scholarly journals Acute benzo[a]pyrene exposure induced oxidative stress, neurotoxicity and epigenetic change in blood clam Tegillarca granosa

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Baoying Guo ◽  
Dan Feng ◽  
Zhongtian Xu ◽  
Pengzhi Qi ◽  
Xiaojun Yan
Keyword(s):  
Oxidative Stress ◽  
Dna Methylation ◽  
Marine Pollution ◽  
Organic Pollutant ◽  
Global Dna Methylation ◽  
Dna Hypomethylation ◽  
Tegillarca Granosa ◽  
Marine Bivalves ◽  
Multiple Biomarkers ◽  
Blood Clam

AbstractThe blood clam (Tegillarca granosa) is being developed into a model bivalve mollusc for assessing and monitoring marine pollution on the offshore seabed. However, the information on the response of blood clam to PAHs, an organic pollutant usually deposited in submarine sediment, remains limited. Herein, we employed multiple biomarkers, including histological changes, oxidative stress, neurotoxicity and global DNA methylation, to investigate the effects of 10 and 100 μg/L Bap exposure on the blood clams under laboratory conditions, as well as the potential mechanisms. Acute Bap exposure can induce significant morphological abnormalities in gills as shown through hematoxylin–eosin (H.E) staining, providing an intuitive understanding on the effects of Bap on the structural organization of the blood clams. Meanwhile, the oxidative stress was significantly elevated as manifested by the increase of antioxidants activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione-s-transferase (GST), lipid peroxidation (LPO) level and 8-hydroxy-2′-deoxyguanosine (8-OHdG) content. The neurotoxicity was also strengthened by Bap toxicity manifested as inhibited acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) activities. In addition, the global DNA methylation level was investigated, and a significant DNA hypomethylation was observed in Bap exposed the blood clam. The correlation analysis showed that the global DNA methylation was negatively correlated with antioxidants (SOD, CAT and POD) activities, but positively correlated choline enzymes (AChE and ChAT) activities. These results collectively suggested that acute Bap exposure can cause damage in gills structures in the blood clam possibly by generating oxidative stress and neurotoxicity, and the global DNA methylation was inhibited to increase the transcriptional expression level of antioxidants genes and consequently elevate antioxidants activities against Bap toxicity. These results are hoped to shed some new light on the study of ecotoxicology effect of PAHs on marine bivalves.

scholarly journals Effects of Acute Benzo[a]pyrene Exposure on Blood Clam Tegillarca Granosa: Histological Changes, Oxidative Stress, Neurotoxicity and DNA Hypomethylation

2021 ◽  
Author(s):  
Baoying Guo ◽  
Dan Feng ◽  
Pengzhi Qi ◽  
Zhi Liao ◽  
Xiaojun Yan
Keyword(s):  
Oxidative Stress ◽  
Dna Methylation ◽  
Marine Pollution ◽  
Organic Pollutant ◽  
Global Dna Methylation ◽  
Dna Hypomethylation ◽  
Glutathione S Transferase ◽  
Histological Changes ◽  
Multiple Biomarkers ◽  
Blood Clam

Abstract The blood clam is being developed into a model bivalve molluscs for assessing and monitoring marine pollution on the offshore seabed. However, the information on the response of blood clam to PAHs, an organic pollutant usually deposited in submarine sediment, remains limited. Herein, we employed multiple biomarkers, including histological changes, oxidative stress, neurotoxicity and global DNA methylation, to investigate the effects of Bap exposure under laboratory conditions on blood clams and its potential mechanisms. Acute Bap exposure can induce significant morphological abnormalities in gills as shown through hematoxylin-eosin (H.E) staining, providing an intuitive understanding on the effects of Bap on the structural organization of blood clams. Meanwhile, the oxidative stress was significantly elevated as manifested by the increase of antioxidants activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione-s-transferase (GST), lipid peroxidation (LPO) level and 8-hydroxy-2’-deoxyguanosine (8-OHdG) content. The neurotoxicity was also strengthened by Bap toxicity manifested as inhibited acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) activities. In addition, the global DNA methylation level was investigated, and a significant DNA hypomethylation was observed in Bap exposed blood clams. The correlation analysis showed that the global DNA methylation was negatively correlated with antioxidants (SOD, CAT and POD) activities, but positively correlated choline enzymes (AChE and ChAT) activities. These results collectively suggested that acute Bap exposure can cause damage in gills structures in blood clams possibly by generating oxidative stress and neurotoxicity, and the global DNA methylation was inhibited to increase the transcriptional expression level of antioxidants genes and consequently elevate antioxidants activities against Bap toxicity. These results are hoped to shed some new light on the study of ecotoxicology effect of PAHs on marine bivalves.

scholarly journals Artificial Light at Night of Different Spectral Compositions Differentially Affects Tumor Growth in Mice: Interaction With Melatonin and Epigenetic Pathways

2018 ◽  
Vol 25 (1) ◽  
pp. 107327481881290 ◽  
Author(s):  
A. E. Zubidat ◽  
B. Fares ◽  
F. Fares ◽  
A. Haim
Keyword(s):  
Breast Cancer ◽  
Dna Methylation ◽  
Tumor Growth ◽  
Short Wavelength ◽  
Global Dna Methylation ◽  
Artificial Light ◽  
Dna Hypomethylation ◽  
Light At Night ◽  
Cancer Burden ◽  
Melatonin Suppression

Lighting technology is rapidly advancing toward shorter wavelength illuminations that offer energy-efficient properties. Along with this advantage, the increased use of such illuminations also poses some health challenges, particularly breast cancer progression. Here, we evaluated the effects of artificial light at night (ALAN) of 4 different spectral compositions (500-595 nm) at 350 Lux on melatonin suppression by measuring its urine metabolite 6-sulfatoxymelatonin, global DNA methylation, tumor growth, metastases formation, and urinary corticosterone levels in 4T1 breast cancer cell-inoculated female BALB/c mice. The results revealed an inverse dose-dependent relationship between wavelength and melatonin suppression. Short wavelength increased tumor growth, promoted lung metastases formation, and advanced DNA hypomethylation, while long wavelength lessened these effects. Melatonin treatment counteracted these effects and resulted in reduced cancer burden. The wavelength suppression threshold for melatonin-induced tumor growth was 500 nm. These results suggest that short wavelength increases cancer burden by inducing aberrant DNA methylation mediated by the suppression of melatonin. Additionally, melatonin suppression and global DNA methylation are suggested as promising biomarkers for early diagnosis and therapy of breast cancer. Finally, ALAN may manifest other physiological responses such as stress responses that may challenge the survival fitness of the animal under natural environments.

scholarly journals Epigenome-wide DNA methylation and risk of breast cancer: a systematic review

BMC Cancer ◽  
2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Kaoutar Ennour-Idrissi ◽  
Dzevka Dragic ◽  
Francine Durocher ◽  
Caroline Diorio
Keyword(s):  
Breast Cancer ◽  
Dna Methylation ◽  
Breast Cancer Risk ◽  
Cancer Risk ◽  
Risk Of Bias ◽  
Global Dna Methylation ◽  
Dna Hypomethylation ◽  
Epigenetic Age ◽  
Potential Biomarker

Abstract Background DNA methylation is a potential biomarker for early detection of breast cancer. However, robust evidence of a prospective relationship between DNA methylation patterns and breast cancer risk is still lacking. The objective of this study is to provide a systematic analysis of the findings of epigenome-wide DNA methylation studies on breast cancer risk, in light of their methodological strengths and weaknesses. Methods We searched major databases (MEDLINE, EMBASE, Web of Science, CENTRAL) from inception up to 30th June 2019, for observational or intervention studies investigating the association between epigenome-wide DNA methylation (using the HM450k or EPIC BeadChip), measured in any type of human sample, and breast cancer risk. A pre-established protocol was drawn up following the Cochrane Reviews rigorous methodology. Study selection, data abstraction, and risk of bias assessment were performed by at least two investigators. A qualitative synthesis and systematic comparison of the strengths and weaknesses of studies was performed. Results Overall, 20 studies using the HM450k BeadChip were included, 17 of which had measured blood-derived DNA methylation. There was a consistent trend toward an association of global blood-derived DNA hypomethylation and higher epigenetic age with higher risk of breast cancer. The strength of associations was modest for global hypomethylation and relatively weak for most of epigenetic age algorithms. Differences in length of follow-up periods may have influenced the ability to detect associations, as studies reporting follow-up periods shorter than 10 years were more likely to observe an association with global DNA methylation. Probe-wise differential methylation analyses identified between one and 806 differentially methylated CpGs positions in 10 studies. None of the identified differentially methylated sites overlapped between studies. Three studies used breast tissue DNA and suffered major methodological issues that precludes any conclusion. Overall risk of bias was critical mainly because of incomplete control of confounding. Important issues relative to data preprocessing could have limited the consistency of results. Conclusions Global DNA methylation may be a short-term predictor of breast cancer risk. Further studies with rigorous methodology are needed to determine spatial distribution of DNA hypomethylation and identify differentially methylated sites associated with risk of breast cancer. Prospero registration number CRD42020147244

scholarly journals Folate metabolism modifies chromosomal damage induced by 1,3-butadiene: results from a match-up study in China and in vitro experiments

2021 ◽  
Vol 43 (1) ◽  
Author(s):  
Menglong Xiang ◽  
Zhi Wang ◽  
Peng Zou ◽  
Xi Ling ◽  
Guowei Zhang ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Methylenetetrahydrofolate Reductase ◽  
Micronucleus Assay ◽  
Folate Metabolism ◽  
Global Dna Methylation ◽  
Dependent Manner ◽  
Chromosomal Damage ◽  
Dna Hypomethylation ◽  
Exposed Workers ◽  
Tk6 Cells

Abstract Objectives To explore the role of folate metabolism in 1,3-Butadiene (BD)'s genotoxicity, we conducted a match-up study in BD-exposed workers in China to analyze the associations between the polymorphisms of methylenetetrahydrofolate reductase (MTHFR) and the chromosomal damage induced by BD exposure, and culture-based experiments in TK-6 cells to examine the global DNA methylation levels and chromosomal damage when exposed both to BD’s genotoxic metabolite, 1,2:3,4-diepoxybutane (DEB), and MTHFR’s direct catalytic product, 5-methyltetrahydrofolate (5-MTHF). Methods Cytokinesis block micronucleus assay (CBMN) was used to examine the chromosomal damage induced by BD or DEB. Poisson regression models were produced to quantify the relationship of chromosomal damage and genetic polymorphisms in the BD-exposed workers. Global DNA methylation levels in TK6 cells were examined using DNA Methylation Quantification Kit. Results We found that BD-exposed workers carrying MTHFR C677T CC (2.00 ± 2.00‰) (FR = 0.36, 95%CI: 0.20–0.67, P < 0.01) or MTHFR C677T CT (2.87 ± 1.98‰) (FR = 0.49, 95%CI: 0.32–0.77, P < 0.01) genotypes had significantly lower nuclear bud (NBUD) frequencies than those carrying genotype MTHFR 677 TT (5.33 ± 2.60‰), respectively. The results in TK6 cells showed that there was a significant increment in frequencies of micronucleus (MN), nucleoplasmic bridge (NPB) and nuclear bud (NBUD) with exposure to DEB at each 5-MTHF dose (ANOVA, P < 0.01). Additionally, there was a significant decrease in frequencies of MN, NPB and NBUD in DEB-exposed cultures with increasing concentration of 5-MTHF (ANOVA, P < 0.05). The levels of global DNA methylation were significantly decreased by DEB treatment in a dose-dependent manner within each 5-MTHF concentration in TK-6 cells (ANOVA, P < 0.01), and were significantly increased by 5-MTHF supplementation within each DEB concentration (ANOVA, P < 0.01). Conclusion We reported that folate metabolism could modify the association between BD exposure and chromosomal damage, and such effect may be partially mediated by DNA hypomethylation, and 5-MTHF supplementation could rescue it.

Global DNA Hypermethylation in Chronic Lymphocytic Leukemia Correlates with Progressive Disease.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 5006-5006
Author(s):  
Margaret K. Yu ◽  
Aniko Szabo ◽  
Hector Bergonia ◽  
Anna Senina ◽  
John D. Phillips
Keyword(s):  
Dna Methylation ◽  
Chronic Lymphocytic Leukemia ◽  
Progressive Disease ◽  
Lymphocytic Leukemia ◽  
Global Dna Methylation ◽  
Dna Hypomethylation ◽  
Physician Visits ◽  
Mutational Status ◽  
Trisomy 12 ◽  
One Year

Abstract Global DNA hypomethylation is observed in chronic lymphocytic leukemia, but methylation has not been correlated with clinical outcome. Although patient survival correlates with factors such as the mutational status of the immunoglobulin variable genes, karyotype abnormalities, Zap-70, and CD38 expression, none of these predictors have altered the way clinicians practice. We report interim results in the assessment of global DNA methylation as a predictor of aggressive disease in patients with chronic lymphocytic leukemia. Fourteen patients with chronic lymphocytic leukemia donated blood samples for DNA studies at the same time as blooddraws for their physician visits. All the treatments occurred within one year and the follow-ups were at least within 12 months except for one patient. We thus classified patients into two groups: those who required treatment within one year and those who did not. The cutoff in methylation level providing the smallest observed prediction error was 4.125%; it correctly predicted 5/6 patients not needing treatment within a year and 5/6 patients needing treatment. These observed classification rates were adjusted for the bias resulting from the optimal selection of the cutoff using bootstrap. The adjusted sensitivity and specificity were 74% and 80%, respectively. Asymptomatic patients with chronic lymphocytic leukemia tended to have lower levels of global DNA methylation (median 3.5%) compared to symptomatic patients (median 4.5%). In other words, high levels of global DNA methylation were associated with higher disease burden, corresponding with higher lymphocyte and white blood cell numbers. Five patients without immediate need for cytoreductive therapy were enrolled on a pilot treatment trial with low-dose cladribine, by subcutaneous injection. Three out of the five patients have had a clinical response, a secondary endpoint. Two of the patients have achieved a partial response, as defined by the NCI sponsored working group, with at least a three month follow-up after discontinuation of the drug. Of the two patients with stable or progressive disease on cladribine, their global DNA methylation levels were higher, correlating with more chemotherapy resistant disease. DNA methylation Levels in Patients with Chronic Lymphocytic Leukemia Age Sex %5-MedC Zap-70 CD-38 Rai Stage FISH Req Treatment (mos) FISH= fluorescence in situ hybridization; Zap-70 assessed by immunochemistry 51 M 5.045 positive positive 4 Del13q14 0.75 73 F 4.865 positive not assessed 4 not assessed 12+ 52 F 4.665 positive negative 2 Del13q14 2 57 M 4.62 negative negative 4 Del13q14 2 66 M 4.59 positive not assessed 4 Del13q14 (5/05) and Del 17p and Del 13q14 (7/05) 0.25 67 M 4.14 positive positive 4 Trisomy 12 10 47 M 4.055 negative negative 0 not assessed 12+ 59 M 3.9 negative negative 2 46XY 0 72 M 3.54 negative not assessed 0 not assessed 8+ 64 M 3.55 positive not assessed 1 Del13q14 12+ 70 F 3.47 not assessed negative 4 Trisomy 12 12+ 68 F 3.47 positive negative 2 not assessed 12+ 77 M 3.2 not assessed not assessed 0 not assessed 12+ DNA Methylation Levels in patients with Chronic Lymphocytic Leukemia DNA Methylation Levels in patients with Chronic Lymphocytic Leukemia

Repetitive DNA Hypomethylation in Multiple Myeloma

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2703-2703
Author(s):  
Sonia Fabris ◽  
Valentina Bollati ◽  
Laura Mosca ◽  
Valeria Pegoraro ◽  
Domenica Ronchetti ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Multiple Myeloma ◽  
Molecular Mechanisms ◽  
Plasma Cells ◽  
Human Cancer ◽  
Wide Spectrum ◽  
Rank Correlation ◽  
Global Dna Methylation ◽  
Dna Hypomethylation ◽  
Alu Elements

Abstract Multiple myeloma (MM) is a malignant proliferation of bone marrow plasma cells characterized by a wide spectrum of genetic and epigenetic changes. Global hypomethylation of repetitive genomic sequences such as long interspersed nuclear elements-1 (LINE-1) and Alu repetitive elements (approximately 500.000 and 1.4 million in the human genome) has been associated with chromosomal instability. Additionally, satellite alfa DNA (SAT-alpha DNA) hypomethylation has been reported to be associated to karyotypic instability in human cancer, possibly playing a role in centromere function. So far, the LINE-1/Alu and centromeric SAT-alpha DNA methylation patterns have not been investigated in the context of the different clinical and molecular MM subtypes. Global DNA methylation changes were investigated in a panel of 53 newly diagnosed, untreated MMs, 7 plasma cell leukemias (PCL) and 11 healthy subjects as controls. DNA was extracted from purified plasma cells, treated with bisulfite and analyzed by bisulfite-PCR and Pyrosequencing. Methylation of LINE-1 and Alu elements was shown to correlate with total 5mC content and thus used to estimate global DNA methylation. MMs showed a decrease of Alu (21.1%) and LINE-1 (70.0%) methylation average levels compared with controls (25.2% and 79.5% respectively). Lower median methylation levels were also found in centromeric SAT-alpha DNA of MMs (77.95%) compared to controls (89.5%). The median methylation level of PCLs was lower than MMs (16.7% versus 21.1% for Alu; 45.5% versus 70.0% for LINE-1; and 33.3% versus 77.9% for SATalpha DNA). Notably, a statistically significant association between SAT-alpha DNA and LINE-1 methylation (Spearman’s rank correlation, ρ = 0.94; P &lt; 0.001) was found in MM. The comparison between methylation pattern and different molecular MM subgroups by means of non parametric tests, revealed that LINE-1 and SAT-alpha DNA methylation was significantly lower in the nonhyperdiploid versus hyperdiploid (HD) tumors (P = 0.01 and 0.02 respectively). Alu and SAT-alpha were significantly lower in the MMs with t(4;14) (P = 0.02 and 0.004 respectively). Finally, in the context of translocation/cyclin D (TC) classification, a statistically significant differences inside the five different groups were found for SAT-alpha DNA methylation (P = 0.008, Kruskal-Wallis test). These findings may provide insights into the molecular mechanisms of MM pathogenesis and suggest that our approach may contribute toward a more exhaustive stratification of the disease.

Global DNA Methylation Status of CD4+ T-Cell Population in Mielodysplastic Syndromes.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4424-4424
Author(s):  
Angel Guerra-Moreno ◽  
Carlos Palacio ◽  
Noemí Martínez-Morgado ◽  
Margarita Ortega ◽  
Maida Navarrete ◽  
...  
Keyword(s):  
Dna Methylation ◽  
T Cells ◽  
Cd4 T Cells ◽  
Research Funding ◽  
Low Risk ◽  
The Other ◽  
Global Dna Methylation ◽  
Dna Hypomethylation ◽  
Dna Concentration ◽  
Other Hand

Abstract Abstract 4424 Introduction Recent studies have demonstrated that sequential administration of demethylating or immunomudulator agents have clinical efficacy in patients with myelodysplastic syndromes (MDS). Demethylating agents induce an optimal re-expression of epigenetically silenced tumor suppressor genes. However, the global DNA demethylation observed in malignant cells during treatment doesn't guarantee a better prognosis, suggesting the presence of others important unknown factors. On the other hand, global DNA hypomethylation of CD4+ T-cells have been related with autoimmune pathology diseases like systemic lupus erythematosus (SLE). The aim of the present study is to establish the degree of the global DNA methylation in CD4+ T-cells in MDS patients and their potential dysfunction. Patients and methods Eight MDS patients with low-risk, according to IPSS (between 0 and 1), diagnosed by cytology, cytogenetics and immunophenotype, and 4 healthy donors have been studied. Peripheral blood mononuclear cells were obtained by ficoll density gradient. Negative CD4+ selection followed by a positive selection were performed using the MACS system (Miltenyi). In patients with CD34+ cells expressing CD4+ antigen, lymphocyte isolation was done using a FACSAria sorter (BD Biosciences). Purity of CD4+ T-cells was higher than 90% in all cases. Cell DNA extraction was carried out with the QIAamp DNA blood mini kit (Qiagen). DNA concentration and 260:280 absorbance ratios were calculated with a NanoDrop ND-1000 spectrophotometer (NanoDrop Technologies). Global DNA methylation content was measured by means of an ELISA using an anti-5-mC mAb (Calbiochem) 1/400 diluted. Before proceeding with patient samples, an optimal DNA concentration to evaluate global methylation levels was established. With this purpose, a reference DNA sample of purified CD4+ T cells (374 ng/ml) was twofold serially diluted in TE (starting at 1:1000 dilution) to observe the kinetics of our ELISA. The best DNA concentration range was 0.025–0.05 ng/ml (Figure 1). Methylation indices (MI) were calculated by getting the ratio between optical density (OD) and DNA concentration for each sample. To minimize experimental variability between plates a reference sample was included in each run. Control and patient MI were corrected by establishing the ratio with the reference MI. Results The global DNA methylation indices obtained by ELISA (Figure 2) displayed that most of MDS patients studied presented a global DNA hypomethylation in CD4+ T-cells, and 3 with IPSS 0 showed and important decrease. Conclusion These preliminary results showed that there are low-risk MDS patients with hypomethylation in CD4+ T-cells. This observation may suggest an autoimmune component in these malignancies as the one described in SLE. To address this hypothesis we are increasing the number of patients studied to all IPSS categories, to test if this phenomenon is highly represented in MDS. In the other hand, we are studying the presence of autoimmune-related factors, like the expression of integrins adhesive receptors such as LFA-1, in patients showed CD4 T-cells hypomethylation. Disclosures: Guerra-Moreno: Celgene: Research Funding. Vallespi:Celgene: Research Funding.

Impact of Oxidative Stress on Global DNA Methylation in Sperms of Infertile Men

2014 ◽  
Vol 9 (2) ◽  
pp. 12-17
Author(s):  
Anam R. Al-Salihi ◽  
Estabraq A. Al-Wasiti ◽  
Mayssaa A. Al-Hilaly
Keyword(s):  
Oxidative Stress ◽  
Dna Methylation ◽  
Global Dna Methylation ◽  
Infertile Men

scholarly journals Quantification of Global DNA Methylation in Canine Melanotic and Amelanotic Oral Mucosal Melanomas and Peripheral Blood Leukocytes From the Same Patients With OMM: First Study

2021 ◽  
Vol 8 ◽  
Author(s):  
Nayra Villar Scattone ◽  
Tatiane Moreno Ferrarias Epiphanio ◽  
Karine Germano Caddrobi ◽  
Juliana Shimara Pires Ferrão ◽  
Francisco Javier Hernandez-Blazquez ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Peripheral Blood ◽  
High Performance ◽  
Global Dna Methylation ◽  
Image Analysis System ◽  
Peripheral Blood Leukocytes ◽  
Dna Hypomethylation ◽  
Blood Leukocytes ◽  
Tissue Samples ◽  
Analysis System

Oral mucosal melanomas (OMMs) are aggressive and resistant cancers of high importance in veterinary oncology. Amelanotic OMM produces comparatively less melanin and is considered to be more aggressive than melanotic OMM. Global DNA methylation profiles with hypomethylated or hypermethylated patterns have both been associated with aggressive neoplasms; however, global DNA hypomethylation seems to correlate to higher aggressiveness. Accordingly, global DNA methylation in peripheral blood leukocytes has been investigated to understand the role of systemic or environmental factors in cancer development. This study aimed to quantify global DNA methylation in canine melanotic and amelanotic OMM samples and in the peripheral blood leukocytes of the same dogs. Tumor tissue samples were collected from 38 dogs, of which 19 were melanotic and 19 were amelanotic OMM. These were submitted to immunohistochemistry (IHC) with anti-5-methylcytosine (5mC) and anti-Ki67 primary antibodies. Ki67- and 5mC-positive nuclei were manually scored with the help of an image analysis system. Peripheral blood samples were collected from 18 among the 38 OMM-bearing dogs and from 7 additional healthy control dogs. Peripheral blood leukocytes were isolated from the 25 dogs, and DNA was extracted and analyzed by high-performance liquid chromatography (HPLC) for global DNA methylation. The pattern of global DNA methylation in both canine melanotic and amelanotic OMM indicated higher percentages of weakly or negatively stained nuclei in most of the OMM cells, presuming predominant global DNA hypomethylation. In addition, Ki67 counts in amelanotic OMM were significantly higher than those in melanotic OMM (p &lt; 0.001). Global DNA methylation different immunostaining patterns (strong, weak or negative) correlated with Ki67 scores. Global DNA methylation in circulating leukocytes did not differ between the 9 melanotic and 9 amelanotic OMM or between the 18 OMM-bearing dogs and the 7 healthy dogs. This study provides new information on canine melanotic and amelanotic OMM based on global DNA methylation and cell proliferation.

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