Anaplastic lymphoma kinase is required for neurogenesis in the developing central nervous system of zebrafish

Tumor-Agnostic Therapy-The Final Step Forward in the Cure for Human Neoplasms?

Cancer accounted for 10 million deaths in 2020, nearly one in every six deaths annually. Despite advancements, the contemporary clinical management of human neoplasms faces a number of challenges. Surgical removal of tumor tissues is often not possible technically, while radiation and chemotherapy pose the risk of damaging healthy cells, tissues, and organs, presenting complex clinical challenges. These require a paradigm shift in developing new therapeutic modalities moving towards a more personalized and targeted approach. The tumor-agnostic philosophy, one of these new modalities, focuses on characteristic molecular signatures of transformed cells independently of their traditional histopathological classification. These include commonly occurring DNA aberrations in cancer cells, shared metabolic features of their homeostasis or immune evasion measures of the tumor tissues. The first dedicated, FDA-approved tumor-agnostic agent's profound progression-free survival of 78% in mismatch repair-deficient colorectal cancer paved the way for the accelerated FDA approvals of novel tumor-agnostic therapeutic compounds. Here, we review the historical background, current status, and future perspectives of this new era of clinical oncology.

Comparing the effects of irradiation with protons or photons on neonatal mouse brain: Apoptosis, oncogenesis and hippocampal alterations

BACKGROUND AND PURPOSE

Medulloblastoma (MB) is a common primary brain cancer in children. Proton therapy in pediatric MB is intensively studied and widely adopted. Compared to photon, proton radiations offer potential for reduced toxicity due to the characteristic Bragg Peak at the end of their path in tissue. The aim of this study was to compare the effects of irradiation with the same dose of protons or photons in Patched1 heterozygous knockout mice, a murine model predisposed to cancer and non-cancer radiogenic pathologies, including MB and lens opacity.

MATERIALS AND METHODS

TOP-IMPLART is a pulsed linear proton accelerator for proton therapy applications. We compared the long-term health effects of 3 Gy of protons or photons in neonatal mice exposed at postnatal day 2, during a peculiarly susceptible developmental phase of the cerebellum, lens, and hippocampus, to genotoxic stress.

RESULTS

Experimental testing of the 5 mm Spread-Out Bragg Peak (SOBP) proton beam, through evaluation of apoptotic response, confirmed that both cerebellum and hippocampus were within the SOBP irradiation field. While no differences in MB induction were observed after irradiation with protons or photons, lens opacity examination confirmed sparing of the lens after proton exposure. Marked differences in expression of neurogenesis-related genes and in neuroinflammation, but not in hippocampal neurogenesis, were observed after irradiation of wild-type mice with both radiation types.

CONCLUSION

In-vivo experiments with radiosensitive mouse models improve our mechanistic understanding of the dependence of brain damage on radiation quality, thus having important implications in translational research.

Small Molecule Tyrosine Kinase Inhibitors (TKIs) for Glioblastoma Treatment

In the last decade, many small molecules, usually characterized by heterocyclic scaffolds, have been designed and synthesized as tyrosine kinase inhibitors (TKIs). Among them, several compounds have been tested at preclinical and clinical levels to treat glioblastoma multiforme (GBM). GBM is the most common and aggressive type of cancer originating in the brain and has an unfavorable prognosis, with a median survival of 15-16 months and a 5-year survival rate of 5%. Despite recent advances in treating GBM, it represents an incurable disease associated with treatment resistance and high recurrence rates. For these reasons, there is an urgent need for the development of new pharmacological agents to fight this malignancy. In this review, we reported the compounds published in the last five years, which showed promising activity in GBM preclinical models acting as TKIs. We grouped the compounds based on the targeted kinase: first, we reported receptor TKIs and then, cytoplasmic and peculiar kinase inhibitors. For each small molecule, we included the chemical structure, and we schematized the interaction with the target for some representative compounds with the aim of elucidating the mechanism of action. Finally, we cited the most relevant clinical trials.

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.

Pharmacological profiling identifies divergent chemosensitivities of differentiating and maturing iPSC-derived human cortical neuron populations

Neuronal differentiation and maturation are extended developmental processes. To determine whether neurons at different developmental stages have divergent chemosensitivities, we screened differentiating and maturing neuronal populations using a small compound library comprising FDA-approved and investigational drugs. Using a neurotoxicity assay format, both respective neuronal population-based screening campaigns performed robustly (Z-factors = 0.7-0.8), although the hit rate for the differentiating neurons (2.8%) was slightly higher than for maturing neurons (1.9%). While the majority of hits were toxic to both neuronal populations, these hits predominantly represented promiscuous drugs. Other drugs were selectively neurotoxic, with receptor tyrosine kinase inhibitors disproportionally represented after confirmation. Ponatinib and amuvatinib were neuroinhibitory for differentiating and maturing neurons, respectively. Chemoinformatic analyses confirmed differences in potential drug targets that may be differentially expressed during neuronal development. Subsequent studies demonstrated neuronal expression of AXL, an amuvatinib target, in both neuronal populations. However, functional AXL activity was confirmed only in the maturing neuronal population as determined by AXL phosphorylation in response to GAS6, the cognate ligand of AXL, and concurrent STAT3Y705 phosphorylation. Differentiating neurons were unresponsive to the effects of GAS6 suggesting that the AXL-STAT3 signaling axis was nonfunctional. Amuvatinib treatment of maturing neuronal cultures significantly reduced pAXL levels. These studies indicate that neuronal developmental states may exhibit unique chemosensitivities and that drugs may have different neuro-inhibitory effects depending upon the developmental stage of the neuronal population.

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.

Hallmarks of Anaplastic Lymphoma Kinase Inhibitors with Its Quick Emergence of Drug Resistance

Anaplastic lymphoma kinase (ALK) is one of the most popular targets for anticancer therapies. In the past decade, the use of anaplastic lymphoma tyrosine kinase inhibitors (ALK-TKIs), including crizotinib and ceritinib, has been a reliable and standard options for patients with lung cancer, particularly for patients with nonsmall cell lung carcinoma. ALK-targeted therapies initially benefit the patients, yet, resistance eventually occurs. Therefore, resistance mechanisms of ALK-TKIs and the solutions have become a formidable challenge in the development of ALK inhibitors. In this review, based on the knowledge of reported ALK inhibitors, we illustrated the crystal structures of ALK, summarized the resistance mechanisms of ALK-targeted drugs, and proposed potential therapeutic strategies to prevent or overcome the resistance.

Predicting fetal exposure of crizotinib during pregnancy: Combining human ex vivo placenta perfusion data with physiologically-based pharmacokinetic modeling

Commercially available physiologically-based pharmacokinetic (PBPK) modeling platforms increasingly allow estimations of fetal exposure to xenobiotics. We aimed to explore a physiology-based approach in which literature data from ex vivo placenta perfusion studies are used to parameterize Simcyp's pregnancy-PBPK (p-PBPK) model, taking crizotinib as an example. First, a physiologically-based semi-mechanistic placenta (PBMP) model was developed in MATLAB to analyze placenta perfusion data of crizotinib. Mixed-effects modeling was performed to derive intrinsic unbound clearance values across the maternal-placental barrier and fetal-placental barrier. Values were then used for parameterization of the p-PBPK model. The PBMP model adequately described the perfusion data. Clearance was estimated to be 71 mL/min and 535 mL/min for the maternal placental uptake and efflux, and 8 mL/min and 163 mL/min for fetal placental uptake and efflux, respectively. For oral dosing of 250 mg twice daily, p-PBPK modeling predicted a C_max and AUC_0-τ of 0.08 mg/L and 0.78 mg/L*h in the umbilical vein at steady-state, respectively. In placental tissue, a C_max of 5.04 mg/L was predicted. In conclusion, PBMP model-based data analysis and the associated p-PBPK modeling approach illustrate how ex vivo placenta perfusion data may be used for fetal exposure predictions.

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.

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.

Review of Therapeutic Strategies for Anaplastic Lymphoma Kinase-Rearranged Non-Small Cell Lung Cancer

Simple Summary

Anaplastic lymphoma kinase (ALK)-rearranged non-small cell lung cancer (NSCLC) was first reported in 2007. Following the development of crizotinib as a tyrosine kinase inhibitor (TKI) targeting ALK, the treatment of advanced NSCLC with ALK-rearrangements has made remarkable progress. Currently, there are five ALK-TKIs approved by the FDA, and the development of new agents, including fourth-generation TKI, is ongoing. Clinical trials with angiogenesis inhibitors and immune checkpoint inhibitors are also underway, and further progress in the treatment of ALK-rearranged advanced NSCLC is expected. The purpose of this manuscript is to provide information on the recent clinical trials of ALK-TKIs, angiogenesis inhibitors, immune checkpoint inhibitors, and chemotherapy, to describe tissue and liquid biopsy as a method to investigate the mechanisms of resistance against ALK-TKIs and suggest a proposed treatment algorithm.

Abstract

Non-small cell lung cancer (NSCLC) with anaplastic lymphoma kinase rearrangement (ALK) was first reported in 2007. ALK-rearranged NSCLC accounts for about 3–8% of NSCLC. The first-line therapy for ALK-rearranged advanced NSCLC is tyrosine kinase inhibitors (TKI) targeting ALK. Following the development of crizotinib, the first ALK-TKI, patient prognosis has been greatly improved. Currently, five TKIs are approved by the FDA. In addition, clinical trials of the novel TKI, ensartinib, and fourth-generation ALK-TKI for compound ALK mutation are ongoing. Treatment with angiogenesis inhibitors and immune checkpoint inhibitors is also being studied. However, as the disease progresses, cancers tend to develop resistance mechanisms. In addition to ALK mutations, other mechanisms, including the activation of bypass signaling pathways and histological transformation, cause resistance, and the identification of these mechanisms is important in selecting subsequent therapy. Studies on tissue and liquid biopsy have been reported and are expected to be useful tools for identifying resistance mechanisms. The purpose of this manuscript is to provide information on the recent clinical trials of ALK-TKIs, angiogenesis inhibitors, immune checkpoint inhibitors, and chemotherapy to describe tissue and liquid biopsy as a method to investigate the mechanisms of resistance against ALK-TKIs and suggest a proposed treatment algorithm.

A Focus on Regulatory Networks Linking MicroRNAs, Transcription Factors and Target Genes in Neuroblastoma

Neuroblastoma (NB) is a tumor of the peripheral sympathetic nervous system that substantially contributes to childhood cancer mortality. NB originates from neural crest cells (NCCs) undergoing a defective sympathetic neuronal differentiation and although the starting events leading to the development of NB remain to be fully elucidated, the master role of genetic alterations in key oncogenes has been ascertained: (1) amplification and/or over-expression of MYCN, which is strongly associated with tumor progression and invasion; (2) activating mutations, amplification and/or over-expression of ALK, which is involved in tumor initiation, angiogenesis and invasion; (3) amplification and/or over-expression of LIN28B, promoting proliferation and suppression of neuroblast differentiation; (4) mutations and/or over-expression of PHOX2B, which is involved in the regulation of NB differentiation, stemness maintenance, migration and metastasis. Moreover, altered microRNA (miRNA) expression takes part in generating pathogenetic networks, in which the regulatory loops among transcription factors, miRNAs and target genes lead to complex and aberrant oncogene expression that underlies the development of a tumor. In this review, we have focused on the circuitry linking the oncogenic transcription factors MYCN and PHOX2B with their transcriptional targets ALK and LIN28B and the tumor suppressor microRNAs let-7, miR-34 and miR-204, which should act as down-regulators of their expression. We have also looked at the physiologic role of these genetic and epigenetic determinants in NC development, as well as in terminal differentiation, with their pathogenic dysregulation leading to NB oncogenesis.

Expression of Anaplastic Lymphoma Kinase in Astrocytic Tumors (Histopathological and Immunohistochemical Study)

BACKGROUND: Astrocytic tumors are the most common primary brain tumors. Glioblastoma is the most common astrocytic tumor representing the highest World Health Organization (WHO) grade (WHO grade IV) with poor prognosis and short survival time. Anaplastic lymphoma kinase (ALK) has a role in embryonic central nervous system development. ALK receptor is thought to contribute to nervous system function, repair, and metabolic homeostasis and is expressed in high-grade tumors like anaplastic large cell lymphoma that makes it a potential target for therapeutic intervention. AIM: This work aimed to examine the immunohistochemical expression of ALK in astrocytic tumors and its correlation with age, sex, clinical presentation, location, laterality, recurrence, and WHO grade to implicate possible therapeutic potential. METHODS: This retrospective study was conducted on sixty cases of archived, formalin-fixed, paraffin-embedded tissue blocks that included different subtypes and grades of astrocytic tumors. Immunohistochemistry using ALK monoclonal antibody was performed using a standard avidin-biotin-peroxidase system. RESULTS: Of the sixty cases, 57 (95%) cases were negative for ALK, while three (5%) cases are positive for ALK; all showed the strong intensity of expression. No statistically significant association was found between ALK expression and astrocytic tumors in addition to other clinical variables of the studied tumors. CONCLUSIONS: Most cases of astrocytic tumors showed negative ALK expression apart from three positive cases seen in higher WHO grades, especially gliosarcoma. The high number of negative cases for ALK in our study group suggests that ALK expression is not associated with a prognostic significance toward astrocytic tumors whatever its grade.

ALK Rearrangement-Positive Pancreatic Cancer with Brain Metastasis Has Remarkable Response to ALK Inhibitors: A Case Report

Patients with metastatic pancreatic cancer typically have poor prognosis due to the limited effectiveness of existing treatment options. ALK rearrangement–positive is rare in pancreatic cancer, but may occur in those with KRAS-wild type. We present a 34-year-old young man with ALK rearrangement–positive and KRAS-wild pancreatic cancer who had a remarkable response to crizotinib after resistance to prior chemotherapy and re-response to alectinib after brain metastases developed. This clinical observation suggests that comprehensive molecular profiling to guide targeted therapies is not only feasible, but also significantly improves survival outcomes for a subgroup of patients with pancreatic cancer.

Transcriptome Regulation by Oncogenic ALK Pathway in Mammalian Cortical Development Revealed by Single-Cell RNA Sequencing

Precise regulation of embryonic neurodevelopment is crucial for proper structural organization and functioning of the adult brain. The key molecular machinery orchestrating this process remains unclear. Anaplastic lymphoma kinase (ALK) is an oncogenic receptor-type protein tyrosine kinase that is specifically and transiently expressed in developing nervous system. However, its role in the mammalian brain development is unknown. We found that transient embryonic ALK inactivation caused long-lasting abnormalities in the adult mouse brain, including impaired neuronal connectivity and cognition, along with delayed neuronal migration and decreased neuronal proliferation during neurodevelopment. scRNA-seq on human cerebral organoids revealed a delayed transition of cell-type composition. Molecular characterization identified a group of differentially expressed genes (DEGs) that were temporally regulated by ALK at distinct developmental stages. In addition to oncogenes, many DEGs found by scRNA-seq are associated with neurological or neuropsychiatric disorders. Our study demonstrates a pivotal role of oncogenic ALK pathway in neurodevelopment and characterized cell-type-specific transcriptome regulated by ALK for better understanding mammalian cortical development.

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.

Temozolomide treatment combined with AZD3463 shows synergistic effect in glioblastoma cells

Temozolomide (TMZ) is used in the standard therapy regimen for patients with glioblastoma (GBM). However, some GBM patients do not respond to TMZ therapy. The combining therapeutic agents in GBM treatment are attracting considerable interest due to TMZ resistance. This study aims to identify the combinatorial effect of TMZ and AZD3463 on the viability of the T98G GBM cells. The cytotoxic effects of compounds were determined by using WST-8 assay. Flow cytometry was used to determine apoptosis and cell cycle profiles after treatments. Real-time PCR was used to identify mRNA expression of genes in the PI3K/AKT signaling pathway after treatments. IC₅₀ concentrations of TMZ and AZD3463 were found to be 1.54 mM and 529 nM after incubation for 48 h, respectively. The combination treatment showed a synergistic effect on reducing the viability of GBM cells. Each one of TMZ, AZD3463, and combination treatments induced apoptosis. Treatments, either alone or the combination of these agents, caused the cell cycle arrest in distinct phases. TMZ and AZD3463 treatments, either alone or in combination, downregulated mRNA expression of genes in the PI3K/AKT signaling pathway. The combination of TMZ with AZD3463 may increase the efficacy of single TMZ treatment in GBM cells due to decreased expression of genes in the PI3K/AKT signaling pathway that is responsible for drug resistance and intratumoral heterogeneity.

Midkine: The Who, What, Where, and When of a Promising Neurotrophic Therapy for Perinatal Brain Injury

Midkine (MK) is a small secreted heparin-binding protein highly expressed during embryonic/fetal development which, through interactions with multiple cell surface receptors promotes growth through effects on cell proliferation, migration, and differentiation. MK is upregulated in the adult central nervous system (CNS) after multiple types of experimental injury and has neuroprotective and neuroregenerative properties. The potential for MK as a therapy for developmental brain injury is largely unknown. This review discusses what is known of MK's expression and actions in the developing brain, areas for future research, and the potential for using MK as a therapeutic agent to ameliorate the effects of brain damage caused by insults such as birth-related hypoxia and inflammation.

Making NSCLC Crystal Clear: How Kinase Structures Revolutionized Lung Cancer Treatment

The parallel advances of different scientific fields provide a contemporary scenario where collaboration is not a differential, but actually a requirement. In this context, crystallography has had a major contribution on the medical sciences, providing a “face” for targets of diseases that previously were known solely by name or sequence. Worldwide, cancer still leads the number of annual deaths, with 9.6 million associated deaths, with a major contribution from lung cancer and its 1.7 million deaths. Since the relationship between cancer and kinases was unraveled, these proteins have been extensively explored and became associated with drugs that later attained blockbuster status. Crystallographic structures of kinases related to lung cancer and their developed and marketed drugs provided insight on their conformation in the absence or presence of small molecules. Notwithstanding, these structures were also of service once the initially highly successful drugs started to lose their effectiveness in the emergence of mutations. This review focuses on a subclassification of lung cancer, non-small cell lung cancer (NSCLC), and major oncogenic driver mutations in kinases, and how crystallographic structures can be used, not only to provide awareness of the function and inhibition of these mutations, but also how these structures can be used in further computational studies aiming at addressing these novel mutations in the field of personalized medicine.

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.

A Computer - Aided Drug Designing for Pharmacological Inhibition of Mutant ALK for the Treatment of Non-small Cell Lung Cancer

Background:

Lung cancer is the most common among all the types of cancer worldwide with 1.8 million people diagnosed every year, leading to 1.6 million deaths every year according to the American cancer society. The involvement of mutated Anaplasic Lymphoma Kinase (ALK) positive fusion protein in the progression of NSCLC has made a propitious target to inhibit and treat NSCLC. In the present study, the main motif is to screen the most effective inhibitor against ALK protein with the potential pharmacological profile. The ligands selected were docked with Molegro Virtual Docker (MVD) and CEP-37440 (PubChem CID- 71721648) was the best docked pre-established compound with a permissible pharmacological profile.

Methods:

The selected ligands were docked with Molegro Virtual Docker (MVD). With reference to the obtained compound with the lowest re-rank score, PubChem database was virtually screened to retrieve a large set of similar compounds which were docked to find the compound with higher affinity. Further comparative studies and in silico prediction included pharmacophore studies, proximity energy parameters, ADMET and BOILED-egg plot analysis.

Results:

CEP-37440 (PubChem CID- 71721648) was the best docked pre-established compound with preferable pharmacological profile and PubChem compound CID-123449015 came out as the most efficient virtually screened inhibitor. Interestingly, the contours of the virtual screened compound PubChem CID- 123449015 fall within our desired high volume cavity of protein having admirable property to control the ALK regulation to prevent carcinogenesis in NSCLC. BOILED-Egg plot analysis depicts that both the compounds have analogous characteristics in the divergent aspects. Moreover, in the evaluations of Blood Brain Barrier, Human Intestinal Absorption, AMES toxicity, and LD50, the virtually screened compound (PubChem CID-123449015) was found within high optimization.

Conclusion:

These investigations denote that the virtually screened compound (PubChem CID- 123449015) is more efficient to be a better prospective candidate for NSCLC treatment having good pharmacological profile than the pre-established compound CEP-37440 (PubChem CID- 71721648) with low re-rank score. The identified virtually screened compound has high potential to act as an ALK inhibitor and can show promising results in the research of non-small cell lung cancer (NSCLC).

Anaplastic lymphoma kinase fusions: Roles in cancer and therapeutic perspectives

Receptor tyrosine kinase (RTK) anaplastic lymphoma kinase (ALK) serves a crucial role in brain development. ALK is located on the short arm of chromosome 2 (2p23) and exchange of chromosomal segments with other genes, including nucleophosmin (NPM), echinoderm microtubule-associated protein-like 4 (EML4) and Trk-fused gene (TFG), readily occurs. Such chromosomal translocation results in the formation of chimeric X-ALK fusion oncoproteins, which possess potential oncogenic functions due to constitutive activation of ALK kinase. These proteins contribute to the pathogenesis of various hematological malignancies and solid tumors, including lymphoma, lung cancer, inflammatory myofibroblastic tumors (IMTs), Spitz tumors, renal carcinoma, thyroid cancer, digestive tract cancer, breast cancer, leukemia and ovarian carcinoma. Targeting of ALK fusion oncoproteins exclusively, or in combination with ALK kinase inhibitors including crizotinib, is the most common therapeutic strategy. As is often the case for small-molecule tyrosine kinase inhibitors (TKIs), drug resistance eventually develops via an adaptive secondary mutation in the ALK fusion oncogene, or through engagement of alternative signaling mechanisms. The updated mechanisms of a variety of ALK fusions in tumorigenesis, proliferation and metastasis, in addition to targeted therapies are discussed below.

Neuroblastoma Origin and Therapeutic Targets for Immunotherapy

Neuroblastoma is a pediatric solid cancer of heterogeneous clinical behavior. The unique features of this type of cancer frequently hamper the process of determining clinical presentation and predicting therapy effectiveness. The tumor can spontaneously regress without treatment or actively develop and give rise to metastases despite aggressive multimodal therapy. In recent years, immunotherapy has become one of the most promising approaches to the treatment of neuroblastoma. Still, only one drug for targeted immunotherapy of neuroblastoma, chimeric monoclonal GD2-specific antibodies, is used in the clinic today, and its application has significant limitations. In this regard, the development of effective and safe GD2-targeted immunotherapies and analysis of other potential molecular targets for the treatment of neuroblastoma represents an important and topical task. The review summarizes biological characteristics of the origin and development of neuroblastoma and outlines molecular markers of neuroblastoma and modern immunotherapy approaches directed towards these markers.

Tumor Resistance against ALK Targeted Therapy-Where It Comes From and Where It Goes

Anaplastic lymphoma kinase (ALK) is a validated molecular target in several ALK-rearranged malignancies, particularly in non-small-cell lung cancer (NSCLC), which has generated considerable interest and effort in developing ALK tyrosine kinase inhibitors (TKI). Crizotinib was the first ALK inhibitor to receive FDA approval for ALK-positive NSCLC patients treatment. However, the clinical benefit observed in targeting ALK in NSCLC is almost universally limited by the emergence of drug resistance with a median of occurrence of approximately 10 months after the initiation of therapy. Thus, to overcome crizotinib resistance, second/third-generation ALK inhibitors have been developed and received, or are close to receiving, FDA approval. However, even when treated with these new inhibitors tumors became resistant, both in vitro and in clinical settings. The elucidation of the diverse mechanisms through which resistance to ALK TKI emerges, has informed the design of novel therapeutic strategies to improve patients disease outcome. This review summarizes the currently available knowledge regarding ALK physiologic function/structure and neoplastic transforming role, as well as an update on ALK inhibitors and resistance mechanisms along with possible therapeutic strategies that may overcome the development of resistance.

The ALK receptor in sympathetic neuron development and neuroblastoma

The ALK gene encodes a tyrosine kinase receptor characterized by an expression pattern mainly restricted to the developing central and peripheral nervous systems. In 2008, the discovery of ALK activating mutations in neuroblastoma, a tumor of the sympathetic nervous system, represented a breakthrough in the understanding of the pathogenesis of this pediatric cancer and established mutated ALK as a tractable therapeutic target for precision medicine. Subsequent studies addressed the identity of ALK ligands, as well as its physiological function in the sympathoadrenal lineage, its role in neuroblastoma development and the signaling pathways triggered by mutated ALK. This review focuses on these different aspects of the ALK biology and summarizes the various therapeutic strategies relying on ALK inhibition in neuroblastoma, either as monotherapies or combinatory treatments.

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

Neuroblastoma is a pediatric tumor arising from the neural crest. Dysregulation of the receptor tyrosine kinase ALK has been linked to neuroblastoma, making it important to understand its function in native conditions. In zebrafish, a related receptor—Ltk—is also expressed in neural crest and regulates development of specific pigment cells—iridophores. Ligands activating human ALK were recently identified as the ALKAL proteins (FAM150, AUG) by biochemical means. Our data show that this ligand–receptor pair functions in vivo in the neural crest of zebrafish to drive development of iridophores. Removal of Ltk or all three zebrafish ALKALs results in larvae completely lacking these cells. Using Drosophila and human cell lines, we show evolutionary conservation of this important interaction.

Mutations in anaplastic lymphoma kinase (ALK) are implicated in somatic and familial neuroblastoma, a pediatric tumor of neural crest-derived tissues. Recently, biochemical analyses have identified secreted small ALKAL proteins (FAM150, AUG) as potential ligands for human ALK and the related leukocyte tyrosine kinase (LTK). In the zebrafish Danio rerio, DrLtk, which is similar to human ALK in sequence and domain structure, controls the development of iridophores, neural crest-derived pigment cells. Hence, the zebrafish system allows studying Alk/Ltk and Alkals involvement in neural crest regulation in vivo. Using zebrafish pigment pattern formation, Drosophila eye patterning, and cell culture-based assays, we show that zebrafish Alkals potently activate zebrafish Ltk and human ALK driving downstream signaling events. Overexpression of the three DrAlkals cause ectopic iridophore development, whereas loss-of-function alleles lead to spatially distinct patterns of iridophore loss in zebrafish larvae and adults. alkal loss-of-function triple mutants completely lack iridophores and are larval lethal as is the case for ltk null mutants. Our results provide in vivo evidence of (i) activation of ALK/LTK family receptors by ALKALs and (ii) an involvement of these ligand–receptor complexes in neural crest development.

High expression of β-catenin contributes to the crizotinib resistant phenotype in the stem-like cell population in neuroblastoma

ALK has been identified as a novel therapeutic target in neuroblastoma (NB), but resistance to ALK inhibitors (such as crizotinib) is well recognized. We recently published that the crizotinib sensitivity in NB cells strongly correlates with the crizotinib—ALK binding, and β-catenin effectively hinders this interaction and confers crizotinib resistance. Here, we asked if these observations hold true for the stem-like cells in NB cells, which were purified based on their responsiveness to a Sox2 reporter. Compared to bulk, reporter unresponsive (RU) cells, reporter responsive (RR) cells had significantly higher neurosphere formation ability, expression of CD133/nestin and chemo-resistance. Using the cellular thermal shift assay, we found that RR cells exhibited significantly weaker crizotinib—ALK binding and higher crizotinib resistance than RU cells. The suboptimal crizotinib—ALK binding in RR cells can be attributed to their high β-catenin expression, since siRNA knockdown of β-catenin restored the crizotinib—ALK binding and lowered the crizotinib resistance to the level of RU cells. Enforced expression of β-catenin in RU cells resulted in the opposite effects. To conclude, high expression of β-catenin in the stem-like NB cells contributes to their crizotinib resistance. Combining β-catenin inhibitors and ALK inhibitors may be useful in treating NB patients.

The role of the ALK receptor in cancer biology

A vast array of oncogenic variants has been identified for anaplastic lymphoma kinase (ALK). Therefore, there is a need to better understand the role of ALK in cancer biology in order to optimise treatment strategies. This review summarises the latest research on the receptor tyrosine kinase ALK, and how this information can guide the management of patients with cancer that is ALK-positive. A variety of ALK gene alterations have been described across a range of tumour types, including point mutations, deletions and rearrangements. A wide variety of ALK fusions, in which the kinase domain of ALK and the amino-terminal portion of various protein partners are fused, occur in cancer, with echinoderm microtubule-associated protein-like 4 (EML4)-ALK being the most prevalent in non-small-cell lung cancer (NSCLC). Different ALK fusion proteins can mediate different signalling outputs, depending on properties such as subcellular localisation and protein stability. The ALK fusions found in tumours lack spatial and temporal regulation, which can also affect dimerisation and substrate specificity. Two ALK tyrosine kinase inhibitors (TKIs), crizotinib and ceritinib, are currently approved in Europe for use in ALK-positive NSCLC and several others are in development. These ALK TKIs bind slightly differently within the ATP-binding pocket of the ALK kinase domain and are associated with the emergence of different resistance mutation patterns during therapy. This emphasises the need to tailor the sequence of ALK TKIs according to the ALK signature of each patient. Research into the oncogenic functions of ALK, and fast paced development of ALK inhibitors, has substantially improved outcomes for patients with ALK-positive NSCLC. Limited data are available surrounding the physiological ligand-stimulated activation of ALK signalling and further research is needed. Understanding the role of ALK in tumour biology is key to further optimising therapeutic strategies for ALK-positive disease.

Alk and Ltk ligands are essential for iridophore development in zebrafish mediated by the receptor tyrosine kinase Ltk

Anaplastic lymphoma kinase (Alk) and leucocyte tyrosine kinase (Ltk) were identified as "orphan" receptor tyrosine kinases (RTKs) with oncogenic potential. Recently ALKAL1 and ALKAL2 (also named "augmentor-β" and "augmentor-α" or "FAM150A" and "FAM150B," respectively) were discovered as physiological ligands of Alk and Ltk. Here, we employ zebrafish as a model system to explore the physiological function and to characterize in vivo links between Alk and Ltk with their ligands. Unlike the two ligands encoded by mammalian genomes, the zebrafish genome contains three genes: aug-α1, aug-α2, and aug-β Our experiments demonstrate that these ligands play an important role in zebrafish pigment development. Deficiency in aug-α1, aug-α2, and aug-β results in strong impairment in iridophore patterning of embryonic and adult zebrafish that is phenocopied in zebrafish deficient in Ltk. We show that aug-α1 and aug-α2 are essential for embryonic iridophore development and adult body coloration. In contrast, aug-α2 and aug-β are essential for iridophore formation in the adult eye. Importantly, these processes are entirely mediated by Ltk and not by Alk. These experiments establish a physiological link between augmentor ligands and Ltk and demonstrate that particular augmentors activate Ltk in a tissue-specific context to induce iridophore differentiation from neural crest-derived cells and pigment progenitor cells.

Anaplastic Lymphoma Kinase Is a Regulator of Alcohol Consumption and Excitatory Synaptic Plasticity in the Nucleus Accumbens Shell

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase recently implicated in biochemical, physiological, and behavioral responses to ethanol. Thus, manipulation of ALK signaling may represent a novel approach to treating alcohol use disorder (AUD). Ethanol induces adaptations in glutamatergic synapses onto nucleus accumbens shell (NAcSh) medium spiny neurons (MSNs), and putative targets for treating AUD may be validated for further development by assessing how their manipulation modulates accumbal glutamatergic synaptic transmission and plasticity. Here, we report that Alk knockout (Alk^KO) mice consumed greater doses of ethanol, relative to wild-type (Alk^WT) mice, in an operant self-administration model. Using ex vivo electrophysiology to examine excitatory synaptic transmission and plasticity at NAcSh MSNs that express dopamine D1 receptors (D1MSNs), we found that the amplitude of spontaneous excitatory post-synaptic currents (EPSCs) in NAcSh D1MSNs was elevated in Alk^KO mice and in the presence of an ALK inhibitor, TAE684. Furthermore, when ALK was absent or inhibited, glutamatergic synaptic plasticity – long-term depression of evoked EPSCs – in D1MSNs was attenuated. Thus, loss of ALK activity in mice is associated with elevated ethanol consumption and enhanced excitatory transmission in NAcSh D1MSNs. These findings add to the mounting evidence of a relationship between excitatory synaptic transmission onto NAcSh D1MSNs and ethanol consumption, point toward ALK as one important molecular mediator of this interaction, and further validate ALK as a target for therapeutic intervention in the treatment of AUD.

ALK: a tyrosine kinase target for cancer therapy

The anaplastic lymphoma kinase (ALK) gene plays an important physiologic role in the development of the brain and can be oncogenically altered in several malignancies, including non-small-cell lung cancer (NSCLC) and anaplastic large cell lymphomas (ALCL). Most prevalent ALK alterations are chromosomal rearrangements resulting in fusion genes, as seen in ALCL and NSCLC. In other tumors, ALK copy-number gains and activating ALK mutations have been described. Dramatic and often prolonged responses are seen in patients with ALK alterations when treated with ALK inhibitors. Three of these—crizotinib, ceritinib, and alectinib—are now FDA approved for the treatment of metastatic NSCLC positive for ALK fusions. However, the emergence of resistance is universal. Newer ALK inhibitors and other targeting strategies are being developed to counteract the newly emergent mechanism(s) of ALK inhibitor resistance. This review outlines the recent developments in our understanding and treatment of tumors with ALK alterations.

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.

Neuronal leucine-rich repeat 1 negatively regulates anaplastic lymphoma kinase in neuroblastoma

In neuroblastoma (NB), one of the most common paediatric solid tumours, activation of anaplastic lymphoma kinase (ALK) is often associated with poor outcomes. Although genetic studies have identified copy number alteration and nonsynonymous mutations of ALK, the regulatory mechanism of ALK signalling at protein levels is largely elusive. Neuronal leucine-rich repeat 1 (NLRR1) is a type 1 transmembrane protein that is highly expressed in unfavourable NB and potentially influences receptor tyrosine kinase signalling. Here, we showed that NLRR1 and ALK exhibited a mutually exclusive expression pattern in primary NB tissues by immunohistochemistry. Moreover, dorsal root ganglia of Nlrr1+/+ and Nlrr1−/− mice displayed the opposite expression patterns of Nlrr1 and Alk. Of interest, NLRR1 physically interacted with ALK in vitro through its extracellular region. Notably, the NLRR1 ectodomain impaired ALK phosphorylation and proliferation of ALK-mutated NB cells. A newly identified cleavage of the NLRR1 ectodomain also supported NLRR1-mediated ALK signal regulation in trans. Thus, we conclude that NLRR1 appears to be an extracellular negative regulator of ALK signalling in NB and neuronal development. Our findings may be beneficial to comprehend NB heterogeneity and to develop a novel therapy against unfavourable NB.

Role of the p55-gamma subunit of PI3K in ALK-induced cell migration: RNAi-based selection of cell migration regulators

Recently, unbiased functional genetic selection identified novel cell migration-regulating genes. This RNAi-based functional selection was performed using 63,996 pooled lentiviral shRNAs targeting 21,332 mouse genes. After five rounds of selection using cells with accelerated or impaired migration, shRNAs were retrieved and identified by half-hairpin barcode sequencing using cells with the selected phenotypes. This selection process led to the identification of 29 novel cell migration regulators. One of these candidates, anaplastic lymphoma kinase (ALK), was further investigated. Subsequent studies revealed that ALK promoted cell migration through the PI3K-AKT pathway via the p55γ regulatory subunit of PI3K, rather than more commonly used p85 subunit. Western blot and immunohistochemistry studies using mouse brain tissues revealed similar temporal expression patterns of ALK, phospho-p55γ, and phospho-AKT during different stages of development. These data support an important role for the p55γ subunit of PI3K in ALK-induced cell migration during brain development.

Using In Vitro Electrophysiology to Screen Medications: Accumbal Plasticity as an Engram of Alcohol Dependence

The nucleus accumbens (NAc) is a central component of the mesocorticolimbic reward system. Increasing evidence strongly implicates long-term synaptic neuroadaptations in glutamatergic excitatory activity of the NAc shell and/or core medium spiny neurons in response to chronic drug and alcohol exposure. Such neuroadaptations likely play a critical role in the development and expression of drug-seeking behaviors. We have observed unique cell-type-specific bidirectional changes in NAc synaptic plasticity (metaplasticity) following acute and chronic intermittent ethanol exposure. Other investigators have also previously observed similar metaplasticity in the NAc following exposure to psychostimulants, opiates, and amazingly, even following an anhedonia-inducing experience. Considering that the proteome of the postsynaptic density likely contains hundreds of biochemicals, proteins and other components and regulators, we believe that there is a large number of potential molecular sites through which accumbal metaplasticity may be involved in chronic alcohol abuse. Many of our companion laboratories are now engaged in identifying and screening medications targeting candidate genes and its products previously linked to maladaptive alcohol phenotypes. We hypothesize that if manipulation of such target genes and their products change NAc plasticity, then that observation constitutes an important validation step for the development of novel therapeutics to treat alcohol dependence.

Crizotinib Synergizes with Chemotherapy in Preclinical Models of Neuroblastoma

PURPOSE

The presence of an ALK aberration correlates with inferior survival for patients with high-risk neuroblastoma. The emergence of ALK inhibitors such as crizotinib has provided novel treatment opportunities. However, certain ALK mutations result in de novo crizotinib resistance, and a phase I trial of crizotinib showed a lack of response in patients harboring those ALK mutations. Thus, understanding mechanisms of resistance and defining circumvention strategies for the clinic is critical.

EXPERIMENTAL DESIGN

The sensitivity of human neuroblastoma-derived cell lines, cell line-derived, and patient-derived xenograft (PDX) models with varying ALK statuses to crizotinib combined with topotecan and cyclophosphamide (topo/cyclo) was examined. Cultured cells and xenografts were evaluated for effects of these drugs on proliferation, signaling, and cell death, and assessment of synergy.

RESULTS

In neuroblastoma murine xenografts harboring the most common ALK mutations, including those mutations associated with resistance to crizotinib (but not in those with wild-type ALK), crizotinib combined with topo/cyclo enhanced tumor responses and mouse event-free survival. Crizotinib + topo/cyclo showed synergistic cytotoxicity and higher caspase-dependent apoptosis than crizotinib or topo/cyclo alone in neuroblastoma cell lines with ALK aberrations (mutation or amplification).

CONCLUSIONS

Combining crizotinib with chemotherapeutic agents commonly used in treating newly diagnosed patients with high-risk neuroblastoma restores sensitivity in preclinical models harboring both sensitive ALK aberrations and de novo-resistant ALK mutations. These data support clinical testing of crizotinib and conventional chemotherapy with the goal of integrating ALK inhibition into multiagent therapy for ALK-aberrant neuroblastoma patients.

Anaplastic lymphoma kinase inhibitors

The anaplastic lymphoma kinase (ALK) gene is a member of the insulin receptor superfamily and it has been associated with more than twenty distinct chimera, including established drivers of several human cancers. Multiple clinical trials have proven that the pharmacological inhibition of ALK signaling leads to remarkable clinical improvement and improves the quality of life of ALK+ cancer patients. Crizotinib was the first ALKi to achieve approval from the Food and Drug Administration, although additional compounds are now moving into diversified clinical trials.

Therapeutic management of ALK+ nonsmall cell lung cancer patients

With therapeutic approaches based on oncogene addiction offering significant anticancer benefit, the identification of anaplastic lymphoma kinase (ALK) rearrangements is a key aspect of the management of lung cancers. The EML4-ALK gene fusion is detected in 4-8% of all lung cancers, predominantly in light smokers or nonsmokers. Crizotinib, the first agent to be approved in this indication, is associated with a median progression-free survival of 10.9 months when given as first-line treatment and 7.7 months when administered after chemotherapy. Median overall survival with crizotinib in the second-line setting is 20.3 months. Second-generation ALK inhibitors are currently being evaluated, with early studies giving impressive results, notably in patients resistant to crizotinib or with brain metastases. Among available chemotherapies, pemetrexed appears to be particularly active in this population. Despite this progress, several questions remain unanswered. What detection strategies should be favoured? What underlies the mechanisms of resistance and what options are available to overcome them? What are the best approaches for progressing patients? This review provides an overview of current data in the literature and addresses these questions.

Wild-type ALK and activating ALK-R1275Q and ALK-F1174L mutations upregulate Myc and initiate tumor formation in murine neural crest progenitor cells

The anaplastic lymphoma kinase (ALK) gene is overexpressed, mutated or amplified in most neuroblastoma (NB), a pediatric neural crest-derived embryonal tumor. The two most frequent mutations, ALK-F1174L and ALK-R1275Q, contribute to NB tumorigenesis in mouse models, and cooperate with MYCN in the oncogenic process. However, the precise role of activating ALK mutations or ALK-wt overexpression in NB tumor initiation needs further clarification.

Human ALK-wt, ALK-F1174L, or ALK-R1275Q were stably expressed in murine neural crest progenitor cells (NCPC), MONC-1 or JoMa1, immortalized with v-Myc or Tamoxifen-inducible Myc-ER^T, respectively. While orthotopic implantations of MONC-1 parental cells in nude mice generated various tumor types, such as NB, osteo/chondrosarcoma, and undifferentiated tumors, due to v-Myc oncogenic activity, MONC-1-ALK-F1174L cells only produced undifferentiated tumors. Furthermore, our data represent the first demonstration of ALK-wt transforming capacity, as ALK-wt expression in JoMa1 cells, likewise ALK-F1174L, or ALK-R1275Q, in absence of exogenous Myc-ER^T activity, was sufficient to induce the formation of aggressive and undifferentiated neural crest cell-derived tumors, but not to drive NB development. Interestingly, JoMa1-ALK tumors and their derived cell lines upregulated Myc endogenous expression, resulting from ALK activation, and both ALK and Myc activities were necessary to confer tumorigenic properties on tumor-derived JoMa1 cells in vitro.

RNAi-based functional selection identifies novel cell migration determinants dependent on PI3K and AKT pathways

Lentiviral short hairpin RNA (shRNA)-mediated genetic screening is a powerful tool for identifying loss-of-function phenotype in mammalian cells. Here, we report the identification of 91 cell migration-regulating genes using unbiased genome-wide functional genetic selection. Individual knockdown or cDNA overexpression of a set of 10 candidates reveals that most of these cell migration determinants are strongly dependent on the PI3K/PTEN/AKT pathway and on their downstream signals, such as FOXO1 and p70S6K1. ALK, one of the cell migration promoting genes, uniquely uses p55γ regulatory subunit of PI3K, rather than more common p85 subunit, to trigger the activation of the PI3K-AKT pathway. Our method enables the rapid and cost-effective genome-wide selection of cell migration regulators. Our results emphasize the importance of the PI3K/PTEN/AKT pathway as a point of convergence for multiple regulators of cell migration.

The midkine family of growth factors: diverse roles in nervous system formation and maintenance

Midkines are heparin-binding growth factors involved in a wide range of biological processes. Originally identified as retinoic acid inducible genes, midkines are widely expressed during embryogenesis with particularly high levels in the developing nervous system. During postnatal stages, midkine expression generally ceases but is often up-regulated under disease conditions, most notably those affecting the nervous system. Midkines are known as neurotrophic factors, as they promote neurite outgrowth and neuron survival in cell culture. Surprisingly, however, mouse embryos deficient for midkine (knockout mice) are phenotypically normal, which suggests functional redundancy by related growth factors. During adult stages, on the other hand, midkine knockout mice develop striking deficits in neuroprotection and regeneration after drug-induced neurotoxicity and injury. The detailed mechanisms by which midkine controls neuron formation, differentiation and maintenance remain unclear. Recent studies in zebrafish and chick have provided important insight into the role of midkine and its putative receptor, anaplastic lymphoma kinase, in cell cycle control in the central and peripheral nervous systems. A recent structural analysis of zebrafish midkine furthermore revealed essential protein domains required for biological activity that serve as promising novel targets for future drug designs. This review will summarize latest findings in the field that help to better understand the diverse roles of midkine in nervous system formation and maintenance.

LINKED ARTICLES

This article is part of a themed section on Midkine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-4.

Sequential axon-derived signals couple target survival and layer specificity in the Drosophila visual system

Neural circuit formation relies on interactions between axons and cells within the target field. While it is well established that target-derived signals act on axons to regulate circuit assembly, the extent to which axon-derived signals control circuit formation is not known. In the Drosophila visual system, anterograde signals numerically match R1-R6 photoreceptors with their targets by controlling target proliferation and neuronal differentiation. Here we demonstrate that additional axon-derived signals selectively couple target survival with layer specificity. We show that Jelly belly (Jeb) produced by R1-R6 axons interacts with its receptor, anaplastic lymphoma kinase (Alk), on budding dendrites to control survival of L3 neurons, one of three postsynaptic targets. L3 axons then produce Netrin, which regulates the layer-specific targeting of another neuron within the same circuit. We propose that a cascade of axon-derived signals, regulating diverse cellular processes, provides a strategy for coordinating circuit assembly across different regions of the nervous system.

Building a brain under nutritional restriction: insights on sparing and plasticity from Drosophila studies

While the growth of the developing brain is known to be well-protected compared to other organs in the face of nutrient restriction (NR), careful analysis has revealed a range of structural alterations and long-term neurological defects. Yet, despite intensive studies, little is known about the basic principles that govern brain development under nutrient deprivation. For over 20 years, Drosophila has proved to be a useful model for investigating how a functional nervous system develops from a restricted number of neural stem cells (NSCs). Recently, a few studies have started to uncover molecular mechanisms as well as region-specific adaptive strategies that preserve brain functionality and neuronal repertoire under NR, while modulating neuron numbers. Here, we review the developmental constraints that condition the response of the developing brain to NR. We then analyze the recent Drosophila work to highlight key principles that drive sparing and plasticity in different regions of the central nervous system (CNS). As simple animal models start to build a more integrated picture, understanding how the developing brain copes with NR could help in defining strategies to limit damage and improve brain recovery after birth.

Mechanistic insight into ALK receptor tyrosine kinase in human cancer biology

The burgeoning field of anaplastic lymphoma kinase (ALK) in cancer encompasses many cancer types, from very rare cancers to the more prevalent non-small-cell lung cancer (NSCLC). The common activation of ALK has led to the use of the ALK tyrosine kinase inhibitor (TKI) crizotinib in a range of patient populations and to the rapid development of second-generation drugs targeting ALK. In this Review, we discuss our current understanding of ALK function in human cancer and the implications for tumour treatment.