The anticancer effects of 5-aza-2'deoxycytidine as a DNA demethylation agent on NNK-induced rat hepatocellular carcimonas

通过每周三次（50 mg/kg腹腔注射）4-甲基亚硝胺-1-（3-吡啶基）-1-丁酮（NNK）处理20周，在雄性Fischer 344大鼠中诱导肝细胞肿瘤。根据组织病理学分析，这些肿瘤被诊断为癌（12个结节/总共28个结节）和腺瘤（16个结节/总共28个结节）。为了确定与NNK暴露于遗传毒性致癌物相关的基因表达变化，对这些RNA进行微阵列分析。与对照组相比，NNK暴露下调了许多基因。甲基化特异性PCR（MSP）检测下调基因的甲基化状态。总的来说，检测到p16和E-cadherin基因启动子区的高甲基化。免疫组织化学染色检测p16和E-cadherin蛋白表达水平。研究了每周一次（1 mg/kg）腹腔注射5-氮杂-2 '脱氧胞苷（5-aza-2' deoxycytidine）作为DNA去甲基化剂对NNK诱导的大鼠肝细胞癌的抗癌作用。我们的研究结果表明，5-氮-2 '脱氧胞苷不影响NNK诱导肝癌的能力，肝癌的进展和甲基化的p16和E-cadherin基因的甲基化状态与NNK处理。

Hepatocellular tumors were induced in male Fischer 344 rats by treatment with the 4-methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK) three times a week (50 mg/kg intraperitoneally injection) for 20 weeks. Based on histopathological analysis, these tumors were diagnosed as carcinomas (12 nodules/total 28 nodules) and adenomas (16 nodules/total 28 nodules).RNA and DNA were isolated from these hepatocellular carcinomas. To determine gene expression changes associated with NNK exposure to genotoxic carcinogens, these RNA were subjected to microarray analysis. A number of genes were down-regulated by NNK exposure compared with controls. The methylation status of these down-regulated genes were determined by methylation-specific PCR (MSP). Overall, the promoter region hypermethylation of the p16 and E-cadherin genes were detected. The protein expression levels of p16 and E-cadherin were examined by immunohistochemical staining. The expression levels of these proteins were also down-regulated.The anticancer effects of 5-aza-2'deoxycytidine once a week (1 mg/kg intraperitoneally injection) as a DNA demethylation agent on NNK-induced rat hepatocellular carcimonas were investigated. Our results suggested that 5-aza-2'deoxycytidine did not influence on the potency of hepatocarcinogenesis induced by NNK, the progression of hepatocellular carcinomas and the methylation status of p16 and E-cadherin genes methylated with NNK treatment.