Anaplastic lymphoma kinase: signalling in development and disease

Targeted agents for sarcoma: is individualized therapy possible in such a diverse tumor type?

A wide variety of cytogenetic abnormalities and molecular pathways have been implicated in the pathogenesis of sarcoma, and significant progress has been made in the past decade toward identifying potential therapeutic targets. However, apart from gastrointestinal stromal tumors (GISTs) and dermatofibrosarcoma protuberans (DFSP), little progress has been made toward translating that knowledge into effective therapeutic strategies. The identification of activating KIT mutations in the majority of GISTs was a defining moment that led to the first effective targeted therapy for sarcoma, and the subsequent use of imatinib mesylate has revolutionized the treatment of GISTs. Beyond imatinib, the most promising agents to date--and the agents most extensively studied--are the multitargeted tyrosine kinase inhibitors. Several other classes of agents have also shown some activity in soft tissue sarcomas, including mammalian target of rapamycin inhibitors, inhibitors of growth factor receptors, histone deacetylase inhibitors, agents that modulate the p53 pathway, inhibitors of molecular chaperone proteins (eg, heat shock protein 90 [Hsp90]), and other signal transduction inhibitors. Despite a large number of completed and ongoing phase II studies, few agents have moved to phase III testing, and much work remains to be done to fully validate the identified targets and determine the optimal treatment strategy. Ongoing studies are exploring a wide range of combination strategies. This review will highlight some of the emerging targeted therapies that appear to hold promise and may eventually contribute to improved systemic therapy for sarcoma.

Midkine and Alk signaling in sympathetic neuron proliferation and neuroblastoma predisposition

Neuroblastoma (NB) is the most common extracranial solid tumor in childhood and arises from cells of the developing sympathoadrenergic lineage. Activating mutations in the gene encoding the ALK tyrosine kinase receptor predispose for NB. Here, we focus on the normal function of Alk signaling in the control of sympathetic neuron proliferation, as well as on the effects of mutant ALK. Forced expression of wild-type ALK and NB-related constitutively active ALK mutants in cultures of proliferating immature sympathetic neurons results in a strong proliferation increase, whereas Alk knockdown and pharmacological inhibition of Alk activity decrease proliferation. Alk activation upregulates NMyc and trkB and maintains Alk expression by an autoregulatory mechanism involving Hand2. The Alk-ligand Midkine (Mk) is expressed in immature sympathetic neurons and in vivo inhibition of Alk signaling by virus-mediated shRNA knockdown of Alk and Mk leads to strongly reduced sympathetic neuron proliferation. Taken together, these results demonstrate that the extent and timing of sympathetic neurogenesis is controlled by Mk/Alk signaling. The predisposition for NB caused by activating ALK mutations may thus be explained by aberrations of normal neurogenesis, i.e. elevated and sustained Alk signaling and increased NMyc expression.

CEP-28122, a highly potent and selective orally active inhibitor of anaplastic lymphoma kinase with antitumor activity in experimental models of human cancers

Anaplastic lymphoma kinase (ALK) is constitutively activated in a number of human cancer types due to chromosomal translocations, point mutations, and gene amplification and has emerged as an excellent molecular target for cancer therapy. Here we report the identification and preclinical characterization of CEP-28122, a highly potent and selective orally active ALK inhibitor. CEP-28122 is a potent inhibitor of recombinant ALK activity and cellular ALK tyrosine phosphorylation. It induced concentration-dependent growth inhibition/cytotoxicity of ALK-positive anaplastic large-cell lymphoma (ALCL), non-small cell lung cancer (NSCLC), and neuroblastoma cells, and displayed dose-dependent inhibition of ALK tyrosine phosphorylation in tumor xenografts in mice, with substantial target inhibition (>90%) for more than 12 hours following single oral dosing at 30 mg/kg. Dose-dependent antitumor activity was observed in ALK-positive ALCL, NSCLC, and neuroblastoma tumor xenografts in mice administered CEP-28122 orally, with complete/near complete tumor regressions observed following treatment at doses of 30 mg/kg twice daily or higher. Treatment of mice bearing Sup-M2 tumor xenografts for 4 weeks and primary human ALCL tumor grafts for 2 weeks at 55 or 100 mg/kg twice daily led to sustained tumor regression in all mice, with no tumor reemergence for more than 60 days postcessation of treatment. Conversely, CEP-28122 displayed marginal antitumor activity against ALK-negative human tumor xenografts under the same dosing regimens. Administration of CEP-28122 was well tolerated in mice and rats. In summary, CEP-28122 is a highly potent and selective orally active ALK inhibitor with a favorable pharmaceutical and pharmacokinetic profile and robust and selective pharmacologic efficacy against ALK-positive human cancer cells and tumor xenograft models in mice.

Emerging therapeutic targets for soft tissue sarcoma

Soft tissue sarcomas (STS) are malignancies of mesenchymal origin that represent approximately 1% of cancers in adults. Systematic research into the treatment of STS is challenging given its rarity and disease heterogeneity. Despite the ability to histologically subtype STS, only recently has our approach to therapy begun to differentiate along these lines. The purpose of this review is to highlight emerging therapeutic targets and therapies that hold the potential to add to the current state of systemic treatment for STS.

NPM-ALK signals through glycogen synthase kinase 3β to promote oncogenesis

Anaplastic large cell lymphoma (ALCL) is the most common type of pediatric peripheral T-cell lymphoma. In 70-80% of cases, the chromosomal aberration t(2;5)(p23;q35) results in the juxtaposition of anaplastic lymphoma kinase (ALK) with nucleophosmin (NPM) and the subsequent expression of the NPM-ALK fusion protein. NPM-ALK is a chimeric tyrosine kinase, which induces numerous signaling pathways that drive proliferation and abrogate apoptosis. However, the mechanisms that lead to activation of downstream growth regulatory molecules have not been completely elucidated. Using a mass spectrometry-based phosphoproteomic screen, we identified GSK3β as a signaling mediator of NPM-ALK. Using a selective inhibitor of ALK, we demonstrated that the tyrosine kinase activity of ALK regulates the serine-9 phosphorylation of GSK3β. Expression of NPM-ALK in 293T cells led to an increase of pS(9)-GSK3β (glycogen synthase kinase 3 beta) compared with kinase-defective K210R mutant NPM-ALK, but did not affect total GSK3β levels. Phosphorylation of pS(9)-GSK3β by NPM-ALK was mediated by the PI3K/AKT signaling pathway. ALK inhibition resulted in degradation of GSK3β substrates Mcl-1 and CDC25A, which was recovered upon chemical inhibition of the proteasome (MG132). Furthermore, the degradation of Mcl-1 was recoverable with inhibition of GSK3β. ALK inhibition also resulted in decreased cell viability, which was rescued by GSK3β inhibition. Furthermore, stable knockdown of GSK3β conferred resistance to the growth inhibitory effects of ALK inhibition using viability and colony formation assays. pS(9)-GSK3β and CDC25A were selectively expressed in neoplastic cells of ALK+ALCL tissue biopsies, and showed a significant correlation (P<0.001). Conversely, ALK-ALCL tissue biopsies did not show significant correlation of pS(9)-GSK3β and CDC25A expression (P<0.2). Our results demonstrate that NPM-ALK regulates the phosphorylation of S(9)-GSK3β by PI3K/AKT. The subsequent inhibition of GSK3β activity results in accumulation of CDC25A and Mcl-1, which confers the advantage of growth and protection from apoptosis. These findings provide support for the role of GSK3β as a mediator of NPM-ALK oncogenesis.

Detection of ALK gene rearrangement in non-small cell lung cancer: a comparison of fluorescence in situ hybridization and chromogenic in situ hybridization with correlation of ALK protein expression

INTRODUCTION

Accurate determination of ALK rearrangement is important in lung cancer patients, especially in determining their eligibility for crizotinib therapy. Fluorescence in situ hybridization (FISH) has been regarded as the gold standard method for detecting ALK rearrangement. However, FISH requires a fluorescence microscope, and the signals are labile and rapidly fade over time. This study evaluates the concordance between ALK gene rearrangement in non-small cell lung cancer assessed by ALK FISH and a newly developed ALK chromogenic in situ hybridization (CISH) and correlates the results with ALK protein expression assessed by immunohistochemistry.

METHODS

A total of 465 formalin-fixed, paraffin-embedded non-small cell lung cancer samples were analyzed by ALK FISH (PathVysion, Vysis, Abbott) and ALK CISH. For comparison, all specimens were stained by immunohistochemistry (clone 5A4, Novocastra) and interobserver reproducibility was assessed.

RESULTS

We found that agreement between the pathologists on the CISH-determined ALK status was achieved in 449 patients (96.6%), and ALK rearrangement was identified in 18 patients (4.0%) in CISH method. Among these cases, 443 cases (95.3%) had results matching the corresponding FISH results: 17 rearranged, 425 wild types, and 1 discordant case. There was high concordance in the assessment of ALK gene rearrangement between FISH and CISH techniques (κ = 0.92) and between observers (κ = 0.97). In addition, there was high concordance in the ALK gene status and ALK protein expression between CISH and IHC tests (κ = 0.82).

CONCLUSIONS

CISH is a highly reproducible and practical method to detect ALK gene rearrangement and correlated well with ALK protein expression. Here, we present a diagnostic algorithm (Chung's SNUBH ALK protocol) to detect lung cancer with ALK rearrangements using IHC, FISH and CISH. Because CISH allows a concurrent analysis of histological features of the tumors and gene rearrangement, it appears to be a useful method in determining ALK gene rearrangement.

Identification of oncogenic point mutations and hyperphosphorylation of anaplastic lymphoma kinase in lung cancer

The oncogenic property of anaplastic lymphoma kinase (ALK) plays an essential role in the pathogenesis of various cancers and serves as an important therapeutic target. In this study, we identified frequent intragenic loss of heterozygosity and six novel driver mutations within ALK in lung adenocarcinomas. Overexpression of H694R or E1384K mutant ALK leads to hyperphosphorylation of ALK, and activation of its downstream mediators STAT3, AKT, and ERK resulted in enhanced cell proliferation, colony formation, cell migration, and tumor growth in xenograft models. Furthermore, the activated phospho-Y1604 ALK was increasingly detected in 13 human lung cancer cell lines and 263 lung cancer specimens regardless of tumor stages and types. Treatment of two different ALK inhibitors, WHI-P154 and NVP-TAE684, resulted in the down-regulation of aberrant ALK signaling, shrinkage of tumor, and suppression of metastasis and significantly improved survival of ALK mutant-bearing mice. Together, we identified that novel ALK point mutations possessed tumorigenic effects mainly through hyperphosphorylation of Y1604 and activation of downstream oncogenic signaling. The upregulated phospho-Y1604 ALK could serve as a diagnostic biomarker for lung cancer. Furthermore, targeting oncogenic mutant ALKs with inhibitors could be a promising strategy to improve the therapeutic efficacy of fatal lung cancers.

The potential for crizotinib in non-small cell lung cancer: a perspective review

Tyrosine kinases have a crucial role as key regulators of signaling pathways that influence cell differentiation and growth. Dysregulation of tyrosine kinase-mediated signaling is understood to be an important oncogenic driver. Genetic rearrangements involving the tyrosine kinase anaplastic lymphoma kinase (ALK) gene occur in non-small cell lung cancer (NSCLC), anaplastic large cell lymphomoas, inflammatory myofibroblastic tumors, and other cancers. Cells with abnormal ALK signaling are sensitive to ALK inhibitors such as crizotinib. This review will highlight the discovery of the fusion between echinoderm microtubule-associated protein-like 4 (EML4) and ALK as an oncogenic driver, recognition of other ALK gene rearrangements in NSCLC, and the confirmation that crizotinib is an effective treatment for patients with ALK-positive NSCLC. Work is underway to further define the role for crizotinib in the treatment of ALK-positive lung cancer and other cancers and to investigate the molecular mechanisms for resistance to ALK inhibition with crizotinib.

Ets-1 activates overexpression of JunB and CD30 in Hodgkin's lymphoma and anaplastic large-cell lymphoma

Overexpression of CD30 and JunB is a hallmark of tumor cells in Hodgkin's lymphoma (HL) and anaplastic large-cell lymphoma (ALCL). We reported that CD30-extracellular signal-regulated kinase (ERK)1/2 mitogen-activated protein kinase (MAPK) signaling induces JunB, which maintains constitutive activation of the CD30 promoter. Herein, we localize a cis-acting enhancer in the JunB promoter that is regulated by Ets-1. We show that E26 transformation-specific-1 (Ets-1) (-146 to -137) enhances JunB promoter activation in a manner that is dependent on CD30 or the nucleophosmin-anaplastic lymphoma kinase (NPM-ALK)-ERK1/2 MAPK pathway. Ets-1 knockdown reduces the expression of both JunB and CD30, and CD30 knockdown significantly reduces JunB expression in HL and ALCL cell lines. NPM-ALK knockdown also reduces JunB expression in ALCL cell lines expressing NPM-ALK. Collectively, these results indicate that CD30 and NPM-ALK cooperate to activate the ERK1/2 MAPK-Ets-1 pathway. Ets-1, constitutively activated by ERK1/2-MAPK, plays a central role in the overexpression of JunB and CD30, which are both involved in the pathogenesis of HL and ALCL.

Copy number status and mutation analyses of anaplastic lymphoma kinase (ALK) gene in 90 sporadic neuroblastoma tumors

Somatic and germline mutations of the anaplastic lymphoma kinase (ALK) gene were recently described in neuroblastoma (NB). In this study, we investigated the association of ALK copy number alterations with copy number status 2p24.1 amplicon harboring DEAD box polypeptide 1 (DDX1), MYCN and neuroblastoma-amplified (NAG) genes in 90 primary tumors of sporadic NB cases by multiplex ligation-dependent probe amplification (MLPA). We also performed mutation analysis of ALK gene by directly sequencing the exons 20-28 which cover the region that encodes juxtamembrane and kinase domains. A total of 39 (43.3%) NB cases revealed copy numbers alterations of ALK gene. There was highly significant association of ALK copy number gains with gains of one or more of the genes at 2p24.1 (DDX1, MYCN or NAG) in MYCN unamplified tumors (P<0.000). In addition, 15 of 17 MYCN amplified cases (88.2%) had aberrant ALK status. Solitary gain of ALK with normal copy number status of all other genes was observed only in one case. DNA sequencing of exons 20-28 of ALK revealed two different nucleotide changes in three cases leading to amino acid substitutions of F1245V and R1275Q in tyrosine kinase domain. In conclusion, the frequency of ALK mutations in NB is low and solitary copy number change of it is rarely observed.

Cooperative Cross-Talk between Neuroblastoma Subtypes Confers Resistance to Anaplastic Lymphoma Kinase Inhibition

Neuroblastoma is a pediatric solid tumor that can be stratified into stroma-rich and stroma-poor histological subgroups. The stromal compartment of neuroblastoma is composed mostly of Schwann cells, and they play critical roles in the differentiation, survival, and angiogenic responses of tumor cells. In certain neuroblastoma cell lines, the coexistence of neuroblastic N-type and substrate-adherent S-type is frequently observed. One such cell line, SK-N-SH, harbors a F1174L oncogenic mutation in the anaplastic lymphoma kinase (ALK) gene. Treatment of SK-N-SH with an ALK chemical inhibitor, TAE684, resulted in the outgrowth of S-type cells that expressed the Schwann cell marker, S100α6. Nucleotide sequencing analysis of these TAE684-resistant (TR) sublines revealed the presence of the ALK F1174L mutation, suggesting their tumor origin, although ALK protein was not detected. Consistent with these findings, TR cells displayed approximately 9-fold higher IC(50) values than N-type cells. Also, unlike N-type cells, TR cells have readily detectable phosphorylated STAT3 but weaker phosphorylated AKT. Under coculture conditions, TR cells conferred survival to N-type cells against the apoptotic effect of TAE684. Cocultivation also greatly enhanced the overall phosphorylation of STAT3 and its transcriptional activity in N-type cells. Finally, conditioned medium from TR clones enhanced cell viability of N-type cells, and this effect was phosphatidylinositol 3-kinase dependent. Taken together, these results demonstrate the ability of tumor-derived S-type cells in protecting N-type cells against the apoptotic effect of an ALK kinase inhibitor through upregulating prosurvival signaling.

ALK and NSCLC: Targeted therapy with ALK inhibitors

For many years treatment for advanced or metastatic non-small cell lung cancer (NSCLC) has employed chemotherapy regimens for patient care, with limited effect. Five-year survival rates for these patients are not encouraging. However, for a subgroup of these patients, there have been radical changes over recent years. Our understanding of the basic pathology behind NSCLC at the molecular level has offered up a host of new molecularly targeted therapies, which are revolutionizing this area of cancer care. Results from recent clinical trials provide hope for NSCLC patients harboring oncogenic translocations involving the anaplastic lymphoma kinase (ALK) receptor tyrosine kinase. Just as inhibition of the breakpoint cluster region-ABL complex has changed the face of chronic myeloid leukemia diagnosis, oncogenic ALK fusions offer a step forward in the diagnosis and treatment of ALK-positive NSCLC. This article discusses the current knowledge and potential implications concerning ALK inhibitors and NSCLC.

Targeted therapies for lung cancer: clinical experience and novel agents

Although lung cancer remains the leading cancer killer in the United States, recently a number of developments indicate future clinical benefit. These include evidence that computed tomography-based screening decreases lung cancer mortality, the use of stereotactic radiation for early-stage tumors, the development of molecular methods to predict chemotherapy sensitivity, and genome-wide expression and mutation analysis data that have uncovered oncogene "addictions" as important therapeutic targets. Perhaps the most significant advance in the treatment of this challenging disease is the introduction of molecularly targeted therapies, a term that currently includes monoclonal antibodies and small-molecule tyrosine kinase inhibitors. The development of effective targeted therapeutics requires knowledge of the genes and pathways involved and how they relate to the biologic behavior of lung cancer. Drugs targeting the epidermal growth factor receptor, anaplastic lymphoma kinase, and vascular endothelial growth factor are now U.S. Food and Drug Administration approved for the treatment of advanced non-small cell lung cancer. These agents are generally better tolerated than conventional chemotherapy and show dramatic efficacy when their use is coupled with a clear understanding of clinical data, mechanism, patient selection, drug interactions, and toxicities. Integrating genome-wide tumor analysis with drug- and targeted agent-responsive phenotypes will provide a wealth of new possibilities for lung cancer-targeted therapeutics. Ongoing research efforts in these areas as well as a discussion of emerging targeted agents being evaluated in clinical trials are the subjects of this review.

Extracellular matrix and its receptors in Drosophila neural development

Extracellular matrix (ECM) and matrix receptors are intimately involved in most biological processes. The ECM plays fundamental developmental and physiological roles in health and disease, including processes underlying the development, maintenance, and regeneration of the nervous system. To understand the principles of ECM-mediated functions in the nervous system, genetic model organisms like Drosophila provide simple, malleable, and powerful experimental platforms. This article provides an overview of ECM proteins and receptors in Drosophila. It then focuses on their roles during three progressive phases of neural development: (1) neural progenitor proliferation, (2) axonal growth and pathfinding, and (3) synapse formation and function. Each section highlights known ECM and ECM-receptor components and recent studies done in mutant conditions to reveal their in vivo functions, all illustrating the enormous opportunities provided when merging work on the nervous system with systematic research into ECM-related gene functions.

The landscape of EGFR pathways and personalized management of non-small-cell lung cancer

Two classes of anti-EGF receptor (EGFR) agents, monoclonal anti-EGFR antibodies and small-molecule EGFR tyrosine kinase inhibitors, have been used for the treatment of non-small-cell lung cancer (NSCLC). However, only a subset of patients will benefit from EGFR-targeted therapy. The discovery of biomarkers that select the appropriate patients for the therapy and predict the responses to the therapy is urgently needed. Molecular genetic analyses provide new insights into EGFR pathway alterations and demonstrate promise for predicting the clinical outcome of patients with NSCLC. In this article, we summarize the latest available knowledge on the clinical impact of EGFR mutations, gene copy number, EGFR overexpression, phosphorylation expression and the alteration of the EGFR pathway downstream factors in predicting the response to EGFR-targeted therapy in NSCLC patients. The role of KRAS and BRAF mutations and ALK rearrangement in lung cancer-targeted therapy, are also reviewed.

Targeted molecular therapy in peripheral T-cell lymphomas

Peripheral T-cell lymphomas (PTCLs) are rare neoplasms constituting a heterogeneous group of diseases. At present, available chemotherapy regimens that have improved outcomes in B-cell lymphomas appear to be less efficacious in the context of PTCLs and, thus, alternative strategies are warranted. In the last few years, based on the recent, deeper understanding of PTCL biology, several molecules and/or pathways have been proposed for targeted therapy in this setting, including surface antigens, tyrosine kinases, the NF-κB pathway, folate metabolism, histone modification and others. Of particular interest, histone deacetylase and proteasome inhibitors, as well as novel chemotherapeutic agents such as pralatrexate, have already demonstrated efficacy in PTCL therapy. In addition, a strong biological rationale and early clinical evidence supports the future study of tyrosine kinase inhibitors in this setting. In this article, the authors review the available literature on targeted therapy in PTCLs and also, based on their own experience, discuss potential opportunities in this intriguing area.

ALK mutations conferring differential resistance to structurally diverse ALK inhibitors

PURPOSE

EML4-ALK fusions define a subset of lung cancers that can be effectively treated with anaplastic lymphoma kinase (ALK) inhibitors. Unfortunately, the duration of response is heterogeneous and acquired resistance limits their ultimate efficacy. Thus, a better understanding of resistance mechanisms will help to enhance tumor control in EML4-ALK-positive tumors.

EXPERIMENTAL DESIGN

By applying orthogonal functional mutagenesis screening approaches, we screened for mutations inducing resistance to the aminopyridine PF02341066 (crizotinib) and/or the diaminopyrimidine TAE684.

RESULTS

Here, we show that the resistance mutation, L1196M, as well as other crizotinib resistance mutations (F1174L and G1269S), are highly sensitive to the structurally unrelated ALK inhibitor TAE684. In addition, we identified two novel EML4-ALK resistance mutations (L1198P and D1203N), which unlike previously reported mutations, induced resistance to both ALK inhibitors. An independent resistance screen in ALK-mutant neuroblastoma cells yielded the same L1198P resistance mutation but defined two additional mutations conferring resistance to TAE684 but not to PF02341066.

CONCLUSIONS

Our results show that different ALK resistance mutations as well as different ALK inhibitors impact the therapeutic efficacy in the setting of EML4-ALK fusions and ALK mutations.

Emerging importance of ALK in neuroblastoma

Since the original descriptions of gain-of function mutations in anaplastic lymphoma kinase (ALK), interest in the role of this receptor tyrosine kinase in neuroblastoma development and as a potential therapeutic target has escalated. As a group, the activating point mutations in full-length ALK, found in approximately 8% of all neuroblastoma tumors, are distributed evenly across different clinical stages. However, the most frequent somatic mutation, F1174L, is associated with amplification of the MYCN oncogene. This combination of features appears to confer a worse prognosis than MYCN amplification alone, suggesting a cooperative effect on neuroblastoma formation by these two proteins. Indeed, F1174L has shown more potent transforming activity in vivo than the second most common activating mutation, R1275Q, and is responsible for innate and acquired resistance to crizotinib, a clinically relevant ALK inhibitor that will soon be commercially available. These advances cast ALK as a bona fide oncoprotein in neuroblastoma and emphasize the need to understand ALK-mediated signaling in this tumor. This review addresses many of the current issues surrounding the role of ALK in normal development and neuroblastoma pathogenesis, and discusses the prospects for clinically effective targeted treatments based on ALK inhibition.

The receptor tyrosine kinase Alk controls neurofibromin functions in Drosophila growth and learning

Anaplastic Lymphoma Kinase (Alk) is a Receptor Tyrosine Kinase (RTK) activated in several cancers, but with largely unknown physiological functions. We report two unexpected roles for the Drosophila ortholog dAlk, in body size determination and associative learning. Remarkably, reducing neuronal dAlk activity increased body size and enhanced associative learning, suggesting that its activation is inhibitory in both processes. Consistently, dAlk activation reduced body size and caused learning deficits resembling phenotypes of null mutations in dNf1, the Ras GTPase Activating Protein-encoding conserved ortholog of the Neurofibromatosis type 1 (NF1) disease gene. We show that dAlk and dNf1 co-localize extensively and interact functionally in the nervous system. Importantly, genetic or pharmacological inhibition of dAlk rescued the reduced body size, adult learning deficits, and Extracellular-Regulated-Kinase (ERK) overactivation dNf1 mutant phenotypes. These results identify dAlk as an upstream activator of dNf1-regulated Ras signaling responsible for several dNf1 defects, and they implicate human Alk as a potential therapeutic target in NF1.

Neurofibromatosis-1 (NF1) syndrome is a common (1/3,000 births) genetic disorder affecting multiple organ systems, including the nervous system. Its clinical features include short stature, learning disabilities, and several types of benign and malignant tumors. NF1 is caused by mutations that inactivate the NF1 gene, a crucial negative regulator of Ras signaling. Although unregulated Ras signaling is a hallmark of NF1, the specific Ras signaling pathways responsible for disease development remain largely unknown. The Drosophila and human Nf1 genes are highly conserved; and, as in patients, mutant flies are smaller than usual and present deficient learning. Here, we identified the Drosophila Receptor Tyrosine Kinase dAlk as a negative regulator of organismal growth and olfactory learning. We show that excessive dAlk activation results in growth and learning defects similar to those of Nf1 mutants. Genetic suppression studies and pharmacological inhibition indicate dAlk as a critical upstream activator of Nf1-regulated neuronal Ras/ERK signals that contribute to size determination and learning. Importantly, our results strongly suggest that Alk represents a novel, highly specific, and promising therapeutic target in human NF1.

The novel chemical entity YTR107 inhibits recruitment of nucleophosmin to sites of DNA damage, suppressing repair of DNA double-strand breaks and enhancing radiosensitization

PURPOSE

Radiation therapy continues to be an important therapeutic strategy for providing definitive local/regional control of human cancer. However, oncogenes that harbor driver mutations and/or amplifications can compromise therapeutic efficacy. Thus, there is a need for novel approaches that enhance the DNA damage produced by ionizing radiation.

EXPERIMENTAL DESIGN

A forward chemical genetic approach coupled with cell-based phenotypic screening of several tumor cell lines was used to identify a novel chemical entity (NCE) that functioned as a radiation sensitizer. Proteomics, comet assays, confocal microscopy, and immunoblotting were used to identify the biological target.

RESULTS

The screening process identified a 5-((N-benzyl-1H-indol-3-yl)-methylene)pyrimidine-2,4,6(1H,3H,5H)trione as an NCE that radiosensitized cancer cells expressing amplified and/or mutated RAS, ErbB, PIK3CA, and/or BRAF oncogenes. Affinity-based solid-phase resin capture followed by liquid chromatography/tandem mass spectrometry identified the chaperone nucleophosmin (NPM) as the NCE target. SiRNA suppression of NPM abrogated radiosensitization by the NCE. Confocal microscopy showed that the NCE inhibited NPM shuttling to radiation-induced DNA damage repair foci, and the analysis of comet assays indicated a diminished rate of DNA double-strand break repair.

CONCLUSION

These data support the hypothesis that inhibition of DNA repair due to inhibition of NPM shuttling increases the efficacy of DNA-damaging therapeutic strategies.

Structure based drug design of crizotinib (PF-02341066), a potent and selective dual inhibitor of mesenchymal-epithelial transition factor (c-MET) kinase and anaplastic lymphoma kinase (ALK)

Because of the critical roles of aberrant signaling in cancer, both c-MET and ALK receptor tyrosine kinases are attractive oncology targets for therapeutic intervention. The cocrystal structure of 3 (PHA-665752), bound to c-MET kinase domain, revealed a novel ATP site environment, which served as the target to guide parallel, multiattribute drug design. A novel 2-amino-5-aryl-3-benzyloxypyridine series was created to more effectively make the key interactions achieved with 3. In the novel series, the 2-aminopyridine core allowed a 3-benzyloxy group to reach into the same pocket as the 2,6-dichlorophenyl group of 3 via a more direct vector and thus with a better ligand efficiency (LE). Further optimization of the lead series generated the clinical candidate crizotinib (PF-02341066), which demonstrated potent in vitro and in vivo c-MET kinase and ALK inhibition, effective tumor growth inhibition, and good pharmaceutical properties.

Selective therapeutic targeting of the anaplastic lymphoma kinase with liposomal siRNA induces apoptosis and inhibits angiogenesis in neuroblastoma

The anaplastic lymphoma kinase (ALK) is a tyrosine kinase receptor that is involved in the pathogenesis of different types of human cancers, including neuroblastoma (NB). In NB, ALK overexpression, or point mutations, are associated with poor prognosis and advanced stage disease. Inhibition of ALK kinase activity by small-molecule inhibitors in lung cancers carrying ALK translocations has shown therapeutic potential. However, secondary mutations may occur that, generate tumor resistance to ALK inhibitors. To overcome resistance to ALK inhibitors in NB, we adopted an alternative RNA interference (RNAi)-based therapeutic strategy that is able to knockdown ALK, regardless of its genetic status [mutated, amplified, wild-type (WT)]. NB cell lines, transduced by lentiviral short hairpin RNA (shRNA), showed reduced proliferation and increased apoptosis when ALK was knocked down. In mice, a nanodelivery system for ALK-specific small interfering RNA (siRNA), based on the conjugation of antibodies directed against the NB-selective marker GD(2) to liposomes, showed strong ALK knockdown in vivo in NB cells, which resulted in cell growth arrest, apoptosis, and prolonged survival. ALK knockdown was associated with marked reductions in vascular endothelial growth factor (VEGF) secretion, blood vessel density, and matrix metalloproteinases (MMPs) expression in vivo, suggesting a role for ALK in NB-induced neoangiogenesis and tumor invasion, confirming this gene as a fundamental oncogene in NB.

The neuroblastoma ALK(I1250T) mutation is a kinase-dead RTK in vitro and in vivo

Activating mutations in the kinase domain of anaplastic lymphoma kinase (ALK) have recently been shown to be an important determinant in the genetics of the childhood tumor neuroblastoma. Here we discuss an in-depth analysis of one of the reported gain-of-function ALK mutations-ALK(I1250T)-identified in the germ line DNA of one patient. Our analyses were performed in cell culture-based systems and subsequently confirmed in a Drosophila model. The results presented here indicate that the germ line ALK(I1250T) mutation is most probably not a determinant for tumor initiation or progression and, in contrast, seems to generate a kinase-dead mutation in the ALK receptor tyrosine kinase (RTK). Consistent with this, stimulation with agonist ALK antibodies fails to lead to stimulation of ALK(I1250T) and we were unable to detect tyrosine phosphorylation under any circumstances. In agreement, ALK(I1250T) is unable to activate downstream signaling pathways or to mediate neurite outgrowth, in contrast to the activated wild-type ALK receptor or the activating ALK(F1174S) mutant. Identical results were obtained when the ALK(I1250T) mutant was expressed in a Drosophila model, confirming the lack of activity of this mutant ALK RTK. We suggest that the ALK(I1250T) mutation leads to a kinase-dead ALK RTK, in stark contrast to assumed gain-of-function status, with significant implications for patients reported to carry this particular ALK mutation.

Anaplastic lymphoma kinase in human cancer

The receptor tyrosine kinases (RTKs) play a critical role, controlling cell proliferation, survival, and differentiation of normal cells. Their pivotal function has been firmly established in the pathogenesis of many cancers as well. The anaplastic lymphoma kinase (ALK), a transmembrane RTK, originally identified in the nucleophosmin (NPM)-ALK chimera of anaplastic large cell lymphoma, has emerged as a novel tumorigenic player in several human cancers. In this review, we describe the expression of the ALK-RTK, its related fusion proteins, and their molecular mechanisms of activation. Novel tailored strategies are briefly illustrated for the treatment of ALK-positive neoplasms.

Genome-wide association study of the child behavior checklist dysregulation profile

OBJECTIVE

A potentially useful tool for understanding the distribution and determinants of emotional dysregulation in children is a Child Behavior Checklist profile, comprising the Attention Problems, Anxious/Depressed, and Aggressive Behavior clinical subscales (CBCL-DP). The CBCL-DP indexes a heritable trait that increases susceptibility for later psychopathology, including severe mood problems and aggressive behavior. We have conducted a genome-wide association study of the CBCL-DP in children with attention-deficit/hyperactivity disorder (ADHD).

METHOD

Families were ascertained at Massachusetts General Hospital and University of California, Los Angeles. Genotyping was conducted with the Illumina Human1M or Human1M-Duo BeadChip platforms. Genome-wide association analyses were conducted with the MQFAM multivariate extension of PLINK.

RESULTS

CBCL data were available for 341 ADHD offspring from 339 ADHD affected trio families from the UCLA (N = 128) and the MGH (N = 213) sites. We found no genome-wide statistically significant associations but identified several plausible candidate genes among findings at p < 5E-05: TMEM132D, LRRC7, SEMA3A, ALK, and STIP1.

CONCLUSIONS

We found suggestive evidence for developmentally expressed genes operant in hippocampal dependent memory and learning with the CBCL-DP.

Hypoxia-microRNA-16 downregulation induces VEGF expression in anaplastic lymphoma kinase (ALK)-positive anaplastic large-cell lymphomas

The anaplastic lymphoma kinase (ALK), tyrosine kinase oncogene is implicated in a wide variety of cancers. In this study we used conditional onco-ALK (NPM-ALK and TPM3-ALK) mouse MEF cell lines (ALK+ fibroblasts) and transgenic models (ALK+ B-lymphoma) to investigate the involvement and regulation of angiogenesis in ALK tumor development. First, we observed that ALK expression leads to downregulation of miR-16 and increased Vascular Endothelial Growth Factor (VEGF) levels. Second, we found that modification of miR-16 levels in TPM3-ALK MEF cells greatly affected VEGF levels. Third, we demonstrated that miR-16 directly interacts with VEGF mRNA at the 3'-untranslated region and that the regulation of VEGF by miR-16 occurs at the translational level. Fourth, we showed that expression of both the ALK oncogene and hypoxia-induced factor 1α (HIF1α) is a prerequisite for miR-16 downregulation. Fifth, in vivo, miR-16 gain resulted in reduced angiogenesis and tumor growth. Finally, we highlighted an inverse correlation between the levels of miR-16 and VEGF in human NPM-ALK+ Anaplastic Large Cell Lymphomas (ALCL). Altogether, our results demonstrate, for the first time, the involvement of angiogenesis in ALK+ ALCL and strongly suggest an important role for hypoxia-miR-16 in regulating VEGF translation.

An evolutionary conserved role for anaplastic lymphoma kinase in behavioral responses to ethanol

Anaplastic lymphoma kinase (Alk) is a gene expressed in the nervous system that encodes a receptor tyrosine kinase commonly known for its oncogenic function in various human cancers. We have determined that Alk is associated with altered behavioral responses to ethanol in the fruit fly Drosophila melanogaster, in mice, and in humans. Mutant flies containing transposon insertions in dAlk demonstrate increased resistance to the sedating effect of ethanol. Database analyses revealed that Alk expression levels in the brains of recombinant inbred mice are negatively correlated with ethanol-induced ataxia and ethanol consumption. We therefore tested Alk gene knockout mice and found that they sedate longer in response to high doses of ethanol and consume more ethanol than wild-type mice. Finally, sequencing of human ALK led to the discovery of four polymorphisms associated with a low level of response to ethanol, an intermediate phenotype that is predictive of future alcohol use disorders (AUDs). These results suggest that Alk plays an evolutionary conserved role in ethanol-related behaviors. Moreover, ALK may be a novel candidate gene conferring risk for AUDs as well as a potential target for pharmacological intervention.

Behavioral choice between conflicting alternatives is regulated by a receptor guanylyl cyclase, GCY-28, and a receptor tyrosine kinase, SCD-2, in AIA interneurons of Caenorhabditis elegans

Animals facing conflicting sensory cues make a behavioral choice between competing alternatives through integration of the sensory cues. Here, we performed a genetic screen to identify genes important for the sensory integration of two conflicting cues, the attractive odorant diacetyl and the aversive stimulus Cu(2+), and found that the membrane-bound guanylyl cyclase GCY-28 and the receptor tyrosine kinase SCD-2 regulate the behavioral choice between these alternatives in Caenorhabditis elegans. The gcy-28 mutants and scd-2 mutants show an abnormal bias in the behavioral choice between the cues, although their responses to each individual cue are similar to those in wild-type animals. Mutants in a gene encoding a cyclic nucleotide gated ion channel, cng-1, also exhibit the defect in sensory integration. Molecular genetic analyses suggested that GCY-28 and SCD-2 regulate sensory integration in AIA interneurons, where the conflicting sensory cues may converge. Genetic ablation or hyperpolarization of AIA interneurons showed nearly the same phenotype as gcy-28 or scd-2 mutants in the sensory integration, although this did not affect the sensory response to each individual cue. In gcy-28 or scd-2 mutants, activation of AIA interneurons is sufficient to restore normal sensory integration. These results suggest that the activity of AIA interneurons regulates the behavioral choice between the alternatives. We propose that GCY-28 and SCD-2 regulate sensory integration by modulating the activity of AIA interneurons.

Screening of anaplastic lymphoma kinase rearrangement by immunohistochemistry in non-small cell lung cancer: correlation with fluorescence in situ hybridization

BACKGROUND

The use of a standard immunohistochemistry (IHC) assay to detect the anaplastic lymphoma kinase (ALK) protein in lung cancer is challenging. There are no universally accepted, evidence-based guidelines on identifying patients with ALK-rearranged lung cancer using IHC.

METHODS

We retrospectively reviewed 465 resected specimens of non-small cell lung cancer using a tissue microarray as a test set. ALK protein expression using IHC with 5A4 monoclonal antibody (Novocastra) and ALK gene rearrangement using fluorescence in situ hybridization (FISH) with dual-color break-apart probes (Abbott molecular) were examined. Immunoreactivity was scored as 0, 1, 2, or 3, and the results were compared with the FISH results. A diagnostic algorithm was derived from the correlation of the IHC and FISH results and applied to an additional 187 adenocarcinoma samples used as a validation set.

RESULTS

In the test set, ALK protein expression was detected in 40 patients (40/465, 8.6%), consisting of IHC scores of 1 (n = 14), 2 (n = 10), and 3 (n = 16), whereas 19 patients (19/453, 4.2%) were FISH-positive. All the FISH-positive patients were assigned IHC scores of 2 or 3. All the patients with ALK IHC scores of 3 were FISH-positive, those with scores of 0 or 1 were FISH-negative, and those with scores of 2 were FISH variable. In the validation set, ALK protein expression was detected in 14 patients (scores of 1, n = 2; scores of 2, n = 6; and scores of 3, n = 6), of which nine patients (9/187, 4.8%) were FISH-positive. All the patients with IHC scores of 0 or 1 were FISH-negative, and those with scores of 3 were FISH- positive. Among the patients with IHC scores of 2, three (3/6, 50%) were FISH-positive.

CONCLUSIONS

The sensitivity and specificity of IHC was 100% and 95.8%, respectively. These data supported an IHC scoring algorithm in which ALK IHC scores of 0, 1, or 3 were highly compatible with FISH results, and IHC scores of 2 were variable. Based on these findings, the IHC assay using the 5A4 antibody reliably detected non-small cell lung cancer with ALK rearrangement and may be useful as a screening method to identify these tumors.

Anaplastic lymphoma kinase (ALK) inhibitor response in neuroblastoma is highly correlated with ALK mutation status, ALK mRNA and protein levels

BACKGROUND

In pediatric neuroblastoma (NBL), high anaplastic lymphoma kinase (ALK) levels appear to be correlated with an unfavorable prognosis, regardless of ALK mutation status. This suggests a therapeutic role for ALK inhibitors in NBL patients. We examined the correlation between levels of ALK, phosphorylated ALK (pALK) and downstream signaling proteins and response to ALK inhibition in a large panel of both ALK mutated and wild type (WT) NBL cell lines.

METHODS

We measured protein levels by western blot and ALK inhibitor sensitivity (TAE684) by viability assays in 19 NBL cell lines of which 6 had a point mutation and 4 an amplification of the ALK gene.

RESULTS

ALK 220 kDa (p = 0.01) and ALK 140 kDa (p = 0.03) protein levels were higher in ALK mutant than WT cell lines. Response to ALK inhibition was significantly correlated with ALK protein levels (p < 0.01). ALK mutant cell lines (n = 4) were 14,9 fold (p < 0,01) more sensitive to ALK inhibition than eight WT cell lines.

CONCLUSION

NBL cell lines often express ALK at high levels and are responsive to ALK inhibitors. Mutated cell lines express ALK at higher levels, which may define their superior response to ALK inhibition.

Anaplastic thyroid cancers harbor novel oncogenic mutations of the ALK gene

Thyroid cancer is the most common endocrine cancer, and targeted approaches to treat it pose considerable interest. In this study, we report the discovery of ALK gene mutations in thyroid cancer that may rationalize clinical evaluation of anaplastic lymphoma kinase (ALK) inhibitors in this setting. In undifferentiated anaplastic thyroid cancer (ATC), we identified two novel point mutations, C3592T and G3602A, in exon 23 of the ALK gene, with a prevalence of 11.11%, but found no mutations in the matched normal tissues or in well-differentiated thyroid cancers. These two mutations, resulting in L1198F and G1201E amino acid changes, respectively, both reside within the ALK tyrosine kinase domain where they dramatically increased tyrosine kinase activities. Similarly, these mutations heightened the ability of ALK to activate the phosphatidylinositol 3-kinase (PI3K)/Akt and mitogen-activated protein (MAP) kinase pathways in established mouse cells. Further investigations showed that these two ALK mutants strongly promoted cell focus formation, anchorage-independent growth, and cell invasion. Similar oncogenic properties were observed in the neuroblastoma-associated ALK mutants K1062M and F1174L but not in wild-type ALK. Overall, our results reveal two novel gain-of-function mutations of ALK in certain ATCs, and they suggest efforts to clinically evaluate the use of ALK kinase inhibitors to treat patients who harbor ATCs with these mutations.

The connections between neural crest development and neuroblastoma

Neuroblastoma (NB), the most common extracranial solid tumor in childhood, is an extremely heterogeneous disease both biologically and clinically. Although significant progress has been made in identifying molecular and genetic markers for NB, this disease remains an enigmatic challenge. Since NB is thought to be an embryonal tumor that is derived from precursor cells of the peripheral (sympathetic) nervous system, understanding the development of normal sympathetic nervous system may highlight abnormal events that contribute to NB initiation. Therefore, this review focuses on the development of the peripheral trunk neural crest, the current understanding of how developmental factors may contribute to NB and on recent advances in the identification of important genetic lesions and signaling pathways involved in NB tumorigenesis and metastasis. Finally, we discuss how future advances in identification of molecular alterations in NB may lead to more effective, less toxic therapies, and improve the prognosis for NB patients.

Neuroblastoma-targeted nanoparticles entrapping siRNA specifically knockdown ALK

RNA interference molecules have some advantages as cancer therapeutics, including a proved efficacy on both wild-type (WT) and mutated transcripts and an extremely high sequence-specificity. The most significant hurdle to be overcome if exogenous small interfering RNAs (siRNA) is to be used therapeutically is the specific, effective, nontoxic delivery of siRNA to its intracellular site of action. At present, human applications are confined almost exclusively to targets within the liver, where the delivery systems naturally accumulate, and extra-hepatic targets remain a challenge. Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase that has recently been shown to contribute to the cell growth and progression of human neuroblastoma (NB). We investigated its potential as a therapeutic target in NB by generating anti-GD₂-targeted nanoparticles that carry ALK-directed siRNA, which are specifically and efficiently delivered to GD₂-expressing NB cells. Relative to free ALK-siRNA, anti-GD₂-targeted liposomal formulations of ALK-siRNA had low plasma clearance, increased siRNA stability, and improved binding, uptake, silencing and induction of cell death, and specificity for NB cells. In NB xenografts, intravenous (i.v.) injection of the targeted ALK-siRNA liposomes showed gene-specific antitumor activity with no side effects. ALK-selective siRNA entrapped in anti-GD₂-targeted nanoparticles is a promising new modality for NB treatment.

Aberrant anaplastic lymphoma kinase activity induces a p53 and Rb-dependent senescence-like arrest in the absence of detectable p53 stabilization

Anaplastic Lymphoma Kinase (ALK) is a receptor tyrosine kinase aberrantly expressed in a variety of tumor types, most notably in Anaplastic Large Cell Lymphoma (ALCL) where a chromosomal translocation generates the oncogenic fusion protein, Nucleophosmin-ALK (NPM-ALK). Whilst much is known regarding the mechanism of transformation by NPM-ALK, the existence of cellular defence pathways to prevent this pathological process has not been investigated. Employing the highly tractable primary murine embryonic fibroblast (MEF) system we show that cellular transformation is not an inevitable consequence of NPM-ALK activity but is combated by p53 and Rb. Activation of p53 and/or Rb by NPM-ALK triggers a potent proliferative block with features reminiscent of senescence. While loss of p53 alone is sufficient to circumvent NPM-ALK-induced senescence and permit cellular transformation, sole loss of Rb permits continued proliferation but not transformation due to p53-imposed restraints. Furthermore, NPM-ALK attenuates p53 activity in an Rb and MDM2 dependent manner but this activity is not sufficient to bypass senescence. These data indicate that senescence may constitute an effective barrier to ALK-induced malignancies that ultimately must be overcome for tumor development.

HuR-mediated control of C/EBPbeta mRNA stability and translation in ALK-positive anaplastic large cell lymphomas

The CCAAT/enhancer-binding protein β (C/EBPβ) plays a major role in the pathogenesis of anaplastic large cell lymphomas (ALCL) that express the nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) tyrosine kinase (ALK(+)). Although ALK-mediated C/EBPβ transcriptional activation has been reported, C/EBPβ mRNA possesses U- and AU-rich domains in its 3'-untranslated region (3'-UTR) that might be privileged targets for posttranscriptional control in ALK(+) ALCLs. The purpose of this study was to explore this possibility. By using human ALCL-derived cells and a murine model of ALK-transformed cells, we show that the AU-binding protein HuR binds to the 3'-UTR of C/EBPβ mRNA, as previously reported in adipocytes, and that NPM-ALK enhances this interaction. Interaction between HuR and C/EBPβ mRNA impacts on C/EBPβ gene expression at both the mRNA and protein levels. Indeed, C/EBPβ mRNA stability following HuR silencing is reduced and reaches the value observed in ALK-inactivated cells. Remarkably, HuR expression is not modified by NPM-ALK, but its association with actively translating polysomes is dramatically increased in ALK(+) cells. HuR/polysomes association diminishes when NPM-ALK activity is inhibited and is accompanied by a concomitant decrease of C/EBPβ mRNA translation. Finally, we show that HuR and NPM-ALK colocalized in cytoplasmic granules and HuR is phosphroylated on tyrosine residues in ALK(+) ALCL cells. Our study thus demonstrates that C/EBPβ is indeed regulated at the posttranscriptional level by HuR in ALK(+) cells, leading us to propose that part of NPM-ALK oncogenic properties relies on its ability to modify HuR properties in the cytoplasm and hence to alter expression of key actors of transformation.

Pathobiology of anaplastic large cell lymphoma

The authors revise the concept of anaplastic large cell lymphoma (ALCL) in the light of the recently updated WHO classification of Tumors of Hematopoietic and Lymphoid Tissues both on biological and clinical grounds. The main histological findings are illustrated with special reference to the cytological spectrum that is indeed characteristic of the tumor. The phenotype is reported in detail: the expression of the ALK protein as well as the chromosomal abnormalities is discussed with their potential pathogenetic implications. The clinical features of ALCL are presented by underlining the difference in terms of response to therapy and survival between the ALK-positive and ALK-negative forms. Finally, the biological rationale for potential innovative targeted therapies is presented.

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.

Anaplastic large cell lymphoma: twenty-five years of discovery

CONTEXT

The year 2010 commemorates the 25th year since the seminal publication by Karl Lennert and Harald Stein and others in Kiel, West Germany, describing an unusual large cell lymphoma now known as anaplastic large cell lymphoma (ALCL). Investigators at many universities and hospitals worldwide have contributed to our current in-depth understanding of this unique peripheral T-cell lymphoma, which in its systemic form, principally occurs in children and young adults.

OBJECTIVE

To summarize our current knowledge of the clinical and pathologic features of systemic and primary cutaneous ALCL. Particular emphasis is given to the biology and pathogenesis of ALCL.

DATA SOURCES

Search of the medical literature (Ovid MEDLINE In-Process & Other Non-Indexed Citations and Ovid MEDLINE: 1950 to Present [National Library of Medicine]) and more than 20 years of diagnostic experience were used as the source of data for review.

CONCLUSIONS

Based on immunostaining for activation antigen CD30 and the presence of dysregulation of the anaplastic lymphoma kinase gene (2p23), the diagnosis of ALCL has become relatively straightforward for most patients. Major strides have been made during the last decade in our understanding of the complex pathogenesis of ALCL. Constitutive NPM-ALK signaling has been shown to drive oncogenesis via an intricate network of redundant and interacting pathways that regulate cell proliferation, cell fate, and cytoskeletal modeling. Nevertheless, pathomechanistic, therapeutic, and diagnostic challenges remain that should be resolved as we embark on the next generation of discovery.