ALKALs are in vivo ligands for ALK family receptor tyrosine kinases in the neural crest and derived cells

ALK inhibitors increase ALK expression and sensitize neuroblastoma cells to ALK.CAR-T cells

Selection of the best tumor antigen is critical for the therapeutic success of chimeric antigen receptor (CAR) T cells in hematologic malignancies and solid tumors. The anaplastic lymphoma kinase (ALK) receptor is expressed by most neuroblastomas while virtually absent in most normal tissues. ALK is an oncogenic driver in neuroblastoma and ALK inhibitors show promising clinical activity. Here, we describe the development of ALK.CAR-T cells that show potent efficacy in monotherapy against neuroblastoma with high ALK expression without toxicity. For neuroblastoma with low ALK expression, combination with ALK inhibitors specifically potentiates ALK.CAR-T cells but not GD2.CAR-T cells. Mechanistically, ALK inhibitors impair tumor growth and upregulate the expression of ALK, thereby facilitating the activity of ALK.CAR-T cells against neuroblastoma. Thus, while neither ALK inhibitors nor ALK.CAR-T cells will likely be sufficient as monotherapy in neuroblastoma with low ALK density, their combination specifically enhances therapeutic efficacy.

Myron Gordon Award Lecture 2023: Painting the neural crest: How studying pigment cells illuminates neural crest cell biology

It has been 30 (!!) years since I began working on zebrafish pigment cells, as a postdoc in the laboratory of Prof. Christiane Nüsslein-Volhard. There, I participated in the first large-scale mutagenesis screen in zebrafish, focusing on pigment cell mutant phenotypes. The isolation of colourless, shady, parade and choker mutants allowed us (as a postdoc in Prof. Judith Eisen's laboratory, and then in my own laboratory at the University of Bath since 1997) to pursue my ambition to address long-standing problems in the neural crest field. Thus, we have studied how neural crest cells choose individual fates, resulting in our recent proposal of a new, and potentially unifying, model which we call Cyclical Fate Restriction, as well as addressing how pigment cell patterns are generated. A key feature of our work in the last 10 years has been the use of mathematical modelling approaches to clarify our biological models and to refine our interpretations. None of this would have been possible without a hugely talented group of laboratory members and other collaborators from around the world-it has been, and I am sure will continue to be, a pleasure and privilege to work with you all!

Multifaceted Roles of ALK Family Receptors and Augmentor Ligands in Health and Disease: A Comprehensive Review

This review commemorates the 10-year anniversary of the discovery of physiological ligands Augα (Augmentor α; ALKAL2; Fam150b) and Augβ (Augmentor β; ALKAL1; Fam150a) for anaplastic lymphoma kinase (ALK) and leukocyte tyrosine kinase (LTK), previously considered orphan receptors. This manuscript provides an in-depth review of the biophysical and cellular properties of ALK family receptors and their roles in cancer, metabolism, pain, ophthalmology, pigmentation, central nervous system (CNS) function, and reproduction. ALK and LTK receptors are implicated in the development of numerous cancers, and targeted inhibition of their signaling pathways can offer therapeutic benefits. Additionally, ALK family receptors are involved in regulating body weight and metabolism, modulating pain signaling, and contributing to eye development and pigmentation. In the CNS, these receptors play a role in synapse modulation, neurogenesis, and various psychiatric pathologies. Lastly, ALK expression is linked to reproductive functions, with potential implications for patients undergoing ALK inhibitor therapy. Further research is needed to better understand the complex interactions of ALK family receptors and Aug ligands and to repurpose targeted therapy for a wide range of human diseases.

Negr1-Derived Peptides Trigger ALK Degradation and Halt Neuroblastoma Progression In Vitro and In Vivo

Neuroblastoma is among the most common childhood cancers. Neuroblastoma in advanced stages is one of the most intractable pediatric cancers, notwithstanding the recent therapeutic advances. ALK mutations are among the leading cause of hereditary neuroblastoma and account for more than 14% of the somatically acquired alterations. ALK kinase activity is currently one of the main targets for pharmacological strategies. However, evidence from ALK fusion-positive lung cancer studies has shown that resistance to ALK inhibition arises during the therapy, causing a relapse within several years. IgLONs are membrane-bound proteins involved in cell-to-cell adhesion. The expression of the IgLON family results altered in different cancers. We found that the IgLON member Negr1 is downregulated in neuroblastoma. The ectopic overexpression of Negr1 impairs neuroblastoma growth in vitro and in vivo. Negr1 exists as a GPI-anchored membrane-bound protein and as a soluble protein released upon metalloprotease cleavage. We generated and characterized a panel of Negr1-derived peptides. The treatment with Negr1 protein and derived peptides induce ALK downregulation and halt neuroblastoma progression in vitro and in vivo.

IGF1R Contributes to Cell Proliferation in ALK-Mutated Neuroblastoma with Preference for Activating the PI3K-AKT Signaling Pathway

Aberrant activation of anaplastic lymphoma kinase (ALK) by activating point mutation or amplification drives 5-12% of neuroblastoma (NB). Previous work has identified the involvement of the insulin-like growth factor 1 receptor (IGF1R) receptor tyrosine kinase (RTK) in a wide range of cancers. We show here that many NB cell lines exhibit IGF1R activity, and that IGF1R inhibition led to decreased cell proliferation to varying degrees in ALK-driven NB cells. Furthermore, combined inhibition of ALK and IGF1R resulted in synergistic anti-proliferation effects, in particular in ALK-mutated NB cells. Mechanistically, both ALK and IGF1R contribute significantly to the activation of downstream PI3K-AKT and RAS-MAPK signaling pathways in ALK-mutated NB cells. However, these two RTKs employ a differential repertoire of adaptor proteins to mediate downstream signaling effects. We show here that ALK signaling led to activation of the RAS-MAPK pathway by preferentially phosphorylating the adaptor proteins GAB1, GAB2, and FRS2, while IGF1R signaling preferentially phosphorylated IRS2, promoting activation of the PI3K-AKT pathway. Together, these findings reveal a potentially important role of the IGF1R RTK in ALK-mutated NB and that co-targeting of ALK and IGF1R may be advantageous in clinical treatment of ALK-mutated NB patients.

A narrative review of methods for the identification of ALK fusions in patients with non-small cell lung carcinoma

Background and Objective

This narrative review is intended to provide pragmatic knowledge of current methods for the search of anaplastic lymphoma kinase (ALK) fusions in patients with non-small cell lung carcinoma (NSCLC). This information is very timely, because a recent survey has identified that almost 50% of patients with advanced NSCLC were not candidates for targeted therapies because of biomarker testing issues.

Methods

PubMed was searched from January 1st, 2012 to February 28th, 2023 using the following keywords: "ALK" and "lung", including reviews and our own work.

Key Content and Findings

Testing rates have not reached 85% among patients' candidates to ALK inhibition. The advantages and disadvantages of the different analytical options [immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), real-time polymerase chain reaction and next-generation sequencing (NGS)] are discussed. The key factor for success in ALK testing is a deep understanding of the concept of "molecular redundancy". This notion has been recommended and endorsed by all the major professional organizations in the field and can be summarized as follows: "laboratories should ensure that test results that are unexpected, discordant, equivocal, or otherwise of low confidence are confirmed or resolved using an alternative method or sample". In-depth knowledge of the different ALK testing methodologies can help clinical and molecular tumor boards implement and maintain sensible algorithms for a rapid and effective detection of predictive biomarkers in patients with NSCLC.

Conclusions

Multimodality testing has the potential to increase both the testing rate and the accuracy of ALK fusion identification.

Zebrafish pigment cells develop directly from persistent highly multipotent progenitors

Neural crest cells are highly multipotent stem cells, but it remains unclear how their fate restriction to specific fates occurs. The direct fate restriction model hypothesises that migrating cells maintain full multipotency, whilst progressive fate restriction envisages fully multipotent cells transitioning to partially-restricted intermediates before committing to individual fates. Using zebrafish pigment cell development as a model, we show applying NanoString hybridization single cell transcriptional profiling and RNAscope in situ hybridization that neural crest cells retain broad multipotency throughout migration and even in post-migratory cells in vivo, with no evidence for partially-restricted intermediates. We find that leukocyte tyrosine kinase early expression marks a multipotent stage, with signalling driving iridophore differentiation through repression of fate-specific transcription factors for other fates. We reconcile the direct and progressive fate restriction models by proposing that pigment cell development occurs directly, but dynamically, from a highly multipotent state, consistent with our recently-proposed Cyclical Fate Restriction model.

ALK-positive lung cancer: a moving target

Anaplastic lymphoma kinase (ALK) is a potent oncogenic driver in lung cancer. ALK tyrosine kinase inhibitors yield significant benefit in patients with ALK fusion-positive (ALK+) lung cancers; yet the durability of response is limited by drug resistance. Elucidation of on-target resistance mechanisms has facilitated the development of next-generation ALK inhibitors, but overcoming ALK-independent resistance mechanisms remains a challenge. In this Review, we discuss the molecular underpinnings of acquired resistance to ALK-directed therapy and highlight new treatment approaches aimed at inducing long-term remission in ALK+ disease.

Patient-associated mutations in Drosophila Alk perturb neuronal differentiation and promote survival

Activating anaplastic lymphoma kinase (ALK) receptor tyrosine kinase (RTK) mutations occur in pediatric neuroblastoma and are associated with poor prognosis. To study ALK-activating mutations in a genetically controllable system, we employed CRIPSR/Cas9, incorporating orthologs of the human oncogenic mutations ALKF1174L and ALKY1278S in the Drosophila Alk locus. AlkF1251L and AlkY1355S mutant Drosophila exhibited enhanced Alk signaling phenotypes, but unexpectedly depended on the Jelly belly (Jeb) ligand for activation. Both AlkF1251L and AlkY1355S mutant larval brains displayed hyperplasia, represented by increased numbers of Alk-positive neurons. Despite this hyperplasic phenotype, no brain tumors were observed in mutant animals. We showed that hyperplasia in Alk mutants was not caused by significantly increased rates of proliferation, but rather by decreased levels of apoptosis in the larval brain. Using single-cell RNA sequencing, we identified perturbations during temporal fate specification in AlkY1355S mutant mushroom body lineages. These findings shed light on the role of Alk in neurodevelopmental processes and highlight the potential of Alk-activating mutations to perturb specification and promote survival in neuronal lineages. This article has an associated First Person interview with the first author of the paper.

The neuronal tyrosine kinase receptor ligand ALKAL2 mediates persistent pain

The anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase known for its oncogenic potential that is involved in the development of the peripheral and central nervous system. ALK receptor ligands ALKAL1 and ALKAL2 were recently found to promote neuronal differentiation and survival. Here, we show that inflammation or injury enhanced ALKAL2 expression in a subset of TRPV1⁺ sensory neurons. Notably, ALKAL2 was particularly enriched in both mouse and human peptidergic nociceptors, yet weakly expressed in nonpeptidergic, large-diameter myelinated neurons or in the brain. Using a coculture expression system, we found that nociceptors exposed to ALKAL2 exhibited heightened excitability and neurite outgrowth. Intraplantar CFA or intrathecal infusion of recombinant ALKAL2 led to ALK phosphorylation in the lumbar dorsal horn of the spinal cord. Finally, depletion of ALKAL2 in dorsal root ganglia or blocking ALK with clinically available compounds crizotinib or lorlatinib reversed thermal hyperalgesia and mechanical allodynia induced by inflammation or nerve injury, respectively. Overall, our work uncovers the ALKAL2/ALK signaling axis as a central regulator of nociceptor-induced sensitization. We propose that clinically approved ALK inhibitors used for non–small cell lung cancer and neuroblastomas could be repurposed to treat persistent pain conditions.

A hypothalamic pathway for Augmentor α-controlled body weight regulation

Augmentor α and β (Augα and Augβ) are newly discovered ligands of the receptor tyrosine kinases Alk and Ltk. Augα functions as a dimeric ligand that binds with high affinity and specificity to Alk and Ltk. However, a monomeric Augα fragment and monomeric Augβ also bind to Alk and potently stimulate cellular responses. While previous studies demonstrated that oncogenic Alk mutants function as important drivers of a variety of human cancers, the physiological roles of Augα and Augβ are poorly understood. Here, we investigate the physiological roles of Augα and Augβ by exploring mice deficient in each or both Aug ligands. Analysis of mutant mice showed that both Augα single knockout and double knockout of Augα and Augβ exhibit a similar thinness phenotype and resistance to diet-induced obesity. In the Augα-knockout mice, the leanness phenotype is coupled to increased physical activity. By contrast, Augβ-knockout mice showed similar weight curves as the littermate controls. Experiments are presented demonstrating that Augα is robustly expressed and metabolically regulated in agouti-related peptide (AgRP) neurons, cells that control whole-body energy homeostasis in part via their projections to the paraventricular nucleus (PVN). Moreover, both Alk and melanocortin receptor-4 are expressed in discrete neuronal populations in the PVN and are regulated by projections containing Augα and AgRP, respectively, demonstrating that two distinct mechanisms that regulate pigmentation operate in the hypothalamus to control body weight. These experiments show that Alk-driven cancers were co-opted from a neuronal pathway in control of body weight, offering therapeutic opportunities for metabolic diseases and cancer.

Neuroblastoma Heterogeneity, Plasticity, and Emerging Therapies

Purpose of Review

The evolving information of the initiation, tumor cell heterogeneity, and plasticity of childhood neuroblastoma has opened up new perspectives for developing therapies based on detailed knowledge of the disease.

Recent Findings

The cellular origin of neuroblastoma has begun to unravel and there have been several reports on tumor cell heterogeneity based on transcriptional core regulatory circuitries that have given us important information on the biology of neuroblastoma as a developmental disease. This together with new insight of the tumor microenvironment which acts as a support for neuroblastoma growth has given us the prospect for designing better treatment approaches for patients with high-risk neuroblastoma. Here, we discuss these new discoveries and highlight some emerging therapeutic options.

Summary

Neuroblastoma is a disease with multiple facets. Detailed biological and molecular knowledge on neuroblastoma initiation, heterogeneity, and the communications between cells in the tumor microenvironment holds promise for better therapies.

Genomic consequences of domestication of the Siamese fighting fish

Siamese fighting (betta) fish are among the most popular and morphologically diverse pet fish, but the genetic bases of their domestication and phenotypic diversification are largely unknown. We assembled de novo the genome of a wild Betta splendens and whole-genome sequenced 98 individuals across five closely related species. We find evidence of bidirectional hybridization between domesticated ornamental betta and other wild Betta species. We discover dmrt1 as the main sex determination gene in ornamental betta and that it has lower penetrance in wild B. splendens. Furthermore, we find genes with signatures of recent, strong selection that have large effects on color in specific parts of the body or on the shape of individual fins and that most are unlinked. Our results demonstrate how simple genetic architectures paired with anatomical modularity can lead to vast phenotypic diversity generated during animal domestication and launch betta as a powerful new system for evolutionary genetics.

Sustained Response to Entrectinib in an Infant With a Germline ALKAL2 Variant and Refractory Metastatic Neuroblastoma With Chromosomal 2p Gain and Anaplastic Lymphoma Kinase and Tropomyosin Receptor Kinase Activation

Personalized molecular workup enabled successful ALK inhibitor treatment in a child with resistant neuroblastoma.

Cell Fate Decisions in the Neural Crest, from Pigment Cell to Neural Development

The neural crest shows an astonishing multipotency, generating multiple neural derivatives, but also pigment cells, skeletogenic and other cell types. The question of how this process is controlled has been the subject of an ongoing debate for more than 35 years. Based upon new observations of zebrafish pigment cell development, we have recently proposed a novel, dynamic model that we believe goes some way to resolving the controversy. Here, we will firstly summarize the traditional models and the conflicts between them, before outlining our novel model. We will also examine our recent dynamic modelling studies, looking at how these reveal behaviors compatible with the biology proposed. We will then outline some of the implications of our model, looking at how it might modify our views of the processes of fate specification, differentiation, and commitment.

Mechanism for the activation of the anaplastic lymphoma kinase receptor

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase (RTK) that regulates important functions in the central nervous system^1,2. The ALK gene is a hotspot for chromosomal translocation events that result in several fusion proteins that cause a variety of human malignancies³. Somatic and germline gain-of-function mutations in ALK were identified in paediatric neuroblastoma^4-7. ALK is composed of an extracellular region (ECR), a single transmembrane helix and an intracellular tyrosine kinase domain^8,9. ALK is activated by the binding of ALKAL1 and ALKAL2 ligands^10-14 to its ECR, but the lack of structural information for the ALK-ECR or for ALKAL ligands has limited our understanding of ALK activation. Here we used cryo-electron microscopy, nuclear magnetic resonance and X-ray crystallography to determine the atomic details of human ALK dimerization and activation by ALKAL1 and ALKAL2. Our data reveal a mechanism of RTK activation that allows dimerization by either dimeric (ALKAL2) or monomeric (ALKAL1) ligands. This mechanism is underpinned by an unusual architecture of the receptor-ligand complex. The ALK-ECR undergoes a pronounced ligand-induced rearrangement and adopts an orientation parallel to the membrane surface. This orientation is further stabilized by an interaction between the ligand and the membrane. Our findings highlight the diversity in RTK oligomerization and activation mechanisms.

Structural basis of cytokine-mediated activation of ALK family receptors

Anaplastic lymphoma kinase (ALK)¹ and the related leukocyte tyrosine kinase (LTK)² are recently deorphanized receptor tyrosine kinases³. Together with their activating cytokines, ALKAL1 and ALKAL2^4-6 (also called FAM150A and FAM150B or AUGβ and AUGα, respectively), they are involved in neural development⁷, cancer^7-9 and autoimmune diseases¹⁰. Furthermore, mammalian ALK recently emerged as a key regulator of energy expenditure and weight gain¹¹, consistent with a metabolic role for Drosophila ALK¹². Despite such functional pleiotropy and growing therapeutic relevance^13,14, structural insights into ALK and LTK and their complexes with cognate cytokines have remained scarce. Here we show that the cytokine-binding segments of human ALK and LTK comprise a novel architectural chimera of a permuted TNF-like module that braces a glycine-rich subdomain featuring a hexagonal lattice of long polyglycine type II helices. The cognate cytokines ALKAL1 and ALKAL2 are monomeric three-helix bundles, yet their binding to ALK and LTK elicits similar dimeric assemblies with two-fold symmetry, that tent a single cytokine molecule proximal to the cell membrane. We show that the membrane-proximal EGF-like domain dictates the apparent cytokine preference of ALK. Assisted by these diverse structure-function findings, we propose a structural and mechanistic blueprint for complexes of ALK family receptors, and thereby extend the repertoire of ligand-mediated dimerization mechanisms adopted by receptor tyrosine kinases.

Chromosome Imbalances in Neuroblastoma-Recent Molecular Insight into Chromosome 1p-deletion, 2p-gain, and 11q-deletion Identifies New Friends and Foes for the Future

Simple Summary

Neuroblastoma is a pediatric cancer that arises in the sympathetic nervous system. High-risk neuroblastoma is clinically challenging and identification of novel therapies, particularly those that offer a reduction in morbidity for these patients, is a high priority. Combining genetic analyses with investigation of molecular mechanisms, while considering recent advances in our understanding of key developmental events, provides avenues for future treatment. Here we review and highlight several recently published articles that address novel molecular mechanisms arising from chromosome 1p, 2p, and 11q aberrations, which likely contribute to high-risk neuroblastoma, and discusses their potential impact on treatment options.

Abstract

Neuroblastoma is the most common extracranial solid pediatric tumor, with around 15% childhood cancer-related mortality. High-risk neuroblastomas exhibit a range of genetic, morphological, and clinical heterogeneities, which add complexity to diagnosis and treatment with existing modalities. Identification of novel therapies is a high priority in high-risk neuroblastoma, and the combination of genetic analysis with increased mechanistic understanding—including identification of key signaling and developmental events—provides optimism for the future. This focused review highlights several recent findings concerning chromosomes 1p, 2p, and 11q, which link genetic aberrations with aberrant molecular signaling output. These novel molecular insights contribute important knowledge towards more effective treatment strategies for neuroblastoma.

In vivo Profiling of the Alk Proximitome in the Developing Drosophila Brain

Anaplastic lymphoma kinase (Alk) is an evolutionary conserved receptor tyrosine kinase belonging to the insulin receptor superfamily. In addition to its well-studied role in cancer, numerous studies have revealed that Alk signaling is associated with a variety of complex traits such as: regulation of growth and metabolism, hibernation, regulation of neurotransmitters, synaptic coupling, axon targeting, decision making, memory formation and learning, alcohol use disorder, as well as steroid hormone metabolism. In this study, we used BioID-based in vivo proximity labeling to identify molecules that interact with Alk in the Drosophila central nervous system (CNS). To do this, we used CRISPR/Cas9 induced homology-directed repair (HDR) to modify the endogenous Alk locus to produce first and next generation Alk::BioID chimeras. This approach allowed identification of Alk proximitomes under physiological conditions and without overexpression. Our results show that the next generation of BioID proteins (TurboID and miniTurbo) outperform the first generation BirA* fusion in terms of labeling speed and efficiency. LC-MS3-based BioID screening of Alk^TurboID and Alk^miniTurbo larval brains revealed an extensive neuronal Alk proximitome identifying numerous potential components of Alk signaling complexes. Validation of Alk proximitome candidates further revealed co-expression of Stardust (Sdt), Discs large 1 (Dlg1), Syntaxin (Syx) and Rugose (Rg) with Alk in the CNS and identified the protein-tyrosine-phosphatase Corkscrew (Csw) as a modulator of Alk signaling.

Cyclical fate restriction: a new view of neural crest cell fate specification

Neural crest cells are crucial in development, not least because of their remarkable multipotency. Early findings stimulated two hypotheses for how fate specification and commitment from fully multipotent neural crest cells might occur, progressive fate restriction (PFR) and direct fate restriction, differing in whether partially restricted intermediates were involved. Initially hotly debated, they remain unreconciled, although PFR has become favoured. However, testing of a PFR hypothesis of zebrafish pigment cell development refutes this view. We propose a novel 'cyclical fate restriction' hypothesis, based upon a more dynamic view of transcriptional states, reconciling the experimental evidence underpinning the traditional hypotheses.

Defining Pathological Activities of ALK in Neuroblastoma, a Neural Crest-Derived Cancer

Neuroblastoma is a common extracranial solid tumour of childhood, responsible for 15% of cancer-related deaths in children. Prognoses vary from spontaneous remission to aggressive disease with extensive metastases, where treatment is challenging. Tumours are thought to arise from sympathoadrenal progenitor cells, which derive from an embryonic cell population called neural crest cells that give rise to diverse cell types, such as facial bone and cartilage, pigmented cells, and neurons. Tumours are found associated with mature derivatives of neural crest, such as the adrenal medulla or paraspinal ganglia. Sympathoadrenal progenitor cells express anaplastic lymphoma kinase (ALK), which encodes a tyrosine kinase receptor that is the most frequently mutated gene in neuroblastoma. Activating mutations in the kinase domain are common in both sporadic and familial cases. The oncogenic role of ALK has been extensively studied, but little is known about its physiological role. Recent studies have implicated ALK in neural crest migration and sympathetic neurogenesis. However, very few downstream targets of ALK have been identified. Here, we describe pathological activation of ALK in the neural crest, which promotes proliferation and migration, while preventing differentiation, thus inducing the onset of neuroblastoma. Understanding the effects of ALK activity on neural crest cells will help find new targets for neuroblastoma treatment.

BioID-Screening Identifies PEAK1 and SHP2 as Components of the ALK Proximitome in Neuroblastoma Cells

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase (RTK) that is mutated in approximately 10% of pediatric neuroblastoma (NB). To shed light on ALK-driven signaling processes, we employed BioID-based in vivo proximity labeling to identify molecules that interact intracellularly with ALK. NB-derived SK-N-AS and SK-N-BE(2) cells expressing inducible ALK-BirA* fusion proteins were generated and stimulated with ALKAL ligands in the presence and absence of the ALK tyrosine kinase inhibitor (TKI) lorlatinib. LC/MS-MS analysis identified multiple proteins, including PEAK1 and SHP2, which were validated as ALK interactors in NB cells. Further analysis of the ALK-SHP2 interaction confirmed that the ALK-SHP2 interaction as well as SHP2-Y542 phosphorylation was dependent on ALK activation. Use of the SHP2 inhibitors, SHP099 and RMC-4550, resulted in inhibition of cell growth in ALK-driven NB cells. In addition, we noted a strong synergistic effect of combined ALK and SHP2 inhibition that was specific to ALK-driven NB cells, suggesting a potential therapeutic option for ALK-driven NB.

A complex genetic architecture in zebrafish relatives Danio quagga and D. kyathit underlies development of stripes and spots

Vertebrate pigmentation is a fundamentally important, multifaceted phenotype. Zebrafish, Danio rerio, has been a valuable model for understanding genetics and development of pigment pattern formation due to its genetic and experimental tractability, advantages that are shared across several Danio species having a striking array of pigment patterns. Here, we use the sister species D. quagga and D. kyathit, with stripes and spots, respectively, to understand how natural genetic variation impacts phenotypes at cellular and organismal levels. We first show that D. quagga and D. kyathit phenotypes resemble those of wild-type D. rerio and several single locus mutants of D. rerio, respectively, in a morphospace defined by pattern variation along dorsoventral and anteroposterior axes. We then identify differences in patterning at the cellular level between D. quagga and D. kyathit by repeated daily imaging during pattern development and quantitative comparisons of adult phenotypes, revealing that patterns are similar initially but diverge ontogenetically. To assess the genetic architecture of these differences, we employ reduced-representation sequencing of second-generation hybrids. Despite the similarity of D. quagga to D. rerio, and D. kyathit to some D. rerio mutants, our analyses reveal a complex genetic basis for differences between D. quagga and D. kyathit, with several quantitative trait loci contributing to variation in overall pattern and cellular phenotypes, epistatic interactions between loci, and abundant segregating variation within species. Our findings provide a window into the evolutionary genetics of pattern-forming mechanisms in Danio and highlight the complexity of differences that can arise even between sister species. Further studies of natural genetic diversity underlying pattern variation in D. quagga and D. kyathit should provide insights complementary to those from zebrafish mutant phenotypes and more distant species comparisons.

Pigment patterns of fishes are diverse and function in a wide range of behaviors. Common pattern themes include stripes and spots, exemplified by the closely related minnows Danio quagga and D. kyathit, respectively. We show that these patterns arise late in development owing to alterations in the development and arrangements of pigment cells. In the closely related model organism zebrafish (D. rerio) single genes can switch the pattern from stripes to spots. Yet, we show that pattern differences between D. quagga and D. kyathit have a more complex genetic basis, depending on multiple genes and interactions between these genes. Our findings illustrate the importance of characterizing naturally occurring genetic variants, in addition to laboratory induced mutations, for a more complete understanding of pigment pattern development and evolution.

Loss of RET Promotes Mesenchymal Identity in Neuroblastoma Cells

Aberrant activation of anaplastic lymphoma kinase (ALK) drives neuroblastoma (NB). Previous work identified the RET receptor tyrosine kinase (RTK) as a downstream target of ALK activity in NB models. We show here that ALK activation in response to ALKAL2 ligand results in the rapid phosphorylation of RET in NB cells, providing additional insight into the contribution of RET to the ALK-driven gene signature in NB. To further address the role of RET in NB, RET knockout (KO) SK-N-AS cells were generated by CRISPR/Cas9 genome engineering. Gene expression analysis of RET KO NB cells identified a reprogramming of NB cells to a mesenchymal (MES) phenotype that was characterized by increased migration and upregulation of the AXL and MNNG HOS transforming gene (MET) RTKs, as well as integrins and extracellular matrix components. Strikingly, the upregulation of AXL in the absence of RET reflects the development timeline observed in the neural crest as progenitor cells undergo differentiation during embryonic development. Together, these findings suggest that a MES phenotype is promoted in mesenchymal NB cells in the absence of RET, reflective of a less differentiated developmental status.

Gilteritinib overcomes lorlatinib resistance in ALK-rearranged cancer

ALK gene rearrangement was observed in 3%-5% of non-small cell lung cancer patients, and multiple ALK-tyrosine kinase inhibitors (TKIs) have been sequentially used. Multiple ALK-TKI resistance mutations have been identified from the patients, and several compound mutations, such as I1171N + F1174I or I1171N + L1198H are resistant to all the approved ALK-TKIs. In this study, we found that gilteritinib has an inhibitory effect on ALK-TKI-resistant single mutants and I1171N compound mutants in vitro and in vivo. Surprisingly, EML4-ALK I1171N + F1174I compound mutant-expressing tumors were not completely shrunk but regrew within a short period of time after alectinib or lorlatinib treatment. However, the relapsed tumor was markedly shrunk after switching to the gilteritinib in vivo model. In addition, gilteritinib was effective against NTRK-rearranged cancers including entrectinib-resistant NTRK1 G667C-mutant and ROS1 fusion-positive cancer.

ALK ligand ALKAL2 potentiates MYCN-driven neuroblastoma in the absence of ALK mutation

High-risk neuroblastoma (NB) is responsible for a disproportionate number of childhood deaths due to cancer. One indicator of high-risk NB is amplification of the neural MYC (MYCN) oncogene, which is currently therapeutically intractable. Identification of anaplastic lymphoma kinase (ALK) as an NB oncogene raised the possibility of using ALK tyrosine kinase inhibitors (TKIs) in treatment of patients with activating ALK mutations. 8-10% of primary NB patients are ALK-positive, a figure that increases in the relapsed population. ALK is activated by the ALKAL2 ligand located on chromosome 2p, along with ALK and MYCN, in the "2p-gain" region associated with NB. Dysregulation of ALK ligand in NB has not been addressed, although one of the first oncogenes described was v-sis that shares > 90% homology with PDGF. Therefore, we tested whether ALKAL2 ligand could potentiate NB progression in the absence of ALK mutation. We show that ALKAL2 overexpression in mice drives ALK TKI-sensitive NB in the absence of ALK mutation, suggesting that additional NB patients, such as those exhibiting 2p-gain, may benefit from ALK TKI-based therapeutic intervention.

NPM-ALK: A Driver of Lymphoma Pathogenesis and a Therapeutic Target

Simple Summary

Anaplastic lymphoma kinase (ALK) is a tyrosine kinase associated with Anaplastic Large Cell lymphoma (ALCL) through oncogenic translocations mainly NPM-ALK. Chemotherapy is effective in ALK(+) ALCL patients and induces remission rates of approximately 80%. The remaining patients do not respond to chemotherapy and some patients have drug-resistant relapses. Different classes of ALK tyrosine kinase inhibitors (TKI) are available but used exclusively for EML4-ALK (+) lung cancers. The significant toxicities of most ALK inhibitors explain the delay in their use in pediatric ALCL patients. Some ALCL patients do not respond to the first generation TKI or develop an acquired resistance. Combination therapy with ALK inhibitors in ALCL is the current challenge.

Abstract

Initially discovered in anaplastic large cell lymphoma (ALCL), the ALK anaplastic lymphoma kinase is a tyrosine kinase which is affected in lymphomas by oncogenic translocations, mainly NPM-ALK. To date, chemotherapy remains a viable option in ALCL patients with ALK translocations as it leads to remission rates of approximately 80%. However, the remaining patients do not respond to chemotherapy and some patients have drug-resistant relapses. It is therefore crucial to identify new and better treatment options. Nowadays, different classes of ALK tyrosine kinase inhibitors (TKI) are available and used exclusively for EML4-ALK (+) lung cancers. In fact, the significant toxicities of most ALK inhibitors explain the delay in their use in ALCL patients, who are predominantly children. Moreover, some ALCL patients do not respond to Crizotinib, the first generation TKI, or develop an acquired resistance months following an initial response. Combination therapy with ALK inhibitors in ALCL is the current challenge.

ALKAL1 gene silencing prevents colorectal cancer progression via suppressing Sonic Hedgehog (SHH) signaling pathway

Anaplastic lymphoma kinase (ALK) has been described in a range of human cancers and is involved in cancer initiation and progression via activating multiple signaling pathways, such as the PI3K-AKT, CRKL-C3G, MEKK2/3-MEK5-ERK5, JAK-STAT and MAPK signal pathways. Recently ALK and LTK ligand 1 (ALKAL1) also named “augmentor-β” or “FAM150A” is identified as a potent activating ligands for human ALK that bind to the extracellular domain of ALK. However, due to its poor stability, the mechanisms of ALKAL1 underlying the tumor progression in the human cancers including colorectal cancer have not been well documented. Herein, ALKAL1 expression was evaluated by RNA sequencing datasets from The Cancer Genome Atlas (TCGA) of 625 cases colorectal cancer, immunohistochemical analysis of 377 cases colorectal cancer tissues, and Western blotting even Real-time PCR of 10 pairs of colorectal cancer tissues and adjacent normal tissues, as well as 8 colorectal cancer cell lines. Statistical analysis was performed to explore the correlation between ALKAL1 expression and clinicopathological features in colorectal cancer. Univariate and multivariate Cox regression analysis were performed to examine the association between ALKAL1 expression and overall survival. In vitro and in vivo assays were performed to assess the biological roles of ALKAL1 in colorectal cancer. Gene set enrichment analysis (GSEA), Western blotting and luciferase assays were used to identify the underlying signal pathway involved in the tumor progression role of ALKAL1. As a result, we showed that ALKAL1 was upregulated in colorectal cancer tissues and cell lines. Upregulation of ALKAL1 correlated with tumor malignancy and poor prognosis in colorectal cancer. ALKAL1 silencing inhibited tumorigenesis, metastasis and invasion of colorectal cancer cells, and inhibited SHH signaling pathway, which is essential for ALKAL1 induced migration. Our findings reveal a new mechanism by which ALKAL1 participates in colorectal cancer migration and invasion via activating the SHH signaling pathway.

Comparative Genomics within and across Bilaterians Illuminates the Evolutionary History of ALK and LTK Proto-Oncogene Origination and Diversification

Comparative genomic analyses have enormous potential for identifying key genes central to human health phenotypes, including those that promote cancers. In particular, the successful development of novel therapeutics using model species requires phylogenetic analyses to determine molecular homology. Accordingly, we investigate the evolutionary histories of anaplastic lymphoma kinase (ALK)—which can underlie tumorigenesis in neuroblastoma, nonsmall cell lung cancer, and anaplastic large-cell lymphoma—its close relative leukocyte tyrosine kinase (LTK) and their candidate ligands. Homology of ligands identified in model organisms to those functioning in humans remains unclear. Therefore, we searched for homologs of the human genes across metazoan genomes, finding that the candidate ligands Jeb and Hen-1 were restricted to nonvertebrate species. In contrast, the ligand augmentor (AUG) was only identified in vertebrates. We found two ALK-like and four AUG-like protein-coding genes in lamprey. Of these six genes, only one ALK-like and two AUG-like genes exhibited early embryonic expression that parallels model mammal systems. Two copies of AUG are present in nearly all jawed vertebrates. Our phylogenetic analysis strongly supports the presence of previously unrecognized functional convergences of ALK and LTK between actinopterygians and sarcopterygians—despite contemporaneous, highly conserved synteny of ALK and LTK. These findings provide critical guidance regarding the propriety of fish and mammal models with regard to model organism-based investigation of these medically important genes. In sum, our results provide the phylogenetic context necessary for effective investigations of the functional roles and biology of these critically important receptors.

Identification of the Wallenda JNKKK as an Alk suppressor reveals increased competitiveness of Alk-expressing cells

Anaplastic lymphoma kinase (Alk) is a receptor tyrosine kinase of the insulin receptor super-family that functions as oncogenic driver in a range of human cancers such as neuroblastoma. In order to investigate mechanisms underlying Alk oncogenic signaling, we conducted a genetic suppressor screen in Drosophila melanogaster. Our screen identified multiple loci important for Alk signaling, including members of Ras/Raf/ERK-, Pi3K-, and STAT-pathways as well as tailless (tll) and foxo whose orthologues NR2E1/TLX and FOXO3 are transcription factors implicated in human neuroblastoma. Many of the identified suppressors were also able to modulate signaling output from activated oncogenic variants of human ALK, suggesting that our screen identified targets likely relevant in a wide range of contexts. Interestingly, two misexpression alleles of wallenda (wnd, encoding a leucine zipper bearing kinase similar to human DLK and LZK) were among the strongest suppressors. We show that Alk expression leads to a growth advantage and induces cell death in surrounding cells. Our results suggest that Alk activity conveys a competitive advantage to cells, which can be reversed by over-expression of the JNK kinase kinase Wnd.

Linking genotype, cell behavior, and phenotype: multidisciplinary perspectives with a basis in zebrafish patterns

Zebrafish are characterized by dark and light stripes, but mutants display a rich variety of altered patterns. These patterns arise from the interactions of brightly colored pigment cells, making zebrafish a self-organization problem. The diversity of patterns present in zebrafish and other emerging fish models provides an excellent system for elucidating how genes, cell behavior, and visible animal characteristics are related. With the goal of highlighting how experimental and mathematical approaches can be used to link these scales, I overview current descriptions of zebrafish patterning, describe advances in the understanding of the mechanisms underlying cell communication, and discuss new work that moves beyond zebrafish to explore patterning in evolutionary relatives.

The neuronal receptor tyrosine kinase Alk is a target for longevity

Inhibition of signalling through several receptor tyrosine kinases (RTKs), including the insulin-like growth factor receptor and its orthologues, extends healthy lifespan in organisms from diverse evolutionary taxa. This raises the possibility that other RTKs, including those already well studied for their roles in cancer and developmental biology, could be promising targets for extending healthy lifespan. Here, we focus on anaplastic lymphoma kinase (Alk), an RTK with established roles in nervous system development and in multiple cancers, but whose effects on aging remain unclear. We find that several means of reducing Alk signalling, including mutation of its ligand jelly belly (jeb), RNAi knock-down of Alk, or expression of dominant-negative Alk in adult neurons, can extend healthy lifespan in female, but not male, Drosophila. Moreover, reduced Alk signalling preserves neuromuscular function with age, promotes resistance to starvation and xenobiotic stress, and improves night sleep consolidation. We find further that inhibition of Alk signalling in adult neurons modulates the expression of several insulin-like peptides, providing a potential mechanistic link between neuronal Alk signalling and organism-wide insulin-like signalling. Finally, we show that TAE-684, a small molecule inhibitor of Alk, can extend healthy lifespan in Drosophila, suggesting that the repurposing of Alk inhibitors may be a promising direction for strategies to promote healthy aging.

Tyrosine kinase signaling in and on the endoplasmic reticulum

Tyrosine kinases are signaling molecules that are common to all metazoans and are involved in the regulation of many cellular processes such as proliferation and survival. While most attention has been devoted to tyrosine kinases signaling at the plasma membrane and the cytosol, very little attention has been dedicated to signaling at endomembranes. In this review, I will discuss recent evidence that we obtained on signaling of tyrosine kinases at the surface of the endoplasmic reticulum (ER), as well as in the lumen of this organelle. I will discuss how tyrosine kinase signaling might regulate ER proteostasis and the implication thereof to general cell physiology.

Galanin Signaling in the Brain Regulates Color Pattern Formation in Zebrafish

Color patterns are prominent features of many animals and are of high evolutionary relevance. In basal vertebrates, color patterns are composed of specialized pigment cells that arrange in multilayered mosaics in the skin. Zebrafish (Danio rerio), the preeminent model system for vertebrate color pattern formation, allows genetic screens as powerful approaches to identify novel functions in a complex biological system. Adult zebrafish display a series of blue and golden horizontal stripes, composed of black melanophores, silvery or blue iridophores, and yellow xanthophores. This stereotyped pattern is generated by self-organization involving direct cell contacts between all three types of pigment cells mediated by integral membrane proteins [1, 2, 3, 4, 5]. Here, we show that neuropeptide signaling impairs the striped pattern in a global manner. Mutations in the genes coding either for galanin receptor 1A (npm/galr1A) or for its ligand galanin (galn) result in fewer stripes, a pale appearance, and the mixing of cell types, thus resembling mutants with thyroid hypertrophy [6]. Zebrafish chimeras obtained by transplantations of npm/galr1A mutant blastula cells indicate that mutant pigment cells of all three types can contribute to a normal striped pattern in the appropriate host. However, loss of galr1A expression in a specific region of the brain is sufficient to cause the mutant phenotype in an otherwise wild-type fish. Increased thyroid hormone levels in mutant fish suggest that galanin signaling through Galr1A in the pituitary is an upstream regulator of the thyroid hormone pathway, which in turn promotes precise interactions of pigment cells during color pattern formation.

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Zebrafish stripes are generated by three types of self-organizing pigment cells

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Galanin signaling through Galr1A impairs zebrafish stripe formation globally

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Galr1A function in a specific brain region is required for pigment cell interactions

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Galanin signaling functions to downregulate thyroid hormone levels

Nongenetic engineering strategies for regulating receptor oligomerization in living cells

Nongenetic strategies for regulating receptor oligomerization in living cells based on DNA, protein, small molecules and physical stimuli.

Analysis of ALK, MYCN, and the ALK ligand ALKAL2 (FAM150B/AUGα) in neuroblastoma patient samples with chromosome arm 2p rearrangements

Gain of chromosome arm 2p is a previously described entity in neuroblastoma (NB). This genomic address is home to two important oncogenes in NB-MYCN and anaplastic lymphoma kinase (ALK). MYCN amplification is a critical prognostic factor coupled with poor prognosis in NB. Mutation of the ALK receptor tyrosine kinase has been described in both somatic and familial NB. Here, ALK activation occurs in the context of the full-length receptor, exemplified by activating point mutations in NB. ALK overexpression and activation, in the absence of genetic mutation has also been described in NB. In addition, the recently identified ALK ligand ALKAL2 (previously described as FAM150B and AUGα) is also found on the distal portion of 2p, at 2p25. Here we analyze 356 NB tumor samples and discuss observations indicating that gain of 2p has implications for the development of NB. Finally, we put forward the hypothesis that the effect of 2p gain may result from a combination of MYCN, ALK, and the ALK ligand ALKAL2.

Repotrectinib (TPX-0005), effectively reduces growth of ALK driven neuroblastoma cells

Neuroblastoma is the most commonly diagnosed extracranial tumor in the first year of life. Approximately 9% of neuroblastoma patients present germline or somatic aberrations in the gene encoding for anaplastic lymphoma kinase (ALK). This increases in high-risk neuroblastomas, which have a 14% frequency of ALK aberrations at the time of diagnosis and show increasing numbers at relapse. Abrogating ALK activity with kinase inhibitors is employed as clinical therapy in malignancies such as non-small cell lung cancer and has shown good results in pediatric inflammatory myofibroblastic tumors and anaplastic large cell lymphomas. A phase I clinical trial of the first generation ALK inhibitor, crizotinib, in neuroblastoma patients showed modest results and suggested that further investigation was needed. Continuous development of ALK inhibitors has resulted in the third generation inhibitor repotrectinib (TPX-0005), which targets the active kinase conformations of ALK, ROS1 and TRK receptors. In the present study we investigated the effects of repotrectinib in a neuroblastoma setting in vitro and in vivo. Neuroblastoma cell lines were treated with repotrectinib to investigate inhibition of ALK and to determine its effect on proliferation. PC12 cells transfected with different ALK mutant variants were used to study the efficacy of repotrectinib to block ALK activation/signaling. The in vivo effect of repotrectinib was also analyzed in a neuroblastoma xenograft model. Our results show that repotrectinib is capable of inhibiting signaling activity of a range of ALK mutant variants found in neuroblastoma patients and importantly it exhibits strong antitumor effects in a xenograft model of neuroblastoma.

Zebrafish Pigment Pattern Formation: Insights into the Development and Evolution of Adult Form

Vertebrate pigment patterns are diverse and fascinating adult traits that allow animals to recognize conspecifics, attract mates, and avoid predators. Pigment patterns in fish are among the most amenable traits for studying the cellular basis of adult form, as the cells that produce diverse patterns are readily visible in the skin during development. The genetic basis of pigment pattern development has been most studied in the zebrafish, Danio rerio. Zebrafish adults have alternating dark and light horizontal stripes, resulting from the precise arrangement of three main classes of pigment cells: black melanophores, yellow xanthophores, and iridescent iridophores. The coordination of adult pigment cell lineage specification and differentiation with specific cellular interactions and morphogenetic behaviors is necessary for stripe development. Besides providing a nice example of pattern formation responsible for an adult trait of zebrafish, stripe-forming mechanisms also provide a conceptual framework for posing testable hypotheses about pattern diversification more broadly. Here, we summarize what is known about lineages and molecular interactions required for pattern formation in zebrafish, we review some of what is known about pattern diversification in Danio, and we speculate on how patterns in more distant teleosts may have evolved to produce a stunningly diverse array of patterns in nature.

The identification of genes involved in the evolution of color patterns in fish

The genetic basis of morphological variation, both within and between species, provides a major topic in evolutionary biology. Teleost fish produce most elaborate color patterns, and among the more than 20000 species a number have been chosen for more detailed analyses because they are suitable to study particular aspects of color pattern evolution. In several fish species, color variants and pattern variants have been collected, transcriptome analyses have been carried out, and the recent advent of gene editing tools, such as CRISPR/Cas9, has allowed the production of mutants. Covering mostly the literature from the last three years, we discuss the cellular basis of coloration and the identification of loci involved in color pattern differences between sister species in cichlids and Danio species, in which cis-regulatory changes seem to prevail.

Dual inhibition of IGF-IR and ALK as an effective strategy to eradicate NPM-ALK+ T-cell lymphoma

Background

Nucleophosmin-anaplastic lymphoma kinase-expressing (NPM-ALK⁺) T cell lymphoma is an aggressive neoplasm. NPM-ALK, an oncogenic tyrosine kinase, plays a critical role in this lymphoma. Recently, selective ALK inhibitors have emerged as a first-line therapy for this neoplasm. Unfortunately, ALK inhibitors were hindered by emergence of resistance and relapse. We have previously demonstrated that type I insulin-like growth factor receptor (IGF-IR) is commonly expressed and activated in this lymphoma. In addition, IGF-IR and NPM-ALK are physically associated and reciprocally enhance their phosphorylation/activation. Herein, we tested the hypothesis that combined inhibition of IGF-IR and NPM-ALK could significantly improve the effects of inhibiting each kinase alone.

Methods

We used clinically utilized inhibitors of IGF-IR (picropodophyllin; PPP) and ALK (ASP3026) to assess the in vitro cellular effects of combined treatment versus treatment using a single agent. Moreover, we used a systemic NPM-ALK⁺ T cell lymphoma mouse model to analyze the in vivo effects of PPP and ASP3026 alone or in combination.

Results

Our data show that combined treatment with PPP and ASP3026 decreased the viability, proliferation, and anchorage-independent colony formation, and increased apoptosis of NPM-ALK⁺ T cell lymphoma cells in vitro. The in vitro effects of combined treatment were synergistic and significantly more pronounced than the effects of PPP or ASP3026 alone. Biochemically, simultaneous antagonism of IGF-IR and ALK induced more pronounced decrease in pIGF-IR^Y1135/1136, pNPM-ALK^Y646, and pSTAT3^Y705 levels than antagonizing IGF-IR or ALK alone. Moreover, combined targeting of IGF-IR and NPM-ALK decreased significantly systemic lymphoma tumor growth and improved mice survival in vivo. Consistent with the in vitro results, the in vivo effects of the combined therapy were more pronounced than the effects of targeting IGF-IR or ALK alone.

Conclusions

Combined targeting of IGF-IR and ALK is more effective than targeting IGF-IR or ALK alone in NPM-ALK⁺ T cell lymphoma. This strategy might also limit emergence of resistance to high doses of ALK inhibitors. Therefore, it could represent a successful therapeutic approach to eradicate this aggressive lymphoma. Importantly, combined inhibition is feasible because of the clinical availability of IGF-IR and ALK inhibitors. Our findings are applicable to other types of cancer where IGF-IR and ALK are simultaneously expressed.

Electronic supplementary material

The online version of this article (10.1186/s13045-019-0768-8) contains supplementary material, which is available to authorized users.

Alectinib, an Anaplastic Lymphoma Kinase Inhibitor, Abolishes ALK Activity and Growth in ALK-Positive Neuroblastoma Cells

Oncogenic receptor tyrosine kinases including anaplastic lymphoma kinase (ALK) are implicated in numerous solid and hematologic cancers. ALK mutations are reported in an estimated 9% of neuroblastoma and recent reports indicate that the percentage of ALK-positive cases increases in the relapsed patient population. Initial clinical trial results have shown that it is difficult to inhibit growth of ALK positive neuroblastoma with crizotinib, motivating investigation of next generation ALK inhibitors with higher affinity for ALK. Here, alectinib, a potent next generation ALK inhibitor with antitumor activity was investigated in ALK-driven neuroblastoma models. Employing neuroblastoma cell lines and mouse xenografts we show a clear and efficient inhibition of ALK activity by alectinib. Inhibition of ALK activity was observed in vitro employing a set of different constitutively active ALK variants in biochemical assays. The results suggest that alectinib is an effective inhibitor of ALK kinase activity in ALK addicted neuroblastoma and should be considered as a potential future therapeutic option for ALK-positive neuroblastoma patients alone or in combination with other treatments.

LTK is an ER-resident receptor tyrosine kinase that regulates secretion

The endoplasmic reticulum (ER) is a major regulator of cellular proteostasis. However, only little is known about signaling molecules resident to this organelle. Centonze et al. identify LTK as the first ER-resident receptor tyrosine kinase and show that it stimulates secretory trafficking out of the ER.

The endoplasmic reticulum (ER) is a key regulator of cellular proteostasis because it controls folding, sorting, and degradation of secretory proteins. Much has been learned about how environmentally triggered signaling pathways regulate ER function, but only little is known about local signaling at the ER. The identification of ER-resident signaling molecules will help gain a deeper understanding of the regulation of ER function and thus of proteostasis. Here, we show that leukocyte tyrosine kinase (LTK) is an ER-resident receptor tyrosine kinase. Depletion of LTK as well as its pharmacologic inhibition reduces the number of ER exit sites and slows ER-to-Golgi transport. Furthermore, we show that LTK interacts with and phosphorylates Sec12. Expression of a phosphoablating mutant of Sec12 reduces the efficiency of ER export. Thus, LTK-to-Sec12 signaling represents the first example of an ER-resident signaling module with the potential to regulate proteostasis.

Targeting ALK in Cancer: Therapeutic Potential of Proapoptotic Peptides

ALK is a receptor tyrosine kinase, associated with many tumor types as diverse as anaplastic large cell lymphomas, inflammatory myofibroblastic tumors, breast and renal cell carcinomas, non-small cell lung cancer, neuroblastomas, and more. This makes ALK an attractive target for cancer therapy. Since ALK–driven tumors are dependent for their proliferation on the constitutively activated ALK kinase, a number of tyrosine kinase inhibitors have been developed to block tumor growth. While some inhibitors are under investigation in clinical trials, others are now approved for treatment, notably in ALK-positive lung cancer. Their efficacy is remarkable, however limited in time, as the tumors escape and become resistant to the treatment through different mechanisms. Hence, there is a pressing need to target ALK-dependent tumors by other therapeutic strategies, and possibly use them in combination with kinase inhibitors. In this review we will focus on the therapeutic potential of proapoptotic ALK-derived peptides based on the dependence receptor properties of ALK. We will also try to make a non-exhaustive list of several alternative treatments targeting ALK-dependent and independent signaling pathways.

Developmental and comparative transcriptomic identification of iridophore contribution to white barring in clownfish

Actinopterygian fishes harbor at least eight distinct pigment cell types, leading to a fascinating diversity of colors. Among this diversity, the cellular origin of the white color appears to be linked to several pigment cell types such as iridophores or leucophores. We used the clownfish Amphiprion ocellaris, which has a color pattern consisting of white bars over a darker body, to characterize the pigment cells that underlie the white hue. We observe by electron microscopy that cells in white bars are similar to iridophores. In addition, the transcriptomic signature of clownfish white bars exhibits similarities with that of zebrafish iridophores. We further show by pharmacological treatments that these cells are necessary for the white color. Among the top differentially expressed genes in white skin, we identified several genes (fhl2a, fhl2b, saiyan, gpnmb, and apoD1a) and show that three of them are expressed in iridophores. Finally, we show by CRISPR/Cas9 mutagenesis that these genes are critical for iridophore development in zebrafish. Our analyses provide clues to the genomic underpinning of color diversity and allow identification of new iridophore genes in fish.

The minimal gap-junction network among melanophores and xanthophores required for stripe-pattern formation in zebrafish

Connexin39.4 (Cx39.4) and Connexin41.8 (Cx41.8), two gap-junction proteins expressed in both melanophores and xanthophores, are critical for the intercellular communication among pigment cells that is necessary for generating the stripe pigment pattern of zebrafish. We previously characterized the gap-junction properties of Cx39.4 and Cx41.8, but how these proteins contribute to stripe formation remains unclear; this is because distinct types of connexins potentially form heteromeric gap junctions, which precludes accurate elucidation of individual connexin functions in vivo. Here, by arranging Cx39.4 and Cx41.8 expression in pigment cells, we identified the simplest gap-junction network required for stripe generation: Cx39.4 expression in melanophores is required but expression in xanthophores is not necessary for stripe patterning, whereas Cx41.8 expression in xanthophores is sufficient for the patterning, and Cx41.8 expression in melanophores might stabilize the stripes. Moreover, patch-clamp recordings revealed that Cx39.4 gap junctions exhibit spermidine-dependent rectification property. Our results suggest that Cx39.4 facilitates the critical cell-cell interactions between melanophores and xanthophores that mediate a unidirectional activation-signal transfer from xanthophores to melanophores, which is essential for melanophore survival.

Phosphoproteome and gene expression profiling of ALK inhibition in neuroblastoma cell lines reveals conserved oncogenic pathways

Anaplastic lymphoma kinase (ALK) is a tyrosine kinase receptor that is a clinical target of major interest in cancer. Mutations and rearrangements in ALK trigger the activation of the encoded receptor and its downstream signaling pathways. ALK mutations have been identified in both familial and sporadic neuroblastoma cases as well as in 30 to 40% of relapses, which makes ALK a bona fide target in neuroblastoma therapy. Tyrosine kinase inhibitors (TKIs) that target ALK are currently in clinical use for the treatment of patients with ALK-positive non-small cell lung cancer. However, monotherapy with the ALK inhibitor crizotinib has been less encouraging in neuroblastoma patients with ALK alterations, raising the question of whether combinatorial therapy would be more effective. In this study, we established both phosphoproteomic and gene expression profiles of ALK activity in neuroblastoma cells exposed to first- and third-generation ALK TKIs, to identify the underlying molecular mechanisms and identify relevant biomarkers, signaling networks, and new therapeutic targets. This analysis has unveiled various important leads for novel combinatorial treatment strategies for patients with neuroblastoma and an increased understanding of ALK signaling involved in this disease.

A novel ligand-receptor relationship between families of ribonucleases and receptor tyrosine kinases

Pancreatic ribonuclease is known to participate in host defense system against pathogens, such as parasites, bacteria, and virus, which results in innate immune response. Nevertheless, its potential impact to host cells remains unclear. Of interest, several ribonucleases do not act as catalytically competent enzymes, suggesting that ribonucleases may be associated with certain intrinsic functions other than their ribonucleolytic activities. Most recently, human pancreatic ribonuclease 5 (hRNase5; also named angiogenin; hereinafter referred to as hRNase5/ANG), which belongs to the human ribonuclease A superfamily, has been demonstrated to function as a ligand of epidermal growth factor receptor (EGFR), a member of the receptor tyrosine kinase family. As a newly identified EGFR ligand, hRNase5/ANG associates with EGFR and stimulates EGFR and the downstream signaling in a catalytic-independent manner. Notably, hRNase5/ANG, whose level in sera of pancreatic cancer patients, serves as a non-invasive serum biomarker to stratify patients for predicting the sensitivity to EGFR-targeted therapy. Here, we describe the hRNase5/ANG-EGFR pair as an example to highlight a ligand-receptor relationship between families of ribonucleases and receptor tyrosine kinases, which are thought as two unrelated protein families associated with distinct biological functions. The notion of serum biomarker-guided EGFR-targeted therapies will also be discussed. Furthering our understanding of this novel ligand-receptor interaction will shed new light on the search of ligands for their cognate receptors, especially those orphan receptors without known ligands, and deepen our knowledge of the fundamental research in membrane receptor biology and the translational application toward the development of precision medicine.

Anaplastic Lymphoma Kinase (ALK) Receptor Tyrosine Kinase: A Catalytic Receptor with Many Faces

The anaplastic lymphoma kinase (ALK) receptor is a membrane-bound tyrosine kinase. The pathogenesis of several cancers is closely related to aberrant forms of ALK or aberrant ALK expression, including ALK fusion proteins, ALK-activated point mutations, and ALK amplification. Clinical applications of different ALK inhibitors represent significant progress in targeted therapy. Knowledge of different aspects of ALK biology can provide significant information to further the understanding of this receptor tyrosine kinase. In this mini-review, we briefly summarize different features of ALK. We also summarize some recent research advances on ALK fusion proteins in cancers.

Leukocyte receptor tyrosine kinase interacts with secreted midkine to promote survival of migrating neural crest cells

Neural crest cells migrate long distances throughout the embryo and rely on extracellular signals that attract, repel and/or stimulate survival to ensure proper contribution to target derivatives. Here, we show that leukocyte receptor tyrosine kinase (LTK), an ALK-type receptor tyrosine kinase, is expressed by neural crest cells during early migratory stages in chicken embryos. Loss of LTK in the cranial neural crest impairs migration and results in increased levels of apoptosis. Conversely, midkine, previously proposed as a ligand for ALK, is secreted by the non-neural ectoderm during early neural crest migratory stages and internalized by neural crest cells in vivo Similar to loss of LTK, loss of midkine reduces survival of the migratory neural crest. Moreover, we show by proximity ligation and co-immunoprecipitation assays that midkine binds to LTK. Taken together, these results suggest that LTK in neural crest cells interacts with midkine emanating from the non-neural ectoderm to promote cell survival, revealing a new signaling pathway that is essential for neural crest development.

Clinical response of the novel activating ALK-I1171T mutation in neuroblastoma to the ALK inhibitor ceritinib

Tumors with anaplastic lymphoma kinase (ALK) fusion rearrangements, including non-small-cell lung cancer and anaplastic large cell lymphoma, are highly sensitive to ALK tyrosine kinase inhibitors (TKIs), underscoring the notion that such cancers are addicted to ALK activity. Although mutations in ALK are heavily implicated in childhood neuroblastoma, response to the ALK TKI crizotinib has been disappointing. Embryonal tumors in patients with DNA repair defects such as Fanconi anemia (FA) often have a poor prognosis, because of lack of therapeutic options. Here we report a child with underlying FA and ALK mutant high-risk neuroblastoma responding strongly to precision therapy with the ALK TKI ceritinib. Conventional chemotherapy treatment caused severe, life-threatening toxicity. Genomic analysis of the initial biopsy identified germline FANCA mutations as well as a novel ALK-I1171T variant. ALK-I1171T generates a potent gain-of-function mutant, as measured in PC12 cell neurite outgrowth and NIH3T3 transformation. Pharmacological inhibition profiling of ALK-I1171T in response to various ALK TKIs identified an 11-fold improved inhibition of ALK-I1171T with ceritinib when compared with crizotinib. Immunoaffinity-coupled LC-MS/MS phosphoproteomics analysis indicated a decrease in ALK signaling in response to ceritinib. Ceritinib was therefore selected for treatment in this child. Monotherapy with ceritinib was well tolerated and resulted in normalized catecholamine markers and tumor shrinkage. After 7.5 mo treatment, the residual primary tumor shrunk, was surgically removed, and exhibited hallmarks of differentiation together with reduced Ki67 levels. Clinical follow-up after 21 mo treatment revealed complete clinical remission including all metastatic sites. Therefore, ceritinib presents a viable therapeutic option for ALK-positive neuroblastoma.