title: The A/G allele of rs16906252 predicts for MGMT methylation and is selectively silenced in premalignant lesions from smokers and in lung adenocarcinomas.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Lung Cancer Program, Lovelace Respiratory Research Institute, Albuquerque, New Mexico 87108, USA.
authors.forename: Shuguang
authors.initials: S
authors.lastname: Leng
authors.forename: Amanda M
authors.initials: AM
authors.lastname: Bernauer
authors.forename: Chibo
authors.initials: C
authors.lastname: Hong
authors.forename: Kieu C
authors.initials: KC
authors.lastname: Do
authors.forename: Christin M
authors.initials: CM
authors.lastname: Yingling
authors.forename: Kristina G
authors.initials: KG
authors.lastname: Flores
authors.forename: Mathewos
authors.initials: M
authors.lastname: Tessema
authors.forename: Carmen S
authors.initials: CS
authors.lastname: Tellez
authors.forename: Randall P
authors.initials: RP
authors.lastname: Willink
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Burki
authors.forename: Maria A
authors.initials: MA
authors.lastname: Picchi
authors.forename: Christine A
authors.initials: CA
authors.lastname: Stidley
authors.forename: Michael D
authors.initials: MD
authors.lastname: Prados
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Costello
authors.forename: Frank D
authors.initials: FD
authors.lastname: Gilliland
authors.forename: Richard E
authors.initials: RE
authors.lastname: Crowell
authors.forename: Steven A
authors.initials: SA
authors.lastname: Belinsky
mesh_terms: D000230:Adenocarcinoma / Q000209:etiology / Q000235:genetics / Q000473:pathology; D000077192:Adenocarcinoma of Lung; D000328:Adult; D000368:Aged; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology; D045744:Cell Line, Tumor; D015254:DNA Modification Methylases / Q000235:genetics* / Q000378:metabolism*; D045643:DNA Repair Enzymes / Q000235:genetics* / Q000378:metabolism*; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000494:pharmacology; D044127:Epigenesis, Genetic; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D056726:Genetic Association Studies; D006239:Haplotypes; D006801:Humans; D015810:Linkage Disequilibrium; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D008175:Lung Neoplasms / Q000209:etiology / Q000235:genetics / Q000473:pathology; D008297:Male; D008745:Methylation; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D011230:Precancerous Conditions / Q000209:etiology / Q000235:genetics* / Q000473:pathology; D011401:Promoter Regions, Genetic; D012907:Smoking / Q000009:adverse effects*; D013183:Sputum / Q000166:cytology / Q000378:metabolism; D000077204:Temozolomide; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism*; D001616:beta-Galactosidase / Q000096:biosynthesis
chemical_list: D018906:Antineoplastic Agents, Alkylating; D025521:Tumor Suppressor Proteins; D003606:Dacarbazine; D008156:Luciferases; D015254:DNA Modification Methylases; C515491:MGMT protein, human; D001616:beta-Galactosidase; D045643:DNA Repair Enzymes; D000077204:Temozolomide