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目的检测直肠癌术前放疗前后原癌基因Kirsten大鼠肉瘤病毒转化基因(K-ras基因)突变率的变化,从细胞遗传学方面深入研究放射治疗对直肠癌的作用。方法pTNMⅡ期和Ⅲ期直肠癌病人40例。病人术前行40Gy放疗,放疗前和术中分别取癌组织、距边缘2、4和6cm正常黏膜采用聚合酶链反应单链构象多态性分析(PCRSSCP)法检测K-ras基因第12密码子突变。结果癌组织中K-ras基因突变率显著高于癌周正常黏膜,同时距癌边缘2cm黏膜的K-ras基因突变率显著高于距癌边缘4、6cm黏膜的。放疗后癌组织和距癌边缘2cm黏膜的K-ras基因突变率与放疗前相比显著降低。结论距肿瘤2cm之内的黏膜有较高的K-ras基因突变率,向恶性转化的可能较大,放疗后癌组织和癌旁黏膜K-ras基因突变率显著降低,因此,放疗可能抑制癌旁黏膜恶变的早期事件,这可能是放疗能增加手术切除率和保肛率的原因。
Objective To detect the mutation rate of Karsten rat sarcoma virus (K-ras) gene before and after radiotherapy for rectal cancer, and to study the effect of radiotherapy on rectal cancer from the perspective of cytogenetics. Methods pTNM Ⅱ and Ⅲ rectal cancer patients 40 cases. Patients preoperative 40Gy radiotherapy, before and during radiotherapy and cancer were taken from the edge of normal mucosa 2, 4 and 6cm by polymerase chain reaction single-strand conformation polymorphism (PCRSSCP) method to detect K-ras gene 12 password Sub-mutation. Results The mutation rate of K-ras gene in cancerous tissue was significantly higher than that in normal mucosa. The mutation rate of K-ras gene in 2cm mucosal margin was significantly higher than that in mucosa 4,6cm away from the edge of carcinoma. The mutation rate of K-ras gene in cancer tissue and 2cm mucosa from the edge of cancer was significantly lower than that before radiotherapy. Conclusion The mucosa within 2cm away from the tumor has a higher mutation rate of K-ras gene and a higher possibility of malignant transformation. The mutation rate of K-ras gene in cancerous tissue and adjacent mucosa after radiotherapy is significantly lower. Therefore, radiotherapy may inhibit cancer Early mucosal malignancy of the early events, which may be radiotherapy can increase the surgical resection rate and anal sphincter of the reasons.