Mechanisms of acquired crizotinib resistance in ALK-rearranged lung Cancers

Physician recruitment of patients to non-therapeutic oncology clinical trials: ethics revisited

Tailoring medical treatment to individual patients requires a strong foundation in research to provide the data necessary to understand the relationship between the disease, the patient, and the type of treatment advocated for. Non-therapeutic oncology clinical trials studying therapeutic resistance require the participation of patients, yet only a small percentage enroll. Treating physicians are often relied on to recruit patients, but they have a number of ethical obligations that might be perceived as barriers to recruiting. Concepts such as voluntariness of consent and conflicts of interest can have an impact on whether physicians will discuss clinical trials with their patients and how patients perceive the information. However, these ethical obligations should not be prohibitive to physician recruitment of patients - precautions can be taken to ensure that patients' consent to research participation is fully voluntary and devoid of conflict, such as the use of other members of the research team than the treating physician to discuss the trial and obtain consent, and better communication between researchers, clinicians, and patients. These can ensure that research benefits are maximized for the good of patients and society.

ALK in lung cancer: past, present, and future

In 2007, scientists discovered that anaplastic lymphoma kinase (ALK) gene rearrangements are present in a small subset of non-small-cell lung cancers. ALK-positive cancers are highly sensitive to small-molecule ALK kinase inhibitors, such as crizotinib. Phase I and II studies of crizotinib in ALK-positive lung cancer demonstrated impressive activity and clinical benefit, leading to rapid US Food and Drug Administration approval in 2011. Although crizotinib induces remissions and extends the lives of patients, cures are not achieved as resistance to therapy develops. In this review, we will discuss the history of this field, current diagnostic and treatment practices, and future challenges and opportunities to advance outcomes for patients with ALK-positive lung cancers.

PROFILing non-small-cell lung cancer patients for treatment with crizotinib according to anaplastic lymphoma kinase abnormalities: translating science into medicine

INTRODUCTION

In the recent years, the growing attention to the molecular background of non-small-cell lung cancer (NSCLC) led to the identification of different molecular subtypes according to genetic abnormalities driving the disease development and progression. Whereas the addicted pathways were successfully inhibited (such as the mutant epidermal growth factor receptor), clinicians have witnessed a dramatic survival improvement. In this regard, the molecular portrait of adenocarcinoma was recently enriched by the identification of a specific patients' subgroup characterized by abnormalities in the anaplastic lymphoma kinase (ALK), with unclear prognostic features but impressive response to specific inhibitors.

AREAS COVERED

In this article, updated data derived from the development and the use of crizotinib (the most advanced in development among tyrosine kinase ALK inhibitors) in comparison with standard second-line chemotherapy for patients affected by ALK-altered NSCLC are reviewed.

EXPERT OPINION

Taking into account the available data, pretreated NSCLC patients carrying the ALK-translocation require a selected targeted therapy which significantly improves activity, efficacy and symptoms control versus chemotherapy. In this context, the identification of this disease entity and the availability of such impressive therapeutic targeting represent a further step toward the understanding of the molecular complexity behind the adenocarcinoma of the lung.

Oncogenes in non-small-cell lung cancer: emerging connections and novel therapeutic dynamics

Non-small-cell lung cancer is a heterogeneous disease that is difficult to treat. Through efforts to define the molecular mechanisms involved in lung oncogenesis, molecularly targeted approaches for patients with lung cancer have now reached the clinical arena. Despite elucidation of some molecular mechanisms of lung carcinogenesis, prognosis for patients remains poor. This Review aims to highlight the functional associations between key oncogenes that drive lung tumorigenesis and are distinct targetable molecules. Oncogenes are defined by acquisition of mutations, which results in a dominant gain-of-function of the targeted protein. In this situation, a single mutated allele is sufficient to induce malignant transformation. Importantly, tumours become addicted to particular genetic alterations that cause oncogene activation and the continued expression of the signalling. An increasing amount of evidence sustains the rationale for targeting of oncogenic pathways rather than a single oncogene. A clear priority for both researchers and clinicians is to better understand the complexity of biological networks underlying lung cancer pathogenesis. This paradigmatic shift in tailoring therapies should effectively improve outcomes for patients.

Using functional genomics to overcome therapeutic resistance in hematological malignancies

Despite great advances in our understanding of the driving events involved in malignant transformation, only a small number of oncogenic drivers have been targeted and translated into tangible clinical benefit. Moreover, even when a targeted therapy can be shown to effectively inhibit an oncogenic driver, leading to cancer remission, disease persistence and/or relapse is typically inevitable. Reemergence of the cancer can result from either intrinsic or acquired resistance mechanisms that result in failure to eliminate all cancer cells. Intrinsic mechanisms of resistance include tumor heterogeneity and pathways that can compensate for the inhibition of the oncogenic driver. Acquired resistance mechanisms include mutation of the oncogenic driver to directly prevent drug-mediated inhibition and the activation of compensatory survival pathways. RNA interference (RNAi)-based screening provides a powerful approach for the interrogation of both intrinsic and acquired resistance mechanisms. The availability of short interfering (si)RNA libraries targeting all human and mouse genes has made it possible to perform large-scale unbiased screens to identify pathways that are specifically required in cancer cells of particular genotypes or following particular treatments, facilitating the design of potential new therapeutic strategies that may limit resistance mechanisms. In this review, we will discuss how RNAi screens can be used to uncover critical growth and survival pathways and aid in the identification of novel therapeutic targets for improved treatment of hematological malignancies.

Multiplexed deep sequencing analysis of ALK kinase domain identifies resistance mutations in relapsed patients following crizotinib treatment

The recently approved ALK kinase inhibitor crizotinib has demonstrated successful treatment of metastatic and late stage ALK fusion positive non-small cell lung cancer (NSCLC). However, the median duration of clinical benefit is ~10-11months due to the emergence of multiple and simultaneous resistance mechanisms in these tumors. Mutations in the ALK kinase domain confer resistance to crizotinib in about one-third of these patients. We developed a multiplex deep sequencing method using semiconductor sequencing technology to quickly detect resistance mutations within the ALK kinase domain from tumor biopsies. By applying a base-pair specific error-weighted mutation calling algorithm (BASCA) that we developed for this assay, genomic DNA analysis from thirteen relapsed patients revealed three known crizotinib resistance mutations, C1156Y, L1196M and G1269A. Our assay demonstrates robust and sensitive detection of ALK kinase mutations in NSCLC tumor samples and aids in the elucidation of resistance mechanisms pertinent to the clinical setting.

Molecular modelling and simulations in cancer research

The complexity of cancer and the vast amount of experimental data available have made computer-aided approaches necessary. Biomolecular modelling techniques are becoming increasingly easier to use, whereas hardware and software are becoming better and cheaper. Cross-talk between theoretical and experimental scientists dealing with cancer-research from a molecular approach, however, is still uncommon. This is in contrast to other fields, such as amyloid-related diseases, where molecular modelling studies are widely acknowledged. The aim of this review paper is therefore to expose some of the more common approaches in molecular modelling to cancer scientists in simple terms, illustrating success stories while also revealing the limitations of computational studies at the molecular level.

Ask the Experts: Managing non-small-cell lung cancer with acquired resistance to EGF receptor and ALK inhibitors

Professor Siow-Ming Lee is a Professor of Medical Oncology at University College London (UCL), and a Consultant Medical Oncologist at UCL Hospitals. He specializes in the treatment of lung cancer and is Chief or Co-chief Investigator for several National Cancer Research Institute cancer trials in the UK. He chairs the London Lung Cancer Group and the National Cancer Research Institute Advanced Disease Lung Cancer Clinical Subgroup, sits on several national and international executive cancer committees and is a member of a number of international cancer societies.

Dr Judy King is a Specialist Registrar in Medical Oncology at UCL Hospitals. She studied Medicine at Cambridge University and Guy’s, King’s and St Thomas’ Medical and Dental School, and has completed a PhD in cancer immunotherapy at UCL.

Pathology and personalized medicine in lung cancer

SUMMARY Personalized medicine for patients with non-small-cell lung cancer is a reality now and its use will only increase in the future. Pathology is key in supporting this approach to treatment decision-making, by performing the most complete and accurate histological subtyping of tumors possible, supported by predictive immunohistochemistry and the assessment of relevant biomarkers. The need for these extra diagnostic steps emphasizes the importance of maximizing tissue yields from biopsy procedures. Although multiplex approaches may allow simultaneous assessment of several biomarkers, there will remain a need for different types of test (e.g., immunohistochemistry, as well as mutation testing). Next-generation technologies for DNA sequencing are a great hope for extensive genetic analysis of single samples, provided various technical and logistical problems can be solved. All such laboratory activity must be supported by high-quality internal procedures and external quality-assurance schemes.

Lung cancer genotype-based therapy and predictive biomarkers: present and future

CONTEXT

The advent of genotype-based therapy and predictive biomarkers for lung cancer has thrust the pathologist into the front lines of precision medicine for this deadly disease.

OBJECTIVE

To provide the clinical background, current status, and future perspectives of molecular targeted therapy for lung cancer patients, including the pivotal participation of the pathologist.

DATA SOURCES

Data were obtained from review of the pertinent peer-reviewed literature.

CONCLUSIONS

First-generation tyrosine kinase inhibitors have produced clinical response in a limited number of non-small cell lung cancers demonstrated to have activating mutations of epidermal growth factor receptor or anaplastic lymphoma kinase rearrangements with fusion partners. Patients treated with first-generation tyrosine kinase inhibitors develop acquired resistance to their therapy. Ongoing investigations of second-generation tyrosine kinase inhibitors and new druggable targets as well as the development of next-generation genotyping and new antibodies for immunohistochemistry promise to significantly expand the pathologist's already crucial role in precision medicine of lung cancer.

Inhibition of TWIST1 leads to activation of oncogene-induced senescence in oncogene-driven non-small cell lung cancer

A large fraction of non-small cell lung cancers (NSCLC) are dependent on defined oncogenic driver mutations. Although targeted agents exist for EGFR- and EML4-ALK-driven NSCLCs, no therapies target the most frequently found driver mutation, KRAS. Furthermore, acquired resistance to the currently targetable driver mutations is nearly universally observed. Clearly a novel therapeutic approach is needed to target oncogene-driven NSCLCs. We recently showed that the basic helix-loop-helix transcription factor Twist1 cooperates with mutant Kras to induce lung adenocarcinoma in transgenic mouse models and that inhibition of Twist1 in these models led to Kras-induced senescence. In the current study, we examine the role of TWIST1 in oncogene-driven human NSCLCs. Silencing of TWIST1 in KRAS-mutant human NSCLC cell lines resulted in dramatic growth inhibition and either activation of a latent oncogene-induced senescence program or, in some cases, apoptosis. Similar effects were observed in EGFR mutation-driven and c-Met-amplified NSCLC cell lines. Growth inhibition by silencing of TWIST1 was independent of p53 or p16 mutational status and did not require previously defined mediators of senescence, p21 and p27, nor could this phenotype be rescued by overexpression of SKP2. In xenograft models, silencing of TWIST1 resulted in significant growth inhibition of KRAS-mutant, EGFR-mutant, and c-Met-amplified NSCLCs. Remarkably, inducible silencing of TWIST1 resulted in significant growth inhibition of established KRAS-mutant tumors. Together these findings suggest that silencing of TWIST1 in oncogene driver-dependent NSCLCs represents a novel and promising therapeutic strategy.

Targeted inhibition in tumors with ALK dependency

The oncogenic function of gene translocations involving the anaplastic lymphoma kinase (ALK) was first reported in rare subtypes of non-Hodgkin's lymphoma almost two decades ago. More recently, aberrant ALK signaling was found to be an oncogenic driver in subsets of non-small cell lung cancer (NSCLC), particularly in patients with little or no tobacco smoking history. The advent of molecularly targeted therapies that inhibit ALK has allowed the pairing of ALK inhibitors such as crizotinib as treatment for ALK-positive NSCLC, yielding dramatic responses and long-term disease control. The clinicopathologic features of ALK-driven NSCLC, the clinical development of ALK inhibitors, and the genetic determinants of acquired resistance to ALK inhibition are among the topics covered in this review.

Cancer heterogeneity: implications for targeted therapeutics

Developments in genomic techniques have provided insight into the remarkable genetic complexity of malignant tumours. There is increasing evidence that solid tumours may comprise of subpopulations of cells with distinct genomic alterations within the same tumour, a phenomenon termed intra-tumour heterogeneity. Intra-tumour heterogeneity is likely to have implications for cancer therapeutics and biomarker discovery, particularly in the era of targeted treatment, and evidence for a relationship between intra-tumoural heterogeneity and clinical outcome is emerging. Our understanding of the processes that exacerbate intra-tumoural heterogeneity, both iatrogenic and tumour specific, is likely to increase with the development and more widespread implementation of advanced sequencing technologies, and adaptation of clinical trial design to include comprehensive tissue collection protocols. The current evidence for intra-tumour heterogeneity and its relevance to cancer therapeutics will be presented in this mini-review.

Acquired resistance to targeted therapies in advanced non-small cell lung cancer: new strategies and new agents

Although the transition to molecularly defined patient subgroups in advanced non-small cell lung cancer (NSCLC) often leads to dramatic and prolonged responses to an inhibitor of an identified oncogenic mutation, acquired resistance eventually ensues. The optimal approach to management in that setting remains the subject of ongoing research, although it is possible to identify several points that distinguish it from traditional tenets based on conventional chemotherapy. Such patients are not equivalent to those who have progressed on first-line chemotherapy, and consideration of initiation of chemotherapy-based regimens as if the patient were being treated first line in the absence of an oncogenic mutation is a reasonable consideration. Acquired resistance is often partial; therefore, continued treatment with the same targeted therapy or another agent against the same target is a strategy favored by many experts, in part to minimize the risk of "rebound progression" that may occur when the targeted therapy is withdrawn. Progression within the central nervous system (CNS) may occur because of poor penetration of the systemic targeted therapy into the CNS, rather than true cellular resistance to the therapy itself; accordingly, local therapy for "brain only" progression with sustained targeted therapy for extracranial disease can be associated with prolonged disease control. Finally, patients with acquired resistance to a targeted therapy are ideal candidates for clinical trials when available, particularly when repeat biopsies of progressing lesions can help elucidate mechanisms of resistance and thereby lead to histologically and molecularly informed treatment decisions.

Drug Resistance Mechanisms in Non-Small Cell Lung Carcinoma

Lung cancer is the most commonly diagnosed cancer in the world. “Driver” and “passenger” mutations identified in lung cancer indicate that genetics play a major role in the development of the disease, progression, metastasis and response to therapy. Survival rates for lung cancer treatment have remained stagnant at ~15% over the past 40 years in patients with disseminated disease despite advances in surgical techniques, radiotherapy and chemotherapy. Resistance to therapy; either intrinsic or acquired has been a major hindrance to treatment leading to great interest in studies seeking to understand and overcome resistance. Genetic information gained from molecular analyses has been critical in identifying druggable targets and tumor profiles that may be predictors of therapeutic response and mediators of resistance. Mutated or overexpressed epidermal growth factor receptor (EGFR) and translocations in the echinoderm microtubule-associated protein-like 4 (EML4)-anaplastic lymphoma kinase (ALK) genes (EML4-ALK) are examples of genetic aberrations resulting in targeted therapies for both localized and metastatic disease. Positive clinical responses have been noted in patients harboring these genetic mutations when treated with targeted therapies compared to patients lacking these mutations. Resistance is nonetheless a major factor contributing to the failure of targeted agents and standard cytotoxic agents. In this review, we examine molecular mechanisms that are potential drivers of resistance in non-small cell lung carcinoma, the most frequently diagnosed form of lung cancer. The mechanisms addressed include resistance to molecular targeted therapies as well as conventional chemotherapeutics through the activity of multidrug resistance proteins.

Mechanisms of resistance to BCR-ABL and other kinase inhibitors

In this article, we are reviewing the molecular mechanisms that lead to kinase inhibitor resistance. As the oncogenic BCR-ABL kinase is the target of the first approved small-molecule kinase inhibitor imatinib, we will first focus on the structural and mechanistic basis for imatinib resistance. We will then show ways how next generations of BCR-ABL inhibitors and alternative targeting strategies have helped to offer effective treatment options for imatinib-resistant patients. Based on these insights, we discuss commonalities and further mechanisms that lead to resistance to other kinase inhibitors in solid tumors. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases (2012).

Diagnostic assays for identification of anaplastic lymphoma kinase-positive non-small cell lung cancer

In series dominated by adenocarcinoma histology, approximately 5% of non-small cell lung cancers (NSCLCs) harbor an anaplastic lymphoma kinase (ALK) gene rearrangement. Crizotinib, a tyrosine kinase inhibitor with significant activity against ALK, has demonstrated high response rates and prolonged progression-free survival in ALK-positive patients enrolled in phase 1/2 clinical trials. In 2011, crizotinib received accelerated approval from the US Food and Drug Administration (FDA) for the treatment of proven ALK-positive NSCLC using an FDA-approved diagnostic test. Currently, only break-apart fluorescence in situ hybridization testing is FDA approved as a companion diagnostic for crizotinib; however, many other assays are available or in development. In the current review, the authors summarize the diagnostic tests available, or likely to become available, that could be used to identify patients with ALK-positive NSCLC, highlighting the pros and cons of each.

Anaplastic lymphoma kinase (ALK) inhibitors for second-line therapy of non-small cell lung cancer

Targeted therapies are nowadays a treatment option in metastatic non-small cell lung cancer, for which oncogenic drivers have been identified. The epidermal growth factor-receptor tyrosine kinase inhibitors gefitinib and erlotinib, are the standard of care for patients in whom tumors are presenting with an activating epidermal growth factor-receptor mutation, with new active agents like afatinib reaching clinics in the near future. Other genetic abnormalities have been documented in squamous and non-squamous lung cancer. The EML4-ALK gene fusion is a rare event, occurring in around 5% of lung cancer, quite exclusively in adenocarcinoma with a predominance of young non/light smokers. Detection of ALK-positive tumors is challenging, as there is no gold-standard technique. Fluorescence in situ hybridization is the method used in prospective trials assessing the activity of crizotinib and is recommended by the American FDA. Crizotinib is the first orally active inhibitor of receptor tyrosine kinases, including ALK and ROS1, in clinical practice. Impressive results came from a phase I study and are now confirmed in a large phase II study with response rate of 60%, whatever the number of previous lines of chemotherapy. Other ALK inhibitors are currently in the preclinical phase, and some are showing promising results in early phase I/II studies. This review aims to present the current knowledge on the EML4-ALK gene fusion, the pitfalls for the pathologist and the clinician in searching this abnormality, and to review the existing literature on ALK inhibitors under development, focusing their role compared to chemotherapy in non-small cell lung cancer patients.

Crizotinib-resistant NPM-ALK mutants confer differential sensitivity to unrelated Alk inhibitors

The dual ALK/MET inhibitor crizotinib was recently approved for the treatment of metastatic and late-stage ALK+ NSCLC, and is currently in clinical trial for other ALK-related diseases. As predicted after other tyrosine kinase inhibitors' clinical experience, the first mutations that confer resistance to crizotinib have been described in patients with non-small cell lung cancer (NSCLC) and in one patient inflammatory myofibroblastic tumor (IMT). Here, we focused our attention on the anaplastic large cell lymphoma (ALCL), where the oncogenic fusion protein NPM-ALK, responsible for 70% to 80% of cases, represents an ideal crizotinib target. We selected and characterized 2 human NPM-ALK+ ALCL cell lines, KARPAS-299 and SUP-M2, able to survive and proliferate at different crizotinib concentrations. Sequencing of ALK kinase domain revealed that a single mutation became predominant at high crizotinib doses in each cell line, namely L1196Q and I1171N in Karpas-299 and SUP-M2 cells, respectively. These mutations also conferred resistance to crizotinib in Ba/F3 cells expressing human NPM-ALK. The resistant cell populations, as well as mutated Ba/F3 cells, were characterized for sensitivity to two additional ALK inhibitors: the dual ALK/EGFR inhibitor AP26113 and NVP-TAE684. While L1196Q-positive cell lines were sensitive to both inhibitors, cells carrying I1171N substitution showed cross-resistance to all ALK inhibitors tested. This study provides potentially relevant information for the management of patients with ALCL that may relapse after crizotinib treatment.

Incidence and patterns of ALK FISH abnormalities seen in a large unselected series of lung carcinomas

BACKGROUND

Anaplastic lymphoma receptor tyrosine kinase (ALK) gene rearrangements have been reported in 2-13% of patients with non-small cell lung cancer (NSCLC). Patients with ALK rearrangements do not respond to EGFR-specific tyrosine kinase inhibitors (TKIs); however, they do benefit from small molecule inhibitors targeting ALK.

RESULTS

In this study, fluorescence in situ hybridization (FISH) using a break-apart probe for the ALK gene was performed on formalin fixed paraffin-embedded tissue to determine the incidence of ALK rearrangements and hybridization patterns in a large unselected cohort of 1387 patients with a referred diagnosis of non-small cell lung cancer (1011 of these patients had a histologic diagnosis of adenocarcinoma). The abnormal FISH signal patterns varied from a single split signal to complex patterns. Among 49 abnormal samples (49/1387, 3.5%), 32 had 1 to 3 split signals. Fifteen samples had deletions of the green 5' end of the ALK signal, and 1 of these 15 samples showed amplification of the orange 3' end of the ALK signal. Two patients showed a deletion of the 3'ALK signal. Thirty eight of these 49 samples (38/1011, 3.7%) were among the 1011 patients with confirmed adenocarcinoma. Five of 8 patients with ALK rearrangements detected by FISH were confirmed to have EML4-ALK fusions by multiplex RT-PCR. Among the 45 ALK-rearranged samples tested, only 1 EGFR mutation (T790M) was detected. Two KRAS mutations were detected among 24 ALK-rearranged samples tested.

CONCLUSIONS

In a large unselected series, the frequency of ALK gene rearrangement detected by FISH was approximately 3.5% of lung carcinoma, and 3.7% of patients with lung adenocarcinoma, with variant signal patterns frequently detected. Rare cases with coexisting KRAS and EGFR mutations were seen.

Gene fusions in non-small-cell lung cancer

SUMMARY Over the past decade, treatments for patients with advanced non-small-cell lung cancer (NSCLC) have rapidly evolved from histological to molecular treatments. EGFR mutation was the first identified molecular subset of NSCLC and defines a specific group of patients sensitive to EGFR tyrosine kinase inhibitors. ALK rearrangements define another genetic subgroup of NSCLC that is highly responsive to targeted therapy. Advances in bioinformatics and sequencing technology have promoted the identification of genomic abnormalities in NSCLC. ROS1 and RET rearrangements are good examples. However, these genetic rearrangements are only prevalent at a relatively low level. It is important to establish a highly sensitive, specific and reproducible screening procedure. This review will focus on relatively common gene fusions in NSCLC and effective screening procedures.

Local ablative therapy of oligoprogressive disease prolongs disease control by tyrosine kinase inhibitors in oncogene-addicted non-small-cell lung cancer

INTRODUCTION

Many patients with oncogene-driven non-small-cell lung cancer (NSCLC) treated with tyrosine kinase inhibitors experience limited sites of disease progression. This study investigated retrospectively the benefits of local ablative therapy (LAT) to central nervous system (CNS) and/or limited systemic disease progression and continuation of crizotinib or erlotinib in patients with metastatic ALK gene rearrangement (ALK+) or EGFR-mutant (EGFR-MT) NSCLC, respectively.

METHODS

Patients with metastatic ALK+ NSCLC treated with crizotinib (n = 38) and EGFR-MT NSCLC treated with erlotinib (n = 27) were identified at a single institution. Initial response to the respective kinase inhibitors, median progression-free survival (PFS1), and site of first progression were recorded. A subset of patients with either nonleptomeningeal CNS and/or four sites or fewer of extra-CNS progression (oligoprogressive disease) suitable for LAT received either radiation or surgery to these sites and continued on the same tyrosine kinase inhibitors. The subsequent median progression-free survival from the time of first progression (PFS2) and pattern of progression were recorded.

RESULTS

Median progression-free survival in ALK+ patients on crizotinib was 9.0 months, and 13.8 months for EGFR-MT patients on erlotinib. Twenty-five of 51 patients (49%) who progressed were deemed suitable for local therapy (15 ALK+, 10 EGFR-MT; 24 with radiotherapy, one with surgery) and continuation of the same targeted therapy. Post-LAT, 19 of 25 patients progressed again, with median PFS2 of 6.2 months.

DISCUSSION

Oncogene-addicted NSCLC with CNS and/or limited systemic disease progression (oligoprogressive disease) on relevant targeted therapies is often suitable for LAT and continuation of the targeted agent, and is associated with more than 6 months of additional disease control.

The battle against ALK resistance: successes and setbacks

Chromosomal translocations and single point mutations involving the Anaplastic Lymphoma Kinase (ALK) gene have been described in several human tumors, including anaplastic large cell lymphoma (ALCL), non-small cell lung cancer (NCSLC), inflammatory myofibroblastic tumor (IMT) and neuroblastoma. Cancer cells are "addicted" to ALK constitutive activation and are highly sensitive to the treatment with small-molecule inhibitors. Crizotinib, an oral ALK inhibitor, has proved to provide dramatic clinical benefit in patients with NSCLC harboring ALK rearrangements. Nonetheless, acquired drug resistance inevitably develops and leads to tumor progression and relapse. Different mechanisms of crizotinib acquired drug resistance, resembling those reported for other tyrosine kinase targeted therapies, have been recently reported both in cell lines and in patients. Thus, the identification of the molecular mechanisms of crizotinib resistance will be strictly required in order to pursue the appropriate therapeutic options for patients with ALK-rearranged tumors.

Detection of anaplastic lymphoma kinase (ALK) gene rearrangement in non-small cell lung cancer and related issues in ALK inhibitor therapy: a literature review

Anaplastic lymphoma kinase (ALK) encodes a receptor tyrosine kinase, and ALK gene rearrangement (ALK+) is implicated in the oncogenesis of non-small cell lung carcinomas (NSCLCs), especially adenocarcinomas. The ALK inhibitor crizotinib was approved in August 2011 by the US Food and Drug Administration (FDA) for treating late-stage NSCLCs that are ALK+, with a companion fluorescent in situ hybridization (FISH) test using the Vysis ALK Break Apart FISH Probe Kit. This review covers pertinent issues in ALK testing, including approaches to select target patients for the test, pros and cons of different detection methods, and mechanisms as well as monitoring of acquired crizotinib resistance in ALK+ NSCLCs.

Resistance to irreversible EGF receptor tyrosine kinase inhibitors through a multistep mechanism involving the IGF1R pathway

The clinical efficacy of EGF receptor (EGFR) kinase inhibitors gefitinib and erlotinib is limited by the development of drug resistance. The most common mechanism of drug resistance is the secondary EGFR T790M mutation. Strategies to overcome EGFR T790M-mediated drug resistance include the use of mutant selective EGFR inhibitors, including WZ4002, or the use of high concentrations of irreversible quinazoline EGFR inhibitors such as PF299804. In the current study, we develop drug-resistant versions of the EGFR-mutant PC9 cell line, which reproducibly develops EGFR T790M as a mechanism of drug resistance to gefitinib. Neither PF299804-resistant nor WZ4002-resistant clones of PC9 harbor EGFR T790M. Instead, they have shown activated insulin-like growth factor receptor (IGF1R) signaling as a result of loss of expression of IGFBP3 with the IGF1R inhibitor, BMS 536924, restoring EGFR inhibitor sensitivity. Intriguingly, prolonged exposure to either PF299804 or WZ4002 results in the emergence of a more drug-resistant subclone that exhibits ERK activation. A MEK inhibitor, CI-1040, partially restores sensitivity to the EGFR/IGF1R inhibitor combination. Moreover, an IGF1R or MEK inhibitor used in combination with either PF299804 or WZ4002 completely prevents the emergence of drug-resistant clones in this model system. Our studies suggest that more effective means of inhibiting EGFR T790M will prevent the emergence of this common drug resistance mechanism in EGFR-mutant non-small cell lung cancer. However, multiple drug resistance mechanisms can still emerge. Preventing the emergence of drug resistance, by targeting pathways that become activated in resistant cancers, may be a more effective clinical strategy.

Understanding resistance to targeted cancer drugs through loss of function genetic screens

Comprehensive analysis of cancer genomes has provided important insights in the critical alterations that confer proliferation and survival advantage to the tumor, so-called driver mutations. Tumors harboring these genetic changes frequently exhibit striking sensitivities to inhibition of these oncogenic driver pathways, a principle referred to as oncogene addiction. Substantial progress has been made in the development of drugs that specifically target components of the pathways that are associated with these driver mutations. This has enabled the first steps in a shift from the use of cytotoxic drugs to highly selective targeted therapeutic agents for the treatment of cancer. Unfortunately, despite the expanding development of targeted anti-cancer strategies, treatment failure due to primary or acquired resistance is still an almost inevitable outcome in most advanced human cancers. Understanding drug resistance mechanisms will help design more efficient combination treatment strategies that help block resistance mechanisms before they become clinically manifest. In this review, we discuss how RNA interference functional genetic screens can be used to identify clinically relevant mechanisms of drug resistance and how this technology can be used to develop effective combination therapies.

Treatment of ALK-Positive Non–Small Cell Lung Cancer

Crizotinib (Xalkori), the first inhibitor of both anaplastic lymphoma kinase (ALK) and c-Met receptor kinases, has been approved in the United States, Korea, and other countries for the treatment of ALK-positive non–small cell lung cancer (NSCLC). This approval came within just 4 years of the discovery of rearrangements in the ALK gene in a subset of patients with NSCLC. Oral crizotinib 250 mg twice daily showed excellent efficacy in patients with advanced ALK-positive NSCLC, with objective response rates of 61% and 51% in ongoing phase I and II studies, respectively. Objective response rates of current standard, single-agent, second-line therapies are less than 10%. Median progression-free survival was 10 months (95% confidence interval, 8.2–14.7) in the phase I study expanded cohort and has yet to be reached in the phase II study; progression-free survival with current therapies is less than 3 months. Crizotinib was well tolerated; grade 1/2 gastrointestinal toxicity and visual disturbances were the most common adverse events. Patients in the phase II study reported improvements in fatigue, dyspnea, and cough, based on quality of life assessments. Phase III studies investigating crizotinib for the first- and second-line treatment of advanced ALK-positive NSCLC, versus current standards of care, are ongoing. Crizotinib represents a new standard of care for patients with ALK-positive NSCLC and highlights the importance of the role of the pathologist, as molecular profiling becomes a part of initial workups for newly diagnosed patients with NSCLC. This approach will ensure effective individualized treatment for patients with NSCLC.

Intratumor heterogeneity: seeing the wood for the trees

Most advanced solid tumors remain incurable, with resistance to chemotherapeutics and targeted therapies a common cause of poor clinical outcome. Intratumor heterogeneity may contribute to this failure by initiating phenotypic diversity enabling drug resistance to emerge and by introducing tumor sampling bias. Envisaging tumor growth as a Darwinian tree with the trunk representing ubiquitous mutations and the branches representing heterogeneous mutations may help in drug discovery and the development of predictive biomarkers of drug response.

Anaplastic lymphoma kinase as a therapeutic target

INTRODUCTION

Anaplastic lymphoma kinase (ALK), a tyrosine kinase receptor, has been initially identified through its involvement in chromosomal translocations associated with anaplastic large cell lymphoma. However, recent evidence that aberrant ALK activity is also involved in an expanding number of tumor types, such as other lymphomas, inflammatory myofibroblastic tumor, neuroblastomas and some carcinomas, including non-small cell lung carcinomas, is boosting research progress in ALK-targeted therapies.

AREAS COVERED

The first aim of this review is to describe current understandings about the ALK tyrosine kinase and its implication in the oncogenesis of human cancers as a fusion protein or through mutations. The second goal is to discuss its interest as a therapeutic target and to provide a review of the literature regarding ALK inhibitors. Mechanisms of acquired resistance are also reviewed.

EXPERT OPINION

Several ALK inhibitors have recently been developed, offering new treatment options in tumors driven by abnormal ALK signaling. However, as observed with other tyrosine kinase inhibitors, resistance has emerged in patients treated with these agents. The complexity of mechanisms of acquired resistance recently described suggests that other therapeutic options, including combination of ALK and other kinases targeted drugs, will be required in the future.

Crizotinib for the treatment of ALK-rearranged non-small cell lung cancer: a success story to usher in the second decade of molecular targeted therapy in oncology

Crizotinib, an ALK/MET/ROS1 inhibitor, was approved by the U.S. Food and Drug Administration for the treatment of anaplastic lymphoma kinase (ALK)-rearranged non-small cell lung cancer (NSCLC) in August 2011, merely 4 years after the first publication of ALK-rearranged NSCLC. The crizotinib approval was accompanied by the simultaneous approval of an ALK companion diagnostic fluorescent in situ hybridization assay for the detection of ALK-rearranged NSCLC. Crizotinib continued to be developed as an ALK and MET inhibitor in other tumor types driven by alteration in ALK and MET. Crizotinib has recently been shown to be an effective ROS1 inhibitor in ROS1-rearranged NSCLC, with potential future clinical applications in ROS1-rearranged tumors. Here we summarize the heterogeneity within the ALK- and ROS1-rearranged molecular subtypes of NSCLC. We review the past and future clinical development of crizotinib for ALK-rearranged NSCLC and the diagnostic assays to detect ALK-rearranged NSCLC. We highlight how the success of crizotinib has changed the paradigm of future drug development for targeted therapies by targeting a molecular-defined subtype of NSCLC despite its rarity and affected the practice of personalized medicine in oncology, emphasizing close collaboration between clinical oncologists, pathologists, and translational scientists.

Mechanisms of intrinsic and acquired resistance to kinase-targeted therapies

Cancer drugs that target pivotal signaling molecules required for malignant cell survival and growth have demonstrated striking antitumor activities in appropriately selected patient populations. Unfortunately, however, therapeutic responses are often of limited duration, typically 6-12 months, because of emergence of drug-resistant subclones of tumor cells. In this review, we highlight several of the mechanisms of emergent resistance to several kinase-targeted small molecule therapies used in melanoma, non-small cell lung cancer (NSCLC) and other solid tumors as illustrative examples. We discuss the implications of these findings for the development of new treatment strategies to delay or prevent the onset of drug resistance.

Targeting ALK: a promising strategy for the treatment of non-small cell lung cancer, non-Hodgkin's lymphoma, and neuroblastoma

Anaplastic lymphoma kinase (ALK) is a tyrosine kinase receptor that affects a number of biological and biochemical functions through normal ligand-dependent signaling. It has oncogenic functions in a number of tumors including non-small cell lung cancer (NSCLC), anaplastic large cell lymphoma, and neuroblastoma when altered by translocation or amplification or mutation. On August 2011, a small molecule inhibitor against ALK, crizotinib, was approved for therapy against NSCLC with ALK translocations. As we determine the molecular heterogeneity of tumors, the potential of ALK as a relevant therapeutic target in a number of malignancies has become apparent. This review will discuss some of the tumor types with oncogenic ALK alterations. The activity and unique toxicities of crizotinib are described, along with potential mechanisms of resistance and new therapies beyond crizotinib.

Activity and safety of crizotinib in patients with ALK-positive non-small-cell lung cancer: updated results from a phase 1 study

BACKGROUND

ALK fusion genes occur in a subset of non-small-cell lung cancers (NSCLCs). We assessed the tolerability and activity of crizotinib in patients with NSCLC who were prospectively identified to have an ALK fusion within the first-in-man phase 1 crizotinib study.

METHODS

In this phase 1 study, patients with ALK-positive stage III or IV NSCLC received oral crizotinib 250 mg twice daily in 28-day cycles. Endpoints included tumour responses, duration of response, time to tumour response, progression-free survival (PFS), overall survival at 6 and 12 months, and determination of the safety and tolerability and characterisation of the plasma pharmacokinetic profile of crizotinib after oral administration. Responses were analysed in evaluable patients and PFS and safety were analysed in all patients. This study is registered with ClinicalTrials.gov, number NCT00585195.

FINDINGS

Between Aug 27, 2008, and June 1, 2011, 149 ALK-positive patients were enrolled, 143 of whom were included in the response-evaluable population. 87 of 143 patients had an objective response (60·8%, 95% CI 52·3-68·9), including three complete responses and 84 partial responses. Median time to first documented objective response was 7·9 weeks (range 2·1-39·6) and median duration of response was 49·1 weeks (95% CI 39·3-75·4). The response rate seemed to be largely independent of age, sex, performance status, or line of treatment. Median PFS was 9·7 months (95% CI 7·7-12·8). Median overall survival data are not yet mature, but estimated overall survival at 6 and 12 months was 87·9% (95% CI 81·3-92·3) and 74·8% (66·4-81·5), respectively. 39 patients continued to receive crizotinib for more than 2 weeks after progression because of perceived ongoing clinical benefit from the drug (12 for at least 6 months from the time of their initial investigator-defined disease progression). Overall, 144 (97%) of 149 patients experienced treatment-related adverse events, which were mostly grade 1 or 2. The most common adverse events were visual effects, nausea, diarrhoea, constipation, vomiting, and peripheral oedema. The most common treatment-related grade 3 or 4 adverse events were neutropenia (n=9), raised alanine aminotransferase (n=6), hypophosphataemia (n=6), and lymphopenia (n=6).

INTERPRETATION

Crizotinib is well tolerated with rapid, durable responses in patients with ALK-positive NSCLC. There seems to be potential for ongoing benefit after initial disease progression in this population, but a more formal definition of ongoing benefit in this context is needed.

Molecular pathology of non-small cell lung cancer: a practical guide

The traditional distinction between small cell lung cancer and non-small cell lung cancer (NSCLC) is no longer sufficient for treatment planning. It is advised to handle small diagnostic specimens prudently because they are often the only specimen available for molecular analysis. Pathologists are experiencing pressure to subclassify lung carcinoma based on extremely small tumor samples, because NSCLC tumor subtyping is now essential to determine molecular testing strategies. Evaluation for EGFR mutations and ALK rearrangements are now considered to be the standard of care in advanced-stage pulmonary adenocarcinomas. Immunohistochemical stains can aid in subclassifying NSCLC, but performing these ancillary studies can significantly reduce the quantity of tissue available for molecular tests, requiring careful balancing of these 2 needs. The pathologist plays a pivotal role in facilitating clear and timely communication between the clinical oncology care team and the molecular laboratory to ensure that the appropriate tests are ordered and optimal material is submitted for testing.

Variants on a theme: a biomarker of crizotinib response in ALK-positive non-small cell lung cancer?

Anaplastic lymphoma kinase (ALK) gene rearrangements are found in approximately 5% of non-small cell lung carcinoma patients and confer sensitivity to ALK inhibitors such as crizotinib. The particular ALK fusion expressed may have an impact on protein stability and sensitivity to crizotinib, and this may underlie the heterogeneity in responses observed in the clinic.

Impact of genetic dynamics and single-cell heterogeneity on development of nonstandard personalized medicine strategies for cancer

Cancers are heterogeneous and genetically unstable. Current practice of personalized medicine tailors therapy to heterogeneity between cancers of the same organ type. However, it does not yet systematically address heterogeneity at the single-cell level within a single individual's cancer or the dynamic nature of cancer due to genetic and epigenetic change as well as transient functional changes. We have developed a mathematical model of personalized cancer therapy incorporating genetic evolutionary dynamics and single-cell heterogeneity, and have examined simulated clinical outcomes. Analyses of an illustrative case and a virtual clinical trial of over 3 million evaluable "patients" demonstrate that augmented (and sometimes counterintuitive) nonstandard personalized medicine strategies may lead to superior patient outcomes compared with the current personalized medicine approach. Current personalized medicine matches therapy to a tumor molecular profile at diagnosis and at tumor relapse or progression, generally focusing on the average, static, and current properties of the sample. Nonstandard strategies also consider minor subclones, dynamics, and predicted future tumor states. Our methods allow systematic study and evaluation of nonstandard personalized medicine strategies. These findings may, in turn, suggest global adjustments and enhancements to translational oncology research paradigms.

MET targeted therapy for lung cancer: clinical development and future directions

MET, the receptor for hepatocyte growth factor, has been identified as a novel promising target in various human malignancies, including lung cancer. Research studies have demonstrated that MET signaling plays important physiologic roles in embryogenesis and early development, whereas its deregulation from an otherwise quiescent signaling state in mature adult tissues can lead to upregulated cell proliferation, survival, scattering, motility and migration, angiogenesis, invasion, and metastasis in tumorigenesis and tumor progression. The MET pathway can be activated through ligand (hepatocyte growth factor, HGF) or MET receptor overexpression, genomic amplification, MET mutations, and alternative splicing. A number of novel therapeutic agents that target the MET/hepatocyte growth factor pathway have been tested in early-phase clinical studies with promising results. Phase III studies of MET targeting agents have recently been initiated. This paper will review the MET signaling pathway and biology in lung cancer, and the recent clinical development and advances of MET/hepatocyte growth factor targeting agents. Emphasis will be placed on discussing various unanswered issues and key strategies needed to optimize further clinical development of MET targeting personalized lung cancer therapy.

Activation of HER family signaling as a mechanism of acquired resistance to ALK inhibitors in EML4-ALK-positive non-small cell lung cancer

PURPOSE

Anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitors (TKI) such as crizotinib show marked efficacy in patients with non-small cell lung cancer positive for the echinoderm microtubule-associated protein-like 4 (EML4)-ALK fusion protein. However, acquired resistance to these agents has already been described in treated patients, and the mechanisms of such resistance remain largely unknown.

EXPERIMENTAL DESIGN

We established lines of EML4-ALK-positive H3122 lung cancer cells that are resistant to the ALK inhibitor TAE684 (H3122/TR cells) and investigated their resistance mechanism with the use of immunoblot analysis, ELISA, reverse transcription and real-time PCR analysis, and an annexin V binding assay. We isolated EML4-ALK-positive lung cancer cells (K-3) from a patient who developed resistance to crizotinib and investigated their characteristics.

RESULTS

The expression of EML4-ALK was reduced at the transcriptional level, whereas phosphorylation of epidermal growth factor receptor (EGFR), HER2, and HER3 was upregulated, in H3122/TR cells compared with those in H3122 cells. This activation of HER family proteins was accompanied by increased secretion of EGF. Treatment with an EGFR-TKI induced apoptosis in H3122/TR cells, but not in H3122 cells. The TAE684-induced inhibition of extracellular signal-regulated kinase (ERK) and STAT3 phosphorylation observed in parental cells was prevented by exposure of these cells to exogenous EGF, resulting in a reduced sensitivity of cell growth to TAE684. K-3 cells also manifested HER family activation accompanied by increased EGF secretion.

CONCLUSIONS

EGF-mediated activation of HER family signaling is associated with ALK-TKI resistance in lung cancer positive for EML4-ALK.

microRNA regulation of cell viability and drug sensitivity in lung cancer

INTRODUCTION

microRNAs (miRNAs) are 19 - 23 nucleotide long RNAs found in multiple organisms that regulate gene expression and have been shown to play important roles in tumorigenesis. In the context of lung cancer, numerous studies have shown that tumor suppressor genes and oncogenes that play crucial roles in lung tumor development and progression are targets of miRNA regulation. Manipulation of miRNA levels that modulate lung cancer cell survival and drug sensitivity can therefore provide novel therapeutic targets and agents.

AREAS COVERED

Here, the authors review the published in vitro, in vivo and preclinical studies on the functional role of miRNAs in modulating lung cancer cell viability and drug response, and discuss the limitations and promise of translating current findings into miRNA-based therapeutic and diagnostic strategies.

EXPERT OPINION

Although many miRNAs have been identified as potent regulators of cell viability and drug sensitivity in lung cancer, most of them have not been characterized for potential clinical application. Further study is warranted to evaluate translation of the current findings to the clinic to improve the diagnosis and treatment of lung cancer. In addition, most studies have focused on non-small cell lung cancer (NSCLC). It is therefore important to raise interest in investigating miRNAs in small cell lung cancer (SCLC) as well as in comparative studies of miRNA expression and function in different histological subtypes of lung cancer.

Inhibitors of the anaplastic lymphoma kinase

INTRODUCTION

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase normally expressed in the developing nervous tissue. Genetic alterations of ALK are associated with a number of cancers, including anaplastic large cell lymphoma (ALCL) and a subset of non-small cell lung cancer (NSCLC). Standard therapies for these diseases include surgery plus unspecific cytotoxic agents, with a low therapeutic window and significant treatment-associated systemic toxicity. A few small-molecule inhibitors of ALK kinase activity have been described in the recent years, some of which are currently undergoing clinical evaluation.

AREAS COVERED

Literature was searched for all ALK inhibitors that have entered clinical investigation, including published research articles and meeting abstracts. Data on pharmacokinetics, safety and efficacy of crizotinib, as well as preliminary clinical data for second-generation compounds, are reviewed. The issue of drug resistance is discussed.

EXPERT OPINION

Understanding the specific genetic aberration that causes cancer development and progression allows major advances in cancer therapy. Along the same way shown by imatinib in chronic myeloid leukemia, compounds that selectively target ALK are bringing a revolution in the treatment of ALK-positive tumors. Crizotinib has just been approved, and new more potent ALK inhibitors will shortly follow. These molecules represent another excellent proof-of-principle for targeted therapy.

ALKoma: a cancer subtype with a shared target

Anaplastic lymphoma kinase (ALK) is a receptor-type protein tyrosine kinase that is currently the focus of much attention in oncology. ALK is rendered oncogenic as a result of its fusion to NPM1 in anaplastic large cell lymphoma, to TPM3 or TPM4 in inflammatory myofibroblastic tumor, to EML4 in non-small cell lung carcinoma, and to VCL in renal medullary carcinoma. It is also activated as a result of missense mutations in neuroblastoma and anaplastic thyroid cancer. Whereas these various tumors arise in different organs, they share activated ALK, and a marked clinical efficacy with ALK inhibitors has already been shown for some of the tumors with ALK fusions. One of such compound, crizotinib, is now approved in the United States for the treatment of lung cancer positive for ALK rearrangement. I propose that tumors carrying abnormal ALK as an essential growth driver be collectively termed "ALKoma."