The A/G Allele of Rs16906252 Predicts for MGMT Methylation and Is Selectively Silenced in Premalignant Lesions from Smokers and in Lung Adenocarcinomas

• Published in: Clinical cancer research 2011-04, Vol.17 (7), p.2014-2023
• Main Authors: SHUGUANG LENG, BERNAUER, Amanda M, PICCHI, Maria A, STIDLEY, Christine A, PRADOS, Michael D, COSTELLO, Joseph F, GILLILAND, Frank D, CROWELL, Richard E, BELINSKY, Steven A, CHIBO HONG, DO, Kieu C, YINGLING, Christin M, FLORES, Kristina G, TESSEMA, Mathewos, TELLEZ, Carmen S, WILLING, Randall P, BURKE, Elizabeth A
• Format: Article
• Language: English
• Subjects: Adenocarcinoma - etiology; Adenocarcinoma - genetics; Adenocarcinoma - pathology; Adenocarcinoma of Lung; Adult; Aged; Antineoplastic agents; Antineoplastic Agents, Alkylating - pharmacology; beta-Galactosidase - biosynthesis; Biological and medical sciences; Cell Line, Tumor; Dacarbazine - analogs & derivatives; Dacarbazine - pharmacology; DNA Modification Methylases - genetics; DNA Modification Methylases - metabolism; DNA Repair Enzymes - genetics; DNA Repair Enzymes - metabolism; Epigenesis, Genetic; Female; Gene Expression Regulation, Neoplastic; Genes, Reporter; Genetic Association Studies; Haplotypes; Humans; Linkage Disequilibrium; Luciferases - biosynthesis; Luciferases - genetics; Lung Neoplasms - etiology; Lung Neoplasms - genetics; Lung Neoplasms - pathology; Male; Medical sciences; Methylation; Middle Aged; Pharmacology. Drug treatments; Pneumology; Polymorphism, Single Nucleotide; Precancerous Conditions - etiology; Precancerous Conditions - genetics; Precancerous Conditions - pathology; Promoter Regions, Genetic; Smoking - adverse effects; Sputum - cytology; Sputum - metabolism; Temozolomide; Tobacco, tobacco smoking; Toxicology; Transcription, Genetic; Tumor Suppressor Proteins - genetics; Tumor Suppressor Proteins - metabolism; Tumors of the respiratory system and mediastinum
• ISSN: 1078-0432; 1557-3265
• DOI: 10.1158/1078-0432.ccr-10-3026

To address the association between sequence variants within the MGMT (O(6)-methylguanine-DNA methyltransferase) promoter-enhancer region and methylation of MGMT in premalignant lesions from smokers and lung adenocarcinomas, their biological effects on gene regulation, and targeting MGMT for therapy. Single nucleotide polymorphisms (SNP) identified through sequencing a 1.9 kb fragment 5' of MGMT were examined in relation to MGMT methylation in 169 lung adenocarcinomas and 1,731 sputum samples from smokers. The effect of promoter haplotypes on MGMT expression was tested using a luciferase reporter assay and cDNA expression analysis along with allele-specific sequencing for methylation. The response of MGMT methylated lung cancer cell lines to the alkylating agent temozolomide (TMZ) was assessed. The A allele of rs16906252 and the haplotype containing this SNP were strongly associated with increased risk for MGMT methylation in adenocarcinomas (ORs ≥ 94). This association was observed to a lesser extent in sputum samples in both smoker cohorts. The A allele was selectively methylated in primary lung tumors and cell lines heterozygous for rs16906252. With the most common haplotype as the reference, a 20 to 41% reduction in promoter activity was seen for the haplotype carrying the A allele that correlated with lower MGMT expression. The sensitivity of lung cancer cell lines to TMZ was strongly correlated with levels of MGMT methylation and expression. These studies provide strong evidence that the A allele of a MGMT promoter-enhancer SNP is a key determinant for MGMT methylation in lung carcinogenesis. Moreover, TMZ treatment may benefit a subset of lung cancer patients methylated for MGMT.