EGFR Mutation Is Specific for Terminal Respiratory Unit Type Adenocarcinoma

Lung cancer preneoplasia

From histological and biological perspectives, lung cancer is a complex neoplasm. Although the sequential preneoplastic changes have been defined for centrally arising squamous carcinomas of the lung, they have been poorly documented for the other major forms of lung cancers, including small cell lung carcinoma and adenocarcinomas. There are three main morphologic forms of preneoplastic lesions recognized in the lung: squamous dysplasias, atypical adenomatous hyperplasia, and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia. However, these lesions account for the development of only a subset of lung cancers. Several studies have provided information regarding the molecular characterization of lung preneoplastic changes, especially for squamous cell carcinoma. These molecular changes have been detected in the histologically normal and abnormal respiratory epithelium of smokers. Two different molecular pathways have been detected in lung adenocarcinoma pathogenesis: smoking-associated activation of RAS signaling, and nonsmoking-associated activation of EGFR signaling; the latter is detected in histologically normal respiratory epithelium.

Why targeted therapy hasn't worked in advanced cancer

In this issue of the JCI, Nissen et al. report that a reciprocal interaction exists between the growth factors FGF2 and PDGF-BB, causing tumors to exhibit increased angiogenesis and metastatic potential. Both FGF2 and PDGF-BB signal through tyrosine kinase receptors, which have been the target of tyrosine kinase inhibitors for cancer therapies. These inhibitors are usually small molecules that inhibit the kinase activity of a receptor or nonreceptor tyrosine kinase, preventing downstream signaling. The results of this study shed light on why tyrosine kinase inhibitors have been useful for the treatment of only a small number of advanced cancers. Currently, a major focus of pharmaceutical companies is to develop ever more potent and specific tyrosine kinases. The results presented here suggest that this approach may not be successful.

Terminal respiratory unit type lung adenocarcinoma is associated with distinctive EGFR immunoreactivity and EGFR mutations

Approximately 10% to 20% of nonsmall cell lung cancer patients respond to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors, such as gefitinib. Responders are mostly nonsmokers and women with tumors displaying bronchioloalveolar features. Mutations of the tyrosine kinase domain of the EGFR gene have been associated with a clinical response to gefitinib. A recent study reported that the terminal respiratory unit (TRU)-type adenocarcinoma shares the clinical profile and EGFR mutations of gefitinib responders. EGFR immunoreactivity in this context has not been reported in the literature. We performed a detailed immunohistochemical analysis of EGFR expression on 124 consecutive lung resection specimens for malignancy, to survey the EGFR immunoreactivity in lung cancers in general and to correlate EGFR immunoreactivity with EGFR mutations and TRU-type histology. EGFR positivity was seen most frequently in squamous cell carcinomas (77%), followed by TRU-type adenocarcinomas (63%), large cell carcinomas (23%), and non-TRU-type adenocarcinomas (12%). A distinctive basally oriented cytoplasmic positivity was observed exclusively in TRU-type adenocarcinomas. EGFR mutation was identified in 6 of 54 cases studied and all 6 cases were TRU-type adenocarcinomas. Five of six cases with EGFR mutation were positive for EGFR immunostain with the basal cytoplasmic localization. In conclusion, EGFR immunoreactivity with basal cytoplasmic pattern was exclusively seen in TRU-type adenocarcinoma and a subset of these cases was seen with EGFR mutations in the responders to EGFR inhibitor therapy.

Chasing targets for EGFR tyrosine kinase inhibitors in non-small-cell lung cancer: Asian perspectives

EGF receptor (EGFR) activation has an important role in various steps of carcinogenesis and progression of non-small-cell lung cancer (NSCLC), implying that EGFR is a potential target for cancer therapy. Therefore, targeted treatments aimed at EGFR have been developed, of which tyrosine kinase inhibitors (TKIs), gefitinib and erlotinib have shown activity in NSCLC. The unexpected findings of a lack of association between expression of EGFR, the target and efficacy of EGFR TKIs and higher response in selective subgroups of patients were puzzling. Identification of somatic activating mutations in the EGFR tyrosine kinase domain solved the mystery and provided new insight. Several lines of study provided information on various molecular targets for EGFR TKI therapy. A target-based patient-selection strategy is expected to eventually lead to tailored therapy for lung cancer.

Mutation of the epidermal growth factor receptor gene in the development of adenocarcinoma of the lung

Recently, a mutation of the epidermal growth factor receptor (EGFR) gene has been reported to be implicated in the development of pulmonary adenocarcinoma. However, the involvement of the mutation in atypical adenomatous hyperplasia (AAH) and multiple adenocarcinomas still remains unclear. We herein examined the EGFR mutations in 9 AAH and 31 adenocarcinoma lesions obtained from 30 Japanese patients. Nine patients had synchronous or metachronous multiple adenocarcinomas and/or AAH. Mutations in exons 18-21 of EGFR gene were analysed using polymerase chain reaction and direct sequence methods. EGFR mutations were detected in 4 (44%) of 9 AAH and in 7 (23%) of 31 adenocarcinomas. A gefitinib-resistant point mutation (T790M) in exon 20 without gefitinib treatment was detected in 1 AAH and 1 adenocarcinoma. The patient with T790M mutated AAH, which also had an exon 19 mutation of D761Y, had synchronous adenocarcinoma, which had only an exon 19 mutation of D761Y. The other exon 19 mutations were all in-frame deletions. In the two patients with synchronous AAH and adenocarcinoma, AAH had mutations at exon 19 although adenocarcinoma did not have any mutations. In the patient with synchronous 2 adenocarcinomas, each had different mutations (exons 19 and 21). In two patients with double adenocarcinomas, 1 adenocarcinoma harbored exon 21 mutations, while the other demonstrated no mutations. Although EGFR mutations appeared to be partially associated with the early steps of adenocarcinoma development, such mutations may possibly occur randomly even in multiple lesions in a single patient.

Lung cancer in never smokers--a different disease

Although most lung cancers are a result of smoking, approximately 25% of lung cancer cases worldwide are not attributable to tobacco use, accounting for over 300,000 deaths each year. Striking differences in the epidemiological, clinical and molecular characteristics of lung cancers arising in never smokers versus smokers have been identified, suggesting that they are separate entities. This Review summarizes our current knowledge of this unique and poorly understood disease.

Smoking and cancer-related gene expression in bronchial epithelium and non-small-cell lung cancers

Tobacco smoking is the leading cause of lung cancer worldwide. Gene expression in surgically resected and microdissected samples of non-small-cell lung cancers (18 squamous cell carcinomas and nine adenocarcinomas), matched normal bronchial epithelium, and peripheral lung tissue from both smokers (n = 22) and non-smokers (n = 5) was studied using the Affymetrix U133A array. A subset of 15 differentially regulated genes was validated by real-time PCR or immunohistochemistry. Hierarchical cluster analysis clearly distinguished between benign and malignant tissue and between squamous cell carcinomas and adenocarcinomas. The bronchial epithelium and adenocarcinomas could be divided into the two subgroups of smokers and non-smokers. By comparison of the gene expression profiles in the bronchial epithelium of non-smokers, smokers, and matched cancer tissues, it was possible to identify a signature of 23 differentially expressed genes, which might reflect early cigarette smoke-induced and cancer-relevant molecular lesions in the central bronchial epithelium of smokers. Ten of these genes are involved in xenobiotic metabolism and redox stress (eg AKR1B10, AKR1C1, and MT1K). One gene is a tumour suppressor gene (HLF); two genes act as oncogenes (FGFR3 and LMO3); two genes are involved in matrix degradation (MMP12 and PTHLH); three genes are related to cell differentiation (SPRR1B, RTN1, and MUC7); and five genes have not been well characterized to date. By comparison of the tobacco-exposed peripheral alveolar lung tissue of smokers with non-smokers and with adenocarcinomas from smokers, it was possible to identify a signature of 27 other differentially expressed genes. These genes are involved in the metabolism of xenobiotics (eg GPX2 and FMO3) and may represent cigarette smoke-induced, cancer-related molecular targets that may be utilized to identify smokers with increased risk for lung cancer.

Pseudomesotheliomatous carcinoma of the lung with a distinct morphology, immunohistochemistry, and comparative genomic hybridization profile

We report 4 cases of pseudomesotheliomatous carcinoma of the lung, which has clinical and microscopic features similar to malignant mesothelioma, but with ultrastructural, immunohistochemical, and molecular characteristics suggestive of a histogenesis from type II pneumocytes. Neoplasm grows as a diffuse or solid pattern of large polygonal cells with sharply defined borders. Hale's colloidal iron is positive in the cytoplasm of small groups of cells and, focally, in some intercellular spaces. Ultrastructure showed short microvilli in the surface. Immunohistochemically, tumor cells were positive for thyroid transcription factor-1, podoplanin, mesothelin, pan-cytokeratin, CK-7, CK-19, Ber-EP4, epithelial membrane antigen, apoprotein surfactant A, epidermal growth factor receptor, Leu-M1, carcinoembryonic antigen, E-cadherin, and CD-44 and negative for mesothelioma markers thrombomodulin and calretinin. In some areas, there were small cysts which contained a concentric fibrilar basophilic material apoprotein surfactant A positive. Chromosomal imbalances with comparative genomic hybridization technique were identified with a median of 15 abnormalities per case (range, 1-26): 51 gains, 6 losses, and 1 high-level amplification. The most frequent aberrations among the cases were gains on chromosomes regions 1q, 3q, 5p, 8q, 16p, and 18q and losses in 17p11-13 and 17q 22-q25. High-level amplifications were detected on 7p13-p21. In all cases, there was a characteristic association between the gains on 16p and those on 18q. The 4 cases resulted in death in less than 14 months, in spite of complete surgery and chemotherapy in 2 cases. Our aim is to complement the current understanding of this pseudomesotheliomatous "pneumocytic" carcinoma and alert pathologists to this rare entity to avoid misdiagnosis.

Epidermal growth factor receptor gene mutations in atypical adenomatous hyperplasias of the lung

Activating epidermal growth factor receptor (EGFR) gene mutations are frequently detected in lung adenocarcinomas, especially adenocarcinomas with a nonmucinous bronchioloalveolar carcinoma component. EGFR-mutated lung adenocarcinomas respond well to EGFR tyrosine kinase inhibitors. We previously found that most (88%) pure nonmucinous bronchioloalveolar carcinomas (adenocarcinoma in situ) already harbor EGFR mutations, indicating that the mutations are an early genetic event in the pathogenesis. We examined 54 atypical adenomatous hyperplasias, precursor lesions of lung adenocarcinomas, obtained from 28 Japanese patients for the hotspot mutations of EGFR exons 19 and 21 and K-ras codon 12. EGFR mutations were observed in 17 of the 54 (32%) atypical adenomatous hyperplasias examined: Ten and seven atypical adenomatous hyperplasias had deletion mutations at exon 19 or point mutations (L858R) at exon 21, respectively. We did not observe apparent histological differences between atypical adenomatous hyperplasias with and without EGFR mutations. K-ras mutation (G12S) was detected in only one atypical adenomatous hyperplasia. As EGFR mutational frequency of atypical adenomatous hyperplasias was much lower than that of nonmucinous bronchioloalveolar carcinomas, we surmise that EGFR-mutated atypical adenomatous hyperplasias, but not atypical adenomatous hyperplasias with wild-type EGFR, are likely to progress to nonmucinous bronchioloalveolar carcinomas.

Disproportionate representation of KRAS gene mutation in atypical adenomatous hyperplasia, but even distribution of EGFR gene mutation from preinvasive to invasive adenocarcinomas

In the resected lung, additional small lesions are occasionally found incidentally, and include the full spectrum of preinvasive to invasive lesions under the current putative schema of the sequential development of lung cancer. In this study, we examined EGFR and KRAS gene mutations in 119 synchronous pulmonary lesions, including 40 precursor lesions (atypical adenomatous hyperplasia, AAH), 26 carcinomas in situ (non-mucinous bronchioloalveolar carcinoma, BAC), 14 minimally invasive adenocarcinomas, 34 overt invasive adenocarcinomas, and five of other subtypes of cancer. Although the mutually exclusive nature of KRAS and EGFR gene mutations was maintained even in preinvasive lesions, the incidences of the lesions along the putative progression schema were quite different. The KRAS gene was mutated in 33% of AAH, 12% of carcinomas in situ, 8% of minimally invasive adenocarcinomas and 0% of well-differentiated adenocarcinomas, whereas the frequencies of EGFR mutation did not fluctuate greatly, at 25%, 51%, 36%, 86% and 67%, respectively. These results are consistent with the findings of a published gene-targeted mouse model; the mice expressing oncogenic KRAS developed AAH but not invasive adenocarcinoma, whereas a spectrum of preinvasive to invasive adenocarcinomas was observed in the mice expressing mutant EGFR. Taking these factors together, it is suggested that AAH could develop by either KRAS or EGFR gene mutation, but AAH harbouring a KRAS gene mutation might not progress further to an invasive cancer.

Lineage-Specific Dependency of Lung Adenocarcinomas on the Lung Development Regulator TTF-1

Emerging evidence, although currently very sparse, suggests the presence of "lineage-specific dependency" in the survival mechanisms of certain cancers. TTF-1 has a decisive role as a master regulatory transcription factor in lung development and in the maintenance of the functions of terminal respiratory unit (TRU) cells. We show that a subset of lung adenocarcinoma cell lines expressing TTF-1, which presumably represent those derived from the TRU lineage, exhibit marked dependence on the persistent expression of TTF-1. The inhibition of TTF-1 by RNA interference (RNAi) significantly and specifically induced growth inhibition and apoptosis in these adenocarcinoma cell lines. Furthermore, a fraction of TTF-1-expressing tumors and cell lines displayed an increase in the gene dosage of TTF-1 in the analysis of 214 patients with non-small-cell lung cancer, including 174 adenocarcinomas, showing a tendency of higher frequency of increased gene copies at metastatic sites than at primary sites (P=0.07, by two-sided Fisher's exact test). These findings strongly suggest that in addition to the development and maintenance of TRU lineages in normal lung, sustained TTF-1 expression may be crucial for the survival of a subset of adenocarcinomas that express TTF-1, providing credence for the lineage-specific dependency model.

Gene expression profiling of epidermal growth factor receptor/KRAS pathway activation in lung adenocarcinoma

We examined the genome-wide expression profiles of 86 primary lung adenocarcinomas and compared them with the mutation status of the four key molecules (EGFR, ERBB2, KRAS and BRAF) in the EGFR/KRAS/BRAF pathway. Unsupervised classification revealed two subtypes (the bronchial type and the alveolar type) of lung adenocarcinoma. Mutually exclusive somatic mutations of the epidermal growth factor receptor (EGFR) gene (36/86, 41.8%), K-ras gene (11/86, 12.8%) and BRAF gene (1/86, 1.1%) were detected. KRAS mutations were observed significantly frequently in bronchial-type tumors, whereas the frequencies of EGFR mutations were similar in both the alveolar and bronchial types. Twenty-seven genes showed increased expression in EGFR-mutated tumors and these included molecules that function in the EGFR/KRAS/BRAF pathway (EGFR, AKT1 and BCR). In particular, expression of BCR, which is required for EGFR protein degradation, was induced by EGF stimulation, suggesting a negative feedback loop in lung cancer. A subgroup of the alveolar type tumors showed significantly better prognosis than other tumors. Integrated analysis of genetic and gene expression profiling aimed to delineate inherent oncogenic pathways in cancer will be valuable not only for the understanding of molecular pathogenesis, but also for discovering novel biomarkers and predicting clinical outcome.

Distinctive evaluation of nonmucinous and mucinous subtypes of bronchioloalveolar carcinomas in EGFR and K-ras gene-mutation analyses for Japanese lung adenocarcinomas: confirmation of the correlations with histologic subtypes and gene mutations

Although adenocarcinomas of the lung are associated with epidermal growth factor receptor (EGFR) gene mutations and sensitivity to EGFR tyrosine kinase inhibitors, it remains unclear whether bronchioloalveolar carcinoma (BAC) components and/or subtypes affect these associations. We aimed to clarify correlations between EGFR gene mutations and BAC components and to establish the histologic features as reliable predictors for the mutations. We examined 141 non-small cell lung cancers (NSCLCs), including 118 adenocarcinomas, for mutations in exons 19 and 21 of the EGFR gene together with mutations in codon 12 of the K-ras gene using loop-hybrid mobility shift assays, a highly sensitive polymerase chain reaction-based method. Adenocarcinomas were subdivided into subtypes with a nonmucinous or mucinous BAC component and those without BAC components. In NSCLCs, EGFR mutations were detected in 75 cases (53.2%) and were significantly associated with adenocarcinoma, female sex, and never smoking. Among adenocarcinomas, nonmucinous and mucinous BAC components were significantly associated with EGFR and K-ras gene mutations, respectively. Because EGFR mutations were detected even in most pure nonmucinous BACs, ie, lung adenocarcinoma in situ, EGFR mutation is considered a critical event in the pathogenesis of nonmucinous BAC tumors.

Clonality and heterogeneity of pulmonary blastoma from the viewpoint of genetic alterations: A case report

Biphasic pulmonary blastoma is a rare lung tumor with epithelial and mesenchymal components. Genetic alterations in this tumor are largely unknown, except for the presence of beta-catenin and p53 mutations and the absence of KRAS mutation. To understand the molecular process of histogenesis of this tumor, a whole genome allelic imbalance (AI) scanning using a high-resolution single nucleotide polymorphism array as well as mutational analysis of the p53, EGFR, KRAS and beta-catenin genes were performed against the epithelial and mesenchymal components in the primary tumor and a metastatic tumor in a case of pulmonary blastoma. AI at chromosome regions 14q24-q32 and 17p11-p13 and beta-catenin mutation were commonly detected in all tumors. On the other hand, AI at chromosome regions 3p11-p14 and 9p21-p24 and p53 mutation were detected only in the mesenchymal component in the primary tumor but not in the epithelial component in the primary tumor and the brain metastasis. Likewise, AI at chromosome regions 6p24-p25 and 6q14-q27 was detected in the epithelial component in the primary tumor and the brain metastasis but not in the mesenchymal component in the primary tumor. Furthermore, the genetic alterations detected in the metastatic tumor were completely the same as those in the epithelial component in the primary tumor, indicating that a tumor cell(s) in the epithelial component in the primary tumor selectively metastasized to the brain. These results indicate that this biphasic tumor is of monoclonal origin and the phenotypic heterogeneity of the tumor is due to the differences in the accumulated genetic alterations in each component of the tumor.

Controversy about Small Peripheral Lung Adenocarcinomas: How Should We Manage Them?

In recent years, the clinical use of high-resolution computed tomography has greatly advanced the diagnosis of small lesions of the peripheral lung. Such small lesions are often associated with ground-glass opacity in computed tomography findings. The noninvasive bronchioloalveolar carcinoma component with a replacement growth pattern of alveolar lining cells manifests as ground-glass opacity. Bronchioloalveolar carcinoma is classified as a subset of lung adenocarcinoma, but has a distinct clinical presentation, tumor biology, and favorable prognosis. Most small peripheral lung lesions including bronchioloalveolar carcinoma putatively originate from the peripheral airway epithelium, in which the epidermal growth factor receptor gene is frequently mutated. As with other subsets of non-small cell lung cancer, surgical resection is a potentially curative treatment. For the ground-glass opacity type of tiny lesions, particularly those less than 1 cm in their greatest dimension, the question has been raised whether lobectomy is really needed. Although several authors in Japan suggest the suitability of limited resection including segmentectomy and wedge resection without any nodal dissections for these small lung adenocarcinomas, this procedure should be validated in future clinical trials.

Epidermal growth factor receptor mutations in lung cancers

In 2004, two groups reported somatic mutations in the gene for the epidermal growth factor receptor (EGFR) in patients with non-small cell lung cancer (NSCLC), which were highly correlated with the clinical response to the anticancer drug, gefitinib. Since then, a tremendous amount of knowledge has accumulated, and sheds light on significant oncological properties as well as the clinical relevance of this mutation, which could be applicable to other malignancies. The EGFR mutations are distributed throughout the kinase domain, but a deletion in exon 19 and the point mutation L858R in exon 21 account for approximately 90%, which confer a greater response to gefitinib treatment, compared with other types of EGFR mutations. These EGFR mutations in the tyrosine kinase domain are seldom acquired in cancers of the other organs and the mutations preferentially involve a subset of lung cancers, which are clinicopathologically characterized by female sex, non-smoking, adenocarcinoma histology and East Asian ethnicity. In Japan, the EGFR mutations are detected in approximately 30% of overall NSCLC and approximately 40% of surgically resected adenocarcinomas. The morphological features of adenocarcinomas harboring the mutations were reported to be frequent in those with bronchioloalveolar features, but it is suggested that the cellular lineage of the putative original cells of the cancers refines the subset more clearly. In the present study the current knowledge of EGFR mutations is reviewed, insights from which raise many further questions, and thus suggest new directions for future research.

Molecular predictors of response to epidermal growth factor receptor antagonists in non-small-cell lung cancer

In the last 5 years the epidermal growth factor receptor (EGFR) has emerged as one of the most important targets for drug development in oncology. Monoclonal antibodies targeting the external domain of EGFR have been shown to have clinical benefit in colorectal and head and neck cancer when combined with chemotherapy and/or radiation. Small molecules that inhibit the tyrosine kinase (TK) domain of EGFR have become critical new weapons in the treatment of non-small-cell lung cancer (NSCLC). The discovery that mutations in the TK domain are associated with dramatic and sustained responses to EGFR TK inhibitors (TKIs) has allowed the design of trials to test these agents as potential first-line therapies and has provided a fascinating window into the future of genotype-directed targeted therapy. Recent advances in understanding the biologic basis of acquired resistance to these agents have great potential to improve the clinical effectiveness of this class of drugs. This review summarizes the biology of EGFR in NSCLC, the clinical and molecular predictors of benefit from treatment with EGFR TKIs, the use of patient-specific molecular profiling, and future directions of clinical and basic scientific research.

Identical epidermal growth factor receptor mutations in adenocarcinomatous and squamous cell carcinomatous components of adenosquamous carcinoma of the lung

BACKGROUND

Adenosquamous carcinoma of the lung is composed of adenocarcinomatous and squamous cell carcinomatous components. The epidermal growth factor receptor (EGFR) mutations occur mostly in adenocarcinomas and rarely in squamous cell carcinoma of lung. Attempts to investigate the EGFR mutation status in each component of adenosquamous carcinoma and to characterize the patients according to mutation status may help to understand the histogenesis of adenosquamous carcinoma.

METHODS

The mutation status of EGFR kinase domain from exon 18 to 21 was investigated in 25 Korean patients with adenosquamous carcinoma by polymerase chain reaction-single strand conformation polymorphism using the tissues of each component from the adenosquamous carcinoma tumor. Clinicopathologic characteristics of the patients according to the status of EGFR mutations were compared.

RESULTS

EGFR mutations were identified in 11 (44%) patients: 9 mutations were in exon 19, 1 in exon 20, and 1 in exon 21. EGFR mutations were significantly more frequent (P = .005) in women (n = 8, 80%) than men (n = 3, 20%). Never-smokers (n = 8, 62%) had EGFR mutations more commonly than smokers (n = 3, 25%; P = .111). Identical EGFR mutations in both components of adenosquamous carcinoma were confirmed by nucleotide sequencing.

CONCLUSIONS

The frequency of EGFR mutation and clinicopathologic characteristics of the EGFR mutants in adenosquamous carcinoma are similar to those of Asian patients with adenocarcinomas. Identical EGFR mutations in both components suggest the possibility of monoclonality in the histogenesis of adenosquamous carcinoma.

Risk factors differ for non-small-cell lung cancers with and without EGFR mutation: assessment of smoking and sex by a case-control study in Japanese

The present study aimed to assess the impact of smoking and sex for the risk of non-small-cell lung cancer (NSCLC) with or without epidermal growth factor receptor (EGFR) mutation. We conducted a case-control study using 152 patients with EGFR-mutated (EGFRmut) NSCLC, 283 with EGFR-wild-type (EGFRwt) NSCLC and 2175 age- and sex-frequency-matched controls. Smoking was a significant risk factor for EGFRwt NSCLC (odds ratio [OR] for ever-smokers, 4.05; 95% confidence interval [CI], 2.79-5.88) but not for EGFRmut NSCLC (OR, 0.73; CI, 0.46-1.14). Sex did not affect this association. The association was observed consistently with other smoking-related parameters including pack-years. Sex was the sole risk factor for EGFRmut NSCLC (OR for women relative to men, 2.19; CI, 1.41-3.39) and there was no significant interaction between women and smoking. In contrast, sex, smoking and their interaction were significant in EGFRwt NSCLC. The impact of sex on EGFR mutation status was assessed by several indicators of reproductive history among women. Total fertile years showed a significant positive association with EGFRmut NSCLC but not with EGFRwt NSCLC. Other indicators showed similar trends and this result may partly explain the sexual difference in the acquisition of EGFR mutation. In conclusion, our case-control study clearly demonstrated that the impacts of smoking and sex on the risk of EGFRmut NSCLC are different from those for EGFRwt NSCLC. Further epidemiological evaluation is warranted.

Epidermal growth factor receptor abnormalities in lung cancer. Pathogenetic and clinical implications

The discovery that mutation of the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) gene occurs in a subset of lung cancers and predicts for sensitivity to tyrosine kinase inhibitors has generated enormous interest and immediately led to intense basic, translational, and clinical research in many laboratories around the globe. All these findings have led to the identification of a subset of lung cancers with relatively distinct molecular, pathologic, and clinical features that demonstrate response to targeted therapy. Currently, the best marker to predict response and better survival for EGFR tyrosine kinase inhibitors, such as EGFR mutation, gene increased copy number, and protein immunohistochemical expression, is still controversial. Importantly, the findings of EGFR abnormalities in lung cancer have supported the notion that different molecular mechanisms and pathways are involved in the pathogenesis of lung cancer arising in never and ever smokers.

Epidermal growth factor receptor mutation in lung cancer are linked to bronchioloalveolar differentiation

In lung cancer, an association was made between drastic clinical response to epidermal growth factor receptor (EGFR) inhibitors and the presence of somatic mutations within the tyrosine kinase domain of the EGFR. In some cases, patients with partial response or disease stabilization do not always have EGFR-mutated tumors. To go further in the characterization of the EGF pathway, we screened EGFR, ERBB2, ERBB3, KRAS, BRAF, and PIK3CA for mutations in 2 groups of White patients with nonsmall cell lung cancer (45 cancers from women and 46 cancers from men). Associations between TP53 mutations, clinicopathologic parameters, and EGF pathway molecular alterations were analyzed. All mutations were exclusive and essentially found in EGFR and KRAS. We demonstrated that EGFR mutations were linked to female sex, absence of smoking, late age at diagnosis, and adenocarcinoma (ADC) with bronchioloalveolar (BAC) features. Moreover, in invasive ADC with BAC component, microdissection assays showed that mutations were retrieved in both tumor subtypes suggesting that EGFR mutations appear early in lung carcinogenesis. On the contrary, KRAS mutations correlated with smoking, younger age at diagnosis, and ADC subtype regardless of BAC differentiation. These results suggest the existence of distinct carcinogenesis pathways both leading to disruption of EGF regulation and targeted either by tobacco carcinogens or by unidentified toxic. The identification of BAC features in ADC helps clustering patients that are more likely to fit the EGFR-mutated group.

Biological and clinical implications of EGFR mutations in lung cancer

BACKGROUND

Patients with non-small-cell lung cancer sometimes show a dramatic clinical response to gefitinib or erlotinib, small-molecule tyrosine kinase inhibitors (TKI) specific for the epidermal growth factor receptor (EGFR). However, until April 2004, it was unclear how to identify patients who would benefit from these drugs. Then, two groups from Boston reported that EGFR gene mutations in the kinase domain are strongly associated with gefitinib sensitivity. EGFR mutations are more frequent in Asians, females, nonsmokers, and adenocarcinomas than in their counterparts. These populations precisely coincide with those populations with higher response rates to TKIs. We and others subsequently confirmed and extended these findings.

METHODS

We reviewed recent literatures on EGFR mutations and EGFR-TKIs. We discuss topics including the molecular epidemiology and biology of EGFR mutations in relation to EGFR-TKIs, the controversy about whether EGFR mutations account for all the clinical activity of EGFR-TKIs, and the mechanisms of acquired resistance to gefitinib or erlotinib.

RESULTS

The discovery of EGFR mutations has great biologic and clinical implications in lung cancer. However, all but one phase III trials have so far failed to show a survival advantage of the treatment arm involving EGFR-TKIs.

CONCLUSION

It would be possible to individualize EGFR-TKI treatment of lung cancer by selecting patients according to EGFR mutational status and other biomarkers.

Mutation profile of EGFR gene detected by denaturing high-performance liquid chromatography in Japanese lung cancer patients

PURPOSE

EGFR mutations in lung cancer increase sensitivity to an EGFR tyrosine kinase inhibitor, gefitinib. Mutation analysis of EGFR is essential for prediction of gefitinib response and avoidance of the coincidental severe side effects for the unresponsive population. The purpose of the present study is to apply DHPLC as a screening system of detection of EGFR mutations for large scaled population.

METHODS

EGFR mutations were detected by both DHPLC procedure and direct sequencing using lung cancer tissue samples obtained from 97 patients (81 surgical specimens and 16 pleural effusions of non-resectable lung cancer patients).

RESULTS

DHPLC analysis detected EGFR mutations in 5 h as opposed to 18 h by direct sequencing for ten samples, and it costs eightfold more expensive by direct sequencing than DHPLC. In addition, DHPLC analysis was sixfold more sensitive than sequencing analysis for detection of the point mutation of exon 21, L858R. Using this system, EGFR mutations in exons 18, 19 and 21 were found in 34 of 97 patients (36%). Thirteen of the 15 patients with exon 21 mutations (87%) were female non-smokers, who were diagnosed with adenocarcinomas with the feature of BAC. Eight of the 18 patients with exon 19 mutations (44%) were 7 male and 1 female current or former smokers, and BAC feature was observed in 61% (8/18).

CONCLUSION

DHPLC analysis for screening followed by sequencing analysis appears to be more sensitive and accurate, as well as easier and faster. In addition, these results suggest different mutagenesis and carcinogenesis pathways for mutations.

Molecular context of the EGFR mutations: evidence for the activation of mTOR/S6K signaling

PURPOSE

Activating somatic mutations in the epidermal growth factor receptor (EGFR) gene are present in a small subset of lung adenocarcinomas. These mutations cluster in specific regions and confer sensitivity to inhibitors of the tyrosine kinase activity of EGFR. To further determine the genetic and molecular characteristics of tumors carrying EGFR gene mutations, we investigated the EGFR gene status in lung adenocarcinomas and evaluated its association with specific characteristics of the patients and tumors, such as mutations at KRAS and p53, EGFR and ErbB2 gene amplification, levels of EGFR and HER2 proteins, and levels of downstream effectors of EGFR, such as phospho-extracellular signal-regulated kinase and phospho-S6 proteins.

EXPERIMENTAL DESIGN

The mutational status of EGFR was determined by direct sequencing in 86 primary lung adenocarcinomas and 12 lung cancer cell lines, and was correlated with a number of variables relating to the tumor and patient. A tissue microarray containing 37 lung tumors was constructed to determine, by fluorescence in situ hybridization analysis, the number of copies of EGFR and ErbB2 genes and, by immunohistochemistry, the levels of EGFR, HER2, phospho-ERK, and phospho-S6 proteins.

RESULTS

EGFR gene mutations were identified in 13% of the primary tumors. The type and clustering of the mutations were identical to those previously reported. Amplification of the EGFR occurred in 14% of the tumors and could arise in tumors with EGFR mutations. Interestingly, mTOR activation, as measured indirectly by augmented levels of phospho-S6 protein, was more frequent in tumors with gene alterations in either EGFR or KRAS (P = 0.00005; Fisher's exact test) than in their wild-type counterparts.

CONCLUSIONS

Our data agree with the accumulation of EGFR mutations in a subset of patients with lung cancer. Moreover, we report EGFR gene amplification in EGFR-mutant tumors and a positive correlation between EGFR or KRAS alterations and activation of mTOR signaling.

Expression profile-defined classification of lung adenocarcinoma shows close relationship with underlying major genetic changes and clinicopathologic behaviors

PURPOSE

This study was conducted to gain insight into the relationship between expression profiles and underlying genetic changes, which are known to be important for the pathogenesis of lung cancers.

METHODS

Expression profiles of 18,175 unique genes and three major targets for genetic changes, p53, epidermal growth factor receptor (EGFR), and K-ras, were investigated in 149 patients with non-small-cell lung cancer, including 90 patients with adenocarcinoma to determine their relationships with various clinicopathologic features and Gene Ontology (GO) terms.

RESULTS

This study successfully established a basis for expression profile-defined classification, which can classify adenocarcinomas into two major types, terminal respiratory unit (TRU) type and non-TRU type. Our GO term-based identifier of particular biologic processes, molecular functions, and cellular compartments clearly showed characteristic retention of normal peripheral lung features in TRU type, in sharp contrast to the significant association of non-TRU type with cell cycling and proliferation-related features. While significantly higher frequency of EGFR mutation was observed in TRU type, we found that the presence of EGFR mutations was a significant predictor of shorter postoperative survival for TRU type, independent of disease stage. We were also able to identify a set of genes in vivo with significant upregulation in the presence of EGFR mutations.

CONCLUSION

This study has shed light on heterogeneity in lung cancers, especially in adenocarcinomas, by establishing a molecularly, genetically, and clinically relevant, expression profile-defined classification. Future studies using independent patient cohorts are warranted to confirm the prognostic significance of EGFR mutations in TRU-type adenocarcinoma.

Epidermal growth factor receptor gene mutation defines distinct subsets among small adenocarcinomas of the lung

Epidermal growth factor receptor (EGFR) gene mutations are frequently detected in lung cancer, especially in adenocarcinoma, in females, and non-smoking patients. EGFR mutations are closely associated with clinical response to EGFR tyrosine kinase inhibitor. Bronchioloalveolar carcinoma (BAC) appearance is a good predictor of response to this agent. Noguchi et al. subdivided small peripheral adenocarcinoma of the lung into two groups. One group was characterized with tumor cell growth replacing the normal alveolar cells with varying degree of fibrosis (types A-C), and the other shows non-replacing and destructive growth (types D-F). Using probes for the 13 mutations which have been previously described, we have genotyped the EGFR gene status in surgically resected atypical adenomatous hyperplasias (AAH) and small peripheral adenocarcinomas up to 2 cm in diameter using TaqMan PCR assay. In 95 small-sized adenocarcinomas, the EGFR mutations were detected in 37 patients (38.9%), and no mutations were found in five AAHs. In small peripheral adenocarcinomas, EGFR mutations were found 47.1% of types A, B, or C adenocarcinomas; it was less frequent (16%) in Noguchi's types D, E or F adenocarcinomas. These results suggest that type D, F adenocarcinomas are not derived from the less malignant types A-C adenocarcinomas; rather, they have arisen de novo by distinct mechanisms. Although types A and B adenocarcinomas are almost 100% cured by surgery, some type C adenocarcinoma show lymph node metastasis and relapse. EGFR mutation analysis may help identify patients who will respond to treatment with tyrosine kinase inhibitors, e.g., gefitinib.

A correlation between EGFR gene mutation status and bronchioloalveolar carcinoma features in Japanese patients with adenocarcinoma

BACKGROUND

The presence of epidermal growth factor receptor (EGFR) mutations in gefitinib-naive lung cancer patients has been reported to be higher in females, in non-smokers, in Japanese, and in adenocarcinoma patients, especially in bronchioloalveolar carcinoma (BAC). To further investigate the prevalence of EGFR mutations in relation to pathological factors, we evaluated EGFR mutations in series of Japanese adenocarcinoma patients who had never been treated with gefitinib.

METHODS

In the previous studies, we examined mutation status in the tyrosine kinase domain of EGFR, exon18 through exon21, in 112 primary lung adenocarcinoma samples. Using these data, adenocarcinomas were histologically classified according to the presence or absence of bronchioloalveolar components.

RESULTS

Among 112 patients, 48 had adenocarcinoma with BAC components. Those with adenocarcinomas with BAC components had higher frequency of EGFR mutation (28/48, 58%) than those with non-BAC adenocarcinoma (24/64, 37%, P = 0.036). Male patients had the same trend; 12/23 (52%) male patients with adenocarcinoma with BAC components and 10/47 (21%) of those with non-BAC adenocarcinoma had EGFR mutation (P = 0.0135) but there was no correlation between the EGFR mutation status and with/without BAC components in 42 female patients (P = 0.30). Among 11 male non-smokers, patients with adenocarcinoma with BAC components had a tendency to have EGFR mutation more frequently than those with non-BAC adenocarcinoma (P = 0.061). In clear contrast, the frequency of EGFR mutation did not differ significantly between male smoker patients with adenocarcinoma with BAC components and those with non-BAC. Among patients with adenocarcinoma with BAC components, those with adenocarcinoma with EGFR gene mutation had a significantly better 5 year survival than those with adenocarcinoma with wild-type (85.7 versus 46.0%, P = 0.0017).

CONCLUSIONS

Adenocarcinomas with BAC components in male non-smokers seem to predict the presence of EGFR mutation. Half of female adenocarcinoma patients with EGFR mutation exhibit adenocarcinomas with non-BAC suggesting a different behavior from those in males. The prognosis of patients with adenocarcinoma with BAC components with EGFR gene mutation is predicted to be better than that of patients with adenocarcinoma with BAC components with wild-type EGFR gene.

Somatic mutations of epidermal growth factor receptor signaling pathway in lung cancers

Somatic mutations in the tyrosine kinase (TK) domain of the epidermal growth factor receptor (EGFR) gene in lung cancers have generated enormous interest, because they predict for sensitivity to TK inhibitors (TKIs). While mutational status is of great importance in determining response to TKIs, it is not the sole factor, and evidence is accumulating that EGFR gene amplification, other members of the EGFR family (HER2, HER3) and genes downstream of EGFR signaling (KRAS, BRAF), may be involved in cancer pathogenesis and the response of TKIs. EGFR mutations occur in highly selected subpopulations of lung cancer patients: adenocarcinoma histology, never-smoker status, East Asian ethnicity and female gender. The recent finding of "a resistance associated" mutation for TKIs also provides new insights into this complicated mechanism. Thus, molecular-based studies to analyze the biological functions and to assess TKI sensitivity depending on the type of mutations are required. Epidemiological studies to identify possible carcinogenic factor(s) affecting different subpopulations are also of interest. In addition, for optimal therapeutic approach a comprehensive understanding of the genes related to EGFR signaling pathway, including RAS/RAF/MAPK and PI3K-AKT pathways, are required.

FrequentEGFR mutations in noninvasive bronchioloalveolar carcinoma

Mutations of the epidermal growth factor receptor gene (EGFR) have been reported to be present in a considerable fraction of lung adenocarcinomas showing dramatic response to EGFR tyrosine kinase inhibitors. To clarify pathogenic significance of the mutations for the development of lung adenocarcinoma, we investigated stage I lung adenocarcinomas for the mutations. First, 107 cases of macrodissected stage I adenocarcinomas were examined for mutations in exons 18-21 of the EGFR gene. EGFR mutations were detected in 36 of the 107 cases (34%). In particular, among the stage I cases, the mutations were detected in 17 of 42 small-sized adenocarcinomas (<or=2 cm in diameter) (40%), including 7 of 11 noninvasive bronchioloalveolar carcinomas (BACs) (64%) and 7 of 25 invasive adenocarcinomas with BAC components (28%). Second, 26 cases of laser capture microdissected small-sized adenocarcinomas, including 9 cases in the first analysis, were examined for the mutations. Reanalysis of microdissected materials in the 9 cases identified the mutations in 2 more adenocarcinomas with BAC components. Moreover, in the analysis of the other 17 microdissected materials, EGFR mutations were detected in 7 of 12 BACs (58%) and in 3 of 5 adenocarcinomas with BAC components (60%). EGFR mutations are present frequently in BACs, and are thus likely to be a critical genetic alteration for the formation of noninvasive lung adenocarcinoma.

FrequentEGFR mutations in brain metastases of lung adenocarcinoma

Lung adenocarcinomas often metastasize to the brain, and the prognosis of patients with brain metastases is still very poor. The epidermal growth factor receptor (EGFR) gene is mutated in a considerable fraction of primary lung adenocarcinomas, in particular those with drastic response to EGFR tyrosine kinase inhibitors. The present study was designed to elucidate the prevalence of EGFR mutations in brain metastases and the timing of their occurrence during cancer progression. EGFR mutations were detected in 12 of 19 metastatic lung adenocarcinomas to the brain (63%). This frequency was higher than those in previous studies for EGFR mutations at various stages of lung adenocarcinoma in East Asia, including Japan (i.e., 20-55%). In 6 cases with EGFR mutations, the corresponding primary lung tumors were also examined for the mutations, and in all of them, the same types of EGFR mutations were detected also in the primary tumors. In 2 of them, second metastatic brain tumors in addition to the first ones were also available for analysis, and the same types of EGFR mutations were detected in both the first and second ones in both cases. These results indicate that EGFR mutations are present frequently in brain metastases and occur preceding brain metastasis. These findings will be highly informative for treatment of metastatic lung adenocarcinoma to the brain.