大肠癌患者血浆DNA中K-ras癌基因突变的检测

目的 评价血浆DNA中K－ras癌基因第12密码子点突变作为肿瘤标记物的临床应用价值。方法 用引物序列特异性聚合酶扩增链式反应（PASP）检测了32例大肠癌患者肿瘤组织DNA、血浆DNA中K－ras癌基因第12密码子点突变，对所有PASP法扩增得到的含点突变的PCR产物进行Sanger双脱氧链终止法测序。结果 14例（44％）大肠癌肿瘤组织DNA中存在K－ras癌基因第12密码子点突变；其中的13例（93％）在血浆DNA中存在与其肿瘤组织DNA相同类型的基因点突变。对于18例肿瘤标本DNA未见突变的各期大肠癌及5例正常献血员对照组，在其血浆DNA中也无一发现K－ras基因突变。结论 血浆DNA中K-ras癌基因第12密码子点突变有望成为一个肿瘤标志物应用于大肠癌的诊断。

Detection of K-ras mutation in DNA extracted from the plasma of patients with colorectal cancer

Objective The purpose of this study was to determine the value of K-ras mutation in DNA extracted from the plasma as clinical indicator of colorectal cancer. Methods Point mutation at codon 12 of K-ras gene was assayed by polymerase chain reaction of sequence-specific primers in DNA extracted from the plasma and tumors from 32 patients with colorectal cancer. The mutation was further confirmed by dideoxy-mediated chain-termination method of DNA sequencing. Results Fourteen patients (44%) had a codon 12 K-ras mutation within their primary tumors and identical mutations were found in the plasma DNA of 13 patients (93%). Mutant DNA was not detected in the plasma specimens of 18 patients whose tumors tested negative for K-ras alterations or in 5 healthy control subjects. Conclusion Preliminary results suggest the detection of K-ras mutations in circulating DNA extracted from the plasma specimens may have some clinical uti- lity in the detection of colorectal cancer.