Retrovirus-Mediated Gene Transfer of NPM-ALK Causes Lymphoid Malignancy in Mice

Chimeric kinase ALK induces expression of NAMPT and selectively depends on this metabolic enzyme to sustain its own oncogenic function

As we show in this study, NAMPT, the key rate-limiting enzyme in the salvage pathway, one of the three known pathways involved in NAD synthesis, is selectively over-expressed in anaplastic T-cell lymphoma carrying oncogenic kinase NPM1::ALK (ALK + ALCL). NPM1::ALK induces expression of the NAMPT-encoding gene with STAT3 acting as transcriptional activator of the gene. Inhibition of NAMPT affects ALK + ALCL cells expression of numerous genes, many from the cell-signaling, metabolic, and apoptotic pathways. NAMPT inhibition also functionally impairs the key metabolic and signaling pathways, strikingly including enzymatic activity and, hence, oncogenic function of NPM1::ALK itself. Consequently, NAMPT inhibition induces cell death in vitro and suppresses ALK + ALCL tumor growth in vivo. These results indicate that NAMPT is a novel therapeutic target in ALK + ALCL and, possibly, other similar malignancies. Targeting metabolic pathways selectively activated by oncogenic kinases to which malignant cells become "addicted" may become a novel therapeutic approach to cancer, alternative or, more likely, complementary to direct inhibition of the kinase enzymatic domain. This potential therapy to simultaneously inhibit and metabolically "starve" oncogenic kinases may not only lead to higher response rates but also delay, or even prevent, development of drug resistance, frequently seen when kinase inhibitors are used as single agents.

Junction of the redox dynamic, orchestra of signaling, and altered metabolism in regulation of T- cell lymphoma

T-cell lymphoma is a hematologic neoplasm derived from the lymphoid lineage. It belongs to a diverse group of malignant disorders, mostly affecting the young population worldwide, that vary with respect to molecular features as well as genetic and clinical complexities. Cancer cells rewire the cellular metabolism, persuading it to meet new demands of growth and proliferation. Furthermore, the metabolic alterations and heterogeneity are aberrantly driven in cancer by a combination of genetic and non-genetic factors, including the tumor microenvironment. New insight into cancer metabolism highlights the importance of nutrient supply to tumor development and therapeutic responses. Importantly, oxidative stress due to an imbalance in the redox status of reactive species via exogenous and/or endogenous factors is closely related to multiple aspects of cancer. This alters the signaling pathways governed through the multiple intracellular signal transduction and transcription factors, leading to tumor progression. These oncogenic signaling molecules are regulated through different redox sensors, including nuclear factor-erythroid 2 related factor 2 (Nrf2), phase-II antioxidant enzyme, and NQO1 (NADPH quinone oxidoreductase (1). The existing understanding of the molecular mechanisms of T-cell lymphoma regulation through the cross-talk of redox sensors under the influence of metabolic vulnerability is not well explored. This review highlights the role of the redox dynamics, orchestra of signaling, and genetic regulation involved in T-cell lymphoma progression in addition to the challenges to their etiology, treatment, and clinical response in light of recent updates.

A kinase inhibitor screen reveals MEK1/2 as a novel therapeutic target to antagonize IGF1R-mediated antiestrogen resistance in ERα-positive luminal breast cancer

Antiestrogen resistance of breast cancer has been related to enhanced growth factor receptor expression and activation. We have previously shown that ectopic expression and subsequent activation of the insulin-like growth factor-1 receptor (IGF1R) or the epidermal growth factor receptor (EGFR) in MCF7 or T47D breast cancer cells results in antiestrogen resistance. In order to identify novel therapeutic targets to prevent this antiestrogen resistance, we performed kinase inhibitor screens with 273 different inhibitors in MCF7 cells overexpressing IGF1R or EGFR. Kinase inhibitors that antagonized antiestrogen resistance but are not directly involved in IGF1R or EGFR signaling were prioritized for further analyses. Various ALK (anaplastic lymphoma receptor tyrosine kinase) inhibitors inhibited cell proliferation in IGF1R expressing cells under normal and antiestrogen resistance conditions by preventing IGF1R activation and subsequent downstream signaling; the ALK inhibitors did not affect EGFR signaling. On the other hand, MEK (mitogen-activated protein kinase kinase)1/2 inhibitors, including PD0325901, selumetinib, trametinib and TAK733, selectively antagonized IGF1R signaling-mediated antiestrogen resistance but did not affect cell proliferation under normal growth conditions. RNAseq analysis revealed that MEK inhibitors PD0325901 and selumetinib drastically altered cell cycle progression and cell migration networks under IGF1R signaling-mediated antiestrogen resistance. In a group of 219 patients with metastasized ER+ breast cancer, strong pMEK staining showed a significant correlation with no clinical benefit of first-line tamoxifen treatment. We propose a critical role for MEK activation in IGF1R signaling-mediated antiestrogen resistance and anticipate that dual-targeted therapy with a MEK inhibitor and antiestrogen could improve treatment outcome.

Induction of Transcriptional Inhibitor HES1 and the Related Repression of Tumor-Suppressor TXNIP Are Important Components of Cell-Transformation Program Imposed by Oncogenic Kinase NPM-ALK

This study reports that hairy and enhancer of split homolog-1 (HES1), known to repress gene transcription in progenitor cells of several cell lineages, was strongly expressed in cells and tissues of T-cell lymphoma expressing the oncogenic chimeric tyrosine kinase nucleophosmin (NPM)-anaplastic lymphoma kinase [ALK; ALK⁺ T-cell lymphoma (TCL)]. The structural analysis of the Orange domain of HES1 indicated that HES1 formed a highly stable homodimer. Of note, repression of HES1 expression led to inhibition of ALK⁺ TCL cell growth in vivo. The expression of the HES1 gene was induced by NPM-ALK through activation of STAT3, which bound to the gene's promoter and induced the gene's transcription. NPM-ALK also directly phosphorylated HES1 protein. In turn, HES1 up-regulated and down-regulated in ALK⁺ TCL cells, the expression of numerous genes, protein products of which are involved in key cell functions, such as cell proliferation and viability. Among the genes inhibited by HES1 was thioredoxin-interacting protein (TXNIP), encoding a protein implicated in promotion of cell death in various types of cells. Accordingly, ALK⁺ TCL cells and tissues lacked expression of TXNIP, and its transcription was co-inhibited by HES1 and STAT3 in an NPM-ALK-dependent manner. Finally, the induced expression of TXNIP induced massive apoptotic cell death of ALK⁺ TCL cells. The results reveal a novel NPM-ALK-controlled pro-oncogenic regulatory network and document an important role of HES and TXNIP in the NPM-ALK-driven oncogenesis, with the former protein displaying oncogenic and the latter tumor suppressor properties.

NIPA (Nuclear Interaction Partner of ALK) Is Crucial for Effective NPM-ALK Mediated Lymphomagenesis

The NPM-ALK fusion kinase is expressed in 60% of systemic anaplastic large-cell lymphomas (ALCL). A Nuclear Interaction Partner of ALK (NIPA) was identified as a binding partner of NPM-ALK. To identify the precise role of NIPA for NPM-ALK-driven lymphomagenesis, we investigated various NPM-ALK+ cell lines and mouse models. Nipa deletion in primary mouse embryonic fibroblasts resulted in reduced transformation ability and colony formation upon NPM-ALK expression. Downregulating NIPA in murine NPM-ALK+ Ba/F3 and human ALCL cells decreased their proliferation ability and demonstrated synergistic effects of ALK inhibition and NIPA knockdown. Comprehensive in vivo analyses using short- and long-latency transplantation mouse models with NPM-ALK+ bone marrow (BM) revealed that Nipa deletion inhibited NPM-ALK-induced tumorigenesis with prolonged survival and reduced spleen colonies. To avoid off-target effects, we combined Nipa deletion and NPM-ALK expression exclusively in T cells using a lineage-restricted murine ALCL-like model resembling human disease: control mice died from neoplastic T-cell infiltration, whereas mice transplanted with Lck-CreTG/wtNipaflox/flox NPM-ALK+ BM showed significantly prolonged survival. Immunophenotypic analyses indicated a characteristic ALCL-like phenotype in all recipients but revealed fewer “stem-cell-like” features of Nipa-deficient lymphomas compared to controls. Our results identify NIPA as a crucial player in effective NPM-ALK-driven ALCL-like disease in clinically relevant murine and cell-based models.

Forward and Reverse Genetics of B Cell Malignancies: From Insertional Mutagenesis to CRISPR-Cas

Cancer genome sequencing has identified dozens of mutations with a putative role in lymphomagenesis and leukemogenesis. Validation of driver mutations responsible for B cell neoplasms is complicated by the volume of mutations worthy of investigation and by the complex ways that multiple mutations arising from different stages of B cell development can cooperate. Forward and reverse genetic strategies in mice can provide complementary validation of human driver genes and in some cases comparative genomics of these models with human tumors has directed the identification of new drivers in human malignancies. We review a collection of forward genetic screens performed using insertional mutagenesis, chemical mutagenesis and exome sequencing and discuss how the high coverage of subclonal mutations in insertional mutagenesis screens can identify cooperating mutations at rates not possible using human tumor genomes. We also compare a set of independently conducted screens from Pax5 mutant mice that converge upon a common set of mutations observed in human acute lymphoblastic leukemia (ALL). We also discuss reverse genetic models and screens that use CRISPR-Cas, ORFs and shRNAs to provide high throughput in vivo proof of oncogenic function, with an emphasis on models using adoptive transfer of ex vivo cultured cells. Finally, we summarize mouse models that offer temporal regulation of candidate genes in an in vivo setting to demonstrate the potential of their encoded proteins as therapeutic targets.

Engineering chromosome rearrangements in cancer

The identification of large chromosomal rearrangements in cancers has multiplied exponentially over the last decade. These complex and often rare genomic events have traditionally been challenging to study, in part owing to lack of tools that efficiently engineer disease-associated inversions, deletions and translocations in model systems. The emergence and refinement of genome editing technologies, such as CRISPR, have significantly expanded our ability to generate and interrogate chromosomal aberrations to better understand the networks that govern cancer growth. Here we review how existing technologies are employed to faithfully model cancer-associated chromosome rearrangements in the laboratory, with the ultimate goal of developing more accurate pre-clinical models of and therapeutic strategies for cancers driven by these genomic events.

Fusion transcripts FYN-TRAF3IP2 and KHDRBS1-LCK hijack T cell receptor signaling in peripheral T-cell lymphoma, not otherwise specified

Peripheral T-cell lymphoma (PTCL) is a heterogeneous group of non-Hodgkin lymphomas with poor prognosis. Up to 30% of PTCL lack distinctive features and are classified as PTCL, not otherwise specified (PTCL-NOS). To further improve our understanding of the genetic landscape and biology of PTCL-NOS, we perform RNA-sequencing of 18 cases and validate results in an independent cohort of 37 PTCL cases. We identify FYN-TRAF3IP2, KHDRBS1-LCK and SIN3A-FOXO1 as new in-frame fusion transcripts, with FYN-TRAF3IP2 as a recurrent fusion detected in 8 of 55 cases. Using ex vivo and in vivo experiments, we demonstrate that FYN-TRAF3IP2 and KHDRBS1-LCK activate signaling pathways downstream of the T cell receptor (TCR) complex and confer therapeutic vulnerability to clinically available drugs.

CRISPR genome editing of murine hematopoietic stem cells to create Npm1-Alk causes ALK+ lymphoma after transplantation

CRISPR/Cas9 genomic editing of wild-type hematopoietic stem cells generates Npm1-Alk, leading to ALK+ large-cell lymphomas in recipients. CD30+ postthymic T-cell lymphomas are polyclonal but transplantable to secondary recipients with long latency.

Emerging Roles of ALK in Immunity and Insights for Immunotherapy

Anaplastic lymphoma kinase (ALK) is mostly known for its oncogenic role in several human cancers. Recent evidences clearly indicate new roles of ALK and its genetic aberrations (e.g. gene rearrangements and mutations) in immune evasion, innate and cell-mediated immunity. New ALK-related immunotherapy approaches are demonstrating both preclinical and clinical promises. Here, we provide a timely review on the most updated laboratory and patient-related findings on ALK and immunity, which would grant us important insights for the development of novel ALK immunotherapies for ALK-altered cancers.

KRCA-0008 suppresses ALK-positive anaplastic large-cell lymphoma growth

Anaplastic lymphoma kinase (ALK), which belongs to the insulin receptor tyrosine kinase superfamily, plays an important role in nervous system development. Due to chromosomal translocations, point mutations, and gene amplification, constitutively activated ALK has been implicated in a variety of human cancers, including anaplastic large-cell lymphoma (ALCL), non-small cell lung cancer, and neuroblastoma. We evaluated the anti-cancer activity of the ALK inhibitor KRCA-0008 using ALCL cell lines that express NPM (nucleophosmin)-ALK. KRCA-0008 strongly suppressed the proliferation and survival of NPM-ALK-positive ALCL cells. Additionally, it induced G0/G1 cell cycle arrest and apoptosis by blocking downstream signals including STAT3, Akt, and ERK1/2. Tumor growth was strongly suppressed in mice inoculated with Karpas-299 tumor xenografts and orally treated with KRCA-0008 (50 mg/kg, BID) for 2 weeks. Our results suggest that KRCA-0008 will be useful in further investigations of ALK signaling, and may provide therapeutic opportunities for NPM-ALK-positive ALCL patients.

EML4-ALK-Positive Non-Small Cell Lung Cancer in a Patient Treated with Azathioprine for Ulcerative Colitis

EML4-ALK-positive lung cancer is a novel cancer entity associated with light or never smoking, younger age, and adenocarcinoma with acinar or signet-ring cell type histology. Another mutation of ALK with NPM, resulting in NPM-ALK fusion mutation, was described in patients with anaplastic large cell lymphoma (ALCL). It was subsequently reported in organ transplant recipients and patiens undergoing immunosuppressive therapy. We describe a case of lung cancer in a 36-year-old nonsmoking woman with ulcerative colitis treated with azathioprine, who was diagnosed with EML4-ALK-positive, metastatic lung cancer two months postpartum. Crizotinib 300 mg/day has been effective in maintaining response after chemotherapy failed. The resemblance of this case to ALK-positive ALCL in organ transplant recipients suggests that similar mechanisms may be responsible for the development of both ALK-positive lung cancer and ALCL in patients receiving immunosuppressive therapy.

Nucleophosmin-anaplastic lymphoma kinase: the ultimate oncogene and therapeutic target

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase physiologically expressed by fetal neural cells. However, aberrantly expressed ALK is involved in the pathogenesis of diverse malignancies, including distinct types of lymphoma, lung carcinoma, and neuroblastoma. The aberrant ALK expression in nonneural cells results from chromosomal translocations that create novel fusion proteins. These protein hybrids compose the proximal part of a partner gene, including its promoter region, and the distal part of ALK, including the coding sequence for the entire kinase domain. ALK was first identified in a subset of T-cell lymphomas with anaplastic large cell lymphoma (ALCL) morphology (ALK+ ALCL), the vast majority of which harbor the well-characterized nucleophosmin (NPM)-ALK fusion protein. NPM-ALK co-opts several intracellular signal transduction pathways, foremost being the STAT3 pathway, normally activated by cytokines from the interleukin-2 (IL-2) family to promote cell proliferation and to inhibit apoptosis. Many genes and proteins modulated by NPM-ALK are also involved in evasion of antitumor immune response, protection from hypoxia, angiogenesis, DNA repair, cell migration and invasiveness, and cell metabolism. In addition, NPM-ALK uses epigenetic silencing mechanisms to downregulate tumor suppressor genes to maintain its own expression. Importantly, NPM-ALK is capable of transforming primary human CD4⁺ T cells into immortalized cell lines indistinguishable from patient-derived ALK+ ALCL. Preliminary clinical studies indicate that inhibition of NPM-ALK induces long-lasting complete remissions in a large subset of heavily pretreated adult patients and the vast majority of children with high-stage ALK+ ALCL. Combining ALK inhibition with other novel therapeutic modalities should prove even more effective.

Challenging perspectives on the cellular origins of lymphoma

Both B and T lymphocytes have signature traits that set them apart from other cell types. They actively and repeatedly rearrange their DNA in order to produce a unique and functional antigen receptor, they have potential for massive clonal expansion upon encountering antigen via this receptor or its precursor, and they have the capacity to be extremely long lived as ‘memory’ cells. All three of these traits are fundamental to their ability to function as the adaptive immune response to infectious agents, but concurrently render these cells vulnerable to transformation. Thus, it is classically considered that lymphomas arise at a relatively late stage in a lymphocyte's development during the process of modifying diversity within antigen receptors, and when the cell is capable of responding to stimulus via its receptor. Attempts to understand the aetiology of lymphoma have reinforced this notion, as the most notable advances to date have shown chronic stimulation of the antigen receptor by infectious agents or self-antigens to be key drivers of these diseases. Despite this, there is still uncertainty about the cell of origin in some lymphomas, and increasing evidence that a subset arises in a more immature cell. Specifically, a recent study indicates that T-cell lymphoma, in particular nucleophosmin-anaplastic lymphoma kinase-driven anaplastic large cell lymphoma, may originate in T-cell progenitors in the thymus.

Exploring Missense Mutations in Tyrosine Kinases Implicated with Neurodegeneration

Protein kinases are one of the largest families of evolutionarily related proteins and the third most common protein class of human genome. All the protein kinases share the same structural organization. They are made up of an extracellular domain, transmembrane domain and an intra cellular kinase domain. Missense mutations in these kinases have been studied extensively and correlated with various neurological disorders. Individual mutations in the kinase domain affect the functions of protein. The enhanced or reduced expression of protein leads to hyperactivation or inactivation of the signalling pathways, resulting in neurodegeneration. Here, we present extensive analyses of missense mutations in the tyrosine kinase focussing on the neurodegenerative diseases encompassing structure function relationship. This is envisaged to enhance our understanding about the neurodegeneration and possible therapeutic measures.

Somatic Engineering of Oncogenic Chromosomal Rearrangements: A Perspective

The ability to engineer specific mutations in mice has proven essential to advancing our understanding of the molecular basis of cancer. Chromosomal rearrangements, a common and clinically relevant class of cancer-causing mutations, have however remained difficult to faithfully recapitulate in vivo The development of genetic tools for in vivo somatic genome editing has recently overcome this limitation and led to the generation of more sophisticated and accurate preclinical models of human cancers. Here, we review the potential applications of these new technologies to the study of tumor biology and discuss their advantages over more conventional strategies, their limitations, and the remaining challenges. Cancer Res; 76(17); 4918-23. ©2016 AACR.

Molecular mechanisms that underpin EML4-ALK driven cancers and their response to targeted drugs

A fusion between the EML4 (echinoderm microtubule-associated protein-like) and ALK (anaplastic lymphoma kinase) genes was identified in non-small cell lung cancer (NSCLC) in 2007 and there has been rapid progress in applying this knowledge to the benefit of patients. However, we have a poor understanding of EML4 and ALK biology and there are many challenges to devising the optimal strategy for treating EML4-ALK NSCLC patients. In this review, we describe the biology of EML4 and ALK, explain the main features of EML4-ALK fusion proteins and outline the therapies that target EML4-ALK. In particular, we highlight the recent advances in our understanding of the structures of EML proteins, describe the molecular mechanisms of resistance to ALK inhibitors and assess current thinking about combinations of ALK drugs with inhibitors that target other kinases or Hsp90.

An update of ALK inhibitors in human clinical trials

The proto-oncogenic ALK is a druggable receptor tyrosine kinase for cancer treatment. Two small molecule inhibitors of ALK, crizotinib and ceritinib, have been recently approved for the treatment of metastatic non-small-cell lung cancer, with marked improvement of progression-free survival of patients. Independent case reports also indicate their potential therapeutic activity in other ALK-rearranged cancers. Numerous single-agent and combination therapy trials are ongoing in lung and many other cancers. Results of these trials are greatly anticipated. Here, we summarize our current understanding of ALK signaling, genomic aberrations in cancer and emerging mechanisms of drug resistance. We will also provide a timely review on all ALK inhibitors and their current status of development in clinical settings.

Oncogenic role of miR-155 in anaplastic large cell lymphoma lacking the t(2;5) translocation

Anaplastic large cell lymphoma (ALCL) is a rare, aggressive, non-Hodgkin's lymphoma that is characterized by CD30 expression and disease onset in young patients. About half of ALCL patients bear the t(2;5)(p23;q35) translocation, which results in the formation of the nucleophosmin-anaplastic lymphoma tyrosine kinase (NPM-ALK) fusion protein (ALCL ALK(+)). However, little is known about the molecular features and tumour drivers in ALK-negative ALCL (ALCL ALK(-)), which is characterized by a worse prognosis. We found that ALCL ALK(-), in contrast to ALCL ALK(+), lymphomas display high miR-155 expression. Consistent with this, we observed an inverse correlation between miR-155 promoter methylation and miR-155 expression in ALCL. However, no direct effect of the ALK kinase on miR-155 levels was observed. Ago2 immunoprecipitation revealed miR-155 as the most abundant miRNA, and enrichment of target mRNAs C/EBPβ and SOCS1. To investigate its function, we over-expressed miR-155 in ALCL ALK(+) cell lines and demonstrated reduced levels of C/EBPβ and SOCS1. In murine engraftment models of ALCL ALK(-), we showed that anti-miR-155 mimics are able to reduce tumour growth. This goes hand-in-hand with increased levels of cleaved caspase-3 and high SOCS1 in these tumours, which leads to suppression of STAT3 signalling. Moreover, miR-155 induces IL-22 expression and suppresses the C/EBPβ target IL-8. These data suggest that miR-155 can act as a tumour driver in ALCL ALK(-) and blocking miR-155 could be therapeutically relevant. Original miRNA array data are to be found in the supplementary material (Table S1).

Anaplastic large cell lymphomas: ALK positive, ALK negative, and primary cutaneous

Anaplastic large cell lymphomas (ALCLs) comprise a group of CD30-positive non-Hodgkin lymphomas that generally are of T-cell origin and share common morphologic and phenotypic characteristics. The World Health Organization recognizes 3 entities: primary cutaneous ALCL (pcALCL), anaplastic lymphoma kinase (ALK)-positive ALCL, and, provisionally, ALK-negative ALCL. Despite overlapping pathologic features, these tumors differ in clinical behavior and genetics. pcALCL presents in the skin and, while it may involve locoregional lymph nodes, rarely disseminates. Outcomes typically are excellent. ALK-positive ALCL and ALK-negative ALCL are systemic diseases. ALK-positive ALCLs consistently have chromosomal rearrangements involving the ALK gene with varied gene partners, and generally have a favorable prognosis. ALK-negative ALCLs lack ALK rearrangements and their genetic and clinical features are more variable. A subset of ALK-negative ALCLs has rearrangements in or near the DUSP22 gene and has a favorable prognosis similar to that of ALK-positive ALCL. DUSP22 rearrangements also are seen in a subset of pcALCLs. In this review, we discuss the clinical, morphologic, phenotypic, genetic, and biological features of ALCLs.

Anaplastic lymphoma kinase-positive anaplastic large cell lymphoma: current and future perspectives in adult and paediatric disease

Anaplastic large cell lymphoma (ALCL) is a rare T-cell lymphoma seen in both adults and children. ALCL is associated with a characteristic chromosomal translocation, t(2;5)(p23;35) which fuses the anaplastic lymphoma kinase (ALK) gene on chromosome 2 with the nucleophosmin (NPM) gene on chromosome 5, resulting in a NPM-ALK fusion protein, ALK over-expression and constitutive tyrosine kinase activity. This aggressive lymphoma is more prevalent in males and can present with extranodal involvement (lung, skin and marrow infiltration) and haemophagocytic lymphohistocytosis. The long-term overall survival is approximately 70-90% in children and over 70% in adults. Staging systems and prognostic risk factors are different in both childhood and adult ALCL. Treatment in adults is typically anthracycline-based, with autologous stem cell transplantation (ASCT) salvaging patients in relapsed disease. There is evidence for ALL-like therapy or intensive, pulsed anthracycline-based induction in children. ASCT, allogeneic SCT and vinblastine maintenance are all considered reasonable options in relapsed childhood disease. The anti-CD30 immunoconjugate Brentuximab Vedotin and the specific ALK inhibitor Crizotinib are changing the treatment paradigm in ALCL (ALK-positive or negative) and ALK-positive ALCL respectively. Both agents have shown encouraging responses in relapsed ALCL. It remains to be seen how these novel agents are used, but it is very possible that they may improve overall responses and survival in both children and adults. This review highlights the presentation, histopathological features, prognostic factors, and evidence-based treatment approaches in the first line and relapsed setting in ALK-positive ALCL. The review concludes by discussing the novel approaches using Brentuximab and Crizotinib which are being tested in clinical trials.

Detection of t(2;5)(p23;q35) in anaplastic large-cell lymphoma by long-range nested polymerase chain reaction assay

Anaplastic large-cell lymphoma (ALCL) is characterized by molecular abnormalities involving ALK gene located at 2p23 which results in an overexpression of ALK. Nine different rearrangements of ALK gene have been reported; the t(2;5)(p23;q35) is the most common. The t(2;5) fuses the NPM gene at 5q35 with the ALK gene. NPM/ALK, as well as ALK activation via other molecular abnormalities, plays an important role in the pathogenesis of ALCL. The lack of tight clustering within the involved NPM and ALK genes precludes analysis using standard PCR methods. We describe a long-range nested PCR assay to detect NPM/ALK gene rearrangements.

Creating cancer translocations in human cells using Cas9 DSBs and nCas9 paired nicks

Recurrent chromosomal translocations are found in numerous tumor types, often leading to the formation and expression of fusion genes with oncogenic potential. Creating chromosomal translocations at the relevant endogenous loci, rather than ectopically expressing the fusion genes, opens new possibilities for better characterizing molecular mechanisms driving tumor formation. In this chapter, we describe methods to create cancer translocations in human cells. DSBs or paired nicks generated by either wild-type Cas9 or the Cas9 nickase, respectively, are used to induce translocations at the relevant loci. Using different PCR-based methods, we also explain how to quantify translocation frequency and to analyze breakpoint junctions in the cells of interest. In addition, PCR detection of translocations is used as a very sensitive method to detect off-target effects, which has general utility.

Models for mature T-cell lymphomas--a critical appraisal of experimental systems and their contribution to current T-cell tumorigenic concepts

Mature T-cell lymphomas/leukemias (MTCL) have been understudied lymphoid neoplasms that currently receive growing attention. Our historically rudimentary molecular understanding and dissatisfactory interventional success in this complex and for the most part poor-prognostic group of tumors is only slightly improving. A major limiting aspect in further progress in these rare neoplasms is the lack of suitable model systems that would substantially facilitate pathogenic studies and pre-clinical drug evaluations. Such representations of MTCL have thus far not been systematically appraised. We therefore provide an overview on existing models and point out their particular advantages and limitations in the context of the specific scientific questions. After addressing issues of species-specific differences and classifications, we summarize data on MTCL cell lines of human as well as murine origin, on murine strain predispositions to MTCL, on available models of genetically engineered mice, and on transplant systems. From an in-silico meta-analysis of available primary data of gene expression profiles on human MTCL we cross-reference genes reported to transform T-cells in mice and reflect on their general vs entity-restricted relevance and on target-promoter influences. Overall, we identify the urgent need for new models of higher fidelity to human MTCL with respect to their increasingly recognized diversity and to predictions of drug response.

The potent oncogene NPM-ALK mediates malignant transformation of normal human CD4(+) T lymphocytes

With this study we have demonstrated that in vitro transduction of normal human CD4(+) T lymphocytes with NPM-ALK results in their malignant transformation. The transformed cells become immortalized and display morphology and immunophenotype characteristic of patient-derived anaplastic large-cell lymphomas. These unique features, which are strictly dependent on NPM-ALK activity and expression, include perpetual cell growth, proliferation, and survival; activation of the key signal transduction pathways STAT3 and mTORC1; and expression of CD30 (the hallmark of anaplastic large-cell lymphoma) and of immunosuppressive cytokine IL-10 and cell-surface protein PD-L1/CD274. Implantation of NPM-ALK-transformed CD4(+) T lymphocytes into immunodeficient mice resulted in formation of tumors indistinguishable from patients' anaplastic large-cell lymphomas. Our findings demonstrate that the key aspects of human carcinogenesis closely recapitulating the features of the native tumors can be faithfully reproduced in vitro when an appropriate oncogene is used to transform its natural target cells; this in turn points to the fundamental role in malignant cell transformation of potent oncogenes expressed in the relevant target cells. Such transformed cells should permit study of the early stages of carcinogenesis, and in particular the initial oncogene-host cell interactions. This experimental design could also be useful for studies of the effects of early therapeutic intervention and likely also the mechanisms of malignant progression.

Malignant transformation of CD4+ T lymphocytes mediated by oncogenic kinase NPM/ALK recapitulates IL-2-induced cell signaling and gene expression reprogramming

Anaplastic lymphoma kinase (ALK), physiologically expressed only by nervous system cells, displays a remarkable capacity to transform CD4(+) T lymphocytes and other types of nonneural cells. In this study, we report that activity of nucleophosmin (NPM)/ALK chimeric protein, the dominant form of ALK expressed in T cell lymphomas (TCLs), closely resembles cell activation induced by IL-2, the key cytokine supporting growth and survival of normal CD4(+) T lymphocytes. Direct comparison of gene expression by ALK(+) TCL cells treated with an ALK inhibitor and IL-2-dependent ALK(-) TCL cells stimulated with the cytokine revealed a very similar, albeit inverse, gene-regulation pattern. Depending on the analysis method, up to 67% of the affected genes were modulated in common by NPM/ALK and IL-2. Based on the gene expression patterns, Jak/STAT- and IL-2-signaling pathways topped the list of pathways identified as affected by both IL-2 and NPM/ALK. The expression dependence on NPM/ALK and IL-2 of the five selected genes-CD25 (IL-2Rα), Egr-1, Fosl-1, SOCS3, and Irf-4-was confirmed at the protein level. In both ALK(+) TCL and IL-2-stimulated ALK(-) TCL cells, CD25, SOCS3, and Irf-4 genes were activated predominantly by the STAT5 and STAT3 transcription factors, whereas transcription of Egr-1 and Fosl-1 was induced by the MEK-ERK pathway. Finally, we found that Egr-1, a protein not associated previously with either IL-2 or ALK, contributes to the cell proliferation. These findings indicate that NPM/ALK transforms the target CD4(+) T lymphocytes, at least in part, by using the pre-existing, IL-2-dependent signaling pathways.

ALK as a paradigm of oncogenic promiscuity: different mechanisms of activation and different fusion partners drive tumors of different lineages

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase protein implicated in a variety of hematological malignancies and solid tumors. Since the identification of the ALK gene in 1994 as the target of the t(2;5) chromosomal translocation in anaplastic large cell lymphoma, ALK has been proven a remarkably promiscuous oncogene. ALK contributes to the development of a notable assortment of tumor types from different lineages, including hematolymphoid, mesenchymal, epithelial and neural tumors, through a variety of genetic mechanisms: gene fusions, activating point mutations, and gene amplification. Recent developments led to significant diagnostic and therapeutic advances, including efficient diagnostic tests and ALK-targeting agents readily available in the clinical setting. This review addresses some therapeutic considerations of ALK-targeted agents and the biologic implications of ALK oncogenic promiscuity, but the main points discussed are: 1) the variety of mechanisms that result in activation of the ALK oncogene, with emphasis on the promiscuous partnerships demonstrated in chromosomal rearrangements; 2) the diversity of tumor types of different lineages in which ALK has been implicated as a pathogenic driver; and 3) the different diagnostic tests available to identify ALK-driven tumors, and their respective indications.

ALK-positive large B-cell lymphomas express a terminal B-cell differentiation program and activated STAT3 but lack MYC rearrangements

ALK-positive large B-cell lymphoma is an aggressive lymphoid neoplasm characterized by a monomorphic proliferation of immunoblast-like cells expressing a plasmablastic phenotype and carrying ALK rearrangements. MYC rearrangements are frequent in plasmablastic lymphomas, advanced plasma cell myelomas and a subgroup of diffuse large B-cell lymphomas, but their presence in ALK-positive large B-cell lymphomas is unknown. MYC expression is downregulated by BLIMP1, a master modulator of plasma cell differentiation. BLIMP1 and MYC are upregulated by STAT3, a signal transducer activated by ALK. To determine the role of BLIMP1, MYC and STAT3 in the pathogenesis of ALK-positive large B-cell lymphomas, we investigated MYC rearrangement and the expression of MYC, phosphorylated STAT3, BLIMP1, PAX5 and XBP1 in 12 ALK-positive large B-cell lymphomas. All cases expressed ALK with a granular cytoplasmic pattern. Nine cases had a split signal consistent with an ALK rearrangement. Three additional cases showed a deletion of the 5' or 3' end of the ALK probe consistent with cryptic translocation. PAX5 was virtually negative in all cases tested, whereas BLIMP1 was expressed in all tumors and XBP1 in 11 of 12. Phosphorylated STAT3 was observed in all cases with a strong and diffuse nuclear pattern. MYC rearrangements were not identified in any tumor, but MYC gains and amplification were detected in six cases and one case, respectively. MYC protein was expressed in all tumors independently of MYC gene alterations. These results indicate that ALK-positive large B-cell lymphomas express a complete plasmablastic differentiation program but, contrary to plasmablastic lymphomas, do not have MYC rearrangements. STAT3 is constantly activated and may be an alternative mechanism to promote MYC expression in these tumors. The relevance of the ALK/STAT3 pathway in the pathogenesis of ALK-positive large B-cell lymphomas may offer an attractive target for new therapies.

Beyond NPM-anaplastic lymphoma kinase driven lymphomagenesis: alternative drivers in anaplastic large cell lymphoma

PURPOSE OF REVIEW

Anaplastic large cell lymphomas (ALCLs) are rare entities whose somatic genetic lesions have been identified only in a subset of patients. Thus, an integrated and massive discovery programme is required to define their tumourigenic alterations and to design more successful tailored therapies.

RECENT FINDINGS

The discovery of anaplastic lymphoma kinase (ALK) fusions has provided the basis for the characterization of distinct subsets among ALCL patients. Although the oncogenic addiction of ALK signalling is proven, the tumorigenic contribution of coactivating lesions is still missing. As ALK- and ALK+ share common signatures, it is plausible that analogous mechanisms of transformation may be operating in both subsets, as confirmed by the dysregulated activation of c-MYC, RAS and NFκB, and the loss of Blimp-1 and p53/p63 axis. Nonetheless, recurrent genetic alterations for ALK- ALCL or refractory leukaemic ALK+ ALCL are lacking. Moreover, although conventional chemotherapies (anthracycline-based) are most successful, that is in ALK+ ALCL patients, the implementation of ALK inhibitors or of anti-CD30 based treatments provides innovative solutions, particularly in paediatric ALK+ ALCL and in chemorefractory/relapsed patients.

SUMMARY

The complete portrayal of the landscape of genetic alterations in ALCL will dictate the development of innovative chemotherapeutic and targeted therapies that will fit most with the molecular and clinical profiling of individual patients.

Cancer translocations in human cells induced by zinc finger and TALE nucleases

Chromosomal translocations are signatures of numerous cancers and lead to expression of fusion genes that act as oncogenes. The wealth of genomic aberrations found in cancer, however, makes it challenging to assign a specific phenotypic change to a specific aberration. In this study, we set out to use genome editing with zinc finger (ZFN) and transcription activator-like effector (TALEN) nucleases to engineer, de novo, translocation-associated oncogenes at cognate endogenous loci in human cells. Using ZFNs and TALENs designed to cut precisely at relevant translocation breakpoints, we induced cancer-relevant t(11;22)(q24;q12) and t(2;5)(p23;q35) translocations found in Ewing sarcoma and anaplastic large cell lymphoma (ALCL), respectively. We recovered both translocations with high efficiency, resulting in the expression of the EWSR1–FLI1 and NPM1–ALK fusions. Breakpoint junctions recovered after ZFN cleavage in human embryonic stem (ES) cell–derived mesenchymal precursor cells fully recapitulated the genomic characteristics found in tumor cells from Ewing sarcoma patients. This approach with tailored nucleases demonstrates that expression of fusion genes found in cancer cells can be induced from the native promoter, allowing interrogation of both the underlying mechanisms and oncogenic consequences of tumor-related translocations in human cells. With an analogous strategy, the ALCL translocation was reverted in a patient cell line to restore the integrity of the two participating chromosomes, further expanding the repertoire of genomic rearrangements that can be engineered by tailored nucleases.

NPM-ALK up-regulates iNOS expression through a STAT3/microRNA-26a-dependent mechanism

NPM-ALK chimeric oncogene is aberrantly expressed in an aggressive subset of T-cell lymphomas that frequently occurs in children and young adults. The mechanisms underlying the oncogenic effects of NPM-ALK are not completely elucidated. Inducible nitric oxide synthase (iNOS) promotes the survival and maintains the malignant phenotype of cancer cells by generating NO, a highly active free radical. We tested the hypothesis that iNOS is deregulated in NPM-ALK(+) T-cell lymphoma and promotes the survival of this lymphoma. In line with this possibility, an iNOS inhibitor and NO scavenger decreased the viability, adhesion, and migration of NPM-ALK(+) T-cell lymphoma cells, and an NO donor reversed these effects. Moreover, the NO donor salvaged the viability of lymphoma cells treated with ALK inhibitors. In further support of an important role of iNOS, we found iNOS protein to be highly expressed in NPM-ALK(+) T-cell lymphoma cell lines and in 79% of primary tumours but not in human T lymphocytes. Although expression of iNOS mRNA was identified in NPM-ALK(+) T-cell lymphoma cell lines and tumours, iNOS mRNA was remarkably elevated in T lymphocytes, suggesting post-transcriptional regulation. Consistently, we found that miR-26a contains potential binding sites and interacts with the 3'-UTR of iNOS. In addition, miR-26a was significantly decreased in NPM-ALK(+) T-cell lymphoma cell lines and tumours compared with T lymphocytes and reactive lymph nodes. Restoration of miR-26a in lymphoma cells abrogated iNOS protein expression and decreased NO production and cell viability, adhesion, and migration. Importantly, the effects of miR-26a were substantially attenuated when the NO donor was simultaneously used to treat lymphoma cells. Our investigation of the mechanisms underlying the decrease in miR-26a in this lymphoma revealed novel evidence that STAT3, a major downstream substrate of NPM-ALK tyrosine kinase activity, suppresses MIR26A1 gene expression.

ALK alterations in adult renal cell carcinoma: frequency, clinicopathologic features and outcome in a large series of consecutively treated patients

Chromosomal rearrangements involving the anaplastic lymphoma kinase gene (ALK) at 2p23 result in fusion with various partner genes leading to aberrant production of oncogenic protein products in multiple tumor types. Recently, the ALK protein inhibitor crizotinib was shown to be an effective therapy in patients with ALK-rearranged non-small cell lung cancer. The goal of this study was to determine the frequency of ALK alterations in adult renal cell carcinoma (RCC) and define associated clinicopathologic features and outcome. RCCs from a cohort of 534 consecutive surgically treated adult patients were analyzed for alterations of ALK by fluorescence in situ hybridization. ALK rearrangements were identified in 2 of 534 (<1%) RCCs. Both showed similar histologic features and the patients had a poor outcome. ALK copy number gain was identified in 54 (10%) RCCs. In clear cell type RCC (CCRCC), ALK copy number gain was significantly associated with tumor size (P=0.02) and nuclear grade (P<0.001), and with a worse 10-year cancer-specific survival vs similar patients lacking ALK copy number gain (P=0.03). ALK rearrangement is rare in adult RCC but may be associated with distinct histological features and poor outcome. Another potential mechanism to elevate ALK expression, increased ALK gene copy number, was observed in 10% of adult CCRCC, where it is associated with a higher tumor grade and poorer outcome. Additional studies are necessary to determine whether patients RCCs with ALK rearrangement and/or those with an increase in ALK copy number would benefit from ALK inhibitor treatment.

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.

The R1275Q neuroblastoma mutant and certain ATP-competitive inhibitors stabilize alternative activation loop conformations of anaplastic lymphoma kinase

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase that, when genetically altered by mutation, amplification, chromosomal translocation or inversion, has been shown to play an oncogenic role in certain cancers. Small molecule inhibitors targeting the kinase activity of ALK have proven to be effective therapies in certain ALK-driven malignancies and one such inhibitor, crizotinib, is now approved for the treatment of EML4-ALK-driven, non-small cell lung cancer. In neuroblastoma, activating point mutations in the ALK kinase domain can drive disease progression, with the two most common mutations being F1174L and R1275Q. We report here crystal structures of the ALK kinase domain containing the F1174L and R1275Q mutations. Also included are crystal structures of ALK in complex with novel small molecule ALK inhibitors, including a classic type II inhibitor, that stabilize previously unobserved conformations of the ALK activation loop. Collectively, these structures illustrate a different series of activation loop conformations than has been observed in previous ALK crystal structures and provide insight into the activating nature of the R1275Q mutation. The novel active site topologies presented here may also aid the structure-based drug design of a new generation of ALK inhibitors.

T-cell receptor diversity prevents T-cell lymphoma development

Mature T-cell lymphomas (MTCLs) have an extremely poor prognosis and are much less frequent than immature T-cell leukemias. This suggests that malignant outgrowth of mature T lymphocytes is well controlled. Indeed, in a previous study we found that mature T cells are resistant to transformation with known T-cell oncogenes. Here, however, we observed that T-cell receptor (TCR) mono-/oligoclonal mature T cells from TCR transgenic (tg) mice (OT-I, P14) expressing the oncogenes NPM/ALK or ΔTrkA readily developed MTCLs in T-cell-deficient recipients. Analysis of cell surface markers largely ruled out that TCR tg lymphomas were derived from T-cell precursors. Furthermore, cotransplanted non-modified TCR polyclonal T cells suppressed malignant outgrowth of oncogene expressing TCR tg T lymphocytes. A dominant role of an anti-leukemic immune response or Tregs in the control of MTCLs seems unlikely as naïve T cells derived from oncogene expressing stem cells, which should be tolerant to leukemic antigens, as well as purified CD4 and CD8 were resistant to transformation. However, our results are in line with a model in which homeostatic mechanisms that stabilize the diversity of the normal T-cell repertoire, for example, clonal competition, also control the outgrowth of potentially malignant T-cell clones. This study introduces a new innate mechanism of lymphoma control.

Case report: A unique pediatric case of a primary CD8 expressing ALK-1 positive anaplastic large cell lymphoma of skeletal muscle

Primary involvement of skeletal muscle is a very rare event in ALK-1 positive anaplastic large cell lymphoma (ALCL). We describe a case of a 10-year old boy presenting with a three week history of pain and a palpable firm swelling at the dorsal aspect of the left thigh. Histological examination of the lesion revealed a tumoral and diffuse polymorphic infiltration of the muscle by large lymphoid cells. Tumor cells displayed eccentric, lobulated "horse shoe" or "kidney-shape" nuclei. The cells showed immunohistochemical positivity for CD30, ALK-1, CD2, CD3, CD7, CD8, and Perforin. Fluorescence in situ hybridization analysis revealed a characteristic rearrangement of the ALK-1 gene in 2p23 leading to the diagnosis of ALK-1 positive ALCL. Chemotherapy according to the ALCL-99-NHL-BFM protocol was initiated and resulted in a complete remission after two cycles. This case illustrates the unusual presentation of a pediatric ALCL in soft tissue with a good response to chemotherapy.

Determining the contribution of NPM1 heterozygosity to NPM-ALK-induced lymphomagenesis

Heterozygous expression of Nucleophosmin (NPM1) predisposes to hematological malignancies in the mouse and cooperates with Myc in lymphomagenesis. NPM1 is therefore regarded as a haploinsufficient tumor suppressor. Heterozygous loss of NPM1 occurs as a result of the t(2;5), which generates the oncogenic fusion tyrosine kinase, NPM-anaplastic lymphoma kinase (ALK), a molecule underlying the pathogenesis of anaplastic large cell lymphoma (ALCL). Given the aforementioned role of NPM1 as a tumor suppressor, we hypothesized that NPM1 heterozygosity would cooperate with NPM-ALK in lymphomagenesis. In the event, we observed no difference in tumor latency, incidence or phenotype in NPM-ALK-transgenic mice heterozygous for NPM1 relative to transgenic mice expressing both NPM1 alleles. We propose that although the t(2;5) simultaneously reduces NPM1 allelic dosage and creates the NPM-ALK fusion protein, the two events do not cooperate in the pathogenesis of ALCL in our mouse model. These data indicate that a tumor-suppressive role for NPM1 may depend on cellular and/or genetic context.

Targeting oncogenic ALK: a promising strategy for cancer treatment

Recently, the anaplastic lymphoma kinase (ALK) has been found to be altered in several solid and hematologic tumors. Novel drugs targeting this tyrosine kinase receptor are under development, and early clinical trials are showing promising activity in non-small cell lung cancer patients with ALK+ tumors. Here, we review the structure and function of the ALK receptor, the mechanisms associated with its deregulation in cancer, methods for ALK detection in tumor samples, its potential as a new marker for candidate patient selection for tailored therapy, and novel drugs under development that target ALK.

Anaplastic large-cell lymphoma

The concept of anaplastic large-cell lymphoma (ALCL) has changed over the years because of a stream of new information and novel understanding regarding the cell of origin, biology, genetics, and clinical features of these neoplasms. This new information has led to the current classification proposed by the expert reviewers of the World Health Organization. The objective of this review is to present the most updated information on the cytologic and histologic features of these entities, with a special reference to diagnostic algorithms. A detailed description of the genetic aberrations and the pathogenetic mechanisms leading to transformation is presented. The clinical features of ALCL and novel tailored strategies are briefly illustrated.

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.

IL-2R common gamma-chain is epigenetically silenced by nucleophosphin-anaplastic lymphoma kinase (NPM-ALK) and acts as a tumor suppressor by targeting NPM-ALK

Anaplastic lymphoma kinase (ALK), physiologically expressed only by certain neural cells, becomes highly oncogenic, when aberrantly expressed in nonneural tissues as a fusion protein with nucleophosphin (NPM) and other partners. The reason why NPM-ALK succeeds in transforming specifically CD4(+) T lymphocytes remains unknown. The IL-2R common γ-chain (IL-2Rγ) is shared by receptors for several cytokines that play key roles in the maturation and growth of normal CD4(+) T lymphocytes and other immune cells. We show that IL-2Rγ expression is inhibited in T-cell lymphoma cells expressing NPM-ALK kinase as a result of DNA methylation of the IL-2Rγ gene promoter. IL-2Rγ promoter methylation is induced in malignant T cells by NPM-ALK. NPM-ALK acts through STAT3, a transcription factor that binds to the IL-2Rγ gene promoter and enhances binding of DNA methyltransferases (DNMTs) to the promoter. In addition, STAT3 suppresses expression of miR-21, which selectively inhibits DNMT1 mRNA expression. Reconstitution of IL-2Rγ expression leads to loss of the NPM-ALK protein and, consequently, apoptotic cell death of the lymphoma cells. These results demonstrate that the oncogenic tyrosine kinase NPM-ALK induces epigenetic silencing of the IL-2Rγ gene and that IL-2Rγ acts as a tumor suppressor by reciprocally inhibiting expression of NPM-ALK.

Fusion tyrosine kinase NPM-ALK Deregulates MSH2 and suppresses DNA mismatch repair function novel insights into a potent oncoprotein

The fusion tyrosine kinase NPM-ALK is central to the pathogenesis of ALK-positive anaplastic large cell lymphoma (ALK(+)ALCL). We recently identified that MSH2, a key DNA mismatch repair (MMR) protein integral to the suppression of tumorigenesis, is an NPM-ALK-interacting protein. In this study, we found in vitro evidence that enforced expression of NPM-ALK in HEK293 cells suppressed MMR function. Correlating with these findings, six of nine ALK(+)ALCL tumors displayed evidence of microsatellite instability, as opposed to none of the eight normal DNA control samples (P = 0.007, Student's t-test). Using co-immunoprecipitation, we found that increasing levels of NPM-ALK expression in HEK293 cells resulted in decreased levels of MSH6 bound to MSH2, whereas MSH2·NPM-ALK binding was increased. The NPM-ALK·MSH2 interaction was dependent on the activation/autophosphorylation of NPM-ALK, and the Y191 residue of NPM-ALK was a crucial site for this interaction and NPM-ALK-mediated MMR suppression. MSH2 was found to be tyrosine phosphorylated in the presence of NPM-ALK. Finally, NPM-ALK impeded the expected DNA damage-induced translocation of MSH2 out of the cytoplasm. To conclude, our data support a model in which the suppression of MMR by NPM-ALK is attributed to its ability to interfere with normal MSH2 biochemistry and function.

Evaluation of EML4-ALK fusion proteins in non-small cell lung cancer using small molecule inhibitors

The echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase (EML4-ALK) fusion gene resulting from an inversion within chromosome 2p occurs in approximately 5% of non-small cell lung cancer and is mutually exclusive with Ras and EGFR mutations. In this study, we have used a potent and selective ALK small molecule inhibitor, NPV-TAE684, to assess the oncogenic role of EML4-ALK in non-small cell lung cancer (NSCLC). We show here that TAE684 inhibits proliferation and induces cell cycle arrest, apoptosis, and tumor regression in two NSCLC models that harbor EML4-ALK fusions. TAE684 inhibits EML4-ALK activation and its downstream signaling including ERK, AKT, and STAT3. We used microarray analysis to carry out targeted pathway studies of gene expression changes in H2228 NSCLC xenograft model after TAE684 treatment and identified a gene signature of EML4-ALK inhibition. The gene signature represents 1210 known human genes, and the top biologic processes represented by these genes are cell cycle, DNA synthesis, cell proliferation, and cell death. We also compared the effect of TAE684 with PF2341066, a c-Met and ALK small molecule inhibitor currently in clinical trial in cancers harboring ALK fusions, and demonstrated that TAE684 is a much more potent inhibitor of EML4-ALK. Our data demonstrate that EML4-ALK plays an important role in the pathogenesis of a subset of NSCLC and provides insight into the mechanism of EML4-ALK inhibition by a small molecule inhibitor.

The lymphoma-associated NPM-ALK oncogene elicits a p16INK4a/pRb-dependent tumor-suppressive pathway

Oncogene-induced senescence (OIS) is a barrier for tumor development. Oncogene-dependent DNA damage and activation of the ARF/p53 pathway play a central role in OIS and, accordingly, ARF and p53 are frequently mutated in human cancer. A number of leukemia/lymphoma-initiating oncogenes, however, inhibit ARF/p53 and only infrequently select for ARF or p53 mutations, suggesting the involvement of other tumor-suppressive pathways. We report that NPM-ALK, the initiating oncogene of anaplastic large cell lymphomas (ALCLs), induces DNA damage and irreversibly arrests the cell cycle of primary fibroblasts and hematopoietic progenitors. This effect is associated with inhibition of p53 and is caused by activation of the p16INK4a/pRb tumor-suppressive pathway. Analysis of NPM-ALK lymphomagenesis in transgenic mice showed p16INK4a-dependent accumulation of senescent cells in premalignant lesions and decreased tumor latency in the absence of p16INK4a. Accordingly, human ALCLs showed no expression of either p16INK4a or pRb. Up-regulation of the histone-demethylase Jmjd3 and de-methylation at the p16INK4a promoter contributed to the effect of NPM-ALK on p16INK4a, which was transcriptionally regulated. These data demonstrate that p16INK4a/pRb may function as an alternative pathway of oncogene-induced senescence, and suggest that the reactivation of p16INK4a expression might be a novel strategy to restore the senescence program in some tumors.

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.

Oncogenic mutations of ALK in neuroblastoma

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