A Novel Insertion Mutation on Exon 20 of Epidermal Growth Factor Receptor,Conferring Resistance to Erlotinib

The epidermal growth factor receptor (EGFR) is a transmembrane glycoprotein tyrosine kinase receptor. The small-molecule tyrosine kinase receptor inhibitors (TKIs) are in clinical use to treat non-small cell lung cancer with EGFR mutations. Variable tumor responses to erlotinib and gefitinib have been observed. The response to these TKIs varies by the type of EGFR mutations found in the tumor. The deletion on exon 19 and the L858R substitution on exon 21 constitute the most frequent mutations and are known to show good response to TKIs. However, mutations on exon 20 are less common and seem to respond poorly to TKIs. In clinical settings, the reported response of exon 20 mutations to reversible TKIs (both gefitinib and erlotinib) remains inconstant. The type of coexisting mutation seems to affect the response of these insertions to TKIs. We herein present a case of disease progression despite the use of erlotinib in a female patient who had a novel insertion mutation on exon 20. Our patient was a never-smoker and was identified to have a Pro772_His773insGlnCysPro mutation on exon 20. She had previously been treated with cisplatin and gemcitabine and then with carboplatin and pemetrexed. She was treated with erlotinib upon intolerance to second-line chemotherapy and did not respond. Our patient had a novel insertion mutation on exon 20, which was found to be resistant to erlotinib.Key words: Epidermal growth factor receptor, Tyrosine kinase receptor inhibitors, Mutations, Exon 20, Non-small cell lung cancer, Erlotinib     

Characterization of epidermal growth factor receptor mutations in non-small-cell lung cancer patients of African-American ancestry

Epidermal growth factor receptor (EGFR) mutations are predictive markers for response to EGFR tyrosine kinase inhibitors (EGFR-TKIs) in non-small-cell lung cancer (NSCLC). The most common mutations, exon 19 short deletions and exon 20 point mutation (L858R), activate the tyrosine kinase and confer sensitivity to EGFR-TKIs. However, the function and sensitivity of rare mutations to EGFR-TKIs are unknown. In this study, we found five EGFR mutations out of 16 patients with NSCLC of African-American descent. The frequency of such mutations in this patient population appears to be significantly higher than previously reported. Two of them (N771GY and A767-V769dup) are rare insertion mutations located in exon 20. Using YFP-tagged EGFR mutants, we demonstrated that the mutations confer increased kinase activity, but no sensitivity to erlotinib at clinically available concentrations. In addition, we examined efficacy of PF00299804, an irreversible EGFR-TKI. Although the drug failed to show efficacy to T790M and S768N mutations, the exon 20 insertion mutations were sensitive to PF00299804. These data suggest that rare mutations in exon 20 are resistant to erlotinib but may be sensitive to irreversible inhibitors.     

Epidermal growth factor receptor activation: how exon 19 and 21 mutations changed our understanding of the pathway.

The discovery of epidermal growth factor receptor (EGFR) mutations in never-smokers has been the most relevant finding ever in non-small cell lung cancer. When patients whose tumors bear the sensitizing mutations are treated with the tyrosine kinase inhibitors gefitinib or erlotinib, we witness response rates and durations never before reported, including complete responses. At the same time, the presence of EGFR mutations has raised numerous new questions, tantalizing data, and new challenges for treatment. This is particularly true as we try to generalize the findings in lung cancer to other malignancies. The indiscriminate use of gefitinib or erlotinib in the general lung cancer population results in meager survival benefit for patients. Similarly, the tyrosine kinase inhibitors have limited activity in a variety of tumor types with EGFR overexpression. This has led to the question of whether EGFR remains a viable target in patients other than those whose tumors contain mutations, and whether the modest activity of cetuximab in colorectal cancer and head and neck cancer represents all that we can expect from inhibition of this pathway in the absence of mutation. Mechanisms of pathway activation other than mutation have been discovered in recent years, and include overexpression mediated by gene amplification or by amplification of a dinucleotide repeat in the EGFR promoter, mutation of an extracellular region on EGFR generating a mutant protein termed EGFRvIII, and enhanced signaling due to heterodimerization with other members of the EGFR family, particularly overexpression of HER2/HER3. The extent to which these paths to EGFR activation will confer sensitivity to the tyrosine kinase inhibitors or to EGFR monoclonal antibodies is being explored. Thus far, published clinical data suggest that there is little room for the administration of gefitinib or erlotinib in the absence of EGFR mutations. The five articles in this edition of CCR Focus will address the various mechanisms of EGFR pathway activation and provide insight into the potential for translation into clinical relevance.     

Prolonged survival with erlotinib followed by afatinib in a caucasian smoker with metastatic,poorly differentiated large cell carcinoma of the lung: a case report

Activating mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR; ErbB1) – either exon 19 deletions or exon 21 point mutations – are associated with hypersensitivity to EGFR tyrosine kinase inhibitors (TKIs). EGFR mutations are more frequently found in females, non-smokers, Asians, and patients with adenocarcinoma. We report the case of a 51-year-old Caucasian woman with metastatic NSCLC harboring an EGFR exon 19 deletion although she was a smoker and had a poorly differentiated large cell carcinoma. Following a partial response on 4 months of chemotherapy, the patient progressed and was treated with the reversible EGFR TKI erlotinib for 3 y. The patient then developed resistance to erlotinib and went on to receive the irreversible ErbB Family Blocker afatinib for 1 year, attaining a partial response at 4 months. The impressive survival time attained by our patient highlights the clinical benefit of targeting one or more members of the ErbB Family in patients with disseminated NSCLC and EGFR activating mutations.     

A novel EGFR nonsense mutation in a non-small-cell lung cancer (NSCLC) patient who did not derive any clinical benefit with combination chemotherapy and erlotinib

Most of the somatic epidermal growth factor receptor (EGFR) mutations described to date in non-smallcell lung cancer (NSCLC) patients are located in the kinase domain and are considered activating mutations. Some of these mutations are associated with response to specific EGFR tyrosine kinase inhibitors (TKI) such as gefitinib and erlotinib. Here we report a case of a previously undescribed EGFR nonsense mutation in a lung adenocarcinoma patient who did not derive any clinical benefit with combination chemotherapy and erlotinib. To the best of our knowledge this is the second report in the literature describing an EGFR nonsense mutation in lung cancer patients.     

Mutations in the epidermal growth factor receptor gene are linked to smoking-independent, lung adenocarcinoma

Epidermal growth factor receptor (EGFR) mutations are a potential predictor of the effectiveness of EGFR inhibitors for the treatment of lung cancer. Although EGFR mutations were reported to occur with high frequency in nonsmoking Japanese adenocarcinoma patients, the exact nature has not been fully elucidated. We examined EGFR gene mutations within exons 18-21 and their correlations to clinico-pathological factors and other genetic alterations in tumour specimens from 154 patients who underwent resection for lung cancer at Kyoto University Hospital. Epidermal growth factor receptor mutations were observed in 60 tumours (39.0%), all of which were adenocarcinoma. Among the patients with adenocarcinoma (n=108), EGFR mutations were more frequently observed in nonsmokers than former smokers or current smokers (83.0, 50.0, 15.2%, respectively), in women than men (76.3 vs 34.0%), in tumours with bronchio-alveolar component than those without bronchio-alveolar component (78.9 vs 42.9%), and in well or moderately differentiated tumours than poorly differentiated tumours (72.0, 64.4, 34.2%). No tumours with EGFR mutations had any K-ras codon 12 mutations, which were well-known smoking-related gene mutations. In conclusion, adenocarcinomas with EGFR mutation had a distinctive clinico-pathological feature unrelated to smoking. Epidermal growth factor receptor mutations may play a key role in the development of smoking-independent adenocarcinoma.     

Tyrosine Kinase Inhibitors in EGFR-Mutated Large-Cell Neuroendocrine Carcinoma of the Lung? A Case Report

Large-cell neuroendocrine carcinoma (LCNEC) of the lung is a high-grade carcinoma belonging to the neuroendocrine tumors of the lung and is different from typical lung large-cell carcinoma. It represents about 3% of all pulmonary malignancies and is characterized by neuroendocrine cytologic features. The treatment usually is platinum-based chemotherapy, however the outcome remains poor. Therefore new therapeutic options are needed. Tyrosine kinase inhibitors have demonstrated greater efficacy and better tolerability than standard chemotherapy in non-small-cell lung cancer harboring epidermal growth factor receptor (EGFR) mutations. EGFR gene mutations were also rarely identified in LCNEC. We report a patient with lung LCNEC activating EGFR mutations who showed an impressive response to gefitinib.Key words: Large-cell neuroendocrine carcinoma, Epidermal growth factor receptor mutation, Tyrosine kinase inhibitors, Gefitinib     

Epidermal growth factor receptor mutations in non-small-cell lung cancer: implications for treatment and tumor biology.

The epidermal growth factor receptor (EGFR) has emerged as an attractive therapeutic target for patients with non-small-cell lung cancer (NSCLC). However, despite its almost universal presence in NSCLC tumors, therapeutic inhibition of EGFR has resulted in significant tumor regressions in only 10% to 20% of patients. Several investigations over the last 12 months have uncovered somatic mutations in EGFR that underlie the sensitivity to EGFR inhibitors. NSCLC tumors and cell lines with EGFR mutations are exquisitely sensitive to the EGFR tyrosine kinase inhibitors (TKIs), erlotinib and gefitinib, and are biologically distinct from other forms of NSCLC. Somatic mutations in EGFR are found more frequently in patients with adenocarcinomas, nonsmokers, patients of Asian ethnicity, and in females. EGFR mutation detection is now becoming clinically available and is being incorporated into clinical treatment decisions and into the design of future clinical trials. Mutations in K-ras, a mediator of EGFR signaling, are mutually exclusive with EGFR mutations, and are associated with resistance to EGFR TKIs. In addition, secondary mutations, conferring resistance to EGFR TKIs, in patients with primary EGFR mutations once sensitive to EGFR TKIs, are beginning to be identified. The frequency of EGFR mutations, their impact on NSCLC biology, clinical treatment, and clinical trial design, as well as methods and limitations for mutation detection, will be reviewed.     

An early event of EGFR mutation in pleomorphic carcinoma of the lung

Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are effective in prolonging progression-free survival time of patients with non-small cell lung carcinoma, typically adenocarcinoma, bearing some active EGFR mutations in their tumors. However, the close relationship between the EGFR mutations and pleomorphic carcinoma of the lung, which is a very rare type of primary lung cancer, has never been elucidated. We present a 60-year-old Japanese woman with pleomorphic carcinoma of the lung that became resistant to cytotoxic chemotherapies including platinum-based chemotherapy, and her general condition seriously deteriorated. Thereafter, treatment with gefitinib was started and resulted in significant tumor shrinkage and a dramatic improvement in her general condition for up to 8.5 months. Analyses of the EGFR mutation in separately microdissected specimens from adenocarcinoma and spindle cell components revealed that both components possessed the L858R point mutation. These findings gave us some insight into the carcinogenesis of pleomorphic carcinoma of the lung in relation to EGFR gene alteration. Testing for EGFR mutation may be important in patients with advanced pleomorphic carcinoma including adenocarcinoma component that is usually chemoresistant.     

The KRAS StripAssay for detection of KRAS mutation in Egyptian patients with colorectal cancer (CRC): A pilot study

BackgroundEpidermal growth factor receptor (EGFR) and its downstream factors KRAS and BRAF are mutated in several types of cancer, affecting the clinical response to EGFR inhibitors. Mutations in the EGFR kinase domain predict sensitivity to the tyrosine kinase inhibitors gefitinib and erlotinib in lung adenocarcinoma, while activating point mutations in KRAS and BRAF confer resistance to the anti-EGFR monoclonal antibody cetuximab in colorectal cancer. The development of new generation methods for systematic mutation screening of these genes will allow more appropriate therapeutic choices.PurposeDetection of KRAS mutation in Egyptian colorectal cancer (CRC) patients by the KRAS StripAssay.MethodsExamination of 20 colorectal cancer (CRC) patients is done to detect KRAS mutations by KRAS StripAssay. For the StripAssay, a mutant-enriched PCR was followed by hybridization to KRAS-specific probes bound to a nitrocellulose strip.ResultsAmong 20 patients, KRAS mutations were identified in 80% of patients by the KRAS StripAssay.ConclusionsOur preliminary results suggest that KRAS StripAssay is an alternative to protocols currently in use for KRAS mutation detection.     

Poorly differentiated and anaplastic thyroid cancer.

BACKGROUND: Poorly differentiated thyroid carcinoma (PDTC) and anaplastic (undifferentiated) thyroid carcinoma (ATC) comprise a small subset of thyroid tumors that are associated with a poor prognosis and account for a significant portion of the morbidity and mortality related to thyroid cancer. Since management strategies vary between these two entities, it is important for clinicians to be able to differentiate PDTC from ATC. METHODS: We reviewed the literature on PDTC and ATC and compared clinical and histopathologic features important in defining the disease process. RESULTS: Both PDTC and ATC display aggressive behavior with increased locoregional and distant disease. In most cases, patients are older and have large, locally advanced tumors. PDTC may represent an intermediate entity in the progression of well-differentiated thyroid carcinoma to ATC. The use of surgical management may be curative or palliative and differs between PDTC and ATC. The roles of radiotherapy and chemotherapy have not been well described. CONCLUSIONS: PDTC and ATC are rare diseases that carry a poor prognosis. Recognition of their different clinicopathologic features is important to the optimal management of these tumors.     

The insulin‐like growth factor 1 receptor causes acquired resistance to erlotinib in lung cancer cells with the wild‐type epidermal growth factor receptor

Epidermal growth factor receptor (EGFR)‐tyrosine kinase inhibitor (TKI) therapy often provides a dramatic response in lung cancer patients with EGFR mutations. In addition, moderate clinical efficacy of the EGFR‐TKI, erlotinib, has been shown in lung cancer patients with the wild‐type EGFR. Numerous molecular mechanisms that cause acquired resistance to EGFR‐TKIs have been identified in lung cancers with the EGFR mutations; however, few have been reported in lung cancers with the wild‐type EGFR. We used H358 lung adenocarcinoma cells lacking EGFR mutations that showed modest sensitivity to erlotinib. The H358 cells acquired resistance to erlotinib via chronic exposure to the drug. The H358 erlotinib‐resistant (ER) cells do not have a secondary EGFR mutation, neither MET gene amplification nor PTEN downregulation; these have been identified in lung cancers with the EGFR mutations. From comprehensive screening of receptor tyrosine kinase phosphorylation, we observed increased phosphorylation of insulin‐like growth factor 1 receptor (IGF1R) in H358ER cells compared with parental H358 cells. H358ER cells responded to combined therapy with erlotinib and NVP‐AEW541, an IGF1R‐TKI. Our results indicate that IGF1R activation is a molecular mechanism that confers acquired resistance to erlotinib in lung cancers with the wild‐type EGFR.     

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。     

Gefitinib and epidermal growth factor receptor gene mutation

Epidermal growth factor receptor (EGFR) gene mutations are frequent in lung cancer of Asian ethnicity, female gender, non-smokers,and of adenocarcinoma histology. About 80% of the patients with EGFR mutations respond to EGFR tyrosine kinase inhibitor (TKI) including gefitinib and erlotinib, while only 10% of those without EGFR mutations do so. Therefore, EGFR mutation is being recognized as one of the most reliable predictive factors in gefitinib treatment. Another important issue in clinical practice is fatal interstitial lung disease (ILD) in patients with gefitinib treatment, especially for Asian patients. A nested case-control study recently conducted in Japan identified some risk factors which cause ILD. About half of the acquired resistance to gefitinib that almost always occurs during the course of gefitinib administration is reportedly caused by secondary mutation at codon 79 0 (T 79 0 M). EGFR-TKIs are not universally effective for lung cancer,but these drugs are effective in patients who have particular characteristics. Therefore, patients who would benefit from gefitinib therapy should be included in clinical trials. Based on this concept, phaseIII clinical trials comparing gefitinib monotherapy with standard platinum-based chemotherapy in lung cancer patients with EGFR mutations are ongoing.     

Mechanisms of acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors in non-small cell lung cancer.

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors gefitinib and erlotinib are effective therapies for non-small cell lung cancer patients whose tumors harbor somatic mutations in EGFR. All patients, however, ultimately develop resistance to these agents. Thus, there is a great need to understand how patients become resistant to develop effective therapies for these cancers. Studies over the last few years have identified two different EGFR tyrosine kinase inhibitor resistance mechanisms, a secondary mutation in EGFR, EGFR 790M, and amplification of the MET oncogene. These findings have led to clinical trials using newly designed targeted therapies that can overcome these resistance mechanisms and have shown promise in laboratory studies. Ongoing research efforts will likely continue to identify additional resistance mechanisms, and these findings will hopefully translate into effective therapies for non-small cell lung cancer patients.     

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.     

PF00299804, an irreversible pan-ERBB inhibitor, is effective in lung cancer models with EGFR and ERBB2 mutations that are resistant to gefitinib

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors gefitinib and erlotinib are effective treatments for a subset of non-small cell lung cancers. In particular, cancers with specific EGFR-activating mutations seem to be the most sensitive to these agents. However, despite their initial response, such cancers almost invariably develop resistance. In 50% of such cancers, a secondary EGFR mutation, T790M, has been identified that renders gefitinib and erlotinib ineffective inhibitors of EGFR kinase activity. Thus, there is a clinical need to develop novel EGFR inhibitors that can effectively inactivate T790M-containing EGFR proteins. In this study, we evaluate the effectiveness of a novel compound, PF00299804, an irreversible pan-ERBB inhibitor. The results from these studies show that PF00299804 is a potent inhibitor of EGFR-activating mutations as well as the EGFR T790M resistance mutation both in vitro and in vivo. Additionally, PF00299804 is a highly effective inhibitor of both the wild-type ERBB2 and the gefitinib-resistant oncogenic ERBB2 mutation identified in lung cancers. These preclinical evaluations support further clinical development of PF00299804 for cancers with mutations and/or amplifications of ERBB family members.     

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.