title: Aberrant methylation accounts for cell adhesion-related gene silencing during 3-methylcholanthrene and diethylnitrosamine induced multistep rat lung carcinogenesis associated with overexpression of DNA methyltransferases 1 and 3a.
abstract: To evaluate the significance of alterations in cell adhesion-related genes methylation during lung multistep carcinogenesis induced by the genotoxic carcinogens 3-methylcholanthrene (MCA) and diethylnitrosamine (DEN), tissue samples microdissected from MCA/DEN-induced rat lung carcinogenesis model were subjected to methylation-specific PCR to evaluate the DNA methylation status of CADM1, TIMP3, E-cadherin and N-cadherin. Immunohistochemistry was used to determine protein expression of CADM1, TIMP3, N-cadherin and the DNA methyltransferases (DNMTs) 1, 3a and 3b. E-cadherin hypermethylation was not detected in any tissue. CADM1, TIMP3 and N-cadherin hypermethylation was correlated with the loss of their protein expression during the progression of pathologic lesions. The prevalence of DNA methylation of at least one gene and the average number of methylated genes increased with the histological progression. DNMT1 and DNMT3a protein expression increased progressively during the stages of lung carcinogenesis, whereas DNMT3b overexpression was only found in several samples. Furthermore, DNMT1 protein expression levels were correlated with CADM1 methylation, and DNMT3a protein expression levels were correlated with CADM1, TIMP3 and N-cadherin methylation. The average number of methylated genes during carcinogenesis was significantly correlated with DNMT1 and DNMT3a protein expression levels. Moreover, mRNA expression of CADM1 significantly increased after treatment with DNMT inhibitor 5-aza-2'-deoxycytidine in CADM1-methylated primary tumor cell lines. Our findings suggest that an accumulation of hypermethylation accounts for cell adhesion-related gene silencing is associated with dynamic changes in the progression of MCA/DEN-induced rat lung carcinogenesis. We suggest that DNMT1 and DNMT3a protein overexpression may be responsible for this aberrant DNA methylation.
authors.affiliation: Department of Hygiene Toxicology, Preventive Medical College, Third Military Medical University, Key Laboratory of Medical Protection for Electromagnetic Radiation, Ministry of Education of China, Chongqing 400038, P.R. China.
authors.forename: Wen-bin
authors.initials: WB
authors.lastname: Liu
authors.forename: Zhi-hong
authors.initials: ZH
authors.lastname: Cui
authors.forename: Lin
authors.initials: L
authors.lastname: Ao
authors.forename: Zi-yuan
authors.initials: ZY
authors.lastname: Zhou
authors.forename: Yan-hong
authors.initials: YH
authors.lastname: Zhou
authors.forename: Xiao-yan
authors.initials: XY
authors.lastname: Yuan
authors.forename: Yun-long
authors.initials: YL
authors.lastname: Xiang
authors.forename: Jin-yi
authors.initials: JY
authors.lastname: Liu
authors.forename: Jia
authors.initials: J
authors.lastname: Cao
mesh_terms: D000818:Animals; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D015820:Cadherins / Q000235:genetics; D002448:Cell Adhesion / Q000187:drug effects / Q000235:genetics*; D015815:Cell Adhesion Molecules / Q000235:genetics* / Q000378:metabolism; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation / Q000187:drug effects; D000090205:DNA Methyltransferase 3A; D000077209:Decitabine; D004052:Diethylnitrosamine; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D020868:Gene Silencing / Q000187:drug effects; D007136:Immunoglobulins / Q000235:genetics; D008175:Lung Neoplasms / Q000139:chemically induced / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D008297:Male; D008748:Methylcholanthrene; D051381:Rats; D017208:Rats, Wistar; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000235:genetics; D015854:Up-Regulation; D000097584:DNA Methyltransferase 3B
chemical_list: D001374:Azacitidine; D015820:Cadherins; D015815:Cell Adhesion Molecules; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D000077209:Decitabine; D004052:Diethylnitrosamine; D004791:Enzyme Inhibitors; D007136:Immunoglobulins; D008748:Methylcholanthrene; D019717:Tissue Inhibitor of Metalloproteinase-3; D000097584:DNA Methyltransferase 3B; C465040:Cadm1 protein, rat; C000619382:Dnmt1 protein, rat