Association between DNA methyltransferases 3B gene polymorphisms and the susceptibility to acute myeloid leukemia in Chinese Han population

Epigenetic regulation in hematopoiesis and its implications in the targeted therapy of hematologic malignancies

Hematologic malignancies are one of the most common cancers, and the incidence has been rising in recent decades. The clinical and molecular features of hematologic malignancies are highly heterogenous, and some hematologic malignancies are incurable, challenging the treatment, and prognosis of the patients. However, hematopoiesis and oncogenesis of hematologic malignancies are profoundly affected by epigenetic regulation. Studies have found that methylation-related mutations, abnormal methylation profiles of DNA, and abnormal histone deacetylase expression are recurrent in leukemia and lymphoma. Furthermore, the hypomethylating agents and histone deacetylase inhibitors are effective to treat acute myeloid leukemia and T-cell lymphomas, indicating that epigenetic regulation is indispensable to hematologic oncogenesis. Epigenetic regulation mainly includes DNA modifications, histone modifications, and noncoding RNA-mediated targeting, and regulates various DNA-based processes. This review presents the role of writers, readers, and erasers of DNA methylation and histone methylation, and acetylation in hematologic malignancies. In addition, this review provides the influence of microRNAs and long noncoding RNAs on hematologic malignancies. Furthermore, the implication of epigenetic regulation in targeted treatment is discussed. This review comprehensively presents the change and function of each epigenetic regulator in normal and oncogenic hematopoiesis and provides innovative epigenetic-targeted treatment in clinical practice.

The influence of DNMT3A and DNMT3B gene polymorphisms on acute myeloid leukemia risk in a Moroccan population

Acute myeloid leukemia (AML) is a very complex disease that is linked to environmental, genetic and epigenetic factors. Several Studies have found that aberrations in DNA methylation process play a crucial role in leukemogenesis. The aim of this case control study was to evaluate the association between rs1569686, rs2424913 polymorphisms located in DNMT3B gene and rs7590760 polymorphism located in DNMT3A gene and AML risk in a Moroccan population.

MATERIALS AND METHODS

The present study was conducted in 142 cases of AML and 179 control subjects from the Moroccan population. Genomic DNA was isolated from whole blood samples by salting-out method and the genotype of the three polymorphisms was determined by the PCR-RFLP technique.

RESULTS

The study results indicated that rs1569686 polymorphism was significantly associated with the risk of AML in dominant model (OR=1.72, 95 % CI 1.01-2.95, P=0.04), but not in recessive model. In stratified analysis by gender, statistically significant association between the rs2424913 CT genotype and AML was found among males (OR=2.05, 95 % CI 1.00-4.19, P=0.04). Similarly, the rs1569686 TT genotype was associated with an increase risk of AML (OR=3.21, 95 % CI 1.15-8. 98, P=0.02), this association was also found under dominant genetic model (OR=2.47, 95 % CI 1.07-5. 67, P=0.03) among males. However, the rs2424913 polymorphism was not associated with AML.

CONCLUSION

Our findings have shown that rs1569686 polymorphism might be a risk factor of AML in males. While, the rs2424913 polymorphism was not associated with AML. Further studies with a large sample size are needed to validate our results.

Methyltransferase DNMT3B in leukemia

DNA methyltransferases (DNMTs) are highly conserved DNA-modifying enzymes that play important roles in epigenetic regulation and they are involved in cell proliferation, differentiation, and apoptosis. In mammalian cells, three active DNMTs have been identified: DNMT1 acts as a maintenance methyltransferase to replicate preexisting methylation patterns, whereas DNMT3A and DNMT3B primarily act as de novo methyltransferases that are responsible for establishing DNA methylation patterns by adding a methyl group to cytosine bases. The expression of DNMT3B is widespread in a variety of hematological cells and it is altered in each type of leukemia, which is associated with its pathogenesis, progression, treatment, and prognosis. Here, we review current information on DNMT3B in leukemia, including its expression, single-nucleotide polymorphisms, mutations, regulation, function, and clinical value for anti-leukemic therapy and prognosis.

Oncogenic Roles and Inhibitors of DNMT1, DNMT3A, and DNMT3B in Acute Myeloid Leukaemia

Epigenetic alteration has been proposed to give rise to numerous classic hallmarks of cancer. Impaired DNA methylation plays a central role in the onset and progression of several types of malignancies, and DNA methylation is mediated by DNA methyltransferases (DNMTs) consisting of DNMT1, DNMT3A, and DNMT3B. DNMTs are frequently implicated in the pathogenesis and aggressiveness of acute myeloid leukaemia (AML) patients. In this review, we describe and discuss the oncogenic roles of DNMT1, DNMT3A, and DNMT3B in AML. The clinical response predictive roles of DNMTs in clinical trials utilising hypomethylating agents (azacitidine and decitabine) in AML patients are presented. Novel hypomethylating agent (guadecitabine) and experimental DNMT inhibitors in AML are also discussed. In summary, hypermethylation of tumour suppressors mediated by DNMT1 or DNMT3B contributes to the progression and severity of AML (except MLL-AF9 and inv(16)(p13;q22) AML for DNMT3B), while mutation affecting DNMT3A represents an early genetic lesion in the pathogenesis of AML. In clinical trials of AML patients, expression of DNMTs is downregulated by hypomethylating agents while the clinical response predictive roles of DNMT biomarkers remain unresolved. Finally, nucleoside hypomethylating agents have continued to show enhanced responses in clinical trials of AML patients, and novel non-nucleoside DNMT inhibitors have demonstrated cytotoxicity against AML cells in pre-clinical settings.

Association of DNMT3B -283T>C polymorphism with risk of lung and gastric cancer: a case-control study and a meta-analysis

PURPOSE

To investigate the association of DNMT3B -283T>C polymorphism with the risk of lung or gastric cancer, which was followed by a meta-analysis.

METHODS

The genotyping of -283T>C was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and was confirmed by sequencing.

RESULTS

The results of this case-control study showed that -283T>C was not associated with the risk of lung or gastric cancer, and further stratified analysis according to age, gender, smoking status, and alcohol status confirmed the present finding. However, data from a meta-analysis in the Asian population revealed a significant association between -283T>C and lung cancer risk in the allelic model (C vs. T: odds ratio [OR] = 1.28, 95% confidence interval [CI], 1.06-1.55, p = 0.01) and two genetic models (CC vs. TC: OR = 1.29, 95% CI, 1.04-1.59, p = 0.02; CC vs. TC + TT: OR = 1.30, 95% CI, 1.06-1.60, p = 0.01).

CONCLUSIONS

These results provided evidence that the DNMT3B -283T>C polymorphism might significantly contribute to the lung cancer risk in the Asian population, but not the gastric cancer risk in the Chinese population.

Aberrant DNA methylation of acute myeloid leukemia and colorectal cancer in a Chinese pedigree with a MLL3 germline mutation

Unlike genetic aberrations, epigenetic alterations do not modify the deoxyribonucleic acid (DNA) coding sequence and can be reversed pharmacologically. Identifying a particular epigenetic alteration such as abnormal DNA methylation may provide better understanding of cancers and improve current therapy. In a Chinese pedigree with colorectal carcinoma and acute myeloid leukemia, we examined the genome-wide DNA methylation level of cases and explored the role of methylation in pathogenesis and progression. DNA methylation status in the four cases, which all harbor a MLL3 germline mutation, differed from that of the normal control, and hypermethylation was more prevalent. Also, more CpG sites were hypermethylated in the acute-phase AML patient than in the AML patient in remission. Fifty-nine hyper- or hypomethylated genes were identified as common to all four cases. Genome-wide DNA methylation analysis demonstrated that differentially methylated sites among acute myeloid leukemia and colorectal carcinoma cases and the control were in both promoters (CpG island) and gene body regions (shelf/shore areas). Hypermethylation was more prevalent in cancer cases. The study supports the suggestion that the level of DNA methylation changes in AML progression.

Genetic variants involved in oxidative stress, base excision repair, DNA methylation, and folate metabolism pathways influence myeloid neoplasias susceptibility and prognosis

Myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) share common features: elevated oxidative stress, DNA repair deficiency, and aberrant DNA methylation. We performed a hospital-based case-control study to evaluate the association in variants of genes involved in oxidative stress, folate metabolism, DNA repair, and DNA methylation with susceptibility and prognosis of these malignancies. To that end, 16 SNPs (one per gene: CAT, CYBA, DNMT1, DNMT3A, DNMT3B, GPX1, KEAP1, MPO, MTRR, NEIL1, NFE2F2, OGG1, SLC19A1, SOD1, SOD2, and XRCC1) were genotyped in 191 patients (101 MDS and 90 AML) and 261 controls. We also measured oxidative stress (reactive oxygen species/total antioxidant status ratio), DNA damage (8-hydroxy-2'-deoxyguanosine), and DNA methylation (5-methylcytosine) in 50 subjects (40 MDS and 10 controls). Results showed that five genes (GPX1, NEIL1, NFE2L2, OGG1, and SOD2) were associated with MDS, two (DNMT3B and SLC19A1) with AML, and two (CYBA and DNMT1) with both diseases. We observed a correlation of CYBA TT, GPX1 TT, and SOD2 CC genotypes with increased oxidative stress levels, as well as NEIL1 TT and OGG1 GG genotypes with higher DNA damage. The 5-methylcytosine levels were negatively associated with DNMT1 CC, DNMT3A CC, and MTRR AA genotypes, and positively with DNMT3B CC genotype. Furthermore, DNMT3A, MTRR, NEIL1, and OGG1 variants modulated AML transformation in MDS patients. Additionally, DNMT3A, OGG1, GPX1, and KEAP1 variants influenced survival of MDS and AML patients. Altogether, data suggest that genetic variability influence predisposition and prognosis of MDS and AML patients, as well AML transformation rate in MDS patients. © 2016 Wiley Periodicals, Inc.

Association of DNMT3B -283 T > C and -579 G > T polymorphisms with decreased cancer risk: evidence from a meta-analysis

Numerous studies have explored the association of polymorphisms in the DNA methyltransferase 3b (DNMT3B) gene with the risk of different types of cancer, but yielded controversial results. Therefore, we performed a meta-analysis to derive a more precise estimation of the association between three widely-studied DNMT3B polymorphisms and overall cancer susceptibility. Totally, 4 studies with 1234 cases and 1337 controls were eligible for DNMT3B -283 T > C (rs6087990), 19 studies with 5332 cases and 7407 controls for DNMT3B -149 C > T (rs2424913), and 14 studies with 3933 cases and 4436 controls for DNMT3B -579 G > T (rs1569686). Overall, DNMT3B -283 T > C was associated with a significantly reduced risk of overall cancer (T vs. C: OR = 0.84, 95% CI = 0.71-0.99, P = 0.039). Likewise, the association of DNMT3B -579 G > T with a decreased overall cancer risk was also observed (heterozygous: OR = 0.77, 95% CI = 0.65-0.91, P = 0.003 and dominant: OR = 0.80, 95% CI = 0.66-0.98, P = 0.029); in the subgroup analysis, the protective association was found for lung and colorectal cancer, but not for head and neck cancer. Finally, the pooled analysis showed no significant association between DNMT3B -149 C > T and overall cancer susceptibility, but stratification analysis indicated that this polymorphism decreased the risk of developing head and neck cancer (heterozygous: OR = 0.73, 95% CI = 0.59-0.90, P = 0.003 and dominant: OR = 0.76, 95% CI = 0.61-0.93, P = 0.009). In conclusion, our results suggested that DNMT3B -283 T > C and DNMT3B -579 G > T but DNMT3B -149 C > T might confer protection against overall cancer risk. In the future, large and well-designed case-control studies are needed to validate our findings.

Systematic evaluation of cancer risk associated with DNMT3B polymorphisms

PURPOSE

The aim of our study is to provide a precise quantification for the association between DNA methyltransferase 3B (DNMT3B) variations (rs2424913 C/T, rs1569686 G/T, rs6087990 T/C and rs2424908 T/C) and the risk of cancer.

METHODS

We performed a systematic literature review and assessed the methodological quality of included case-control designed studies based on Newcastle-Ottawa Scale. Pooled odds ratios (ORs) and corresponding 95% confidence intervals (95% CIs) were calculated to assess the strengths of the associations.

RESULTS

We identified 34 studies for pooled analyses. Overall, the results demonstrated that rs2424913 polymorphism was significantly associated with negative cancer risk in the African population (CT vs TT: OR 0.10, 95% CI 0.02-0.63, P = 0.01; CT+CC vs TT: OR 0.14, 95% CI 0.03-0.76, P = 0.02), and the rs1569686 polymorphism was significantly associated with a subtly decreased cancer risk (GT vs TT: OR 0.80, 95% CI 0.72-0.90, P < 0.01; GT+GG vs TT: OR 0.84, 95% CI 0.76-0.94, P < 0.01), particularly in the Asian population (GT vs TT: OR 0.79, 95% CI 0.66-0.96, P < 0.01) and in colorectal cancer subgroup (G vs T: OR 0.69, 95% CI 0.54-0.88, P < 0.01). In addition, the rs6087990 polymorphism was associated with decreased risk in Asian population (T vs C: OR 0.77, 95% CI 0.62-0.96, P = 0.02). Similarly, the rs2424908 polymorphism was observed as a protective factor for cancer in the Asian population (CT+CC vs TT: OR 0.79, 95% CI 0.66-0.95, P = 0.01).

CONCLUSIONS

DNMT3B polymorphisms might be associated with decreased cancer risk especially in the Asian population and for colorectal cancer. Further multicentric studies are still needed to confirm the results.

Association of DNA methyltransferases 3A and 3B polymorphisms, and plasma folate levels with the risk of urothelial carcinoma

BACKGROUND

Interindividual genetic variations of human DNA methyltransferases (DNMTs), which involve the methyl donor from the folate-related one-carbon metabolism pathway, are hypothesized as a risk factor for urothelial carcinoma (UC). Therefore, we evaluated the role of gene-environment interaction in UC carcinogenesis.

METHODS

A hospital-based case-control study was conducted by recruiting 192 patients with UC and 381 controls. Their plasma folate levels were measured using a competitive immunoassay kit. In addition, DNMT3A -448A>G and DNMT3B -579G>T genotyping was evaluated using a polymerase chain reaction-restriction fragment length polymorphism technique. Multivariate logistic regression and 95% confidence intervals (CIs) were applied to estimate the UC risk.

RESULTS

We observed that patients with UC exhibited a higher prevalence rate of folate insufficiency (folate levels ≤6 ng/mL) compared with the controls (35.94% and 18.37%, respectively). Furthermore, folate levels were higher in the prevalent UC patients than in the incident UC patients. However, folate insufficiency was similarly associated with a nearly two-fold increase in the risk of UC regardless of the UC patient group. In addition, the frequencies of the variant alleles for DNMT3A and DNMT3B were 0.80 and 0.92, respectively, and no association was observed with UC risk. However, participants with a variant homozygous genotype of DNMT3B -579G>T and folate insufficiency or with high cumulative cigarette smoking exhibited an increased risk of UC.

CONCLUSION

Overall, environmental factors may contribute more significantly to UC carcinogenesis compared with genetic susceptibility. Future studies should investigate other polymorphisms of DNMT3A and DNMT3B to determine genetic susceptibility.