RESUMO
DNA base damage is a major source of oncogenic mutations1. Such damage can produce strand-phased mutation patterns and multiallelic variation through the process of lesion segregation2. Here we exploited these properties to reveal how strand-asymmetric processes, such as replication and transcription, shape DNA damage and repair. Despite distinct mechanisms of leading and lagging strand replication3,4, we observe identical fidelity and damage tolerance for both strands. For small alkylation adducts of DNA, our results support a model in which the same translesion polymerase is recruited on-the-fly to both replication strands, starkly contrasting the strand asymmetric tolerance of bulky UV-induced adducts5. The accumulation of multiple distinct mutations at the site of persistent lesions provides the means to quantify the relative efficiency of repair processes genome wide and at single-base resolution. At multiple scales, we show DNA damage-induced mutations are largely shaped by the influence of DNA accessibility on repair efficiency, rather than gradients of DNA damage. Finally, we reveal specific genomic conditions that can actively drive oncogenic mutagenesis by corrupting the fidelity of nucleotide excision repair. These results provide insight into how strand-asymmetric mechanisms underlie the formation, tolerance and repair of DNA damage, thereby shaping cancer genome evolution.
Assuntos
Dano ao DNA , Reparo do DNA , DNA Polimerase Dirigida por DNA , DNA , Mutagênese , Mutação , Animais , Humanos , Camundongos , Alquilação/efeitos da radiação , Linhagem Celular , DNA/química , DNA/genética , DNA/metabolismo , DNA/efeitos da radiação , Adutos de DNA/química , Adutos de DNA/genética , Adutos de DNA/metabolismo , Adutos de DNA/efeitos da radiação , Dano ao DNA/genética , Dano ao DNA/efeitos da radiação , Reparo do DNA/genética , Reparo do DNA/fisiologia , Replicação do DNA , DNA Polimerase Dirigida por DNA/metabolismo , Mutagênese/genética , Mutagênese/efeitos da radiação , Mutação/genética , Mutação/efeitos da radiação , Neoplasias/genética , Transcrição Gênica , Raios Ultravioleta/efeitos adversosRESUMO
Covalent DNA-protein cross-links (DPCs) are toxic DNA lesions that block replication and require repair by multiple pathways. Whether transcription blockage contributes to the toxicity of DPCs and how cells respond when RNA polymerases stall at DPCs is unknown. Here we find that DPC formation arrests transcription and induces ubiquitylation and degradation of RNA polymerase II. Using genetic screens and a method for the genome-wide mapping of DNA-protein adducts, DPC sequencing, we discover that Cockayne syndrome (CS) proteins CSB and CSA provide resistance to DPC-inducing agents by promoting DPC repair in actively transcribed genes. Consequently, CSB- or CSA-deficient cells fail to efficiently restart transcription after induction of DPCs. In contrast, nucleotide excision repair factors that act downstream of CSB and CSA at ultraviolet light-induced DNA lesions are dispensable. Our study describes a transcription-coupled DPC repair pathway and suggests that defects in this pathway may contribute to the unique neurological features of CS.
Assuntos
Síndrome de Cockayne , DNA Helicases , Enzimas Reparadoras do DNA , Reparo do DNA , Proteínas de Ligação a Poli-ADP-Ribose , RNA Polimerase II , Humanos , Síndrome de Cockayne/genética , Síndrome de Cockayne/metabolismo , Síndrome de Cockayne/patologia , Adutos de DNA/metabolismo , Adutos de DNA/genética , Dano ao DNA , DNA Helicases/metabolismo , DNA Helicases/genética , Enzimas Reparadoras do DNA/metabolismo , Enzimas Reparadoras do DNA/genética , Reparo por Excisão , Proteínas de Ligação a Poli-ADP-Ribose/metabolismo , Proteínas de Ligação a Poli-ADP-Ribose/genética , Receptores de Interleucina-17 , RNA Polimerase II/metabolismo , RNA Polimerase II/genética , Fatores de Transcrição , Transcrição Gênica , Ubiquitinação , Raios UltravioletaRESUMO
The PHYTOME study investigated the effect of consuming processed meat products on outcomes related to colorectal cancer risk without testing the impact of genetic variability on these responses. This research aims to elucidate the genetic impact on apparent total N-nitroso compound (ATNC) excretion, colonic DNA adduct formation, ex vivo-induced DNA damage, and gene expression changes in colon biopsies of healthy participants. Through a systematic literature review, candidate polymorphisms were selected and then detected using TaqMan and PCR analysis. The effect of genotype on study outcomes was determined via a linear mixed model and analysis of variance. Machine learning was used to evaluate relative allele importance concerning genotoxic responses, which established a ranking of the most protective alleles and a combination of genotypes (gene scores). Participants were grouped by GSTM1 genotype and differentially expressed genes (DEGs), and overrepresented biological pathways were compared between groups. Stratifying participants by ten relevant genes revealed significant variations in outcome responses. After consumption of processed red meat, variations in NQO1 and COMT impacted responses in ATNC levels (µmol/L) (+9.56 for wildtype vs. heterozygous) and DNA adduct levels (pg/µg DNA) (+1.26 for variant vs. wildtype and +0.43 for variant vs. heterozygous), respectively. After phytochemicals were added to the meat, GSTM1 variation impacted changes in DNA adduct levels (-6.12 for deletion vs. wildtype). The gene scores correlated with these responses and DEGs were identified by GSTM1 genotype. The altered pathways specific to the GSTM1 wildtype group included 'metabolism', 'cell cycle', 'vitamin D receptor', and 'metabolism of water-soluble vitamins and co-factors'. Genotype impacted both the potential genotoxicity of processed red meat and the efficacy of protective phytochemical extracts.
Assuntos
Produtos da Carne , Carne Vermelha , Humanos , Produtos da Carne/análise , Adutos de DNA/genética , Adutos de DNA/metabolismo , Transcriptoma , Dano ao DNA , Carne/análise , Carne Vermelha/análise , Compostos Nitrosos/metabolismo , Colo/metabolismoRESUMO
Dietary exposure to aflatoxin B1 (AFB1) is a recognized risk factor for developing hepatocellular carcinoma. The mutational signature of AFB1 is characterized by high-frequency base substitutions, predominantly G>T transversions, in a limited subset of trinucleotide sequences. The 8,9-dihydro-8-(2,6-diamino-4-oxo-3,4-dihydropyrimid-5-yl-formamido)-9-hydroxyaflatoxin B1 (AFB1-FapyGua) has been implicated as the primary DNA lesion responsible for AFB1-induced mutations. This study evaluated the mutagenic potential of AFB1-FapyGua in four sequence contexts, including hot- and cold-spot sequences as apparent in the mutational signature. Vectors containing site-specific AFB1-FapyGua lesions were replicated in primate cells and the products of replication were isolated and sequenced. Consistent with the role of AFB1-FapyGua in AFB1-induced mutagenesis, AFB1-FapyGua was highly mutagenic in all four sequence contexts, causing G>T transversions and other base substitutions at frequencies of ~80%-90%. These data suggest that the unique mutational signature of AFB1 is not explained by sequence-dependent fidelity of replication past AFB1-FapyGua lesions.
Assuntos
Neoplasias Hepáticas , Mutagênicos , Animais , Mutagênicos/toxicidade , Aflatoxina B1/toxicidade , Adutos de DNA/genética , Guanina , Mutagênese , Neoplasias Hepáticas/patologia , Imidazóis/efeitos adversosRESUMO
The catalytic cycle of topoisomerase 2 (TOP2) enzymes proceeds via a transient DNA double-strand break (DSB) intermediate termed the TOP2 cleavage complex (TOP2cc), in which the TOP2 protein is covalently bound to DNA. Anticancer agents such as etoposide operate by stabilizing TOP2ccs, ultimately generating genotoxic TOP2-DNA protein cross-links that require processing and repair. Here, we identify RAD54 like 2 (RAD54L2) as a factor promoting TOP2cc resolution. We demonstrate that RAD54L2 acts through a novel mechanism together with zinc finger protein associated with tyrosyl-DNA phosphodiesterase 2 (TDP2) and TOP2 (ZATT/ZNF451) and independent of TDP2. Our work suggests a model wherein RAD54L2 recognizes sumoylated TOP2 and, using its ATPase activity, promotes TOP2cc resolution and prevents DSB exposure. These findings suggest RAD54L2-mediated TOP2cc resolution as a potential mechanism for cancer therapy resistance and highlight RAD54L2 as an attractive candidate for drug discovery.
Assuntos
Adutos de DNA , Proteínas de Ligação a DNA , Humanos , Adutos de DNA/genética , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Diester Fosfórico Hidrolases/genética , DNA Topoisomerases Tipo II/genética , DNA/genética , Instabilidade Genômica , DNA Helicases/genéticaRESUMO
Sequence context influences structural characteristics and repair of DNA adducts, but there is limited information on how epigenetic modulation affects conformational heterogeneity and bypass of DNA lesions. Lesions derived from the environmental pollutant 2-nitrofluorene have been extensively studied as chemical carcinogenesis models; they adopt a sequence-dependent mix of two significant conformers: major groove binding (B) and base-displaced stacked (S). We report a conformation-dependent bypass of the N-(2'-deoxyguanosin-8-yl)-7-fluoro-2-aminofluorene (dG-FAF) lesion in epigenetic sequence contexts (d[5'-CTTCTC#G*NCCTCATTC-3'], where C# is C or 5-methylcytosine (5mC), G* is G or G-FAF, and N is A, T, C or G). FAF-modified sequences with a 3' flanking pyrimidine were better bypassed when the 5' base was 5mC, whereas sequences with a 3' purine exhibited the opposite effect. The conformational basis behind these variations differed; for -CG*C- and -CG*T-, bypass appeared to be inversely correlated with population of the duplex-destabilizing S conformer. On the other hand, the connection between conformation and a decrease in bypass for flanking purines in the 5mC sequences relative to C was more complex. It could be related to the emergence of a disruptive non-S/B conformation. The present work provides novel conformational insight into how 5mC influences the bypass efficiency of bulky DNA damage.
Assuntos
Adutos de DNA , Fluorenos , Sequência de Bases , Conformação de Ácido Nucleico , Fluorenos/química , Adutos de DNA/genética , Epigênese Genética , Desoxiguanosina/químicaRESUMO
DNA damage causes genomic instability underlying many diseases, with traditional analytical approaches providing minimal insight into the spectrum of DNA lesions in vivo. Here we used untargeted chromatography-coupled tandem mass spectrometry-based adductomics (LC-MS/MS) to begin to define the landscape of DNA modifications in rat and human tissues. A basis set of 114 putative DNA adducts was identified in heart, liver, brain, and kidney in 1-26-month-old rats and 111 in human heart and brain by 'stepped MRM' LC-MS/MS. Subsequent targeted analysis of these species revealed species-, tissue-, age- and sex-biases. Structural characterization of 10 selected adductomic signals as known DNA modifications validated the method and established confidence in the DNA origins of the signals. Along with strong tissue biases, we observed significant age-dependence for 36 adducts, including N2-CMdG, 5-HMdC and 8-Oxo-dG in rats and 1,N6-ϵdA in human heart, as well as sex biases for 67 adducts in rat tissues. These results demonstrate the potential of adductomics for discovering the true spectrum of disease-driving DNA adducts. Our dataset of 114 putative adducts serves as a resource for characterizing dozens of new forms of DNA damage, defining mechanisms of their formation and repair, and developing them as biomarkers of aging and disease.
Assuntos
Adutos de DNA , DNA , Animais , Feminino , Humanos , Masculino , Ratos , Cromatografia Líquida/métodos , DNA/química , Adutos de DNA/genética , Roedores , Espectrometria de Massas em Tandem/métodosRESUMO
Studies have indicated that air pollution, including surface-level ozone (O3), can significantly influence the risk of chronic diseases. To better understand the carcinogenic mechanisms of air pollutants and identify predictive disease biomarkers, we examined the association between traffic-related pollutants with DNA methylation alterations and bulky DNA adducts, two biomarkers of carcinogen exposure and cancer risk, in the peripheral blood of 140 volunteers-95 traffic police officers, and 45 unexposed subjects. The DNA methylation and adduct measurements were performed by bisulfite-PCR and pyrosequencing and 32P-postlabeling assay. Airborne levels of benzo(a)pyrene [B(a)P], carbon monoxide, and tropospheric O3 were determined by personal exposure biomonitoring or by fixed monitoring stations. Overall, air pollution exposure was associated with a significant reduction (1.41 units) in global DNA methylation (95% C.I. -2.65-0.04, p = 0.026). The decrement in ALU repetitive elements was greatest in the policemen working downtown (95% C.I. -3.23--0.49, p = 0.008). The DNA adducts were found to be significantly increased (0.45 units) in the municipal officers with respect to unexposed subjects (95% C.I. 0.02-0.88, p = 0.039), mainly in those who were controlling traffic in downtown areas (95% C.I. 0.39-1.29, p < 0.001). Regression models indicated an increment of ALU methylation at higher B(a)P concentrations (95% C.I. 0.03-0.60, p = 0.032). Moreover, statistical models showed a decrement in ALU methylation and an increment of DNA damage only above the cut-off value of 30 µg/m3 O3. A significant increment of 0.73 units of IL-6 gene methylation was also found in smokers with respect to non-smokers. Our results highlighted the role of air pollution on epigenetic alterations and genotoxic effects, especially above the target value of 30 µg/m3 surface-level O3, supporting the necessity for developing public health strategies aimed to reduce traffic-related air pollution molecular alterations.
Assuntos
Poluentes Atmosféricos , Poluição do Ar , Ozônio , Humanos , Adutos de DNA/genética , Ozônio/toxicidade , Dano ao DNA , Poluentes Atmosféricos/toxicidade , Poluentes Atmosféricos/análise , Poluição do Ar/efeitos adversos , Poluição do Ar/análise , BiomarcadoresRESUMO
Acetaldehyde (AA), a by-product of ethanol metabolism, is acutely toxic due to its ability to react with various biological molecules including DNA and proteins, which can greatly impede key processes such as replication and transcription and lead to DNA damage. As such AA is classified as a group 1 carcinogen by the International Agency for Research on Cancer (IARC). Previous in vitro studies have shown that AA generates bulky adducts on DNA, with signature guanine-centered (GGâTT) mutations. However, due to its weak mutagenicity, short chemical half-life, and the absence of powerful genetic assays, there is considerable variability in reporting the mutagenic effects of AA in vivo. Here, we used an established yeast genetic reporter system and demonstrate that AA treatment is highly mutagenic to cells and leads to strand-biased mutations on guanines (GâT) at a high frequency on single stranded DNA (ssDNA). We further demonstrate that AA-derived mutations occur through lesion bypass on ssDNA by the translesion polymerase Polζ. Finally, we describe a unique mutation signature for AA, which we then identify in several whole-genome and -exome sequenced cancers, particularly those associated with alcohol consumption. Our study proposes a key mechanism underlying carcinogenesis by acetaldehyde-mutagenesis of single-stranded DNA.
Assuntos
Acetaldeído , DNA de Cadeia Simples , Acetaldeído/química , Acetaldeído/metabolismo , Acetaldeído/toxicidade , DNA/genética , Adutos de DNA/genética , Dano ao DNA , Replicação do DNA , DNA de Cadeia Simples/genética , Guanina/metabolismo , Mutagênese , Mutagênicos , MutaçãoRESUMO
The allure of tobacco smoking is linked to the instant gratification provided by inhaled nicotine. Unfortunately, tobacco curing and burning generates many mutagens including more than 70 carcinogens. There are two types of mutagens and carcinogens in tobacco smoke (TS): direct DNA damaging carcinogens and procarcinogens, which require metabolic activation to become DNA damaging. Recent studies provide three new insights on TS-induced DNA damage. First, two major types of TS DNA damage are induced by direct carcinogen aldehydes, cyclic-1,N2-hydroxy-deoxyguanosine (γ-OH-PdG) and α-methyl-1, N2-γ-OH-PdG, rather than by the procarcinogens, polycyclic aromatic hydrocarbons and aromatic amines. Second, TS reduces DNA repair proteins and activity levels. TS aldehydes also prevent procarcinogen activation. Based on these findings, we propose that aldehydes are major sources of TS induce DNA damage and a driving force for carcinogenesis. E-cigarettes (E-cigs) are designed to deliver nicotine in an aerosol state, without burning tobacco. E-cigarette aerosols (ECAs) contain nicotine, propylene glycol and vegetable glycerin. ECAs induce O6-methyl-deoxyguanosines (O6-medG) and cyclic γ-hydroxy-1,N2--propano-dG (γ-OH-PdG) in mouse lung, heart and bladder tissues and causes a reduction of DNA repair proteins and activity in lungs. Nicotine and nicotine-derived nitrosamine ketone (NNK) induce the same types of DNA adducts and cause DNA repair inhibition in human cells. After long-term exposure, ECAs induce lung adenocarcinoma and bladder urothelial hyperplasia in mice. We propose that E-cig nicotine can be nitrosated in mouse and human cells becoming nitrosamines, thereby causing two carcinogenic effects, induction of DNA damage and inhibition of DNA repair, and that ECA is carcinogenic in mice. Thus, this article reviews the newest literature on DNA adducts and DNA repair inhibition induced by nicotine and ECAs in mice and cultured human cells, and provides insights into ECA carcinogenicity in mice.
Assuntos
Sistemas Eletrônicos de Liberação de Nicotina , Poluição por Fumaça de Tabaco , Aerossóis , Aldeídos , Animais , Carcinogênese/genética , Carcinógenos/toxicidade , Adutos de DNA/genética , Dano ao DNA , Reparo do DNA/genética , Humanos , Camundongos , Mutagênicos , Nicotina/análise , Fumaça , Nicotiana/efeitos adversos , Poluição por Fumaça de Tabaco/análiseRESUMO
4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is one of the key tobacco-specific nitrosamines that plays an important role in human lung carcinogenesis. Repeated dose inhalation toxicity data on NNK, particularly relevant to cigarette smoking, however, is surprisingly limited. Hence, there is a lack of direct information available on the carcinogenic and potential non-carcinogenic effects of NNK via inhalational route exposure. In the present study, the subchronic inhalation toxicity of NNK was evaluated in Sprague Dawley rats. Both sexes (9-10 weeks age; 23 rats/sex/group) were exposed by nose-only inhalation to air, vehicle control (75% propylene glycol), or 0.2, 0.8, 3.2, or 7.8 mg/kg body weight (BW)/day of NNK (NNK aerosol concentrations: 0, 0, 0.0066, 0.026, 0.11, or 0.26 mg/L air) for 1 h/day for 90 consecutive days. Toxicity was evaluated by assessing body weights; food consumption; clinical pathology; histopathology; organ weights; blood, urine, and tissue levels of NNK, its major metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), and their glucuronides (reported as total NNK, tNNK, and total NNAL, tNNAL, respectively); tissue levels of the DNA adduct O6-methylguanine; blood and bone marrow micronucleus (MN) frequency; and bone marrow DNA strand breaks (comet assay). The results showed that NNK exposure caused multiple significant adverse effects, with the most sensitive endpoint being non-neoplastic lesions in the nose. Although the genotoxic biomarker O6-methylguanine was detected, genotoxicity from NNK exposure was negative in the MN and comet assays. The Lowest-Observed-Adverse-Effect-Level (LOAEL) was 0.8 mg/kg BW/day or 0.026 mg/L air of NNK for 1 h/day for both sexes. The No-Observed-Adverse-Effect-Level (NOAEL) was 0.2 mg/kg BW/day or 0.0066 mg/L air of NNK for 1 h/day for both sexes. The results of this study provide new information relevant to assessing the human exposure hazard of NNK.
Assuntos
Exposição por Inalação/efeitos adversos , Nicotiana/toxicidade , Nitrosaminas/toxicidade , Animais , Fumar Cigarros/efeitos adversos , Adutos de DNA/genética , Dano ao DNA/efeitos dos fármacos , Feminino , Humanos , Masculino , Testes para Micronúcleos , Nível de Efeito Adverso não Observado , Nariz/efeitos dos fármacos , Nariz/patologia , Ratos , Ratos Sprague-Dawley , Fumaça/efeitos adversos , Nicotiana/químicaRESUMO
Adductomics novel and emerging discipline in the toxicological research emphasizes on adducts formed by reactive chemical agents with biological molecules in living organisms. Development in analytical methods propelled the application and utility of adductomics in interdisciplinary sciences. This review endeavors to add a new dimension where comprehensive insights into diverse applications of adductomics in addressing some of society's pressing challenges are provided. Also focuses on diverse applications of adductomics include: forecasting risk of chronic diseases triggered by reactive agents and predicting carcinogenesis induced by tobacco smoking; assessing chemical agents' toxicity and supplementing genotoxicity studies; designing personalized medication and precision treatment in cancer chemotherapy; appraising environmental quality or extent of pollution using biological systems; crafting tools and techniques for diagnosis of diseases and detecting food contaminants; furnishing exposure profile of the individual to electrophiles; and assisting regulatory agencies in risk assessment of reactive chemical agents. Characterizing adducts that are present in extremely low concentrations is an exigent task and more over absence of dedicated database to identify adducts is further exacerbating the problem of adduct diagnosis. In addition, there is scope of improvement in sample preparation methods and data processing software and algorithms for accurate assessment of adducts.
Assuntos
Adutos de DNA/genética , Poluentes Ambientais/toxicidade , Expossoma , Mutagênicos/toxicidade , Animais , Monitoramento Ambiental/métodos , HumanosRESUMO
Mutation patterns of DNA adducts, such as mutational spectra and signatures, are useful tools for diagnostic and prognostic purposes. Mutational spectra of carcinogens derive from three sources: adduct formation, replication bypass, and repair. Here, we consider the repair aspect of 1,N6-ethenoadenine (εA) by the 2-oxoglutarate/Fe(II)-dependent AlkB family enzymes. Specifically, we investigated εA repair across 16 possible sequence contexts (5'/3' flanking base to εA varied as G/A/T/C). The results revealed that repair efficiency is altered according to sequence, enzyme, and strand context (ss- versus ds-DNA). The methods can be used to study other aspects of mutational spectra or other pathways of repair.
Assuntos
Adutos de DNA/química , Reparo do DNA/fisiologia , Adutos de DNA/genética , Reparo do DNA/genética , Mutação , OxirreduçãoRESUMO
PURPOSE: DNA, the hereditary material of a human cell generally exists as Watson-Crick base paired double-stranded B-DNA. Studies suggest that DNA can also exist in non-B forms, such as four stranded G-quadruplexes (G4 DNA). Recently, our studies revealed that the regions of DNA that can fold into G-quadruplex structures are less sensitive to ionizing radiation (IR) compared to B-DNA. Importantly, we reported that the planar G-quartet of a G4 structure is shielded from radiation induced DNA breaks, while the single- and double-stranded DNA regions remained susceptible. Thus, in the present study, we investigate whether telomeric repeat DNA present at the end of telomere, known to fold into G4 DNA can protect from radiation induced damages including strand breaks, oxidation of purines and bulky adduct formation on DNA. MATERIALS AND METHODS: For plasmid irradiation assay, plasmids containing human telomeric repeat DNA sequence TTAGGG (0.8 kb or 1.8 kb) were irradiated with increasing doses of IR along with appropriate control plasmids and products were resolved on 1% agarose gel. Radioprotection was evaluated based on extent of conversion of supercoiled to nicked or linear forms of the DNA following irradiation. Formation of G-quadruplex structure on supercoiled DNA was evaluated based on circular dichroism (CD) spectroscopy studies. Cleavage of radiation induced oxidative damage and extent of formation of nicks was further evaluated using base and nucleotide excision repair proteins. RESULTS: Results from CD studies showed that the plasmid DNA harboring human telomeric repeats (TTAGGG) can fold into G-quadruplex DNA structures. Further, results showed that human telomeric repeat sequence when present on a plasmid can protect the plasmid DNA against IR induced DNA strand breaks, unlike control plasmids bearing random DNA sequence. CONCLUSIONS: Human telomeric repeat sequence when present on plasmids can fold into G-quadruplex DNA structures, and can protect the DNA against IR induced DNA strand breaks and oxidative damage. These results in conjunction with our previous studies suggest that telomeric repeat sequence imparts less sensitivity to IR and thus telomeres of chromosomes are protected from radiation.
Assuntos
Adutos de DNA/genética , Adutos de DNA/efeitos da radiação , Quadruplex G/efeitos da radiação , Raios gama/efeitos adversos , Estresse Oxidativo/genética , Estresse Oxidativo/efeitos da radiação , Telômero/genética , Sequência de Bases , Humanos , Telômero/efeitos da radiaçãoRESUMO
1,3-Butadiene (BD) is a known human carcinogen used in the synthetic polymer industry and also found in cigarette smoke, automobile exhaust and wood burning smoke. BD is metabolically activated by cytochrome P450 monooxygenases (CYP) 2E1 and 2A6 to 3,4-epoxy-1-butene (EB), which can be detoxified by GST-catalyzed glutathione conjugation or hydrolysis. We have previously observed ethnic differences in urinary levels of EB-mercapturic acids in white, Japanese American and Native Hawaiian smokers. In the present study, similar analyses were extended to urinary BD-DNA adducts. BD-induced N7-(1-hydroxy-3-buten-2-yl) guanine (EB-GII) adducts were quantified in urine samples obtained from smokers and non-smokers belonging to three racial/ethnic groups: white, Japanese American and Native Hawaiian. After adjusting for sex, age, nicotine equivalents, body mass index and batch, we found that Japanese American smokers excreted significantly higher amounts of urinary EB-GII than whites [1.45 (95% confidence interval: 1.12-1.87) versus 0.68 (95% confidence interval: 0.52-0.85) fmol/ml urine, P = 4 × 10-5]. Levels of urinary EB-GII in Native Hawaiian smokers were not different from those in whites [0.67 (95% confidence interval: 0.51-0.84) fmol/ml urine, P = 0.938]. There were no racial/ethnic differences in urinary EB-GII adduct levels in non-smokers. Racial/ethnic differences in urinary EB-GII adduct levels in smokers could not be explained by GSTT1 gene deletion or CYP2A6 enzymatic activity. Urinary EB-GII adduct levels in smokers were significantly associated with concentrations of BD metabolite dihyroxybutyl mercapturic acid. Overall, our results reveal that urinary EB-GII adducts in smokers differ across racial/ethnic groups. Future studies are required to understand genetic and epigenetic factors that may be responsible for these differences.
Assuntos
Butadienos/toxicidade , Citocromo P-450 CYP2A6/genética , Citocromo P-450 CYP2E1/genética , Adutos de DNA/efeitos dos fármacos , Acetilcisteína/urina , Adulto , Idoso , Asiático/genética , Carcinógenos/metabolismo , Carcinógenos/toxicidade , Adutos de DNA/genética , Adutos de DNA/urina , Compostos de Epóxi/efeitos adversos , Compostos de Epóxi/urina , Etnicidade/genética , Feminino , Glutationa Transferase/genética , Humanos , Masculino , Pessoa de Meia-Idade , Havaiano Nativo ou Outro Ilhéu do Pacífico/genética , Fumaça/efeitos adversos , Fumantes , Espectrometria de Massas por Ionização por Electrospray , Produtos do Tabaco/efeitos adversos , Emissões de Veículos/toxicidade , População Branca/genéticaRESUMO
Sperm DNA contains a range of DNA base damage that can arise, in part, from exposure to methylating agents. However, the effects are not fully characterized and so the aim of this study was to investigate associations between semen quality and the levels of N7-methyldeoxyguanosine (N7-MedG), a marker of exposure to methylating agents, and other markers of DNA damage and DNA methylation. Sperm samples were collected from 105 men attending an assisted reproduction clinic as part of a couple undergoing treatment for infertility and semen quality assessed manually according to WHO guidelines. Semen levels of N7-MedG, quantified by immunoslotblot, were significantly higher in men with sperm concentration < 15 × 106/ml (p ≤ 0.01), semen volume < 1.5 ml (p ≤ 0.05) and also in men with any aspect of semen quality below WHO reference levels (p ≤ 0.001). Measures of neutral Comet DNA damage were correlated with semen quality in a univariate analysis but not after adjustment for N7-MedG levels. Sperm concentration was negatively associated with % methylation at the gene for DAZL but no other marker of global or gene-specific DNA methylation. Results support the hypothesis that the known toxic and DNA damaging properties of alkylating agent exposure may have direct deleterious consequences on semen quality.
Assuntos
Metilação de DNA , DNA/genética , Desoxiguanosina/análogos & derivados , Infertilidade Masculina/diagnóstico , Infertilidade Masculina/genética , Proteínas de Ligação a RNA/genética , Adulto , Alquilantes/toxicidade , Biomarcadores/metabolismo , Ensaio Cometa , DNA/metabolismo , Adutos de DNA/genética , Adutos de DNA/metabolismo , Dano ao DNA , Desoxiguanosina/metabolismo , Expressão Gênica , Humanos , Infertilidade Masculina/metabolismo , Infertilidade Masculina/patologia , Masculino , Pessoa de Meia-Idade , Proteínas de Ligação a RNA/metabolismo , Sêmen/citologia , Sêmen/metabolismo , Análise do Sêmen/métodos , Contagem de Espermatozoides , Espermatozoides/metabolismo , Espermatozoides/patologiaRESUMO
Chemical carcinogenesis is focused on the formation of DNA adducts, a form of DNA damage caused by covalent binding of a chemical moiety to DNA. The detection of carcinogen-DNA adducts in human tissues, along with demonstration of mutagenicity/carcinogenicity in experimental systems, and validation of adducts as biomarkers of environmental exposure and indicators of cancer risk in molecular epidemiological studies suggests a pivotal role of DNA adducts in cancer development. However, accurate measurement of DNA adducts in varied biological samples is challenging. Advances in mass spectrometry have prompted the development of DNA adductome analysis, an emerging method that simultaneously screens for multiple DNA adducts and provides relevant structural information. In this review, we summarize the basic principle and applications of DNA adductome analysis that would contribute to the elucidation of the environmental causes of cancer. Based on parallel developments in several fields, including next-generation sequencing, we describe a new approach used to explore cancer etiology, which integrates analyses of DNA adductome data and mutational signatures derived from whole-genome/exome sequencing.
Assuntos
Adutos de DNA/genética , DNA/genética , Exposição Ambiental/efeitos adversos , Neoplasias/etiologia , Neoplasias/genética , Animais , Dano ao DNA/genética , Humanos , Mutação/genéticaRESUMO
PURPOSE: Here we investigated the impact of oncolytic herpes simplex virus (HSV) treatment on cisplatin sensitivity of platinum-resistant ovarian cancer, and the impact of the combination on immunotherapy. EXPERIMENTAL DESIGN: Therapeutic efficacy of the combination was assessed in platinum-resistant human and murine ovarian cancer peritoneal metastatic mouse models (n = 9-10/group). RNA sequencing along with flow cytometry of splenocytes from treated mice was employed to examine the effect of antitumor immune response (n = 3/group). Anti-PD-1 antibody was performed to evaluate impact on checkpoint inhibition in vivo. RESULTS: Gene Ontology pathway analysis uncovered disruption of cellular extracellular vesicle (EV)-related pathways in infected cells (FDR = 2.97E-57). Mechanistically, we identified reduced expression of transporters expressed on EV implicated in cisplatin efflux. The increased cisplatin retention led to increased cisplatin-DNA adducts, which resulted in micronuclei and the subsequent activation of cGAS-STING pathway with a significant activation of innate immune cells and translated to an increase in antitumor immunity and efficacy. In mice bearing platinum-resistant ovarian cancer, we also observed a feedback induction of PD-L1 on tumor cells, which sensitized combination-treated mice to anti-PD-1 immune checkpoint therapy. CONCLUSIONS: To our knowledge, this is the first report to show HSV-induced cisplatin retention in infected cells. The consequential increased damaged DNA was then expelled from cells as micronuclei which resulted in induction of inflammatory responses and education of antitumor immunity. The combination therapy also created an environment that sensitized tumors to immune checkpoint therapy.
Assuntos
Cisplatino/uso terapêutico , Terapia Viral Oncolítica/métodos , Neoplasias Ovarianas/terapia , Animais , Antineoplásicos/uso terapêutico , Linhagem Celular Tumoral , Células Cultivadas , Terapia Combinada , Adutos de DNA/genética , Adutos de DNA/imunologia , Modelos Animais de Doenças , Feminino , Herpesvirus Humano 1/fisiologia , Humanos , Imunoterapia/métodos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos NOD , Camundongos Knockout , Camundongos SCID , Neoplasias Ovarianas/genética , Neoplasias Ovarianas/virologia , Transdução de Sinais/genética , Transdução de Sinais/imunologia , Resultado do Tratamento , Ensaios Antitumorais Modelo de Xenoenxerto/métodosRESUMO
Reactive aldehydes arise as by-products of metabolism and are normally cleared by multiple families of enzymes. We find that mice lacking two aldehyde detoxifying enzymes, mitochondrial ALDH2 and cytoplasmic ADH5, have greatly shortened lifespans and develop leukemia. Hematopoiesis is disrupted profoundly, with a reduction of hematopoietic stem cells and common lymphoid progenitors causing a severely depleted acquired immune system. We show that formaldehyde is a common substrate of ALDH2 and ADH5 and establish methods to quantify elevated blood formaldehyde and formaldehyde-DNA adducts in tissues. Bone-marrow-derived progenitors actively engage DNA repair but also imprint a formaldehyde-driven mutation signature similar to aging-associated human cancer mutation signatures. Furthermore, we identify analogous genetic defects in children causing a previously uncharacterized inherited bone marrow failure and pre-leukemic syndrome. Endogenous formaldehyde clearance alone is therefore critical for hematopoiesis and in limiting mutagenesis in somatic tissues.
Assuntos
Álcool Desidrogenase/genética , Aldeído-Desidrogenase Mitocondrial/genética , Formaldeído/sangue , Leucemia/genética , Adolescente , Aldeídos/sangue , Animais , Criança , Pré-Escolar , Adutos de DNA/genética , Dano ao DNA/efeitos dos fármacos , Reparo do DNA/efeitos dos fármacos , Feminino , Formaldeído/toxicidade , Hematopoese/genética , Células-Tronco Hematopoéticas/metabolismo , Humanos , Lactente , Leucemia/sangue , Leucemia/patologia , Masculino , Camundongos , Mutação/genética , Especificidade por SubstratoRESUMO
Stalled replication forks can be restarted and repaired by RAD51-mediated homologous recombination (HR), but HR can also perform post-replicative repair after bypass of the obstacle. Bulky DNA adducts are important replication-blocking lesions, but it is unknown whether they activate HR at stalled forks or behind ongoing forks. Using mainly BPDE-DNA adducts as model lesions, we show that HR induced by bulky adducts in mammalian cells predominantly occurs at post-replicative gaps formed by the DNA/RNA primase PrimPol. RAD51 recruitment under these conditions does not result from fork stalling, but rather occurs at gaps formed by PrimPol re-priming and resection by MRE11 and EXO1. In contrast, RAD51 loading at double-strand breaks does not require PrimPol. At bulky adducts, PrimPol promotes sister chromatid exchange and genetic recombination. Our data support that HR at bulky adducts in mammalian cells involves post-replicative gap repair and define a role for PrimPol in HR-mediated DNA damage tolerance.