O6-Methylguanine-DNA methyltransferase hypermethylation modulated by 17beta-estradiol in lung cancer cells.
BACKGROUND
Our recent report indicated that MGMT hypermethylation is more common in squamous cell carcinomas (SCC) in males, and smokers than in adenocarcinomas (ADC) in females, and nonsmokers. More interestingly, MGMT hypermethylation in SCC and ADC was pronouncedly influenced by gender factor, not by smoking status. We questioned whether 17beta-estradiol could modulate the machinery of promoter methylation to cause the gender difference of MGMT hypermethylation in lung cancer.


METHODS
Two MGMT hypermethylated Ch27 and H1355 lung cancer cell lines were treated with or without 17beta-estradiol and the status of hypermethylation was examined by methylated specific methylation (MSP) as compared with both cells treated with demethylating agents, 5-AZA-dC (AZA) or TSA.


RESULTS
Our data showed that 17beta-estradiol, similar to AZA, diminished the MGMT hypermethylation and restored MGMT mRNA expression, which was not observed in the case of TSA. Western blotting showed that 17beta-estradiol markedly reduced DNMT1 expression in Ch27 and H1355 cells, but slightly reduced HDAC1 expression. Consequently, acetylated H3 and H4 histone levels were slightly increased by 17beta-estradiol in both cell types. In addition, ChIP analysis revealed that 17beta-estradiol simultaneously diminished the binding activity of both proteins on the MGMT promoter of both cell lines.


CONCLUSIONS
17beta-Estradiol decreased DNMT1 and HDAC1 protein expressions and their binding activity on MGMT promoter, and this may partially contribute to the gender difference of MGMT hypermethylation in lung cancer.
Lai
Ji-Ching
JC
Department of Internal Medicine, Institute of Medical and Molecular Toxicology, Chung Shan Medical University, Taichung, Taiwan.
Wu
Jeng-Yuan
JY
Cheng
Ya-Wen
YW
Yeh
Kun-Tu
KT
Wu
Tzu-Chin
TC
Chen
Chih-Yi
CY
Lee
Huei
H
D000230:Adenocarcinoma / Q000201:enzymology / Q000473:pathology; D001483:Base Sequence; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000201:enzymology / Q000473:pathology; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D019175:DNA Methylation; D017931:DNA Primers; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology* / Q000473:pathology; D008297:Male; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics
D017931:DNA Primers; D012333:RNA, Messenger; D004958:Estradiol; D019853:O(6)-Methylguanine-DNA Methyltransferase