DNA Methylation ; Glioma ; metabolism ; Humans ; O(6)-Methylguanine-DNA Methyltransferase ; genetics ; Polymerase Chain Reaction ; methods ; Promoter Regions, Genetic ; genetics

Despite recent innovation in treatment techniques and subsequently improved outcomes, the majority of glioblastoma (GBL) have relapses, especially in locoregional areas. Local re-irradiation (re-RT) has been established as a feasible option for recurrent GBL of all ages with safety, tolerability, and effectiveness both in survival and quality of life regardless of fractionation schedule. To keep adverse effects under acceptable range, cumulative dose limit in equivalent dose at 2 Gy fractions by the linear-quadratic model at α/β = 2 for normal brain tissue (EQD2) with narrow margin should be observed and single/hypofractionated re-RT should be undertaken very carefully to recurrent tumor with large volume or adjacent to the brainstem. Promising outcome of re-operation (re-Op) plus re-RT (re-Op/RT) need to be validated and result from re-RT with temozolomide/bevacizumab (TMZ/BV) or new strategy is expected. Development of new-concept prognostic scoring or risk group is required to select patients properly and make use of predictive biomarkers such as O(6)-methylguanine-DNA methyltransferase (MGMT) promotor methylation that influence outcomes of re-RT, re-Op/RT, or re-RT with TMZ/BV.
Appointments and Schedules ; Biomarkers ; Brain ; Brain Stem ; Glioblastoma ; Humans ; Methylation ; O(6)-Methylguanine-DNA Methyltransferase ; Quality of Life ; Re-Irradiation ; Recurrence

OBJECTIVETo elucidate the mechanism of carcinogenesis induced by coke oven emissions by investigating the cell genetic damage index and the methylation of O⁶-methylguanine-DNA methyltransferase (MGMT).

METHODSThe human bronchial epithelial cell 16HBE was treated by 1 µmol/L B(a)P for 48 h, and then was exposed continuously to either 1‰ dimethyl sulfoxide (DMSO) or organic extracts of coke oven emission (OE-COE) for five days at the concentrations of 0, 2.5, 5.0, 10.0 and 20.0 µg/ml. The methylation-specific PCR (MSP-PCR), RT-PCR and immunoblotting were applied to detect the methylation status, changes of mRNA and protein of MGMT, respectively. Single cell gel electrophoresis was used to detect DNA damage induced by OE-COE.

RESULTSCompared with the control group (DMSO), there was a significant hypermethylation in all study groups, along with the suppression of mRNA and protein in a dose-dependent manner, and the gradation ratio of them was 1.0, 0.96, 0.96, 0.85, 0.32 and 1.0, 1.0, 1.1, 0.41, 0.52, separately. There was a significant DNA damage with a dose-effect relationship in all study groups (F = 41.22, P < 0.05), and the comet Olive tail moment was (2.98 ± 1.43), (4.76 ± 1.79), (10.09 ± 1.75), (11.38 ± 1.77), (11.67 ± 1.88). The further study found that the index of DNA damage was negatively correlated to the expression of MGMT mRNA and its protein.

CONCLUSIONThe DNA damage induced by COE might be associated with the suppression of MGMT caused by its hypermethylation.

Bronchi ; cytology ; Cell Line ; Coke ; adverse effects ; Comet Assay ; DNA Damage ; DNA Methylation ; DNA Repair ; Epithelial Cells ; metabolism ; Gene Silencing ; Humans ; O(6)-Methylguanine-DNA Methyltransferase ; genetics ; metabolism

The relationship between hypermethylation of CpG islands in the promoter regions of O6-methylguanine DNA methyltransferase (MGMT) genes and laryngeal squamous cell carcinoma was explored. Methylation-specific PCR and semi-quantitative RT-PCR were used to study the promoter methylation and mRNA expression of the MGMT gene in laryngeal carcinoma tissues, tissues adjacent to the tumor and normal laryngeal tissues. Hypermethylation of MGMT gene was detected in 16 samples of 46 (34.8%) laryngeal squamous cell carcinoma samples. However, the MGMT hypermethylation was not detected in all tissues adjacent to the tumors and normal tissues. No significant difference in MGMT gene hypermethylation was found in samples with different histological grades (chi2 = 3.130, P = 0.077) or in samples from patients with different TNM status (chi2 = 3.957, P = 0.138). No expression of MGMT mRNA was detected in all hypermethylated laryngeal carcinoma tissues. The expression of MGMT mRNA was detected in all unmethylated laryngeal carcinoma tissues, tissues adjacent to the tumors and normal tissues. It suggests that MGMT gene promoter hypermethylation is associated with MGMT gene transcription loss in laryngeal carcinoma tissues and possibly plays an important role in carcinogenesis of laryngeal tissues.
Carcinoma, Squamous Cell/*genetics ; CpG Islands/genetics ; DNA Methylation ; DNA Repair ; Laryngeal Neoplasms/*genetics ; O(6)-Methylguanine-DNA Methyltransferase/*genetics ; Polymerase Chain Reaction/methods ; Promoter Regions (Genetics)/*genetics

PURPOSE: Functional inactivation of the O(6)-methylguanine-DNA methyltransferase (MGMT) gene has been demonstrated as loss of MGMT protein and suggested that it plays an important role in primary human neoplasia, including lung cancer. It has also been reported to be associated with the G : C-->A : T transition mutation in the p53 gene of lung cancer. The aims of this study were to investigate the role of MGMT expression loss and its prognostic significance in non-small cell lung carcinomas (NSCLCs), and its correlation with p53 overexpression as well as influence on patient survival. MATERIALS AND METHODS: 112 surgically resected NSCLC specimens were reviewed by medical records for their clinicopathologic variables. Their tissue microarray blocks were immunostained with anti-human MGMT and p53 primary antibodies. Correlation between MGMT loss and the clinicopathologic prognostic factors, including p53 overexpression and the single or combined actions of MGMT loss and p53 overexpression on patient survival were statistically analyzed by SPSS15.0. RESULTS: Reduced or absent MGMT expression was found in 48 of 112 NSCLCs (43%), and significantly associated with nodal metastasis and squamous or undifferentiated cell types. Loss of MGMT expression was correlated with p53 overexpression in adenocarcinomas, but not in overall NSCLCs. Its solitary or combined actions with p53 overexpression did not have influence on patient survival. CONCLUSION: Loss of MGMT expression is a relatively common event in NSCLCs and significantly associated with nodal metastasis and p53 overexpression, suggesting that it may play a major role in pulmonary carcinogenesis, and also in disease progression of NSCLCs.
Adenocarcinoma ; Antibodies ; Disease Progression ; DNA ; Genes, p53 ; Guanine ; Humans ; Lung ; Lung Neoplasms ; Medical Records ; Neoplasm Metastasis ; O(6)-Methylguanine-DNA Methyltransferase

BACKGROUNDGlioblastoma multiforme (GBM) is the most common and lethal primary brain tumor in adults. Magnetic resonance imaging (MRI) is routinely used in the diagnosis, characterization and clinical management of GBM. The diagnosis and treatment of GBM is largely guided by histopathology and immunohistochemistry. This study aimed to identify the relationship between magnetic resonance features and molecular pathology of GBM.

METHODSMRI images of 43 glioblastoma patients were collected. Four imaging features, degree of edema, contrast tumor enhanced/T2 ratio, multiple lesions and tumor across the midline, were selected to identify their relationship with P53, Ki-67 and O(6)-methylguanine-DNA methyltransferase (MGMT) expression in patients with GBM. The relationship between imaging features and molecular pathology was studied by chi-square test using the software SPSS 13.0.

RESULTSHigh expression of P53 was found correlated with low contrast tumor enhanced/T2 ratio, low expression of Ki-67 was correlated with multiple lesions and high expression of KI-67 may be related with tumor across the midline, low expression of MGMT was correlated with edema.

CONCLUSIONSome MRI features such as the degree of edema, contrast tumor enhanced/T2 ratio, multiple lesions and tumor acrossing the midline are correlated with P53, Ki-67 and MGMT of GBM.

Edema ; metabolism ; pathology ; Glioblastoma ; metabolism ; pathology ; Humans ; In Vitro Techniques ; Ki-67 Antigen ; metabolism ; Magnetic Resonance Imaging ; methods ; O(6)-Methylguanine-DNA Methyltransferase ; metabolism ; Tumor Suppressor Protein p53 ; metabolism

OBJECTIVETo evaluate association between DNA methylation of MAL, CDKN2A, and MGMT in stool and development of colorectal cancer, and to evaluate the screening value of these biomarkers in colorectal cancer and pre-malignant lesions.

METHODSMorning stool specimens were collected from 69 patients with colorectal cancer, 24 with colon adenoma, 19 with hyperplastic polyps, and 26 healthy controls. DNA was extracted and treated with bisulfite. Methylation-specific PCR(MSP) was performed for methylation analysis of MAL, CDKN2A and MGMT in DNA samples. Associations between clinicopathological features and gene methylation were analyzed. The sensitivity of diagnosis by combining three methylation markers was compared with fecal occult blood test(FOBT).

RESULTSThe methylation frequencies of MAL, CDKN2A and MGMT were 78.3%, 52.5% and 55.1% in colorectal cancer, 58.3%, 41.7% and 37.5% in colon adenomas, 26.3%, 15.8% and 10.5% in hyperplastic polyps, and 3.8%, 0 and 3.8% in healthy controls, respectively. Significant differences in three genes were found between colorectal cancer and hyperplastic polyp, colorectal cancer and healthy control, colon adenoma and hyperplastic polyp, colon adenoma and healthy control(all P<0.05). The diagnostic sensitivity by combining three methylation markers was 92.8% in colorectal cancer, 70.8% in colon adenomas, significantly higher than FOBT examination (29.0% in colorectal cancer and 25.0% in colon adenomas, all P<0.05). No significant associations existed between three genes methylation of the three genes and clinical characteristic including sex, age, tumor location, lymph node metastases and TNM stage (all P>0.05).

CONCLUSIONDNA methylations levels of MAL, CDKN2A, and MGMT in stools are significantly higher in colorectal cancer and colon adenoma, which may serve as an noninvasive approach for the screening of colorectal cancer and pre-malignant lesions.

Adult ; Aged ; Colorectal Neoplasms ; diagnosis ; genetics ; Cyclin-Dependent Kinase Inhibitor p16 ; genetics ; DNA Methylation ; Early Detection of Cancer ; Feces ; chemistry ; Female ; Humans ; Male ; Mass Screening ; Middle Aged ; O(6)-Methylguanine-DNA Methyltransferase ; genetics ; Precancerous Conditions ; diagnosis ; genetics ; Promoter Regions, Genetic ; genetics

OBJECTIVETo establish a drug-resistance cell line of human glioma mediated by MGMT.

METHODSSimulated the clinical usage of BCNU to establish a BCNU-resistant human glioma subline by cyclic exposing the U251 parent cells to a constant concentration of BCNU. The resistance index and the expression of MGMT mRNA of U251/BCNU were detected and compared the difference of in vitro proliferation between U251 and U251/BCNU.

RESULTSA subline--U251/BCNU was successfully established in about 4-month culture, which had a stable resistance to BCNU. U251/BCNU cells showed 17-fold higher resistance to BCNU than did U251 cells by MTT assay, while U251/BCNU cells expressed MGMT mRNA. The doubling time of U251 and U251/BCNU had no statistical difference.

CONCLUSIONA drug-resistance cell line of human glioma mediated by MGMT is established, which could provide experimental basis for further studies on the resistance mechanism and reversal methods of glioma chemotherapy.

ATP-Binding Cassette, Sub-Family B, Member 1 ; biosynthesis ; Brain Neoplasms ; pathology ; Cell Line, Tumor ; DNA Modification Methylases ; biosynthesis ; genetics ; Drug Resistance, Neoplasm ; genetics ; Glioma ; pathology ; Humans ; O(6)-Methylguanine-DNA Methyltransferase ; metabolism ; physiology

The hypermethylation of the CpG islands is a common mechanism for the inactivation of tumor-related genes. In the present study, we analyzed the methylation status of genes for cell repair such as hMLH1, MGMT, and GSTP1, and a gastric cancer-specifically methylated DNA fragment, MINT 25 in gastric cancer cases and control groups. The study population consisted of 100 gastric cancer patients (50 distal and 50 proximal carcinomas), and 238 healthy controls. All genes showed more frequent hypermethylation in the cases than in the control group (p<0.0001). We investigated the association between promoter hypermethylation and relevant parameters including age, gender, alcohol consumption, smoking, and family history. There was a common hypermethylation of hMLH1 (p=0.008), MGMT (p= 0.0001), and GSTP1 (p=0.0003) in females. This study also demonstrates that hypermethylation was strongly associated with non-drinkers (MGMT, p=0.046 and MINT 25, p=0.049) and non-smokers (hMLH1, p=0.044; MGMT, p=0.0003; MINT 25, p=0.029). Moreover, the frequency of MINT 25 hypermethylation increased with age (p=0.037), and MGMT methylation was frequently detected in distal gastric cancer than in proximal type (p=0.038). Our study suggested that promoter hypermethylation of the genes involved in cell repair system and MINT 25 is associated strongly with some subgroups of primary gastric carcinoma.
Adult ; Aged ; *DNA Methylation ; Female ; Glutathione Transferase/genetics ; Humans ; Isoenzymes/genetics ; Male ; Middle Aged ; Neoplasm Proteins/genetics ; Nuclear Proteins/genetics ; O(6)-Methylguanine-DNA Methyltransferase/genetics ; Promoter Regions (Genetics) ; Research Support, Non-U.S. Gov't ; Stomach Neoplasms/*genetics

OBJECTIVETo study the methylation of O-6-methylguanine-DNA methyltransferase (MGMT) and p16 gene in the sputum cells of radon-exposed population. To provide the experimental base for finding the molecular biomarker of the high risk population of the radon-induced lung cancer.

METHODS91 radon-exposed workers were divided into 4 groups, high dosage group (> 120 WLM), middle dosage group (between 60 and 120 WLM), low dosage group (between 30 and 60 WLB) and lower dosage group (between 2 and 30 WLM) according to the accumulated exposure dosage of the radon daughters. The abnormal methylation of p16 and MGMT gene in the sputum cells of the population in the four groups was detected with the methylation specific PCR (MSP).

RESULTSThere was significantly upward trend for the p16 gene methylation rate (0.00%-20.00%), the MGMT gene methylation rate (0.00%-28.00%) and the total methylation rate (0.00%-40.00%) with the increase of the accumulated exposure dosage of the radon daughters (P < 0.01).

CONCLUSIONThe methylation of p16 and MGMT gene is related to the accumulate exposure dosage of the radon daughters.

Carcinogens, Environmental ; adverse effects ; Cyclin-Dependent Kinase Inhibitor p16 ; genetics ; metabolism ; DNA Methylation ; Dose-Response Relationship, Radiation ; Humans ; Male ; O(6)-Methylguanine-DNA Methyltransferase ; genetics ; metabolism ; Occupational Exposure ; Radon ; adverse effects ; Radon Daughters ; adverse effects ; Sputum ; metabolism