Epidermal Growth Factor Receptor Mutant Lung Adenocarcinoma Research Articles

High Incidence of EGFR Mutations in Korean Men Smokers with No Intratumoral Heterogeneity of Lung Adenocarcinomas: Correlation with Histologic Subtypes, EGFR/TTF-1 Expressions, and Clinical Features

Epidermal growth factor receptor (EGFR) mutation has been known to be associated with adenocarcinoma with bronchioloalveolar carcinoma (BAC; lepidic) feature. This study was aimed to characterize the frequency of EGFR mutations and their association with histologic subtypes in Korean nonsmall cell lung cancer (NSCLC) patients. Three hundred eighty-two (88 biopsies and 294 resections) NSCLC patients were investigated for EGFR mutations (exons 18-21) by polymerase chain reaction and direct sequencing method. For the resected adenocarcinoma specimens, histologic subtypes were classified according to both 2004 World Health Organization classification and 2011 International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society classification. The results were correlated with EGFR mutation and clinicopathologic features. EGFR mutations were detected in 196 of 382 NSCLCs (51.3%) and were more frequent in women than in men (65.7% versus 34.3%, p < 0.001) and in nonsmokers than in smokers (63.4% versus 32.0%, p < 0.001). Regarding histologic subtypes of adenocarcinoma, mixed acinar and BAC pattern showed the most frequent EGFR mutation (67.6%), followed by mixed papillary and acinar (65.2%), mixed solid and acinar (38.2%), micropapillary and acinar (30.4%), and acinar and mucinous BAC (13.3%). In addition, EGFR mutations were more frequently observed in tumors with BAC or papillary components than those with mucinous BAC or solid components. Identical EGFR mutations were detected in a single tumor showing mixed histological features. EGFR protein expression was seen more frequently in tumors with EGFR mutations than those without EGFR mutations (75.3% versus 24.7%, p=0.003). EGFR mutations were significantly more common in tumors with thyroid transcription factor-1 (TTF-1) expression than those without TTF-1 (p < 0.001), and almost all (92.7%) mutated adenocarcinomas were TTF-1 positive. The incidence of EGFR mutations is variable according to histologic subtypes, gender, and smoking history. The mixed acinar and BAC and papillary and acinar subtypes, the presence of BAC (lepidic) or papillary components, EGFR, and TTF-1 protein expression can predict higher EGFR mutation in lung adenocarcinoma. However, intratumoral heterogeneity of EGFR mutation was not found. In addition, relatively high incidence of EGFR mutations in Korean men who smoked with adenocarcinoma histology suggests that these patients should not be left behind EGFR mutation test.

Nomogram to predict the presence of EGFR activating mutation in lung adenocarcinoma

Epidermal growth factor receptor (EGFR) tumour genotyping is crucial to guide treatment decisions regarding the use of EGFR tyrosine kinase inhibitors in nonsmall cell lung cancer (NSCLC). However, some patients may not be able to obtain tumour testing, either because tissue is limited and/or tests are not routinely offered. Here, we aimed to build a model-based nomogram to allow for prediction of the presence of EGFR mutations in NSCLC. We retrospectively collected clinical and pathological data on 3,006 patients with NSCLC who had their tumours genotyped for EGFR mutations at five institutions worldwide. Variables of interest were integrated in a multivariate logistic regression model. In the 2,392 non-Asian patients with lung adenocarcinomas, the most important predictors of harbouring EGFR mutation were: lower tobacco smoking exposure (OR 0.41, 95% CI 0.37-0.46), longer time interval between smoking cessation and diagnosis (OR 2.19, 95% CI 1.71-2.80), advanced stage (OR 1.58, 95% CI 1.18-2.13), and papillary (OR 4.57, 95% CI 3.14-6.66) or bronchioloalveolar (OR 2.84, 95% CI 1.98-4.06) histologically predominant subtype. A nomogram was established and showed excellent discriminating accuracy: the concordance index on an independent validation dataset was 0.84. As clinical practices transition to incorporating genotyping as part of routine care, this nomogram could be highly useful to predict the presence of EGFR mutations in lung adenocarcinoma in non-Asian patients when mutational profiling is not available or possible.

Abstract LB-398: Identification of novel mechanisms of resistance to EGFR tyrosine kinase inhibitors in non-small cell lung cancer

Abstract Most lung adenocarcinoma patients with activating mutations in the Epidermal Growth Factor Receptor (EGFR) gene initially respond to EGFR tyrosine kinase inhibitors (TKIs), such as erlotinib and gefitinib. However, most patients eventually acquire resistance to this class of drugs. In approximately half of all resistant tumors this is caused by a secondary EGFR mutation (T790M) and/or by amplification of the MET tyrosine kinase receptor, yet the cause of resistance in the remainder of cases is largely unknown. In this study, we aim to identify novel determinants of resistance to EGFR TKIs in order to find new drug targets that may increase the effectiveness of EGFR targeted therapy. We performed a genome-wide siRNA screen examining cell viability in the presence and absence of erlotinib. We used a lung adenocarcinoma cell line (PC9) with activated EGFR that is highly sensitive to erlotinib. We selected hits as genes that upon knockdown showed increased cell viability in drug treated versus untreated conditions. Within the list of candidate genes is the tumor suppressor Neurofibromin (NF1). Using multiple shRNA constructs, we confirmed the enhanced survival in the presence of erlotinib upon NF1 knockdown in a number of EGFR mutant lung adenocarcinoma cell lines using different cell viability and cell competition assays. NF1 is a known negative regulator of RAS activity. We observed increased RAS activity and MAPK signaling in cells where NF1 was knocked down using RNA interference and found that this was resistant to inhibition by erlotinib. Moreover, treatment with low doses of MEK inhibitors resensitized the NF1 knockdown cells to erlotinib. To assess the relevance of this resistance mechanism in vivo, we made use of a tetracycline-inducible mouse model of EGFR-dependent lung cancer. Prolonged erlotinib treatment of lung tumor-bearing mice leads to the outgrowth of resistant tumors. Evaluation of the expression levels of Nf1 in erlotinib-resistant tumors in this preclinical model showed low Nf1 mRNA levels in about half of all erlotinib resistant tumors when compared to the levels in normal adjacent lung. Interestingly, tumors bearing the EGFR-T790M mutation do not show decreased Nf1 expression. These observations suggest that decreased NF1 might be a novel resistance mechanism in EGFR-driven lung tumors. Together, our results show that reduced NF1 expression leads to resistance to erlotinib in EGFR mutant lung adenocarcinomas via enhanced RAS and MAPK pathway activity. Since NF1 is known to be mutated in a subset of lung adenocarcinomas, it is possible that NF1 mutations or loss of expression in EGFR mutant lung tumors could result in de novo or acquired resistance to EGFR inhibitors and that these patients may benefit from treatment with a MEK inhibitor in combination with continued EGFR tyrosine kinase inhibitor. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-398. doi:10.1158/1538-7445.AM2011-LB-398

Restoration of tumour suppressor hsa-miR-145 inhibits cancer cell growth in lung adenocarcinoma patients with epidermal growth factor receptor mutation

Background In Hong Kong, about 30% of non-small cell lung cancer patients have never smoked tobacco. Among women, 83% are never-smokers and their histological type is invariably adenocarcinoma with 70% incidence of epidermal growth factor receptor ( EGFR) mutation. The present study focuses on the microRNA (miRNA) expression profiles of this important subset of lung cancer. Methods Paired samples collected from the lung cancer tissue and adjacent normal lung parenchyma of 10 non-smoking patients with lung adenocarcinoma were profiled by miRNA microarray. Results were validated by quantitative reverse transcription polymerase chain reaction. Transfected cell viability assays were applied to determine the effects of candidate miRNAs on lung cancer cells. Results Comparing paired lung cancer tissue with adjacent normal lung parenchyma, hsa-miR-126 ∗, hsa-miR-145, hsa-miR-21, hsa-miR-182, hsa-miR-183 and hsa-miR-210 were found to be the most differentially expressed miRNAs. Most interestingly, an obvious inhibition of cell growth was observed in the EGFR mutant lung adenocarcinoma after transfection of hsa-pre-miR-145. Conclusions Our study is the first report to connect miR-182 to lung cancer. Our results also show that restoration of tumour suppressor hsa-miR-145 inhibits cancer cell growth in EGFR mutant lung adenocarcinoma. Further study on these specific differentially expressed miRNAs may provide important information on peculiar tumourigenetic pathways and may identify useful biomarkers.

Correlation between morphology and EGFR mutations in lung adenocarcinomas: Significance of the micropapillary pattern and the hobnail cell type

The presence of epidermal growth factor receptor (EGFR) tyrosine kinase (TK) mutations significantly correlates with tumor sensitivity to TK inhibitors, particularly in lung adenocarcinomas, the predominant histological subtype in Japan and the United States. To clarify links between EGFR mutations and pathological findings in Japanese lung cancer, detailed pathological features of adenocarcinomas were examined using the WHO criteria as well as our cell type classification (hobnail, columnar and polygonal). Medical records were reviewed for a total of 107 surgically resected tumors. Clinicopathological factors were examined and correlations with EGFR status were evaluated. EGFR mutations were found in 63 patients (59%) distributed through all four exons examined (through exons 18-21). EGFR mutations were significantly associated with female gender (P=0.003), non-smoker status (P=0.008) and hobnail cell morphology (P<0.00001). In addition, detailed pathological examination showed significant associations with bronchioloalveolar carcinoma (BAC) component and a micropapillary pattern (MPP) (P=0.012 and 0.043, respectively). We conclude that characteristic histological features, i.e. the hobnail cell morphology and the presence of BAC component and MPP are good predictors of EGFR mutations in lung adenocarcinoma.

EGFR Mutations in Lung Adenocarcinomas : Clinical Testing Experience and Relationship to EGFR Gene Copy Number and Immunohistochemical Expression

Lung adenocarcinomas responsive to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors possess EGFR mutations and often increased EGFR copy number. We prospectively studied 334 clinical cases using polymerase chain reaction-based assays to detect deletions within exon 19 and the L858R mutation in exon 21, which together account for approximately 90% of EGFR mutations. Seventy-eight (23%) of these tumors had an EGFR mutation, with 55 (71%) exon 19 deletions and 23 (29%) exon 21 L858R mutations. We were able to compare mutant and normal EGFR alleles and found a preferential amplification of the mutant allele. The association of mutations with EGFR amplification (determined by chromogenic in situ hybridization) and EGFR expression (determined by immunohistochemistry) was further examined in a subset of 60 tumors. EGFR amplification (> or =5 EGFR signals per nucleus) was seen in 15 of 29 (52%) EGFR-mutated tumors but in only five of 31 (6%) non-mutated tumors (P = 0.006). EGFR overexpression was strongly associated with amplification but was statistically independent of EGFR mutation. Most patients with EGFR mutations (17 of 29, 59%) never smoked compared with 13% (four of 31) of patients lacking such mutations (P = 0.0003). The association of amplification with smoking status was marginal and was nonexistent with EGFR expression. Thus, these results indicate that EGFR amplification, preferentially of the mutant allele, often accompanies EGFR mutation, whereas EGFR immunohistochemical staining associates with amplification but cannot predict EGFR mutation status.

Female Sex and Bronchioloalveolar Pathologic Subtype Predict EGFR Mutations in Non-small Cell Lung Cancer

The prevalence of epidermal growth factor receptor (EGFR) mutations in gefitinib-naive lung cancer patients is higher in adenocarcinomas, in women, and in Japanese. To further investigate the prevalence of EGFR mutations in relation to ethnic and geographic factors, we evaluated EGFR mutations in a series of Taiwanese patients with primary lung adenocarcinomas who had never been treated with gefitinib. We retrospectively studied 35 primary lung adenocarcinoma samples for mutations in the tyrosine kinase domain of EGFR; exons 18, 19, and 21 were analyzed by nested polymerase chain reaction and automated sequencing. Clinicopathologic information was obtained from patient records and pathology reports. Correlation between EGFR mutations and patient characteristics, including sex, smoking history, and pathologic subtypes, were evaluated by using the chi(2) test and logistic regression analysis. Heterozygous EGFR mutations were detected in 17 of 35 patients (48%). Missense mutations in exon 21 (13 of 17 patients, 76%) were the most frequent mutations detected. EGFR mutations were more frequent in women (13 of 18 patients [72%]) than in men (4 of 17 patients [23%]; p = 0.004), more frequent in nonsmokers (14 of 21 patients [66%]) than in current smokers (3 of 14 patients [21%]; p = 0.009), and when any degree of bronchioloalveolar carcinoma (BAC) was present (14 of 21 patients [66%]) compared with pure adenocarcinoma (3 of 14 patients [21%]; p = 0.009). Logistic regression analysis demonstrated that female gender (odds ratio [OR], 10.913; 95% confidence interval [CI], 1.778 to 66.97; p = 0.01) and BAC, including adenocarcinomas with any bronchioloalveolar features (OR, 9.708; 95% CI, 1.464 to 64.393; p = 0.019), were significantly associated with EGFR mutations. In our series, female sex and bronchioloalveolar pathologic subtype predicted the presence of EGFR mutations in lung adenocarcinomas, and the high frequency of EGFR mutations supports the hypothesis that genetic backgrounds and/or environmental factors may affect the pathogenesis of certain lung cancers.