T790M突变与EGFR-TKI耐药后治疗策略

表皮生长因子受体酪氨酸激酶抑制剂（epidermal growth factor receptor-tyrosine kinase inhibitor,EGFR-TKI）治疗非小细胞肺癌已获得较好的疗效,患者生活质量明显改善。但EGFR-TKI耐药似乎成为了靶向治疗的瓶颈,耐药的产生可能存在多种机制,包括T790M突变、K-ras基因突变、C-Met基因扩增、BRAF基因突变、BIM多态性缺失、EML4-ALK融合基因突变及上皮间充质转化等,其中最常见的是T790M基因突变。目前研究表明,T790M基因还可能具有一定预测疗效和预后的作用。本文将简要介绍T790M基因的发现、起源、作用机制及预后,并主要针对EGFR-TKIs耐药后的治疗策略进行综述。     

AZD9291治疗非小细胞肺癌的临床转化研究

近年来在非小细胞肺癌(non-small cell lung cancer,NSCLC)治疗领域里程碑式的改变是采用EGFR-酪氨酸激酶抑制剂(tyrosine kinase inhibitor,TKI)治疗表皮生长因子受体(epidermal growth factor receptor,EGFR)基因突变阳性的晚期患者.但大部分患者在使用该药治疗9～11个月后陆续出现耐药现象.研究发现EGFR基因20号外显子T790M基因突变是导致EGFR TKI耐药的最主要因素,因此特异性靶向T-790M抗药性突变的EGFR抑制剂AZD9291受到了极大的关注.本文对AZD9291治疗非小细胞肺癌的临床转化进行了综述.     

非小细胞肺癌患者外周血表皮生长因子受体T790M检测与奥希替尼疗效的相关性研究

摘 要：［目的］ 评估非小细胞肺癌患者第一代表皮生长因子受体-酪氨酸激酶抑制剂（epidermal growth factor receptor-tyrosine kinase inhibitor,EGFR-TKI）获得性耐药后外周血EGFR T790M突变的阳性率和用外周血T790M检测结果预测奥希替尼疗效的可靠性。［方法］ 回顾性分析2017 年3月至2018年6月经第一代EGFR-TKI治疗后获得性耐药且使用超级扩增阻滞突变系统(ultra-amplification refractory mutation system,Ultra-ARMS )进行外周血EGFR T790M检测的原发性非小细胞肺癌患者。评估血T790M阳性患者使用奥希替尼的疗效。［结果］共有103例符合标准的第一代EGFR-TKI获得性耐药患者,其中28例（27.2%,28/103）血T790M阳性,75例（72.8%,75/103）血T790M阴性。血T790M阳性患者中,接受奥希替尼治疗有23例：部分缓解（partial response,PR） 15例,疾病稳定（stable disease,SD）6例,疾病进展（progression of disease,PD） 2例。疾病控制率(disease control rate,DCR) 91.3%,客观有效率（objective response rate,ORR)65.2%。奥希替尼治疗的中位无进展生存时间（progression free survival,PFS） 12.5个月（95%CI：11.2~13.8）。有9例血T790M阴性患者后续进行了组织检测,3例在组织中检测到T790M突变。有6例血T790M阴性的患者虽未再行组织检测,但要求试用奥希替尼靶向治疗,1例患者获得了PR,1例SD（PFS超过5个月）。［结论］对第一代EGFR-TKI获得性耐药后未能再次行组织活检的非小细胞肺癌患者,Ultra-ARMS方法检测血T790M阳性可预测奥希替尼疗效。血T790M检测阴性的患者建议再次取组织进行T790M检测以排除假阴性。组织检测是T790M检测的金标准,血T790M检测可作为补充。     

EGFR T790M突变丰度对奥希替尼治疗晚期非小细胞肺癌疗效的影响

摘 要：［目的］ 分析奥希替尼治疗晚期非小细胞肺癌疗效,并探索ddPCR方法外周血检测表皮生长因子（epidermal growth factor,EGFR）T790M突变的丰度与奥希替尼疗效之间的关系。［方法］ 回顾性分析104例接受奥希替尼治疗的Ⅲb~Ⅳ期非小细胞癌肺癌患者,采用ddPCR法测定外周血T790M突变丰度,采用Kaplan-Meier法和Cox模型进行生存预后分析,并探索疗效相关T790M突变丰度的界值。［结果］ 外周血EGFR T790M突变丰度中位值为0.89%（0.02%~35.10%）。将突变丰度分为＜5.00%和≥5.00%两组,客观缓解率分别为46.5%和88.9%（P=0.001）,中位无进展生存期分别为8.80个月和21.83个月（P=0.039）。Cox回归分析显示,初治时基因类型（EGFR 19外显子缺失和21外显子L858R突变）、PS评分、外周血EGFR T790M突变丰度分组（＜5.00%和≥5.00%）是奥希替尼治疗患者PFS的独立影响因素。［结论］ EGFR T790M突变丰度可能可预测奥希替尼治疗的晚期EGFR T790M突变NSCLC患者的有效率和无进展生存期。     

非小细胞肺癌患者外周血中表皮生长因子受体突变检测的研究进展

 非小细胞肺癌（NSCLC）治疗手段以手术、化疗、放疗和靶向治疗为主。随着靶向治疗研究的进展,发现有表皮生长因子受体（EGFR）突变者接受小分子酪氨酸激酶抑制剂（TKI）靶向治疗效果佳,进行这类药物治疗前的筛选是个体化治疗的前提,目前以组织标本基因检测为金标准。但是进展期患者肿瘤组织难以获得,外周血中游离DNA的EGFR突变检测便成为一种选择。文章综述了国内外研究者在外周血（血清、血浆）中进行EGFR 外显子19／21（exon19／21）及耐药基因外显子20的T790M突变（exon20 T790M）检测的情况与进展。     

晚期非小细胞肺癌T790M突变的检测方法及临床意义

表皮生长因子受体酪氨酸激酶抑制剂（epidermal growth factor receptor-tyrosine kinase inhibitors,EGFR-TKIs）是EGFR活化突变阳性晚期非小细胞肺癌（non-small cell lung cancer,NSCLC）患者的有效治疗药物,然而,几乎所有服药患者最终将出现耐药,第20号外显子的T790M点突变可能是导致耐药的机制之一,如何敏感、准确地检测T790M基因突变是技术关键,外周血检测因创伤小、操作简便而成为近几年研究热点,实时定量检测血浆T790M突变有望成为监测EGFR-TKI疗效的有效途径。目前,T790M突变的临床意义尚存争议,近年来出现的第三代EGFR-TKI对T790M突变阳性患者的有效率较高,使得克服T790M突变导致的耐药成为可能。本文就T790M检测方法及其临床意义进行综述。      

晚期非小细胞肺癌厄洛替尼耐药研究进展

酪氨酸激酶抑制剂(TKI)厄洛替尼作为晚期非小细胞肺癌(NSCLC)靶向治疗药物,延长了患者的生存时间,但其耐药性的发生成为其进一步应用的瓶颈.现已证实T790M突变、KRAS突变、c-met癌基因扩增在耐药机制中起重要作用.针对不同耐药机制,第2代TKI的应用、再次应用化疗或厄洛替尼以及针对失败模式进行后续治疗等多项临床试验不断开展.     

第三代EGFR-TKIs在非小细胞肺癌中的耐药机制及应对策略

表皮生长因子受体酪氨酸激酶抑制剂(epidermal growth factor receptor tyrosine kinase inhibitors,EGFR-TKIs)靶向治疗相对于传统化疗具有很大的优势,已成为晚期非小细胞肺癌EGFR敏感突变患者的一线治疗方案。然而,耐药现象不可避免地发生。EGFR第20号外显子的T790M突变是第一、二代EGFRTKIs的主要耐药机制。第三代EGFR-TKIs,如AZD9291、CO-1686等可克服T790M耐药,并在临床试验中显示出良好的治疗效果,然而,第三代EGFR-TKIs的耐药同样不可避免,该文就第三代EGFR-TKIs的耐药机制及目前的应对策略进行综述。     

表皮生长因子受体酪氨酸激酶抑制剂的耐药机制及应对策略

 表皮生长因子受体（EGFR）酪氨酸激酶抑制剂(EGFR-TKI)对含有EGFR突变的非小细胞肺癌治疗效果较好,但仍有部分患者对酪氨酸激酶抑制剂（TKI）原发耐药,而对TKI治疗敏感的患者最终无法避免继发耐药导致肿瘤进展,其主要分子机制是T790M突变和MET扩增。研究新的靶向治疗药物及联合应用药物克服耐药是目前临床科研的主题。     

非小细胞肺癌表皮生长因子受体T790M突变的研究进展

摘 要：临床工作中表皮生长因子受体—酪氨酸激酶抑制剂（epidermal growth factor receptor-tyrosine kinase inhibitor，EGFR-TKI）耐药的非小细胞肺癌（non-small cell lung cancer，NSCLC）患者须进行EGFR T790M突变的检测。由于多种原因一些患者无法通过组织再活检获得满意基因检测结果，而液体活检也存在敏感性较低等限制。探索与T790M突变状态相关的临床因素、提高T790M突变再活检的技术水平有助于实现EGFR-TKI耐药后的精准诊断。T790M突变的NSCLC患者首选三代EGFR-TKI奥希替尼，但仍会不可避免地出现耐药。该文对继发性T790M突变的发生、相关检测技术的优劣、临床因素、治疗选择、奥希替尼的耐药机制及对策等研究情况进行综述，希望为患者临床再活检策略及后续治疗的选择提供帮助。     

Oncogenic activity of epidermal growth factor receptor kinase mutant alleles is enhanced by the T790M drug resistance mutation

Activating mutations in the epidermal growth factor receptor (EGFR) characterize a subset of non-small cell lung cancers (NSCLC) with extraordinary sensitivity to targeted tyrosine kinase inhibitors (TKI). A single secondary EGFR mutation, T790M, arising in cis with the primary activating mutation, confers acquired resistance to these drugs. However, the T790M mutation is also detected in the absence of drug selection, suggesting that it may provide a growth advantage. We show here that although T790M alone has only a modest effect on EGFR function, when combined with the characteristic activating mutations L858R or del746-750, it results in a dramatic enhancement of EGFR activity. The double mutants show potent ligand-independent receptor autophosphorylation associated with altered cellular phenotypes, soft agar colony formation, and tumorigenesis in nude mice. The significant gain-of-function properties of these double mutants may explain their initial presence before drug selection and their rapid selection as the single drug resistance mutation during therapy with gefitinib/erlotinib, and suggests that they may contribute to the adverse clinical course of TKI-resistant NSCLC.     

T790M突变的非小细胞肺癌研究现状与前景

目前,针对表皮生长因子受体(epidermal growth factor receptor,EGFR)突变的非小细胞肺癌(non-small cell lung cancer,NSCLC)公认的一线治疗方案是以EGFR酪氨酸激酶抑制剂(tyrosine kinase inhibitors,TKIs)为主的靶向治疗,尽管一代、二代TKIs带来的靶向治疗可为患者带来更长的无进展生存(progression-free survival,PFS),及更好的耐受,但其远期治疗不可避免会出现耐药.其中,50%以上的获得性耐药与T790M突变有关,因此美国国立综合癌症网络(National Comprehensive Cancer Network,NCCN)推出的最新指南已经提出三代TKI(Osimertinib,奥西替尼)可用于一线TKI治疗进展同时检出T790M突变的患者.但就在三代TKI为我们带来令人鼓舞的可长达13个月的中位PFS及延续着后EGFR-TKIs治疗时代的同时,也面临着严峻的挑战,如怎样实现T790M的检测及动态监测、对已有三代TKI的研究进展、出现三代TKI耐药的机制及后续治疗等,本文将围绕以上各热点问题展开综述.     

An alternative inhibitor overcomes resistance caused by a mutation of the epidermal growth factor receptor

Mutations of the epidermal growth factor receptor (EGFR) gene have been identified in non-small cell lung cancer specimens from patients responding to anilinoquinazoline EGFR inhibitors. However, clinical resistance to EGFR inhibitor therapy is commonly observed. Previously, we showed that such resistance can be caused by a second mutation of the EGFR gene, leading to a T790M amino acid change in the EGFR tyrosine kinase domain and also found that CL-387,785, a specific and irreversible anilinoquinazoline EGFR inhibitor, was able to overcome this resistance on the biochemical level. Here, we present the successful establishment of a stable Ba/F3 cell line model system for the study of oncogenic EGFR signaling and the functional consequences of the EGFR T790M resistance mutation. We show the ability of gefitinib to induce growth arrest and apoptosis in cells transfected with wild-type or L858R EGFR, whereas the T790M mutation leads to high-level functional resistance against gefitinib and erlotinib. In addition, CL-387,785 is able to overcome resistance caused by the T790M mutation on a functional level, correlating with effective inhibition of downstream signaling pathways. Similar data was also obtained with the use of the gefitinib-resistant H1975 lung cancer cell line. The systems established by us should prove useful for the large-scale screening of alternative EGFR inhibitor compounds against the T790M or other EGFR mutations. These data also support the notion that clinical investigations of compounds similar to CL-387,785 may be useful as a treatment strategy for patients with resistance to EGFR inhibitor therapy caused by the T790M mutation.     

Bronchial and peripheral murine lung carcinomas induced by T790M-L858R mutant EGFR respond to HKI-272 and rapamycin combination therapy

The EGFR T790M mutation has been identified in tumors from lung cancer patients that eventually develop resistance to erlotinib. In this study, we generated a mouse model with doxycycline-inducible expression of a mutant EGFR containing both L858R, an erlotinib-sensitizing mutation, and the T790M resistance mutation (EGFR TL). Expression of EGFR TL led to development of peripheral adenocarcinomas with bronchioloalveolar features in alveoli as well as papillary adenocarcinomas in bronchioles. Treatment with an irreversible EGFR tyrosine kinase inhibitor (TKI), HKI-272, shrunk only peripheral tumors but not bronchial tumors. However, the combination of HKI-272 and rapamycin resulted in significant regression of both types of lung tumors. This combination therapy may potentially benefit lung cancer patients with the EGFR T790M mutation.     

Picoliter‐Droplet Digital Polymerase Chain Reaction‐Based Analysis of Cell‐Free Plasma DNA to Assess EGFR Mutations in Lung Adenocarcinoma That Confer Resistance to Tyrosine‐Kinase Inhibitors

Purpose.

The objective of this study was to evaluate the utility of analyzing cell-free plasma DNA (cfDNA) by picoliter-droplet digital polymerase chain reaction (ddPCR) to detect EGFR mutations that confer resistance to tyrosine-kinase inhibitors (TKIs) used for treatment of lung adenocarcinoma (LADC).

Experimental design.

Thirty-five LADC patients who received epidermal growth factor receptor (EGFR)-TKI therapy, including ten who received tumor rebiopsy after development of resistance, were subjected to picoliter-ddPCR-cfDNA analysis to determine the fraction of cfDNA with TKI-sensitive (L858R and inflame exon 19 deletions) and -resistant (i.e., T790M) mutations, as well as their concordance with mutation status in rebiopsied tumor tissues.

Results.

cfDNA samples from 15 (94%) of 16 patients who acquired resistance were positive for TKI-sensitive mutations. Also, 7 (44%) were positive for the T790M mutation, with fractions of T790M (+) cfDNA ranging from 7.4% to 97%. T790M positivity in cfDNA was consistent in eight of ten patients for whom rebiopsied tumor tissues were analyzed, whereas the remaining cases were negative in cfDNA and positive in rebiopsied tumors. Prior to EGFR-TKI therapy, cfDNAs from 9 (38%) and 0 of 24 patients were positive for TKI-sensitive and T790M mutations, respectively. Next-generation sequencing of cfDNA from one patient who exhibited innate resistance to TKI despite a high fraction of TKI-sensitive mutations and the absence of the T790M mutation in his cfDNA revealed the presence of the L747P mutation, a known driver of TKI resistance.

Conclusion.

Picoliter-ddPCR examination of cfDNA, supported by next-generation sequencing analysis, enables noninvasive assessment of EGFR mutations that confer resistance to TKIs.

Implications for Practice:

Noninvasive monitoring of the predominance of tumors harboring the secondary T790M mutation in the activating mutation in EGFR gene is necessary for precise and effective treatment of lung adenocarcinoma. Because cells harboring the T790M mutation are resistant to epidermal growth factor receptor-tyrosine-kinase inhibitors (TKIs), the predominance of tumor cells harboring the T790M mutations influences the choice of whether to use conventional or next-generation TKIs. Digital polymerase chain reaction-based examination of cfDNA is a promising method; however, its feasibility, including its consistency with examination of rebiopsied tumor tissue, has not been fully proven. Here, picoliter-droplet digital polymerase chain reaction technology is presented as a candidate method for testing cfDNA and assessing the predominance of T790M-mutant tumors.     

EGFR mutation status in pleural fluid predicts tumor responsiveness and resistance to gefitinib

It has been reported that the threonine-to-methionine substitution at amino acid position 790 (T790M) of the epidermal growth factor receptor (EGFR) gene is correlated with acquired resistance to gefitinib. We previously reported that there was some population that harbored the EGFR T790M mutation as a minor clone of tumor cells prior to drug treatment, may be causing resistance to gefitinib during treatment. This fact also suggests that the detection of the EGFR T790M mutation prior to treatment may predict the development of resistance. We also showed that pleural fluid is a useful specimen for detection of EGFR mutation using sensitive assays. In this study, we reported a female patient who was treated with gefitinib because an EGFR L858R mutation was found in her pleural fluid. Our patient showed partial response to gefitinib, but she had progressive disease only 4 months after the start of treatment. Furthermore, the EGFR T790M mutation was detected in the pleural fluid before gefitinib treatment by the mutant-enriched PCR assay. Our findings confirmed that the EGFR T790M mutation was occasionally present as a minor population in tumor cells before treatment and caused resistance after gefitinib administration. The detection of a small fraction of T790M-positive alleles may be useful to predict the clinical course of the gefitinib-treated non-small-cell lung cancer patients.     

Combination Osimertinib and Gefitinib in C797S and T790M EGFR-Mutated Non–Small Cell Lung Cancer

IntroductionOsimertinib, a third-generation EGFR tyrosine kinase inhibitor has demonstrated efficacy in tumors harboring the EGFR T790M resistance mutation. Inevitably, resistance to third-generation inhibitors results in disease progression, with the EGFR C797S mutation being one of several resistance pathways identified to date. On the basis of preclinical data, we report what is the first known case of a patient harboring the T790M and C797S mutations in trans treated with combination gefitinib and osimertinib.MethodsOn development of progressive disease after multiple therapies, the patient’s plasma was sequenced using the Oncomine Lung cfDNA Assay (Thermo Fisher Scientific, Waltham, MA). Subsequent monitoring of circulating tumor DNA in plasma was performed by droplet digital polymerase chain reaction.ResultsSequencing showed that the T790M and C797S mutations were in trans. Within 2 weeks of commencement of combination therapy, rapid clinical improvement occurred. Accompanying this, a rapid decline in the C797S mutation subclone in plasma was detected. However, the levels of the EGFR exon 19 deletion driver mutation and the T790M resistance mutation in the circulating tumor DNA continued to rise and the patient died from progressive disease 6 weeks after commencement of combination therapy. There were no adverse events seen with the combination therapy.ConclusionThis is, to the best of our knowledge, the first reported case of combination EGFR tyrosine kinase inhibitor therapy tailored to the allelic conformation of T790M and C797S mutation that resulted in brief clinical improvement without toxicity.     

Detection of epidermal growth factor receptor T790M mutation in plasma DNA from patients refractory to epidermal growth factor receptor tyrosine kinase inhibitor

A secondary epidermal growth factor receptor (EGFR) mutation, the substitution of threonine 790 with methionine (T790M), leads to acquired resistance to reversible EGFR‐tyrosine kinase inhibitors (EGFR‐TKIs). A non‐invasive method for detecting T790M mutation would be desirable to direct patient treatment strategy. Plasma DNA samples were obtained after discontinuation of gefitinib or erlotinib in 75 patients with non‐small cell lung cancer (NSCLC). T790M mutation was amplified using the SABER (single allele base extension reaction) technique and analyzed using the Sequenom MassARRAY platform. We examined the T790M mutation status in plasma samples obtained after treatment with an EGFR‐TKI. The SABER assay sensitivity using mixed oligonucleotides was determined to be 0.3%. The T790M mutation was detected in 21 of the 75 plasma samples (28%). The presence of the T790M mutation was confirmed by subcloning into sequencing vectors and sequencing in 14 of the 21 samples (66.6%). In this cohort of 75 patients, the median progression‐free survival (PFS) of the patients with the T790M mutation (n = 21) was not statistically different from that of the patients without the mutation (n = 54, P = 0.94). When patients under 65 years of age who had a partial response were grouped according to their plasma T790M mutation status, the PFS of the T790M‐positive patients (n = 11) was significantly shorter than that of the T790M‐negative patients (n = 29, P = 0.03). The SABER method is a feasible means of determining the plasma T790M mutation status and could potentially be used to monitor EGFR‐TKI therapy.