CN105567837B - 检测K-ras基因突变的引物和探针体系、方法及试剂盒 - Google Patents

检测K-ras基因突变的引物和探针体系、方法及试剂盒 Download PDF

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CN105567837B
CN105567837B CN201610071654.2A CN201610071654A CN105567837B CN 105567837 B CN105567837 B CN 105567837B CN 201610071654 A CN201610071654 A CN 201610071654A CN 105567837 B CN105567837 B CN 105567837B
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陈晓琦
张传雷
王新亭
张闪闪
刘姝
陈欣菊
冀爱英
刘香丽
张宇
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Abstract

本发明涉及一种检测K‑ras基因突变的引物和探针体系,包括SEQ ID NO:1~13所示的核苷酸序列;还公开了其检测方法,包括配置50μL荧光PCR反应体系、进行荧光PCR扩增程序、结果判定等步骤。本发明可同时检测KRAS基因7种突变;最多可以检测1~10拷贝的基因突变;特异性强,在10~30ng野生型DNA背景下不受干扰;检测性能突出,在10ng DNA背景下,可以检测出1~10拷贝的基因突变。

Description

检测K-ras基因突变的引物和探针体系、方法及试剂盒
技术领域
本发明属于基因工程技术领域,具体涉及一种检测K-ras基因突变的引物和探针体系、方法及试剂盒。
背景技术
K-ras基因是EGFR信号通路中的重要分子之一,是首个影响结直肠癌临床治疗决策的生物标记物,其所编码的K-ras蛋白为EGFR信号通路下游区的一种分子G蛋白,当K-ras基因发生突变后,会导致该信号通路异常活化,从而对EGFR单抗治疗无效。因此,K-ras基因状态与针对EGFR的靶向药物(例如西妥昔单抗和帕尼单抗等)的疗效有关,《09年NCCN非小细胞肺癌临床实践指南》明确指出:如果K-ras基因发生了突变,则不建议病人使用特罗凯(Tarceva/厄洛替尼/Erlotinib)进行分子靶向治疗。
许多肿瘤中K-ras基因的突变率较高,在白血病、肺癌、直肠癌、胰腺癌等癌症中,K-ras突变很常见,尤其是在结直肠癌和非小细胞肺癌中,突变率甚至可达30~60%和21~28%。同时在上述两种肿瘤中约80~90%的K-ras基因突变发生在突变热点2号外显子12、13密码子上,其中的7个突变热点:G12C、G12R、G12S、G12V、G12D、G12A、G13V/D占到了全部突变的90%以上。
因此,检测K-ras基因上述7个突变热点,可准确判断患者对该类治疗的预测疗效,以供临床医师参考,也能尽最大的努力筛选出有效人群,避免错过治疗。
发明内容
针对上述问题,本发明提供一种检测人K-ras基因突变的引物和探针体系,可同时检测KRAS基因7种突变,最多可以检测1~10拷贝的基因突变,特异性强,在10~30ng 野生型DNA背景下不受干扰,检测性能突出,在10ng DNA背景下,可以检测出1~10拷贝的基因突变。
为解决以上技术问题,本发明通过以下技术方案实现:
设计一种检测K-ras基因突变的引物和探针体系,包括SEQ ID NO:1~13所示的核苷酸序列,所述引物或探针具有以下特点:
(1)本发明引进LNA修饰的野生探针封闭野生模板,探针3’-末端用PO4修饰或NH2修饰封闭阻止Taq DNA聚合酶的延伸;
(2)本发明特异性引物3’-末端碱基采用LNA修饰;
(3)本发明特异性引物3’-末端起第二个碱基引入脱氧次黄嘌呤核苷修饰。
设计一种检测K-ras基因突变的方法,包括以下步骤:
(1)合成所述引物和探针;
(2)配置50μL荧光PCR反应体系:Buffer(10×)5μL,Mg2+ 1.0~5mmol/L,dNTP 100~1000nmol/L,上述每个引物100~500nmol/L,上述每个探针100~1000nmol/L,Taq DNA聚合酶1U~3U,DNA模板5~10ng;
(3)进行荧光PCR扩增程序:酶激活,95℃ 10min;突变富集,95℃ 30s,68℃ 30,64℃ 50s,72℃ 25s,16个循环;扩增检测,30个循环,95℃ 30s,58℃ 32s,72℃ 18s,于“58℃32s”该步骤收集荧光信号FAM和HEX;
(4)结果判定:检测体系中,HEX通道15<Ct<22,表明上样在可控范围内,结果有效;以FAM信号通道为阳性判断标准,曲线呈“S”曲线,且Ct<29 为阳性,Ct为0则为阴性。
所述DNA模板包括FFPE组织及外周血游离DNA。
利用上述引物和/或探针中的至少一种,可制成用于检测K-ras基因突变的试剂盒。
本发明具有以下积极有益技术效果:
(1)本发明改良现有扩增受阻检测体系,摈弃ARMS引物设计中引入错配的原则,将特异性检测突变引物3’-末端起第2碱基采用脱氧次黄嘌呤核苷代替。脱氧次黄嘌呤核苷(dI)是天然存在的碱基,与A、G、C、T结合力弱,当与其它碱基结合时,会比其它碱基错配相对更稳定。脱氧次黄嘌呤与其它碱基的结合能力为:dI:dC> dI:dA> dI:dG> dI:dT,在DNA聚合酶的催化下,脱氧次黄嘌呤优先与dC结合。
(2)本发明在特异性检测突变引物的3’-末端碱基采用LNA修饰,提高了检测的特异性和敏感性。
(3)本发明引入了LNA修饰的封闭野生型的LNA探针,使得可以在高背景下检测低拷贝。
因此,本发明可同时检测KRAS基因7种突变;最多可以检测1~10拷贝的基因突变;特异性强,在10~30ng 野生型DNA背景下不受干扰;检测性能突出,在10ng DNA背景下,可以检测出1~10拷贝的基因突变。
附图说明
图1 为本发明阳性结果判定标准对照示意图。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白,以下结合具体实施例,对本发明进一步详细说明。应当理解,此处所描述的具体实施例仅仅用以解释本发明,并不用于限定本发明。以下实施例中所涉及的原料,如无特别说明均为市售,所涉及检测方法如无特别说明,则均为常规方法。
实施例1
一种检测KRAS基因 7种突变的试剂盒,包括SEQ ID NO:1~13所示的核苷酸序列,见表1。
表1引物和探针
实施例2
一种检测K-ras基因7种突变的方法,包括以下步骤:
(1)配置50μL荧光PCR反应体系:Buffer(10×)5μL,Mg2+ 2.0mmol/L,dNTP300nmol/L,实施例1每个引物200nmol/L,实施例1每个探针300nmol/L,Taq DNA聚合酶2U,DNA模板10ng,余量为ddH2O;
(2)进行荧光PCR扩增程序:酶激活,95℃ 10min;突变富集,95℃ 30s,68℃ 30,64℃ 50s,72℃ 25s,16个循环;扩增检测,30个循环,95℃ 30s,58℃ 32s,72℃ 18s,于“58℃32s”该步骤收集荧光信号FAM和HEX;
(3)结果判定:检测体系中,HEX通道15<Ct<22,表明上样在可控范围内,结果有效;以FAM信号通道为阳性判断标准,曲线呈“S”曲线,且Ct<29 为阳性,Ct为0则为阴性。
实施例3
一、K-ras突变检测体系和阈值的确定
(1)突变检测体系:通过长期的反复测试研究,本发明确定K-ras检测的上样量为10ng,将K-ras基因7种突变分别装入八排管的7个孔,第8个为外控;
(2)阳性判定:阳性判定需要满足以下要求:
首先,PCR阴性对照没有扩增曲线,有标明有污染,结果不可靠;
其次,检测103 copies阳性突变,Ct<23,否则性能不稳定;
第三,外控的Ct值为:17~25,确保上样量的准确性;
最后,检测样品,曲线成“S”,且Ct<30。
满足上述条件,待检测样品K-ras基因突变为阳性。
结果无论有无突变,内参HEX通路都有曲线可以观察到,如果没有,则表明实验存在错误,需要重新实验,见图1。
二、检测结肠癌K-ras基因突变
62例结肠癌样本,已经采用厦门艾德ADX-ARMS 试剂盒标定,来评价本发明实施例2检测临床样本的准确性。检测有出入或阳性的样本采用COLD-PCR后,亚克隆测序鉴定。
表2本发明检测与ADX-ARMS结果对比
通过与对62例临床样本的检测,结果与厦门艾德完全一致,且主要为Gly12Ser(GGT>AGT)、Gly12Val(GGT>GTT)、Gly12Asp(GGT>GAT)、Gly12Ala(GGT>GCT)和Gly13Asp(GGC>GAC),具体的结果参加表2。对两种方法检测判定为阳性的样本采用COLD-PCR测序,结果完成正确。在结肠癌中,K-ras的突变率约为32.8%左右。
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Claims (2)

1.一种检测K-ras基因突变的引物和探针体系,其特征在于:由SEQ ID NO:1~13所示的核苷酸序列组成。
2.一种检测K-ras基因突变的试剂盒,包括权利要求1所述引物和探针。
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