The epidermal growth factor receptor D761Y mutation and effect of tyrosine kinase inhibitor

De Novo mutation in Epidermal growth factor receptor (EGFR)-D761Y responding to third generation tyrosine kinase inhibitor Osimertinib: A case report

INTRODUCTION

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer. Epidermal growth factor receptor (EGFR) mutations are the most common accurate gene targets. However, the lack of case reports or cohort studies on the exceptionally rare mutations limit the acquisition of deeper insights.

PATIENT CONCERNS

A 76-year-old female nonsmoker presented to our hospital with a one-week disease history of cough accompanied by shortness of breath.

DIAGNOSIS

Contrast-enhanced CT scan showed right pleural effusion with scattered inflammation and consolidation in the right upper lung. Tumor marker display showed obvious increased. Histopathology of the pulmonary mass combined with Immunohistochemical staining indicated lung adenocarcinoma. Contrast-enhanced magnetic resonance imaging suggested brain metastases. ECT scan showed bone metastasis. The patient was thus diagnosed as right lung adenocarcinoma of stage IV (cT3N3M1c). Next generation sequencing was performed to profile the mutation status of known oncogenic driver mutations, and only EGFR-D761Y in exon 19 (allelic frequency, AF: 0.53%) mutation was found.

INTERVENTIONS

The patient was accordingly treated with the third generation EGFR-Epidermal growth factor receptor tyrosine kinase inhibitor (TKI) Osimertinib (80 mg, qd). Accompanied with whole brain radiotherapy (DT3000c Gy/10f) for brain metastases, technetium methylene diphosphonate injection was performed for bone metastases.

OUTCOMES

The efficacy of the first-line Osimertinib treatment for 1 month was assessed as PR per RECIST version 1.1. The NSCLC patient harboring EGFR-D761Y mutation detected prior to the EGFR L858R mutation was benefited from the third-generation EGFR-TKI Osimertinib and had a worse prognosis than with other EGFR mutations according to data from previous case reports.

CONCLUSIONS

This case reported a NSCLC patient with de novo mutation of EGFR-D761Y responding to third generation TKI Osimertinib.

Epidermal Growth Factor Receptor Expression and Resistance Patterns to Targeted Therapy in Non-Small Cell Lung Cancer: A Review

Globally, lung cancer is the leading cause of cancer-related death. The majority of non-small cell lung cancer (NSCLC) tumours express epidermal growth factor receptor (EGFR), which allows for precise and targeted therapy in these patients. The dysregulation of EGFR in solid epithelial cancers has two distinct mechanisms: either a kinase-activating mutation in EGFR (EGFR-mutant) and/or an overexpression of wild-type EGFR (wt-EGFR). The underlying mechanism of EGFR dysregulation influences the efficacy of anti-EGFR therapy as well as the nature of resistance patterns and secondary mutations. This review will critically analyse the mechanisms of EGFR expression in NSCLC, its relevance to currently approved targeted treatment options, and the complex nature of secondary mutations and intrinsic and acquired resistance patterns in NSCLC.

Durable Response to Osimertinib in a Chinese Patient with Metastatic Lung Adenocarcinoma Harboring a Rare EGFR L858R/D761Y Compound Mutation

Uncommon mutations account for 10-15% of epidermal growth factor receptor (EGFR) mutations in patients with non-small-cell lung cancer (NSCLC). However, in spite of the wealth of knowledge of the clinical significance and tyrosine kinase inhibitor (TKI) sensitivity of these mutations, acquisition of deeper insights is limited by the paucity of case reports and cohort studies of the exceptionally rare mutations, including compound mutations. In the present case, we describe the clinical efficacy of icotinib and osimertinib in a metastatic lung adenocarcinoma patient carrying a highly uncommon EGFR L858R/D761Y compound mutation. The progression-free survival (PFS) with osimertinib treatment was much longer than that with icotinib (19 mo vs 8.2 mo), and the overall survival (OS) has currently exceeded three years. To the best of our knowledge, this is the first report of durable osimertinib response in an NSCLC patient with a rare EGFR L858R/D761Y mutation.

Mechanisms of acquired resistance to first- and second-generation EGFR tyrosine kinase inhibitors

Patients with non-small-cell lung cancer (NSCLC) whose tumours harbour activating mutations within the epidermal growth factor receptor (EGFR) frequently derive significant clinical and radiographic benefits from treatment with EGFR tyrosine kinase inhibitors (TKIs). As such, prospective identification of EGFR mutations is now the standard of care worldwide. However, acquired therapeutic resistance to these agents invariably develops. Over the past 10 years, great strides have been made in defining the molecular mechanisms of EGFR TKI resistance in an effort to design rational strategies to overcome this acquired drug resistance. Approximately 60% of patients with acquired resistance to the EGFR TKIs (erlotinib, gefitinib, and afatinib) develop a new mutation within the drug target. This mutation-T790M-has been shown to alter drug binding and enzymatic activity of the mutant EGF receptor. Less common mechanisms of acquired resistance include MET amplification, ERBB2 amplification, transformation to small-cell lung cancer, and others. Here, we present a condensed overview of the literature on EGFR-mutant NSCLC, paying particular attention to mechanisms of drug resistance, recent clinical trial results, and novel strategies for identifying and confronting drug resistance, while also striving to identify gaps in current knowledge. These advances are rapidly altering the treatment landscape for EGFR-mutant NSCLC, expanding the armamentarium of available therapies to maximize patient benefit.

The mechanism of acquired resistance to irreversible EGFR tyrosine kinase inhibitor-afatinib in lung adenocarcinoma patients

Introduction

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are associated with favorable response in EGFR mutant lung cancer. Acquired resistance to reversible EGFR TKIs remains a significant barrier, and acquired EGFR T790M-mutation is the major mechanism. Second-generation irreversible EGFR TKI, afatinib, had also been approved for treating EGFR mutant lung cancer patients, but the mechanism of acquired resistance to afatinib has not been well studied.

Results

Forty-two patients had tissue specimens taken after acquiring resistance to afatinib. The sensitizing EGFR mutation were all consistent between pre- and post-afatinib tissues. Twenty patients (47.6%) had acquired T790M mutation. T790M rate was not different between first-generation EGFR TKI-naïve patients (50%) and first-generation EGFR TKI-treated patients (46.4%) (p = 0.827). No clinical characteristics or EGFR mutation types were associated with the development of acquired T790M. No other second-site EGFR mutations were detected. There were no small cell or squamous cell lung cancer transformation. Other genetic mutations were not identified in PIK3CA, BRAF, HER2, KRAS, NRAS, MEK1, AKT2, LKB1 and JAK2.

Methods

Afatinib-prescription record of our department of pharmacy from January 2007 and December 2014 was retrieved. We investigated patients with tissue specimens available after acquiring resistance to afatinib. Enrolled patients should have partial response or durable stable disease of treatment response to afatinib. Various mechanisms of acquired resistance to first-generation EGFR TKIs were evaluated. Histology and cytology were reviewed. EGFR, PIK3CA, BRAF, HER2, KRAS, NRAS, MEK1, AKT2, LKB1 and JAK2 genetic alterations were evaluated by sequencing. Statistical analysis was performed using Chi-square test and Kaplan-Meier method.

Conclusions

T790M was detected in half of the lung adenocarcinoma after acquiring resistance to afatinib. T790M is still the major acquired resistance mechanism. First-generation EGFR TKI exposure did not influence the prevalence of T790M in lung cancer acquired resistance to afatinib.

Histological evolution from primary lung adenocarcinoma harboring EGFR mutation to high-grade neuroendocrine carcinoma

Background

Although patients with EGFR mutated lung adenocarcinoma benefit greatly from tyrosine kinase inhibitors (TKIs), they inevitably develop acquired resistance after an average of 10–14 months of continuous treatment.

Methods

We retrospectively analyzed the clinical and histopathological data of eight patients with primary lung adenocarcinoma harboring EGFR mutations that transformed into high‐grade neuroendocrine carcinoma after TKI therapy. Morphology scanning for neuroendocrine differentiation and immunohistochemistry for neuroendocrine markers CD56, chromogranin, and synaptophysin were performed on primary adenocarcinoma tissues and repeated biopsies. Mutations of EGFR exons 19–21 were reexamined using the amplification refractory mutation system.

Results

The carcinoma in seven patients transformed to small cell lung carcinoma; two of these patients enrolled in theAZD9291 study after acquiring a T790M missense mutation. The carcinoma in one patient transformed to large cell neuroendocrine carcinoma. None of the eight primary tumors exhibited neuroendocrine morphologic features and only one surgical specimen displayed a weak stain for neuroendocrine marker synaptophysin. Drug resistant high‐grade neuroendocrine carcinomas retained their initial activating EGFR mutations.

Conclusions

Lung adenocarcinoma in eight patients transformed into high‐grade neuroendocrine carcinoma and retained the original activating EGFR mutations after targeted therapy by TKIs. Furthermore, the prognosis of the transformed carcinoma was worse than the original primary genetic and morphologic type.

Bayesian model of signal rewiring reveals mechanisms of gene dysregulation in acquired drug resistance in breast cancer

Small molecule inhibitors, such as lapatinib, are effective against breast cancer in clinical trials, but tumor cells ultimately acquire resistance to the drug. Maintaining sensitization to drug action is essential for durable growth inhibition. Recently, adaptive reprogramming of signaling circuitry has been identified as a major cause of acquired resistance. We developed a computational framework using a Bayesian statistical approach to model signal rewiring in acquired resistance. We used the p₁-model to infer potential aberrant gene-pairs with differential posterior probabilities of appearing in resistant-vs-parental networks. Results were obtained using matched gene expression profiles under resistant and parental conditions. Using two lapatinib-treated ErbB2-positive breast cancer cell-lines: SKBR3 and BT474, our method identified similar dysregulated signaling pathways including EGFR-related pathways as well as other receptor-related pathways, many of which were reported previously as compensatory pathways of EGFR-inhibition via signaling cross-talk. A manual literature survey provided strong evidence that aberrant signaling activities in dysregulated pathways are closely related to acquired resistance in EGFR tyrosine kinase inhibitors. Our approach predicted literature-supported dysregulated pathways complementary to both node-centric (SPIA, DAVID, and GATHER) and edge-centric (ESEA and PAGI) methods. Moreover, by proposing a novel pattern of aberrant signaling called V-structures, we observed that genes were dysregulated in resistant-vs-sensitive conditions when they were involved in the switch of dependencies from targeted to bypass signaling events. A literature survey of some important V-structures suggested they play a role in breast cancer metastasis and/or acquired resistance to EGFR-TKIs, where the mRNA changes of TGFBR2, LEF1 and TP53 in resistant-vs-sensitive conditions were related to the dependency switch from targeted to bypass signaling links. Our results suggest many signaling pathway structures are compromised in acquired resistance, and V-structures of aberrant signaling within/among those pathways may provide further insights into the bypass mechanism of targeted inhibition.

[Advances in the Research of Autophagy in EGFR-TKI Treatment and Resistance in Lung Cancer]

表皮生长因子受体激酶抑制剂（epidermal growth factor receptor-tyrosine kinase inhibitor, EGFR-TKI）是一类针对肿瘤细胞中EGFR的异常活化而开发的肿瘤靶向药物，可以有效抑制带有EGFR敏感突变的肿瘤细胞的生长。然而先天性以及获得性耐药严重制约了该类药物的使用。近些年的研究发现自噬（autophagy），作为一个细胞编码的高度保守的应对压力的存活机制，其与肿瘤的发生发展及抗肿瘤药物的耐药密切相关。EGFR的激活可以通过多条通路调控自噬。EGFR-TKI也可以诱导自噬，且自噬在EGFR-TKI的治疗和产生耐药性的过程中发挥着双刃剑的作用：一方面EGFR-TKI诱导的自噬是肿瘤细胞的一个保护机制，联合使用自噬抑制剂可以增强药物的细胞毒性效果；同时还有研究证明EGFR-TKI诱导的高水平自噬可以在凋亡缺陷的细胞中造成自噬性死亡，这种情况下联合使用自噬诱导剂则可能产生更好的效果。因此，针对不同的情况通过调控自噬以提高EGFR-TKI的治疗效果是一个颇具前景的治疗方案。本文对EGFR-TKI和自噬相关的信号通路进行了阐述，并对自噬在EGFR-TKI类药物对肺癌的治疗和耐药中作用的最新研究进展进行了总结，为设计联合方案提高EGFR-TKI的抑制效果，降低耐药性提供线索。

Mechanisms of resistance to EGFR tyrosine kinase inhibitors

Since the discovery that non-small cell lung cancer (NSCLC) is driven by epidermal growth factor receptor (EGFR) mutations, the EGFR tyrosine kinase inhibitors (EGFR-TKIs, e.g., gefitinib and elrotinib) have been effectively used for clinical treatment. However, patients eventually develop drug resistance. Resistance to EGFR-TKIs is inevitable due to various mechanisms, such as the secondary mutation (T790M), activation of alternative pathways (c-Met, HGF, AXL), aberrance of the downstream pathways (K-RAS mutations, loss of PTEN), impairment of the EGFR-TKIs-mediated apoptosis pathway (BCL2-like 11/BIM deletion polymorphism), histologic transformation, ATP binding cassette (ABC) transporter effusion, etc. Here we review and summarize the known resistant mechanisms to EGFR-TKIs and provide potential targets for development of new therapeutic strategies.

Hepatocyte growth factor expression in EGFR mutant lung cancer with intrinsic and acquired resistance to tyrosine kinase inhibitors in a Japanese cohort

INTRODUCTION

This study was performed to determine the incidence rates of resistance factors, i.e., high-level hepatocyte growth factor (HGF) expression, epidermal growth factor receptor (EGFR) T790M secondary mutation, and MET amplification, in tumors with intrinsic and acquired EGFR tyrosine kinase inhibitor (TKI) resistance in EGFR mutant lung cancer.

METHODS

Ninety-seven specimens from 93 EGFR mutant lung cancer patients (23 tumors with acquired resistance from 20 patients, 45 tumors with intrinsic resistance from 44 patients [nonresponders], 29 sensitive tumors from 29 patients) from 11 institutes in Japan were analyzed. HGF expression, EGFR T790M secondary mutation, and MET amplification were determined by immunohistochemistry, cycleave real-time polymerase chain reaction, and fluorescence in situ hybridization, respectively.

RESULTS

High-level HGF expression, EGFR T790M secondary mutation, and MET amplification were detected in 61, 52, and 9% of tumors with acquired resistance, respectively. High-level HGF expression was detected in 29% of tumors with intrinsic resistance (nonresponders), whereas EGFR T790M secondary mutation and MET amplification were detected in 0 and 4%, respectively. HGF expression was significantly higher in tumors with acquired resistance than in sensitive tumors (p < 0.001, Student's t test). Fifty percent of tumors with acquired resistance showed simultaneous HGF expression with EGFR T790M secondary mutation and MET amplification.

CONCLUSIONS

High-level HGF expression was detected more frequently than EGFR T790M secondary mutation or MET amplification in tumors with intrinsic and acquired EGFR-TKI resistance in EGFR mutant lung cancer in Japanese patients. These observations provide a rationale for targeting HGF in EGFR-TKI resistance in EGFR mutant lung cancer.

The Pharmacogenetic Rescue of Side-Lined Anticancer Drugs to the Front-Line: Gefitinib as a Case Example

OBJECTIVE

To illustrate the increasing importance of pharmacogenetics in drug development and clinical practice through a critical analysis of the validation and licensing of gefitinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, as a treatment for non-small cell lung cancer (NSCLC).

DATA SOURCES

Journal articles and the "grey" literature were identified through a systematic search of MEDLINE (to June 2010) and the Web sites of the major drug regulators. References identified through the reference lists of major published reviews of gefitinib and Erb receptors, including EGFR, were also reviewed.

STUDY SELECTION AND DATA EXTRACTION

A broad appraisal of the titles and abstracts of articles on gefitinib and tyrosine kinase inhibitors in lung cancer was undertaken to identify pertinent concepts and relevant publications for further analysis. Articles deemed particularly relevant were retrieved for detailed appraisal. Dossiers on the licensing of gefitinib from the Food and Drug Administration Web site and major published reviews were retrieved. Relevant pharmacogenetic issues were identified and the clinical studies addressing these were evaluated.

DATA SYNTHESIS

Initial promising trial data for gefitinib in NSCLC led to its conditional marketing approval. When the drug's efficacy was not confirmed in a pivotal Phase 3 trial, its prescribing was restricted. Subsequent discovery of activating mutations in the tyrosine kinase domain of EGFR led to further retrospective and prospective evaluation of the drug in patients with those mutations. The new evidence was sufficiently robust to persuade the drug regulators to license the drug as first-line treatment for patients with locally advanced or metastatic NSCLC who test positive for those mutations.

CONCLUSIONS

Pharmacogenetic evidence has played a key role in rescuing gefitinib for front-line treatment of NSCLC. This case-example portends what will be increasingly likely scenarios in the regulation and clinical validation of targeted drug therapies.

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.