Role of the subcellular localization of ALK tyrosine kinase domain in neuronal differentiation of PC12 cells

Anaplastic lymphoma kinase overexpression enhances aggressive phenotypic characteristics of endometrial carcinoma

BACKGROUND

Although anaplastic lymphoma kinase (ALK) is overexpressed in several primary solid tumor types, its role in endometrial carcinoma (Em Ca) remains unclear.

METHODS

We evaluated expression of ALK and its related molecules in clinical samples consisting of 168 Em Ca tissues. We also used Em Ca cell lines to evaluate the functional role of ALK.

RESULTS

Cytoplasmic ALK immunoreactivity in the absence of chromosomal rearrangement was positively correlated with ALK mRNA expression, and was significantly higher in Grade (G) 3 Em Ca than in G1 or G2 tumors. ALK immunoreactivity was also significantly associated with expression of cancer stem cell (CSC)-related molecules (cytoplasmic CD133, ALDH1, Sox2) and neuroendocrine markers (CD56 and synaptophysin). Although the proliferative index was significantly higher in ALK-positive Em Ca when compared to ALK- negative malignancies, there was no association between ALK expression and other clinicopathological factors in this disease. In Em Ca cell lines, full-length ALK overexpression increased proliferation, decreased susceptibility to apoptosis, enhanced cancer stem cell features, and accelerated cell mobility, whereas these phenotypes were abrogated in ALK-knockdown cells. Finally, patients with tumors harboring either wild-type ALK or high ALK mRNA expression had a poorer prognosis than those with either mutant ALK or low ALK mRNA expression.

CONCLUSION

Full-length ALK overexpression occurs in a subset of Em Ca, particularly in G3 tumors, and contributes to the establishment and maintenance of aggressive phenotypic characteristics through modulation of several biological processes.

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.

Anaplastic Lymphoma Kinase Overexpression Is Associated with Aggressive Phenotypic Characteristics of Ovarian High-Grade Serous Carcinoma

Deregulated full-length anaplastic lymphoma kinase (ALK) overexpression has been found in some primary solid tumors, but little is known about its role in ovarian high-grade serous carcinoma (HGSC). Herein, we focused on the functional roles of ALK in HGSC. Cytoplasmic ALK immunoreactivity without chromosomal rearrangement and gene mutations was significantly higher in HGSC compared with non-HGSC type ovarian carcinomas, and was significantly associated with several unfavorable clinicopathologic factors and poor prognosis. HGSC cell lines stably overexpressing ALK exhibited increased cell proliferation, enhanced cancer stem cell features, and accelerated cell mobility, whereas these phenotypes were abrogated in ALK-knockdown cells. Expression of the nervous system-associated gene, ELAVL3, and the corresponding protein (commonly known as HuC) was significantly increased in cells overexpressing ALK. There was increased expression of Sox2 and Sox3 (genes associated with the neural progenitor population) in ALK-overexpressing but not ALK-knockdown cells. Furthermore, overexpression of Sox2 or Sox3 enhanced both ALK and ELAVL3 promoter activities, suggesting the existence of ALK/Sox/HuC signaling loops. Finally, ALK overexpression was due to increased expression of neuroendocrine markers, including synaptophysin, CD56, and BCL2, in HGSC tissues. These findings suggest that overexpression of full-length ALK may influence the biological behavior of HGSC through cooperation with ELAVL3 and Sox factors, leading to establishment and maintenance of the aggressive phenotypic characteristics of HGSC.

Associative Learning Requires Neurofibromin to Modulate GABAergic Inputs to Drosophila Mushroom Bodies

Cognitive dysfunction is among the hallmark symptoms of Neurofibromatosis 1, and accordingly, loss of the Drosophila melanogaster ortholog of Neurofibromin 1 (dNf1) precipitates associative learning deficits. However, the affected circuitry in the adult CNS remained unclear and the compromised mechanisms debatable. Although the main evolutionarily conserved function attributed to Nf1 is to inactivate Ras, decreased cAMP signaling on its loss has been thought to underlie impaired learning. Using mixed sex populations, we determine that dNf1 loss results in excess GABAergic signaling to the central for associative learning mushroom body (MB) neurons, apparently suppressing learning. dNf1 is necessary and sufficient for learning within these non-MB neurons, as a dAlk and Ras1-dependent, but PKA-independent modulator of GABAergic neurotransmission. Surprisingly, we also uncovered and discuss a postsynaptic Ras1-dependent, but dNf1-independnet signaling within the MBs that apparently responds to presynaptic GABA levels and contributes to the learning deficit of the mutants.

ERICH3: vesicular association and antidepressant treatment response

Selective serotonin reuptake inhibitors (SSRIs) are standard of care for major depressive disorder (MDD) pharmacotherapy, but only approximately half of these patients remit on SSRI therapy. Our previous genome-wide association study identified a single-nucleotide polymorphism (SNP) signal across the glutamate-rich 3 (ERICH3) gene that was nearly genome-wide significantly associated with plasma serotonin (5-HT) concentrations, which were themselves associated with SSRI response for MDD patients enrolled in the Mayo Clinic PGRN-AMPS SSRI trial. In this study, we performed a meta-analysis which demonstrated that those SNPs were significantly associated with SSRI treatment outcomes in four independent MDD trials. However, the function of ERICH3 and molecular mechanism(s) by which it might be associated with plasma 5-HT concentrations and SSRI clinical response remained unclear. Therefore, we characterized the human ERICH3 gene functionally and identified ERICH3 mRNA transcripts and protein isoforms that are highly expressed in central nervous system cells. Coimmunoprecipitation identified a series of ERICH3 interacting proteins including clathrin heavy chain which are known to play a role in vesicular function. Immunofluorescence showed ERICH3 colocalization with 5-HT in vesicle-like structures, and ERICH3 knock-out dramatically decreased 5-HT staining in SK-N-SH cells as well as 5-HT concentrations in the culture media and cell lysates without changing the expression of 5-HT synthesizing or metabolizing enzymes. Finally, immunofluorescence also showed ERICH3 colocalization with dopamine in human iPSC-derived neurons. These results suggest that ERICH3 may play a significant role in vesicular function in serotonergic and other neuronal cell types, which might help explain its association with antidepressant treatment response.

Expression of the Neuroblastoma-Associated ALK-F1174L Activating Mutation During Embryogenesis Impairs the Differentiation of Neural Crest Progenitors in Sympathetic Ganglia

Neuroblastoma (NB) is an embryonal malignancy derived from the abnormal differentiation of the sympathetic nervous system. The Anaplastic Lymphoma Kinase (ALK) gene is frequently altered in NB, through copy number alterations and activating mutations, and represents a predisposition in NB-genesis when mutated. Our previously published data suggested that ALK activating mutations may impair the differentiation potential of neural crest (NC) progenitor cells. Here, we demonstrated that the expression of the endogenous ALK gene starts at E10.5 in the developing sympathetic ganglia (SG). To decipher the impact of deregulated ALK signaling during embryogenesis on the formation and differentiation of sympathetic neuroblasts, Sox10-Cre;LSL-ALK-F1174L embryos were produced to restrict the expression of the human ALK-F1174L transgene to migrating NC cells (NCCs). First, ALK-F1174L mediated an embryonic lethality at mid-gestation and an enlargement of SG with a disorganized architecture in Sox10-Cre;LSL-ALK-F1174L embryos at E10.5 and E11.5. Second, early sympathetic differentiation was severely impaired in Sox10-Cre;LSL-ALK-F1174L embryos. Indeed, their SG displayed a marked increase in the proportion of NCCs and a decrease of sympathetic neuroblasts at both embryonic stages. Third, neuronal and noradrenergic differentiations were blocked in Sox10-Cre;LSL-ALK-F1174L SG, as a reduced proportion of Phox2b⁺ sympathoblasts expressed βIII-tubulin and almost none were Tyrosine Hydroxylase (TH) positive. Finally, at E10.5, ALK-F1174L mediated an important increase in the proliferation of Phox2b⁺ progenitors, affecting the transient cell cycle exit observed in normal SG at this embryonic stage. Altogether, we report for the first time that the expression of the human ALK-F1174L mutation in NCCs during embryonic development profoundly disturbs early sympathetic progenitor differentiation, in addition to increasing their proliferation, both mechanisms being potential crucial events in NB oncogenesis.

Development of tau-directed small molecule modulators for Alzheimer's disease: a recent patent review (2014-2018)

Alzheimer's disease (AD) is a progressive neurodegenerative disease that is characterized by memory loss and cognitive impairment. As this disease is becoming a serious global health issue, development of disease modifying therapeutics is urgently required. AD is characterized by deposits of two protein, amyloid β and tau. Although amyloid β-based therapeutics have been extensively investigated so far, tau has also received great attention as one of promising molecular targets for AD. In this review, a variety of tau-directed strategies to rescue tau-mediated neurotoxicity will be reviewed especially focusing on small molecules. Subsequently, recent patents published from 2014 to 2018 that integrate efforts to develop tau-directed small molecules for the treatment of AD will be reviewed.

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.

Identification and biological evaluation of glycol diaryl ethers as novel anti-cancer agents through structure-based optimization of crizotinib

Crizotinib, a drug for anaplastic lymphoma kinase (ALK) positive and c-ros oncogene 1 receptor tyrosine kinase (ROS1) positive non-small cell lung cancer (NSCLC), was structurally optimized via a strategy of structure-based fragment replacing. Computational study showed it was beneficial for interaction of crizotinib and ALK to increase the distance between pyridyl ring and phenyl ring in crizotinib, and thus, a series of novel glycol diaryl ethers were synthesized. The in vitro anti-tumor activity of synthesized compounds was studied in NSCLC cell line H2228 and neurobalstoma cell line SH-SY5Y. Among the synthesized compounds, 9e exhibits stronger anti-cancer activity than crizotinib toward H2228 cell line with an IC₅₀ value of 0.22 μM. Molecular docking indicated that a longer chain between pyridyl ring and phenyl ring enabled molecule to have new interaction with a neighboring small hydrophobic pocket.

ALK in Neuroblastoma: Biological and Therapeutic Implications

Neuroblastoma (NB) is the most common and deadly solid tumour in children. Despite the development of new treatment options for high-risk NB, over half of patients relapse and five-year survival remains at 40-50%. Therefore, novel treatment strategies aimed at providing long-term disease remission are urgently sought. ALK, encoding the anaplastic lymphoma kinase receptor, is altered by gain-of-function point mutations in around 14% of high-risk NB and represents an ideal therapeutic target given its low or absent expression in healthy tissue postnatally. Small-molecule inhibitors of Anaplastic Lymphoma Kinase (ALK) approved in ALK fusion-positive lung cancer are currently undergoing clinical assessment in patients with ALK-mutant NB. Parallel pre-clinical studies are demonstrating the efficacy of ALK inhibitors against common ALK variants in NB; however, a complex picture of therapeutic resistance is emerging. It is anticipated that long-term use of these compounds will require combinatorial targeting of pathways downstream of ALK, functionally-related 'bypass' mechanisms and concomitant oncogenic pathways.

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.

Proliferation and Survival of Embryonic Sympathetic Neuroblasts by MYCN and Activated ALK Signaling

Neuroblastoma (NB) is a childhood tumor that arises from the sympathoadrenal lineage. MYCN amplification is the most reliable marker for poor prognosis and MYCN overexpression in embryonic mouse sympathetic ganglia results in NB-like tumors. MYCN cooperates with mutational activation of anaplastic lymphoma kinase (ALK), which promotes progression to NB, but the role of MYCN and ALK in tumorigenesis is still poorly understood. Here, we use chick sympathetic neuroblasts to examine the normal function of MYCN and MYC in the control of neuroblast proliferation, as well as effects of overexpression of MYCN, MYC, and activated ALK, alone and in combination. We demonstrate that MYC is more strongly expressed than MYCN during neurogenesis and is important for in vitro neuroblast proliferation. MYC and MYCN overexpression elicits increased proliferation but does not sustain neuroblast survival. Unexpectedly, long-term expression of activated ALK^F1174L leads to cell-cycle arrest and promotes differentiation and survival of postmitotic neurons. ALK^F1174L induces NEFM, RET, and VACHT and results in decreased expression of proapototic (BMF, BIM), adrenergic (TH), and cell-cycle genes (e.g., CDC25A, CDK1). In contrast, neuroblast proliferation is maintained when MYCN and ALK^F1174L are coexpressed. Proliferating MYCN/ALK^F1174L neuroblasts display a differentiated phenotype but differ from ALK-expressing neurons by the upregulation of SKP2, CCNA2, E2F8, and DKC1 Inhibition of the ubiquitin ligase SKP2 (S-phase kinase-associated protein 2), which targets the CDK inhibitor p27 for degradation, reduces neuroblast proliferation, implicating SKP2 in the maintained proliferation of MYCN/ALK^F1174L neuroblasts. Together, our results characterize MYCN/ALK cooperation leading to neuroblast proliferation and survival that may represent initial steps toward NB development.

SIGNIFICANCE STATEMENT

MYCN overexpression combined with activated anaplastic lymphoma kinase (ALK) is sufficient to induce neuroblastoma (NB) in mouse sympathoadrenal cells. To address cellular and molecular effects elicited by MYCN/ALK cooperation, we used cultures of chick sympathetic neuroblasts. We demonstrate that MYCN increases proliferation but not survival, whereas long-term expression of ALK^F1174L elicits cell-cycle exit, differentiation, and survival of postmitotic neurons. Combined MYCN/ALK^F1174L expression allows long-term proliferation and survival of neuroblasts with differentiated characteristics. In the presence of ALK^F1174L signaling, MYCN induces the expression of the ubiquitin ligase SKP2 (S-phase kinase-associated protein 2), which targets p27 for degradation and is also upregulated in high-risk NB. SKP2 inhibition supports a function for SKP2 in the maintained neuroblast proliferation downstream of MYCN/ALK, which may represent an early step toward tumorigenesis.

Functional role of ALK-related signal cascades on modulation of epithelial-mesenchymal transition and apoptosis in uterine carcinosarcoma

BACKGROUND

Anaplastic lymphoma kinase (ALK), which is a receptor tyrosine kinase, is essentially and transiently expressed in the developing nervous system. Recently, the deregulated expression of full-length ALK has been observed in some primary solid tumors, but little is known about its involvement in the tumorigenesis of uterine carcinosarcomas (UCSs). Here we examined the functional role of the ALK gene in UCSs.

METHODS

Regulation and function of the ALK gene were assessed using two endometrial carcinoma cell lines. Expression of ALK and its related molecules were also investigated using clinical samples of UCSs.

RESULTS

In cell lines, ALK promoter activity was significantly increased by transfection of Sox11 and N-myc, which are known to contribute to neuronal properties. Cells stably overexpressing full-length ALK showed an enhancement of EMT properties mediated by TGF-β1 and HGF, along with an increase in phosphorylated (p) Akt and nuclear p65. Overexpression of p65 also led to transactivation of Twist1 gene, known as an EMT inducer. Finally, treatment of the stable ALK-overexpressing cells with doxorubicin resulted in inhibition of apoptosis with progressive increase in the expression ratio of both pAkt and bcl2 relative to total Akt and bax, respectively. In clinical samples, strong cytoplasmic ALK immunoreactivity and mRNA signals without rearrangement or amplification of the ALK locus were frequently observed in UCSs, particularly in the sarcomatous components. Further, ALK IHC score was found to be positively correlated with Sox11, N-myc, Twist1, and bcl2 scores.

CONCLUSION

ALK-related signal cascades containing Akt, NF-κB, Twist1, and bcl2 may participate in initial signaling for divergent sarcomatous differentiation driven from carcinomatous components in UCSs through induction of the EMT process and inhibition of apoptotic features.

Exploring Missense Mutations in Tyrosine Kinases Implicated with Neurodegeneration

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

Ethanol activates midkine and anaplastic lymphoma kinase signaling in neuroblastoma cells and in the brain

Alcohol engages signaling pathways in the brain. Midkine (MDK) is a neurotrophic factor that is over-expressed in the prefrontal cortex of alcoholics. MDK and one of its receptors, anaplastic lymphoma kinase (ALK), also regulate behavioral responses to ethanol in mice. The goal of this study was to determine whether MDK and ALK expression and signaling are activated by ethanol. We found that ethanol treatment of neuroblastoma cells increased MDK and ALK expression. We also assessed activation of ALK by ethanol in cells and found that ALK and ALK-dependent extracellular signal-regulated kinase (ERK) and signal transducer and activator of transcription 3 (STAT3) phosphorylation increased rapidly with ethanol exposure. Similarly, treatment of cells with recombinant MDK protein increased ALK, ERK and STAT3 phosphorylation, suggesting that ethanol may utilize MDK to activate ALK signaling. In support of this, transfection of cells with MDK siRNAs attenuated ALK signaling in response to ethanol. Ethanol also activates ERK signaling in the brain. We found that inhibition of ALK or knockout of MDK attenuated ethanol-induced ERK phosphorylation in mouse amygdala. These results demonstrate that ethanol engages MDK and ALK signaling, which has important consequences for alcohol-induced neurotoxicity and the regulation of behaviors related to alcohol abuse.

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.

Anaplastic lymphoma kinase: "Ligand Independent Activation" mediated by the PTN/RPTPβ/ζ signaling pathway

Anaplastic lymphoma kinase is essential in early development, differentiation, and maintenance of cell survival; nevertheless, the mechanism to activate ALK has remained elusive. ALK has remained an "Orphan Receptor." The studies cited below describe a unique mechanism termed "Ligand Independent Activation." It is shown that activation of ALK results when the cytokine pleiotrophin (PTN) interacts with its receptor, the receptor protein tyrosine phosphatase β/ζ (RPTPβ/ζ). Pleiotrophin inactivates the catalytic activity of RPTPβ/ζ, which, when not inactivated, dephosphorylates phosphotyrosine sites in the activation domain of ALK; as a consequence of the inactivation of RPTPβ/ζ by PTN, autophosphorylation and autoactivation of ALK rapidly follow. The PTN/RPTPβ/ζ signaling pathway thus regulates the catalytic activity of ALK and tyrosine phosphorylation levels of ALK downstream target proteins. Furthermore, since ALK is only one of the key ALK phosphoproteins targeted by the PTN/RPTPβ/ζ signaling pathway, the PTN/RPTPβ/ζ signaling pathway has the potential to coordinately regulate tyrosine phosphorylation of other different key proteins in multiple cellular compartments. This article is part of a Special Issue entitled: Emerging recognition and activation mechanisms of receptor tyrosine kinases.

Mechanism for the induction of cell death in ONS-76 medulloblastoma cells by Zhangfei/CREB-ZF

Cells from medulloblastoma lines do not contain detectable amounts of the basic leucine-zipper protein Zhangfei. However, we have previously shown that expression of this protein in cells of the ONS-76 and UW228 medulloblastoma lines causes the cells to stop growing and develop processes that resemble neurites. Our objective was to determine the molecular mechanisms by which Zhangfei influences ONS-76 cells. We infected ONS-76 cells with adenovirus vectors expressing either Zhangfei or the control protein LacZ and then compared the following parameters in Zhangfei and LacZ-expressing cells: (a) markers of apoptosis, autophagy and macropinocytosis, (b) transcripts for genes involved in neurogenesis and apoptosis, (c) phosphorylation of peptide targets of selected cellular protein kinases, and (d) activation of transcription factors. Zhangfei-expressing cells appeared to succumb to apoptosis. Increased staining for autophagic vesicles and upregulated expression of autophagy response genes in these cells indicated that they were undergoing autophagy, possibly associated with apoptosis. Within our analysis, patterns of gene expression and phosphorylation-mediated signal transduction activity in Zhangfei-expressing cells indicated that the mitogen-activated protein kinase (MAPK) pathway was active. In addition, we found that the transcription factor Brn3a as well as factors implicated in differentiation were also active in Zhangfei-expressing cells. We tested the hypothesis that Zhangfei enhances the expression of Brn3a, a known inducer of TrkA, the high-affinity receptor for nerve growth factor (NGF). TrkA then engages NGF in an autocrine manner triggering the MAPK pathway and leading to differentiation of ONS-76 cells into neuron and glia-like cells-a process that eventually brings about cell death. We showed that: (a) Zhangfei could enhance transcription from the isolated Brn3a promoter, (b) ONS-76 cells produced NGF and (c) antibodies against NGF and inhibitors of TrkA and selected components of the MAPK pathway could partially restore the growth of Zhangfei-expressing ONS-76 cells.

Emerging importance of ALK in neuroblastoma

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

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

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

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

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

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

Identification of novel prognostic markers in relapsing localized resectable neuroblastoma

Patients with localized resectable neuroblastoma (NB) generally have an excellent prognosis and can be treated by surgery alone, but approximately 10% of them develop local recurrences or metastatic progression. The known predictive risk factors are important for the identification of localized resectable NB patients at risk of relapse and/or progression, who may benefit from early and aggressive treatment. These factors, however, identify only a subset of patients at risk, and the search for novel prognostic markers is warranted. This review focuses on the recent advances in the identification of new prognostic markers. Recently we addressed the search of novel genetic prognostic markers in a selected cohort of patients with stroma-poor localized resectable NB who underwent disease relapse or progression (group 1) or complete remission (group 2). High-resolution array-comparative genomic hybridization (CGH) DNA copy-number analysis technology was used. Chromosome 1p36.22p36.32 loss and 1q22qter gain, detected almost exclusively in group 1 patients, were significantly associated with poor event-free survival (EFS). Increasing evidence points to anaplastic lymphoma kinase (ALK) as a fundamental oncogene associated with NB. The immunohistochemical analysis of sporadic NB localized resectable primary tumors (stage 1-2) showed a correlation between aberrant ALK level of expression and tumor progression and clinical outcome. Moreover, other factors that might influence the clinical behavior of these tumors will be reviewed.

Anaplastic lymphoma kinase activates the small GTPase Rap1 via the Rap1-specific GEF C3G in both neuroblastoma and PC12 cells

Many different types of cancer originate from aberrant signaling from the anaplastic lymphoma kinase (ALK) receptor tyrosine kinase (RTK), arising through different translocation events and overexpression. Further, activating point mutations in the ALK domain have been recently reported in neuroblastoma. To characterize signaling in the context of the full-length receptor, we have examined whether ALK is able to activate Rap1 and contribute to differentiation/proliferation processes. We show that ALK activates Rap1 via the Rap1-specific guanine-nucleotide exchange factor C3G, which binds in a constitutive complex with CrkL to activated ALK. The activation of the C3G/Rap1 pathway results in neurite outgrowth of PC12 cells, which is inhibited by either overexpression of Rap1GAP or siRNA-mediated knockdown of Rap1 itself or the guanine nucleotide exchange factor C3G. Significantly, this pathway also appears to function in the regulation of proliferation of neuroblastoma cells such as SK-N-SH and SH-SY5Y, because abrogation of Rap1 activity by Rap1-specific siRNA or overexpression of Rap1GAP reduces cellular growth. These results suggest that ALK activation of Rap1 may contribute to cell proliferation and oncogenesis of neuroblastoma driven by gain-of-function mutant ALK receptors.

Mutation-independent anaplastic lymphoma kinase overexpression in poor prognosis neuroblastoma patients

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase predominantly expressed in the developing nervous system. Recently, mutated ALK has been identified as a major oncogene associated with familial and sporadic neuroblastomas (NBL). Yet, a direct correlation between endogenous expression level of the ALK protein, oncogenic potential, and clinical outcome has not been established. We investigated ALK genetic mutations, protein expression/phosphorylation, and functional inhibition both in NBL-derived cell lines and in 34 localized and 48 advanced/metastatic NBL patients. ALK constitutive phosphorylation/activation was observed in high-ALK expressing cells, harboring either a mutated or a wild-type receptor. No activation was found in cell lines with low expression of wild-type ALK. After 72 hours of treatments, small molecule ALK inhibitor CEP-14083 (60 nmol/L) induced growth arrest and cell death in NBL cells overexpressing wild-type (viability: ALK(high) 12.8%, ALK(low) 73%, P = 0.0035; cell death: ALK(high) 56.4%, ALK(low) 16.2%, P = 0.0001) or mutated ALK. ALK protein expression was significantly up-regulated in advanced/metastatic compared with localized NBLs (ALK overexpressing patients: stage 1-2, 23.5%; stage 3-4, 77%; P < 0.0001). Interestingly, protein levels did not always correlate with ALK genetic alterations and/or mRNA abundance. Both mutated and wild-type ALK receptor can exert oncogenic activity in NBL cells. However, wild-type ALK receptor requires a critical threshold of expression to achieve oncogenic activation. Overexpression of either mutated or wild-type ALK defines poor prognosis patients. Alternative mechanisms other than direct mutations and/or gene amplification regulate the ALK level of expression in NBL cells. Wild-type ALK is a potential therapeutic target for advanced/metastatic NBLs.

ALK (Anaplastic Lymphoma Kinase) expression in DRG neurons and its involvement in neuron-Schwann cells interaction

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase (RTK) transiently expressed in specific regions of the central and peripheral nervous systems. In this study, we focused on the rat developing dorsal root ganglion (DRG). This ganglion is composed of heterogeneous sensory neurons characterized by the expression of RTK for neurotrophic factors, such as the nerve growth factor receptor TrkA or the glial-derived neurotrophic factor family receptor Ret, which are specifically detected in nociceptive neurons. In DRG, ALK expression reached a maximum around birth. We showed that ALK is specifically present in a subtype of neurons during DRG development, and that the majority of these neurons co-expressed TrkA and Ret. Interestingly, we identified only one form (220 kDa) of ALK in DRG neurons both in vivo and in vitro. On the opposite, in transfected cells as well as in brain extracts, ALK was identified as two forms (220 and 140 kDa). The DRG is composed of neurons and glial cells, principally satellite Schwann cells. Thus, we hypothesized that the presence of satellite Schwann cells was involved in the absence of truncated ALK. Using two different cell types, HEK293 cells stably expressing ALK, and MSC80 cells, a previously described Schwann cell line, we showed that a factor secreted by the Schwann cells is likely involved in the absence of ALK cleavage. All these data hence open new perspectives concerning the role of ALK in the specification of nociceptive DRG neurons and in the neurons-Schwann cells interaction.

Anaplastic lymphoma kinase: signalling in development and disease

RTKs (receptor tyrosine kinases) play important roles in cellular proliferation and differentiation. In addition, RTKs reveal oncogenic potential when their kinase activities are constitutively enhanced by point mutation, amplification or rearrangement of the corresponding genes. The ALK (anaplastic lymphoma kinase) RTK was originally identified as a member of the insulin receptor subfamily of RTKs that acquires transforming capability when truncated and fused to NPM (nucleophosmin) in the t(2;5) chromosomal rearrangement associated with ALCL (anaplastic large cell lymphoma). To date, many chromosomal rearrangements leading to enhanced ALK activity have been described and are implicated in a number of cancer types. Recent reports of the EML4 (echinoderm microtubule-associated protein like 4)–ALK oncoprotein in NSCLC (non-small cell lung cancer), together with the identification of activating point mutations in neuroblastoma, have highlighted ALK as a significant player and target for drug development in cancer. In the present review we address the role of ALK in development and disease and discuss implications for the future.

The ethanol response gene Cab45 can modulate the impairment elicited by ethanol and ultraviolet in PC12 cells

High consumption of ethanolic beverages facilitates neurodegeneration, but the mechanism of this process still remained elusive. Suppression subtractive hybridization (SSH) is a technique for detection of rare transcripts. With SSH approach, we identified one ethanol response gene Cab45, which was down-regulated by ethanol with time-dependent manner in B104 cells. The full-length sequence of Cab45 gene was obtained by 5' -RACE (5' Rapid Amplification of cDNA Ends) for the first time in rat. Based on the sequence of deduced amino acid of rat Cab45, the alignment was conducted with its counterparts in different species and displayed a high conservation. Using different tissues in rat and cell lines, Cab45 was characterized by a ubiquitous expression and differentiation dependent down-regulation. Given that ethanol facilitates some cell differentiation, we hypothesize that Cab45 is involved in ethanol-mediated differentiation. With transient transfection, the function of Cab45 was investigated by up-regulation and down-regulation in PC12 cells. Ethanol treatment and UV exposure were conducted subsequently and cell proliferations were detected by MTT (Methyl Thiazolyl Tetrazolium) approach. It revealed that the up-regulation of Cab45 modulated the impairment elicited by ethanol and UV in transfected cells. As a member of new calcium binding protein family, the exact role of Cab45 still remains unclear.

ALK activation induces Shc and FRS2 recruitment: Signaling and phenotypic outcomes in PC12 cells differentiation

Activation of the neuronal receptor tyrosine kinase ALK (anaplastic lymphoma kinase) promoted the neuron-like differentiation of PC12 cells through specific activation of the ERK MAP-kinase pathway. However, the nature of primary signaling events initiated is still poorly documented. Here, we established that Shc and FRS2 adaptors were recruited and phosphorylated following antibody-based ALK activation. We further demonstrated that Shc was recruited to the consensus phosphotyrosine site NPTpY(1507) and FRS2 was likely recruited to a novel non-orthodox phosphotyrosine site within ALK. Finally, we characterized a functional role for Shc and likely FRS2 in ALK-dependant MAP-kinase activation and neuronal differentiation of PC12 cells. These findings hence open attractive perspectives concerning specific characteristics of ALK in the control of the mechanisms driving neuronal differentiation.