海军军医大学学报  2025, Vol. 46 Issue (5): 609-620   PDF    
NRAS基因突变结直肠癌临床病理和分子遗传特征分析
蒋英杰1, 刘言2, 孙波2, 何宗杰1, 丁丹1, 白辰光1     
1. 海军军医大学(第二军医大学)第一附属医院病理科,上海 200433;
2. 海军军医大学(第二军医大学)基础医学院,上海 200433
摘要: 目的 分析神经母细胞瘤大鼠肉瘤病毒癌基因同源物(NRAS)基因突变结直肠癌(CRC)患者的临床病理特征与其肿瘤组织中Kirsten大鼠肉瘤病毒癌基因同源物(KRAS)、磷脂酰肌醇4, 5-二磷酸3-激酶催化亚基α(PIK3CA)、v-raf鼠科肉瘤病毒癌基因同源物B1(BRAF)基因突变状态及错配修复(MMR)蛋白、人表皮生长因子受体2(HER-2)蛋白表达的关系。方法 回顾性分析546例NRAS基因突变CRC患者的临床病理资料。采用基因突变联合检测试剂盒(荧光PCR法)检测NRASKRASPIK3CABRAF基因的突变状态,采用免疫组织化学染色EnVision法检测MMR、HER-2蛋白的表达情况,并分析它们与患者临床病理特征的关系。结果 NRAS基因突变CRC患者中,NRAS基因单一位点突变者占98.35%(537/546),NRAS基因双位点突变者占1.65%(9/546),NRASKRAS基因同时突变者占1.47%(8/546),未检出PIK3CABRAF基因突变的患者。NRAS基因突变类型包括Q61R(或Q61K、Q61L、Q61H)突变(266/546,48.72%)、G12D(或G12S)突变(154/546,28.21%)、G13R(或G12C、G12V、G12A、G13V)突变(134/546,24.54%)和A146T突变(1/546,0.18%)。其中,G13R(或G12C、G12V、G12A、G13V)突变更容易发生在原发于直肠的CRC患者(P=0.035);与该位点未突变患者相比,突变患者虽然肿瘤最大径更大(P=0.029),但患者术后无进展生存期更长(P=0.028)。在NRAS基因突变的患者中,HER-2阳性与神经周围浸润相关(P=0.003),MMR蛋白表达缺陷的患者平均年龄更小(P=0.041)且与NRAS双位点突变相关(P=0.018)。结论 NRAS基因突变CRC可能具有独特的临床病理表现与分子表型,为后续CRC的个体化治疗和预后评估提供了潜在依据。
关键词: 结直肠肿瘤    NRAS基因突变    临床病理特征    错配修复蛋白    人表皮生长因子受体2    
Clinicopathological and molecular genetic characteristics of colorectal cancer with NRAS mutations
JIANG Yingjie1, LIU Yan2, SUN Bo2, HE Zongjie1, DING Dan1, BAI Chenguang1     
1. Department of Pathology, The First Affiliated Hospital of Naval Medical University (Second Military Medical University), Shanghai 200433, China;
2. College of Basic Medical Sciences, Naval Medical University (Second Military Medical University), Shanghai 200433, China
Abstract: Objective To analyze the mutation status of Kirsten rat sarcoma viral oncogene homolog (KRAS), phosphatidylinositol-4, 5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), v-raf murine sarcoma viral oncogene homolog B1 (BRAF) genes, and the expression of mismatch repair (MMR) and human epidermal growth factor receptor 2 (HER-2) proteins in tumor tissues of patients with colorectal cancer (CRC) harboring neuroblastoma rat sarcoma viral oncogene homolog (NRAS) gene mutations, and explore their relationships with the clinicopathological characteristics of CRC patients. Methods The clinicopathological data of 546 patients with NRAS mutation CRC were retrospectively analyzed. The mutation status of NRAS, KRAS, PIK3CA, and BRAF genes was detected by AmoyDx amplification refractory mutation system (ARMS)-polymerase chain reaction (PCR) kit (fluorescent PCR method), the expression levels of MMR and HER-2 proteins were detected by immunohistochemical staining EnVision method, and the relationship between them and the clinicopathological characteristics of patients were analyzed. Results The mutation rate of single-point mutations in the NRAS gene was 98.35% (537/546), double-point mutations in the NRAS gene were 1.65% (9/546), and double mutations in the NRAS and KRAS genes were 1.47% (8/546). No patients were found to harbor mutations in the PIK3CA or BRAF genes. The types of NRAS mutations included Q61R (or Q61K, Q61L, Q61H) mutations (266/546, 48.72%), G12D (or G12S) mutations (154/546, 28.21%), G13R (or G12C, G12V, G12A, G13V) mutations (134/546, 24.54%), and A146T mutation (1/546, 0.18%). G13R (or G12C, G12V, G12A, G13V) mutations in the NRAS gene were more likely to occur in the rectum cancer patients (P=0.035); although the tumors had a larger diameter (P=0.029), the patients had a longer progression-free survival after surgery (P=0.028). Among patients with NRAS gene mutations, HER-2 positive expression was associated with perineural invasion (P=0.003), and the patients with deficient MMR were younger on average (P=0.041) and were associated with double-point mutations in the NRAS gene (P=0.018). Conclusion CRC harboring NRAS mutations may have unique clinicopathological characteristics and molecular phenotypes, providing possibilities for individualized treatment and prognosis evaluation of CRC.
Key words: colorectal neoplasms    NRAS mutations    clinicopathological characteristics    mismatch repair protein    human epidermal growth factor receptor 2    

结直肠癌(colorectal cancer,CRC)是全球最常见的恶性肿瘤之一,其发病率和死亡率在全部恶性肿瘤中分别位列第3位和第2位[1-2]。国家癌症中心发布的2022年中国恶性肿瘤流行病学数据显示,中国CRC发病率逐年上升,其发病率和死亡率在全部恶性肿瘤中分别位列第2位和第4位[3]。尽管手术治疗、放化疗和靶向治疗等手段可以延长CRC患者的生存期并提高其生活质量,但晚期患者的预后仍不乐观[4]

大鼠肉瘤病毒癌基因同源物(rat sarcoma viral oncogene homolog,RAS)基因编码的蛋白质具有鸟苷三磷酸(guanosine triphosphate,GTP)水解酶活性,调控细胞的生长和增殖[5]。在癌细胞中,RAS的单个点突变使RAS蛋白无法正常响应细胞内的调控信号,导致下游信号通路持续激活,促进癌细胞的生长和转移[6]。在CRC中,Kirsten大鼠肉瘤病毒癌基因同源物(Kirsten rat sarcoma viral oncogene homolog,KRAS)和神经母细胞瘤大鼠肉瘤病毒癌基因同源物(neuroblastoma rat sarcoma viral oncogene homolog,NRAS)基因的突变率分别为44.7%和7.5%[7-8]。美国肿瘤联合会结直肠癌分期系统(第8版)中明确指出,RAS基因既是预测表皮生长因子受体(epidermal growth factor receptor,EGFR)单抗类药物疗效的重要标志物,又是CRC的预后因子[9]。中国临床肿瘤学会结直肠癌专家委员会也提出,CRC患者检测KRASNRAS基因突变具有重要临床意义[10]

研究发现,KRAS突变的CRC患者可能有其特殊的临床病理特征谱,包括男性多见、组织学类型主要为经典型腺癌、呈中或高分化及微卫星稳定型状态等[11]KRAS不同密码子的突变或相同密码子的不同突变对CRC患者预后的影响不同,如12和61位密码子突变的患者通常比其他位点突变的患者预后差[12]。但目前关于CRC中NRAS基因突变的研究较少,这可能与NRAS突变率较低有关,要获得更可靠的研究结果,仍需通过更大样本量的研究来进一步验证。本研究通过回顾性分析546例NRAS突变的CRC患者肿瘤组织标本的临床病理数据,同时检测了KRAS、磷脂酰肌醇4, 5-二磷酸3-激酶催化亚基α(phosphatidylinositol-4, 5-bisphosphate 3-kinase catalytic subunit alpha,PIK3CA)、v-raf鼠科肉瘤病毒癌基因同源物B1(v-raf murine sarcoma viral oncogene homolog B1,BRAF)基因突变状态及错配修复(mismatch repair,MMR)蛋白、人表皮生长因子受体2(human epidermal growth factor receptor 2,HER-2)蛋白表达情况,分析其可能具有的独特临床病理特征及分子遗传学特征。

1 资料和方法 1.1 生物信息学分析

采用基因表达谱交互分析数据库2(Gene Expression Profiling Interactive Analysis 2,GEPIA2;http://gepia2.cancer-pku.cn)分析多种肿瘤样本与正常组织样本中NRAS的mRNA表达情况。在癌症基因组图谱(The Cancer Genome Atlas,TCGA)数据库(https://portal.gdc.cancer.gov)中共检索到275例CRC肿瘤样本和349例正常结直肠组织样本的NRAS基因表达数据及其相应的临床信息,分析CRC肿瘤样本与正常结直肠组织中NRAS基因表达的差异;按基因表达水平的标准化指标——每百万转录本中的转录本数(transcripts per million,TPM)从高到低排序,前50%的样本归为高表达组(n=135),后30%的样本归为低表达组(n=80),绘制生存曲线分析NRAS基因与CRC患者预后的关系。

1.2 临床资料

收集海军军医大学第一附属医院2015年3月至2024年11月17 800余例通过病理检查明确诊断为原发性结直肠腺癌的患者,筛选出546例有NRAS突变的CRC患者,分析其临床病理资料和分子遗传学特征,包括KRASNRASPIK3CABRAF基因突变状态和MMR、HER-2蛋白表达情况。以2024年11月30日为截止随访日期,通过电话随访结合病历系统检索收集患者术后复发或转移情况以确定无进展生存期(progression free survival,PFS)。纳入标准:CRC患者行根治性或姑息性手术切除治疗,肿瘤组织标本病理诊断明确,术前无放化疗及免疫治疗等治疗史,基因检测显示NRAS突变。排除标准:同时伴发其他类型恶性肿瘤或为转移性恶性肿瘤,患者失访,临床病理资料不完整。共607例患者符合纳入标准,按照排除标准将61例患者排除后,最终546例患者纳入分析。男343例,女203例;年龄26~94岁,平均年龄为(62.46±11.12)岁,其中<40岁16例、40~<60岁185例,≥60岁345例。

基于前期研究[13],将CRC的发病部位依据解剖学位置分为3类:(1)原发于右半结肠(right-sided primary tumor location,RPTL),包括原发于盲肠、升结肠、结肠肝曲和横结肠的CRC;(2)原发于左半结肠(left-sided primary tumor location,LPTL),包括原发于结肠脾曲、降结肠和乙状结肠的CRC;(3)原发于直肠:原发于直肠的CRC。由于Solar Vasconcelos等[14]研究结果显示原发自横结肠与左侧结肠的CRC患者PFS存在差异,故本研究在分析不同原发部位CRC患者的PFS时,将原发自横结肠的CRC单独分组。根据Liebig等[15]的观点规范了神经周围浸润(perineural invasion,PNI)的定义,即肿瘤细胞接近神经结构(至少占神经周长的33%)或位于神经鞘三层结构中的任意一层。本研究通过海军军医大学第一附属医院伦理委员会审核批准(CHEC2022-109)。

1.3 基因突变的检测方法

采用基因突变联合检测试剂盒(荧光PCR法)检测NRASKRASPIK3CABRAF基因的突变状态,目标突变见表 1。该试剂盒只能定性检测甲醛溶液固定石蜡包埋(formalin-fixed paraffin-embedded,FFPE)CRC样本DNA中KRAS(外显子2、3和4)、NRAS(外显子2、3和4)、PIK3CA(外显子20)和BRAF(外显子15)基因的突变,未能具体到某一个体细胞突变而无法获取精准的基因分型结果[7]。因此,本研究统一将试剂盒同时检测的NRAS突变位点进行合并表述:外显子2上发生G12D(或G12S)突变,外显子2上发生G13R(或G12C、G12V、G12A、G13V)突变,外显子3上发生Q61R(或Q61K、Q61L、Q61H)突变,外显子4上发生A146T突变。

表 1 人类KRAS/NRAS/PIK3CA/BRAF基因突变联合检测试剂盒(AmoyDx ARMS-PCR kit)的目标突变 Tab 1 Targeted mutations in human KRAS/NRAS/PIK3CA/BRAF genes of AmoyDx ARMS-PCR kit

1.4 MMR与HER-2蛋白表达的检测方法

采用免疫组织化学染色EnVision法检测HER-2(抗体克隆号:UMAB36)及4个MMR相关蛋白[mutL同源物(mutL homolog,MLH)1(抗体克隆号:OTI4H4)、mutS同源物(mutS homolog,MSH)2(抗体克隆号:RED2)、MSH6(抗体克隆号:EP49)、减数分裂后分离增强蛋白2(postmeiotic segregation increased 2,PMS2)(抗体克隆号:EP51)]的表达。以PBS代替一抗作为阴性对照,已知抗体阳性的切片作为阳性对照。所有一抗均为即用型抗体,购于北京中杉金桥生物技术有限公司;二抗为即用型HRP鼠/兔通用二抗试剂盒,购于上海杰浩生物技术有限公司。操作步骤严格按照试剂说明书进行。其中HER-2以细胞膜呈棕色为阳性染色,0(未染色)或1+(阳性细胞占比<10%)定义为阴性,2+(阳性细胞占比11%~50%)或3+(阳性细胞占比≥10%且细胞膜呈完整、均匀、强着色)定义为阳性。MLH1、MSH2、MSH6、PMS2以细胞核呈棕色为阳性染色,4项指标全部为阳性染色判读为MMR蛋白表达完整(proficient mismatch repair,pMMR),任意一项呈完全阴性染色则判读为MMR蛋白表达缺陷(deficient mismatch repair,dMMR)[10]

1.5 统计学处理

采用SPSS 27.0软件进行统计学分析。计量资料以x±s表示,用Levene检验评估方差齐性,两组间比较采用独立样本t检验。计数资料用频次和百分数表示,组间比较采用χ2检验、连续校正的χ2检验或Fisher确切概率法。采用Kaplan-Meier法进行生存分析,多重比较使用Bonferroni法进行校正。检验水准(α)为0.05。

2 结果 2.1 NRAS基因在CRC患者中的突变状态

利用GEPIA2数据库中的数据比对肿瘤样本和正常样本中NRAS基因的表达情况,结果显示在结肠腺癌、弥漫性大B细胞淋巴瘤、食管癌等肿瘤中NRAS基因突变更为多见(图 1A)。分析TCGA数据库中624例NRAS基因的RNA测序结果、免疫组织化学染色结果及随访预后等统计数据,结果显示NRAS在CRC组织中的表达水平高于正常结直肠组织(P<0.05,图 1B),NRAS基因的高水平表达与CRC患者较长的总生存期相关(P=0.024,图 1C)。因此,进一步探究NRAS基因的特定突变位点在CRC中的意义及其与KRASPIK3CABRAF基因突变状态和MMR、HER-2蛋白表达水平的相关性,对于确定NRAS相关的免疫治疗靶点具有重要意义。

图 1 数据库中CRC患者NRAS基因突变情况及其与预后的关系 Fig 1 Relationship between NRAS mutation status and prognosis in CRC patients from database A: The expression of NRAS gene in different types of tumors (T) and normal tissue (N) in the GEPIA2 database; B: The expression levels of NRAS in colon tumor and normal tissue in the TCGA database; C: The overall survival of patients with different NRAS gene expression levels in the TCGA database. *P<0.05. CRC: Colorectal cancer; NRAS: Neuroblastoma rat sarcoma viral oncogene homolog; ACC: Adrenocortical carcinoma; BLCA: Bladder urothelial carcinoma; BRCA: Breast invasive carcinoma; CESC: Cervical squamous cell carcinoma; CHOL: Cholangiocarcinoma; COAD: Colon adenocarcinoma; DLBC: Lymphoid neoplasm diffuse large B-cell lymphoma; ESCA: Esophageal carcinoma; GBM: Glioblastoma multiforme; HNSC: Head and neck squamous cell carcinoma; KICH: Kidney chromophobe; KIRC: Kidney renal clear cell carcinoma; KIRP: Kidney renal papillary cell carcinoma; LAML: Acute myeloid leukemia-like; LGG: Brain lower grade glioma; LIHC: Liver hepatocellular carcinoma; LUAD: Lung adenocarcinoma; LUSC: Lung squamous cell carcinoma; MESO: Mesothelioma; OV: Ovarian serous cystadenocarcinoma; PAAD: Pancreatic adenocarcinoma; PCPG: Pheochromocytoma and paraganglioma; PRAD: Prostate adenocarcinoma; READ: Rectum adenocarcinoma; SARC: Sarcoma; SKCM: Skin cutaneous melanoma; STAD: Stomach adenocarcinoma; TGCT: Testicular germ cell tumor; THCA: Thyroid carcinoma; THYM: Thymoma; UCEC: Uterine corpus endometrioid carcinoma; UCS: Uterine carcinosarcoma; UVM: Uveal melanoma; TPM: Transcripts per million; GEPIA2: Gene Expression Profiling Interactive Analysis 2; TCGA: The Cancer Genome Atlas; HR: Hazard ratio.

在本研究纳入的546例NRAS基因突变的CRC患者队列中,位居首位的外显子突变类型是Q61R(或Q61K、Q61L、Q61H)突变,占48.72%(266/546);其次是G12D(或G12S)突变(28.21%,154/546)、G13R(或G12C、G12V、G12A、G13V)突变(24.54%,134/546);A146T突变较为罕见,仅占0.18%(1/546)。

2.2 NRAS基因突变CRC患者的临床病理特征

在纳入的546例NRAS基因突变CRC患者中,均未检测到PIK3CABRAF突变。

有8例患者发生罕见的NRASKRAS基因同时突变,占1.47%。其中,男5例、女3例,年龄<60岁3例、≥60岁5例,肿瘤分化程度均为中分化,1例发生淋巴结转移,均无PNI及癌栓形成,病理TNM(pathologic TNM,pTNM)分期Ⅰ期5例、Ⅱ期2例、Ⅲ期1例。至随访结束,术后均未发生复发、转移。8例患者均为pMMR。KRAS基因突变发生在第12号密码子者4例,发生在第13号和第117号密码子者各2例。

有9例患者发生罕见的NRAS基因双位点突变,占1.65%。其中,男5例、女4例,年龄<60岁3例、≥60岁6例,肿瘤分化程度均为中分化,4例发生淋巴结转移,3例有癌栓形成,1例有PNI,pTNM分期Ⅰ期3例、Ⅱ期2例、Ⅲ期4例。截至随访结束,1例术后发生复发、转移。NRAS基因主要突变类型为G12D(或G12S)/G13R(或G12C、G12V、G12A、G13V),占66.67%(6/9),2例为G12D(或G12S)/Q61R(或Q61K、Q61L、Q61H)突变,1例为G13R(或G12C、G12V、G12A、G13V)/Q61R(或Q61K、Q61L、Q61H)突变。

进一步分析NRAS基因外显子2和外显子3突变与CRC患者临床病理特征间的关系,结果显示NRAS基因突变与性别、年龄、肿瘤分化程度、pTNM分期、淋巴结转移、PNI、癌栓、肿瘤性坏死、MMR蛋白表达状态均无明显关系(均P>0.05),但发生NRAS基因G13R(或G12C、G12V、G12A、G13V)突变的患者肿瘤最大径大于未发生该突变的患者(P=0.029)。此外,LPTL患者NRAS基因更容易发生Q61R(或Q61K、Q61L、Q61H)突变(P=0.042),而原发于直肠的患者更容易发生G13R(或G12C、G12V、G12A、G13V)突变(P=0.035)。见表 2

表 2 CRC患者NRAS基因突变与临床病理特征的关系 Tab 2 Relationship between NRAS mutations and clinicopathological parameters in CRC pateints

2.3 NRAS基因突变CRC患者的生存分析

546例患者中,术后复发者51例,未复发者495例。比较不同NRAS基因突变位点患者的PFS,结果显示Q61R(或Q61K、Q61L、Q61H)、G12D(或G12S)位点突变者与相应位点未突变者之间PFS差异无统计学意义(P>0.05),而G13R(或G12C、G12V、G12A、G13V)位点突变者PFS较该位点未突变者更长(P=0.028)(图 2A~2C)。年龄≥60岁与<60岁、pTNM分期Ⅰ~Ⅱ期与Ⅲ~Ⅳ的NRAS突变CRC患者之间比较,PFS差异无统计学意义(均P>0.05,图 2D2E)。相比于LPTL和原发于直肠的患者,RPTL患者(除外9例原发部位为横结肠的患者)的PFS较短(P=0.027、0.033,图 2F);此外,肿瘤原发部位为横结肠的患者术后均未出现复发转移(n=9)。

图 2 546例CRC患者无进展生存期的Kaplan-Meier分析 Fig 2 Kaplan-Meier analysis of progression free survival of 546 CRC patients A-C: Progression free survival analysis among patients with or without NRAS gene mutations at specific sites; D: Progression free survival analysis stratified by age; E: Progression free survival analysis according to pTNM stage; F: Progression free survival analysis based on tumor site. CRC: Colorectal cancer; NRAS: Neuroblastoma rat sarcoma viral oncogene homolog; pTNM: Pathological TNM; RPTL: Right-sided primary tumor location (excluding 9 cases of primary tumors of transverse colon); LPTL: Left-sided primary tumor location.

2.4 NRAS突变CRC患者中MMR蛋白表达与临床病理特征的关系

546例NRAS基因突变的CRC患者中,有533例进行了有效的MMR蛋白免疫组织化学检测,其中dMMR共13例(2.44%),pMMR共520例(97.56%)。dMMR组患者年龄低于pMMR组患者,差异有统计学意义(P=0.041)。dMMR组与pMMR组患者的性别、肿瘤最大径、肿瘤分化程度、pTNM分期、淋巴结转移、PNI、癌栓、肿瘤性坏死及肿瘤原发部位比较,差异均无统计学意义(均P>0.05)。NRAS单一位点突变和双位点突变患者发生dMMR和pMMR的频率分布存在差异,dMMR更多发生于NRAS双位点突变的患者(P=0.018)。见表 3

表 3 NRAS突变CRC患者MMR和HER-2蛋白表达情况与肿瘤病理特征之间的关系 Tab 3 Relationship between MMR and HER-2 protein expression status and clinicopathological parameters in NRAS mutated CRC patients

2.5 NRAS基因突变CRC患者中HER-2蛋白表达与临床病理特征的关系

546例NRAS基因突变CRC患者中,240例患者进行了HER-2蛋白免疫组织化学检测,其中15.00%(36/240)的患者HER-2表达阳性(免疫组织化学染色显示2+或3+)。统计分析发现,NRAS基因突变CRC患者中,HER-2蛋白阳性表达与肿瘤PNI相关(P=0.003);但HER-2蛋白阳性和阴性表达患者的性别、年龄、肿瘤最大径、肿瘤分化程度、pTNM分期、淋巴结转移、癌栓、肿瘤性坏死及肿瘤原发部位比较,差异均无统计学意义(均P>0.05)。见表 3

3 讨论

RAS基因家族成员(包括KRASNRASHRAS)均可通过EGFR酪氨酸激酶受体下游的PIK3CA/Akt和RAS/RAF/MAPK信号通路参与促进细胞的代谢、增殖、存活、生长及血管的生成[16]。这些基因的突变会导致下游信号通路持续激活,从而引起细胞异常增殖分化,与CRC的发生和发展密切相关[17]。目前的研究表明,KRAS/NRASBRAF突变是相互排斥的,PIK3CA突变可以与上述突变在同一肿瘤中并存[18-21]。本研究统计分析的546例NRAS基因突变CRC患者队列中,仅1.46%(8/546)的患者存在NRASKRAS基因的同时突变,而BRAFPIK3CA均未发生突变,这与上述文献报道一致。这种基因突变互斥性的原因可能在于致癌RAS信号转导引起肿瘤形成有一个狭窄的窗口或称“平衡点”(sweet spot)[22]:信号过多时导致生长停滞,而信号过少时导致细胞无法增殖。同时,在某些肿瘤中,RAF下游的信号通路可在没有任何RAS直接参与的情况下强烈活化,表明KRASNRAS基因在肿瘤的发生过程中发挥重要作用,并且其突变在功能上相对冗余[23-24]

尽管有研究表明NRAS突变与CRC临床病理特征之间无明显关系(n=37)[17],但在RAS野生型或KRAS突变的转移性CRC患者中,NRAS突变的患者预后相对较差[25-26]。由于NRAS突变的低检出率,目前缺乏大样本量研究来支持NRAS基因突变与CRC患者临床病理特征之间的相关性。本研究通过对546例NRAS突变CRC患者中3种主要的NRAS基因突变位点与临床病理特征的关系进行统计分析,发现NRAS基因位点G13R(或G12C、G12V、G12A、G13V)突变的患者较该位点未突变的患者肿瘤最大径更大、PFS更长,且肿瘤更易发生于直肠。这种特性使针对具有这类基因位点突变的CRC研究更具价值,有望挖掘更多治疗策略。然而,由于所采用基因检测试剂盒的局限性,本研究未能进行更精确的基因位点分析,有待进一步探索。

NRAS突变CRC患者已被证明不能从EGFR单抗治疗中获益[27-28]。研发针对RAS突变的肿瘤治疗药物是CRC治疗的重点研究方向之一[29-30]。现已经开发出多种针对KRAS突变的抑制剂,其中包括索托拉西布(sotorasib)和阿达格拉西布(adagrasib)[31-33];针对NRAS上游的活性调节因子丝氨酸/苏氨酸蛋白激酶19(serine/threonine kinase 19,STK19)抑制剂和天然产物白屈菜碱(chelidonine)可能有望成为NRAS突变CRC的潜在候选药物[34-35];NRAS下游MAPK通路的丝裂原活化蛋白激酶激酶(mitogen-activated protein kinase kinase,MEK)抑制剂,如MEK1/2抑制剂妥拉美替尼(tunlametinib),在NRAS突变恶性肿瘤患者中显示出较高的客观缓解率[36];而针对其他靶点的药物,如EGFR抑制剂、SOS(son of sevenless)抑制剂及含Src同源结构域2的蛋白酪氨酸磷酸酶2(Src homology 2-containing protein tyrosine phosphatase 2,SHP2)抑制剂等,被发现可以通过阻断RAS活化来抑制肿瘤生长[37]。将这些靶点的分子病理检测从基础研究转化为临床应用,离不开对NRAS基因突变CRC的准确病理诊断及其分子遗传特征的深入理解。

有研究表明,RAS/BRAF野生型同时伴有HER-2扩增突变的转移性CRC患者是抗HER-2治疗的主要获益人群[38]。CRC中HER-2扩增突变的总体发生率为1%~6%[39-40],并且在RAS/BRAF野生型患者中HER-2扩增突变/过表达比例更高(4%~14%)[41]。但本研究统计结果表明,NRAS突变CRC患者中HER-2蛋白表达的阳性率达15%(36/240),且HER-2蛋白阳性表达与肿瘤PNI相关(P=0.003),这表明NRAS突变的CRC患者可能从抗HER-2的靶向治疗中获益。本研究未对HER-2蛋白免疫组织化学检测呈阳性的患者进行荧光原位杂交(fluorescence in situ hybridization,FISH)检测,无法确定是否有HER-2基因扩增,可能导致假阳性结果的出现。因此,NRAS突变的CRC患者能否通过配合HER-2的单抗靶向治疗以获得更好的预后,仍需要更大队列的研究证实。

发生dMMR的CRC属于对免疫治疗敏感的“热肿瘤”[42-43]。dMMR在CRC中占7.6%~15.0%,在转移性CRC中占4%~5%[44-47],且dMMR与CRC患者的肿瘤大小、分化程度及肿瘤分期等临床病理特征有关[48]。本研究中NRAS突变的CRC患者中dMMR占2.44%,比转移性CRC中dMMR的发生率低;发生dMMR的NRAS突变CRC患者平均年龄较小,且与NRAS基因双位点突变相关(P=0.018),其临床意义有待进一步探讨。

综上所述,KRAS/NRAS突变与BRAF突变之间存在互斥,NRAS基因突变的CRC患者肿瘤发生部位与PFS相关,RPTL患者相比于LPTL和原发于直肠的患者PFS较短,而G13R(或G12C、G12V、G12A、G12V)突变的患者PFS更长;NRAS突变CRC患者中HER-2蛋白阳性表达的比例较高,且与PNI相关;dMMR与NRAS基因双位点突变相关。这些研究结果为NRAS基因突变CRC患者靶向治疗策略的优化提供了分子病理学依据。为优化CRC治疗方案,可依据NRAS突变特征采用相应靶向治疗措施,如使用RAF-MAPK通路抑制剂、抗HER-2治疗等,并考虑联合治疗方案以提高疗效。未来研究可以聚焦于深入探索NRAS突变与CRC临床病理特征和治疗反应的关系,开发针对NRAS突变的新型治疗策略和药物,以及制定基于分子特征的个体化治疗方案。

参考文献
[1]
BRAY F, FERLAY J, SOERJOMATARAM I, et al. Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries[J]. CA Cancer J Clin, 2018, 68(6): 394-424. DOI:10.3322/caac.21492
[2]
SUNG H, FERLAY J, SIEGEL R L, et al. Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries[J]. CA Cancer J Clin, 2021, 71(3): 209-249. DOI:10.3322/caac.21660
[3]
郑荣寿, 陈茹, 韩冰峰, 等. 2022年中国恶性肿瘤流行情况分析[J]. 中华肿瘤杂志, 2024, 46(3): 221-231. DOI:10.3760/cma.j.cn112152-20240119-00035
[4]
SIEGEL R L, WAGLE N S, CERCEK A, et al. Colorectal cancer statistics, 2023[J]. CA A Cancer J Clinicians, 2023, 73(3): 233-254. DOI:10.3322/caac.21772
[5]
MUKHOPADHYAY S, VANDER HEIDEN M G, MCCORMICK F. The metabolic landscape of RAS-driven cancers from biology to therapy[J]. Nat Cancer, 2021, 2(3): 271-283. DOI:10.1038/s43018-021-00184-x
[6]
MALAPELLE U, PASSIGLIA F, CREMOLINI C, et al. RAS as a positive predictive biomarker: focus on lung and colorectal cancer patients[J]. Eur J Cancer, 2021, 146: 74-83. DOI:10.1016/j.ejca.2021.01.015
[7]
ZHANG J, ZHENG J, YANG Y, et al. Molecular spectrum of KRAS, NRAS, BRAF and PIK3CA mutations in Chinese colorectal cancer patients: analysis of 1, 110 cases[J]. Sci Rep, 2015, 5: 18678. DOI:10.1038/srep18678
[8]
MAHDI Y, KHMOU M, SOUADKA A, et al. Correlation between KRAS and NRAS mutational status and clinicopathological features in 414 cases of metastatic colorectal cancer in Morocco: the largest North African case series[J]. BMC Gastroenterol, 2023, 23(1): 193. DOI:10.1186/s12876-023-02694-7
[9]
AMIN M B, GREENE F L, EDGE S B, et al. The eighth edition AJCC cancer staging manual: continuing to build a bridge from a population-based to a more "personalized" approach to cancer staging[J]. CA Cancer J Clin, 2017, 67(2): 93-99. DOI:10.3322/caac.21388
[10]
中国临床肿瘤学会(CSCO)结直肠癌专家委员会. 结直肠癌分子标志物临床检测中国专家共识[J]. 中华胃肠外科杂志, 2021, 24(3): 191-197. DOI:10.3760/cma.j.cn.441530-20201225-00679
[11]
ZHU G, PEI L, XIA H, et al. Role of oncogenic KRAS in the prognosis, diagnosis and treatment of colorectal cancer[J]. Mol Cancer, 2021, 20(1): 143. DOI:10.1186/s12943-021-01441-4
[12]
SAEED O, LOPEZ-BELTRAN A, FISHER K W, et al. RAS genes in colorectal carcinoma: pathogenesis, testing guidelines and treatment implications[J]. J Clin Pathol, 2019, 72(2): 135-139. DOI:10.1136/jclinpath-2018-205471
[13]
GAO X H, LI J, LIU L J, et al. Trends, clinicopathological features, surgical treatment patterns and prognoses of early-onset versus late-onset colorectal cancer: a retrospective cohort study on 34067 patients managed from 2000 to 2021 in a Chinese tertiary center[J]. Int J Surg, 2022, 104: 106780. DOI:10.1016/j.ijsu.2022.106780
[14]
SOLAR VASCONCELOS J P, CHEN N, TITMUSS E, et al. Transverse colon primary tumor location as a biomarker in metastatic colorectal cancer: a pooled analysis of CCTG/AGITG CO.17 and CO.20 randomized clinical trials[J]. Clin Cancer Res, 2024, 30(6): 1121-1130. DOI:10.1158/1078-0432.CCR-23-3275
[15]
LIEBIG C, AYALA G, WILKS J A, et al. Perineural invasion in cancer: a review of the literature[J]. Cancer, 2009, 115(15): 3379-3391. DOI:10.1002/cncr.24396
[16]
CHEN K, ZHANG Y, QIAN L, et al. Emerging strategies to target RAS signaling in human cancer therapy[J]. J Hematol Oncol, 2021, 14(1): 116. DOI:10.1186/s13045-021-01127-w
[17]
RIMBERT J, TACHON G, JUNCA A, et al. Association between clinicopathological characteristics and RAS mutation in colorectal cancer[J]. Mod Pathol, 2018, 31(3): 517-526. DOI:10.1038/modpathol.2017.119
[18]
UUTELA A, OSTERLUND E, HALONEN P, et al. Resectability, conversion, metastasectomy and outcome according to RAS and BRAF status for metastatic colorectal cancer in the prospective RAXO study[J]. Br J Cancer, 2022, 127(4): 686-694. DOI:10.1038/s41416-022-01858-8
[19]
KAWAZOE A, SHITARA K, FUKUOKA S, et al. A retrospective observational study of clinicopathological features of KRAS, NRAS, BRAF and PIK3CA mutations in Japanese patients with metastatic colorectal cancer[J]. BMC Cancer, 2015, 15: 258. DOI:10.1186/s12885-015-1276-z
[20]
GUO L, WANG Y, YANG W, et al. Molecular profiling provides clinical insights into targeted and immunotherapies as well as colorectal cancer prognosis[J]. Gastroenterology, 2023, 165(2): 414-428.e7. DOI:10.1053/j.gastro.2023.04.029
[21]
BANDO H, OHTSU A, YOSHINO T. Therapeutic landscape and future direction of metastatic colorectal cancer[J]. Nat Rev Gastroenterol Hepatol, 2023, 20(5): 306-322. DOI:10.1038/s41575-022-00736-1
[22]
LI S, BALMAIN A, COUNTER C M. A model for RAS mutation patterns in cancers: finding the sweet spot[J]. Nat Rev Cancer, 2018, 18(12): 767-777. DOI:10.1038/s41568-018-0076-6
[23]
ULLAH R, YIN Q, SNELL A H, et al. RAF-MEK-ERK pathway in cancer evolution and treatment[J]. Semin Cancer Biol, 2022, 85: 123-154. DOI:10.1016/j.semcancer.2021.05.010
[24]
LEICHT D T, BALAN V, ZHU J, et al. MEK-1 activates C-Raf through a Ras-independent mechanism[J]. Biochim Biophys Acta, 2013, 1833(5): 976-986. DOI:10.1016/j.bbamcr.2013.01.015
[25]
LOREE J M, WANG Y, SYED M A, et al. Clinical and functional characterization of atypical KRAS/NRAS mutations in metastatic colorectal cancer[J]. Clin Cancer Res, 2021, 27(16): 4587-4598. DOI:10.1158/1078-0432.CCR-21-0180
[26]
CERCEK A, BRAGHIROLI M I, CHOU J F, et al. Clinical features and outcomes of patients with colorectal cancers harboring NRAS mutations[J]. Clin Cancer Res, 2017, 23(16): 4753-4760. DOI:10.1158/1078-0432.CCR-17-0400
[27]
BILLER L H, SCHRAG D. Diagnosis and treatment of metastatic colorectal cancer: a review[J]. JAMA, 2021, 325(7): 669-685. DOI:10.1001/jama.2021.0106
[28]
MARTELLI V, PASTORINO A, SOBRERO A F. Prognostic and predictive molecular biomarkers in advanced colorectal cancer[J]. Pharmacol Ther, 2022, 236: 108239. DOI:10.1016/j.pharmthera.2022.108239
[29]
PATELLI G, TOSI F, AMATU A, et al. Strategies to tackle RAS-mutated metastatic colorectal cancer[J]. ESMO Open, 2021, 6(3): 100156. DOI:10.1016/j.esmoop.2021.100156
[30]
SOROKIN A V, KANIKARLA MARIE P, BITNER L, et al. Targeting RAS mutant colorectal cancer with dual inhibition of MEK and CDK4/6[J]. Cancer Res, 2022, 82(18): 3335-3344. DOI:10.1158/0008-5472.CAN-22-0198
[31]
SKOULIDIS F, LI B T, DY G K, et al. Sotorasib for lung cancers with KRAS p.G12C mutation[J]. N Engl J Med, 2021, 384(25): 2371-2381. DOI:10.1056/NEJMoa2103695
[32]
DROSTEN M, BARBACID M. KRAS inhibitors: going noncovalent[J]. Mol Oncol, 2022, 16(22): 3911-3915. DOI:10.1002/1878-0261.13341
[33]
JÄNNE P A, RIELY G J, GADGEEL S M, et al. Adagrasib in non-small-cell lung cancer harboring a KRASG12C mutation[J]. N Engl J Med, 2022, 387(2): 120-131. DOI:10.1056/NEJMoa2204619
[34]
ASQUITH C R M, TEMME L. STK19: a new target for NRAS-driven cancer[J]. Nat Rev Drug Discov, 2020, 19(9): 579. DOI:10.1038/d41573-020-00116-x
[35]
QIAN L, CHEN K, WANG C, et al. Targeting NRAS-mutant cancers with the selective STK19 kinase inhibitor chelidonine[J]. Clin Cancer Res, 2020, 26(13): 3408-3419. DOI:10.1158/1078-0432.CCR-19-2604
[36]
WANG X, LUO Z, CHEN J, et al. First-in-human phaseⅠdose-escalation and dose-expansion trial of the selective MEK inhibitor HL-085 in patients with advanced melanoma harboring NRAS mutations[J]. BMC Med, 2023, 21(1): 2. DOI:10.1186/s12916-022-02669-7
[37]
MOORE A R, ROSENBERG S C, MCCORMICK F, et al. RAS-targeted therapies: is the undruggable drugged?[J]. Nat Rev Drug Discov, 2020, 19(8): 533-552. DOI:10.1038/s41573-020-0068-6
[38]
TOSI F, SARTORE-BIANCHI A, LONARDI S, et al. Long-term clinical outcome of trastuzumab and lapatinib for HER2-positive metastatic colorectal cancer[J]. Clin Colorectal Cancer, 2020, 19(4): 256-262.e2. DOI:10.1016/j.clcc.2020.06.009
[39]
STRICKLER J H, YOSHINO T, GRAHAM R P, et al. Diagnosis and treatment of ERBB2-positive metastatic colorectal cancer: a review[J]. JAMA Oncol, 2022, 8(5): 760-769. DOI:10.1001/jamaoncol.2021.8196
[40]
HASHIMOTO T, TAKAYANAGI D, YONEMARU J, et al. A comprehensive appraisal of HER2 heterogeneity in HER2-amplified and HER2-low colorectal cancer[J]. Br J Cancer, 2023, 129(7): 1176-1183. DOI:10.1038/s41416-023-02382-z
[41]
WANG G, HE Y, SUN Y, et al. Prevalence, prognosis and predictive status of HER2 amplification in anti-EGFR-resistant metastatic colorectal cancer[J]. Clin Transl Oncol, 2020, 22(6): 813-822. DOI:10.1007/s12094-019-02213-9
[42]
WILLIAMS C J M, PEDDLE A M, KASI P M, et al. Neoadjuvant immunotherapy for dMMR and pMMR colorectal cancers: therapeutic strategies and putative biomarkers of response[J]. Nat Rev Clin Oncol, 2024, 21(12): 839-851. DOI:10.1038/s41571-024-00943-6
[43]
SARTORE-BIANCHI A, TRUSOLINO L, MARTINO C, et al. Dual-targeted therapy with trastuzumab and lapatinib in treatment-refractory, KRAS codon 12/13 wild-type, HER2-positive metastatic colorectal cancer (HERACLES): a proof-of-concept, multicentre, open-label, phase 2 trial[J]. Lancet Oncol, 2016, 17(6): 738-746. DOI:10.1016/S1470-2045(16)00150-9
[44]
LE D T, DURHAM J N, SMITH K N, et al. Mismatch repair deficiency predicts response of solid tumors to PD-1 blockade[J]. Science, 2017, 357(6349): 409-413. DOI:10.1126/science.aan6733
[45]
LIZARDO D Y, KUANG C, HAO S, et al. Immunotherapy efficacy on mismatch repair-deficient colorectal cancer: from bench to bedside[J]. Biochim Biophys Acta Rev Cancer, 2020, 1874(2): 188447. DOI:10.1016/j.bbcan.2020.188447
[46]
DIAZ L A Jr, SHIU K K, KIM T W, et al. Pembrolizumab versus chemotherapy for microsatellite instability-high or mismatch repair-deficient metastatic colorectal cancer (KEYNOTE-177): final analysis of a randomised, open-label, phase 3 study[J]. Lancet Oncol, 2022, 23(5): 659-670. DOI:10.1016/S1470-2045(22)00197-8
[47]
JIN Z, SINICROPE F A. Mismatch repair-deficient colorectal cancer: building on checkpoint blockade[J]. J Clin Oncol, 2022, 40(24): 2735-2750. DOI:10.1200/JCO.21.02691
[48]
FAN W X, SU F, ZHANG Y, et al. Oncological characteristics, treatments and prognostic outcomes in MMR-deficient colorectal cancer[J]. Biomark Res, 2024, 12(1): 89. DOI:10.1186/s40364-024-00640-7