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。     

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。     

奥希替尼治疗非小细胞肺癌的研究进展

表皮生长因子受体(EGFR)突变的发现以及EGFR酪氨酸激酶抑制剂(TKI)疗效的证明，标志着非小细胞肺癌(NSCLC)精准药物使用时代的到来。奥希替尼是针对EGFR TKI敏感突变和野生型EGFR T790M突变，同时保留野生型EGFR的第三代TKI。因其在临床试验中表现出的显著临床有效性和良好安全性，2015年及2016年初，美国及欧洲首次批准了奥希替尼用于接受EGFR TKI治疗后进展的EGFR T790M突变阳性的NSCLC患者的治疗，2017年3月奥西替尼正式在我国获批上市。本文主要就奥希替尼在NSCLC治疗中的研究进展进行综述。     

厄洛替尼单药治疗EGFR突变的晚期NSCLC患者试验汇合分析

背景与目的 厄洛替尼被全球多个国家批准用于晚期非小细胞肺癌(non-small cell lung cancer,NSCLC)患者的二、三线治疗.有报道显示EGFR突变的患者应用厄洛替尼治疗疗效更好.本文拟探讨厄洛替尼单药治疗EGFR突变晚期NSCLC患者的疗效.方法 计算机检索MEDLINE(2004-2009)、CBMdjc(2004-2008)、CNKI(2004-2008),互联网检索以及纳入试验的参考文献.纳入相关临床试验,提取并汇总试验结果.结果 共纳入研究7篇,包括晚期非小细胞肺癌患者463例.厄洛替尼单药治疗EGFR突变的晚期非小细胞肺癌患者,有效率达到66%,1年生存率达到73%,2年生存率达到5396,中位生存时间23个月以上,无进展生存时间8.6个月以上.结论 在当前研究的基础上,厄洛替尼单药一线和二线治疗EGFR突变的晚期NSCLC有效率高,无进展生存期和总生存期长,可以推荐作为EGFR突变的晚期NSCLC的首选治疗.尚需要更详尽的证据评价厄洛替尼单药方案或厄洛替尼与化疗联合方案与标准含铂化疗方案在治疗晚期NSCLC中的地位.     

西妥昔单抗联合厄洛替尼对人肝癌细胞的体外抑制作用

背景与目的:国内外研究报道原发性肝癌患者的肝癌组织和癌旁肝组织常有表皮生长因子受体(epidermal growth factor receptor,EGFR)的高表达,并常与肝癌侵袭、转移、放化疗抗性等生物学特性有密切关系。现已证实EGFR靶向治疗药物西妥昔单抗和厄洛替尼对肝癌细胞具有一定的体内外抑制作用,本研究探讨联合两种药物对人肝癌细胞HepG2和Bel-7402的体外作用,及两者是否具有协同性。方法:选用浓度递增的西妥昔单抗(5～500mg/mL)和厄洛替尼(2.5～250μmol/L),单独或联合作用于HepG2和Bel-7402细胞,观察不同时间对细胞增殖的抑制作用,以及联用时的两药协同系数(combinationindex,CI),并用免疫蛋白印迹法检测不同药物处理后HepG2和Bel-7402细胞EGFR信号转导通路关键酶的表达。结果:单药西妥昔单抗和厄洛替尼对HepG2和Bel-7402细胞的作用均呈时间和浓度依赖性,两药单独作用72h后,对HepG2细胞的最大抑制率分别为(43.1±1.9)%和(83.4±1.3)%,对Bel-7402细胞的最大抑制率分别为(35.1±2.6)%和(73.9±1.2)%;两药联用72h对HepG2细胞和Bel-7402细胞的最大抑制率分别为(91.1±1.0)%和(84.6±1.1)%。不同浓度的两种药物在各时间点的CI均小于1,提示二者联合作用有较好的协同性。免疫蛋白印迹检测亦显示,两药联用后HepG2和Bel-7402细胞中活化的EGFR信号转导通路关键酶的表达减弱更为明显。结论:西妥昔单抗和厄洛替尼在体外对HepG2和Bel-7402细胞的增殖都具有一定的抑制作用。联合应用时具有明显的协同效应,其作用可能与进一步下调了活化的EGFR信号转导通路关键酶的表达有关。     

肺癌中EGFR分子靶向药物及其疗效与毒性的分子预测指标

表皮生长因子受体(epidermal growth factor receptor,EGFR)信号转导通路是非小细胞肺癌(non-small cell lung cancer,NSCLC)治疗的重要靶点.通过小分子的酪氨酸抑制剂如厄洛替尼、吉非替尼或单克隆抗体如西妥昔单抗可阻止EGFR信号转导通路.     

阿美替尼二线治疗晚期非小细胞肺癌的疗效观察

目的:探究使用阿美替尼二线治疗驱动基因阳性非小细胞肺癌（non-small cell lung cancer,NSCLC）患者的疗效及安全性并分析影响患者疗效的相关因素。方法:共收集72例2020年03月至2021年03月于我院接受阿美替尼二线治疗的EGFR敏感突变IV期NSCLC患者的临床资料,最终回顾性分析了59例患者使用阿美替尼二线治疗的疗效、安全性及疗效的影响因素。结果:阿美替尼二线治疗IV期EGFR阳性突变NSCLC患者整体中位无进展生存期（mPFS）为12.0个月（95%CI:9.02个月~14.97个月）,客观缓解率（ORR）为42.4%,疾病控制率（DCR）为94.9%,其中,T790M阳性突变的患者mPFS为16.0个月（95%CI:13.2个月~18.7个月）,无突变者mPFS为8.0个月（95%CI:5.8个月~10.2个月）,差异有统计学意义（P<0.001),而患者是否有T790M突变在ORR、DCR均无显著差异（P>0.05）。基因突变类型上,EGFR 19外显子缺失突变的患者mPFS为11.5个月,21外显子L858R突变患者mPFS为10.0个月,二者差异无显著性,而这两种常见突变与罕见突变的mPFS（12.0个月 vs 5.0个月）差异则具有显著性（P=0.015）。是否肺外转移（9.0个月 vs 14.0个月,P=0.044）也是影响阿美替尼二线治疗疗效的因素,但性别、年龄、是否手术、是否吸烟、是否脑转移在mPFS上的差异无显著性。COX回归分析示T790M阴性、罕见突变、肺外转移是影响阿美替尼疗效的独立危险因素。应用阿美替尼总不良反应发生率为62.7%,三级不良反应发生率为3.4%,无严重的三四级或致死性不良反应发生。结论:阿美替尼治疗EGFR突变的NSCLC患者效果较好,T790M阳性突变、EGFR常见突变及无肺外转移患者可获得更长的PFS且用药耐受性良好。     

中国人非小细胞肺癌EGFR和K-ras基因突变与临床病理特征及厄洛替尼治疗效果的关系

目的 研究中国小细胞肺癌(NSCLC)患者表皮生长因与受体(EGFR)和K-ras基因突变情况,探讨其与NSCLC临床病理学特征及厄洛替尼治疗效果的关系.方法 利用PCR扩增和基因测序的方法检测301例中国NSCLC患者EGFR基因第18、19、20和21外显子及K-ras基因第1213密码子的突变情况,并分析其与NSCLC临床病理学特征及厄洛替尼治疗效果的关系.结果 301例患者中,99例(32.9%)有EGFR基因突变,其中第18外显子上发生突变3例,第19外显子上发生突变59例,第20外显子上发生突变2 例,第21外显子上发生突变35例.14例(4.7%)有K-ras基因突变,其中13例位于第12密码子.无同时存在EGFR和K-ras基因突变者.腺癌、无吸烟史和女性患者EGFR基因突变率较高,分别为45.7%、48.4%和49.6%.10例服用厄洛替尼有效的患者中7例携带有EGFR基因突变.结论 中国NSCLC患者EGFR基因突变率显著高于西方人群,而K-ras基因突变率则较西方人群低.联合检测EGFR和K-ras基因的突变情况可以筛选EGFR酪氨酸激酶抑制剂治疗的获益人群,并较好地预测厄洛替尼治疗晚期NSCLC的疗效.     

奥希替尼联合抗血管生成靶向药对人肺腺癌细胞抑制作用的实验研究

目的:通过体外细胞学实验初步探究奥希替尼联合两种不同机制的抗血管靶向治疗药物（贝伐珠单抗或阿帕替尼）治疗表皮生长因子受体（EGFR）敏感突变和T790M耐药突变肺腺癌细胞的抗肿瘤活性及其作用机制。方法:培养人肺腺癌细胞PC-9（E19 del）和H1975（E21 L858R/E20 T790M）,CCK-8法检测奥希替尼及抗血管靶向治疗药物（贝伐珠单抗或阿帕替尼）单药或联合处理肺腺癌细胞48 h后的抑瘤率;蛋白质印迹法检测EGFR及其下游AKT和ERK信号通路蛋白表达情况。结果:PC-9和H1975肺腺癌细胞对奥希替尼敏感且呈剂量依赖性。奥希替尼联合抗血管生成靶向药物（贝伐珠单抗,阿帕替尼）较同等浓度的单药奥希替尼可增加对PC-9和H1975细胞株的抑瘤率（P<0.05）。低浓度奥希替尼联合高浓度阿帕替尼（1 000 nmol/L）的抑制作用与高浓度奥希替尼相当（P>0.05）。随着联合的阿帕替尼浓度的升高,对PC-9和H1975细胞抑瘤率也有一定程度的提高（P<0.05）。不同处理因素对PC-9细胞的抑制率均高于对H1975细胞（P<0.01）。随着奥希替尼浓度的上升,p-EGFR、p-AKT、p-ERK磷酸化蛋白表达逐渐降低。结论:奥希替尼联合贝伐珠单抗或阿帕替尼会进一步增强对EGFR敏感突变或T790M突变肺腺癌细胞的杀伤作用。奥希替尼与阿帕替尼联合使用具有很强的抑瘤活性,具有很好的应用前景。奥希替尼单药或与抗血管形成药联合作用可能是进一步下调EGFR及其下游AKT和ERK信号通路的活化。     

晚期非小细胞肺癌患者使用EGFR-TKI治疗后长期生存的研究

目的 探索应用表皮生长因子受体酪氨酸激酶抑制剂( EGFR-TKI)治疗晚期非小细胞肺癌(NSCLC)患者长期生存的影响因素,并研究长期生存者与EGFR突变关系.方法回顾性分析2002年12月至2007年6月在北京协和医院进行EGFR-TKI治疗的292例晚期NSCLC,并收集长期生存(定义为使用吉非替尼或厄洛替尼治疗...     

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.     

Acquired Resistance to Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors in Non–Small-Cell Lung Cancers Dependent on the Epidermal Growth Factor Receptor Pathway

Most advanced Non–Small-cell lung cancers (NSCLCs) with activating epidermal growth factor receptor (EGFR) mutations (exon 19 deletions or L858R) initially respond to the EGFR tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib. However, over time (median of 6–12 months), most tumors develop acquired resistance to EGFR TKIs. Intense research in these NSCLCs has identified two major mechanisms of resistance to gefitinib/erlotinib: secondary resistance mutations and “oncogene kinase switch" systems. The secondary T790M mutation occurs in 50% of EGFR-mutated patients with TKI resistance, and in vitro, this mutation negates the hypersensitivity of activating EGFR mutations. Sensitive detection methods have identified a proportion of TKI-naive tumors that carry T790M, and these resistant clones may be selected after exposure to gefitinib or erlotinib. Other secondary resistance mutations (D761Y, L747S, T854A) seem to be rare. The amplification of the MET oncogene is present in 20% of TKI-resistant tumors; however, in half of the cases with this “oncogene kinase switch" mechanism the T790M is coexistent. It is possible that other kinases (such as insulin-like growth factor-1 receptor [IGF-1R]) might also be selected to bypass EGFR pathways in resistant tumors. The growing preclinical data in EGFR-mutated NSCLCs with acquired resistance to gefitinib or erlotinib has spawned the initiation or conception of clinical trials testing novel EGFR inhibitors that in vitro inhibit T790M (neratinib, XL647, BIBW 2992, and PF-00299804), MET, or IGF-1R inhibitors in combination with EGFR TKIs, and heat shock protein 90 inhibitors. Ongoing preclinical and clinical research in EGFR-mutated NSCLC has the potential to significantly improve the outcomes of patients with these somatic mutations.     

Molecular determinants of drug-specific sensitivity for epidermal growth factor receptor (EGFR) exon 19 and 20 mutants in non-small cell lung cancer

We hypothesized that aberrations activating epidermal growth factor receptor (EGFR) via dimerization would be more sensitive to anti-dimerization agents (e.g., cetuximab). EGFR exon 19 abnormalities (L747_A750del; deletes amino acids LREA) respond to reversible EGFR kinase inhibitors (TKIs). Exon 20 in-frame insertions and/or duplications (codons 767 to 774) and T790M mutations are clinically resistant to reversible/some irreversible TKIs. Their impact on protein function/therapeutic actionability are not fully elucidated.In our study, the index patient with non-small cell lung cancer (NSCLC) harbored EGFR D770_P772del_insKG (exon 20). A twenty patient trial (NSCLC cohort) (cetuximab-based regimen) included two participants with EGFR TKI-resistant mutations ((i) exon 20 D770>GY; and (ii) exon 19 LREA plus exon 20 T790M mutations). Structural modeling predicted that EGFR exon 20 anomalies (D770_P772del_insKG and D770>GY), but not T790M mutations, stabilize the active dimer configuration by increasing the interaction between the kinase domains, hence sensitizing to an agent preventing dimerization. Consistent with predictions, the two patients harboring D770_P772del_insKG and D770>GY, respectively, responded to an EGFR antibody (cetuximab)-based regimen; the T790M-bearing patient showed no response to cetuximab combined with erlotinib. In silico modeling merits investigation of its ability to optimize therapeutic selection based on structural/functional implications of different aberrations within the same gene.     

Novel D761Y and common secondary T790M mutations in epidermal growth factor receptor-mutant lung adenocarcinomas with acquired resistance to kinase inhibitors.

PURPOSE: In patients whose lung adenocarcinomas harbor epidermal growth factor receptor (EGFR) tyrosine kinase domain mutations, acquired resistance to the tyrosine kinase inhibitors (TKI) gefitinib (Iressa) and erlotinib (Tarceva) has been associated with a second-site EGFR mutation, which leads to substitution of methionine for threonine at position 790 (T790M). We aimed to elucidate the frequency and nature of secondary EGFR mutations in patients with acquired resistance to TKI monotherapy. EXPERIMENTAL DESIGN: Tumor cells from patients with acquired resistance were examined for secondary EGFR kinase domain mutations by molecular analyses. RESULTS: Eight of 16 patients (50% observed rate; 95% confidence interval, 25-75%) had tumor cells with second-site EGFR mutations. Seven mutations were T790M and one was a novel D761Y mutation found in a brain metastasis. When combined with a drug-sensitive L858R mutation, the D761Y mutation modestly reduced the sensitivity of mutant EGFR to TKIs in both surrogate kinase and cell viability assays. In an autopsy case, the T790M mutation was found in multiple visceral metastases but not in a brain lesion. CONCLUSIONS: The T790M mutation is common in patients with acquired resistance. The limited spectrum of TKI-resistant mutations in EGFR, which binds to erlotinib in the active conformation, contrasts with a wider range of second-site mutations seen with acquired resistance to imatinib, which binds to ABL and KIT, respectively, in closed conformations. Collectively, our data suggest that the type and nature of kinase inhibitor resistance mutations may be influenced by both anatomic site and mode of binding to the kinase target.     

Clinicopathologic and Molecular Features of Epidermal Growth Factor Receptor T790M Mutation and c-MET Amplification in Tyrosine Kinase Inhibitor-resistant Chinese Non-small Cell Lung Cancer

To investigate the clinicopathologic and molecular features of the T790M mutation and c-MET amplification in a cohort of Chinese non-small cell lung cancer (NSCLC) patients resistant to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). EGFR TKI-resistant NSCLC patients (n?=?29) and corresponding tumor specimens, and 53 samples of postoperative TKI-naïve NSCLC patients were collected. EGFR exon 19, 20, and 21 mutations were analyzed. And c-MET gene copy number was determined. The EGFR T790M mutation in exon 20 was not detected in the population of 53 TKI-naïve patients, but found in 48.3% (14/29) of the enrolled TKI-resistant patients. c-MET was amplified in 3.8% (2/53) of the TKI-naïve NSCLC patients and highly amplified in 17.2% (5/29) of the cohort. Most of T790M mutations were frequently associated with non-smoker, adenocarcinoma and EGFR activating mutations. Three male patients with T790M mutation occurred with wild-type EGFR, and were resistant to the treatments following TKI resistance. Features of c-MET amplification in TKI-naïve patients were indistinguishable from TKI-resistant patients. In the group of wild-type EGFR, patients with T790M mutation had median progression free survival (PFS) and overall survival (OS) as 9.6 months and 12.6 months, respectively; whereas the median PFS and OS of c-MET amplified patients was 4.1 months and 8.0 months, respectively. These results suggest that EGFR T790M mutation and c-MET amplification can occur in TKI-resistant NSCLC with wild-type EGFR, and these genetic defects might be related to different survival outcome. c-MET amplification in TKI-naïve or -resistant patients might share similarities in clinicopathologic features.     

Inhibiting proliferation of gefitinib-resistant, non-small cell lung cancer

Purpose

Sensitivity to a tyrosine kinase inhibitor (TKI) is correlated with the presence of somatic mutations that affect the kinase domain of epidermal growth factor receptor (EGFR). Development of resistance to TKI is a major therapeutic problem in non-small cell lung cancer (NSCLC). Aim of this study is to identify agents that can overcome TKI resistance in NSCLC.

Methods

We used a carefully selected panel of 12 NSCLC cell lines to address this clinical problem. Initially, the cell lines were treated with a variety of 10 compounds. Cellular proliferation was measured via MTT assay. We then focused on the gefitinib-resistant, EGFR mutant cell lines [H1650: exon 19 and PTEN mutations; and H1975: exons 20 (T790M) and 21 (L858R)] to identify agents that could overcome TKI resistance.

Results

Both 17-DMAG (Hsp90 inhibitor) and belinostat (histone deacetylase inhibitor, HDACi) effectively decreased the growth of almost all NSCLC lines. Also, belinostat markedly decreased the expression of EGFR and phospho-Akt in the cells. Combination of 17-DMAG and belinostat synergistically inhibited in vitro proliferation of these cells. Furthermore, both agents and their combination almost completely prevented TKI-resistant tumor formation (EGFR T790M mutation) in a xenograft model.

Conclusion

These results suggest that the combination of 17-DMAG and belinostat should be examined in a clinical trial for TKI-resistant NSCLC cell.     

Hsp90 inhibition suppresses mutant EGFR-T790M signaling and overcomes kinase inhibitor resistance

The epidermal growth factor receptor (EGFR) secondary kinase domain T790M non-small cell lung cancer (NSCLC) mutation enhances receptor catalytic activity and confers resistance to the reversible tyrosine kinase inhibitors gefitinib and erlotinib. Currently, irreversible inhibitors represent the primary approach in clinical use to circumvent resistance. We show that higher concentrations of the irreversible EGFR inhibitor CL-387,785 are required to inhibit EGFR phosphorylation in T790M-expressing cells compared with EGFR mutant NSCLC cells without T790M. Additionally, CL-387,785 does not fully suppress phosphorylation of other activated receptor tyrosine kinases (RTK) in T790M-expressing cells. These deficiencies result in residual Akt and mammalian target of rapamycin (mTOR) activities. Full suppression of EGFR-mediated signaling in T790M-expressing cells requires the combination of CL-387,785 and rapamycin. In contrast, Hsp90 inhibition overcomes these limitations in vitro and depletes cells of EGFR, other RTKs, and phospho-Akt and inhibits mTOR signaling whether or not T790M is present. EGFR-T790M-expressing cells rendered resistant to CL-387,785 by a kinase switch mechanism retain sensitivity to Hsp90 inhibition. Finally, Hsp90 inhibition causes regression in murine lung adenocarcinomas driven by mutant EGFR (L858R) with or without T790M. However, efficacy in the L858R-T790M model requires a more intense treatment schedule and responses were transient. Nonetheless, these findings suggest that Hsp90 inhibitors may be effective in T790M-expressing cells and offer an alternative therapeutic strategy for this subset of lung cancers.     

Overcoming erlotinib resistance with tailored treatment regimen in patient‐derived xenografts from naïve Asian NSCLC patients

Overall benefits of EGFR‐TKIs are limited because these treatments are largely only for adenocarcinoma (ADC) with EGFR activating mutation. The treatments also usually lead to development of resistances. We have established a panel of patient‐derived xenografts (PDXs) from treatment naïve Asian NSCLC patients, including those containing “classic” EGFR activating mutations. Some of these EGFR‐mutated PDXs do not respond to erlotinib: LU1868 containing L858R/T790M mutations, and LU0858 having L858R mutation as well as c‐MET gene amplification, both squamous cell carcinoma (SCC). Treatment of LU0858 with crizotinib, a small molecule inhibitor for ALK and c‐MET, inhibited tumor growth and c‐MET activity. Combination of erlotinib and crizotinib caused complete response, indicating the activation of both EGFR and c‐MET promote its growth/survival. LU2503 and LU1901, both with wild‐type EGFR and c‐MET gene amplification, showed complete response to crizotinib alone, suggesting that c‐MET gene amplification, not EGFR signaling, is the main oncogenic driver. Interestingly, LU1868 with the EGFR L858R/T790M, but without c‐met amplification, had a complete response to cetuximab. Our data offer novel practical approaches to overcome the two most common resistances to EGFR‐TKIs seen in the clinic using marketed target therapies.     

Challenges of detecting EGFR T790M in gefitinib/erlotinib-resistant tumours

For patients with advanced non-small cell lung cancer (NSCLC), the introduction of the epi- dermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), gefitinib and erlotinib, into clinical practice was promising. Treatment with either of these agents is associated with an objective response in 10-20% of patients. Subsequent studies have shown that patients responsive to gefitinib/erlotinib have tumours containing somatic activating mutations in the EGFR gene. Although impressive clinical and radiological responses have been observed in these patients, tumour progression occurs after the prolonged administration of gefitinib/erlotinib as acquired resistance develops. In order to combat acquired resistance, research has been largely focused on determining the factors underlying it. Two resistance mechanisms have so far been identified: a secondary mutation in the EGFR gene, T790M, and amplification of the MET proto-oncogene. This review will centre on T790M, which is thought to cause steric hindrance and impair the binding of gefitinib/erlotinib. A novel class of irreversible TKIs currently under development may retain activity against some common resistance mechanisms, including T790M. The next challenge is to identify accurately the subgroup of patients with NSCLC whose tumours harbour EGFR T790M. To this end, post-treatment tumour specimens will be needed to establish molecular profiles for each patient. In addition, novel, highly sensitive technology will be required to detect these mutations. This is because allelic dilution, whereby the EGFR gene is amplified but only a few copies of the T790M allele are needed to confer resistance, may obscure results of conventional sequencing methods. The importance of identifying patients who harbour T790M cannot be overstated; the development of irreversible TKIs will have profound implications for their treatment. In this way, treatment strategies in NSCLC are becoming increasingly tailored to the individual, and may set an example for other areas of oncology.     

Tumor growth inhibition with cetuximab and chemotherapy in non-small cell lung cancer xenografts expressing wild-type and mutated epidermal growth factor receptor.

PURPOSE: Targeting the epidermal growth factor receptor (EGFR) is a validated approach to treat cancer. In non-small cell lung cancer (NSCLC), EGFR contains somatic mutations in 10% of patients, which correlates with increased response rates to small molecule inhibitors of EGFR. We analyzed the effects of the monoclonal IgG1 antibody Erbitux (cetuximab) in NSCLC xenografts with wild-type (wt) or mutated EGFR. EXPERIMENTAL DESIGN: NSCLC cell lines were grown s.c. in nude mice. Dose-dependent efficacy was established for cetuximab. To determine whether combination therapy produces tumor regressions, cetuximab was dosed at half-maximal efficacy with chemotherapy used at maximum tolerated dose. RESULTS: Cetuximab showed antitumor activity in wt (A549, NCI-H358, NCI-H292) and mutated [HCC-827 (delE746-A750), NCI-H1975 (L858R, T790M)] EGFR-expressing xenografts. In the H292 model, cetuximab and docetaxel combination therapy was more potent to inhibit tumor growth than cetuximab or docetaxel alone. Cisplatin augmented efficacy of cetuximab to produce 6 of 10 regressions, whereas 1 of 10 regressions was found with cetuximab and no regression was found with cisplatin. Using H1975 xenografts, gemcitabine increased efficacy of cetuximab resulting in 12 of 12 regressions. Docetaxel with cetuximab was more efficacious with seven of nine regressions compared with single treatments. Cetuximab inhibited autophosphorylation of EGFR in both H292 and H1975 tumor lysates. Exploring the underlying mechanism for combination effects in the H1975 xenograft model, docetaxel in combination with cetuximab added to the antiproliferative effects of cetuximab but was the main component in this drug combination to induce apoptosis. CONCLUSIONS: Cetuximab showed antitumor activity in NSCLC models expressing wt and mutated EGFR. Combination treatments increased the efficacy of cetuximab, which may be important for the management of patients with chemorefractory NSCLC.