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.     

Poor response to erlotinib in patients with tumors containing baseline EGFR T790M mutations found by routine clinical molecular testing

BackgroundEGFR T790M is the most common mutation associated with acquired resistance to EGFR tyrosine kinase inhibitors (TKIs). Baseline EGFR T790M mutations in EGFR TKI-naïve patients have been reported, but the frequency and their association with response to EGFR TKIs remain unclear.Patients and methodsThe frequency of baseline EGFR T790M as detected by routine molecular genotyping was determined by reviewing clinical results obtained at our institution from 2009 to 2013. We also collected outcome data for treatment with EGFR TKIs.ResultsTo define the incidence of EGFR T790M, we reviewed 2774 sequentially tested patients with lung cancer who underwent molecular testing using a mass spectrometry-based assay, and 11 (0.5%) had baseline EGFR T790M. Compiling results from several molecular techniques, we observed EGFR T790M in tumors from 20 patients who had not previously been treated with an EGFR TKI. In all cases, EGFR T790M occurred concurrently with another EGFR mutation, L858R (80%, 16/20), or exon 19 deletion (20%, 4/20). Two percent of all pre-treatment EGFR-mutant lung cancers harbored an EGFR T790M mutation. Thirteen patients received erlotinib monotherapy as treatment for metastatic disease. The response rate was 8% (1/13, 95% confidence interval 0%–35%). For the patients who received erlotinib, the median progression-free survival was 2 months and the median overall survival was 16 months.ConclusionsDe novo EGFR T790M mutations are rare (<1%) when identified by standard sensitivity methods. TKI therapy for patients with baseline EGFR T790M detected by standard molecular analysis has limited benefit.     

Efficacy of immunotherapy targeting the neoantigen derived from epidermal growth factor receptor T790M/C797S mutation in non–small cell lung cancer

Lung cancer is the leading cause of cancer‐related deaths worldwide. Epidermal growth factor receptor‐tyrosine kinase inhibitors (EGFR‐TKI) often have good clinical activity against non–small cell lung cancer (NSCLC) with activating EGFR mutations. Osimertinib, which is a third‐generation EGFR‐TKI, has a clinical effect even on NSCLC harboring the threonine to methionine change at codon 790 of EGFR (EGFR T790M) mutation that causes TKI resistance. However, most NSCLC patients develop acquired resistance to osimertinib within approximately 1 year, and 40% of these patients have the EGFR T790M and cysteine to serine change at codon 797 (C797S) mutations. Therefore, there is an urgent need for the development of novel treatment strategies for NSCLC patients with the EGFR T790M/C797S mutation. In this study, we identified the EGFR T790M/C797S mutation‐derived peptide (790‐799) (MQLMPFGSLL) that binds the human leukocyte antigen (HLA)‐A*02:01, and successfully established EGFR T790M/C797S‐peptide‐specific CTL clones from human PBMC of HLA‐A2 healthy donors. One established CTL clone demonstrated adequate cytotoxicity against T2 cells pulsed with the EGFR T790M/C797S peptide. This CTL clone also had high reactivity against cancer cells that expressed an endogenous EGFR T790M/C797S peptide using an interferon‐γ (IFN‐γ) enzyme‐linked immunospot (ELISPOT) assay. In addition, we demonstrated using a mouse model that EGFR T790M/C797S peptide‐specific CTL were induced by EGFR T790M/C797S peptide vaccine in vivo. These findings suggest that an immunotherapy targeting a neoantigen derived from EGFR T790M/C797S mutation could be a useful novel therapeutic strategy for NSCLC patients with EGFR‐TKI resistance, especially those resistant to osimertinib.     

The safety and efficacy of osimertinib for the treatment of EGFR T790M mutation positive non-small-cell lung cancer

First- and second-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are the evidence-based first-line treatment for metastatic non-small-cell lung cancers (NSCLCs) that harbor sensitizing EGFR mutations (i.e. exon 19 deletions or L858R). However, acquired resistance to EGFR TKI monotherapy occurs invariably within a median time frame of one year. The most common form of biological resistance is through the selection of tumor clones harboring the EGFR T790M mutation, present in >50% of repeat biopsies. The presence of the EGFR T790M mutation negates the inhibitory activity of gefitinib, erlotinib, and afatinib. A novel class of third-generation EGFR TKIs has been identified by probing a series of covalent pyrimidine EGFR inhibitors that bind to amino-acid residue C797 of EGFR and preferentially inhibit mutant forms of EGFR versus the wild-type receptor. We review the rapid clinical development and approval of the third-generation EGFR TKI osimertinib for treatment of NSCLCs with EGFR-T790M.     

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.     

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.     

Analysis of epidermal growth factor receptor gene mutation in patients with non-small cell lung cancer and acquired resistance to gefitinib.

PURPOSE: Non-small cell lung cancers carrying activating mutations in the gene for the epidermal growth factor receptor (EGFR) are highly sensitive to EGFR-specific tyrosine kinase inhibitors. However, most patients who initially respond subsequently experience disease progression while still on treatment. Part of this "acquired resistance" is attributable to a secondary mutation resulting in threonine to methionine at codon 790 (T790M) of EGFR. EXPERIMENTAL DESIGN: We sequenced exons 18 to 21 of the EGFR gene to look for secondary mutations in tumors with acquired resistance to gefitinib in 14 patients with adenocarcinomas. Subcloning or cycleave PCR was used in addition to normal sequencing to increase the sensitivity of the assay. We also looked for T790M in pretreatment samples from 52 patients who were treated with gefitinib. We also looked for secondary KRAS gene mutations because tumors with KRAS mutations are generally resistant to tyrosine kinase inhibitors. RESULTS: Seven of 14 tumors had a secondary T790M mutation. There were no other novel secondary mutations. We detected no T790M mutations in pretreatment specimens from available five tumors among these seven tumors. Patients with T790M tended to be women, never smokers, and carrying deletion mutations, but the T790M was not associated with the duration of gefitinib administration. None of the tumors had an acquired mutation in the KRAS gene. CONCLUSIONS: A secondary T790M mutation of EGFR accounted for half the tumors with acquired resistance to gefitinib in Japanese patients. Other drug-resistant secondary mutations are uncommon in the EGFR gene.     

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.     

Monitoring EGFR T790M with plasma DNA from lung cancer patients in a prospective observational study

Use of plasma DNA to detect mutations has spread widely as a form of liquid biopsy. EGFR T790M has been observed in half of lung cancer patients who have acquired resistance to EGFR tyrosine kinase inhibitors (EGFR‐TKI). Effectiveness of monitoring T790M via plasma DNA during treatment with EGFR‐TKI has not been established as an alternative to re‐biopsy. This was a prospective multicenter observational study involving non‐small cell lung cancer patients carrying EGFR L858R or exon 19 deletions, treated with EGFR‐TKI. The primary objective was to determine whether T790M could be detected using plasma DNA in patients with progressive disease (PD). T790M was examined using the mutation‐biased PCR and quenching probe (MBP‐QP) method, a sensitive, fully‐automated system developed in our laboratory. Eighty‐nine non‐small cell lung cancer patients were enrolled from seven hospitals in Japan. Sequential examinations revealed T790M in plasma DNA among 40% of patients who developed PD. Activating mutations, such as L858R and exon 19 deletions, were detected in 40% of patients using plasma DNA, and either T790M or activating mutations were observed in 62%. Dividing into four periods (before PD, at PD, at discontinuation of EGFR‐TKI and subsequently), T790M was detected in 10, 19, 24 and 27% of patients, respectively. Smokers, males, patients having exon 19 deletions and patients who developed new lesions evidenced significantly frequent presence of T790M in plasma DNA. Monitoring T790M with plasma DNA using MBP‐QP reflects the clinical course of lung cancer patients treated with EGFR‐TKI. Detection of T790M with plasma DNA was correlated with EGFR mutation type, exon 19 deletions and tumor progression. Re‐biopsy could be performed only in 14% of PD cases, suggesting difficulty in obtaining re‐biopsy specimens in practice. Monitoring T790M with plasma DNA reflects the clinical course, and is potentially useful in designing strategies for subsequent treatment.     

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.     

Double mutation and gene copy number of EGFR in gefitinib refractory non-small-cell lung cancer

Mutations of the epidermal growth factor receptor (EGFR) gene have been reported in non-small-cell lung cancer (NSCLC), especially in patients with adenocarcinoma and never smokers. Some common somatic mutations in EGFR, including deletion mutations in exon 19 and leucine-to-arginine substitution at amino acid position 858 (L858R) in exon 21, have been examined for their ability to predict sensitivity to gefitinib or erlotinib, which are selective EGFR tyrosine kinase inhibitors (EGFR-TKIs). On the other hand, reports have shown that the threonine-to-methionine substitution at amino acid position 790 (T790M) in exon 20 is related to gefitinib resistance. Some studies have indicated that high copy numbers of the EGFR gene may be a more effective molecular predictor to responsiveness and prolonged survival in patients treated with EGFR-TKIs. Here, we describe two NSCLC patients with the L858R mutation who did not respond to gefitinib. Case 1 harbored both the T790M and L858R mutations, and fluorescence in situ hybridization showed EGFR gene amplification. Case 2 harbored both the L858R and aspartic acid-to-tyrosine substitution at amino acid position 761 in exon 19 of EGFR mutations and had a high polysomy status for EGFR. In these two cases, tumors showed resistance to gefitinib treatment despite the presence of EGFR L858R mutation and increased copy number. Our findings encourage further molecular analysis to elucidate the relationship between the EGFR status, including mutations and amplifications, and the responsiveness of NSCLC to gefitinib.     

Indication of EGFR kinase inhibitors should be refined

Even though lung cancer incidence began to decline in the majority of industrialized countries, is still belong to cancers with one of the highest incidence and mortality rates. In the Czech Republic, epidermal growth factor receptor (EGFR) kinase activity inhibitors erlotinib and gefitinib are approved for the use as the second- and third-line treatment of non-small-cell lung cancer. In a cohort of non-small-cell lung cancer patients, erlotinib administration led to tumour regression in less than 20% of patients. However, when used in patients with EGFR-activating mutations, e.g. L858R or delE746-A750, the response rate increased to 75-82% in several parallel clinical studies. Similarly, improved response rate was reported in patients bearing amplified wild-type EGFR gene. In contrary, patients with T790M, D761Y, L747S, and T854A mutations (and some other rare abberations) were found to be resistant to treatment with small-molecule inhibitors targeting the active site of the kinase domain. These mutations do not change the EGFR affinity to gefitinib or erlotinib but the mutated receptor is able to bind ATP into its active site even in the presence of erlotinib or gefitinib, similar to a wild-type receptor without an inhibitor. Besides that, when the EGFR molecule bears both the activating (e.g. L858R) and resistance-inducing mutation (e.g. T790M), the tumour acquires resistance to both erlotinib and gefitinib treatment. Currently, research focuses on a development of new strategies that would allow treatment of patients bearing mutations inducing resistance to the small-molecule inhibitors targeted on the active site of EGFR kinase domain. Contrary to the current guidelines for Czech oncologists, identification of EGFR with any of the above mentioned resistance-inducing somatic mutations should be considered as an explicit contraindication for non-small-cell cancer treatment using small-molecule EGFR kinase activity inhibitors erlotinib or gefitinib. This should also include patients in whom a resistance-inducing mutation is detected together with any of the activating mutations or deletions.     

Antitumor activity of HM781-36B, a highly effective pan-HER inhibitor in erlotinib-resistant NSCLC and other EGFR-dependent cancer models

The epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases has been implicated in a variety of cancers. In particular, activating mutations such as the L858R point mutation in exon 21 and the small in-frame deletions in exon 19 of the EGFR tyrosine kinase domain are correlated with sensitivity to EGFR tyrosine kinase inhibitors in non-small cell lung cancer (NSCLC) patients. Clinical treatment of patients is limited by the development of drug resistance resulting mainly from a gatekeeper mutation (T790M). In this study, we evaluated the therapeutic potential of a novel, irreversible pan-HER inhibitor, HM781-36B. The results from this study show that HM781-36B is a potent inhibitor of EGFR in vitro, including the EGFR-acquired resistance mutation (T790M), as well as HER-2 and HER-4, compared with other EGFR tyrosine kinases inhibitors (erlotinib, lapatinib and BIBW2992). HM781-36B treatment of EGFR DelE746_A750-harboring erlotinib-sensitive HCC827 and EGFR L858R/T790M-harboring erlotinib-resistant NCI-H1975 NSCLC cells results in the inhibition of EGFR phosphorylation and the subsequent deactivation of downstream signaling proteins. Additionally, HM781-36B shows an excellent efficacy in a variety of EGFR- and HER-2-dependent tumor xenograft models, including erlotinib-sensitive HCC827 NSCLC cells, erlotinib-resistant NCI-H1975 NSCLC cells, HER-2 overexpressing Calu-3 NSCLC cells, NCI-N87 gastric cancer cells, SK-Ov3 ovarian cancer cells and EGFR-overexpressing A431 epidermoid carcinoma cancer cells. On the basis of these preclinical results, HM781-36B is the most potent pan-HER inhibitor, which will be advantageous for the treatment of patients with NSCLC including clinical limitation caused by acquired mutation (EGFR T790M), breast cancer and gastric cancer.     

Clinical outcomes and secondary epidermal growth factor receptor (EGFR) T790M mutation among first-line gefitinib,erlotinib and afatinib-treated non-small cell lung cancer patients with activating EGFR mutations

Gefitinib, erlotinib and afatinib are approved for first-line treatment of advanced non-small cell lung cancer (NSCLC) bearing an activating epidermal growth factor receptor (EGFR) mutation. However, the clinical outcomes among the three EGFR tyrosine kinase inhibitors (TKIs) are still controversial. We aimed to evaluate clinical outcomes and secondary EGFR T790M mutation among the three EGFR TKIs. From May 2014 to January 2016, a total of 301 patients received treatment with gefitinib, erlotinib or afatinib, for first-line treatment of advanced NSCLC with an activating EGFR mutation, based on their clinicians’ choice. The median overall survival (OS) was 37.0 months. Although the baseline characteristics of patients were unequal, progression-free survival and OS did not differ among the 3 groups. Multivariate analysis found that gefitinib (adjusted odds ratio [aOR] 3.29, 95% confidence interval [CI], 1.15–9.46, p = 0.027), EGFR TKI treatment duration more than 13 months (aOR 3.16, 95% CI, 1.20–8.33, p = 0.020), male (aOR 3.25, 95% CI, 1.10–9.66, p = 0.034), initial liver metastasis (aOR 4.97, 95% CI 1.18–20.96, p = 0.029) and uncommon EGFR mutation (aOR 0.14, 95% CI, 0.02–0.97, compared to EGFR deletion 19, p = 0.047) were independent factors for secondary T790M mutation. In real-world practice, choosing first line EGFR TKI based on the patients’ clinical characteristics yielded good clinical outcomes. First-line gefitinib, longer EGFR TKI treatment duration, male, initial liver metastasis and uncommon EGFR mutations may be independent factors for secondary EGFR T790M mutation.     

Non-small-cell lung cancer harbouring mutations in the EGFR kinase domain

Key “driver” mutations have been discovered in specific subgroups of non-small-cell lung cancer (NSCLC) patients. Activating mutations in the form of deletions in exon 19 (del 19) or the missense mutation L858R in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) predict outcome to EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib. Pooled data from several phase II studies show that gefitinib and erlotinib induce responses in over 70% of NSCLC patients harbouring EGFR mutations, with progression-free survival (PFS) ranging from 9 to 13 months and median survival of around 23 months. Two studies in Caucasian and Asian patients have confirmed that these subgroups of patients attain response rates of 70% with erlotinib and gefitinib, including complete responses, PFS up to 14 months and median survival up to 27 months. These landmark outcomes have been accompanied by new challenges: the additional role of chemotherapy and the management of tumours with the secondary T790M mutation that confers resistance to EGFR TKIs. Mechanisms of resistance to reversible EGFR TKIs should be further clarified and could be related to modifications in DNA repair. The presence of double mutations (T790M plus either L858R or del 19) at the time of diagnosis could be much more frequent than originally thought. The sensitivity to EGFR TKIs could be greatly influenced by the expression of genes involved in the repair of DNA double-strand breaks by homologous recombination and non-homologous end joining.     

EGFR-T790M is a rare lung cancer susceptibility allele with enhanced kinase activity

The use of tyrosine kinase inhibitors (TKI) has yielded great success in treatment of lung adenocarcinomas. However, patients who develop resistance to TKI treatment often acquire a somatic resistance mutation (T790M) located in the catalytic cleft of the epidermal growth factor receptor (EGFR) enzyme. Recently, a report describing EGFR-T790M as a germ-line mutation suggested that this mutation may be associated with inherited susceptibility to lung cancer. Contrary to previous reports, our analysis indicates that the T790M mutation confers increased Y992 and Y1068 phosphorylation levels. In a human bronchial epithelial cell line, overexpression of EGFR-T790M displayed a growth advantage over wild-type (WT) EGFR. We also screened 237 lung cancer family probands, in addition to 45 bronchoalveolar tumors, and found that none of them contained the EGFR-T790M mutation. Our observations show that EGFR-T790M provides a proliferative advantage with respect to WT EGFR and suggest that the enhanced kinase activity of this mutant is the basis for rare cases of inherited susceptibility to lung cancer.     

厄洛替尼与西妥昔单抗联合应用治疗吉非替尼耐药NSCLC的疗效

本研究通过EGFR-TKI和EGFR单克隆抗体联合应用探讨治疗EGFR突变阴性和EGFR T790M突变继发性耐药的NSCLC的疗效。方法:应用EGFR突变阴性和EGFR T790M突变继发性耐药的NSCLL细胞原代培养及药敏技术检验EGFR-TKI和EGFR单克隆抗体联合应用的疗效。结果:检测厄洛替尼和西妥昔单抗联合处理对于15例EGFR突变阴性和8例T790M突变阳性的继发性耐药的NSCLC患者原代细胞的影响,应用浓度分别为50 μg/mL西妥昔单抗和1 μM厄洛替尼作用于EGFR突变阴性的NSCLC患者原代细胞,结果显示这三组间T/C值无显著性差异（P>0.05）,对于T790M突变阳性的继发性耐药的NSCLC原代细胞这三组间T/C值有显著性差异（P<0.05）,联合用药组疗效明显高于单药组。结论:进一步验证了厄洛替尼和西妥昔单抗联合应用对于EGFR突变阴性的NSCLC患者无效,但对于T790M突变阳性的继发性耐药的NSCLC患者有效。      

Combined EGFR/MET or EGFR/HSP90 inhibition is effective in the treatment of lung cancers codriven by mutant EGFR containing T790M and MET

Tyrosine kinase inhibitors (TKI) that target the EGF receptor (EGFR) are effective in most non-small cell lung carcinoma (NSCLC) patients whose tumors harbor activating EGFR kinase domain mutations. Unfortunately, acquired resistance eventually emerges in these chronically treated cancers. Two of the most common mechanisms of acquired resistance to TKIs seen clinically are the acquisition of a secondary "gatekeeper" T790M EGFR mutation that increases the affinity of mutant EGFR for ATP and activation of MET to offset the loss of EGFR signaling. Although up to one-third of patient tumors resistant to reversible EGFR TKIs harbor concurrent T790M mutation and MET amplification, potential therapies for these tumors have not been modeled in vivo. In this study, we developed a preclinical platform to evaluate potential therapies by generating transgenic mouse lung cancer models expressing EGFR-mutant Del19-T790M or L858R-T790M, each with concurrent MET overexpression. We found that monotherapy targeting EGFR or MET alone did not produce significant tumor regression. In contrast, combination therapies targeting EGFR and MET simultaneously were highly efficacious against EGFR TKI-resistant tumors codriven by Del19-T790M or L858R-T790M and MET. Our findings therefore provide an in vivo model of intrinsic resistance to reversible TKIs and offer preclinical proof-of-principle that combination targeting of EGFR and MET may benefit patients with NSCLC.     

Audit of Molecular Mechanisms of Primary and Secondary Resistance to Various Generations of Tyrosine Kinase Inhibitors in Known Epidermal Growth Factor Receptor-Mutant Non-small Cell Lung Cancer Patients in a Tertiary Centre

AimsPresently, three generations of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are approved against oncogene addicted EGFR-mutant non-small cell lung cancer (NSCLC). Patients with actionable EGFR mutations invariably develop resistance. This resistance can be intrinsic (primary) or acquired (secondary).Materials and methodsThis was a retrospective study carried out between January 2016 and April 2021 analysing 486 samples of NSCLC for primary and secondary resistance to first- (erlotinib, gefitinb), second- (afatinib) and/or third-generation (osimertinib) TKIs in EGFR-mutant NSCLCs by next generation sequencing (NGS). Tissue NGS was carried out using the Thermofischer Ion Torrent? Oncomine? Focus 52 gene assay; liquid biopsy NGS was carried out using the Oncomine Lung Cell-Free Total Nucleic Acid assay. All cases were previously tested for a single EGFR gene with the Therascreen® EGFR RGQ PCR kit.ResultsThe results were divided into four groups: (i) group 1: primary resistance to first- and/or second-generation TKIs. This group, with 21 cases, showed EGFR exon 20 insertions, dual, complex mutations and variant of unknown significance, de novo MET gene amplification besides other mutations. (ii) Group 2: primary resistance to third-generation TKIs. This group showed two cases, with one showing dual EGFR mutation (L858R and E709A) and EGFR gene amplification. (iii) Group 3: secondary resistance to first- and second-generation TKIs. This group had 27 cases, which were previously reported negative for EGFR T790M by single gene testing. Significant findings were MET gene amplification in four cases, with one also showing MET exon 14 skipping mutation. Three cases showed small cell change and one showed loss of primary mutation. (iv) Group 4: secondary resistance to third-generation TKIs. The latter group was further subgrouped into group 4A: secondary resistance to osimertinib (third-generation TKI) when offered as second-line therapy after first- and second-generation TKIs on detection of T790M mutation. This group had 15 cases. EGFR T790M mutation was lost in 10 (10/15; 67%) cases and was retained in five cases. Patients with T790M loss experienced early resistance (6.9 months versus 12.6 months mean, P = 0.0024) compared with cases that retained T790M. Two cases gained MET amplification as the resistance mechanisms. Other mutations that were found when EGFR T790M was lost were in FGFR3, KRAS, PIK3CA, CTNNB1, BRAF genes. One case had EML4-ALK translocation. Two cases showed driver EGFR deletion 19, retained T790M and C797S mutation in Cis form. Group 4B: secondary resistance to osimertinib (when given as first-line therapy) in EGFR-mutant NSCLC. This group had three cases. The duration of osimertinib treatment ranged from 11 to 17 months. Two patients showed additional C797S mutation along with primary EGFR mutation.ConclusionThis study shows the wide spectrum of primary and secondary EGFR resistance mechanisms to first, second and third generation of TKIs and helps us to identify newer therapeutic targets that could carry forward the initial advantage offered by EGFR TKIs.     

肺癌EGFR-TKI继发耐药的主要机制与应对策略

表皮生长因子受体-酪氨酸激酶抑制剂(EGFR-TKI)是含有EGFR敏感突变的肺腺癌患者重要的靶向治疗药物,但几乎所有治疗有效的患者最终都会对EGFR-TKI治疗产生继发耐药.目前较公认的耐药机制主要包括T790M突变、MET扩增、PIK3CA突变、人第10号染色体缺失的磷酸酶及张力蛋白同源的基因表达下调、Fas-核转录因子-κB激活等.近年针对以上耐药机制,诞生了一批克服EGFR-TKI继发耐药的新药物,这些药物大部分仍停留在细胞或动物实验阶段,但也有少数药物获得了比较肯定的临床结果.