Anaplastic lymphoma kinase is activated through the pleiotrophin/receptor protein-tyrosine phosphatase beta/zeta signaling pathway: an alternative mechanism of receptor tyrosine kinase activation

Olanzapine Modulate Lipid Metabolism and Adipose Tissue Accumulation via Hepatic Muscarinic M3 Receptor-Mediated Alk-Related Signaling

Olanzapine is an atypical antipsychotic drug and a potent muscarinic M3 receptor (M3R) antagonist. Olanzapine has been reported to cause metabolic disorders, including dyslipidemia. Anaplastic lymphoma kinase (Alk), a tyrosine kinase receptor well known in the pathogenesis of cancer, has been recently identified as a key gene in the regulation of thinness via the regulation of adipose tissue lipolysis. This project aimed to investigate whether Olanzapine could modulate the hepatic Alk pathway and lipid metabolism via M3R. Female rats were treated with Olanzapine and/or Cevimeline (an M3R agonist) for 9 weeks. Lipid metabolism and hepatic Alk signaling were analyzed. Nine weeks' treatment of Olanzapine caused metabolic disturbance including increased body mass index (BMI), fat mass accumulation, and abnormal lipid metabolism. Olanzapine treatment also led to an upregulation of Chrm3, Alk, and its regulator Ptprz1, and a downregulation of Lmo4, a transcriptional repressor of Alk in the liver. Moreover, there were positive correlations between Alk and Chrm3, Alk and Ptprz1, and a negative correlation between Alk and Lmo4. However, cotreatment with Cevimeline significantly reversed the lipid metabolic disturbance and adipose tissue accumulation, as well as the upregulation of the hepatic Alk signaling caused by Olanzapine. This study demonstrates evidence that Olanzapine may cause metabolic disturbance by modulating hepatic Alk signaling via M3R, which provides novel insight for modulating the hepatic Alk signaling and potential interventions for targeting metabolic disorders.

Novel RPTPγ and RPTPζ splice variants from mixed neuron-astrocyte hippocampal cultures as well as from the hippocampi of newborn and adult mice

Receptor protein tyrosine phosphatases γ and ζ (RPTPγ and RPTPζ) are transmembrane signaling proteins with extracellular carbonic anhydrase-like domains that play vital roles in the development and functioning of the central nervous system (CNS) and are implicated in tumor suppression, neurodegeneration, and sensing of extracellular [CO2] and [HCO3 -]. RPTPγ expresses throughout the body, whereas RPTPζ preferentially expresses in the CNS. Here, we investigate differential RPTPγ-RPTPζ expression in three sources derived from a wild-type laboratory strain of C57BL/6 mice: (a) mixed neuron-astrocyte hippocampal (HC) cultures 14 days post isolation from P0-P2 pups; (b) P0-P2 pup hippocampi; and (c) 9- to 12-week-old adult hippocampi. Regarding RPTPγ, we detect the Ptprg variant-1 (V1) transcript, representing canonical exons 1-30. Moreover, we newly validate the hypothetical assembly [XM_006517956] (propose name, Ptprg-V3), which lacks exon 14. Both transcripts are in all three HC sources. Regarding RPTPζ, we confirm the expression of Ptprz1-V1, detecting it in pups and adults but not in cultures, and Ptprz1-V3 through Ptprz1-V7 in all three preparations. We newly validate hypothetical assemblies Ptprz1-X1 (in cultures and pups), Ptprz1-X2 (in all three), and Ptprz1-X5 (in pups and adults) and propose to re-designate them as Ptprz1-V0, Ptprz1-V2, and Ptprz1-V8, respectively. The diversity of RPTPγ and RPTPζ splice variants likely corresponds to distinct signaling functions, in different cellular compartments, during development vs later life. In contrast to previous studies that report divergent RPTPγ and RPTPζ protein expressions in neurons and sometimes in the glia, we observe that RPTPγ and RPTPζ co-express in the somata and processes of almost all HC neurons but not in astrocytes, in all three HC preparations.

Anaplastic Lymphoma Kinase (ALK) in Posterior Cranial Fossa Tumors: A Scoping Review of Diagnostic, Prognostic, and Therapeutic Perspectives

Anaplastic Lymphoma Kinase (ALK) has been implicated in several human cancers. This review aims at mapping the available literature on the involvement of ALK in non-glial tumors localized in the posterior cranial fossa and at identifying diagnostic, prognostic, and therapeutic considerations. Following the PRISMA-ScR guidelines, studies were included if they investigated ALK's role in primary CNS, non-glial tumors located in the posterior cranial fossa. A total of 210 manuscripts were selected for full-text review and 16 finally met the inclusion criteria. The review included 55 cases of primary, intracranial neoplasms with ALK genetic alterations and/or protein expression, located in the posterior fossa, comprising of medulloblastoma, anaplastic large-cell lymphoma, histiocytosis, inflammatory myofibroblastic tumors, and intracranial myxoid mesenchymal tumors. ALK pathology was investigated via immunohistochemistry or genetic analysis. Several studies provided evidence for potential diagnostic and prognostic value for ALK assessment as well as therapeutic efficacy in its targeting. The available findings on ALK in posterior fossa tumors are limited. Nevertheless, previous findings suggest that ALK assessment is of diagnostic and prognostic value in medulloblastoma (WNT-activated). Interestingly, a substantial proportion of ALK-positive/altered CNS histiocytoses thus far identified have been localized in the posterior fossa. The therapeutic potential of ALK inhibition in histiocytosis warrants further investigation.

Protein Tyrosine Phosphatase Receptor Zeta 1 as a Potential Target in Cancer Therapy and Diagnosis

Protein tyrosine phosphatase receptor zeta 1 (PTPRZ1) is a type V transmembrane tyrosine phosphatase that is highly expressed during embryonic development, while its expression during adulthood is limited. PTPRZ1 is highly detected in the central nervous system, affecting oligodendrocytes' survival and maturation. In gliomas, PTPRZ1 expression is significantly upregulated and is being studied as a potential cancer driver and as a target for therapy. PTPRZ1 expression is also increased in other cancer types, but there are no data on the potential functional significance of this finding. On the other hand, low PTPRZ1 expression seems to be related to a worse prognosis in some cancer types, suggesting that in some cases, it may act as a tumor-suppressor gene. These discrepancies may be due to our limited understanding of PTPRZ1 signaling and tumor microenvironments. In this review, we present evidence on the role of PTPRZ1 in angiogenesis and cancer and discuss the phenomenal differences among the different types of cancer, depending on the regulation of its tyrosine phosphatase activity or ligand binding. Clarifying the involved signaling pathways will lead to its efficient exploitation as a novel therapeutic target or as a biomarker, and the development of proper therapeutic approaches.

PROTAC'ing oncoproteins: targeted protein degradation for cancer therapy

Molecularly targeted cancer therapies substantially improve patient outcomes, although the durability of their effectiveness can be limited. Resistance to these therapies is often related to adaptive changes in the target oncoprotein which reduce binding affinity. The arsenal of targeted cancer therapies, moreover, lacks coverage of several notorious oncoproteins with challenging features for inhibitor development. Degraders are a relatively new therapeutic modality which deplete the target protein by hijacking the cellular protein destruction machinery. Degraders offer several advantages for cancer therapy including resiliency to acquired mutations in the target protein, enhanced selectivity, lower dosing requirements, and the potential to abrogate oncogenic transcription factors and scaffolding proteins. Herein, we review the development of proteolysis targeting chimeras (PROTACs) for selected cancer therapy targets and their reported biological activities. The medicinal chemistry of PROTAC design has been a challenging area of active research, but the recent advances in the field will usher in an era of rational degrader design.

The Tyrosine Phosphatase hPTPRβ Controls the Early Signals and Dopaminergic Cells Viability via the P2X7 Receptor

ATP, one of the signaling molecules most commonly secreted in the nervous system and capable of stimulating multiple pathways, binds to the ionotropic purinergic receptors, in particular, the P2X₇ receptor (P2X₇R) and stimulates neuronal cell death. Given this effect of purinergic receptors on the viability of dopaminergic neurons model cells and that Ras GTPases control Erk1/2-regulated mitogen-activated cell proliferation and survival, we have investigated the role of the small GTPases of the Ras superfamily, together with their regulatory and effector molecules as the potential molecular intermediates in the P2X₇R-regulated cell death of SN4741 dopaminergic neurons model cells. Here, we demonstrate that the neuronal response to purinergic stimulation involves the Calmodulin/RasGRF1 activation of the small GTPase Ras and Erk1/2. We also demonstrate that tyrosine phosphatase PTPRβ and other tyrosine phosphatases regulate the small GTPase activation pathway and neuronal viability. Our work expands the knowledge on the intracellular responses of dopaminergic cells by identifying new participating molecules and signaling pathways. In this sense, the study of the molecular circuitry of these neurons is key to understanding the functional effects of ATP, as well as considering the importance of these cells in Parkinson’s Disease.

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

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

Genetic inactivation of midkine, not pleiotrophin, facilitates extinction of alcohol-induced conditioned place preference

Pleiotrophin (PTN) and midkine (MK) are growth factors that modulate alcohol consumption and reward. Since both PTN and MK limit the rewarding effects of alcohol, pharmacological potentiation of the PTN and MK signaling pathways has been proposed for the treatment of alcohol use disorders (AUD). Although the use of this therapy in the prevention of alcohol relapse is important, the potential role of these cytokines in extinguishing alcohol-induced seeking behavior is a key question that remains unanswered. To fill this gap, we have now studied the extinction of the conditioned place preference (CPP) induced by different doses of alcohol in Ptn knockout (Ptn^-/-) and Mk knockout (Mk^-/-) mice. The data confirm a higher sensitivity of Ptn^-/- mice to the conditioning effects of a low dose (1 g/kg) and a rewarding dose (2 g/kg) of alcohol, while Mk^-/- mice are only more susceptible to the conditioning effects of the low dose of this drug. More importantly, the percentage of Mk^-/- mice, not Ptn^-/- mice, that efficiently extinguished alcohol-induced CPP was significantly higher than that of Wt mice. Taken together, the data presented here confirm that Ptn and Mk are genetic factors that determine the conditioning effects of alcohol in mice and that Mk is a novel factor that plays an important role in the extinction of alcohol-induced CPP.

Role of Receptor Protein Tyrosine Phosphatase β/ζ in Neuron-Microglia Communication in a Cellular Model of Parkinson's Disease

Pleiotrophin (PTN) is a neurotrophic factor that regulates glial responses in animal models of different types of central nervous system (CNS) injuries. PTN is upregulated in the brain in different pathologies characterized by exacerbated neuroinflammation, including Parkinson’s disease. PTN is an endogenous inhibitor of Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ, which is abundantly expressed in the CNS. Using a specific inhibitor of RPTPβ/ζ (MY10), we aimed to assess whether the PTN/RPTPβ/ζ axis is involved in neuronal and glial injury induced by the toxin MPP+. Treatment with the RPTPβ/ζ inhibitor MY10 alone decreased the viability of both SH-SY5Y neuroblastoma cells and BV2 microglial cultures, suggesting that normal RPTPβ/ζ function is involved in neuronal and microglial viability. We observed that PTN partially decreased the cytotoxicity induced by MPP+ in SH-SY5Y cells underpinning the neuroprotective function of PTN. However, MY10 did not seem to modulate the SH-SY5Y cell loss induced by MPP+. Interestingly, we observed that media from SH-SY5Y cells treated with MPP+ and MY10 decreases microglial viability but may elicit a neuroprotective response of microglia by upregulating Ptn expression. The data suggest a neurotrophic role of microglia in response to neuronal injury through upregulation of Ptn levels.

Role of RPTPβ/ζ in neuroinflammation and microglia-neuron communication

Pleiotrophin (PTN) is a cytokine that is upregulated in different neuroinflammatory disorders. Using mice with transgenic PTN overexpression in the brain (Ptn-Tg), we have found a positive correlation between iNos and Tnfα mRNA and Ptn mRNA levels in the prefrontal cortex (PFC) of LPS-treated mice. PTN is an inhibitor of Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ, which is mainly expressed in the central nervous system. We aimed to test if RPTPβ/ζ is involved in the modulation of neuroinflammatory responses using specific inhibitors of RPTPβ/ζ (MY10 and MY33-3). Treatment with MY10 potentiated LPS-induced microglial responses in the mouse PFC. Surprisingly, MY10 caused a decrease in LPS-induced NF-κB p65 expression, suggesting that RPTPβ/ζ may be involved in a novel mechanism of potentiation of microglial activation independent of the NF-κB p65 pathway. MY33-3 and MY10 limited LPS-induced nitrites production and iNos increases in BV2 microglial cells. SH-SY5Y neuronal cells were treated with the conditioned media from MY10/LPS-treated BV2 cells. Conditioned media from non-stimulated and from LPS-stimulated BV2 cells increased the viability of SH-SY5Y cultures. RPTPβ/ζ inhibition in microglial cells disrupted this neurotrophic effect of microglia, suggesting that RPTPβ/ζ plays a role in the neurotrophic phenotype of microglia and in microglia-neuron communication.

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.

PTN-PTPRZ signalling is involved in deer antler stem cell regulation during tissue regeneration

A growing deer antler contains a stem cell niche that can drive endochondral bone regeneration at up to 2 cm/day. Pleiotrophin (PTN), as a multifunctional growth factor, is found highly expressed at the messenger RNA level within the active antler stem cell tissues. This study aims to map the expression patterns of PTN protein and its receptors in a growing antler and investigate the effects of PTN on antler stem cells in vitro. Immunohistochemistry was employed to localise PTN/midkine (MDK) and their functional receptors, protein tyrosine phosphatase receptor type Z (PTPRZ), anaplastic lymphoma kinase (ALK), NOTCH2, and integrin α_V β_3, on serial slides of the antler growth centre. PTN was found to be the dominantly expressed growth factor in the PTN/MDK family. High expression of PTPRZ and ALK co-localised with PTN was found suggesting a potential interaction. The high levels of PTN and PTPRZ reflected the antler stem cell activation status during the regenerative process. When antler stem cells were cultured in vitro under the normoxic condition, no PTN protein was detected and exogenous PTN did not induce differentiation or proliferation but rather stem cell maintenance. Collectively, the antler stem cell niche appears to upregulate PTN and PTPRZ in vivo, and PTN-PTPRZ signalling may be involved in regulating antler stem cell behaviour during rapid antler regeneration.

Association of an anaplastic lymphoma kinase pathway signature with cell de-differentiation, neoadjuvant chemotherapy response, and recurrence risk in breast cancer

Background

Aberrant activation of anaplastic lymphoma kinase (ALK) signaling has been found to be involved in the tumorigenesis of multiple types of cancer. The aim of this study was to determine the role of this pathway in the pathogenesis of breast cancer.

Methods

An ALK pathway signature that we generated previously was used to compute the ALK pathway activity in 6381 breast cancer samples from 42 microarray datasets, and the associations between ALK pathway signature score and clinical variables were examined using logistic regression and survival analyses.

Results

Our results indicated that high ALK pathway activity was a significant risk factor for hormone receptor‐negative, high‐grade breast cancer in the 42 datasets. ALK pathway activity was positively associated with pathological complete response (pCR) in 15 datasets annotated with patient's neoadjuvant chemotherapy response information (overall odds ratio = 1.67, P < 0.01), and this association was more significant in HER2‐negative and grade 1&2 tumors than in HER2‐positive and grade 3 tumors. ALK pathway activity was also positively associated with recurrence risk in breast cancer patients from 30 datasets annotated with survival information (overall hazard ratio = 1.21, P < 0.01), particularly in patients with age > 50 years old, with positive lymph nodes, or with residual disease after neoadjuvant chemotherapy.

Conclusions

ALK may be involved in breast cancer tumorigenesis, and ALK pathway signature score may serve as a prognostic biomarker for breast cancer.

Recent advances in the NEK7-licensed NLRP3 inflammasome activation: Mechanisms, role in diseases and related inhibitors

The nucleotide-binding oligomerization domain (NOD)-like receptor containing pyrin domain 3 (NLRP3) inflammasome is a high-molecular-weight complex mediated by the activation of pattern-recognition receptors (PRRs) seed in innate immunity. Once NLRP3 is activated, the following recruitment of the adapter apoptosis-associated speck-like protein containing a caspase recruitment domain (CARD) (ASC) and procaspase-1 would be initiated. Cleavage of procaspase-1 into active caspase-1 then leads to the maturation of the precursor forms of interleukin (IL)-1β and IL-18 into biologically active IL-1β and IL-18. The activation of NLRP3 inflammasome is thought to be tightly associated with a regulator never in mitosis A (NIMA)-related kinase 7 (NEK7), apart from other signaling events such as K⁺ efflux and reactive oxygen species (ROS). Plus, the NLRP3 inflammasome has been linked to various metabolic disorders, chronic inflammation and other diseases. In this review, we firstly describe the cellular/molecular mechanisms of the NEK7-licensed NLRP3 inflammasome activation. Then we detail the potential inhibitors that can selectively and effectively modulate either the NEK7-NLRP3 complex itself or the related molecular/cellular events. Finally, we describe some inhibitors as promising therapeutic strategies for diverse diseases driven by NLRP3 inflammasome.

Identification of ALK in Thinness

There is considerable inter-individual variability in susceptibility to weight gain despite an equally obesogenic environment in large parts of the world. Whereas many studies have focused on identifying the genetic susceptibility to obesity, we performed a GWAS on metabolically healthy thin individuals (lowest 6th percentile of the population-wide BMI spectrum) in a uniquely phenotyped Estonian cohort. We discovered anaplastic lymphoma kinase (ALK) as a candidate thinness gene. In Drosophila, RNAi mediated knockdown of Alk led to decreased triglyceride levels. In mice, genetic deletion of Alk resulted in thin animals with marked resistance to diet- and leptin-mutation-induced obesity. Mechanistically, we found that ALK expression in hypothalamic neurons controls energy expenditure via sympathetic control of adipose tissue lipolysis. Our genetic and mechanistic experiments identify ALK as a thinness gene, which is involved in the resistance to weight gain.

ALK Inhibitors-Induced M Phase Delay Contributes to the Suppression of Cell Proliferation

Anaplastic lymphoma kinase (ALK), a receptor-type tyrosine kinase, is involved in the pathogenesis of several cancers. ALK has been targeted with small molecule inhibitors for the treatment of different cancers, but absolute success remains elusive. In the present study, the effects of ALK inhibitors on M phase progression were evaluated. Crizotinib, ceritinib, and TAE684 suppressed proliferation of neuroblastoma SH-SY5Y cells in a concentration-dependent manner. At approximate IC₅₀ concentrations, these inhibitors caused misorientation of spindles, misalignment of chromosomes and reduction in autophosphorylation. Similarly, knockdown of ALK caused M phase delay, which was rescued by re-expression of ALK. Time-lapse imaging revealed that anaphase onset was delayed. The monopolar spindle 1 (MPS1) inhibitor, AZ3146, and MAD2 knockdown led to a release from inhibitor-induced M phase delay, suggesting that spindle assembly checkpoint may be activated in ALK-inhibited cells. H2228 human lung carcinoma cells that express EML4-ALK fusion showed M phase delay in the presence of TAE684 at about IC₅₀ concentrations. These results suggest that ALK plays a role in M phase regulation and ALK inhibition may contribute to the suppression of cell proliferation in ALK-expressing cancer cells.

Receptor Tyrosine Kinases as Therapeutic Targets for Alcohol Use Disorder

The receptor tyrosine kinases (RTKs) are a large family of proteins that transduce extracellular signals to the inside of the cell to ultimately affect important cellular functions such as cell proliferation, survival, apoptosis, differentiation, and migration. They are expressed in the nervous system and can regulate behavior through modulation of neuronal and glial function. As a result, RTKs are implicated in neurodegenerative and psychiatric disorders such as depression and addiction. Evidence has emerged that 5 RTKs (tropomyosin-related kinase B (TrkB), RET proto-oncogene (RET), anaplastic lymphoma kinase (ALK), fibroblast growth factor receptor (FGFR), and epidermal growth factor receptor (EGFR)) modulate alcohol drinking and other behaviors related to alcohol addiction. RTKs are considered highly "druggable" targets and small-molecule inhibitors of RTKs have been developed for the treatment of various conditions, particularly cancer. These kinases are therefore attractive targets for the development of new pharmacotherapies to treat alcohol use disorder (AUD). This review will examine the preclinical evidence describing TrkB, RET, ALK, FGFR, and EGFR modulation of alcohol drinking and other behaviors relevant to alcohol abuse.

Anaplastic Lymphoma Kinase Regulates Internalization of the Dopamine D2 Receptor

The dopamine D2 receptor (D2R) is a G protein-coupled receptor (GPCR) expressed in regions of the brain that control motor function, cognition, and motivation. As a result, D2R is involved in the pathophysiology of disorders such as schizophrenia and drug addiction. Understanding the signaling pathways activated by D2R is crucial to finding new therapeutic targets for these disorders. D2R stimulation by its agonist, dopamine, causes desensitization and internalization of the receptor. A previous study found that inhibitors of the receptor tyrosine kinase anaplastic lymphoma kinase (ALK) blocked D2R desensitization in neurons in the ventral tegmental area of the brain. In the present study, using a cell-based system, we investigated whether ALK regulates D2R internalization. The ALK inhibitor alectinib completely inhibited dopamine-induced D2R internalization. Since GPCRs can transactivate receptor tyrosine kinases, we also examined if D2R stimulation activated ALK signaling. ALK phosphorylation increased by almost 2-fold after dopamine treatment and ALK coimmunoprecipitated with D2R. To identify the signaling pathways downstream of ALK that might regulate D2R internalization, we used pharmacological inhibitors of proteins activated by ALK signaling. Protein kinase Cγ was activated by dopamine in an ALK-dependent manner, and a protein kinase C inhibitor completely blocked dopamine-induced D2R internalization. Taken together, these results identify ALK as a receptor tyrosine kinase transactivated by D2R that promotes its internalization, possibly through activation of protein kinase C. ALK inhibitors could be useful in enhancing D2R signaling. SIGNIFICANCE STATEMENT: Receptor internalization is a mechanism by which receptors are desensitized. In this study we found that agonist-induced internalization of the dopamine D2 receptor is regulated by the receptor tyrosine kinase ALK. ALK was also transactivated by and associated with dopamine D2 receptor. Dopamine activated protein kinase C in an ALK-dependent manner and a PKC inhibitor blocked dopamine D2 receptor internalization. These results indicate that ALK regulates dopamine D2 receptor trafficking, which has implications for psychiatric disorders involving dysregulated dopamine signaling.

Inhibition of RPTPβ/ζ blocks ethanol-induced conditioned place preference in pleiotrophin knockout mice

Pleiotrophin (PTN) and Midkine (MK) are neurotrophic factors that are upregulated in the prefrontal cortex after alcohol administration and have been shown to reduce ethanol drinking and reward. PTN and MK are endogenous inhibitors of Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ. Interestingly, pharmacological inhibition of RPTPβ/ζ reduces ethanol consumption and blocks ethanol-induced conditioned place preference (CPP) in wild type mice. Since PTN-knockout (Ptn^-/-) mice are more sensitive to the conditioning effects of alcohol, we aimed to test the effects of MY10, a small-molecule inhibitor of RPTPβ/ζ, on ethanol-induced CPP in Ptn^-/- mice. The data presented here demonstrate for the first time that a regular dose of MY10, known to block ethanol consumption and reward in wild type mice, also blocks the rewarding effects of ethanol in the more vulnerable individuals lacking PTN, the endogenous inhibitor of RPTPβ/ζ. In addition, since MY10 readily penetrates the blood brain barrier (BBB), we tested its effects in a series of behavioural tests in Ptn^+/+ and Ptn^-/- mice. The data indicate that MY10 does not cause gross behavioural effects in wild type mice. However, MY10 tended to induce anxiolytic effects in Ptn^-/- mice in the elevated plus maze paradigm. Overall, the data indicate that MY10 rescues Ptn^-/- mice from their increased susceptibility to the conditioning effects of ethanol and may induce anxiolytic effects in individuals with reduced or absent PTN functions. Further studies are needed to confirm the potential of pharmacological inhibition of RPTPβ/ζ as a new therapeutic strategy in the treatment of anxiety-related disorders.

Connecting Metainflammation and Neuroinflammation Through the PTN-MK-RPTPβ/ζ Axis: Relevance in Therapeutic Development

Inflammation is a common factor of pathologies such as obesity, type 2 diabetes or neurodegenerative diseases. Chronic inflammation is considered part of the pathogenic mechanisms of different disorders associated with aging. Interestingly, peripheral inflammation and the associated metabolic alterations not only facilitate insulin resistance and diabetes but also neurodegenerative disorders. Therefore, the identification of novel pathways, common to the development of these diseases, which modulate the immune response and signaling is key. It will provide highly relevant information to advance our knowledge of the multifactorial process of aging, and to establish new biomarkers and/or therapeutic targets to counteract the underlying chronic inflammatory processes. One novel pathway that regulates peripheral and central immune responses is triggered by the cytokines pleiotrophin (PTN) and midkine (MK), which bind its receptor, Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ, and inactivate its phosphatase activity. In this review, we compile a growing body of knowledge suggesting that PTN and MK modulate the immune response and/or inflammation in different pathologies characterized by peripheral inflammation associated with insulin resistance, such as aging, and in central disorders characterized by overt neuroinflammation, such as neurodegenerative diseases and endotoxemia. Evidence strongly suggests that regulation of the PTN and MK signaling pathways may provide new therapeutic opportunities particularly in those neurological disorders characterized by increased PTN and/or MK cerebral levels and neuroinflammation. Importantly, we discuss existing therapeutics, and others being developed, that modulate these signaling pathways, and their potential use in pathologies characterized by overt neuroinflammation.

The Expression, Functions, Interactions and Prognostic Values of PTPRZ1: A Review and Bioinformatic Analysis

Available studies demonstrate that receptor-type tyrosine-protein phosphatase zeta (PTPRZ1) is expressed in different tumor tissues, and functions in cell proliferation, cell adhesion and migration, epithelial-to-mesenchymal transition, cancer stem cells and treatment resistance by interacting with or binding to several molecules. These included pleiotrophin (PTN), midkine, interleukin-34, β-catenin, VEGF, NF-κB, HIF-2, PSD-95, MAGI-3, contactin and ErbB4. PTPRZ1 was involved in survival signaling and could predict the prognosis of several tumors. This review discusses: the current knowledge about PTPRZ1, its expression, co-receptors, ligands, functions, signaling pathway, prognostic values and therapeutic agents that target PTPRZ1.

Pleiotrophin: Analysis of the endothelialisation potential

PURPOSE

Endothelialisation of vascular substitutes, in fact, remains one of the most unsolved problems in cardiovascular diseases treatment. Stromal Derived Factor 1 (SDF-1) has been largely investigated as an endothelialisation promoter and Pleiotrophin is a promising alternative. Although it has been known to exert beneficial effects on different cell types, its potential as an inducer of proliferation and migration of endothelial cells was not investigated. Therefore, this work is aimed to compare the effects of Pleiotrophin on proliferation and migration of endothelial cells with respect to SDF-1.

MATERIALS/METHODS

Endothelial cell line EA.hy926 was treated with Pleiotrophin (50 ng/ml) or SDF-1 (50 ng/ml). Cell viability was evaluated by MTT assay and migration assays were performed in Transwell chambers. Wound healing potential was evaluated by scratch wound assay. CXCR4, RPTP β/ζ, PCNA and Rac1 expression was detected by Western Blot.

RESULTS

Interestingly, Pleiotrophin significantly increased the viability of the treated endothelial cells with respects to SDF-1. The migratory ability of the endothelial cells was also improved in the presence of Pleiotrophin with reference to the SDF-1 treatment. Moreover, Western Blot analysis showed how the treatment with Pleiotrophin can induce an increase in the expression of RPTP β/ζ, PCNA and Rac1 compared to SDF-1.

CONCLUSION

Due to the significant effects exerted on viability, migration and repair ability of endothelial cells compared to SDF-1, Pleiotrophin can be considered as an interesting molecule to promote re-endothelialisation.

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.

Pharmacological inhibition of Receptor Protein Tyrosine Phosphatase β/ζ (PTPRZ1) modulates behavioral responses to ethanol

Pleiotrophin (PTN) and Midkine (MK) are neurotrophic factors that are upregulated in the prefrontal cortex after alcohol administration and have been shown to reduce ethanol drinking and reward. PTN and MK are the endogenous inhibitors of Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ (a.k.a. PTPRZ1, RPTPβ, PTPζ), suggesting a potential role for this phosphatase in the regulation of alcohol effects. To determine if RPTPβ/ζ regulates ethanol consumption, we treated mice with recently developed small-molecule inhibitors of RPTPβ/ζ (MY10, MY33-3) before testing them for binge-like drinking using the drinking in the dark protocol. Mice treated with RPTPβ/ζ inhibitors, particularly with MY10, drank less ethanol than controls. MY10 treatment blocked ethanol conditioned place preference, showed limited effects on ethanol-induced ataxia, and potentiated the sedative effects of ethanol. We also tested whether RPTPβ/ζ is involved in ethanol signaling pathways. We found that ethanol treatment of neuroblastoma cells increased phosphorylation of anaplastic lymphoma kinase (ALK) and TrkA, known substrates of RPTPβ/ζ. Treatment of neuroblastoma cells with MY10 or MY33-3 also increased levels of phosphorylated ALK and TrkA. However, concomitant treatment of neuroblastoma cells with ethanol and MY10 or MY33-3 prevented the increase in pTrkA and pALK. These results demonstrate for the first time that ethanol engages TrkA signaling and that RPTPβ/ζ modulates signaling pathways activated by alcohol and behavioral responses to this drug. The data support the hypothesis that RPTPβ/ζ might be a novel target of pharmacotherapy for reducing excessive alcohol consumption.

ALK is required for NLRP3 inflammasome activation in macrophages

The NLRP3 inflammasome is a key mediator of host immune responses through the induction of pyroptosis and the release of cytokines. Although the pathologic role of inflammasome in infection and sterile inflammation is well known, the mechanism and regulation of NLRP3 inflammasome activation remains obscure. Here, we report that anaplastic lymphoma kinase (ALK) is a novel regulator of NLRP3 inflammasome activation in macrophages. Pharmacologic or genetic inhibition of ALK through targeted drugs (ceritinib and lorlatinib) or RNAi blocked extracellular ATP-induced NLRP3 inflammasome activation in macrophages. Mechanically, ALK-mediated NF-κB activation was required for the priming step of NLRP3 upregulation, whereas ALK-mediated lipid peroxidation contributed to the sensing step of NLRP3-NEK7 complex formation. These studies indicate that inhibition of ALK could be utilized to treat NLRP3-related inflammatory diseases.

Role and targeting of anaplastic lymphoma kinase in cancer

Anaplastic lymphoma kinase (ALK) gene activation is involved in the carcinogenesis process of several human cancers such as anaplastic large cell lymphoma, lung cancer, inflammatory myofibroblastic tumors and neuroblastoma, as a consequence of fusion with other oncogenes (NPM, EML4, TIM, etc) or gene amplification, mutation or protein overexpression.

ALK is a transmembrane tyrosine kinase receptor that, upon ligand binding to its extracellular domain, undergoes dimerization and subsequent autophosphorylation of the intracellular kinase domain. When activated in cancer it represents a target for specific inhibitors, such as crizotinib, ceritinib, alectinib etc. which use has demonstrated significant effectiveness in ALK-positive patients, in particular ALK-positive non- small cell lung cancer.

Several mechanisms of resistance to these inhibitors have been described and new strategies are underway to overcome the limitations of current ALK inhibitors.

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.

The Extended Family of Protein Tyrosine Phosphatases

In higher eukaryotes, the Tyr phosphorylation status of cellular proteins results from the coordinated action of Protein Tyrosine Kinases (PTKs) and Protein Tyrosine Phosphatases (PTPs). PTPs have emerged as highly regulated enzymes with diverse substrate specificity, and proteins with Tyr-dephosphorylation or Tyr-dephosphorylation-like properties can be clustered as the PTPome. This includes proteins from the PTP superfamily, which display a Cys-based catalytic mechanism, as well as enzymes from other gene families (Asp-based phosphatases, His-based phosphatases) that have converged in protein Tyr-dephosphorylation-related functions by using non-Cys-based catalytic mechanisms. Within the Cys-based members of the PTPome, classical PTPs dephosphorylate specific phosphoTyr (pTyr) residues from protein substrates, whereas VH1-like dual-specificity PTPs dephosphorylate pTyr, pSer, and pThr residues, as well as nonproteinaceous substrates, including phosphoinositides and phosphorylated carbohydrates. In addition, several PTPs have impaired catalytic activity as a result of amino acid substitutions at their active sites, but retain regulatory functions related with pTyr signaling. As a result of their relevant biological activity, many PTPs are linked to human disease, including cancer, neurodevelopmental, and metabolic diseases, making these proteins important drug targets and molecular markers in the clinic. Here, a brief overview on the biochemistry and physiology of the different groups of proteins that belong to the mammalian PTPome is presented.

Development of inhibitors of receptor protein tyrosine phosphatase β/ζ (PTPRZ1) as candidates for CNS disorders

A new series of blood-brain barrier permeable molecules designed to mimic the activity of Pleiotrophin in the CNS has been designed and synthesized. These compounds exert their action by interacting with the intracellular domain PD1 of the Protein Tyrosine-Phosphatase Receptor Z1 (PTPRZ1), and inhibiting its tyrosine phosphatase activity. The most potent compounds 10a and 12b (IC₅₀ = 0,1 μM) significantly increase the phosphorylation of key tyrosine residues of PTPRZ1 substrates involved in neuronal survival and differentiation, and display protective effects against amphetamine-induced toxicity. Docking and molecular dynamics experiments have been used to analyze the binding mode and to explain the observed selectivity against PTP1B. An In vivo experiment has demonstrated that 10a can cross the BBB, thus promoting the possibility of moving forward these candidates for the development of drugs for the treatment of CNS disorders, such as drug addiction and neurodegenerative diseases.

Therapeutic silence of pleiotrophin by targeted delivery of siRNA and its effect on the inhibition of tumor growth and metastasis

Pleiotrophin (PTN) is a secreted cytokine that is expressed in various cancer cell lines and human tumor such as colon cancer, lung cancer, gastric cancer and melanoma. It plays significant roles in angiogenesis, metastasis, differentiation and cell growth. The expression of PTN in the adult is limited to the hippocampus in an activity-dependent manner, making it a very attractive target for cancer therapy. RNA interference (RNAi) offers great potential as a new powerful therapeutic strategy based on its highly specific and efficient silencing of a target gene. However, efficient delivery of small interfering RNA (siRNA) in vivo remains a significant hurdle for its successful therapeutic application. In this study, we first identified, on a cell-based experiment, applying a 1:1 mixture of two PTN specific siRNA engenders a higher silencing efficiency on both mRNA and protein level than using any of them discretely at the same dose. As a consequence, slower melanoma cells growth was also observed for using two specific siRNA combinatorially. To establish a robust way for siRNA delivery in vivo and further investigate how silence of PTN affects tumor growth, we tested three different methods to deliver siRNA in vivo: first non-targeted in-vivo delivery of siRNA via jetPEI; second lung targeted delivery of siRNA via microbubble coated jetPEI; third tumor cell targeted delivery of siRNA via transferrin-polyethylenimine (Tf-PEI). As a result, we found that all three in-vivo siRNAs delivery methods led to an evident inhibition of melanoma growth in non-immune deficiency C57BL/6 mice without a measureable change of ALT and AST activities. Both targeted delivery methods showed more significant curative effect than jetPEI. The lung targeted delivery by microbubble coated jetPEI revealed a comparable therapeutic effect with Tf-PEI, indicating its potential application for target delivery of siRNA in vivo.

Anaplastic lymphoma kinase regulates binge-like drinking and dopamine receptor sensitivity in the ventral tegmental area

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase associated with alcohol dependence in humans and behavioral responses to ethanol in mice. To characterize the ability of ALK to control ethanol consumption, we treated mice with the ALK inhibitors TAE684 or alectinib before testing them for binge-like drinking using the drinking in the dark protocol. Mice treated with ALK inhibitors drank less ethanol than controls. In addition, TAE684 treatment abolished ethanol conditioned place preference, indicating that ALK regulates the rewarding properties of ethanol. Because the ventral tegmental area (VTA) is a key brain region involved in the rewarding effects of ethanol, we determined if Alk expression in the VTA is important for binge-like ethanol consumption. Mice expressing a short hairpin ribonucleic acid targeting Alk in the VTA drank less ethanol compared with controls. ALK is expressed on dopamine (DA) neurons in the VTA, suggesting that ALK might regulate their firing properties. Extracellular recordings of putative DA neurons in VTA slices demonstrated that ALK inhibition did not affect the ability of ethanol to stimulate, or DA to inhibit, the firing of DA neurons. However, inhibiting ALK attenuated the time-dependent reversal of inhibition produced by moderate concentrations of DA, suggesting that ALK affects DA D2 autoreceptor (D2R) desensitization. Altered desensitization of the D2R changes the firing of DA neurons and is predicted to affect DA levels and alcohol drinking. These data support the possibility that ALK might be a novel target of pharmacotherapy for reducing excessive alcohol consumption.

From top to bottom: midkine and pleiotrophin as emerging players in immune regulation

Cytokines are pivotal in the generation and resolution of the inflammatory response. The midkine/pleiotrophin (MK/PTN) family of cytokines, composed of just two members, was discovered as heparin-binding neurite outgrowth-promoting factors. Since their discovery, expression of this cytokine family has been reported in a wide array of inflammatory diseases and cancer. In this minireview, we will discuss the emerging appreciation of the functions of the MK/PTN family in the immune system, which include promoting lymphocyte survival, sculpting myeloid cell phenotype, driving immune cell chemotaxis, and maintaining hematopoiesis.

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.

Anaplastic lymphoma kinase: Role in cancer and therapy perspective

Anaplastic lymphoma kinase (ALK) is correlated with oncogenesis in different types of cancers, such as anaplastic large cell lymphoma, lung cancer, neuroblastoma, and even breast cancer, by abnormal fusion of ALK or non-fusion ALK activation. ALK is a receptor tyrosine kinase, with a single transmembrane domain, that plays an important role in development. Upon ligand binding to the extracellular domain, the receptor undergoes dimerization and subsequent autophosphorylation of the intracellular kinase domain. In recent years, ALK inhibitors have been developed for cancer treatment. These inhibitors target ALK activity and show effectiveness in ALK-positive non-small cell lung cancer. However, acquired treatment resistance makes the future of this therapy unclear; new strategies are underway to overcome the limitations of current ALK inhibitors.

Pleiotrophin exerts its migration and invasion effect through the neuropilin-1 pathway

Pleiotrophin (PTN) is a pleiotropic growth factor that exhibits angiogenic properties and is involved in tumor growth and metastasis. Although it has been shown that PTN is expressed in tumor cells, few studies have investigated its receptors and their involvement in cell migration and invasion. Neuropilin-1 (NRP-1) is a receptor for multiple growth factors that mediates cell motility and plays an important role in angiogenesis and tumor progression. Here we provide evidence for the first time that NRP-1 is crucial for biological activities of PTN. We found that PTN interacted directly with NRP-1 through its thrombospondin type-I repeat domains. Importantly, binding of PTN to NRP-1 stimulated the internalization and recycling of NRP-1 at the cell surface. Invalidation of NRP-1 by RNA interference in human carcinoma cells inhibited PTN-induced intracellular signaling of the serine-threonine kinase, mitogen-activated protein MAP kinase, and focal adhesion kinase pathways. Accordingly, NRP-1 silencing or blocking by antibody inhibited PTN-induced human umbilical vein endothelial cell migration and tumor cell invasion. These results suggest that NRP-1/PTN interaction provides a novel mechanism for controlling the response of endothelial and tumoral cells to PTN and may explain, at least in part, how PTN contributes to tumor angiogenesis and cancer progression.

Breast cancer carcinoma-associated fibroblasts differ from breast fibroblasts in immunological and extracellular matrix regulating pathways

Tumor stroma has been recently shown to play a crucial role in the development of breast cancer. Since the origin of the stromal cells in the tumor is unknown, we have examined differences and similarities between three stromal cell types of mesenchymal origin, namely carcinoma associated fibroblasts from breast tumor (CAFs), fibroblasts from normal breast area (NFs) and bone marrow derived mesenchymal stromal cells (MSCs). In a microarray analysis, immunological, developmental and extracellular matrix -related pathways were over-represented in CAFs when compared to NFs (p<0.001). Under hypoxic conditions, the expression levels of pyruvate dehydrogenase kinase-1 (PDK1) and pyruvate dehydrogenase kinase-4 (PDK4) were lower in CAFs when compared to NFs (fold changes 0.6 and 0.4, respectively). In normoxia, when compared to NFs, CAFs displayed increased expression of glucose transporter 1 (GLUT-1) and PDK1 (fold changes 1.5 and 1.3, respectively). With respect to the assessed surface markers, only CD105 was expressed differently in MSCs when compared to fibroblasts, being more often expressed on MSCs. Cells with myofibroblast features were present in both NF and CAF samples. We conclude, that CAFs differ distinctly from NFs at the gene expression level, this hypothesis was also tested in silico for other available gene expression data.

Pleiotrophin regulates the ductular reaction by controlling the migration of cells in liver progenitor niches

OBJECTIVE

The ductular reaction (DR) involves mobilisation of reactive-appearing duct-like cells (RDC) along canals of Hering, and myofibroblastic (MF) differentiation of hepatic stellate cells (HSC) in the space of Disse. Perivascular cells in stem cell niches produce pleiotrophin (PTN) to inactivate the PTN receptor, protein tyrosine phosphatase receptor zeta-1 (PTPRZ1), thereby augmenting phosphoprotein-dependent signalling. We hypothesised that the DR is regulated by PTN/PTPRZ1 signalling.

DESIGN

PTN-GFP, PTN-knockout (KO), PTPRZ1-KO, and wild type (WT) mice were examined before and after bile duct ligation (BDL) for PTN, PTPRZ1 and the DR. RDC and HSC from WT, PTN-KO, and PTPRZ1-KO mice were also treated with PTN to determine effects on downstream signaling phosphoproteins, gene expression, growth, and migration. Liver biopsies from patients with DRs were also interrogated.

RESULTS

Although quiescent HSC and RDC lines expressed PTN and PTPRZ1 mRNAs, neither PTN nor PTPRZ1 protein was demonstrated in healthy liver. BDL induced PTN in MF-HSC and increased PTPRZ1 in MF-HSC and RDC. In WT mice, BDL triggered a DR characterised by periportal accumulation of collagen, RDC and MF-HSC. All aspects of this DR were increased in PTN-KO mice and suppressed in PTPRZ1-KO mice. In vitro studies revealed PTN-dependent accumulation of phosphoproteins that control cell-cell adhesion and migration, with resultant inhibition of cell migration. PTPRZ1-positive cells were prominent in the DRs of patients with ductal plate defects and adult cholestatic diseases.

CONCLUSIONS

PTN, and its receptor, PTPRZ1, regulate the DR to liver injury by controlling the migration of resident cells in adult liver progenitor niches.

Mutation-Independent Activation of the Anaplastic Lymphoma Kinase in Neuroblastoma

Activating mutations of anaplastic lymphoma kinase (ALK) have been identified as important players in neuroblastoma development. Our goal was to evaluate the significance of overall ALK activation in neuroblastoma. Expression of phosphorylated ALK, ALK, and its putative ligands, pleiotrophin and midkine, was screened in 289 neuroblastomas and 56 paired normal tissues. ALK was expressed in 99% of tumors and phosphorylated in 48% of cases. Pleiotrophin and midkine were expressed in 58% and 79% of tumors, respectively. ALK activation was significantly higher in tumors than in paired normal tissues, together with ALK and midkine expression. ALK activation was largely independent of mutations and correlated with midkine expression in tumors. ALK activation in tumors was associated with favorable features, including a younger age at diagnosis, hyperdiploidy, and detection by mass screening. Antitumor activity of the ALK inhibitor TAE684 was evaluated in wild-type or mutated ALK neuroblastoma cell lines and xenografts. TAE684 was cytotoxic in vitro in all cell lines, especially those harboring an ALK mutation. TAE684 efficiently inhibited ALK phosphorylation in vivo in both F1174I and R1275Q xenografts but demonstrated antitumor activity only against the R1275Q xenograft. In conclusion, ALK activation occurs frequently during neuroblastoma oncogenesis, mainly through mutation-independent mechanisms. However, ALK activation is not associated with a poor outcome and is not always a driver of cell proliferation and/or survival in neuroblastoma.

ALK alteration is a frequent event in aggressive breast cancers

INTRODUCTION

Breast cancer is the most common female malignancy worldwide and, despite improvements in treatment modalities, there are increased chances of recurrence and metastasis in a substantial number of cases and it remains one of the major causes of mortality among female cancer patients. Anaplastic lymphoma kinase (ALK) gene has been found to be altered in several solid and hematologic tumors. We aimed to comprehensively study the prevalence of ALK expression, and changes in copy number and translocation in a large cohort of breast cancer cases in a Middle Eastern population.

METHODS

ALK protein expression was investigated by immunohistochemistry and numerical and structural variations of the ALK gene were analyzed by fluorescence in situ hybridization (FISH) in a tissue microarray format in a cohort of more than 1000 Middle Eastern breast cancers. The data were correlated with clinicopathologic parameters and other important molecular biomarkers.

RESULTS

Immunohistochemical analysis showed ALK overexpression in 36.0 % of the breast cancer patients and gene amplification was present in 13.3 % of cases, seen by FISH analyses. ALK overexpression was significantly associated with ALK gene amplification (p = 0.0031). ALK-overexpressing tumors showed significant association with high-grade tumors (p = 0.0039), ductal histologic subtype (p = 0.0076), triple-negative phenotype (p = 0.0034), and high Ki-67 (p = 0.0001) and p-AKT (p <0.0001).

CONCLUSIONS

Immunohistochemical analysis showed ALK is overexpressed in a substantial proportion of breast cancers and possibly plays a significant role in the aggressive behavior of this cancer. Gene amplification is hypothesized to be a possible cause for a significant proportion of this overexpression. Based on these findings, a potential role for an ALK inhibitor, as a therapeutic agent targeting aggressive subtypes of breast cancer, merits further investigation.

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.

Understanding the Interplay between Expression, Mutation and Activity of ALK Receptor in Rhabdomyosarcoma Cells for Clinical Application of Small-Molecule Inhibitors

BACKGROUND

Receptor tyrosine kinases (RTKs) have a central role in cancer initiation and progression, since changes in their expression and activity potentially results in cell transformation. This concept is essential from a therapeutic standpoint, as clinical evidence indicates that tumours carrying deregulated RTKs are particularly susceptible to their activity but also to their inhibition. Rhabdomyosarcoma (RMS) is an aggressive childhood cancer where emerging therapies rely on the use kinase inhibitors, and among druggable kinases ALK represents a potential therapeutic target to commit efforts against. However, the functional relevance of ALK in RMS is not known, likewise the multi-component deregulated RTK profile to which ALK belongs.

METHODS

In this study we used RMS cell lines representative of the alveolar and embrional histotype and looked at ALK intracellular localization, activity and cell signalling.

RESULTS

We found that ALK was properly located at the plasma membrane of RMS cells, though in an unphosphorylated and inactive state due to intracellular tyrosine phosphatases (PTPases) activity. Indeed, increase of ALK phosphorylation was observed upon PTPase inhibition, as well as after ligand binding or protein overexpression. In these conditions, ALK signalling proceeded through the MAPK/ERK and PI3K/AKT pathways, and it was susceptible to ATP-competitive inhibitors exposure. However, drug-induced growth inhibition, cell cycle arrest and apoptosis did not correlate with ALK expression only, but relied also on the expression of other RTKs with akin drug binding affinity. Indeed, analysis of baseline and inducible RTK phosphorylation confirmed that RMS cells were susceptible to ALK kinase inhibitors even in the absence of the primary intended target, due to the presence of compensatory RTKs signalling pathways.

CONCLUSIONS

These data, hence, provided evidences of a potentially active role of ALK in RMS cells, but also suggest caution in considering ALK a major therapeutic target in this malignancy, particularly if expression and activity cannot be accurately determined.

Intracellular and extracellular domains of protein tyrosine phosphatase PTPRZ-B differentially regulate glioma cell growth and motility

Gliomas are primary brain tumors for which surgical resection and radiotherapy is difficult because of the diffuse infiltrative growth of the tumor into the brain parenchyma. For development of alternative, drug-based, therapies more insight in the molecular processes that steer this typical growth and morphodynamic behavior of glioma cells is needed. Protein tyrosine phosphatase PTPRZ-B is a transmembrane signaling molecule that is found to be strongly up-regulated in glioma specimens. We assessed the contribution of PTPRZ-B protein domains to tumor cell growth and migration, via lentiviral knock-down and over-expression using clinically relevant glioma xenografts and their derived cell models. PTPRZ-B knock-down resulted in reduced migration and proliferation of glioma cells in vitro and also inhibited tumor growth in vivo. Interestingly, expression of only the PTPRZ-B extracellular segment was sufficient to rescue the in vitro migratory phenotype that resulted from PTPRZ-B knock-down. In contrast, PTPRZ-B knock-down effects on proliferation could be reverted only after re-expression of PTPRZ-B variants that contained its C-terminal PDZ binding domain. Thus, distinct domains of PTPRZ-B are differentially required for migration and proliferation of glioma cells, respectively. PTPRZ-B signaling pathways therefore represent attractive therapeutic entry points to combat these tumors.

Peptides derived from the dependence receptor ALK are proapoptotic for ALK-positive tumors

ALK is a receptor tyrosine kinase with an oncogenic role in various types of human malignancies. Despite constitutive activation of the kinase through gene alterations, such as chromosomal translocation, gene amplification or mutation, treatments with kinase inhibitors invariably lead to the development of resistance. Aiming to develop new tools for ALK targeting, we took advantage of our previous demonstration identifying ALK as a dependence receptor, implying that in the absence of ligand the kinase-inactive ALK triggers or enhances apoptosis. Here, we synthesized peptides mimicking the proapoptotic domain of ALK and investigated their biological effects on tumor cells. We found that an ALK-derived peptide of 36 amino acids (P36) was cytotoxic for ALK-positive anaplastic large-cell lymphoma and neuroblastoma cell lines. In contrast, ALK-negative tumor cells and normal peripheral blood mononuclear cells were insensitive to P36. The cytotoxic effect was due to caspase-dependent apoptosis and required N-myristoylation of the peptide. Two P36-derived shorter peptides as well as a cyclic peptide also induced apoptosis. Surface plasmon resonance and mass spectrometry analysis of P36-interacting proteins from two responsive cell lines, Cost lymphoma and SH-SY5Y neuroblastoma, uncovered partners that could involve p53-dependent signaling and pre-mRNA splicing. Furthermore, siRNA-mediated knockdown of p53 rescued these cells from P36-induced apoptosis. Finally, we observed that a treatment combining P36 with the ALK-specific inhibitor crizotinib resulted in additive cytotoxicity. Therefore, ALK-derived peptides could represent a novel targeted therapy for ALK-positive tumors.

Pleiotrophin as a central nervous system neuromodulator, evidences from the hippocampus

Pleiotrophin (PTN) is a secreted growth factor, and also a cytokine, associated with the extracellular matrix, which has recently starting to attract attention as a significant neuromodulator with multiple neuronal functions during development. PTN is expressed in several tissues, where its signals are generally related with cell proliferation, growth, and differentiation by acting through different receptors. In Central Nervous System (CNS), PTN exerts post-developmental neurotrophic and -protective effects, and additionally has been involved in neurodegenerative diseases and neural disorders. Studies in Drosophila shed light on some aspects of the different levels of regulatory control of PTN invertebrate homologs. Specifically in hippocampus, recent evidence from PTN Knock-out (KO) mice involves PTN functioning in learning and memory. In this paper, we summarize, discuss, and contrast the most recent advances and results that lead to proposing a PTN as a neuromodulatory molecule in the CNS, particularly in hippocampus.

Identification of genome-wide SNP-SNP and SNP-clinical Boolean interactions in age-related macular degeneration

We propose here a methodology to uncover modularities in the network of SNP-SNP interactions most associated with disease. We start by computing all possible Boolean binary SNP interactions across the whole genome. By constructing a weighted graph of the most relevant interactions and via a combinatorial optimization approach, we find the most highly interconnected SNPs. We show that the method can be easily extended to find SNP/environment interactions. Using a modestly sized GWAS dataset of age-related macular degeneration (AMD), we identify a group of only 19 SNPs, which include those in previously reported regions associated to AMD. We also uncover a larger set of loci pointing to a matrix of key processes and functions that are affected. The proposed integrative methodology extends and overlaps traditional statistical analysis in a natural way. Combinatorial optimization techniques allow us to find the kernel of the most central interactions, complementing current methods of GWAS analysis and also enhancing the search for gene-environment interaction.

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.

Pleiotrophin mediates hematopoietic regeneration via activation of RAS

Hematopoietic stem cells (HSCs) are highly susceptible to ionizing radiation-mediated death via induction of ROS, DNA double-strand breaks, and apoptotic pathways. The development of therapeutics capable of mitigating ionizing radiation-induced hematopoietic toxicity could benefit both victims of acute radiation sickness and patients undergoing hematopoietic cell transplantation. Unfortunately, therapies capable of accelerating hematopoietic reconstitution following lethal radiation exposure have remained elusive. Here, we found that systemic administration of pleiotrophin (PTN), a protein that is secreted by BM-derived endothelial cells, substantially increased the survival of mice following radiation exposure and after myeloablative BM transplantation. In both models, PTN increased survival by accelerating the recovery of BM hematopoietic stem and progenitor cells in vivo. PTN treatment promoted HSC regeneration via activation of the RAS pathway in mice that expressed protein tyrosine phosphatase receptor-zeta (PTPRZ), whereas PTN treatment did not induce RAS signaling in PTPRZ-deficient mice, suggesting that PTN-mediated activation of RAS was dependent upon signaling through PTPRZ. PTN strongly inhibited HSC cycling following irradiation, whereas RAS inhibition abrogated PTN-mediated induction of HSC quiescence, blocked PTN-mediated recovery of hematopoietic stem and progenitor cells, and abolished PTN-mediated survival of irradiated mice. These studies demonstrate the therapeutic potential of PTN to improve survival after myeloablation and suggest that PTN-mediated hematopoietic regeneration occurs in a RAS-dependent manner.