RESUMO
Changes in epigenetic programming have been proposed as being key events in the initiation and progression of childhood cancers. HMT euchromatic histone lysine methyltransferase 2 (G9a, EHMT2), which is encoded by the G9a (Ehmt2) gene, as well as its related protein GLP, which is encoded by the GLP/Ehmt1 gene, participate in epigenetic regulation by contributing to a transcriptionally repressed chromatin state. G9a/GLP activation has been reported in several cancer types. Herein, we evaluated the role of G9a in two solid pediatric tumors: neuroblastoma (NB) and Ewing sarcoma (ES). Our results show that G9a/Ehmt2 and GLP/Ehmt1 expression is higher in tumors with poorer prognosis, including St4 International Neuroblastoma Staging System (INSS) stage, MYCN amplified NB, and metastatic ES. Importantly, higher G9a and GLP levels were associated with shorter patient overall survival (OS) in both NB and ES. Moreover, pharmacological inhibition of G9a/GLP reduced cell viability in NB and ES cells. These findings suggest that G9a and GLP are associated with more aggressive NB and ES tumors and should be further investigated as being epigenetic targets in pediatric solid cancers.
Assuntos
Neuroblastoma , Sarcoma de Ewing , Criança , Humanos , Sobrevivência Celular/genética , Epigênese Genética , Antígenos de Histocompatibilidade/genética , Antígenos de Histocompatibilidade/metabolismo , Histona Metiltransferases/metabolismo , Histona-Lisina N-Metiltransferase/genética , Histona-Lisina N-Metiltransferase/metabolismo , Neuroblastoma/genética , Sarcoma de Ewing/genéticaRESUMO
The therapeutic targeting of the immune system, for example in vaccinology and cancer treatment, is a challenging task and the subject of active research. Several in silico tools used for predicting immunogenicity are based on the analysis of peptide sequences binding to the Major Histocompatibility Complex (pMHC). However, few of these bioinformatics tools take into account the pMHC three-dimensional structure. Here, we describe a new bioinformatics tool, MatchTope, developed for predicting peptide similarity, which can trigger cross-reactivity events, by computing and analyzing the electrostatic potentials of pMHC complexes. We validated MatchTope by using previously published data from in vitro assays. We thereby demonstrate the strength of MatchTope for similarity prediction between targets derived from several pathogens as well as for indicating possible cross responses between self and tumor peptides. Our results suggest that MatchTope can enhance and speed up future studies in the fields of vaccinology and cancer immunotherapy.
Assuntos
Complexo Principal de Histocompatibilidade , Peptídeos , Antígenos de Histocompatibilidade , Reações Cruzadas , Sequência de AminoácidosRESUMO
Changes in epigenetic programming are associated with cancer development during childhood. Components of the epigenetic machinery involved in normal embryonic development and hijacked by pediatric cancers include enzymes mediating post-translational modifications of DNA and histones that regulate chromatin structure, such as histone methyltransferases (HMTs). Overexpression of the HMT G9a (euchromatic histone lysine methyltransferase 2, EHMT2) has been described in several cancer types. Medulloblastoma (MB), the main type of malignant brain tumor afflicting children, is currently classified into four molecular subgroups. Here, we show that expression level of the G9a/Ehmt2 gene is higher in MB tumors belonging to the SHH, Group 3, and Group 4 subgroups, compared to Wnt tumors. Remarkably, high G9a expression was significantly associated with shorter overall survival in MB patients. We also present evidence that G9a inhibition dose-dependently reduces MB cell viability. Our findings suggest that higher transcription of G9a may be a predictor of poor prognosis in patients with SHH MB, and that inhibiting G9a activity can display antitumor effects in MB.
Assuntos
Neoplasias Cerebelares , Meduloblastoma , Criança , Humanos , Histona-Lisina N-Metiltransferase/genética , Meduloblastoma/genética , Prognóstico , Neoplasias Cerebelares/genética , Biomarcadores , Proteínas Hedgehog/genética , Antígenos de Histocompatibilidade/genética , Antígenos de Histocompatibilidade/metabolismoRESUMO
The emergence of horizontal transmission of cancer between vertebrates is an issue that interests scientists and medical society. Transmission requires: (i) a mechanism by which cancer cells can transfer to another organism and (ii) a repressed immune response on the part of the recipient. Transmissible tumors are unique models to comprehend the responses and mechanisms mediated by the major histocompatibility complex (MHC), which can be transposed for transplant biology. Here, we discuss the mechanisms involved in immune-mediated tissue rejection, making a parallel with transmissible cancers. We also discuss cellular and molecular mechanisms involved in cancer immunotherapy and anti-rejection therapies.
Assuntos
Imunoterapia , Neoplasias , Animais , Antígenos de Histocompatibilidade , Fatores Imunológicos , Complexo Principal de Histocompatibilidade , Neoplasias/genética , Neoplasias/terapiaRESUMO
Epigenetic mechanisms, including post-translational modifications of DNA and histones that influence chromatin structure, regulate gene expression during normal development and are also involved in carcinogenesis and cancer progression. The histone methyltransferase G9a (euchromatic histone lysine methyltransferase 2, EHMT2), which mostly mediates mono- and dimethylation by histone H3 lysine 9 (H3K9), influences gene expression involved in embryonic development and tissue differentiation. Overexpression of G9a has been observed in several cancer types, and different classes of G9a inhibitors have been developed as potential anticancer agents. Here, we review the emerging evidence suggesting the involvement of changes in G9a activity in brain tumors, namely glioblastoma (GBM), the main type of primary malignant brain cancer in adults, and medulloblastoma (MB), the most common type of malignant brain cancer in children. We also discuss the role of G9a in neuroblastoma (NB) and the drug development of G9a inhibitors.
Assuntos
Antineoplásicos/farmacologia , Neoplasias Encefálicas/tratamento farmacológico , Metilação de DNA , Epigênese Genética , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Histona-Lisina N-Metiltransferase/antagonistas & inibidores , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patologia , Antígenos de Histocompatibilidade , HumanosRESUMO
Despite the high number of individuals infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) who develop coronavirus disease 2019 (COVID-19) symptoms worldwide, many exposed individuals remain asymptomatic and/or uninfected and seronegative. This could be explained by a combination of environmental (exposure), immunological (previous infection), epigenetic, and genetic factors. Aiming to identify genetic factors involved in immune response in symptomatic COVID-19 as compared to asymptomatic exposed individuals, we analyzed 83 Brazilian couples where one individual was infected and symptomatic while the partner remained asymptomatic and serum-negative for at least 6 months despite sharing the same bedroom during the infection. We refer to these as "discordant couples". We performed whole-exome sequencing followed by a state-of-the-art method to call genotypes and haplotypes across the highly polymorphic major histocompatibility complex (MHC) region. The discordant partners had comparable ages and genetic ancestry, but women were overrepresented (65%) in the asymptomatic group. In the antigen-presentation pathway, we observed an association between HLA-DRB1 alleles encoding Lys at residue 71 (mostly DRB1*03:01 and DRB1*04:01) and DOB*01:02 with symptomatic infections and HLA-A alleles encoding 144Q/151R with asymptomatic seronegative women. Among the genes related to immune modulation, we detected variants in MICA and MICB associated with symptomatic infections. These variants are related to higher expression of soluble MICA and low expression of MICB. Thus, quantitative differences in these molecules that modulate natural killer (NK) activity could contribute to susceptibility to COVID-19 by downregulating NK cell cytotoxic activity in infected individuals but not in the asymptomatic partners.
Assuntos
Infecções Assintomáticas , COVID-19 , Antígenos de Histocompatibilidade , Complexo Principal de Histocompatibilidade , SARS-CoV-2 , Adulto , Idoso , Brasil , COVID-19/genética , COVID-19/imunologia , Feminino , Predisposição Genética para Doença , Genótipo , Antígenos de Histocompatibilidade/genética , Antígenos de Histocompatibilidade/imunologia , Humanos , Complexo Principal de Histocompatibilidade/genética , Complexo Principal de Histocompatibilidade/imunologia , Masculino , Pessoa de Meia-Idade , Sequenciamento do ExomaRESUMO
Experimentally estimating peptide-major histocompatibility complex (pMHC) binding affinity has been quite challenging due to the many receptors and the many potential ligands implicated in it. We have thus proposed a straightforward computational methodology considering the different mechanisms involved in pMHC binding to facilitate studying such receptor-ligand interactions. We have developed a pipeline using semi-empirical quantum mechanical methods for calculating pMHC class I and II molecules' binding energy (BE). This pipeline can systematize the methodology for calculating pMHC system BE, enabling the rational design of T-cell epitopes to be used as pharmaceuticals and vaccines.
Assuntos
Biologia Computacional/métodos , Antígenos de Histocompatibilidade/química , Modelos Moleculares , Oligopeptídeos/química , Teoria Quântica , Software , Algoritmos , Sequência de Aminoácidos , Antígenos de Histocompatibilidade/imunologia , Antígenos de Histocompatibilidade/metabolismo , Humanos , Ligantes , Oligopeptídeos/imunologia , Oligopeptídeos/metabolismo , Ligação Proteica , Relação Estrutura-AtividadeRESUMO
Euchromatic histone-lysine N-methyltransferase 1 (EHMT1) and EHMT2 are upregulated in various human cancers, and their deregulation is associated with tumor development and progression. In this paper, we investigated the expression level of EHMT1/EHMT2 in acute lymphoblastic leukemia (ALL) and whether the modulation of these enzymes could have any cellular or molecular impact on ALL cells. For this, we used UNC0646 as a priming strategy to target EHMT1/EHMT2 and investigated its effect on proliferation and cell viability of Jurkat cells by MTT assay. Then, considering the IC50 and IC75, cellular death was determined by Annexin V/PI staining using flow cytometry. Finally, we investigated by RT-PCR the molecular bases that could be involved in the observed effects. Interestingly, accessing the International Microarray Innovations in Leukemia (MILE) study group, we detected that both EHMT1 and EHMT2 are overexpressed in ALL. More important, we determined that inhibition of EHMT1/EHMT2 significantly decreased Jurkat cell viability in a dose-dependent manner. Accordingly, we observed that inhibition of EHMT1/EHMT2 promoted Jurkat cell death, which was accompanied by increased expression of P53, TP73, BAX, and MDM4. These results clearly indicate that inhibition of EHMT1/EHMT2 induces pro-apoptotic gene expression in ALL and promotes cell death. More importantly, the modulation of these histone methyltransferases may be a promising epigenetic target for ALL treatment.
Assuntos
Regulação Leucêmica da Expressão Gênica , Antígenos de Histocompatibilidade/genética , Histona-Lisina N-Metiltransferase/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Proteína Tumoral p73/genética , Proteína Supressora de Tumor p53/genética , Morte Celular , Proliferação de Células , Sobrevivência Celular , Simulação por Computador , Epigênese Genética , Humanos , Células JurkatRESUMO
Orchestrated events, including extensive changes in epigenetic marks, allow a somatic nucleus to become totipotent after transfer into an oocyte, a process termed nuclear reprogramming. Recently, several strategies have been applied in order to improve reprogramming efficiency, mainly focused on removing repressive epigenetic marks such as histone methylation from the somatic nucleus. Herein we used the specific and non-toxic chemical probe UNC0638 to inhibit the catalytic activity of the histone methyltransferases EHMT1 and EHMT2. Either the donor cell (before reconstruction) or the early embryo was exposed to the probe to assess its effect on developmental rates and epigenetic marks. First, we showed that the treatment of bovine fibroblasts with UNC0638 did mitigate the levels of H3K9me2. Moreover, H3K9me2 levels were decreased in cloned embryos regardless of treating either donor cells or early embryos with UNC0638. Additional epigenetic marks such as H3K9me3, 5mC, and 5hmC were also affected by the UNC0638 treatment. Therefore, the use of UNC0638 did diminish the levels of H3K9me2 and H3K9me3 in SCNT-derived blastocysts, but this was unable to improve their preimplantation development. These results indicate that the specific reduction of H3K9me2 by inhibiting EHMT1/2 during nuclear reprogramming impacts the levels of H3K9me3, 5mC, and 5hmC in preimplantation bovine embryos.
Assuntos
Reprogramação Celular/genética , Metilação de DNA/genética , Desenvolvimento Embrionário/genética , Histona Metiltransferases/genética , Animais , Blastocisto , Bovinos , Diferenciação Celular , Clonagem de Organismos/métodos , Transferência Embrionária/métodos , Epigênese Genética/genética , Regulação da Expressão Gênica no Desenvolvimento/genética , Antígenos de Histocompatibilidade/genética , Histona-Lisina N-Metiltransferase/genética , Técnicas de Transferência Nuclear , Oócitos/crescimento & desenvolvimento , Processamento de Proteína Pós-Traducional/genética , Quinazolinas/farmacologiaRESUMO
In this work, we analyze the structure-activity relationships (SAR) of epigenetic inhibitors (lysine mimetics) against lysine methyltransferase (G9a or EHMT2) using a combined activity landscape, molecular docking and molecular dynamics approach. The study was based on a set of 251 G9a inhibitors with reported experimental activity. The activity landscape analysis rapidly led to the identification of activity cliffs, scaffolds hops and other active an inactive molecules with distinct SAR. Structure-based analysis of activity cliffs, scaffold hops and other selected active and inactive G9a inhibitors by means of docking followed by molecular dynamics simulations led to the identification of interactions with key residues involved in activity against G9a, for instance with ASP 1083, LEU 1086, ASP 1088, TYR 1154 and PHE 1158. The outcome of this work is expected to further advance the development of G9a inhibitors.