CpG island hypermethylation of multiple tumor suppressor genes associated with loss of their protein expression during rat lung carcinogenesis induced by 3-methylcholanthrene and diethylnitrosamine.
The epigenetic mechanisms underlying the tumorigenesis caused by polycyclic aromatic hydrocarbons and nitrosamine compounds such as 3-methylcholanthrene (MCA) and diethylnitrosamine (DEN) are currently unknown. We reported previously that dynamic changes in DNA methylation occurred during MCA/DEN-induced rat lung carcinogenesis. Here, we used the same animal model to further study the evolution of methylation alterations in tumor suppressor genes (TSGs) DAPK1, FHIT, RASSF1A, and SOCS-3. We found that none of these genes were methylated in either normal or hyperplasia tissue. However, as the severity of the cancer progressed through squamous metaplasia and dysplasia to carcinoma in situ (CIS) and infiltrating carcinoma, so methylation became more prevalent. Particularly dramatic increases in the level of methylation, the average number of methylated genes, and the incidence of concurrent methylation in three genes were observed in CIS and infiltrating carcinoma. Similar but less profound changes were seen in squamous metaplasia and dysplasia. Furthermore, methylation status was closely correlated to loss of protein expression for these genes, with protein levels markedly declining along the continuum of carcinogenesis. These results suggest that progressive CpG island hypermethylation leading to inactivation of TSGs might be a vital molecular mechanism in the pathogenesis of MCA/DEN-induced multistep rat lung carcinogenesis.
Liu
Wen-bin
WB
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, PR China.
Ao
Lin
L
Zhou
Zi-yuan
ZY
Cui
Zhi-hong
ZH
Zhou
Yan-hong
YH
Yuan
Xiao-yan
XY
Xiang
Yun-long
YL
Cao
Jia
J
Liu
Jin-yi
JY
D017766:Acid Anhydride Hydrolases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D002273:Carcinogens / Q000633:toxicity; D018899:CpG Islands; D019175:DNA Methylation; D064550:Death-Associated Protein Kinases; D004052:Diethylnitrosamine / Q000633:toxicity; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D016147:Genes, Tumor Suppressor; D008175:Lung Neoplasms / Q000139:chemically induced / Q000235:genetics*; D008297:Male; D008748:Methylcholanthrene / Q000633:toxicity; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism; D000099170:Bis(5'-adenosyl)triphosphatase
D017766:Acid Anhydride Hydrolases; D051017:Apoptosis Regulatory Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002273:Carcinogens; D064550:Death-Associated Protein Kinases; D004052:Diethylnitrosamine; D008748:Methylcholanthrene; D009363:Neoplasm Proteins; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D025521:Tumor Suppressor Proteins; D000099170:Bis(5'-adenosyl)triphosphatase; C411762:RASSF1 protein, human; C106644:SOCS3 protein, human; C579096:DAPK1 protein, human