Methylation Of Tumor Suppressor Genes Research Articles

Promoter methylation as biomarkers for diagnosis of melanoma: A systematic review and meta-analysis.

Melanoma is one of the most common skin cancer that is characterized by rapid growth, early metastasis, high malignant, and mortality. Accumulating evidence demonstrated that promoter methylation of tumor-suppressor genes is implicated in the pathogenesis of melanoma. In the current study, we performed a meta-analysis to identify promising methylation biomarkers in the diagnosis of melanoma. We carried out a systematic literature search using Pubmed, Embase, and ISI web knowledge database and found that gene promoter methylation of 50 genes was reported to be associated with the risk of melanoma. Meta-analysis revealed that hypermethylation of claudin 11 (CLDN11; odds ratio [OR], 16.82; 95% confidence interval [CI], 1.97-143.29; p = 0.010), O-6-methylguanine-DNA methyltransferase (MGMT; OR, 5.59; 95% CI, 2.51-12.47; p < 0.0001), cyclin-dependent kinase inhibitor 2A (p16; OR, 6.57; 95% CI, 2.19-19.75; p = 0.0008), retinoic acid receptorβ (RAR-β2; OR, 24.31; 95% CI, 4.58-129.01; p = 0.0002), and Ras association domain family member (RASSF1A; OR, 9.35; 95% CI, 4.73-18.45; p < 0.00001) was significantly higher in melanoma patients compared with controls. CLDN11 (OR, 14.52; 95% CI, 1.84-114.55; p = 0.01), MGMT (OR, 8.08; 95% CI, 1.84-35.46; p = 0.006), p16 (OR, 9.44; 95% CI, 2.68-33.29; p = 0.0005), and RASSF1A (OR, 7.72; 95% CI, 1.05-56.50; p = 0.04) hypermethylation was significantly increased in primary melanoma compared with controls. Methylation frequency of CLDN11 (OR, 25.56; 95% CI, 2.32-281.66; p = 0.008), MGMT (OR, 4.64; 95% CI, 1.98-10.90; p = 0.0004), p16 (OR, 4.31; 95% CI, 1.33-13.96; p = 0.01), and RASSF1A (OR, 10.10; 95% CI, 2.87-35.54; p = 0.0003) was significantly higher in metastasis melanoma compared with controls. These findings indicated that CLDN11, MGMT, p16, RAR-β2, and RASSF1A hypermethylation is a risk factor and a potential biomarker for melanoma. CLDN11, MGMT, p16, and RASSF1A promoter methylation may take part in the development of melanoma and become useful biomarkers in the early diagnosis of the disease.

HYPERMETHYLATED DNA AS BIOMARKER FOR NASOPHARYNGEAL CANCER DETECTION

Backgroud: Nasopharyngeal carcinoma (NPC) is a malignancy with remarkable geographic and distribution worldwide, toward in Southern China and Southern Asia. In addition to Epstein–Barr virus infection, environmental carcinogens, the development of NPC involves the cumulative genetic as well as epigenetic alteration. More recently, it has been reported that DNA hypermethylation, an epigenetic mechanism, that occurred by the addition of a methyl group at 5’ position of the pyrimidine ring of cytosine residues at CpG islands, has been considered as the cause of nasopharyngeal tumorigenesis. In recent years, many reports have focused on the identification, evaluation of aberrant methylation of target tumor suppressor genes’ promoters, such as RASSF1A, BLU, DLEC, RARβ, p16, p15, p14, and MGMT in the NPC development.Objective: We focused on the description and exemplification of the DNA hypermethylation changes in nasopharyngeal carcinoma.Conclusion: we highlighted the DNA hypermethylation as a potential biomarker applied in monitoring, screening, and early diagnosis for cancer of nasopharynx.

Clinical, Pathological, and Molecular Characteristics of CpG Island Methylator Phenotype in Colorectal Cancer: A Systematic Review and Meta-analysis

BACKGROUND: CpG island methylator phenotype (CIMP) tumors, comprising 20% of colorectal cancers, are associated with female sex, age, right-sided location, and BRAF mutations. However, other factors potentially associated with CIMP have not been robustly examined. This meta-analysis provides a comprehensive assessment of the clinical, pathologic, and molecular characteristics that define CIMP tumors. METHODS: We conducted a comprehensive search of the literature from January 1999 through April 2018 and identified 122 articles, on which comprehensive data abstraction was performed on the clinical, pathologic, molecular, and mutational characteristics of CIMP subgroups, classified based on the extent of DNA methylation of tumor suppressor genes assessed using a variety of laboratory methods. Associations of CIMP with outcome parameters were estimated using pooled odds ratio or standardized mean differences using random-effects model. RESULTS: We confirmed prior associations including female sex, older age, right-sided tumor location, poor differentiation, and microsatellite instability. In addition to the recognized association with BRAF mutations, CIMP was also associated with PIK3CA mutations and lack of mutations in KRAS and TP53. Evidence of an activated immune response was seen with high rates of tumor-infiltrating lymphocytes (but not peritumoral lymphocytes), Crohn-like infiltrates, and infiltration with Fusobacterium nucleatum bacteria. Additionally, CIMP tumors were associated with advance T-stage and presence of perineural and lymphovascular invasion. CONCLUSION: The meta-analysis highlights key features distinguishing CIMP in colorectal cancer, including molecular characteristics of an active immune response. Improved understanding of this unique molecular subtype of colorectal cancer may provide insights into prevention and treatment.

Methylation of BRCA1 and MGMT genes in white blood cells are transmitted from mothers to daughters

BackgroundConstitutive methylation of tumor suppressor genes are associated with increased cancer risk. However, to date, the question of epimutational transmission of these genes remains unresolved. Here, we studied the potential transmission of BRCA1 and MGMT promoter methylations in mother-newborn pairs.MethodsA total of 1014 female subjects (cancer-free women, n = 268; delivering women, n = 295; newborn females, n = 302; breast cancer patients, n = 67; ovarian cancer patients, n = 82) were screened for methylation status in white blood cells (WBC) using methylation-specific PCR and bisulfite pyrosequencing assays. In addition, BRCA1 gene expression levels were analyzed by quantitative real-time PCR.ResultsWe found similar methylation frequencies in newborn and adults for both BRCA1 (9.9 and 9.3%) and MGMT (12.3 and 13.1%). Of the 290 mother-newborn pairs analyzed for promoter methylation, 20 mothers were found to be positive for BRCA1 and 29 for MGMT. Four mother-newborn pairs were positive for methylated BRCA1 (20%) and nine pairs were positive for methylated MGMT (31%). Intriguingly, the delivering women had 26% lower BRCA1 and MGMT methylation frequencies than those of the cancer-free female subjects. BRCA1 was downregulated in both cancer-free woman carriers and breast cancer patients but not in newborn carriers. There was a statistically significant association between the MGMT promoter methylation and late-onset breast cancers.ConclusionsOur study demonstrates that BRCA1and MGMT epimutations are present from the early life of the carriers. We show the transmission of BRCA1 and MGMT epimutations from mother to daughter. Our data also point at the possible demethylation of BRCA1and MGMT during pregnancy.

Epstein-Barr Virus-Induced Epigenetic Pathogenesis of Viral-Associated Lymphoepithelioma-Like Carcinomas and Natural Killer/T-Cell Lymphomas.

Cancer genome studies of Epstein-Barr virus (EBV)-associated tumors, including lymphoepithelioma-like carcinomas (LELC) of nasopharyngeal (NPC), gastric (EBVaGC) and lung tissues, and natural killer (NK)/T-cell lymphoma (NKTCL), reveal a unique feature of genomic alterations with fewer gene mutations detected than other common cancers. It is known now that epigenetic alterations play a critical role in the pathogenesis of EBV-associated tumors. As an oncogenic virus, EBV establishes its latent and lytic infections in B-lymphoid and epithelial cells, utilizing hijacked cellular epigenetic machinery. EBV-encoded oncoproteins modulate cellular epigenetic machinery to reprogram viral and host epigenomes, especially in the early stage of infection, using host epigenetic regulators. The genome-wide epigenetic alterations further inactivate a series of tumor suppressor genes (TSG) and disrupt key cellular signaling pathways, contributing to EBV-associated cancer initiation and progression. Profiling of genome-wide CpG methylation changes (CpG methylome) have revealed a unique epigenotype of global high-grade methylation of TSGs in EBV-associated tumors. Here, we have summarized recent advances of epigenetic alterations in EBV-associated tumors (LELCs and NKTCL), highlighting the importance of epigenetic etiology in EBV-associated tumorigenesis. Epigenetic study of these EBV-associated tumors will discover valuable biomarkers for their early detection and prognosis prediction, and also develop effective epigenetic therapeutics for these cancers.

Overexpression of DNA (Cytosine-5)-Methyltransferase 1 (DNMT1) And DNA (Cytosine-5)-Methyltransferase 3A (DNMT3A) Is Associated with Aggressive Behavior and Hypermethylation of Tumor Suppressor Genes in Human Pituitary Adenomas.

BackgroundAlteration of DNA methylation of tumor suppressor genes (TSGs) is one of the most consistent epigenetic changes in human cancers. DNMTs play several important roles in DNA methylation and development of cancers. Regarding DNMTs protein expressions, little is known about the clinical significance and correlation with promoter methylation status of TSGs in human pituitary adenomas.Material/MethodsWe analyzed the protein expression of 3 DNMTs using immunohistochemistry and assessed DNA hypermethylation of RASSF1A, CDH13, CDH1, and CDKN2A (p16) in 63 pituitary adenomas. We examined associations between DNMTs expression and clinicopathological features or promoter methylation status of TSGs.ResultsOverexpression of DNMTs was detected in pituitary adenomas. Frequencies of DNMT1 overexpression were significantly higher in macroadenomas, invasive tumors, and grade III and IV tumors. DNMT3A was frequently detected in invasive tumors and grade IV tumors. In addition, DNMT1 and DNMT3A were frequently detected in high-methylation tumors. Furthermore, in multivariate logistic regression, the significant association between DNMT1 or DNMT3A and high-methylation status persisted after adjusting for clinicopathological features.ConclusionsOur findings suggested that tumor overexpression of DNMT1 and DNMT3A is associated with tumor aggressive behavior and high-methylation status in pituitary adenomas. Our data support a possible role of DNMT1 and DNMT3A in TSG promoter methylation leading to pituitary adenoma invasion and suggest that inhibition of DNMTs has the potential to become a new therapeutic approach for invasive pituitary adenoma.

Abstract 557: Aberrant methylation of tumor-suppressor genes in pediatric myelodysplastic syndrome/acute myeloid leukemia

Abstract Introduction: Not only somatic mutations, but also epigenetic modifications in acute myeloid leukemia (AML) are estimated to have a pivotal role in leukemogenesis and it could be a therapeutic target. Especially, aberrant methylation of the promotor region of tumor suppressor genes (TSGs) were the causative events in leukemogenesis, however, there was only limited information in pediatric myelodysplastic syndrome (MDS) and AML. Materials and Methods: We analyzed the aberrant methylation of promotor region of 25 TSGs in pediatric 7 low grade MDS, 4 advanced MDS and 22 AML patients by FAB classification by Methylation-Specific Multiplex Ligation-dependent Probe Amplification (MS-MLPA) method (10 Male, 12 female, 0-14 years old, median 6 years ols). Simultaneously, detection of SNVs, In/del, and copy number variants were also analyzed by target sequence of more than 150 leukemia related genes. Especially, specific chimeras were analyzed in each patient. Results: Total 12/22(54.5%) patients had more than one methylated TSGs (number of methylated TSGs was 0-5 in each patient, median 1). More than 20% of patients had methylated TSGs including CDKN2B, CADM1, CDH13 and ESR1. Especially, there was a specific methylation pattern of TSGs, for example, all (4/4) t(8;21) patients had CDH13 methylation, 3/4 (75%) patients with inv(16) had ESR1 mutation and normal karyotype did not. Normal control samples, complete remission samples, and low grade MDS samples were not completely methylated. All advanced MDS patients had 1 or 2 methylated TSGs. Simultaneously, several leukemogenic genes were mutated such as GATA1, IKZF1, KRAS, KIT, FLT3, SH2B3, PIK3CD, PU.1, SMARC1, ALK, etc. Several genes were deleted such as CTCF, RB1, SRP72, ATM, NF1, U2AF1 etc. Discussion: In adult MDS, the increased number of methylated TSGs correlated to the development of AML and the poor prognosis. In this study, a few TSGs were methylated as the adult study (Hess CJ., Leuk Lymphoma 2008), furthermore, many genes related to epigenetic modification such as ASXL1, TET2 and EZH2 were not mutated in this study. Recently, anti-methylation drug were used in adult MDS/AML, larger study will be needed for adjusted use of epigenetic modifier in pediatric MDS/AML. Citation Format: Akira Shimada, Hirotaka Kanzaki, Hisashi Ishida, Takehiro Matsubara, Michinori Aoe. Aberrant methylation of tumor-suppressor genes in pediatric myelodysplastic syndrome/acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 557.

Abstract 3081: Methylation changes and somatic mutations as early events in Lynch syndrome-associated colorectal cancer

Abstract Lynch syndrome (LS) is a hereditary cancer predisposition syndrome caused by germline mutations in the DNA mismatch repair (MMR) genes resulting in an increased risk of colorectal cancer (CRC) and other malignancies. Those germline defects with other genetic and epigenetic changes accelerate multistep tumorigenesis. However, early events leading to polyp formation and the timing and order of the molecular “hits” remain unknown. Studies on sporadic CRC have indicated that promoter hypermethylation leading to gene silencing can act as an alternative mechanism to mutations at early stages of tumorigenesis, but its importance in hereditary CRC is obscure. In this study we aimed to define 1) methylation changes that occur at different stages of LS-associated colorectal tumor progression, and 2) somatic mutations that occur in adenomas comparing the status of low- and high-grade dysplasia and MMR deficiency (MMR-D) and proficiency (MMR-P). Colorectal biopsies including normal mucosae, adenomas and carcinomas were prospectively collected from 104 LS patients during colonoscopy surveillance, supplemented with retrospective tumor specimens from 56 patients. Promoter methylation was analyzed using the methylation-specific multiplex ligation-dependent probe amplification test (MS-MLPA) including selected tumor suppressor genes (TSGs) associated with early colon oncogenesis. Hypermethylation tendency was evaluated based on the frequency of CpG island methylator phenotype (CIMP) according to the methylation status of eight established CIMP marker genes. LINE-1 methylation was studied as a surrogate marker for global hypomethylation. Immunohistochemistry was used to detect MMR protein expression in neoplastic lesions. As an ongoing study mutation status of adenomas are studied using the Ion AmpliSeqTM Colon and Lung Cancer Panel targeting mutational hot spots in 22 genes. Results indicate that the expression of the MMR protein corresponding to the gene mutated in the germline decreases along with dysplasia but occurs as a relatively late event in the tumor progression, suggesting the presence of other somatic events that drive neoplastic transformation. Taken together, methylation of TSGs and frequency of CIMP increased and LINE-1 methylation decreased in adenomas and carcinomas along with dysplasia. However, a significant increase of methylation in some genes was detected already in adenomas with low-grade dysplasia compared to normal mucosae. In addition, a proportion of low-grade adenomas could already be classified CIMP positive. When comparing MMR-P and MMR-D adenomas, LINE-1 methylation decreased along the loss of MMR protein expression, and interestingly, higher methylation of SFRP1 was observed in MMR-P adenomas compared to MMR-D cases and normal mucosae. These findings emphasize the importance and early appearance of epigenetic changes in LS-associated tumorigenesis. Citation Format: Satu Mäki-Nevala, Satu Valo, Ari Ristimäki, Laura Renkonen-Sinisalo, Anna Lepistö, Jukka-Pekka Mecklin, Päivi Peltomäki. Methylation changes and somatic mutations as early events in Lynch syndrome-associated colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3081.

Aberrant DNA Methylation of Two Tumor Suppressor Genes, p14ARF and p15INK4b, after Chronic Occupational Exposure to Low Level of Benzene.

Background: Exposure to benzene would be associated with many diseases including leukemia. Epigenetic alterations seem to be among the main mechanisms involved. Objective: To determine if chronic occupational exposure to low level of benzene would be associated with DNA methylation. Methods: Global DNA methylation and promoter-specific methylation of the two tumor suppressor genes, p14ARF and p15INK4b, were assessed employing methylation-specific PCR using the DNA extracted from 40 petrochemical workers exposed to ambient benzene levels of <1 ppm, and 31 office workers not exposed to benzene or its derivatives. Results: While an increase in global DNA methylation of 5% in p14ARF (p=0.501) and 28% in p15INK4b (p=0.02) genes was observed in the exposed group, no hypermethylation in either of the studied genes was observed in the unexposed group. No significant association was found between the frequency of aberrant methylation and either of age, work experience, and smoking habit in the exposed group. Conclusion: Chronic occupational exposure to lower than the permissible exposure limit of benzene may still result in DNA methylation of tumor suppressor genes that may ultimately lead to development of cancer.

Abstract 5337: The epigenetic feedback loop of the CpG demethylase TET family genes in head and neck cancers

Abstract Purpose: The aim of this study is that clarifying the epigenetic regulation of TET family genes can provide insights into the mechanisms of tumorigenesis and the risk of disease recurrence in HNSCC. Experimental Design: We generated methylation profiles of TET family genes in tumor samples obtained from 233 patients with head and neck squamous cell carcinoma (HNSCC); these included 57 hypopharynx, 44 larynx, 69 oral cavity, and 63 oropharynx tumor samples. TET family genes mRNA expression and promoter DNA methylation were examined via quantitative reverse transcription (Q-RT-PCR) and methylation-specific PCR (Q-MSP), respectively. Promoter methylation was compared with various clinical characteristics and methylation index. Results: The TET methylation index (TE-MI) as the number of TET family genes methylation events was positively correlated with alcohol consumption (P = 0.004), HPV status (P = 0.004) and disease recurrence (P = 0.002). Simultaneous methylation analysis of TET family genes significantly correlated with reduced disease-free survival in unfavorable event groups (log-rank test, P = 0.026). In the multivariate Cox proportional hazards analysis, TET3 methylation of T1/2 patients, oropharyngeal cancer patients and oral cancer patients exhibited the high association with poor survival (hazard ratio: 2.64, P = 0.014; 3.55, P = 0.048; 2.63, P = 0.028, respectively). Joint analysis of tumor suppressor genes methylation index (TS-MI) showed a significant trend toward higher TE-MI increased. Conclusions: TET family genes methylation status was independently associated with aggressive tumor behavior and forming a DNA methylation feedback loop in patients with HNSCC. Citation Format: Kiyoshi Misawa, Atsushi Imai, Daiki Mochizuki, Takeharu Kanazawa. The epigenetic feedback loop of the CpG demethylase TET family genes in head and neck cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5337.

Aberrant DNA methylation is associated with aggressive clinicopathological features and poor survival in cutaneous melanoma.

Promoter methylation of tumour suppressor genes (TSGs) has recently been implicated in the pathogenesis of several types of cancer. Regarding melanoma, over 100 genes that contribute to its pathogenesis have been identified to be aberrantly hypermethylated. This is a retrospective observational study that aims to analyse the prevalence of CpG island methylation in a series of primary melanomas, to identify the associations with the main clinicopathological features, and to explore the prognostic significance of methylation in melanoma survival. DNA methylation was analysed using methylation-specific multiplex ligation-dependent probe amplification in a series of 170 melanoma formalin-fixed paraffin-embedded tumour samples. The relationship between the methylation status, known somatic mutations and clinicopathological features was evaluated. Disease-free survival (DFS) and overall survival (OS) were displayed by the Kaplan-Meier method. In the entire cohort, one or more genes were detected to be methylated in 55% of the patients. The most prevalent methylated genes were RARB 31%, PTEN 24%, APC 16%, CDH13 16%, ESR1 14%, CDKN2A 6% and RASSF1 5%. An association between aberrant methylation and aggressive clinicopathological features was observed (older age, increased Breslow thickness, presence of mitosis and ulceration, fast-growing melanomas, advancing stage and TERT mutations). Furthermore, Kaplan-Meier survival analysis showed a correlation of methylation and poorer DFS and OS. Aberrant methylation of TSGs is a frequent event in melanoma. It is associated with aggressive clinicopathological features and poorer survival. Epigenetic alterations may represent a significant prognostic marker with utility in routine practice.

Hypermethylation of CpG islands is associated with increasing chromosomal damage in chinese lead-exposed workers.

Lead is a widely existing environmental pollutant with potential carcinogenicity. To investigate the association of blood lead level (B-Pb) with potential chromosomal damage and cancer, we analyzed micronucleus (MN) frequency of peripheral blood lymphocytes (PBLs) and the methylation status of six human tumor suppressor genes (TSGs) post lead exposure. In the study, 147 lead-exposed workers were divided into two groups according to their B-Pb P50 value, with other 50 lead-unexposed workers as a control group. The cytokinesis-blocked micronucleus (CBMN) assay was performed to detect chromosomal damage of PBLs of both lead-exposed and -unexposed workers. The methylation-specific polymerase chain reaction (MSP-PCR) was further used to examine the methylation status of six TSGs (GSTP1, hMLH1, MGMT, p14, p15, and p16). Results showed that MN frequencies of high B-Pb workers 8.1 ± 3.1‰ and low B-Pb workers 5.7 ± 2.3‰ were significantly higher than that of control group 2.8 ± 1.9‰ (P < 0.01), while the MN frequency of high B-Pb workers was also higher than that of the low B-Pb workers (P < 0.01). The MN frequency in PBLs of lead-exposed group with the methylated TSGs was significantly higher than that in PBLs with the unmethylated TSGs (P < 0.05). Notably, the CpG island methylator phenotype (CIMP) correlated with chromosome damage (P < 0.05). Additionally, workers with high B-Pb had higher chromosome damage than those with low B-Pb (P < 0.05). Taken altogether, the results suggest that lead-exposed workers with CIMP positive and high B-Pb have a higher risk of being vulnerable to tumorigenesis. Environ. Mol. Mutagen. 59:549-556, 2018. © 2018 Wiley Periodicals, Inc.

Association of TET3 epigenetic inactivation with head and neck cancer.

The aim of this study was to clarify the epigenetic regulation of ten eleven translocation protein (TET) family genes, which can provide insights into the mechanisms of tumorigenesis and the risk of disease recurrence in head and neck squamous cell carcinoma (HNSCC). We generated methylation profiles of TET1, TET2 and TET3 genes in tumor samples obtained from 233 patients with HNSCC; these included 57 hypopharynx, 44 larynx, 69 oral cavity, and 63 oropharynx tumor samples. The mRNA expression and promoter DNA methylation of TET family genes were examined via quantitative RT-PCR and methylation-specific PCR, respectively. Promoter methylation was compared with various clinical characteristics and the TET methylation index (TE-MI). The TE-MI, representing the number of methylation events in TET family genes, was positively correlated with alcohol consumption (P = 0.004), high-risk human papilloma virus (HPV) status (P = 0.004) and disease recurrence (P = 0.002). The simultaneous methylation analysis of TET family genes was correlated with reduced disease-free survival in unfavorable event groups (log-rank test, P = 0.026). In the multivariate Cox proportional hazards analysis, TET3 methylation in T1 and T2 tumor stages, oropharyngeal cancer, and oral cancer patients exhibited high association with poor survival (hazard ratio: 2.64, P = 0.014; 3.55, P = 0.048; 2.63, P = 0.028, respectively). A joint analysis of the tumor suppressor gene methylation index showed a significant trend toward a higher TE-MI. The methylation status of TET3 was independently associated with aggressive tumor behavior and a global effect on DNA methylation status in HNSCC.

Deletion of MBD2 inhibits proliferation of chronic myeloid leukaemia blast phase cells

ABSTRACTAberrant methylation of tumour suppressor genes is associated with the progression to a blast crisis in chronic myeloid leukaemia (CML). Methyl-CpG-binding domain protein 2 (MBD2) has been studied as a “reader” of DNA methylation in many cancers, but its role in CML is unclear. We constructed cell models of a homozygous deletion mutation of MBD2 using gene-editing technology in K562 cells and BV173 cells. Here, we demonstrated that the deletion of MBD2 inhibited cell proliferation capacity in vitro. MBD2 deletion also significantly inhibited K562 cell proliferation in a xenograft tumour model in vivo. Additionally, the JAK2/STAT3 signalling pathway, which is abnormally active in CML, was inhibited by MBD2 deletion, and MBD2 deletion could up-regulate the expression of SHP1. In conclusion, our findings suggest that MBD2 is a candidate therapeutic strategy for the CML blast phase.

Using Methylation-Specific PCR to Study RB1 Promoter Hypermethylation.

It has increasingly been considered crucial the understanding of DNA methylation of Tumor Suppressor Gene (TSG) promoters, such as that of retinoblastoma 1 gene (RB1), and its role during carcinogenesis. We present a detailed and optimized protocol of the methylation-specific PCR (MSP) technique to study RB1 gene promoter hypermethylation.

Serrated neoplasia pathway as an alternative route of colorectal cancer carcinogenesis.

In the past two decades, besides conventional adenoma pathway, a subset of colonic lesions, including hyperplastic polyps, sessile serrated adenoma/polyps, and traditional serrated adenomas have been suggested as precancerous lesions via the alternative serrated neoplasia pathway. Major molecular alterations of sessile serrated neoplasia include BRAF mutation, high CpG island methylator phenotype, and escape of cellular senescence and progression via methylation of tumor suppressor genes or mismatch repair genes. With increasing information of the morphologic and molecular features of serrated lesions, one major challenge is how to reflect this knowledge in clinical practice, such as pathologic and endoscopic diagnosis, and guidelines for treatment and surveillance.

Lifetime exposure to ambient air pollution and methylation of tumor suppressor genes in breast tumors

BackgroundWe previously reported increased risk of breast cancer associated with early life exposure to two measures of air pollution exposure, total suspended particulates (TSP) and traffic emissions (TE), possible proxies for exposure to polycyclic aromatic hydrocarbons (PAHs). Exposure to PAHs has been shown to be associated with aberrant patterns of DNA methylation in peripheral blood of healthy individuals. Exposure to PAHs and methylation in breast tumor tissue has received little attention. We examined the association of early life exposure to TSP and TE with patterns of DNA methylation in breast tumors. MethodsWe conducted a study of women enrolled in the Western New York Exposures and Breast Cancer (WEB) Study. Methylation of nine genes (SFN, SCGB3A1, RARB, GSTP1, CDKN2A CCND2, BRCA1, FHIT, and SYK) was assessed using bisulfite-based pyrosequencing. TSP exposure at each woman's home address at birth, menarche, and when she had her first child was estimated. TE exposure was modeled for each woman's residence at menarche, her first birth, and twenty and ten years prior to diagnosis. Unconditional logistic regression was employed to estimate odds ratios (OR) of having methylation greater than the median value, adjusting for age, secondhand smoke exposure before age 20, current smoking status, and estrogen receptor status. ResultsExposure to higher TSP at a woman's first birth was associated with lower methylation of SCGB3A1 (OR = 0.48, 95% CI: 0.23–0.99) and higher methylation of SYK (OR = 1.86, 95% CI: 1.03–3.35). TE at menarche was associated with increased methylation of SYK (OR = 2.37, 95% CI: 1.05–5.33). TE at first birth and ten years prior to diagnosis was associated with decreased methylation of CCND2 (OR ten years prior to diagnosis=0.48, 95% CI: 0.26–0.89). Although these associations were nominally significant, none were significant after adjustment for multiple comparisons (p < 0.01). ConclusionsWe observed suggestive evidence that exposure to ambient air pollution throughout life, measured as TSP and TE, may be associated with DNA methylation of some tumor suppressor genes in breast tumor tissue. Future studies with a larger sample size that assess methylation of more sites are warranted.

Association of MGMT promoter methylation with tumorigenesis features in patients with ovarian cancer: A systematic meta-analysis.

BackgroundThe MGMT is a key tumor suppressor gene and aberrant promoter methylation has been reported in many cancers. However, the relationship between MGMT promoter methylation and ovarian cancer remains controversial. This meta‐analysis was first conducted to estimate the clinical significance of MGMT promoter methylation in ovarian carcinoma.MethodsLiterature search was performed in the PubMed, Embase, EBSCO and Cochrane Library databases. The pooled odds ratio (OR) and their corresponding 95% confidence interval (95% CI) were summarized.ResultsFinal 10 studies with 910 ovarian tissue samples were included in this meta‐analysis. MGMT promoter methylation was significantly higher in ovarian cancer than in normal ovarian tissues (OR = 4.13, 95% CI = 2.32–7.33, p < .001). The MGMT had a similar methylation status in cancer versus benign lesions and low malignant potential (LMP) samples (OR = 2.01, 95% CI = 0.67–6.04, p = .212; OR = 1.42, 95% CI = 0.46–4.40, p = .543; respectively). MGMT promoter methylation was correlated with pathological types in which it was significantly lower in serous cancer than in nonserous cancer (OR = 0.29, 95% CI = 0.14–0.59, p = .001). The methylation of the MGMT promoter was not associated with clinical stage and tumor grade (OR = 1.46, 95% CI = 0.71–3.02, p = .301; OR = 1.13, 95% CI = 0.51–2.46, p = .767; respectively).Conclusions MGMT promoter methylation may be correlated with the tumorigenesis of ovarian cancer. It was associated with tumor histotypes, but not correlated with clinical stage and tumor grade. More prospective studies with lager sample sizes are necessary in the future.

Promoter Methylation of RASSF1A Gene in Egyptian Patients with Ovarian Cancer.

Ovarian malignancy is diagnosed in nearly a fourth of a million women internationally every year. Methylation of RASSF1A tumor suppressor gene prompts its inactivation in diseases. In this study, the RASSF1A promoter methylation was detected by methylated-specific PCR and investigated serum RASSF1A protein level through enzyme-linked immunosorbant assay in 160 Egyptian patients with ovarian cancer and 160 healthy controls. The present work proved that there was a higher frequency of RASSF1A methylation and a decrease in its serum level in patients with ovarian cancer compared to controls as well as in the high-grade tumor patients compared to low grade ones and also in advanced ovarian tumor stage compared to early stages. Our study exhibited that RASSF1A promoter hypermethylation and its protein levels may be a reliable and sensitive tool for diagnosing and monitoring of ovarian malignancy patients.

A vicious loop of fatty acid-binding protein 4 and DNA methyltransferase 1 promotes acute myeloid leukemia and acts as a therapeutic target.

Aberrant DNA methylation mediated by deregulation of DNA methyltransferases (DNMT) is a key hallmark of acute myeloid leukemia (AML), yet efforts to target DNMT deregulation for drug development have lagged. We previously demonstrated that upregulation of fatty acid-binding protein 4 (FABP4) promotes AML aggressiveness through enhanced DNMT1-dependent DNA methylation. Here we demonstrate that FABP4 upregulation in AML cells occurs through vascular endothelial growth factor (VEGF) signaling, thus elucidating a crucial FABP4-DNMT1 regulatory feedback loop in AML biology. We show that FABP4 dysfunction by its selective inhibitor BMS309403 leads to downregulation of DNMT1, decrease of global DNA methylation and re-expression of p15INK4B tumor suppressor gene by promoter DNA hypomethylation in vitro, ex vivo and in vivo. Functionally, BMS309403 suppresses cell colony formation, induces cell differentiation, and, importantly, impairs leukemic disease progression in mouse models of leukemia. Our findings highlight AML-promoting properties of the FABP4-DNMT1 vicious loop, and identify an attractive class of therapeutic agents with a high potential for clinical use in AML patients. The results will also assist in establishing the FABP4-DNMT1 loop as a target for therapeutic discovery to enhance the index of current epigenetic therapies.