosomal instability characterized by the formation of anaphase/telophase chromatin bridges and micronuclei. These effects are rescued by exogenous expression of wild type HP1α or a phosphomimetic (S92D) variant. Thus, the results from the current study extend our knowledge of the role of HP1α in chromosomal stability during mitosis.

Co-occurrence of a maternally inherited DNMT3A duplication and a paternally inherited pathogenic variant in EZH2 in a child with growth retardation and severe short stature: atypical Weaver syndrome or evidence of a DNMT3A dosage effect?

Overgrowth syndromes are a clinically heterogeneous group of disorders characterized by localized or generalized tissue overgrowth and varying degrees of developmental and intellectual disability. An expanding list of genes associated with overgrowth syndromes include the histone methyltransferase genes EZH2 and NSD1, which cause Weaver and Sotos syndrome, respectively, and the DNA methyltransferase (DNMT3A) gene that results in Tatton-Brown-Rahman syndrome (TBRS). Here, we describe a 5-year-old female with a paternally inherited pathogenic mutation in EZH2 (c.2050C>T, p.Arg684Cys) and a maternally inherited 505-kb duplication of uncertain significance at 2p23.3 (encompassing five genes, including DNMT3A) who presented with intrauterine growth restriction, slow postnatal growth, short stature, hypotonia, developmental delay, and neuroblastoma diagnosed at the age of 8 mo. Her father had tall stature, dysmorphic facial features, and intellectual disability consistent with Weaver syndrome, whereas her mother had short stature, cognitive delays, and chronic nonprogressive leukocytosis. It has been previously shown that EZH2 directly controls DNA methylation through physical association with DNMTs, including DNMT3A, with concomitant H3K27 methylation and CpG promoter methylation leading to repression of EZH2 target genes. Interestingly, NSD1 is involved in H3K36 methylation, a mark associated with transcriptional activation, and exhibits exquisite dosage sensitivity leading to overgrowth when deleted and severe undergrowth when duplicated in vivo. Although there is currently no evidence of dosage effects for DNMT3A, the co-occurrence of a duplication involving this gene and a pathogenic alteration in EZH2 in a patient with severe undergrowth is suggestive of a similar paradigm and further study is warranted.

Functional validation reveals the novel missense V419L variant in TGFBR2 associated with Loeys-Dietz syndrome (LDS) impairs canonical TGF-ß signaling.

TGF-ß-related heritable connective tissue disorders are characterized by a similar pattern of cardiovascular defects, including aortic root dilatation, mitral valve prolapse, vascular aneurysms, and vascular dissections and exhibit incomplete penetrance and variable expressivity. Because of the phenotypic overlap of these disorders, panel-based genetic testing is frequently used to confirm the clinical findings. Unfortunately in many cases, variants of uncertain significance (VUSs) obscure the genetic diagnosis until more information becomes available. Here, we describe and characterize the functional impact of a novel VUS in the TGFBR2 kinase domain (c.1255G>T; p.Val419Leu), in a patient with the clinical diagnosis of Marfan syndrome spectrum. We assessed the structural and functional consequence of this VUS using molecular modeling, molecular dynamic simulations, and in vitro cell-based assays. A high-quality homology-based model of TGFBR2 was generated and computational mutagenesis followed by refinement and molecular dynamics simulations were used to assess structural and dynamic changes. Relative to wild type, the V419L induced conformational and dynamic changes that may affect ATP binding, increasing the likelihood of adopting an inactive state, and, we hypothesize, alter canonical signaling. Experimentally, we tested this by measuring the canonical TGF-ß signaling pathway activation at two points; V419L significantly delayed SMAD2 phosphorylation by western blot and significantly decreased TGF-ß-induced gene transcription by reporter assays consistent with known pathogenic variants in this gene. Thus, our results establish that the V419L variant leads to aberrant TGF-ß signaling and confirm the diagnosis of Loeys-Dietz syndrome in this patient.

A novel de novo frameshift deletion in EHMT1 in a patient with Kleefstra Syndrome results in decreased H3K9 dimethylation.

BACKGROUND: Kleefstra Syndrome (KS) (MIM# 610253) is an autosomal dominant disorder caused by haploinsufficiency of euchromatic histone methyltransferase-1 (EHMT1, GLP). EHMT1 (MIM# 607001) encodes a histone methyltransferase that heterodimerizes with EHMT2 (also known as G9a, MIM# 604599), which together are responsible for mono- and dimethylation of H3 lysine 9 (H3K9me1 and -me2), resulting in transcriptional repression of target genes. METHODS: This report describes an 18-year-old woman with intellectual disability, severely limited speech, hypotonia, microcephaly, and facial dysmorphisms, who was found to have a novel de novo single-base frameshift deletion in EHMT1. RESULTS: Functional studies using patient fibroblasts showed decreased H3K9me2 compared to wild-type control cells, thus providing a rapid confirmatory test that complements molecular studies. CONCLUSION: Whole exome sequencing revealed a novel frameshift deletion in EHMT1 after a lengthy diagnostic odyssey in this patient. Functional testing using this patient's fibroblasts provides proof-of-concept for the analysis of variants of uncertain significance that are predicted to impact EHMT1 enzymatic activity.

The promise of epigenomic therapeutics in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is often viewed to arise primarily by genetic alterations. However, today we know that many aspects of the cancer phenotype require a crosstalk among these genetic alterations with epigenetic changes. Indeed, aberrant gene expression patterns, driven by epigenetics are fixed by altered signaling from mutated oncogenes and tumor suppressors to define the PDAC phenotype. This conceptual framework may have significant mechanistic value and could offer novel possibilities for treating patients affected with PDAC. In fact, extensive investigations are leading to the development of small molecule drugs that reversibly modify the epigenome. These new 'epigenetic therapeutics' discussed herein are promising to fuel a new era of studies, by providing the medical community with new tools to treat this dismal disease.

Krüppel-like factor KLF10 deficiency predisposes to colitis through colonic macrophage dysregulation.

Krüppel-like factor (KLF)-10 is an important transcriptional regulator of TGF-ß1 signaling in both CD8(+) and CD4(+) T lymphocytes. In the present study, we demonstrate a novel role for KLF10 in the regulation of TGFßRII expression with functional relevance in macrophage differentiation and activation. We first show that transfer of KLF10(-/-) bone marrow-derived macrophages into wild-type (WT) mice leads to exacerbation of experimental colitis. At the cell biological level, using two phenotypic strategies, we show that KLF10-deficient mice have an altered colonic macrophage phenotype with higher frequency of proinflammatory LyC6(+)MHCII(+) cells and a reciprocal decrease of the anti-inflammatory LyC6(-)MHCII(+) subset. Additionally, the anti-inflammatory CD11b(+)CX3CR1(hi) subset of colonic macrophages is significantly decreased in KLF10(-/-) compared with WT mice under inflammatory conditions. Molecularly, CD11b(+) colonic macrophages from KLF10(-/-) mice exhibit a proinflammatory cytokine profile with increased production of TNF-α and lower production of IL-10 in response to LPS stimulation. Because KLF10 is a transcription factor, we explored how this protein may regulate macrophage function. Consequently, we analyzed the expression of TGFßRII expression in colonic macrophages and found that, in the absence of KLF10, macrophages express lower levels of TGFßRII and display an attenuated Smad-2 phosphorylation following TGF-ß1 stimulation. We further show that KLF10 directly binds to the TGFßRII promoter in macrophages, leading to enhanced gene expression through histone H3 acetylation. Collectively, our data reveal a critical role for KLF10 in the epigenetic regulation of TGFßRII expression in macrophages and the acquisition of a "regulatory" phenotype that contributes to intestinal mucosal homeostasis.

Perhexiline activates KLF14 and reduces atherosclerosis by modulating ApoA-I production.

Recent genome-wide association studies have revealed that variations near the gene locus encoding the transcription factor Krüppel-like factor 14 (KLF14) are strongly associated with HDL cholesterol (HDL-C) levels, metabolic syndrome, and coronary heart disease. However, the precise mechanisms by which KLF14 regulates lipid metabolism and affects atherosclerosis remain largely unexplored. Here, we report that KLF14 is dysregulated in the liver of 2 dyslipidemia mouse models. We evaluated the effects of both KLF14 overexpression and genetic inactivation and determined that KLF14 regulates plasma HDL-C levels and cholesterol efflux capacity by modulating hepatic ApoA-I production. Hepatic-specific Klf14 deletion in mice resulted in decreased circulating HDL-C levels. In an attempt to pharmacologically target KLF14 as an experimental therapeutic approach, we identified perhexiline, an approved therapeutic small molecule presently in clinical use to treat angina and heart failure, as a KLF14 activator. Indeed, in WT mice, treatment with perhexiline increased HDL-C levels and cholesterol efflux capacity via KLF14-mediated upregulation of ApoA-I expression. Moreover, perhexiline administration reduced atherosclerotic lesion development in apolipoprotein E-deficient mice. Together, these results provide comprehensive insight into the KLF14-dependent regulation of HDL-C and subsequent atherosclerosis and indicate that interventions that target the KLF14 pathway should be further explored for the treatment of atherosclerosis.

The Triple-Code Model for Pancreatic Cancer: Cross Talk Among Genetics, Epigenetics, and Nuclear Structure.

Pancreatic adenocarcinoma is painful, generally incurable, and frequently lethal. The current progression model indicates that this cancer evolves by mutations and deletions in key oncogenes and tumor suppressor genes. This article describes an updated, more comprehensive model that includes concepts from the fields of epigenetics and nuclear architecture. Widespread use of next-generation sequencing for identifying genetic and epigenetic changes genome-wide will help identify and validate more and better markers for this disease. Epigenetic alterations are amenable to pharmacologic manipulations, thus this new integrated paradigm will contribute to advance this field from a mechanistic and translational point of view.

Development and characterization of human-induced pluripotent stem cell-derived cholangiocytes.

Cholangiocytes are the target of a heterogeneous group of liver diseases known as the cholangiopathies. An evolving understanding of the mechanisms driving biliary development provides the theoretical underpinnings for rational development of induced pluripotent stem cell (iPSC)-derived cholangiocytes (iDCs). Therefore, the aims of this study were to develop an approach to generate iDCs and to fully characterize the cells in vitro and in vivo. Human iPSC lines were generated by forced expression of the Yamanaka pluripotency factors. We then pursued a stepwise differentiation strategy toward iDCs, using precise temporal exposure to key biliary morphogens, and we characterized the cells, using a variety of morphologic, molecular, cell biologic, functional, and in vivo approaches. Morphology shows a stepwise phenotypic change toward an epithelial monolayer. Molecular analysis during differentiation shows appropriate enrichment in markers of iPSC, definitive endoderm, hepatic specification, hepatic progenitors, and ultimately cholangiocytes. Immunostaining, western blotting, and flow cytometry demonstrate enrichment of multiple functionally relevant biliary proteins. RNA sequencing reveals that the transcriptome moves progressively toward that of human cholangiocytes. iDCs generate intracellular calcium signaling in response to ATP, form intact primary cilia, and self-assemble into duct-like structures in three-dimensional culture. In vivo, the cells engraft within mouse liver, following retrograde intrabiliary infusion. In summary, we have developed a novel approach to generate mature cholangiocytes from iPSCs. In addition to providing a model of biliary differentiation, iDCs represent a platform for in vitro disease modeling, pharmacologic testing, and individualized, cell-based, regenerative therapies for the cholangiopathies.

Krüppel-like factor KLF10 regulates transforming growth factor receptor II expression and TGF-ß signaling in CD8+ T lymphocytes.

KLF10 has recently elicited significant attention as a transcriptional regulator of transforming growth factor-ß1 (TGF-ß1) signaling in CD4(+) T cells. In the current study, we demonstrate a novel role for KLF10 in the regulation of TGF-ß receptor II (TGF-ßRII) expression with functional relevance in antiviral immune response. Specifically, we show that KLF10-deficient mice have an increased number of effector/memory CD8(+) T cells, display higher levels of the T helper type 1 cell-associated transcription factor T-bet, and produce more IFN-γ following in vitro stimulation. In addition, KLF10(-/-) CD8(+) T cells show enhanced proliferation in vitro and homeostatic proliferation in vivo. Freshly isolated CD8(+) T cells from the spleen of adult mice express lower levels of surface TGF-ßRII (TßRII). Congruently, in vitro activation of KLF10-deficient CD8(+) T cells upregulate TGF-ßRII to a lesser extent compared with wild-type (WT) CD8(+) T cells, which results in attenuated Smad2 phosphorylation following TGF-ß1 stimulation compared with WT CD8(+) T cells. Moreover, we demonstrate that KLF10 directly binds to the TGF-ßRII promoter in T cells, leading to enhanced gene expression. In vivo viral infection with Daniel's strain Theiler's murine encephalomyelitis virus (TMEV) also led to lower expression of TGF-ßRII among viral-specific KLF10(-/-) CD8(+) T cells and a higher percentage of IFN-γ-producing CD8(+) T cells in the spleen. Collectively, our data reveal a critical role for KLF10 in the transcriptional activation of TGF-ßRII in CD8(+) T cells. Thus, KLF10 regulation of TGF-ßRII in this cell subset may likely play a critical role in viral and tumor immune responses for which the integrity of the TGF-ß1/TGF-ßRII signaling pathway is crucial.

Differential coupling of KLF10 to Sin3-HDAC and PCAF regulates the inducibility of the FOXP3 gene.

Inducible gene expression, which requires chromatin remodeling on gene promoters, underlies the epigenetically inherited differentiation program of most immune cells. However, chromatin-mediated mechanisms that underlie these events in T regulatory cells remain to be fully characterized. Here, we report that inducibility of FOXP3, a key transcription factor for the development of T regulatory cells, depends upon Kruppel-like factor 10 (KLF10) interacting with two antagonistic histone-modifying systems. We utilized chromatin immunoprecipitation, genome-integrated reporter assays, and functional domain KLF10 mutant proteins, to characterize reciprocal interactions between this transcription factor and either the Sin3-histone deacetylase complex or the histone acetyltransferase, p300/CBP-associated factor (PCAF). We characterize a Sin3-interacting repressor domain on the NH2 terminus of KLF10, which works to limit the activating function of this transcription factor. Indeed, inactivation of this Sin3-interacting domain renders KLF10 able to physically associate with PCAF as to induce FOXP3 gene transcription. We show that this biochemical data derived from studying our genome-integrated reporter cell system are recapitulated in primary murine lymphocytes. Collectively, these results advance our understanding of how a single transcription factor, namely KLF10, functions as a toggle to integrate antagonistic signals regulating FOXP3 and, thus, immune activation.

Aurora-A mitotic kinase induces endocrine resistance through down-regulation of ERα expression in initially ERα+ breast cancer cells.

Development of endocrine resistance during tumor progression represents a major challenge in the management of estrogen receptor alpha (ERα) positive breast tumors and is an area under intense investigation. Although the underlying mechanisms are still poorly understood, many studies point towards the 'cross-talk' between ERα and MAPK signaling pathways as a key oncogenic axis responsible for the development of estrogen-independent growth of breast cancer cells that are initially ERα+ and hormone sensitive. In this study we employed a metastatic breast cancer xenograft model harboring constitutive activation of Raf-1 oncogenic signaling to investigate the mechanistic linkage between aberrant MAPK activity and development of endocrine resistance through abrogation of the ERα signaling axis. We demonstrate for the first time the causal role of the Aurora-A mitotic kinase in the development of endocrine resistance through activation of SMAD5 nuclear signaling and down-regulation of ERα expression in initially ERα+ breast cancer cells. This contribution is highly significant for the treatment of endocrine refractory breast carcinomas, because it may lead to the development of novel molecular therapies targeting the Aurora-A/SMAD5 oncogenic axis. We postulate such therapy to result in the selective eradication of endocrine resistant ERαlow/- cancer cells from the bulk tumor with consequent benefits for breast cancer patients.

Membrane-to-nucleus signaling links insulin-like growth factor-1- and stem cell factor-activated pathways.

Stem cell factor (mouse: Kitl, human: KITLG) and insulin-like growth factor-1 (IGF1), acting via KIT and IGF1 receptor (IGF1R), respectively, are critical for the development and integrity of several tissues. Autocrine/paracrine KITLG-KIT and IGF1-IGF1R signaling are also activated in several cancers including gastrointestinal stromal tumors (GIST), the most common sarcoma. In murine gastric muscles, IGF1 promotes Kitl-dependent development of interstitial cells of Cajal (ICC), the non-neoplastic counterpart of GIST, suggesting cooperation between these pathways. Here, we report a novel mechanism linking IGF1-IGF1R and KITLG-KIT signaling in both normal and neoplastic cells. In murine gastric muscles, the microenvironment for ICC and GIST, human hepatic stellate cells (LX-2), a model for cancer niches, and GIST cells, IGF1 stimulated Kitl/KITLG protein and mRNA expression and promoter activity by activating several signaling pathways including AKT-mediated glycogen synthase kinase-3ß inhibition (GSK3i). GSK3i alone also stimulated Kitl/KITLG expression without activating mitogenic pathways. Both IGF1 and GSK3i induced chromatin-level changes favoring transcriptional activation at the Kitl promoter including increased histone H3/H4 acetylation and H3 lysine (K) 4 methylation, reduced H3K9 and H3K27 methylation and reduced occupancy by the H3K27 methyltransferase EZH2. By pharmacological or RNA interference-mediated inhibition of chromatin modifiers we demonstrated that these changes have the predicted impact on KITLG expression. KITLG knock-down and immunoneutralization inhibited the proliferation of GIST cells expressing wild-type KIT, signifying oncogenic autocrine/paracrine KITLG-KIT signaling. We conclude that membrane-to-nucleus signaling involving GSK3i establishes a previously unrecognized link between the IGF1-IGF1R and KITLG-KIT pathways, which is active in both physiologic and oncogenic contexts and can be exploited for therapeutic purposes.

A novel role of the Sp/KLF transcription factor KLF11 in arresting progression of endometriosis.

Endometriosis affects approximately 10% of young, reproductive-aged women. Disease associated pelvic pain; infertility and sexual dysfunction have a significant adverse clinical, social and financial impact. As precise disease etiology has remained elusive, current therapeutic strategies are empiric, unfocused and often unsatisfactory. Lack of a suitable genetic model has impaired further translational research in the field. In this study, we evaluated the role of the Sp/KLF transcription factor KLF11/Klf11 in the pathogenesis of endometriosis. KLF11, a human disease-associated gene is etiologically implicated in diabetes, uterine fibroids and cancer. We found that KLF11 expression was diminished in human endometriosis implants and further investigated its pathogenic role in Klf11-/- knockout mice with surgically induced endometriotic lesions. Lesions in Klf11-/- animals were large and associated with prolific fibrotic adhesions resembling advanced human disease in contrast to wildtype controls. To determine phenotype-specificity, endometriosis was also generated in Klf9-/- animals. Unlike in Klf11-/- mice, lesions in Klf9-/- animals were neither large, nor associated with a significant fibrotic response. KLF11 also bound to specific elements located in the promoter regions of key fibrosis-related genes from the Collagen, MMP and TGF-ß families in endometrial stromal cells. KLF11 binding resulted in transcriptional repression of these genes. In summary, we identify a novel pathogenic role for KLF11 in preventing de novo disease-associated fibrosis in endometriosis. Our model validates in vivo the phenotypic consequences of dysregulated Klf11 signaling. Additionally, it provides a robust means not only for further detailed mechanistic investigation but also the ability to test any emergent translational ramifications thereof, so as to expand the scope and capability for treatment of endometriosis.

Insights into the epigenetic mechanisms controlling pancreatic carcinogenesis.

During the last couple decades, we have significantly advanced our understanding of mechanisms underlying the development of pancreatic ductual adenocarcinoma (PDAC). In the late 1990s into the early 2000s, a model of PDAC development and progression was developed as a multi-step process associated with the accumulation of somatic mutations. The correlation and association of these particular genetic aberrations with the establishment and progression of PDAC has revolutionized our understanding of this process. However, this model leaves out other molecular events involved in PDAC pathogenesis that contribute to its development and maintenance, specifically those being epigenetic events. Thus, a new model considering the new scientific paradigms of epigenetics will provide a more comprehensive and useful framework for understanding the pathophysiological mechanisms underlying this disease. Epigenetics is defined as the type of inheritance not based on a particular DNA sequence but rather traits that are passed to the next generation via DNA and histone modifications as well as microRNA-dependent mechanisms. Key tumor suppressors that are well established to play a role in PDAC may be altered through hypermethylation, and oncogenes can be upregulated secondary to permissive histone modifications. Factors involved in tumor invasiveness can be aberrantly expressed through dysregulated microRNAs. A noteworthy characteristic of epigenetic-based inheritance is its reversibility, which is in contrast to the stable nature of DNA sequence-based alterations. Given this nature of epigenetic alterations, it becomes imperative that our understanding of epigenetic-based events promoting and maintaining PDAC continues to grow.

Polycomb antagonizes p300/CREB-binding protein-associated factor to silence FOXP3 in a Kruppel-like factor-dependent manner.

Inducible gene expression underlies the epigenetically inherited differentiation program of most immune cells. We report that the promoter of the FOXP3 gene possesses two distinct functional states: an "off state" mediated by the polycomb histone methyltransferase complex and a histone acetyltransferase-dependent "on state." Regulating these states is the presence of a Kruppel-like factor (KLF)-containing Polycomb response element. In the KLF10(-/-) mouse, the FOXP3 promoter is epigenetically silenced by EZH2 (Enhancer of Zeste 2)-mediated trimethylation of Histone 3 K27; thus, impaired FOXP3 induction and inappropriate adaptive T regulatory cell differentiation results in vitro and in vivo. The epigenetic transmittance of adaptive T regulatory cell deficiency is demonstrated throughout more than 40 generations of mice. These results provide insight into chromatin remodeling events key to phenotypic features of distinct T cell populations.