结直肠癌Ras、BRAF和PIK3CA基因突变分析及与临床病理特征的关系

Relationship between Ras,BRAF,PIK3CA mutation status and clinicopathological characteristics in colorectal cancer

目的分析结直肠癌患者中Ras(K-Ras/N-Ras)、BRAF和PIK3CA基因突变情况及其与临床病理特征的关系。方法回顾性分析2013年12月至2014年10月于北京大学肿瘤医院消化肿瘤内科接受诊治的200例结直肠癌患者的肿瘤组织标本,采用PCR扩增-直接测序法检测Ras,包括K-Ras(第2、3、4外显子)、N-Ras(第2、3、4外显子)、BRAF(第15外显子)及PIK3CA(第9、20外显子)基因的突变状态,分析其与结直肠癌临床病理特征的关系。结果 200例患者中存在Ras基因突变92例(46.0%),其中K-Ras基因突变87例(43.5%),主要发生在外显子2,N-Ras基因突变5例(2.5%);其中1例患者存在KRas、N-Ras基因同时突变。存在BRAF基因突变15例(7.5%),突变类型均为V600E,且与K-Ras突变存在排他性。存在PIK3CA基因突变9例(4.5%),可与Ras或BRAF基因突变共存。Ras(K-Ras/N-Ras)基因在年龄≥65岁患者中的突变率明显高于<65岁者(P<0.05),其表达与性别、原发部位、组织学类型、分化程度、TNM分期、区域淋巴结转移、远处转移、术后复发转移均无关(P均>0.05)。BRAF、PIK3CA基因在原发部位为右半结肠患者中的突变率明显升高(P<0.05),但与年龄、性别、组织学类型、分化程度、TNM分期、区域淋巴结转移、远处转移、术后复发转移均无关(P>0.05)。结论 N-Ras、PIK3CA基因在中国结直肠癌患者中的突变率较低。K-Ras、N-Ras基因突变与年龄相关,BRAF、PIK3CA基因与肿瘤原发部位相关;对结直肠癌患者进行Ras(K-Ras/N-Ras)、BRAF及PIK3CA基因的联合检测将会为提高临床靶向治疗的疗效提供更加可靠的依据。

Objective To understand the mutation status of Ras （K-Ras/N-Ras）, BRAF, PIK3CA and its associations with clinicopathological characteristics in colorectal cancer （CRC）. Methods Tumor specimens were collected from 200 CRC patients treated in Peking University Cancer Hospital from December 2013 to October 2014. The mutation status of Ras, including K-Ras （exon 2, 3 and 4）, N-Ras （exon 2, 3 and 4） ,BRAF （exon 15） and PIK3CA （exon 9, 20） were detected by direct sequencing. The relationships be- tween the gene mutations and clinicopathological parameters were analyzed. Results Ras mutations were found in 92 （46. 0%） of 200 patients, including 87 cases（43.5%） of K-Ras, of which occurred mainly in exon 2, and 5 cases of N-Ras. One patient carried K-Ras mutation and N-Ras mutation simultaneously. BRAF mutations were found in 15 patients （7. 5%） and all types of BRAF mutation were V6OOE. K-Ras and BRAF mutations were mutually exclusive. PIK3CA mutations were found in 9 patients（4. 5% ）, which appeared simul- taneously in Ras/BRAF mutation tumors. Also, the mutation rate of Ras （K-Ras/N-Ras） in patients ≥65 years was higher than that in patients 〈65 years （P〈0. 05）. Other clinicopathological features, such as gender, location of the tumor, histological classification, tumor differentiation, TNM staging, local lymph node metastasis, distant metastasis, and post-operative recurrence and metastasis had no rela- tionship with Ras （K-Ras/N-Ras） gene mutations （P〉0. 05）. BRAF/PIK3CA mutation rates were hizher in rizht side colon tumors （P〈0.05）. No significant associations were observed between BRAF/PIK3CA mutations and gender, age, histological classification, tumor differentiation, TNM staging, local lymph node metastasis, distant metastasis, and post-operative recurrence and metastasis（ P〉0. 05）. Conclusion N-Ras/PIK3CA genes were rarely mutated in Chinese CRC patients. K-Ras/N-Ras mutation were associated with age, while BRAF/PIK3CA mutation were only associated with location of the tumor. Combined detection with K-Ras, N-Ras, BRAF and PIK3CA gene in colorectal cancer patients will provide more reliable basis for clinical targeted therapy.