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1.
Int J Mol Sci ; 22(11)2021 May 31.
Artigo em Inglês | MEDLINE | ID: mdl-34072831

RESUMO

Although histone deacetylase 8 (HDAC8) plays a role in glioblastoma multiforme (GBM), whether its inhibition facilitates the treatment of temozolomide (TMZ)-resistant GBM (GBM-R) remains unclear. By assessing the gene expression profiles from short hairpin RNA of HDAC8 in the new version of Connectivity Map (CLUE) and cells treated by NBM-BMX (BMX)-, an HDAC8 inhibitor, data analysis reveals that the Wnt signaling pathway and apoptosis might be the underlying mechanisms in BMX-elicited treatment. This study evaluated the efficacy of cotreatment with BMX and TMZ in GBM-R cells. We observed that cotreatment with BMX and TMZ could overcome resistance in GBM-R cells and inhibit cell viability, markedly inhibit cell proliferation, and then induce cell cycle arrest and apoptosis. In addition, the expression level of ß-catenin was reversed by proteasome inhibitor via the ß-catenin/ GSK3ß signaling pathway to reduce the expression level of c-Myc and cyclin D1 in GBM-R cells. BMX and TMZ cotreatment also upregulated WT-p53 mediated MGMT inhibition, thereby triggering the activation of caspase-3 and eventually leading to apoptosis in GBM-R cells. Moreover, BMX and TMZ attenuated the expression of CD133, CD44, and SOX2 in GBM-R cells. In conclusion, BMX overcomes TMZ resistance by enhancing TMZ-mediated cytotoxic effect by downregulating the ß-catenin/c-Myc/SOX2 signaling pathway and upregulating WT-p53 mediated MGMT inhibition. These findings indicate a promising drug combination for precision personal treating of TMZ-resistant WT-p53 GBM cells.


Assuntos
Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Glioblastoma/tratamento farmacológico , Histona Desacetilases/genética , Proteínas Repressoras/genética , Proteína Supressora de Tumor p53/genética , Proteínas Supressoras de Tumor/genética , beta Catenina/genética , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos/genética , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Glioblastoma/genética , Glioblastoma/patologia , Humanos , Proteínas Repressoras/antagonistas & inibidores , Bibliotecas de Moléculas Pequenas/farmacologia , Temozolomida/efeitos adversos , Temozolomida/farmacologia , Ensaios Antitumorais Modelo de Xenoenxerto
2.
Nat Commun ; 12(1): 3520, 2021 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-34112784

RESUMO

The Immunodeficiency Centromeric Instability Facial Anomalies (ICF) 4 syndrome is caused by mutations in LSH/HELLS, a chromatin remodeler promoting incorporation of histone variant macroH2A. Here, we demonstrate that LSH depletion results in degradation of nascent DNA at stalled replication forks and the generation of genomic instability. The protection of stalled forks is mediated by macroH2A, whose knockdown mimics LSH depletion and whose overexpression rescues nascent DNA degradation. LSH or macroH2A deficiency leads to an impairment of RAD51 loading, a factor that prevents MRE11 and EXO1 mediated nascent DNA degradation. The defect in RAD51 loading is linked to a disbalance of BRCA1 and 53BP1 accumulation at stalled forks. This is associated with perturbed histone modifications, including abnormal H4K20 methylation that is critical for BRCA1 enrichment and 53BP1 exclusion. Altogether, our results illuminate the mechanism underlying a human syndrome and reveal a critical role of LSH mediated chromatin remodeling in genomic stability.


Assuntos
DNA Helicases/metabolismo , Replicação do DNA , Instabilidade Genômica , Histonas/metabolismo , Rad51 Recombinase/metabolismo , Animais , Proteína BRCA1/metabolismo , Linhagem Celular Tumoral , Sobrevivência Celular/genética , Montagem e Desmontagem da Cromatina/genética , Sequenciamento de Cromatina por Imunoprecipitação , DNA Helicases/deficiência , DNA Helicases/genética , Enzimas Reparadoras do DNA/genética , Enzimas Reparadoras do DNA/metabolismo , Replicação do DNA/genética , Epigênese Genética , Exodesoxirribonucleases/genética , Exodesoxirribonucleases/metabolismo , Instabilidade Genômica/genética , Histonas/deficiência , Histonas/genética , Humanos , Proteína Homóloga a MRE11/genética , Proteína Homóloga a MRE11/metabolismo , Metilação , Camundongos , RNA Interferente Pequeno , Rad51 Recombinase/genética , Regulação para Cima
3.
Anticancer Res ; 41(5): 2583-2589, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33952487

RESUMO

BACKGROUND/AIM: High-grade gliomas have a poor prognosis despite standard treatment. The aim of the study was to identify new prognostic factors to select patients who need more intense treatment. PATIENTS AND METHODS: Forty-three consecutive patients underwent surgery plus chemoradiotherapy for pathologically diagnosed high-grade gliomas (grade III, IV). RESULTS: The median survival time was 989 days, and the 1-year survival rate was 87.6%. Among patients with grade IV disease, the median survival time, 1-year, and 2-year survival rate were 814 days, 82.6%, and 58.7%, respectively. In the univariate analysis, unmethylated MGMT promoter (p=0.0495), brainstem infiltration (p=0.0004), basal ganglia as the primary lesion site (p=0.0056), 3-dimensional conformal radiotherapy (p=0.0286), and <50 Gy (p=0.0049) were associated with a poor prognosis. In the multivariate analysis, only brainstem infiltration retained significance (HR for death, 0.21; 95% CI=0.06-0.70; p=0.011). CONCLUSION: Brainstem infiltration is a novel prognostic factor for poor prognosis in patients with high-grade gliomas.


Assuntos
Tronco Encefálico/imunologia , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Glioma/tratamento farmacológico , Glioma/radioterapia , Proteínas Supressoras de Tumor/genética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Gânglios da Base/imunologia , Gânglios da Base/patologia , Tronco Encefálico/patologia , Quimiorradioterapia/efeitos adversos , Intervalo Livre de Doença , Feminino , Regulação Neoplásica da Expressão Gênica/imunologia , Glioma/imunologia , Glioma/patologia , Humanos , Linfócitos do Interstício Tumoral/imunologia , Linfócitos do Interstício Tumoral/patologia , Masculino , Pessoa de Meia-Idade , Gradação de Tumores , Regiões Promotoras Genéticas/genética
4.
Neurol India ; 69(2): 362-366, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33904453

RESUMO

Background: Cockayne syndrome is an autosomal recessive disorder caused by biallelic mutations in ERCC6 or ERCC8 genes. Aims: To study the clinical and mutation spectrum of Cockayne syndrome. Setting and Design: Medical Genetics Outpatient Department of Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow. This was a prospective study from 2007 to 2015. Materials and Methods: Clinical details were recorded, and sequencing of ERCC6 and ERCC8 were performed. Results and Conclusions: Of the six families, one family had a homozygous mutation in ERCC8 and the other five families had homozygous mutations in ERCC6. Novel variants in ERCC6 were identified in four families. Phenotypic features may vary from severe to mild, and a strong clinical suspicion is needed for diagnosis during infancy or early childhood. Hence, molecular diagnosis is needed for confirmation of diagnosis in a child with a suspicion of Cockayne syndrome. Prenatal diagnosis can be provided only if molecular diagnosis is established in the proband.


Assuntos
Síndrome de Cockayne , DNA Helicases/genética , Enzimas Reparadoras do DNA/genética , Proteínas de Ligação a Poli-ADP-Ribose/genética , Fatores de Transcrição , Criança , Pré-Escolar , Síndrome de Cockayne/diagnóstico , Síndrome de Cockayne/genética , Feminino , Humanos , Índia , Mutação , Gravidez , Estudos Prospectivos , Fatores de Transcrição/genética
6.
Cancer Med ; 10(10): 3177-3187, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33838014

RESUMO

OBJECTIVE: Accumulating evidence from recent molecular diagnostic studies has indicated the prognostic significance of various genetic markers for patients with glioblastoma (GBM). To evaluate the impact of such genetic markers on prognosis, we retrospectively analyzed the outcomes of patients with IDH-wildtype GBM in our institution. In addition, to assess the impact of bevacizumab (BEV) treatment, we compared overall survival (OS) between the pre- and post-BEV eras. METHODS: We analyzed the data of 100 adult patients (over 18 years old) with IDH-wildtype GBM from our database between February 2006 and October 2018. Genetic markers, such as MGMT methylation status, EGFR amplification, CDKN2A homozygous deletion, and clinical factors were analyzed by evaluating the patients' OS. RESULTS: CDKN2A homozygous deletion showed no significant impact on OS in patients with methylated MGMT status (p = 0.5268), whereas among patients with unmethylated MGMT status, there was a significant difference in OS between patients with and without CDKN2A homozygous deletion (median OS: 14.7 and 16.9 months, respectively, p = 0.0129). This difference was more evident in the pre-BEV era (median OS: 10.1 and 15.6 months, respectively, p = 0.0351) but has become nonsignificant in the post-BEV era (median OS: 16.0 and 16.9 months, respectively, p = 0.1010) due to OS improvement in patients with CDKN2A homozygous deletion. However, these findings could not be validated in The Cancer Genome Atlas cohort. CONCLUSIONS: MGMT and CDKN2A status subdivided our cohort into three race-specific groups with different prognoses. Our findings indicate that BEV approval in Japan led to OS improvement exclusively for patients with concurrent unmethylated MGMT status and CDKN2A homozygous deletion.


Assuntos
Neoplasias Encefálicas/genética , Inibidor p16 de Quinase Dependente de Ciclina/genética , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Glioblastoma/genética , Isocitrato Desidrogenase/genética , Deleção de Sequência/genética , Proteínas Supressoras de Tumor/genética , Idoso , Antineoplásicos Imunológicos/uso terapêutico , Bevacizumab/uso terapêutico , Neoplasias Encefálicas/tratamento farmacológico , Metilação de DNA/genética , Feminino , Marcadores Genéticos/genética , Glioblastoma/tratamento farmacológico , Homozigoto , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico , Estudos Retrospectivos
7.
Eur J Endocrinol ; 185(1): 57-66, 2021 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-33909591

RESUMO

Patients with deletions on chromosome 9q31.2 may exhibit delayed puberty, craniofacial phenotype including cleft lip/palate, and olfactory bulb hypoplasia. We report a patient with congenital HH with anosmia (Kallmann syndrome, KS) and a de novo 2.38 Mb heterozygous deletion in 9q31.2. The deletion breakpoints (determined with whole-genome linked-read sequencing) were in the FKTN gene (9:108,331,353) and in a non-coding area (9:110,707,332) (hg19). The deletion encompassed six protein-coding genes (FKTN, ZNF462, TAL2, TMEM38B, RAD23B, and KLF4). ZNF462 haploinsufficiency was consistent with the patient's Weiss-Kruszka syndrome (craniofacial phenotype, developmental delay, and sensorineural hearing loss), but did not explain his KS. In further analyses, he did not carry rare sequence variants in 32 known KS genes in whole-exome sequencing and displayed no aberrant splicing of 15 KS genes that were expressed in peripheral blood leukocyte transcriptome. The deletion was 1.8 Mb upstream of a KS candidate gene locus (PALM2AKAP2) but did not suppress its expression. In conclusion, this is the first report of a patient with Weiss-Kruszka syndrome and KS. We suggest that patients carrying a microdeletion in 9q31.2 should be evaluated for the presence of KS and KS-related features.


Assuntos
Anormalidades Craniofaciais/genética , Proteínas de Ligação a DNA/genética , Deficiências do Desenvolvimento/genética , Perda Auditiva Neurossensorial/genética , Defeitos dos Septos Cardíacos/genética , Síndrome de Kallmann/genética , Proteínas de Membrana/genética , Proteínas do Tecido Nervoso/genética , Fatores de Transcrição/genética , Adolescente , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Cromossomos Humanos Par 9/genética , Anormalidades Craniofaciais/complicações , Enzimas Reparadoras do DNA/genética , Deficiências do Desenvolvimento/complicações , Deleção de Genes , Haploinsuficiência , Perda Auditiva Neurossensorial/complicações , Defeitos dos Septos Cardíacos/complicações , Humanos , Canais Iônicos/genética , Síndrome de Kallmann/complicações , Fatores de Transcrição Kruppel-Like/genética , Masculino , Proteínas de Membrana/metabolismo , Proteínas de Neoplasias/genética , Análise de Sequência de RNA , Síndrome , Sequenciamento Completo do Exoma
8.
Int J Mol Sci ; 22(8)2021 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-33923767

RESUMO

Glioblastoma multiforme (GBM) recurrences after temozolomide (TMZ) treatment result from the expansion of drug-resistant and potentially invasive GBM cells. This process is facilitated by O6-Methylguanine-DNA Methyltransferase (MGMT), which counteracts alkylating TMZ activity. We traced the expansion of invasive cell lineages under persistent chemotherapeutic stress in MGMTlow (U87) and MGMThigh (T98G) GBM populations to look into the mechanisms of TMZ-induced microevolution of GBM invasiveness. TMZ treatment induced short-term, pro-invasive phenotypic shifts of U87 cells, in the absence of Snail-1 activation. They were illustrated by a transient induction of their motility and followed by the hypertrophy and the signs of senescence in scarce U87 sub-populations that survived long-term TMZ stress. In turn, MGMThigh T98G cells reacted to the long-term TMZ treatment with the permanent induction of invasiveness. Ectopic Snail-1 down-regulation attenuated this effect, whereas its up-regulation augmented T98G invasiveness. MGMTlow and MGMThigh cells both reacted to the long-term TMZ stress with the induction of Cx43 expression. However, only in MGMThigh T98G populations, Cx43 was directly involved in the induction of invasiveness, as manifested by the induction of T98G invasiveness after ectopic Cx43 up-regulation and by the opposite effect after Cx43 down-regulation. Collectively, Snail-1/Cx43-dependent signaling participates in the long-term TMZ-induced microevolution of the invasive GBM front. High MGMT activity remains a prerequisite for this process, even though MGMT-related GBM chemoresistance is not necessary for its initiation.


Assuntos
Antineoplásicos Alquilantes/farmacologia , Movimento Celular/efeitos dos fármacos , Metilases de Modificação do DNA/metabolismo , Enzimas Reparadoras do DNA/metabolismo , Glioblastoma/metabolismo , Temozolomida/farmacologia , Proteínas Supressoras de Tumor/metabolismo , Animais , Linhagem Celular Tumoral , Conexina 43/metabolismo , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Humanos , Fenótipo , Ratos , Fatores de Transcrição da Família Snail/metabolismo , Proteínas Supressoras de Tumor/genética
9.
Cells ; 10(4)2021 04 10.
Artigo em Inglês | MEDLINE | ID: mdl-33920220

RESUMO

Cockayne syndrome (CS) is a DNA repair syndrome characterized by a broad spectrum of clinical manifestations such as neurodegeneration, premature aging, developmental impairment, photosensitivity and other symptoms. Mutations in Cockayne syndrome protein B (CSB) are present in the vast majority of CS patients and in other DNA repair-related pathologies. In the literature, the role of CSB in different DNA repair pathways has been highlighted, however, new CSB functions have been identified in DNA transcription, mitochondrial biology, telomere maintenance and p53 regulation. Herein, we present an overview of identified structural elements and processes that impact on CSB activity and its post-translational modifications, known to balance the different roles of the protein not only during normal conditions but most importantly in stress situations. Moreover, since CSB has been found to be overexpressed in a number of different tumors, its role in cancer is presented and possible therapeutic targeting is discussed.


Assuntos
Síndrome de Cockayne/genética , DNA Helicases/genética , Enzimas Reparadoras do DNA/genética , Neoplasias/genética , Proteínas de Ligação a Poli-ADP-Ribose/genética , Animais , Síndrome de Cockayne/metabolismo , Dano ao DNA , DNA Helicases/química , DNA Helicases/metabolismo , Reparo do DNA , Enzimas Reparadoras do DNA/química , Enzimas Reparadoras do DNA/metabolismo , Regulação Neoplásica da Expressão Gênica , Humanos , Modelos Moleculares , Mutação , Neoplasias/metabolismo , Proteínas de Ligação a Poli-ADP-Ribose/química , Proteínas de Ligação a Poli-ADP-Ribose/metabolismo , Conformação Proteica , Processamento de Proteína Pós-Traducional
10.
Int J Mol Sci ; 22(5)2021 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-33801310

RESUMO

BACKGROUND: The molecular regulation of increased MGMT expression in human brain tumors, the associated regulatory elements, and linkages of these to its epigenetic silencing are not understood. Because the heightened expression or non-expression of MGMT plays a pivotal role in glioma therapeutics, we applied bioinformatics and experimental tools to identify the regulatory elements in the MGMT and neighboring EBF3 gene loci. RESULTS: Extensive genome database analyses showed that the MGMT genomic space was rich in and harbored many undescribed RNA regulatory sequences and recognition motifs. We extended the MGMT's exon-1 promoter to 2019 bp to include five overlapping alternate promoters. Consensus sequences in the revised promoter for (a) the transcriptional factors CTCF, NRF1/NRF2, GAF, (b) the genetic switch MYC/MAX/MAD, and (c) two well-defined p53 response elements in MGMT intron-1, were identified. A putative protein-coding or non-coding RNA sequence was located in the extended 3' UTR of the MGMT transcript. Eleven non-coding RNA loci coding for miRNAs, antisense RNA, and lncRNAs were identified in the MGMT-EBF3 region and six of these showed validated potential for curtailing the expression of both MGMT and EBF3 genes. ChIP analysis verified the binding site in MGMT promoter for CTCF which regulates the genomic methylation and chromatin looping. CTCF depletion by a pool of specific siRNA and shRNAs led to a significant attenuation of MGMT expression in human GBM cell lines. Computational analysis of the ChIP sequence data in ENCODE showed the presence of NRF1 in the MGMT promoter and this occurred only in MGMT-proficient cell lines. Further, an enforced NRF2 expression markedly augmented the MGMT mRNA and protein levels in glioma cells. CONCLUSIONS: We provide the first evidence for several new regulatory components in the MGMT gene locus which predict complex transcriptional and posttranscriptional controls with potential for new therapeutic avenues.


Assuntos
Biomarcadores Tumorais/metabolismo , Metilases de Modificação do DNA/metabolismo , Enzimas Reparadoras do DNA/metabolismo , Epigênese Genética , Regulação Neoplásica da Expressão Gênica , Glioma/metabolismo , Sequências Reguladoras de Ácido Nucleico , Proteínas Supressoras de Tumor/metabolismo , Biomarcadores Tumorais/genética , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patologia , Fator de Ligação a CCCTC/genética , Fator de Ligação a CCCTC/metabolismo , Metilação de DNA , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Genômica , Glioma/genética , Glioma/patologia , Humanos , Fator 2 Relacionado a NF-E2/genética , Fator 2 Relacionado a NF-E2/metabolismo , Fator 1 Nuclear Respiratório/genética , Fator 1 Nuclear Respiratório/metabolismo , Regiões Promotoras Genéticas , RNA Interferente Pequeno/genética , RNA não Traduzido/genética , Proteínas Supressoras de Tumor/genética
11.
Int J Mol Sci ; 22(8)2021 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-33917711

RESUMO

Quantifying O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation plays an essential role in assessing the potential efficacy of alkylating agents in the chemotherapy of malignant gliomas. MGMT promoter methylation is considered to be a characteristic of subgroups of certain malignancies but has also been described in various peripheral inflammatory diseases. However, MGMT promoter methylation levels have not yet been investigated in non-neoplastic brain diseases. This study demonstrates for the first time that one can indeed detect slightly enhanced MGMT promoter methylation in individual cases of inflammatory demyelinating CNS diseases such as multiple sclerosis and progressive multifocal leucencephalopathy (PML), as well as in other demyelinating diseases such as central pontine and exptrapontine myelinolysis, and diseases with myelin damage such as Wallerian degeneration. In this context, we identified a reduction in the expression of the demethylase TET1 as a possible cause for the enhanced MGMT promoter methylation. Hence, we show for the first time that MGMT hypermethylation occurs in chronic diseases that are not strictly associated to distinct pathogens, oncogenic viruses or neoplasms but that lead to damage of the myelin sheath in various ways. While this gives new insights into epigenetic and pathophysiological processes involved in de- and remyelination, which might offer new therapeutic opportunities for demyelinating diseases in the future, it also reduces the specificity of MGMT hypermethylation as a tumor biomarker.


Assuntos
Doenças do Sistema Nervoso Central/etiologia , Doenças do Sistema Nervoso Central/metabolismo , Metilação de DNA , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Suscetibilidade a Doenças , Proteínas Supressoras de Tumor/genética , Idoso , Biomarcadores , Biópsia , Doenças do Sistema Nervoso Central/diagnóstico , Metilases de Modificação do DNA/metabolismo , Enzimas Reparadoras do DNA/metabolismo , Epigênese Genética , Feminino , Regulação Neoplásica da Expressão Gênica , Humanos , Imuno-Histoquímica , Masculino , Pessoa de Meia-Idade , Oxigenases de Função Mista/genética , Oxigenases de Função Mista/metabolismo , Regiões Promotoras Genéticas , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Supressoras de Tumor/metabolismo
12.
Radiol Clin North Am ; 59(3): 305-322, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33926679

RESUMO

Molecular features are now essential in distinguishing between glioma histologic subtypes. Currently, isocitrate dehydrogenase mutation, 1p19q codeletion, and MGMT methylation status play significant roles in optimizing medical and surgical treatment. Noninvasive pretreatment and post-treatment determination of glioma subtype is of great interest. Although imaging cannot replace the genetic panel at present, image findings have shown promising signs to identify and diagnose the types and subtypes of gliomas. This article details key imaging findings in the most common molecular glioma subtypes and highlights recent advances in imaging technologies to differentiate these lesions noninvasively.


Assuntos
Neoplasias Encefálicas/diagnóstico por imagem , Neoplasias Encefálicas/genética , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Isocitrato Desidrogenase/genética , Imageamento por Ressonância Magnética/métodos , Mutação/genética , Tomografia Computadorizada por Raios X/métodos , Proteínas Supressoras de Tumor/genética , Encéfalo/diagnóstico por imagem , Humanos , Metilação
14.
J Theor Biol ; 521: 110662, 2021 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-33684406

RESUMO

Glioblastoma originates in the brain and is one of the most aggressive cancer types. Glioblastoma represents 15% of all brain tumours, with a median survival of 15 months. Although the current standard of care for such a tumour (the Stupp protocol) has shown positive results for the prognosis of patients, O-6-methylguanine-DNA methyltransferase (MGMT) driven drug resistance has been an issue of increasing concern and hence requires innovative approaches. In addition to the well established drug resistance factors such as tumour location and blood brain barriers, it is also important to understand how the genetic and epigenetic dynamics of the glioblastoma cells can play a role. One important aspect of this is the study of methylation status of MGMT following administration of temozolomide. In this paper, we extend our previously published model that simulated MGMT expression in glioblastoma cells to incorporate the promoter methylation status of MGMT. This methylation status has clinical significance and is used as a marker for patient outcomes. Using this model, we investigate the causative relationship between temozolomide treatment and the methylation status of the MGMT promoter in a population of cells. In addition by constraining the model to relevant biological data using Approximate Bayesian Computation, we were able to identify parameter regimes that yield different possible modes of resistances, namely, phenotypic selection of MGMT, a downshift in the methylation status of the MGMT promoter or both simultaneously. We analysed each of the parameter sets associated with the different modes of resistance, presenting representative solutions as well as discovering some similarities between them as well as unique requirements for each of them. Finally, we used them to devise optimal strategies for inhibiting MGMT expression with the aim of minimising live glioblastoma cell numbers.


Assuntos
Neoplasias Encefálicas , Glioblastoma , Antineoplásicos Alquilantes/uso terapêutico , Teorema de Bayes , Neoplasias Encefálicas/genética , Metilação de DNA/genética , Metilases de Modificação do DNA/genética , Metilases de Modificação do DNA/metabolismo , Metilases de Modificação do DNA/uso terapêutico , Enzimas Reparadoras do DNA/genética , Enzimas Reparadoras do DNA/metabolismo , Enzimas Reparadoras do DNA/uso terapêutico , Glioblastoma/tratamento farmacológico , Glioblastoma/genética , Humanos , O(6)-Metilguanina-DNA Metiltransferase/genética , O(6)-Metilguanina-DNA Metiltransferase/uso terapêutico , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismo
16.
AJNR Am J Neuroradiol ; 42(5): 845-852, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33664111

RESUMO

BACKGROUND AND PURPOSE: O6-Methylguanine-DNA methyltransferase (MGMT) promoter methylation confers an improved prognosis and treatment response in gliomas. We developed a deep learning network for determining MGMT promoter methylation status using T2 weighted Images (T2WI) only. MATERIALS AND METHODS: Brain MR imaging and corresponding genomic information were obtained for 247 subjects from The Cancer Imaging Archive and The Cancer Genome Atlas. One hundred sixty-three subjects had a methylated MGMT promoter. A T2WI-only network (MGMT-net) was developed to determine MGMT promoter methylation status and simultaneous single-label tumor segmentation. The network was trained using 3D-dense-UNets. Three-fold cross-validation was performed to generalize the performance of the networks. Dice scores were computed to determine tumor-segmentation accuracy. RESULTS: The MGMT-net demonstrated a mean cross-validation accuracy of 94.73% across the 3 folds (95.12%, 93.98%, and 95.12%, [SD, 0.66%]) in predicting MGMT methylation status with a sensitivity and specificity of 96.31% [SD, 0.04%] and 91.66% [SD, 2.06%], respectively, and a mean area under the curve of 0.93 [SD, 0.01]. The whole tumor-segmentation mean Dice score was 0.82 [SD, 0.008]. CONCLUSIONS: We demonstrate high classification accuracy in predicting MGMT promoter methylation status using only T2WI. Our network surpasses the sensitivity, specificity, and accuracy of histologic and molecular methods. This result represents an important milestone toward using MR imaging to predict prognosis and treatment response.


Assuntos
Neoplasias Encefálicas/diagnóstico por imagem , Neoplasias Encefálicas/genética , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Aprendizado Profundo , Glioma/diagnóstico por imagem , Glioma/genética , Imageamento por Ressonância Magnética/métodos , Proteínas Supressoras de Tumor/genética , Adulto , Idoso , Área Sob a Curva , Metilação de DNA , Humanos , Masculino , Pessoa de Meia-Idade , Redes Neurais de Computação , Regiões Promotoras Genéticas , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
17.
Neurol India ; 69(1): 119-125, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33642282

RESUMO

Objective: Preliminary study of magnetic resonance (MR) diffusion kurtosis imaging (DKI) assessing the pathological glial fibrillary acidic protein (GFAP), TopoIIα, and O 6-methylguanine-DNA methyltransferase (MGMT) expression in astrocytomas. Materials and Methods: This study was approved by the local ethics committee, and informed consent was obtained from all participants. Sixty-six cases with pathologically proven astrocytomas were enrolled in this study; of which, 34 were high grade and remaining 32 were low grade. They patients underwent conventional MRI head scan, DKI scan, and enhanced scan under the same conditions. Fractional anisotropy (FA) and mean kurtosis (MK) calculated from DKI, as well as GFAP, TopoIIα, and MGMT expression level were compared prospectively between high and low-grade astrocytomas. Spearman rank correlation analysis was used for comparing values of DKI and GFAP, TopoIIα, and MGMT expression level in the two groups. Results: The MK values were significantly higher in high-grade astrocytomas than those in low-grade astrocytomas (P < 0.05); FA values demonstrated no significant difference between the two groups (P = 0.331). GFAP expression level was significantly lower in high-grade astrocytomas than in low-grade astrocytomas (P < 0.05). Topo-IIα expression level were significantly higher in high-grade astrocytomas than in low-grade astrocytomas (P < 0.05). There was no significant difference in MGMT expression level between the two groups (P = 0.679). MK values were negatively correlated with the expression of GFAP (r = -0.836; P = 0.03), however, they were positively correlated with the expression of Topo-IIα (r = 0.896; P = 0.01). FA values were not correlated with the expression of GFAP (r = 0.366; P = 0.05), Topo-IIα (r = -0.562; P = 0.05), and MGMT (r = -0.153; P = 0.10). Conclusion: MK, the DKI parameter values of astrocytomas, was significantly correlated to the expression of GFAP and TopoIIα. To a certain extent, applying DKI may provide the biological behavior of tumor cell differentiation, proliferation activity, invasion and metastasis, and can guide individual treatment.


Assuntos
Astrocitoma , Neoplasias Encefálicas , Astrocitoma/diagnóstico por imagem , Neoplasias Encefálicas/diagnóstico por imagem , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Imagem de Difusão por Ressonância Magnética , Imagem de Tensor de Difusão , Proteína Glial Fibrilar Ácida , Humanos , Proteínas Supressoras de Tumor/genética
18.
Neurol India ; 69(1): 126-134, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33642283

RESUMO

Background: Telomerase reverse transcriptase promoter (pTERT) mutation is a dominant altered telomere maintenance mechanism in primary glioblastomas (GBMs). Objective: The aim of this study was to correlate pTERT mutations with clinico-histological features and other molecular markers (p53 protein-expression, ATRX protein-expression, IDH mutations, EGFR gene amplification and MGMT methylation) in adult GBMs. Materials and Methods: Evaluated for histological patterns, p53 and ATRX protein expression by immunohistochemistry (IHC), IDH mutations by IHC followed by sequencing in IHC negative cases, EGFR gene amplification by fluorescence in situ hybridization, MGMT promoter methylation by methylation-specific PCR and pTERT mutation by sequencing. Results: A total of 155 adult supratentorial GBMs [age-range 20-80 years] formed study cohort. 15.6% were IDH1R132 mutated, none were IDH2R172 mutated and 27% were EGFR amplified. 43% were MGMT methylated and were more common with IDH-mutation (mIDH) than EGFR amplification. 90% of mIDH (but no EGFR amplified) cases showed ATRX-loss. 43.5% were pTERT mutated (C228T was the commonest type) and were mutually exclusive with ATRX-loss. 14% of mIDH and 42% of EGFR amplified cases showed pTERT mutation, the latter was more commonly pMGMT unmethylated (63.6%). Conclusions: 43.5% of the GBMs showed pTERT mutation (C228T was commonest; 72%). pTERT mutations were mutually exclusive with ATRX protein loss, more commonly associated with IDH wild type and EGFR amplified GBMs.


Assuntos
Neoplasias Encefálicas , Glioblastoma , Telomerase , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias Encefálicas/genética , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Glioblastoma/genética , Humanos , Hibridização in Situ Fluorescente , Isocitrato Desidrogenase/genética , Isocitrato Desidrogenase/metabolismo , Pessoa de Meia-Idade , Mutação/genética , Prognóstico , Telomerase/genética , Proteínas Supressoras de Tumor/genética , Adulto Jovem
20.
Molecules ; 26(5)2021 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-33668176

RESUMO

Colorectal cancer is a common cancer worldwide and reduced expression of the DNA repair endonuclease XPF (xeroderma pigmentosum complementation group F) is associated with colorectal cancer. Bacopa monnieri extracts were previously found to exhibit chemical-genetic synthetic lethal effects in a Saccharomyces cerevisiae model of colorectal cancer lacking Rad1p, a structural and functional homologue of human XPF. However, the mechanisms for B. monnieri extracts to limit proliferation and promote an apoptosis-like event in RAD1 deleted yeast was not elucidated. Our current analysis has revealed that B. monnieri extracts have the capacity to promote mutations in rad1∆ cells. In addition, the effects of B. monnieri extracts on rad1∆ yeast is linked to disruption of the vacuole, similar to the mammalian lysosome. The absence of RAD1 in yeast sensitizes cells to the effects of vacuole disruption and the release of proteases. The combined effect of increased DNA mutations and release of vacuolar contents appears to induce an apoptosis-like event that is dependent on the meta-caspase Yca1p. The toxicity of B. monnieri extracts is linked to sterol content, suggesting saponins may be involved in limiting the proliferation of yeast cells. Analysis of major constituents from B. monnieri identified a chemical-genetic interaction between bacopasaponin C and rad1∆ yeast. Bacopasaponin C may have potential as a drug candidate or serve as a model for the development of analogs for the treatment of colorectal cancer.


Assuntos
Bacopa/química , Enzimas Reparadoras do DNA/metabolismo , Endonucleases/metabolismo , Glicosídeos/farmacologia , Extratos Vegetais/farmacologia , Proteínas de Saccharomyces cerevisiae/metabolismo , Triterpenos/farmacologia , Vacúolos/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Enzimas Reparadoras do DNA/deficiência , Enzimas Reparadoras do DNA/genética , Endonucleases/deficiência , Endonucleases/genética , Glicosídeos/química , Extratos Vegetais/química , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Triterpenos/química , Vacúolos/metabolismo
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