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2.
Nat Commun ; 12(1): 803, 2021 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-33547285

RESUMO

Meiotic recombination is a critical process for plant breeding, as it creates novel allele combinations that can be exploited for crop improvement. In wheat, a complex allohexaploid that has a diploid-like behaviour, meiotic recombination between homoeologous or alien chromosomes is suppressed through the action of several loci. Here, we report positional cloning of Pairing homoeologous 2 (Ph2) and functional validation of the wheat DNA mismatch repair protein MSH7-3D as a key inhibitor of homoeologous recombination, thus solving a half-century-old question. Similar to ph2 mutant phenotype, we show that mutating MSH7-3D induces a substantial increase in homoeologous recombination (up to 5.5 fold) in wheat-wild relative hybrids, which is also associated with a reduction in homologous recombination. These data reveal a role for MSH7-3D in meiotic stabilisation of allopolyploidy and provides an opportunity to improve wheat's genetic diversity through alien gene introgression, a major bottleneck facing crop improvement.


Assuntos
DNA de Plantas/genética , Regulação da Expressão Gênica de Plantas , Recombinação Homóloga , Melhoramento Vegetal/métodos , Proteínas de Plantas/genética , Triticum/genética , Alelos , Quimera , Cromossomos de Plantas/química , Reparo de Erro de Pareamento de DNA , DNA de Plantas/metabolismo , Meiose , Mutação , Mapeamento Físico do Cromossomo , Proteínas de Plantas/metabolismo , Ploidias , Secale/genética , Secale/metabolismo , Triticum/metabolismo
3.
J Clin Pathol ; 74(4): 264-268, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33597222

RESUMO

DNA mismatch repair (MMR) proteins are essential for the recognition and correction of sporadic genetic mutations that occur during DNA replication. Deficient MMR function (dMMR) leads to an increased risk of development of neoplasia. Identification of dMMR within tumours can suggest a high chance of the inherited cancer condition Lynch syndrome and predicts poor clinical response to certain conventional chemotherapies but an increased likelihood of response to immunotherapy. This review provides an update on the biology of MMR proteins, their encoding genes and mechanisms for the development of dMMR. This is followed by a discussion of the identification and significance of dMMR in routine clinical practice.


Assuntos
Adenoma/genética , Biomarcadores Tumorais/genética , Carcinoma/genética , Neoplasias Colorretais Hereditárias sem Polipose/genética , Reparo de Erro de Pareamento de DNA , Enzimas Reparadoras do DNA/genética , Mutação , Adenoma/enzimologia , Adenoma/patologia , Adenoma/terapia , Biomarcadores Tumorais/metabolismo , Biópsia , Carcinoma/enzimologia , Carcinoma/patologia , Carcinoma/terapia , Neoplasias Colorretais Hereditárias sem Polipose/enzimologia , Neoplasias Colorretais Hereditárias sem Polipose/patologia , Neoplasias Colorretais Hereditárias sem Polipose/terapia , Enzimas Reparadoras do DNA/metabolismo , Predisposição Genética para Doença , Humanos , Fenótipo
4.
Am J Epidemiol ; 190(2): 230-238, 2021 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-33524116

RESUMO

People with Lynch syndrome (LS), who carry a pathogenic mutation in a DNA mismatch repair gene, have increased risks of colorectal cancer (CRC) and endometrial cancer (EC). A high reported variability in cancer risk suggests the existence of factors that modify cancer risk for persons with LS. We aimed to investigate the associations between height and CRC and EC risk for persons with LS using data from 2 large studies. Information on 1,115 men and 1,553 women with LS from the Colon Cancer Family Registry (1998-2007) and the GEOLynch Cohort Study (2006-2017) was harmonized. We used weighted Cox proportional hazards regression models with age on the time axis to estimate adjusted hazard ratios and 95% confidence intervals for each 5-cm increment in self-reported height. CRC was diagnosed in 947 persons during 65,369 person-years of observation, and 171 women were diagnosed with EC during 39,227 person-years. Height was not associated with CRC for either men (per 5-cm increment, hazard ratio (HR) = 1.00, 95% confidence interval (CI): 0.91, 1.11) or women (per 5-cm increment, HR = 1.01, 95% CI: 0.92, 1.11), nor was height associated with EC (per 5-cm increment, HR = 1.08, 95% CI: 0.94, 1.24). Hence, we observed no evidence for an association of height with either CRC or EC among persons with LS.


Assuntos
Estatura , Neoplasias Colorretais/epidemiologia , Neoplasias do Endométrio/epidemiologia , Adulto , Fatores Etários , Neoplasias Colorretais/genética , Neoplasias Colorretais Hereditárias sem Polipose/epidemiologia , Neoplasias Colorretais Hereditárias sem Polipose/genética , Reparo de Erro de Pareamento de DNA , Neoplasias do Endométrio/genética , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Modelos de Riscos Proporcionais , Fatores de Risco , Fatores Sexuais
5.
Nat Commun ; 12(1): 482, 2021 01 20.
Artigo em Inglês | MEDLINE | ID: mdl-33473124

RESUMO

DNA ligase 1 (LIG1, Cdc9 in yeast) finalizes eukaryotic nuclear DNA replication by sealing Okazaki fragments using DNA end-joining reactions that strongly discriminate against incorrectly paired DNA substrates. Whether intrinsic ligation fidelity contributes to the accuracy of replication of the nuclear genome is unknown. Here, we show that an engineered low-fidelity LIG1Cdc9 variant confers a novel mutator phenotype in yeast typified by the accumulation of single base insertion mutations in homonucleotide runs. The rate at which these additions are generated increases upon concomitant inactivation of DNA mismatch repair, or by inactivation of the Fen1Rad27 Okazaki fragment maturation (OFM) nuclease. Biochemical and structural data establish that LIG1Cdc9 normally avoids erroneous ligation of DNA polymerase slippage products, and this protection is compromised by mutation of a LIG1Cdc9 high-fidelity metal binding site. Collectively, our data indicate that high-fidelity DNA ligation is required to prevent insertion mutations, and that this may be particularly critical following strand displacement synthesis during the completion of OFM.


Assuntos
Replicação do DNA/fisiologia , DNA Fúngico/metabolismo , DNA/metabolismo , Saccharomyces cerevisiae/metabolismo , Acetiltransferases/metabolismo , DNA Ligase Dependente de ATP/metabolismo , DNA Ligases , Reparo de Erro de Pareamento de DNA/genética , Replicação do DNA/genética , DNA Polimerase Dirigida por DNA/metabolismo , Endonucleases Flap/metabolismo , Proteínas de Membrana/metabolismo , Mutagênese , Mutação , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo
6.
Anticancer Res ; 41(2): 975-982, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33517304

RESUMO

BACKGROUND/AIM: DNA mismatch repair (MMR) deficiency has received increasing attention as a biomarker of anti-PD-1 treatments of solid tumors including gastric cancer (GC). However, efficient screening has not been established. PATIENTS AND METHODS: A total of 513 patients were tested for the expression of MMR proteins by immunohistochemistry to identify MMR deficient GC. Development of a prediction model was attempted using the common clinicopathological features. RESULTS: In total, 11% (57/513) of the patients showed loss of expression of either one or more MMR proteins (MMR protein deficiency; MMR-D). Multivariate analysis demonstrated that age (≥70 years), sex (female), tumor location (lower 1/3), depth invasion (low, T1/T2/T3), and absence of distant metastasis were significantly independent predictive factors of MMR-D GCs. The MMR-D GC probability estimated by the prediction model ranged from 0.4% to 62.2%, and the area under the curve of the receiver operating characteristics curve was 0.82 (95% confidence interval=0.75-0.87). CONCLUSION: Our prediction model can sufficiently and efficiently identify MMR-D GCs using clinical features.


Assuntos
Reparo de Erro de Pareamento de DNA , Proteínas de Ligação a DNA/deficiência , Endonuclease PMS2 de Reparo de Erro de Pareamento/deficiência , Proteína 1 Homóloga a MutL/deficiência , Neoplasias Gástricas/patologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Área Sob a Curva , Biomarcadores Tumorais/metabolismo , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Gradação de Tumores , Invasividade Neoplásica , Caracteres Sexuais , Neoplasias Gástricas/metabolismo , Carga Tumoral , Adulto Jovem
7.
Int J Mol Sci ; 22(2)2021 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-33430305

RESUMO

Lynch syndrome, known as hereditary nonpolyposis colorectal cancer (HNPCC), is an autosomal-dominant familial cancer syndrome with an increased risk for urothelial cancer (UC). Mismatch repair (MMR) deficiency, due to pathogenic variants in MLH1, MSH2, MSH6, and PMS2, and microsatellite instability, are known for development of Lynch syndrome (LS) associated carcinogenesis. UC is the third most common cancer type in LS-associated tumors. The diversity of germline variants in the affected MMR genes and their following subsequent function loss might be responsible for the variation in cancer risk, suggesting an increased risk of developing UC in MSH2 mutation carriers. In this review, we will focus on LS-associated UC of the upper urinary tract (UUT) and bladder, their germline profiles, and outcomes compared to sporadic UC, the impact of genetic testing, as well as urological follow-up strategies in LS. In addition, we present a case of metastatic LS-associated UC of the UUT and bladder, achieving complete response during checkpoint inhibition since more than 2 years.


Assuntos
Carcinoma/genética , Neoplasias Colorretais Hereditárias sem Polipose/genética , Predisposição Genética para Doença , Urotélio/metabolismo , Carcinoma/complicações , Carcinoma/patologia , Neoplasias Colorretais Hereditárias sem Polipose/complicações , Neoplasias Colorretais Hereditárias sem Polipose/patologia , Reparo de Erro de Pareamento de DNA/genética , Proteínas de Ligação a DNA/genética , Humanos , Instabilidade de Microssatélites , Endonuclease PMS2 de Reparo de Erro de Pareamento/genética , Proteína 1 Homóloga a MutL/genética , Proteína 2 Homóloga a MutS/genética , Urotélio/patologia
8.
Cancer Sci ; 112(3): 1105-1113, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33403729

RESUMO

Microsatellite instability-high (MSI-H) is an important biomarker for predicting the effect of immune checkpoint inhibitors (ICIs) on advanced solid tumors. Microsatellite instability-high is detected in various cancers, but its frequency varies by cancer type and stage. Therefore, precise frequency is required to plan ICI therapy. In this study, the results of MSI tests actually carried out in clinical practice were investigated. In total, 26 469 samples of various cancers were examined between December 2018 and November 2019 to determine whether programmed cell death-1 blockade was indicated. The results of MSI tests were obtained for 26 237 (99.1%) of these samples. The male : female ratio was 51:49 and mean age was 64.3 years. In all samples, the overall frequency of MSI-H was 3.72%. By gender, the frequency of MSI-H was higher in female patients (4.75%) than in male patients (2.62%; P < .001). A comparison by age revealed that the frequency of MSI-H was significantly higher in patients younger than 40 years of age (6.12%) and 80 years or older (5.77%) than in patients aged between 60 and 79 years (3.09%; P < .001). Microsatellite instability-high was detected in 30 cancer types. Common cancer types were: endometrial cancer, 16.85%; small intestinal cancer, 8.63%; gastric cancer, 6.74%; duodenal cancer, 5.60%; and colorectal cancer, 3.78%. Microsatellite instability-high was detected in cancer derived from a wide variety of organs. The frequency of MSI-H varied by cancer type and onset age. These data should prove especially useful when considering ICI treatment.


Assuntos
Resistencia a Medicamentos Antineoplásicos/genética , Instabilidade de Microssatélites , Neoplasias/genética , Adolescente , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Anticorpos Monoclonais Humanizados , Criança , Pré-Escolar , Estudos de Coortes , Reparo de Erro de Pareamento de DNA , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias/tratamento farmacológico , Neoplasias/imunologia , Neoplasias/patologia , Receptor de Morte Celular Programada 1/antagonistas & inibidores , Receptor de Morte Celular Programada 1/imunologia , Fatores de Risco , Fatores Sexuais , Adulto Jovem
9.
Am J Hum Genet ; 108(1): 163-175, 2021 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-33357406

RESUMO

The lack of functional evidence for the majority of missense variants limits their clinical interpretability and poses a key barrier to the broad utility of carrier screening. In Lynch syndrome (LS), one of the most highly prevalent cancer syndromes, nearly 90% of clinically observed missense variants are deemed "variants of uncertain significance" (VUS). To systematically resolve their functional status, we performed a massively parallel screen in human cells to identify loss-of-function missense variants in the key DNA mismatch repair factor MSH2. The resulting functional effect map is substantially complete, covering 94% of the 17,746 possible variants, and is highly concordant (96%) with existing functional data and expert clinicians' interpretations. The large majority (89%) of missense variants were functionally neutral, perhaps unexpectedly in light of its evolutionary conservation. These data provide ready-to-use functional evidence to resolve the ∼1,300 extant missense VUSs in MSH2 and may facilitate the prospective classification of newly discovered variants in the clinic.


Assuntos
Predisposição Genética para Doença/genética , Proteína 2 Homóloga a MutS/genética , Mutação de Sentido Incorreto/genética , Neoplasias Colorretais Hereditárias sem Polipose/genética , Reparo de Erro de Pareamento de DNA/genética , Células HEK293 , Humanos
10.
Nucleic Acids Res ; 49(2): 1023-1032, 2021 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-33367848

RESUMO

Pseudomonas putida MPE exemplifies a novel clade of manganese-dependent single-strand DNA endonuclease within the binuclear metallophosphoesterase superfamily. MPE is encoded within a widely conserved DNA repair operon. Via structure-guided mutagenesis, we identify His113 and His81 as essential for DNA nuclease activity, albeit inessential for hydrolysis of bis-p-nitrophenylphosphate. We propose that His113 contacts the scissile phosphodiester and serves as a general acid catalyst to expel the OH leaving group of the product strand. We find that MPE cleaves the 3' and 5' single-strands of tailed duplex DNAs and that MPE can sense and incise duplexes at sites of short mismatch bulges and opposite a nick. We show that MPE is an ambidextrous phosphodiesterase capable of hydrolyzing the ssDNA backbone in either orientation to generate a mixture of 3'-OH and 3'-PO4 cleavage products. The directionality of phosphodiester hydrolysis is dictated by the orientation of the water nucleophile vis-à-vis the OH leaving group, which must be near apical for the reaction to proceed. We propose that the MPE active site and metal-bound water nucleophile are invariant and the enzyme can bind the ssDNA productively in opposite orientations.


Assuntos
Proteínas de Bactérias/metabolismo , Enzimas Reparadoras do DNA/metabolismo , DNA de Cadeia Simples/metabolismo , Desoxirribonuclease I/metabolismo , Pseudomonas putida/enzimologia , Proteínas de Bactérias/química , Pareamento de Bases , Domínio Catalítico , Reparo de Erro de Pareamento de DNA , Reparo do DNA , Enzimas Reparadoras do DNA/química , Desoxirribonuclease I/química , Histidina/química , Hidrólise , Manganês/química , Modelos Moleculares , Nitrofenóis/metabolismo , Fosfatos/química , Ligação Proteica , Conformação Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Relação Estrutura-Atividade , Água
11.
PLoS One ; 15(10): e0238836, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33095797

RESUMO

Recently, the Cancer Genome Atlas and Asian Cancer Research Group propose two new classifications system of gastric cancer by using multi-platforms of molecular analyses. However, these highly complicated and cost technologies have not yet been translated into full clinical utility. In addition, the clinicians are expected to gain more guidance of treatment for different molecular subtypes. In this study, we developed a panel of gastric cancer patients in population from Southern China using commercially accessible TMA and immunohistochemical technology. A cohort of 259 GC patients was classified into 4 subtypes on the basis of expression of mismatch repair proteins (PMS2, MLH1, MSH2, and MSH6), E-cadherin and p21 protein. We observed that the subtypes presented distinct prognosis. dMMR-like subtype was associated with the best prognosis, and E-cadherin-a subtype was associated with the worst prognosis. Patients with p21-High and p21-Ligh subtypes had intermediate overall survival. In multivariate analysis, the dMMR-like subtype remained an independent prediction power for overall survival in the model. We described a molecular classification of gastric cancers using clinically applicable assay. The biological relevance of the four subtypes was illustrated by significant differences in prognosis. Our molecular classification provided an effective and inexpensive screening tool for improving prognostic models. Nevertheless, our study should be considered preliminary and carries a limited predictive value as a single-center retrospective study.


Assuntos
Proteínas de Neoplasias/metabolismo , Neoplasias Gástricas/classificação , Neoplasias Gástricas/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Antígenos CD/metabolismo , Biomarcadores Tumorais/metabolismo , Caderinas/metabolismo , China , Estudos de Coortes , Inibidor de Quinase Dependente de Ciclina p21/metabolismo , Reparo de Erro de Pareamento de DNA , Proteínas de Ligação a DNA/metabolismo , Feminino , Humanos , Imuno-Histoquímica , Masculino , Pessoa de Meia-Idade , Endonuclease PMS2 de Reparo de Erro de Pareamento/metabolismo , Proteína 1 Homóloga a MutL/metabolismo , Proteína 2 Homóloga a MutS/metabolismo , Prognóstico , Estudos Retrospectivos , Neoplasias Gástricas/patologia , Análise Serial de Tecidos
12.
Bull Cancer ; 107(11): 1091-1097, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32980144

RESUMO

PURPOSE: This study aims to analyze sensitivities and polymorphisms of the Bethesda panel markers (BAT25, BAT26, D2S123, D5S346 and D17S250) for microsatellite instability testing in Chinese from Jiangsu Province and their clinical implication. METHODS: MSI, sensitivity and polymorphism analysis in 541 colorectal cancer (CRC) patients were detected by fragment analysis. RESULTS: Five hundred and twenty-five tissue samples and 541 blood samples of the 541 sample pairs were successfully amplified. Thirty-four (6.5%) cases were MSI-high (MSI-H) while 33 (6.3%) and 458 (87.2%) were MSI-low (MSI-L) and microsatellite stable (MSS), respectively. BAT26 (85.3%) exhibited the highest instability followed by BAT25 (82.4%), D2S123 (67.6%), D17S250 (64.7%) and D5S346 (50.0%) in MSI-H cases. The median ages of CRC patients with LS, MSI-H, MSI-L and MSS status were 38-43, 48, 60 and 63, respectively. 75.0%, 44.1%, 12.1% and 7.0% CRC cases were mucinous carcinomas in LS, MSI-H, MSI-L and MSS group, respectively. For D2S123, D17S250 and D5S346, heterozygosity was 80.8%, 74.1% and 57.7% and sizes of polymorphic variation range (PVR) were 207bp to 234bp, 140bp to 169bp and 109bp to 137bp, respectively. For D2S123 and D5S346, there was a bimodal distribution distinguishing the D17S250 from an indistinct trimodal or tetramodal distribution. CONCLUSION: MSI-H cases showed earlier onset and higher proportion of mucinous carcinomas. Mononucleotide BAT26 and BAT25 exhibited higher sensitivity than dinucleotides D2S123, D17S250 and D5S346 in the Chinese population. The dinucleotide markers were highly polymorphic with high percent of heterozygosity, great variation in repeat length and non-normal distribution in Chinese population from Jiangsu Province.


Assuntos
Adenocarcinoma Mucinoso/genética , Neoplasias Colorretais/genética , Marcadores Genéticos , Instabilidade de Microssatélites , Polimorfismo Genético , Adulto , China , Neoplasias Colorretais/etnologia , Reparo de Erro de Pareamento de DNA , Primers do DNA , Feminino , Heterozigoto , Humanos , Masculino , Repetições de Microssatélites/genética , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase Multiplex/métodos , Técnicas de Amplificação de Ácido Nucleico
13.
PLoS Med ; 17(9): e1003263, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32941469

RESUMO

BACKGROUND: Lynch syndrome (LS) predisposes to endometrial cancer (EC), colorectal cancer, and other cancers through inherited pathogenic variants affecting mismatch-repair (MMR) genes. Diagnosing LS in women with EC can reduce subsequent cancer mortality through colonoscopic surveillance and aspirin chemoprevention; it also enables cascade testing of relatives. A growing consensus supports LS screening in EC; however, the expected proportion of test positives, and optimal testing strategy is uncertain. Previous studies from insurance-based healthcare systems were limited by narrow selection criteria, failure to apply reference standard tests consistently, and poor conversion to definitive testing. The aim of this study was to establish the prevalence of LS and the diagnostic accuracy of LS testing strategies in an unselected EC population. METHODS AND FINDINGS: This was a prospective cross-sectional study carried out at a large United Kingdom gynaecological cancer centre between October 2015 and January 2017. Women diagnosed with EC or atypical hyperplasia (AH) were offered LS testing. Tumours underwent MMR immunohistochemistry (IHC), microsatellite instability (MSI), and targeted MLH1-methylation testing. Women <50 years, with strong family histories and/or indicative tumour molecular features, underwent MMR germline sequencing. Somatic MMR sequencing was performed when indicative molecular features were unexplained by LS or MLH1-hypermethylation. The main outcome measures were the prevalence of LS in an unselected EC population and the diagnostic accuracy of clinical and tumour testing strategies for risk stratifying women with EC for MMR germline sequencing. In total, 500 women participated in the study; only 2 (<1%) declined. Germline sequencing was indicated and conducted for 136 and 135 women, respectively. A total of 16/500 women (3.2%, 95% CI 1.8% to 5.1%) had LS, and 11 more (2.2%) had MMR variants of uncertain significance. Restricting testing to age <50 years, indicative family history (revised Bethesda guidelines or Amsterdam II criteria) or endometrioid histology alone would have missed 9/16 (56%), 8/13 (62%) or 9/13 (69%), and 5/16 (31%) cases of LS, respectively. In total 132/500 tumours were MMR deficient by IHC of which 83/132 (63%) had MLH1-hypermethylation, and 16/49 (33%) of the remaining patients had LS (16/132 with MMR deficiency, 12%). MMR-IHC with targeted MLH1-methylation testing was more discriminatory for LS than MSI with targeted methylation testing, with 100% versus 56.3% (16/16 versus 9/16) sensitivity (p = 0.016) and equal 97.5% (468/484) specificity; 64% MSI-H and 73% MMR deficient tumours unexplained by LS or MLH1-hypermethylation had somatic MMR mutations. The main limitation of the study was failure to conduct MMR germline sequencing for the whole study population, which means that the sensitivity and specificity of tumour triage strategies for LS detection may be overestimated, although the risk of LS in women with no clinical or tumour predictors is expected to be extremely low. CONCLUSIONS: In this study, we observed that age, family history, and histology are imprecise clinical correlates of LS-EC. IHC outperformed MSI for tumour triage and reliably identified both germline and somatic MMR mutations. The 3.2% proportion of LS-EC is similar to colorectal cancer, supporting unselected screening of EC for LS.


Assuntos
Neoplasias Colorretais Hereditárias sem Polipose/diagnóstico , Detecção Precoce de Câncer/métodos , Neoplasias do Endométrio/genética , Adulto , Neoplasias Colorretais Hereditárias sem Polipose/genética , Neoplasias Colorretais Hereditárias sem Polipose/patologia , Estudos Transversais , Metilação de DNA/genética , Reparo de Erro de Pareamento de DNA/genética , Neoplasias do Endométrio/diagnóstico , Feminino , Testes Genéticos/métodos , Humanos , Imuno-Histoquímica , Programas de Rastreamento/métodos , Instabilidade de Microssatélites , Pessoa de Meia-Idade , Estudos Prospectivos , Sensibilidade e Especificidade , Reino Unido
14.
Proc Natl Acad Sci U S A ; 117(38): 23597-23605, 2020 09 22.
Artigo em Inglês | MEDLINE | ID: mdl-32900932

RESUMO

Trinucleotide repeat (TNR) expansions cause nearly 20 severe human neurological diseases which are currently untreatable. For some of these diseases, ongoing somatic expansions accelerate disease progression and may influence age of onset. This new knowledge emphasizes the importance of understanding the protein factors that drive expansions. Recent genetic evidence indicates that the mismatch repair factor MutSß (Msh2-Msh3 complex) and the histone deacetylase HDAC3 function in the same pathway to drive triplet repeat expansions. Here we tested the hypothesis that HDAC3 deacetylates MutSß and thereby activates it to drive expansions. The HDAC3-selective inhibitor RGFP966 was used to examine its biological and biochemical consequences in human tissue culture cells. HDAC3 inhibition efficiently suppresses repeat expansion without impeding canonical mismatch repair activity. Five key lysine residues in Msh3 are direct targets of HDAC3 deacetylation. In cells expressing Msh3 in which these lysine residues are mutated to arginine, the inhibitory effect of RGFP966 on expansions is largely bypassed, consistent with the direct deacetylation hypothesis. RGFP966 treatment does not alter MutSß subunit abundance or complex formation but does partially control its subcellular localization. Deacetylation sites in Msh3 overlap a nuclear localization signal, and we show that localization of MutSß is partially dependent on HDAC3 activity. Together, these results indicate that MutSß is a key target of HDAC3 deacetylation and provide insights into an innovative regulatory mechanism for triplet repeat expansions. The results suggest expansion activity may be druggable and support HDAC3-selective inhibition as an attractive therapy in some triplet repeat expansion diseases.


Assuntos
Reparo de Erro de Pareamento de DNA/genética , Histona Desacetilases , Expansão das Repetições de Trinucleotídeos/genética , Acetilação/efeitos dos fármacos , Acrilamidas/farmacologia , Linhagem Celular , Células Cultivadas , Inibidores de Histona Desacetilases/farmacologia , Histona Desacetilases/genética , Histona Desacetilases/metabolismo , Humanos , Fenilenodiaminas/farmacologia
16.
Nat Genet ; 52(9): 958-968, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32747826

RESUMO

Certain mutagens, including the APOBEC3 (A3) cytosine deaminase enzymes, can create multiple genetic changes in a single event. Activity of A3s results in striking 'mutation showers' occurring near DNA breakpoints; however, less is known about the mechanisms underlying the majority of A3 mutations. We classified the diverse patterns of clustered mutagenesis in tumor genomes, which identified a new A3 pattern: nonrecurrent, diffuse hypermutation (omikli). This mechanism occurs independently of the known focal hypermutation (kataegis), and is associated with activity of the DNA mismatch-repair pathway, which can provide the single-stranded DNA substrate needed by A3, and contributes to a substantial proportion of A3 mutations genome wide. Because mismatch repair is directed towards early-replicating, gene-rich chromosomal domains, A3 mutagenesis has a high propensity to generate impactful mutations, which exceeds that of other common carcinogens such as tobacco smoke and ultraviolet exposure. Cells direct their DNA repair capacity towards more important genomic regions; thus, carcinogens that subvert DNA repair can be remarkably potent.


Assuntos
Citidina Desaminase/genética , Reparo de Erro de Pareamento de DNA/genética , Mutação/genética , Neoplasias/genética , Citosina Desaminase/genética , DNA de Cadeia Simples/genética , Genoma/genética , Humanos , Mutagênese/genética
17.
Nucleic Acids Res ; 48(16): 9124-9134, 2020 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-32756902

RESUMO

Substitutions in the exonuclease domain of DNA polymerase ϵ cause ultramutated human tumors. Yeast and mouse mimics of the most common variant, P286R, produce mutator effects far exceeding the effect of Polϵ exonuclease deficiency. Yeast Polϵ-P301R has increased DNA polymerase activity, which could underlie its high mutagenicity. We aimed to understand the impact of this increased activity on the strand-specific role of Polϵ in DNA replication and the action of extrinsic correction systems that remove Polϵ errors. Using mutagenesis reporters spanning a well-defined replicon, we show that both exonuclease-deficient Polϵ (Polϵ-exo-) and Polϵ-P301R generate mutations in a strictly strand-specific manner, yet Polϵ-P301R is at least ten times more mutagenic than Polϵ-exo- at each location analyzed. Thus, the cancer variant remains a dedicated leading-strand polymerase with markedly low accuracy. We further show that P301R substitution is lethal in strains lacking Polδ proofreading or mismatch repair (MMR). Heterozygosity for pol2-P301R is compatible with either defect but causes strong synergistic increases in the mutation rate, indicating that Polϵ-P301R errors are corrected by Polδ proofreading and MMR. These data reveal the unexpected ease with which polymerase exchange occurs in vivo, allowing Polδ exonuclease to prevent catastrophic accumulation of Polϵ-P301R-generated errors on the leading strand.


Assuntos
Reparo de Erro de Pareamento de DNA/genética , DNA Polimerase III/genética , DNA Polimerase II/genética , Neoplasias/enzimologia , Sequência de Aminoácidos/genética , Reparo do DNA/genética , Replicação do DNA/genética , Regulação da Expressão Gênica/genética , Humanos , Mutagênese/genética , Mutação/genética , Neoplasias/genética , Plasmídeos/genética , Saccharomyces cerevisiae/genética
18.
J Cancer Res Clin Oncol ; 146(10): 2651-2657, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32623573

RESUMO

PURPOSE: Patients with DNA mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) cancers are prone to response to programmed cell death-1 (PD-1) checkpoint inhibitors. Therefore, we explored the efficacy and safety of a PD-1 checkpoint inhibitor camrelizumab in advanced or metastatic solid tumour with dMMR/MSI-H. METHODS: Patients with dMMR/MSI-H advanced or metastatic solid tumours who had received at least one line of prior systemic chemotherapy were recruited. Camrelizumab was given intravenously 200 mg every 2-week treatment cycle. The primary endpoint was objective response rate according to Response Evaluation Criteria in Solid Tumours v1.1. RESULTS: Twelve patients were enrolled. As data cutoff, eight patients (66.7%, 95% CI 34.9-90.1) achieved objective response. Disease control rate reached 100% (95% CI 73.5-100). Progression-free survival rate at 12 months was 83.3% (95% CI 48.2-95.6), and overall survival rate at 12 months was 90% (95% CI 47.3-98.5). The most common treatment-related adverse events were reactive cutaneous capillary endothelial proliferation (100%), increased alanine aminotransferase (41.7%), and increased aspartate aminotransferase (41.7%). CONCLUSIONS: Camrelizumab provided durable objective response and disease control in pre-treated patients with dMMR/MSI-H advanced or metastatic solid tumour, being a promising treatment option for these patients.


Assuntos
Anticorpos Monoclonais Humanizados/uso terapêutico , Neoplasias/tratamento farmacológico , Neoplasias/genética , Adulto , Idoso , Anticorpos Monoclonais Humanizados/efeitos adversos , Antineoplásicos Imunológicos/efeitos adversos , Antineoplásicos Imunológicos/uso terapêutico , Reparo de Erro de Pareamento de DNA , Feminino , Humanos , Masculino , Instabilidade de Microssatélites , Pessoa de Meia-Idade , Metástase Neoplásica , Neoplasias/patologia , Receptor de Morte Celular Programada 1/antagonistas & inibidores , Intervalo Livre de Progressão , Estudos Prospectivos , Resultado do Tratamento
19.
BMC Med Genet ; 21(1): 141, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32611331

RESUMO

BACKGROUND: Lynch syndrome (LS), which is known as a hereditary cancer syndrome, is distinguished by microsatellite instability, represented by the altered number of repetitive sequences in the coding and/or non-coding region. Immunohistochemical staining (IHC) of DNA mismatch repair (MMR) proteins (e.g., MLH1, MSH2, MSH6, and PMS2) has been recognized as an useful technique for screening of LS. Previous study has shown that the assessment of IHC, however, requires specific caution due to variable staining patterns even without germline mutations in MMR genes. CASE PRESENTATION: A 48-year-old man, who had been treated for anaplastic astrocytoma, was referred to our department for the precise examination of progressing anemia. Whole-body examination revealed two advanced carcinomas in descending colon and stomach. A hypo-vascular mass lesion was detected in liver as well. Pathological diagnosis (on surgical specimens) was poorly differentiated adenocarcinoma in descending colon, moderately differentiated tubular adenocarcinoma in stomach, and liver metastasis, which is possibly from colon. It was suspected that this case would be Turcot's syndrome-type-1 due to its specific family history having two cases of colon cancer within the second relatives. Pathogenic frameshift mutations in codon 618 of MLH1 gene was identified. Immunohistochemical analyses (IHC) demonstrated complete loss of MLH1 immuno-expression as well as of PMS2 except for those in brain tumor. Although frameshift mutation was not found in MSH6 gene, histological expression of MSH6 was patchy in primary colon carcinoma and was completely lost in the metastatic site in liver. MSH6 expression in gastric carcinoma, a coincidental cancer in this case, was intact. An abnormal (C)8 region was identified by the cloned PCR of colon and liver tumors but not from gastric cancer. Frameshift mutation in a (C)8 tract in exon 5 of the MSH6 gene was also detected in liver metastasis. CONCLUSION: This case supports a plausible mechanism, proposed by a previous literature, for the reduced expression of MSH6 in a somatic mutation manner, which might preferentially happen in colon cancer rather than in stomach carcinoma in MLH1/PMS2-deficient type of Turcot's syndrome type 1.


Assuntos
Neoplasias Encefálicas/genética , Neoplasias do Colo/genética , Neoplasias Colorretais/genética , Proteínas de Ligação a DNA/imunologia , Predisposição Genética para Doença , Neoplasias Hepáticas/secundário , Mutação/genética , Síndromes Neoplásicas Hereditárias/genética , Adulto , Sequência de Bases , Reparo de Erro de Pareamento de DNA/genética , Feminino , Humanos , Masculino , Repetições de Microssatélites/genética , Pessoa de Meia-Idade , Linhagem
20.
PLoS One ; 15(7): e0235613, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32634176

RESUMO

Germline variants inactivating the mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2 cause Lynch syndrome that implies an increased cancer risk, where colon and endometrial cancer are the most frequent. Identification of these pathogenic variants is important to identify endometrial cancer patients with inherited increased risk of new cancers, in order to offer them lifesaving surveillance. However, several other genes are also part of the MMR pathway. It is therefore relevant to search for variants in additional genes that may be associated with cancer risk by including all known genes involved in the MMR pathway. Next-generation sequencing was used to screen 22 genes involved in the MMR pathway in constitutional DNA extracted from full blood from 199 unselected endometrial cancer patients. Bioinformatic pipelines were developed for identification and functional annotation of variants, using several different software tools and custom programs. This facilitated identification of 22 exonic, 4 UTR and 9 intronic variants that could be classified according to pathogenicity. This study has identified several germline variants in genes of the MMR pathway that potentially may be associated with an increased risk for cancer, in particular endometrial cancer, and therefore are relevant for further investigation. We have also developed bioinformatics strategies to analyse targeted sequencing data, including low quality data and genomic regions outside of the protein coding exons of the relevant genes.


Assuntos
Reparo de Erro de Pareamento de DNA , Neoplasias do Endométrio/patologia , Endonuclease PMS2 de Reparo de Erro de Pareamento/genética , Proteína 1 Homóloga a MutL/genética , Proteína 2 Homóloga a MutS/genética , Neoplasias Colorretais Hereditárias sem Polipose/genética , Neoplasias Colorretais Hereditárias sem Polipose/patologia , Variações do Número de Cópias de DNA , DNA de Neoplasias/sangue , DNA de Neoplasias/química , DNA de Neoplasias/metabolismo , Neoplasias do Endométrio/genética , Éxons , Feminino , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Íntrons , Fatores de Risco , Regiões não Traduzidas/genética
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