左金丸对大肠癌APC表达及DNA甲基转移酶活性的影响

目的研究左金丸对结肠腺瘤性息肉基因（adenomatous polyposis coli,APC）的表达及DNA甲基转移酶（DNA methyltransferase,Dnmts）各亚型Dnmt1、Dnmt3a、Dnmt3b活性的影响,探讨大肠癌的发病机制及左金丸中药的抑癌机理。方法将120只Wistar大鼠按随机数字表法分为3组：正常组、左金丸组和对照组,每组40只。正常组为健康大鼠不做任何处理,左金丸组和对照组大鼠每周注射1次化学致癌剂1,2-二甲基酰肼（1,2-di meth-ylhydrazine,DMH）共12周,左金丸组从注射药物开始每天灌服左金丸汤剂,对照组与正常组灌服同等体积的生理盐水,分别在第11、21、34周将部分大鼠处死,切取肿物、进行切片、HE染色、病理观察Duke分期,用Western blot-ting半定量法检测不同肿瘤时期APC蛋白的表达;Elisa方法检测Dnmts活性。结果 APC相对蛋白含量比较：正常组〉左金丸组〉对照组,各组两两比较差异均有统计学意义（P〈0.05或P〈0.01）,但与肿瘤Dukes分期无关;Dnmt1、Dnmt3a、Dnmt3b的活性比较：对照组〉左金丸组〉正常组,各组两两比较差异均有统计学意义（P〈0.05或P〈0.01）,其中对照组中Dnmt1、Dnmt3b的活性与肿瘤Dukes分期有关,随着肿瘤浸润程度的增加而升高。结论 APC蛋白参与了结直肠癌的发生,并且是肿瘤形成的早期事件,与肿瘤的发展进程无关;Dnmt1、Dn-mt3a、Dnmt3b参与了结直肠癌的发生过程,且Dnmt1、Dnmt3b活性升高与结直肠癌进展有关;左金丸组APC蛋白表达量的增加及甲基转移酶活性的降低可能跟左金丸的抑癌作用有关。

Effect of Zuojin Pill on Expression of APC and Activity of DNA Methyltransferase in Colorectal Adenomas

Objective To investigate the effect of Zuojin Pill on the expression of APC gene and the activity of DNA methyltransferases（Dnmt1,Dnmt3a and Dnmt3b）,and to discuss the pathogenesis of colorectal carcinoma（CRC）and anticancer mechanism of Zuojin Pill.Methods A total of 120 rats were randomly divided into three groups：normal group,Zuojin Pill group and control group.No treatment was given in normal group.Rats in Zuojin Pill group and control group were injected with a carcinogenic substance 1,2-dimethyl hydrazine（1,2-DMH） once a week for 12 weeks.In addition,rats in Zuojin Pill group were gavaged with Zuojin decoction and rats in control group were given the same volume of normal saline once a day.Some rats in each group were killed at 11,21 and 34 weeks after treatment,and the tumors were sliced into sections,which were stained with HE and distinguished by pathological examination.The expression of APC in different phases was detected by Western blot analysis and the activities of Dnmts were determined by ELISA.Results The expression of APC in normal group was significantly higher than that in Zuojin Pill group（P0.01）,which was significantly higher than that in control group（P0.05）.There was no correlation between APC expression and Duke＇s staging.The activities of Dnmts in control group were significantly higher than those in Zuojin Pill group（P0.01）,which were significantly higher than those in normal group（P0.05）.The activities of Dnmt1 and Dnmt3b increased with tumor immersion.Conclusion APC protein plays a early role in the development of colorectal tumors,but is not correlated with tumor stage.Dnmt1,Dnmt3a and Dnmt3b are related to the development of colorectal carcinoma.The anti-cancer function of Zuojin pill may be mediated by increased expression of APC and decreased activities of Dnmts.