p53和nm23杂合性缺失及表达异常在晚期胃肠癌转移中的作用

Loss of heterozygosity and abnormal expressions of p53 and nm23 in the metastasis of late primary gastrointestinal carcinoma

目的：研究原发胃肠肿瘤及其淋巴结转移癌和肝转移癌中p53和nm23基因的杂合性缺失(loss of heterozygosity,LOH)及其表达情况,探讨基因杂合性缺失和蛋白表达异常在肿瘤细胞转移中的作用,验证转移进展模型的可信性。方法：用多聚酶链反应-单链构象多态性(PCR-SSCP)银染法和免疫组织化学方法分析21例原发癌、16例淋巴结转移癌和21例肝转移癌中p53和nm23基因的杂合性缺失及其表达状况。结果：原发灶、淋巴结转移组织和肝脏转移组织中,p53位点的LOH发生率分别为37.5%、50.0%和68.8%(P＞0.05)．nm23的LOH发生率分别为26.7%、36.4%和40.0%(P＞0.05)；突变型p53蛋白表达率依次为85.7%、87.5%和90.5%(P＞0.05),nm23蛋白表达率分别为76.2%、50.0%和42.9%(肝转移与原发灶相比,P＜0.05)。结论：肿瘤发展过程中,遗传学异常逐步积累,最终转移发生,本研究结果符合转移进展模型理论；p53和nm23的异常改变促进胃肠癌的发展和转移,是肿瘤发展后期的重要分子事件。

Objective： To investigate the loss of heterozygosity （LOH） and expressions of p53 and nm23 in primary gastrointestinal carcinoma and matched nodal and liver metastases, and to confirm the progression model of metastasis. Methods.. Twenty-one patients with primary gastric and colorectal carcinomas, 16 patients with matched nodal metastases, 21 patients with matched liver metastases were recruited in our study regarding genetic changes of two tumor suppressor genes： p53 and nm23. Loss of heterozygosity （LOH） was tested by polymerase chain reaction （PCR）/single strand conformation polymorphisms （SSCP） method. Expressions of p53 and nm23 were detected by immunohistochemistry. Results： The LOH frequencies of p53 gene were 6/16 （37.5%） in primary tumor,6/12 （50.0%） in nodal metastases, and 11/16 （68.8%） in liver metastases, respective ly. While the LOH frequency of nm23 gene were 4/15 （ 26.7%）, 4/11 （36.4% ）, and 6/15 （40.0%）, respectively. Expression rates of mutated p53 and nm23 protein were 85.7%,87.5%, and 90.5% and 76.2% ,50.0%, and 42.9% ,respectively. The intensities of p53 increased and the intensities of nm23 decreased with the progression of metastasis. Conclusion：Gradual accumulation of abnormal genetic alterations during the progression of gastrointestinal carcinoma verifies the progression model of metastasis. Abnormal alterations of p53 and nm23 accelerate the development and metastasis of gastrointestinal carcinoma and are important molecular events in the late stage of tumor development.