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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 (4 4%)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。
Objective To evaluate the clinical value of point mutation in codon 12 of K ras oncogene as a tumor marker in plasma DNA. Methods The mutation of the 12th codon of K ras oncogene in DNA and plasma DNA of 32 patients with colorectal cancer was detected by primer-specific polymerase chain reaction (PASP). All PASP amplified The point-mutated PCR product was subjected to Sanger dideoxy chain termination. Results The codon 12 of K ras oncogene was detected in DNA of 14 cases (44%) of colorectal cancer tissues. Of the 13 cases (93%), there were point mutations in plasma DNA of the same type as the tumor DNA. For 18 cases of colorectal cancer without mutation and 5 normal blood donors control group, no mutation in K ras gene was found in plasma DNA. Conclusion The point mutation in codon 12 of K ras oncogene in plasma is expected to become a tumor marker for the diagnosis of colorectal cancer.