摘要目的 研究结直肠癌KRAS、BRAF、PIK3CA等基因突变情况,分析KRAS基因及其他影响靶向治疗效果的基因突变在结直肠癌中的分布.方法 收集结直肠癌标本311例,所有标本均通过石蜡包埋、切片,HE染色后确定肿瘤细胞含量,必要时切割富集肿瘤细胞后采用聚合酶链反应-直接测序法检测KRAS基因第2号外显子的第12和13位密码子、BRAF基因的第11和15号外显子、PIK3CA基因的第9和20号外显子、表皮生长因子受体(EGFR)基因的第18至21号外显子.结果 KRAS、BRAF、PIK3 CA和EGFR等基因在结直肠癌的突变率分别为44.1％(137/311)、5.8％(9/156)、2.6％ (4/156)和1.3％ (2/156).KRAS基因突变阳性标本中第12位密码子的突变占81.0％ (111/137),其中p.G12D发生率最高,占总突变的45.3％ (62/137);第13位密码子的突变占19.0％ (26/137),以c.38G＞A为主(17.5％,24/137).结论 结直肠癌中KRAS基因突变的发生率较高;结直肠癌患者联合检测KRAS、BRAF、PIK3 CA等基因突变可获得额外靶向治疗的预测信息.

abstractsObjective To investigate the mutation frequencies of KRAS,BRAF,PIK3CA and EGFR genes that were effective on the targeted therapies in colorectal carcinoma.Methods The tissue specimens from 331 colorectal cancer patients were collected and subject to KRAS,BRAF,PIK3CA and EGFR mutation analysis.Paraffin-embedded tissue samples were obtained and macrodissection was performed to enrich the tumor cells for DNA extraction when necessary.PCR-based direct DNA sequencing was used to investigate the codons 12 and 13 in exon 2 of KRAS gene,exons 11 and 15 of BRAF gene,exons 9 and 20 of PIK3CA gene and exons 18-21 of EGFR gene.Results Activating mutations were detected in KRAS (44.1％,137/311),BRAF (5.8％,9/156),PIK3CA (2.6％,4/156) and EGFR (1.3％,2/156) in the study cohort of colorectal carcinoma cases.Among KRAS gene mutations,81.0％ (111/137) occurred in codon 12,with p.G12D as the most common variant(45.3％,62/137); 19.0％ (26/137) occurred in codon 13,with 38G ＞ A (G13D) as the most common variant(17.5％,24/137).Conclusions The KRAS mutation frequency is the highest among the four genes (KRAS,BRAF,PIK3CA and EGFT) tested in colorectal carcinoma.The presence of these gene mutations may provide therapeutic information for targeted therapy.Mutation analyses of BRAF and PIK3CA in addition to KRAS should be a part of the standard diagnostic algorithm for colorectal carcinoma patients.