Promoter methylation of O(6)-methylguanine-DNA-methyltransferase in lung cancer is regulated by p53.
Methylation of the O(6)-methylguanine-DNA-methyltransferase (MGMT) promoter is associated with G:C to A:T transitions in the p53 gene in various human cancers, including lung cancer. In tumors with p53 mutation, MGMT promoter methylation is more common in advanced tumors than in early tumors. However, in tumors with wild-type p53, MGMT promoter methylation is independent of tumor stage. To elucidate whether p53 participates in MGMT promoter methylation, we engineered three cell models: A549 cells with RNA interference (RNAi)-mediated knockdown of p53, and p53 null H1299 cells transfected with either wild-type p53 (WT-p53) or mutant-p53 (L194R, and R249S-p53). Knockdown of endogenous p53 increased MGMT promoter methylation in A549 cells, and transient expression of WT-p53 in p53 null H1299 cells diminished MGMT promoter methylation, whereas the MGMT promoter methylation status were unchanged by expression of mutant-p53. Previous work showed that p53 modulates DNA-methyltransferase 1 (DNMT1) expression; we additionally examined chromatin remodeling proteins expression levels of histone deacetylase 1 (HDAC1). We found that p53 knockdown elevated expression of both DNMT1 and HDAC1 in A549 cells. Conversely, expressing WT-p53 in p53 null H1299 cells reduced DNMT1 and HDAC1 expression, but the reduction of both proteins was not observed in expressing mutant-p53 H1299 cells. CHIP analysis further showed that DNMT1 and HDAC1 binding to the MGMT promoter was increased by MGMT promoter methylation and decreased by MGMT promoter demethylation. In conclusion, MGMT promoter methylation modulated by p53 status could partially promote p53 mutation occurrence in advanced lung tumors.
Institute of Medical & Molecular Toxicology, Chung Shan Medical University, Taichung, Taiwan, ROC.
Ji-Ching
JC
Lai
Ya-Wen
YW
Cheng
Yih-Gang
YG
Goan
Jinghua Tsai
JT
Chang
Tzu-Chin
TC
Wu
Chih-Yi
CY
Chen
Huei
H
Lee
D001483:Base Sequence; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000235:genetics*; D017931:DNA Primers; D045643:DNA Repair Enzymes / Q000235:genetics*; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases / Q000235:genetics; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology*; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000235:genetics*
D017931:DNA Primers; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D015254:DNA Modification Methylases; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human; C515491:MGMT protein, human; C110550:HDAC1 protein, human; D056284:Histone Deacetylase 1; D006655:Histone Deacetylases; D045643:DNA Repair Enzymes