A mouse model for EML4-ALK-positive lung cancer

New driver mutations in non-small-cell lung cancer

Treatment decisions for patients with lung cancer have historically been based on tumour histology. Some understanding of the molecular composition of tumours has led to the development of targeted agents, for which initial findings are promising. Clearer understanding of mutations in relevant genes and their effects on cancer cell proliferation and survival, is, therefore, of substantial interest. We review current knowledge about molecular subsets in non-small-cell lung cancer that have been identified as potentially having clinical relevance to targeted therapies. Since mutations in EGFR and KRAS have been extensively reviewed elsewhere, here, we discuss subsets defined by so-called driver mutations in ALK, HER2 (also known as ERBB2), BRAF, PIK3CA, AKT1, MAP2K1, and MET. The adoption of treatment tailored according to the genetic make-up of individual tumours would involve a paradigm shift, but might lead to substantial therapeutic improvements.

Lung cancer: New biological insights and recent therapeutic advances

Approximately 1.6 million new cases of lung cancer are diagnosed each year throughout the world. In many countries, the mortality related to lung cancer continues to rise. The outcomes for patients with all stages of lung cancer have improved in recent years. The use of systemic therapy in conjunction with local therapy has led to improved cure rates in both resectable and unresectable patient groups. For patients with advanced stage disease, modest but real improvements in overall survival and quality of life have been achieved with systemic chemotherapy. A major focus of research has been the development of molecularly targeted agents and the identification of biomarkers for patient selection. Patients with non-small cell lung cancer with mutations in the epidermal growth factor receptor (EGFR) tyrosine kinase domain achieve response rates of greater than 70% and superior progression-free survival when treated with an EGFR tyrosine kinase inhibitor compared with standard chemotherapy. This has now emerged as the preferred therapeutic approach for the subset of patients with a mutation in exons 19 or 21 of the EGFR. Another promising targeted approach involves the use of an anaplastic lymphoma kinase (ALK) inhibitor in patients with a translocation involving the echinoderm microtubule-associated protein-like 4 (EML4) and -ALK genes. Finally, a paradigm shift in favor of maintenance therapy for patients with advanced stage disease has gained strength from recent data. All of these advances have been made possible by developing a greater understanding of the biology, the discovery of novel anticancer agents, and improved supportive care measures. This article reviews the major strides made in the treatment of lung cancer in the recent past.

Mind-mapping for lung cancer: towards a personalized therapeutics approach

There were over 220,000 people diagnosed with lung cancer and over 160,000 people dying of lung cancer during 2010 alone in the United States. In order to arrive at better control, prevention, diagnosis, and therapeutics for lung cancer, we must be able to personalize the approach towards the disease. Mind-mapping has existed for centuries for physicians to properly think about various "flows" of personalized medicine. We include here the epidemiology, diagnosis, histology, and treatment of lung cancer-in particular, non-small cell lung cancer. As we have new molecular signatures for lung cancer, this is further detailed. This review is not meant to be a comprehensive review, but rather its purpose is to highlight important aspects of lung cancer diagnosis, management, and personalized treatment options.

Targeting anaplastic lymphoma kinase in lung cancer

Several decades of cancer research have revealed a pivotal role for tyrosine kinases as key regulators of signaling pathways, controlling cell growth and differentiation. Deregulation of tyrosine kinase-mediated signaling occurs frequently in cancer and is believed to drive the initiation and progression of disease. Chromosomal rearrangements involving the tyrosine kinase anaplastic lymphoma kinase (ALK) occur in a variety of human malignancies including non-small cell lung cancer (NSCLC), anaplastic large cell lymphomas, and inflammatory myofibroblastic tumors. The aberrant activation of ALK signaling leads to "oncogene addiction" and marked sensitivity to ALK inhibitors such as crizotinib (PF-02341066). This review focuses on ALK rearrangements in NSCLC, starting with the discovery of the EML4-ALK fusion oncogene, and culminating in the recent validation of ALK as a therapeutic target in patients with ALK-rearranged NSCLC. Current efforts seek to expand the role of ALK kinase inhibition in lung and other cancers and to address the molecular basis for the development of resistance.

Oncogenic mutations of ALK in neuroblastoma

Neuroblastoma is one of the most common solid cancers among children. Prognosis of advanced neuroblastoma is still poor despite the recent advances in chemo/radiotherapies. In view of improving the clinical outcome of advanced neuroblastoma, it is important to identify the key molecules responsible for the pathogenesis of neuroblastoma and to develop effective drugs that target these molecules. Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase, initially identified through the analysis of a specific translocation associated with a rare subtype of non-Hodgkin's lymphoma. Recently it was demonstrated that ALK is frequently mutated in sporadic cases with advanced neuroblastoma. Moreover, germline mutations of ALK were shown to be responsible for the majority of hereditary neuroblastoma. ALK mutants found in neuroblastoma show constitutive active kinase activity and oncogenic potentials. Inhibition of ALK in neuroblastoma cell lines carrying amplified or mutated ALK alleles results in compromised downstream signaling and cell growth, indicating potential roles of small molecule ALK inhibitors in the therapeutics of neuroblastoma carrying mutated ALK kinases.

Molecular testing of solid tumors

CONTEXT

Molecular testing of solid tumors is steadily becoming a vital component of the contemporary anatomic pathologist's armamentarium. These sensitive and specific ancillary tools are useful for confirming ambiguous diagnoses suspected by light microscopy and for guiding therapeutic decisions, assessing prognosis, and monitoring patients for residual neoplastic disease after therapy.

OBJECTIVE

To review current molecular biomarkers and tumor-specific assays most useful in solid tumor testing, specifically of breast, colon, lung, thyroid, and soft tissue tumors, malignant melanoma, and tumors of unknown origin. A few upcoming molecular diagnostic assays that may become standard of care in the near future will also be discussed.

DATA SOURCES

Original research articles, review articles, and the authors' personal practice experience.

CONCLUSIONS

Molecular testing in anatomic pathology is firmly established and will continue to gain ground as the need for more specific diagnoses and new targeted therapies evolve. Knowledge of the more common and clinically relevant molecular tests available for solid tumor diagnosis and management, and their indications and limitations, is necessary if anatomic pathologists are to optimally use these tests and act as consultants for fellow clinicians directly involved in patient care.

How genetically engineered mouse tumor models provide insights into human cancers

Genetically engineered mouse models (GEMMs) of human cancer were first created nearly 30 years ago. These early transgenic models demonstrated that mouse cells could be transformed in vivo by expression of an oncogene. A new field emerged, dedicated to generating and using mouse models of human cancer to address a wide variety of questions in cancer biology. The aim of this review is to highlight the contributions of mouse models to the diagnosis and treatment of human cancers. Because of the breadth of the topic, we have selected representative examples of how GEMMs are clinically relevant rather than provided an exhaustive list of experiments. Today, as detailed here, sophisticated mouse models are being created to study many aspects of cancer biology, including but not limited to mechanisms of sensitivity and resistance to drug treatment, oncogene cooperation, early detection, and metastasis. Alternatives to GEMMs, such as chemically induced or spontaneous tumor models, are not discussed in this review.

Crizotinib for EML4-ALK positive lung adenocarcinoma: a hope for the advanced disease? Evaluation of Kwak EL, Bang YJ, Camidge DR, et al. Anaplastic lymphoma kinase inhibition in non-small-cell lung cancer. N Engl J Med 2010;363(18):1693-703

INTRODUCTION

In lung adenocarcinoma, certain mutations such as echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase (ALK) are associated with lower sensitivity to chemotherapy, when used conventionally as the first-line therapy in the advanced stage of the disease.

AREAS COVERED

This paper discusses the clinical and therapeutic importance of ALK mutations in NSCLC and the early clinical results of a Phase I study assessing crizotinib in patients with ALK mutations.

EXPERT OPINION

Abnormal ALK is evolving as an important therapeutic target in patients with more aggressive lung adenocarcinoma. Further clinical studies are needed in order to assess if crizotinib, an ALK inhibitor, is able to increase the efficacy of the conventional chemotherapy in this disease subset.

Crizotinib (PF02341066) as a ALK /MET inhibitor- Special Emphasis as a Therapeutic Drug Against Lung Cancer

There are a number of molecular abnormalities that can occur in normal cells to induce a malignant phenotype. Recently, the receptor tyrosine kinase anaplastic lymphoma kinase (ALK) has been shown to have gain-of-function when partnered with different proteins. As an example, on chromosome 2p, with inversion, there is translocation with generation of EML4-ALK tyrosine kinase in lung cancer. In a phase I trial, EML4-ALK patients were selected to determine the response to a potent small molecule tyrosine kinase inhibitor crizotinib (previously identified as PF02341066). Dramatic durable responses were observed with crizotinib at 250 mg twice a day (orally). Interestingly, crizotinib also has activity against MET receptor tyrosine kinase. We have previously shown that MET can be overexpressed, sometimes mutated, or sometimes amplified in lung cancer. Thus, this review will emphasize the characteristics of crizotinib, and detail the clinical experience.

The neuroblastoma-associated F1174L ALK mutation causes resistance to an ALK kinase inhibitor in ALK-translocated cancers

The ALK kinase inhibitor crizotinib (PF-02341066) is clinically effective in patients with ALK-translocated cancers, but its efficacy will ultimately be limited by acquired drug resistance. Here we report the identification of a secondary mutation in ALK, F1174L, as one cause of crizotinib resistance in a patient with an inflammatory myofibroblastic tumor (IMT) harboring a RANBP2-ALK translocation who progressed while on crizotinib therapy. When present in cis with an ALK translocation, this mutation (also detected in neuroblastomas) causes an increase in ALK phosphorylation, cell growth, and downstream signaling. Furthermore, the F1174L mutation inhibits crizotinib-mediated downregulation of ALK signaling and blocks apoptosis in RANBP2-ALK Ba/F3 cells. A chemically distinct ALK inhibitor, TAE684, and the HSP90 inhibitor 17-AAG are both effective in models harboring the F1174L ALK mutation. Our findings highlight the importance of studying drug resistance mechanisms in order to develop effective clinical treatments for patients with ALK-translocated cancers.

ALK inhibition for non-small cell lung cancer: from discovery to therapy in record time

It was only 3 years ago that an acquired translocation of EML4 with ALK leading to the expression of an EML4-ALK oncoprotein in non-small cell lung cancer (NSCLC) was reported. Tumor cells expressing EML4-ALK are "addicted" to its continued function. Now, crizotinib, an oral ALK inhibitor, is demonstrated to provide dramatic clinical benefit with little toxicity in patients having such advanced NSCLC, and a mechanism of clinical resistance to crizotinib is identified. Such therapy "targeted" at oncogenic proteins provides "personalized" medicine and prompts genome-wide mutation analysis of human tumors to find other therapeutic targets.

Molecular testing in lung cancer: the time is now

In the past few years, we have witnessed a revolution in the molecular understanding of non-small cell lung cancer. Major progress has also been made in the clinic, with the introduction of EGFR-targeted and anti-angiogenic therapies. These advances have led to the development of a multitude of commercially available prognostic and predictive biomarkers. In particular, EGFR mutation and EML4/ALK testing have reached clinical validation and are incorporated into current treatment paradigms. This overview will present the scientific background of the biology of the relevant biomarkers and the studies conducted for their clinical validation. The technical challenges and shortcomings of these assays are also discussed. Furthermore, ongoing biomarker-driven clinical studies and the appropriate clinical use of available tests will be reviewed to assist the clinician with the proper incorporation of molecular testing into the routine care of patients with non-small cell lung cancer.

The role of mechanistic factors in promoting chromosomal translocations found in lymphoid and other cancers

Recurrent chromosomal abnormalities, especially chromosomal translocations, are strongly associated with certain subtypes of leukemia, lymphoma and solid tumors. The appearance of particular translocations or associated genomic alterations can be important indicators of disease prognosis, and in some cases, certain translocations may indicate appropriate therapy protocols. To date, most of our knowledge about chromosomal translocations has derived from characterization of the highly selected recurrent translocations found in certain cancers. Until recently, mechanisms that promote or suppress chromosomal translocations, in particular, those responsible for their initiation, have not been addressed. For translocations to occur, two distinct chromosomal loci must be broken, brought together (synapsed) and joined. Here, we discuss recent findings on processes and pathways that influence the initiation of chromosomal translocations, including the generation fo DNA double strand breaks (DSBs) by general factors or in the context of the Lymphocyte-specific V(D)J and IgH class-switch recombination processes. We also discuss the role of spatial proximity of DSBs in the interphase nucleus with respect to how DSBs on different chromosomes are justaposed for joining. In addition, we discuss the DNA DSB response and its role in recognizing and tethering chromosomal DSBs to prevent translocations, as well as potential roles of the classical and alternative DSB end-joining pathways in suppressing or promoting translocations. Finally, we discuss the potential roles of long range regulatory elements, such as the 3'IgH enhancer complex, in promoting the expression of certain translocations that are frequent in lymphomas and, thereby, contributing to their frequent appearance in tumors.

Frequent ALK rearrangement and TTF-1/p63 co-expression in lung adenocarcinoma with signet-ring cell component

Primary adenocarcinoma with signet-ring cell component (Ad-SRCC) of the lung has been well characterized clinicopathologically and histologically, but their genetics has rarely been investigated. A recent report suggesting an association between Ad-SRCC and EML4-ALK fusion prompted us to undertake a histological, immunohistochemical, and molecular analysis of 10 cases of primary Ad-SRCC identified out of 699 lung adenocarcinomas (1.4%). Most of the Ad-SRCCs showed characteristic architectural as well as cytological features including cohesive clustering of signet-ring cells, a solid/acinar growth pattern, and alveolar filling at the tumor periphery. Diffuse co-expression of TTF-1 and p63 was observed in half of the Ad-SRCCs, and this immunoprofile has not been recognized previously. Four Ad-SRCCs (40%) harbored ALK translocations detected by reverse-transcriptase polymerase chain reaction, fluorescence in situ hybridization, and immunohistochemistry. One new EML4-ALK fusion variant was identified. One ALK-rearranged tumor showed focal squamous differentiation. None of the present Ad-SRCCs had EGFR or KRAS mutations, regardless of ALK status. This study successfully utilized tumor histology alone to identify a subset of adenocarcinomas showing a high rate of ALK translocation. The characteristic histology, immunoprofile, frequent ALK translocation, and total lack of EGFR or KRAS mutations, may suggest that Ad-SRCC forms a histologically/molecularly coherent subgroup of adenocarcinoma.

EML4-ALK mutations in lung cancer that confer resistance to ALK inhibitors

The EML4 (echinoderm microtubule-associated protein-like 4)-ALK (anaplastic lymphoma kinase) fusion-type tyrosine kinase is an oncoprotein found in 4 to 5% of non-small-cell lung cancers, and clinical trials of specific inhibitors of ALK for the treatment of such tumors are currently under way. Here, we report the discovery of two secondary mutations within the kinase domain of EML4-ALK in tumor cells isolated from a patient during the relapse phase of treatment with an ALK inhibitor. Each mutation developed independently in subclones of the tumor and conferred marked resistance to two different ALK inhibitors. (Funded by the Ministry of Health, Labor, and Welfare of Japan, and others.).

New tricks from an old oncogene: gene fusion and copy number alterations of MYB in human cancer

MYB is a leucine zipper transcription factor that is essential for hematopoesis and for renewal of colonic crypts. There is also ample evidence showing that MYB is leukemogenic in several animal species. However, it was not until recently that clear evidence was presented showing that MYB actually is an oncogene rearranged in human cancer. In a recent study, a novel mechanism of activation of MYB involving gene fusion was identified in carcinomas of the breast and head and neck. A t(6;9) translocation was shown to generate fusions between MYB and the transcription factor gene NFIB. The fusions consistently result in loss of the 3'-end of MYB, including several highly conserved target sites for microRNAs that negatively regulate MYB expression. Deletion of these target sites may disrupt the repression of MYB, leading to overexpression of MYB-NFIB transcripts and protein and to transcriptional activation of critical MYB target genes associated with apoptosis, cell cycle control, cell growth/angiogenesis and cell adhesion. This study, together with previous and recent data showing rearrangements and copy number alterations of the MYB locus in T-cell leukemia and certain solid tumors, will be the main focus of this review.

Fusion of EML4 and ALK is associated with development of lung adenocarcinomas lacking EGFR and KRAS mutations and is correlated with ALK expression

Background

The anaplastic lymphoma kinase (ALK) gene is frequently involved in translocations that lead to gene fusions in a variety of human malignancies, including lymphoma and lung cancer. Fusion partners of ALK include NPM, EML4, TPM3, ATIC, TFG, CARS, and CLTC. Characterization of ALK fusion patterns and their resulting clinicopathological profiles could be of great benefit in better understanding the biology of lung cancer.

Results

RACE-coupled PCR sequencing was used to assess ALK fusions in a cohort of 103 non-small cell lung carcinoma (NSCLC) patients. Within this cohort, the EML4-ALK fusion gene was identified in 12 tumors (11.6%). Further analysis revealed that EML4-ALK was present at a frequency of 16.13% (10/62) in patients with adenocarcinomas, 19.23% (10/52) in never-smokers, and 42.80% (9/21) in patients with adenocarcinomas lacking EGFR and KRAS mutations. The EML4-ALK fusion was associated with non-smokers (P = 0.03), younger age of onset (P = 0.03), and adenocarcinomas without EGFR/KRAS mutations (P = 0.04). A trend towards improved survival was observed for patients with the EML4-ALK fusion, although it was not statistically significant (P = 0.20). Concurrent deletion in EGFR exon 19 and fusion of EML4-ALK was identified for the first time in a Chinese female patient with an adenocarcinoma. Analysis of ALK expression revealed that ALK mRNA levels were higher in tumors positive for the EML-ALK fusion than in negative tumors (normalized intensity of 21.99 vs. 0.45, respectively; P = 0.0018). However, expression of EML4 did not differ between the groups.

Conclusions

The EML4-ALK fusion gene was present at a high frequency in Chinese NSCLC patients, particularly in those with adenocarcinomas lacking EGFR/KRAS mutations. The EML4-ALK fusion appears to be tightly associated with ALK mRNA expression levels. RACE-coupled PCR sequencing is a highly sensitive method that could be used clinically for the identification of EML4-ALK-positive patients.

Clinicopathologic features of non-small-cell lung cancer with EML4-ALK fusion gene

BACKGROUND

A fusion gene between echinoderm microtubule-associated protein-like 4 (EML4) and the anaplastic lymphoma kinase (ALK) has recently been identified in nonsmall-cell lung cancers (NSCLCs). We screened for EML4-ALK fusion genes and examined the clinicopathological and genetic characteristics of fusion-harboring NSCLC tumors.

METHODS

We examined 313 NSCLC samples from patients who underwent resection at our hospital between May 2001 and July 2005. We screened for the fusion genes using reverse-transcription polymerase chain reaction (RT-PCR) assay and confirmed the results with direct sequencing. We also examined mutations in the epidermal growth factor receptor (EGFR), KRAS, and ERBB2 genes.

RESULTS

Five EML4-ALK fusion genes were detected (four from 111 female samples and one from 202 male samples; 1.6% overall). All five genes were found in adenocarcinomas and accounted for 2.4% of the 211 adenocarcinoma samples. One EML4-ALK fusion was variant 1, and two were variant 3. In addition, we also found two new fusion variants. Patients with fusion-positive tumors were nonsmokers or light smokers. Among the 211 adenocarcinomas, mutations in EGFR, KRAS, and ERBB2 were detected in 105, 29, and 7 tumors, respectively. Interestingly, all of the fusion-positive NSCLCs had no mutations within these genes.

CONCLUSIONS

EML4-ALK fusion genes were observed predominantly in adenocarcinomas, in female or nonsmoking populations. Additionally, the EML4-ALK fusions were mutually exclusive with mutations in the EGFR, KRAS, and ERBB2 genes.

The emerging pathogenic and therapeutic importance of the anaplastic lymphoma kinase gene

The anaplastic lymphoma kinase gene (ALK) is a gene on chromosome 2p23 that has expression restricted to the brain, testis and small intestine but is not expressed in normal lymphoid tissue. It has similarity to the insulin receptor subfamily of kinases and is emerging as having increased pathologic and potential therapeutic importance in malignant disease. This gene was originally established as being implicated in the pathogenesis of rare diseases including inflammatory myofibroblastic tumour (IMT) and ALK-positive anaplastic large cell lymphoma, which is a subtype of non-Hodgkin's lymphoma. Recently the number of diseases in which ALK is implicated in their pathogenesis has increased. In 2007, an inversion of chromosome 2 involving ALK and a fusion partner gene in a subset of non-small cell lung cancer was discovered. In 2008, publications emerged implicating ALK in familial and sporadic cases of neuroblastoma, a childhood cancer of the sympatho-adrenal system. Chromosomal abnormalities involving ALK are translocations, amplifications or mutations. Chromosomal translocations are the longest recognised ALK genetic abnormality. When translocations occur a fusion gene is created between ALK and a gene partner. This has been described in ALK-positive anaplastic large cell lymphoma in which ALK is fused to NPM (nucleolar protein gene) and in non-small cell lung cancer where ALK is fused to EML4 (Echinoderm microtubule-associated protein 4). The most frequently described partner genes in inflammatory myofibroblastic tumour are tropomyosin 3/4 (TMP3/4), however in IMTs a diversity of ALK fusion partners have been found, with the ability to homodimerise a common characteristic. Point mutations and amplification of the ALK gene occur in the childhood cancer neuroblastoma. Therapeutic targeting of ALK fusion genes using tyrosine kinase inhibition, vaccination using an ALK specific antigen and treatment using viral vectors for RNAi are emerging potential therapeutic possibilities.

The biology and treatment of EML4-ALK non-small cell lung cancer

The fusion between echinoderm microtubule-associated protein-like 4 (EML4) and anaplastic lymphoma kinase (ALK) has recently been identified in a subset of non-small cell lung cancers (NSCLCs). EML4-ALK is most often detected in never smokers with lung cancer and has unique pathologic features. EML4-ALK is oncogenic both in vitro and in vivo and ALK kinase inhibitors are quite effective in pre-clinical model systems. More recently ALK inhibitors have entered clinical development and remarkably clinical efficacy has been observed in NSCLC patients harbouring EML4-ALK translocations. This review will focus on the biology, clinical characteristics, diagnosis and treatment of EML4-ALK NSCLC.

ALK gene rearrangements: a new therapeutic target in a molecularly defined subset of non-small cell lung cancer

Transforming rearrangements of the ALK (anaplastic lymphoma kinase) gene have recently been described in non-small cell lung cancer (NSCLC). The most common rearrangement arises from an inversion in the short arm of chromosome 2 that creates a fusion between the 5' portion of the EML4 (echinoderm microtubule-associated protein-like 4) gene and the 3' portion of the ALK gene. At least seven ALK gene rearrangement variants have been described involving different EML4-ALK breakpoints or rarely other non-EML4 fusion partners. ALK rearrangements may be readily identified in tumor tissue by reverse transcription-polymerase chain reaction or fluorescent in situ hybridization. Although ALK gene rearrangements affect only about 4% of all lung cancers, they are more frequent in adenocarcinomas, in never or light smokers, and seem almost mutually exclusive with activating EGFR or KRAS mutations. Promising results seen in patients with NSCLC containing fluorescent in situ hybridization-detected ALK rearrangements treated on a phase I study with PF02341066, an oral ALK inhibitor, indicate that ALK represents a new therapeutic target in this molecularly defined subset of NSCLC.

EML4-ALK fusion transcripts in immunohistochemically ALK-positive non-small cell lung carcinomas

EML4-ALK fusion transcripts have been found in a subset of non-small cell lung carcinomas (NSCLCs); however, their protein expression status has not yet been fully elucidated. In this study we investigated ALK protein expression in 302 NSCLCs and 291 gastric carcinomas by means of immunohistochemical analysis. Twelve (4.0%) NSCLCs, but none of the gastric carcinomas, were found to be positive for ALK. The ALK signal was detected in the cytoplasm of cancer cells. Subsequent RNA analysis of 10 RNA-available, immunohistochemically ALK-positive tumors revealed that three tumors had EML4-ALK variant 1, three tumors had variant 2, three tumors had variants 3a and 3b, and one tumor had a novel variant in which exon 14 of EML4 is connected to the nucleotide at position 53 of exon 20 of ALK by a 2-bp insertion. These results suggest that immunohistochemical ALK detection is a useful way to screen NSCLCs for tumors containing ALK fusions.

Targeted Therapies in Lung Cancer

An ongoing research and multiple clinical trials involve new targeted therapies and less aggressive treatment regimens that improve survival in patients with lung cancer. Targeted therapeutic agents are based on the concept of discovering genetic alterations and the signaling pathways altered in cancer and have added significantly to our armamentarium in order to prolong patient survival and minimizing drug toxicity. Among 34 molecularly targeted drugs approved by U.S. Food and Drug Administration (FDA) for treatment of various cancers since 1998 three targeted therapies have been approved for treatment of lung cancer (gefitinib in 2002, erlotinib in 2003, and bevacizumab in 2006).This review focuses on the targeted therapies in lung cancer, the molecular biomarkers that help identify patients that will benefit for these targeted therapies, describes the basic molecular biology principles and selected molecular diagnostic techniques and the pathological features correlated with molecular abnormalities in lung cancer. Lastly, new molecular abnormalities described in lung cancer that are predictive to novel promising targeted agents in various phases of clinical trials are discussed.

A novel, highly sensitive antibody allows for the routine detection of ALK-rearranged lung adenocarcinomas by standard immunohistochemistry

PURPOSE

Approximately 5% of lung adenocarcinomas harbor an EML4-ALK gene fusion and define a unique tumor group that may be responsive to targeted therapy. However ALK-rearranged lung adenocarcinomas are difficult to detect by either standard fluorescence in situ hybridization or immunohistochemistry (IHC) assays. In the present study, we used novel antibodies to compare ALK protein expression in genetically defined lung cancers and anaplastic large cell lymphomas.

EXPERIMENTAL DESIGN

We analyzed 174 tumors with one standard and two novel monoclonal antibodies recognizing the ALK protein. Immunostained tissue sections were assessed for the level of tumor-specific ALK expression by objective quantitative image analysis and independently by three pathologists.

RESULTS

ALK protein is invariably and exclusively expressed in ALK-rearranged lung adenocarcinomas but at much lower levels than in the prototypic ALK-rearranged tumor, anaplastic large cell lymphoma, and as a result, is often not detected by conventional IHC. We further validate a novel IHC that shows excellent sensitivity and specificity (100% and 99%, respectively) for the detection of ALK-rearranged lung adenocarcinomas in biopsy specimens, with excellent interobserver agreement between pathologists (kappa statistic, 0.94).

CONCLUSIONS

Low levels of ALK protein expression is a characteristic feature of ALK-rearranged lung adenocarcinomas. However, a novel, highly sensitive IHC assay reliably detects lung adenocarcinomas with ALK rearrangements and obviates the need for fluorescence in situ hybridization analysis for the majority of cases, and therefore could be routinely applicable in clinical practice to detect lung cancers that may be responsive to ALK inhibitors.

Molecular pathogenesis of peripheral neuroblastic tumors

Neuroblastoma (NB) is an embryonal cancer of the sympathetic nervous system observed in early childhood, characterized by a broad spectrum of clinical behaviors, ranging from spontaneous regression to fatal outcome despite aggressive therapies. NB accounts for 8-10% of pediatric cancers and 15% of the deaths attributable to malignant conditions in children. Interestingly, NB may occur in various contexts, being mostly sporadic but also familial or syndromic. This review focuses on recent advances in the identification of the genes and mechanisms implicated in NB pathogenesis. Although the extensive characterization of the genomic aberrations recurrently observed in sporadic NBs provides important insights into the understanding of the clinical heterogeneity of this neoplasm, analysis of familial and syndromic cases also unravels essential clues on the genetic bases of NB. Recently, the ALK gene emerged as an important NB gene, being implicated both in sporadic and familial cases. The identification of gene expression signatures associated with patient's outcome points out the potential of using gene expression profiling to improve clinical management of patients suffering from NB. Finally, based on recent observations integrating genomic analyses, biological data and clinical information, we discuss possible evolution/progression schemes in NB.

Incidentally proven pulmonary "ALKoma"

Genetic alterations of echinoderm microtubule-associated protein-like 4 (EML4)-anaplastic lymphoma kinase (ALK) inversion were recently found in lung cancer. A 39-year-old woman with multiple brain metastases and bulky mediastinal lymph node metastases was admitted. Biopsy from her supraclavicular lymph nodes was performed to differentiate the diagnosis between lymphoma and lung cancer. Pathologically, the lymph nodes had a feature of adenocarcinoma. On the other hand, the commercially available chromosomal fluorescent in situ hybridization (FISH) analysis showed split signals of ALK, which was confirmed to be the EML4-ALK inversion. The commercial-based ALK FISH is useful for screening pulmonary ALKoma.

The EML4-ALK transcript but not the fusion protein can be expressed in reactive and neoplastic lymphoid tissues

Rearrangements involving the ALK gene define two distinct entities in the new 2008 WHO classification of lymphoid neoplasms, i.e. ALK+ anaplastic large cell lymphoma and a rare subset of ALK+ diffuse large B-cell lymphoma. Recently, rearrangements involving ALK and the echinoderm microtubule associated protein-like 4 (EML4) gene were described as a specific genetic alteration in about 6% of non-small cell lung cancer (NSCLC). We investigated the expression of EML4-ALK mRNA and protein in 51 reactive and 58 neoplastic lymphoid tissues. EML4-ALK transcripts were detected in 3/51 (5.9%) of reactive lymphoid tissues and 12/58 (20.7%) of lymphomas of different categories, including follicular lymphoma, diffuse large B-cell lymphoma and Hodgkin's disease. Notably, none of these cases expressed the EML4-ALK fusion protein at Western blotting samples and immunohistochemistry. These results indicate that EML4-ALK rearrangements are not specific of NSCLC and raise yet unsolved questions about their role in promoting human neoplasms.

Loss of dystrophin and the microtubule-binding protein ELP-1 causes progressive paralysis and death of adult C. elegans

EMAP-like proteins (ELPs) are conserved microtubule-binding proteins that function during cell division and in the behavior of post-mitotic cells. In Caenorhabditis elegans, ELP-1 is broadly expressed in many cells and tissues including the touch receptor neurons and body wall muscle. Within muscle, ELP-1 is associated with a microtubule network that is closely opposed to the integrin-based adhesion sites called dense bodies. To examine ELP-1 function, we utilized an elp-1 RNA interference assay and screened for synthetic interactions with mutated adhesion site proteins. We reveal a synthetic lethal relationship between ELP-1 and the dystrophin-like protein, DYS-1. Reduction of ELP-1 in a dystrophin [dys-1(cx18)] mutant results in adult animals with motility defects, splayed and hypercontracted muscle with altered cholinergic signaling. Worms fill with vesicles, become flaccid, and die. We conclude that ELP-1 is a genetic modifier of a C. elegans model of muscular dystrophy.

Inhibition of ALK signaling for cancer therapy

Paradigm shifting advances in cancer can occur after discovering the key oncogenic drivers of the malignant process, understanding their detailed molecular mechanisms, and exploiting this transdisciplinary knowledge therapeutically. A variety of human malignancies have anaplastic lymphoma kinase (ALK) translocations, amplifications, or oncogenic mutations, including anaplastic large cell lymphoma, inflammatory myofibroblastic tumors, non-small cell lung cancer, and neuroblastoma. This finding has focused intense interest in inhibiting ALK signaling as an effective molecular therapy against diseases with ALK-driven pathways. Recent progress in the elucidation of the major canonical signaling pathways postulated to be activated by NPM-ALK signaling has provided insight into which pathways may present a rational therapeutic approach. The identification of the downstream effector pathways controlled by ALK should pave the way for the rational design of ALK-inhibition therapies for the treatment of a subset of human cancers that harbor ALK aberrations.

Exon array profiling detects EML4-ALK fusion in breast, colorectal, and non-small cell lung cancers

The echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase (EML4-ALK) fusion gene has been identified as an oncogene in a subset of non-small cell lung cancers (NSCLC). We used profiling of cancer genomes on an exon array to develop a novel computational method for the global search of gene rearrangements. This approach led to the detection of EML4-ALK fusion in breast and colorectal carcinomas in addition to NSCLC. Screening of a large collection of patient tumor samples showed the presence of EML4-ALK fusion in 2.4% of breast (5 of 209), 2.4% of colorectal (2 of 83), and in 11.3% of NSCLC (12 of 106). Besides previously known EML4-ALK variants 1 (E13; A20) and 2 (E20; A20), a novel variant E21; A20 was found in colorectal carcinoma. The presence of an EML-ALK rearrangement was verified by identifying genomic fusion points in tumor samples representative of breast, colon, and NSCLC. EML4-ALK translocation was also confirmed by fluorescence in situ hybridization assay, which revealed its substantial heterogeneity in both primary tumors and tumor-derived cell lines. To elucidate the functional significance of EML4-ALK, we examined the growth of cell lines harboring the fusion following EML4 and ALK silencing by small interfering RNA. Significant growth inhibition was observed in some but not all cell lines, suggesting their variable dependence on ALK-mediated cell survival signaling. Collectively, these findings show the recurrence of EML4-ALK fusion in multiple solid tumors and further substantiate its role in tumorigenesis.

Unique clinicopathologic features characterize ALK-rearranged lung adenocarcinoma in the western population

PURPOSE

The anaplastic large cell kinase gene (ALK) is rearranged in approximately 5% of lung adenocarcinomas within the Asian population. We evaluated the incidence and the characteristics of ALK-rearranged lung adenocarcinomas within the western population and the optimal diagnostic modality to detect ALK rearrangements in routine clinical practice.

EXPERIMENTAL DESIGN

We tested 358 lung adenocarcinomas from three institutions for ALK rearrangements by fluorescent in situ hybridization (FISH) and immunohistochemistry with and without tyramide amplification. The clinicopathologic characteristics of tumors with and without ALK rearrangements were compared.

RESULTS

We identified 20 (5.6%) lung adenocarcinomas with ALK rearrangements within our cohort of western patients. ALK rearrangement was associated with younger age (P = 0.0002), never smoking (P < 0.0001), advanced clinical stage (P = 0.0001), and a solid histology with signet-ring cells (P < 0.0001). ALK rearrangement was identified by FISH in 95% of cases and immunohistochemistry with and without tyramide amplification in 80% and 40% of cases, respectively, but neither FISH nor immunohistochemistry alone detected all cases with ALK rearrangement on initial screening. None of the ALK-rearranged tumors harbored coexisting EGFR mutations.

CONCLUSIONS

Lung adenocarcinomas with ALK rearrangements are uncommon in the western population and represent a distinct entity of carcinomas with unique characteristics. For suspected cases, dual diagnostic testing, with FISH and immunohistochemistry, should be considered to accurately identify lung adenocarcinomas with ALK rearrangement.

Clinical features and outcome of patients with non-small-cell lung cancer who harbor EML4-ALK

PURPOSE

The EML4-ALK fusion oncogene represents a novel molecular target in a small subset of non-small-cell lung cancers (NSCLC). To aid in identification and treatment of these patients, we examined the clinical characteristics and treatment outcomes of patients who had NSCLC with and without EML4-ALK.

PATIENTS AND METHODS

Patients with NSCLC were selected for genetic screening on the basis of two or more of the following characteristics: female sex, Asian ethnicity, never/light smoking history, and adenocarcinoma histology. EML4-ALK was identified by using fluorescent in situ hybridization for ALK rearrangements and was confirmed by immunohistochemistry for ALK expression. EGFR and KRAS mutations were determined by DNA sequencing.

RESULTS

Of 141 tumors screened, 19 (13%) were EML4-ALK mutant, 31 (22%) were EGFR mutant, and 91 (65%) were wild type (WT/WT) for both ALK and EGFR. Compared with the EGFR mutant and WT/WT cohorts, patients with EML4-ALK mutant tumors were significantly younger (P < .001 and P = .005) and were more likely to be men (P = .036 and P = .039). Patients with EML4-ALK-positive tumors, like patients who harbored EGFR mutations, also were more likely to be never/light smokers compared with patients in the WT/WT cohort (P < .001). Eighteen of the 19 EML4-ALK tumors were adenocarcinomas, predominantly the signet ring cell subtype. Among patients with metastatic disease, EML4-ALK positivity was associated with resistance to EGFR tyrosine kinase inhibitors (TKIs). Patients in the EML4-ALK cohort and the WT/WT cohort showed similar response rates to platinum-based combination chemotherapy and no difference in overall survival.

CONCLUSION

EML4-ALK defines a molecular subset of NSCLC with distinct clinical characteristics. Patients who harbor this mutation do not benefit from EGFR TKIs and should be directed to trials of ALK-targeted agents.

Anaplastic lymphoma kinase: role in cancer pathogenesis and small-molecule inhibitor development for therapy

Anaplastic lymphoma kinase (ALK), a receptor tyrosine kinase in the insulin receptor superfamily, was initially identified in constitutively activated oncogenic fusion forms - the most common being nucleophosmin-ALK - in anaplastic large-cell lymphomas, and subsequent studies have identified ALK fusions in diffuse large B-cell lymphomas, systemic histiocytosis, inflammatory myofibroblastic tumors, esophageal squamous cell carcinomas and non-small-cell lung carcinomas. More recently, genomic DNA amplification and protein overexpression, as well as activating point mutations, of ALK have been described in neuroblastomas. In addition to those cancers for which a causative role for aberrant ALK activity is well validated, more circumstantial links implicate the full-length, normal ALK receptor in the genesis of other malignancies - including glioblastoma and breast cancer - via a mechanism of receptor activation involving autocrine and/or paracrine growth loops with the reported ALK ligands, pleiotrophin and midkine. This review summarizes normal ALK biology, the confirmed and putative roles of ALK in the development of human cancers and efforts to target ALK using small-molecule kinase inhibitors.

Anaplastic lymphoma kinase: signalling in development and disease

RTKs (receptor tyrosine kinases) play important roles in cellular proliferation and differentiation. In addition, RTKs reveal oncogenic potential when their kinase activities are constitutively enhanced by point mutation, amplification or rearrangement of the corresponding genes. The ALK (anaplastic lymphoma kinase) RTK was originally identified as a member of the insulin receptor subfamily of RTKs that acquires transforming capability when truncated and fused to NPM (nucleophosmin) in the t(2;5) chromosomal rearrangement associated with ALCL (anaplastic large cell lymphoma). To date, many chromosomal rearrangements leading to enhanced ALK activity have been described and are implicated in a number of cancer types. Recent reports of the EML4 (echinoderm microtubule-associated protein like 4)–ALK oncoprotein in NSCLC (non-small cell lung cancer), together with the identification of activating point mutations in neuroblastoma, have highlighted ALK as a significant player and target for drug development in cancer. In the present review we address the role of ALK in development and disease and discuss implications for the future.

Anaplastic lymphoma kinase immunoreactivity correlates with ALK gene rearrangement and transcriptional up-regulation in non-small cell lung carcinomas

Recently, the fusion gene EML4-ALK was identified in non-small cell lung carcinoma, which could be a potential therapeutic target. We investigated the prevalence of anaplastic lymphoma kinase protein expression in these tumors by immunohistochemistry and correlated the results with data from ALK molecular studies. Gene expression profiling was performed on 35 adenocarcinomas to identify cases with ALK gene up-regulation, which was correlated with protein overexpression by immunohistochemistry. Immunohistochemistry was also performed on an independent cohort consisting of 150 adenocarcinomas and 150 squamous cell carcinomas to evaluate the utility of anaplastic lymphoma kinase immunostaining as a screening tool. Florescence in situ hybridization for the ALK locus and reverse transcriptase-polymerase chain reaction for EML4-ALK were performed on tumors positive for anaplastic lymphoma kinase by immunohistochemistry. Transcriptional up-regulation of ALK was identified in 2 (6%) of 35 adenocarcinomas by gene expression profiling. These 2 cases were positive for anaplastic lymphoma kinase by immunohistochemistry, whereas the remaining 33 cases were completely negative. In the independent cohort, anaplastic lymphoma kinase immunostaining was positive in 1 of 150 squamous cell carcinomas and in 3 of 150 adenocarcinomas. The 6 cases positive for anaplastic lymphoma kinase by immunohistochemistry showed evidence of ALK locus rearrangement by florescence in situ hybridization but were negative for EGFR and KRAS mutation. The presence of EML4-ALK fusion transcript was confirmed in 2 cases by reverse transcriptase-polymerase chain reaction. In conclusion, anaplastic lymphoma kinase immunoreactivity in non-small cell lung carcinomas was associated with transcriptional up-regulation, ALK locus rearrangement, and the presence of EML4-ALK fusion transcript. Anaplastic lymphoma kinase immunohistochemistry may have utility as a screening tool or as a surrogate marker for the molecular techniques to detect the EML4-ALK fusion gene in these tumors.

KIF5B-ALK, a novel fusion oncokinase identified by an immunohistochemistry-based diagnostic system for ALK-positive lung cancer

PURPOSE

EML4-ALK is a transforming fusion tyrosine kinase, several isoforms of which have been identified in lung cancer. Immunohistochemical detection of EML4-ALK has proved difficult, however, likely as a result of low transcriptional activity conferred by the promoter-enhancer region of EML4. The sensitivity of EML4-ALK detection by immunohistochemistry should be increased adequately.

EXPERIMENTAL DESIGN

We developed an intercalated antibody-enhanced polymer (iAEP) method that incorporates an intercalating antibody between the primary antibody to ALK and the dextran polymer-based detection reagents.

RESULTS

Our iAEP method discriminated between tumors positive or negative for EML4-ALK in a test set of specimens. Four tumors were also found to be positive for ALK in an archive of lung adenocarcinoma (n = 130) and another 4 among fresh cases analyzed in a diagnostic laboratory. These 8 tumors were found to include 1 with EML4-ALK variant 1, 1 with variant 2, 3 with variant 3, and 2 with previously unidentified variants (designated variants 6 and 7). Inverse reverse transcription-PCR analysis revealed that the remaining tumor harbored a novel fusion in which intron 24 of KIF5B was ligated to intron 19 of ALK. Multiplex reverse transcription-PCR analysis of additional archival tumor specimens identified another case of lung adenocarcinoma positive for KIF5B-ALK.

CONCLUSIONS

The iAEP method should prove suitable for immunohistochemical screening of tumors positive for ALK or ALK fusion proteins among pathologic archives. Coupling of PCR-based detection to the iAEP method should further facilitate the rapid identification of novel ALK fusion genes such as KIF5B-ALK.

Anaplastic lymphoma kinase: an oncogene for tumor vaccination

The immune system contributes both to the maintenance of cancer in an equilibrium state and to the elimination of tumor cells. Specific antitumor vaccination could increase the intensity or modulate the quality of this immune response against transformed cells. Antitumor vaccination strategies rely upon the identification of one or multiple antigens that can serve to stimulate the immune system. This review will focus particularly on cancer vaccination strategies based on the use of DNA molecules and on the search for antigens that are required for the growth of tumor cells and that cannot be easily down-regulated by the cancer cells (oncoantigens). In addition, we will summarize some results on clinical trials that are currently exploiting selected antigens against tumors and on the recently identified anaplastic lymphoma kinase as a potential oncoantigen for selected types of human cancers.