Defective Signal Transduction Research Articles

Association of Factor V Secretion with Protein Kinase B Signaling in Platelets from Horses with Atypical Equine Thrombasthenia.

BackgroundTwo congenital bleeding diatheses have been identified in Thoroughbred horses: Glanzmann thrombasthenia (GT) and a second, novel diathesis associated with abnormal platelet function in response to collagen and thrombin stimulation.Hypothesis/ObjectivesPlatelet dysfunction in horses with this second thrombasthenia results from a secretory defect.AnimalsTwo affected and 6 clinically normal horses.MethodsEx vivo study. Washed platelets were examined for (1) expression of the αIIb‐β3 integrin; (2) fibrinogen binding capacity in response to ADP and thrombin; (3) secretion of dense and α‐granules; (4) activation of the mammalian target of rapamycin (mTOR)‐protein kinase B (AKT) signaling pathway; and (5) cellular distribution of phosphatidylinositol‐4‐phosphate‐3‐kinase, class 2B (PIK3C2B) and SH2 containing inositol‐5′‐phosphatase 1 (SHIP1).ResultsPlatelets from affected horses expressed normal amounts of αIIb‐β3 integrin and bound fibrinogen normally in response to ADP, but bound 80% less fibrinogen in response to thrombin. α‐granules only released 50% as much Factor V as control platelets, but dense granules released their contents normally. Protein kinase B (AKT) phosphorylation was reduced after thrombin activation, but mTOR Complex 2 (mTORC2) and phosphoinositide‐dependent kinase 1 (PDK1) signaling were normal. SH2‐containing inositol‐5'‐phosphatase 1 (SHIP1) did not localize to the cytoskeleton of affected platelets and was decreased overall consistent with reduced AKT phosphorylation.Conclusions and clinical significanceDefects in fibrinogen binding, granule secretion, and signal transduction are unique to this thrombasthenia, which we designate as atypical equine thrombasthenia.

Abstract LB-230: SOCS5 mediates defective function of monocyte-derived dendritic cells in patients with chronic lymphocytic leukemia

Abstract Chronic lymphocytic leukemia (CLL) is the most common form of adult leukemia in Western countries. This clinically heterogeneous disease is characterized by the progressive accumulation of monoclonal B cells co-expressing CD5, CD19, CD20 and CD23 in the peripheral blood and in the primary and secondary lymphoid organs. Additionally, a range of immune cells are altered in patients with CLL. The resulting immunologic defects predispose patients to severe recurrent infections, which is the major life-threatening complication associated with CLL. Functional impairment of dendritic cells (DCs) in CLL not only diminishes the response to microorganisms, but it also allows for tumor escape from immune control. Understanding the mechanism for this effect can provide insight into the molecular regulation of DC function and may also suggest therapeutic strategies to reverse the immunosuppressive effect of tumors on DCs. To elucidate the mechanism for DC dysfunction in patients with CLL, we focused on signal transduction pathways that regulate the expression of genes necessary for the immune response. We found that monocytes from CLL patients have a decrease in IL-4-induced activation of the transcription factor STAT6, which prevents the phenotypic and functional maturation of DCs. This does not reflect a generalized defect in cytokine-induced signal transduction, as the activation of the related transcription factor STAT5 in response to GM-CSF is unaffected. Monocyte-derived DCs from CLL patients display low levels of HLA-DR, costimulatory molecules and CD83, and reduced secretion of pro-inflammatory cytokines. These changes are associated with low expression of TLR4 and related molecules, which decrease the ability of these cells to respond to stimulus afforded by LPS, impairing their complete maturation. Consequently, monocyte-derived DCs from CLL patients have decreased ability to induce proliferation of T-cells and display an increased induction of immune-suppressive regulatory T cell. Although monocytes from CLL patients exhibit high IL-4R expression, activation of the downstream transcription factor STAT6 is inhibited because of increased expression of the negative regulator SOCS5. It is known that CLL cells produce IL-10, leading to elevated serum levels of this cytokine. IL-10-treatment of monocytes from healthy donors mimics the alteration in signaling observed in patients, through enhanced STAT3-dependent expression of SOCS5, which inhibits STAT6 activation and leads to defective DC differentiation. These findings suggest that SOCS5 can mediate the impaired function of DCs in CLL patients, and may be a new potential therapeutic target for reversing cancer-associated immune suppression. Note: This abstract was not presented at the meeting. Citation Format: Patricia A. Toniolo, Suhu Liu, Sarah R. Walker, Jose Alexandre M. Barbuto, David A. Frank. SOCS5 mediates defective function of monocyte-derived dendritic cells in patients with chronic lymphocytic leukemia. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-230. doi:10.1158/1538-7445.AM2015-LB-230

Single-cell mass cytometry of TCR signaling: amplification of small initial differences results in low ERK activation in NOD mice.

Signaling from the T-cell receptor (TCR) conditions T-cell differentiation and activation, requiring exquisite sensitivity and discrimination. Using mass cytometry, a high-dimensional technique that can probe multiple signaling nodes at the single-cell level, we interrogate TCR signaling dynamics in control C57BL/6 and autoimmunity-prone nonobese diabetic (NOD) mice, which show ineffective ERK activation after TCR triggering. By quantitating signals at multiple steps along the signaling cascade and parsing the phosphorylation level of each node as a function of its predecessors, we show that a small impairment in initial pCD3ζ activation resonates farther down the signaling cascade and results in larger defects in activation of the ERK1/2-S6 and IκBα modules. This nonlinear property of TCR signaling networks, which magnifies small initial differences during signal propagation, also applies in cells from B6 mice activated at different levels of intensity. Impairment in pCD3ζ and pSLP76 is not a feedback consequence of a primary deficiency in ERK activation because no proximal signaling defect was observed in Erk2 KO T cells. These defects, which were manifest at all stages of T-cell differentiation from early thymic pre-T cells to memory T cells, may condition the imbalanced immunoregulation and tolerance in NOD T cells. More generally, this amplification of small initial differences in signal intensity may explain how T cells discriminate between closely related ligands and adopt strongly delineated cell fates.

Ethylene signalling affects susceptibility of tomatoes to Salmonella

Fresh fruits and vegetables are increasingly recognized as important reservoirs of human pathogens, and therefore, significant attention has been directed recently to understanding mechanisms of the interactions between plants and enterics, like Salmonella. A screen of tomato cultivars for their susceptibility to Salmonella revealed significant differences in the ability of this human pathogen to multiply within fruits; expression of the Salmonella genes (cysB, agfB, fadH) involved in the interactions with tomatoes depended on the tomato genotype and maturity stage. Proliferation of Salmonella was strongly reduced in the tomato mutants with defects in ethylene synthesis, perception and signal transduction. While mutation in the ripening-related ethylene receptor Nr resulted only in a modest reduction in Salmonella numbers within tomatoes, strong inhibition of the Salmonella proliferation was observed in rin and nor tomato mutants. RIN and NOR are regulators of ethylene synthesis and ripening. A commercial tomato variety heterozygous for rin was less susceptible to Salmonella under the greenhouse conditions but not when tested in the field over three production seasons.

Genetics of inherited platelet disorders

The current review describes inherited platelet disorders, illustrates their clinical phenotype and molecular genetic defects. Platelets are the key molecules mediating haemostasis via adhesion, activation and clot formation at the site of injury. The inherited platelet disorders can be classified according to their platelet defects: receptor/cytoskeleton defects, secretion disorder, and signal transduction defect. Patients with inherited thrombocytopathia present with mucous membrane bleedings (epistaxis, gingival bleeding) and may present with serious life threatening bleedings following surgery or trauma. Therefore, biochemical and molecular genetic characterization of inherited platelet disorders is important to understand these disorders and to support an efficient therapy.

Peripheral Neutrophil Functions and Cell Signalling in Crohn`s Disease

The role of the innate immunity in the pathogenesis of Crohn’s disease (CD), an inflammatory bowel disease, is a subject of increasing interest. Neutrophils (PMN) are key members of the innate immune system which migrate to sites of bacterial infection and initiate the defence against microbes by producing reactive oxygen species (ROS), before undergoing apoptosis. It is believed that impaired innate immune responses contribute to CD, but it is as yet unclear whether intrinsic defects in PMN signal transduction and corresponding function are present in patients with quiescent disease. We isolated peripheral blood PMN from CD patients in remission and healthy controls (HC), and characterised migration, bacterial uptake and killing, ROS production and cell death signalling. Whereas IL8-induced migration and signalling were normal in CD, trans-epithelial migration was significantly impaired. Uptake and killing of E. coli were normal. However, an increased ROS production was observed in CD PMN after stimulation with the bacterial peptide analogue fMLP, which was mirrored by an increased fMLP-triggered ERK and AKT signal activation. Interestingly, cleavage of caspase-3 and caspase-8 during GMCSF-induced rescue from cell-death was decreased in CD neutrophils, but a reduced survival signal emanating from STAT3 and AKT pathways was concomitantly observed, resulting in a similar percentage of end stage apoptotic PMN in CD patients and HC. In toto, these data show a disturbed signal transduction activation and functionality in peripheral blood PMN from patients with quiescent CD, which point toward an intrinsic defect in innate immunity in these patients.

Mentale Retardierung – eine häufige Fragestellung in der medizinischen Genetik

Mental retardation affects about 2-3% of the population and is often associated with comorbidities. So far, more than 450 different medical conditions are known with mental retardation as a sign and it is assumed that there are many more yet to be defined. The diagnosis of the underlying entity allows for a few specific optimization of cognitive function, but usually improves the treatment of comorbidities. Furthermore, the detection of the underlying genetic defect allows the specification of the risk of recurrence and enables prenatal diagnosis for future pregnancies of persons at risk in the family. Recent findings suggest that especially in diseases that are associated with defective synaptic signal transduction may be targeted by specific drugs for improvement of cognitive performance in the near future.

Therapeutic potential of renal sympathetic denervation in patients with chronic heart failure

Chronic heart failure is associated with sympathetic activation characterised by elevated circulating norepinephrine levels linked to cardiovascular morbidity and mortality. Norepinephrine induces phenotype changes of the cardiomyocyte, fibrosis and β-adrenergic signal transduction defects implicated in the dysregulation of contractility. Renal denervation reduces left ventricular hypertrophy and improves diastolic dysfunction, partly blood pressure independently. Also, exercise tolerance and cardiac arrhythmias are positively influenced. Furthermore, there is evidence that common comorbidities like sleep apnoea, metabolic disease and microalbuminuria are improved following renal denervation. The available evidence suggests performing randomised controlled trials to scrutinise whether renal sympathetic denervation might be able to improve morbidity and mortality in chronic heart failure with preserved or reduced ejection fraction.

Characterization of the Complex Regulation of AtALMT1 Expression in Response to Phytohormones and Other Inducers

In Arabidopsis (Arabidopsis thaliana), malate released into the rhizosphere has various roles, such as detoxifying rhizotoxic aluminum (Al) and recruiting beneficial rhizobacteria that induce plant immunity. ALUMINUM-ACTIVATED MALATE TRANSPORTER1 (AtALMT1) is a critical gene in these responses, but its regulatory mechanisms remain unclear. To explore the mechanism of the multiple responses of AtALMT1, we profiled its expression patterns in wild-type plants, in transgenic plants harboring various deleted promoter constructs, and in mutant plants with defects in signal transduction in response to various inducers. AtALMT1 transcription was clearly induced by indole-3-acetic acid (IAA), abscisic acid (ABA), low pH, and hydrogen peroxide, indicating that it was able to respond to multiple signals, while it was not induced by methyl jasmonate and salicylic acid. The IAA-signaling double mutant nonphototropic hypocotyls4-1; auxin-responsive factor19-1 and the ABA-signaling mutant aba insensitive1-1 did not respond to auxin and ABA, respectively, but both showed an Al response comparable to that of the wild type. A synthetic microbe-associated molecular pattern peptide, flagellin22 (flg22), induced AtALMT1 transcription but did not induce the transcription of IAA- and ABA-responsive biomarker genes, indicating that both Al and flg22 responses of AtALMT1 were independent of IAA and ABA signaling. An in planta β-glucuronidase reporter assay identified that the ABA response was regulated by a region upstream (-317 bp) from the first ATG codon, but other stress responses may share critical regulatory element(s) located between -292 and -317 bp. These results illustrate the complex regulation of AtALMT1 expression during the adaptation to abiotic and biotic stresses.

Effect of Bisphenol-A on insulin signal transduction and glucose oxidation in liver of adult male albino rat

Bisphenol-A (BPA) has been classified as an endocrine disruptor which disrupts normal cell function by acting as an estrogen agonist. Environmentally relevant doses of the Bisphenol-A have profound effects on rat endocrine pancreas, an essential organ involved in glucose homeostasis. Bisphenol-A acts on insulin releasing β-cells whereby it increases the pancreatic insulin content and secretion and also favours post prandial hyperinsulinemia and insulin resistance in male mice. Liver plays a central role in the control of glucose production and regulation of insulin secretion. It is one of the primary organs that are initially confronted by damage from toxic substances, xenobiotics and environmental hormones. The present study was designed to assess the effect of Bisphenol-A on insulin signal transduction and glucose oxidation in liver of adult male albino rat. Wistar strain albino rats were selected and divided into three groups, Group-I: Control, Group-II: 20mg BPA treated, Group-III: 200mg BPA treated. The IR (insulin receptor) and Akt (PKB: protein kinase B) mRNA and protein showed a decreased expression pattern in the high dose group. Eventhough there was an increase in serum insulin and a decrease in serum testosterone levels in the high dose group, the fasting blood glucose level remained unaltered. Glucose oxidation and glycogen content were found to be decreased in both high and low dose treated groups. Results of this study suggest that Bisphenol-A treatment impairs hepatic glucose oxidation and glycogen content through defective insulin signal transduction.

Altered APP Processing in Insulin-Resistant Conditions Is Mediated by Autophagosome Accumulation via the Inhibition of Mammalian Target of Rapamycin Pathway

Insulin resistance, one of the major components of type 2 diabetes mellitus (T2DM), is a known risk factor for Alzheimer’s disease (AD), which is characterized by an abnormal accumulation of intra- and extracellular amyloid β peptide (Aβ). Insulin resistance is known to increase Aβ generation, but the underlying mechanism that links insulin resistance to increased Aβ generation is unknown. In this study, we examined the effect of high-fat diet–induced insulin resistance on amyloid precursor protein (APP) processing in mouse brains. We found that the induced insulin resistance promoted Aβ generation in the brain via altered insulin signal transduction, increased β- and γ-secretase activities, and accumulation of autophagosomes. These findings were confirmed in diabetic db/db mice brains. Furthermore, in vitro experiments in insulin-resistant SH-SY5Y cells and primary cortical neurons confirmed the alteration of APP processing by insulin resistance–induced autophagosome accumulation. Defects in insulin signal transduction affect autophagic flux by inhibiting the mammalian target of rapamycin pathway, resulting in altered APP processing in these cell culture systems. Thus, the insulin resistance that underlies the pathogenesis of T2DM might also trigger accumulation of autophagosomes, leading to increased Aβ generation, which might be involved in the pathogenesis of AD.

Baxis Essential for Death Receptor-Mediated Apoptosis in Human Colon Cancer Cells

To demonstrate the role of Bax in death receptor-induced apoptosis in the human colon cancer HCT116 cells. We treated HCT116 cells and HCT116 with p53(-/-) (KO) by 0.1 μg/mL TRAIL for 24 hours, which indicated that HCT116 parental cells are sensitive to p53-independent death receptor-induced apoptosis. Although the p53 signaling pathway is totally intact in this system, the down-regulation of Bax in HCT116 cells is dramatically resistant to TRAIL and failed to undergo apoptosis. However, the over-expression of Bax can rescue the sensitivity of apoptosis induced by the death receptor. Our study has revealed an essential role for Bax in death receptor-induced apoptosis in the human colon cancer HCT116 cells. It may aid in a molecular understanding of possible defects in signal transduction and a regulation of the death receptor-induced apoptotic process.

The mesenchymal stem cell marker CD248 (endosialin) is a negative regulator of bone formation in mice

CD248 (tumor endothelial marker 1/endosialin) is found on stromal cells and is highly expressed during malignancy and inflammation. Studies have shown a reduction in inflammatory arthritis in CD248-knockout (CD248(-/-) ) mice. The aim of the present study was to investigate the functional effect of genetic deletion of CD248 on bone mass. Western blotting, polymerase chain reaction, and immunofluorescence were used to investigate the expression of CD248 in humans and mice. Micro-computed tomography and the 3-point bending test were used to measure bone parameters and mechanical properties of the tibiae of 10-week-old wild-type (WT) or CD248(-/-) mice. Human and mouse primary osteoblasts were cultured in medium containing 10 mM β-glycerophosphate and 50 μg/ml ascorbic acid to induce mineralization, and then treated with platelet-derived growth factor BB (PDGF-BB). The mineral apposition rate in vivo was calculated by identifying newly formed bone via calcein labeling. Expression of CD248 was seen in human and mouse osteoblasts, but not osteoclasts. CD248(-/-) mouse tibiae had higher bone mass and superior mechanical properties (increased load required to cause fracture) compared to WT mice. Primary osteoblasts from CD248(-/-) mice induced increased mineralization in vitro and produced increased bone over 7 days in vivo. There was no decrease in bone mineralization and no increase in proliferation of osteoblasts in response to stimulation with PDGF-BB, which could be attributed to a defect in PDGF signal transduction in the CD248(-/-) mice. There is an unmet clinical need to address rheumatoid arthritis-associated bone loss. Genetic deletion of CD248 in mice results in high bone mass due to increased osteoblast-mediated bone formation, suggesting that targeting CD248 in rheumatoid arthritis may have the effect of increasing bone mass in addition to the previously reported effect of reducing inflammation.

Nerve growth factor and the physiology of pain: lessons from congenital insensitivity to pain with anhidrosis

Congenital insensitivity to pain with anhidrosis (CIPA) is an autosomal recessive genetic disorder characterized by insensitivity to pain, anhidrosis (the inability to sweat) and mental retardation. Nerve growth factor (NGF) is a well-known neurotrophic factor essential for the survival and maintenance of NGF-dependent neurons, including primary afferent neurons with thin fibers and sympathetic postganglionic neurons, during development. NGF is also considered to be an inflammatory mediator associated with pain, itch and inflammation in adults. CIPA results from loss-of-function mutations in the NTRK1 gene-encoding TrkA (tropomyosin-related kinase A), a receptor tyrosine kinase for NGF. Defects in NGF-TrkA signal transduction lead to the failure of survival of various NGF-dependent neurons. As a result, patients with CIPA lack NGF-dependent neurons. Recent studies have revealed that mutations in the NGFB gene-encoding NGF protein also cause congenital insensitivity to pain. Using the pathophysiology of CIPA as a foundation, this review investigates the ways in which NGF-dependent neurons contribute to interoception, homeostasis and emotional responses and, together with the brain, immune and endocrine systems, play crucial roles in pain, itch and inflammation. The NGF-TrkA system is essential for the establishment of neural networks for interoception, homeostasis and emotional responses. These networks mediate reciprocal communication between the brain and the body in humans.

Aktuelles zur diabetischen Makroangiopathie

Current findings from the literature on the multifactorial genesis of macroangiopathy of diabetes mellitus (DM) were compiled using the PubMed database. The primary aim was to find an explanation for the morphological, immunohistochemical and molecular characteristics of this form of atherosclerosis. The roles of advanced glycation end products (AGE), defective signal transduction and imbalance of matrix metalloproteinases in the increased progression of atherosclerosis in coronary and cerebral arteries as well as peripheral vascular disease are discussed. The restricted formation of collateral arteries (arteriogenesis) in diabetic patients with postischemic lesions is also a focus of attention. The increased level of prothrombotic factors and the role of diabetic neuropathy in DM are also taken into account. Therapeutic influences of AGE-RAGE (receptor of AGE) interactions on the vascular wall and the effects of endothelial progenitor cells in the repair of diabetic vascular lesions are additionally highlighted.

The Loss of c-Jun N-Terminal Protein Kinase Activity Prevents the Amyloidogenic Cleavage of Amyloid Precursor Protein and the Formation of Amyloid PlaquesIn Vivo

Phosphorylation plays a central role in the dynamic regulation of the processing of the amyloid precursor protein (APP) and the production of amyloid-β (Aβ), one of the clinically most important factors that determine the onset of Alzheimer's disease (AD). This has led to the hypothesis that aberrant Aβ production associated with AD results from regulatory defects in signal transduction. However, conflicting findings have raised a debate over the identity of the signaling pathway that controls APP metabolism. Here, we demonstrate that activation of the c-Jun N-terminal protein kinase (JNK) is essential for mediating the apoptotic response of neurons to Aβ. Furthermore, we discovered that the functional loss of JNK signaling in neurons significantly decreased the number of amyloid plaques present in the brain of mice carrying familial AD-linked mutant genes. This correlated with a reduction in Aβ production. Biochemical analyses indicate that the phosphorylation of APP at threonine 668 by JNK is required for γ-mediated cleavage of the C-terminal fragment of APP produced by β-secretase. Overall, this study provides genetic evidence that JNK signaling is required for the formation of amyloid plaques in vivo. Therefore, inhibition of increased JNK activity associated with aging or with a pathological condition constitutes a potential strategy for the treatment of AD.

Current perspectives of insulin resistance and polycystic ovary syndrome

To review the relationship between insulin resistance and polycystic ovary syndrome. A literature review. Insulin resistance likely plays a central pathogenic role in polycystic ovary syndrome and may explain the pleiotropic presentation and involvement of multiple organ systems. Insulin resistance in the skeletal muscle of women with polycystic ovary syndrome involves both intrinsic and acquired defects in insulin signalling. The cellular insulin resistance in polycystic ovary syndrome has been further shown to involve a novel post-binding defect in insulin signal transduction. Treatment of insulin resistance through lifestyle therapy or with a diabetes drug has become mainstream therapy in women with polycystic ovary syndrome. However, effects with current pharmacologic treatment with metformin tend to be modest, with limited benefit as an agent to treat infertility. Insulin resistance contributes to increased risk for pregnancy complications, diabetes and cardiovascular disease risk profile in polycystic ovary syndrome, which is further exacerbated by obesity. While numerous studies demonstrate increased prevalence of cardiovascular disease risk factors in women with polycystic ovary syndrome, there are limited data showing that women with polycystic ovary syndrome are at increased risk for cardiovascular disease events. Insulin resistance is linked to polycystic ovary syndrome. Further study of lifestyle and pharmacologic interventions that reduce insulin resistance, such as metformin, are needed to demonstrate that they are effective in reducing the risk of diabetes, endometrial abnormalities and cardiovascular disease events in women with polycystic ovary syndrome.

WNT/β-catenin signaling in polycystic kidney disease

Cystic kidney diseases have been linked to defective WNT signal transduction. Perturbations of cystic disease genes cause activation of canonical WNT/β-catenin/TCF/Lef1 signaling in model organisms and cultured cells. Inappropriate levels of WNT/β-catenin signaling cause renal cyst formation in mice. These observations have prompted the idea that an activation of WNT/β-catenin signaling may constitute a common causative event in cyst formation. Now this view is challenged by key genetic mouse models of cystic kidney disease that do not display WNT/β-catenin activity in cyst-lining epithelia.

Association of IFN-γ Signal Transduction Defects with Impaired HLA Class I Antigen Processing in Melanoma Cell Lines

Abnormalities in the constitutive and IFN-γ-inducible HLA class I surface antigen expression of tumor cells is often associated with an impaired expression of components of the antigen processing machinery (APM). Hence, we analyzed whether there exists a link between the IFN-γ signaling pathway, constitutive HLA class I APM component expression, and IFN-γ resistance. The basal and IFN-γ-inducible expression profiles of HLA class I APM and IFN-γ signal transduction cascade components were assessed in melanoma cells by real-time PCR (RT-PCR), Western blot analysis and/or flow cytometry, the integrity of the Janus activated kinase (JAK) 2 locus by comparative genomic hybridization. JAK2 was transiently overexpressed in JAK2(-) cells. The effect of IFN-γ on the cell growth was assessed by XTT [2,3-bis(2-methoxy-4-nitro-S-sulfophenynl)-H-tetrazolium-5-carboxanilide inner salt] assay. The analysis of 8 melanoma cell lines linked the IFN-γ unresponsiveness of Colo 857 cells determined by lack of inducibility of HLA class I surface expression on IFN-γ treatment to a deletion of JAK2 on chromosome 9, whereas other IFN-γ signaling pathway components were not affected. In addition, the constitutive HLA class I APM component expression levels were significantly reduced in JAK2(-) cells. Furthermore, JAK2-deficient cells were also resistant to the antiproliferative effect of IFN-γ. Transfection of wild-type JAK2 into JAK2(-) Colo 857 not only increased the basal APM expression but also restored their IFN-γ sensitivity. Impaired JAK2 expression in melanoma cells leads to reduced basal expression of MHC class I APM components and impairs their IFN-γ inducibility, suggesting that malfunctional IFN-γ signaling might cause HLA class I abnormalities.

Inhibition Of Cancer Cell Growth By Na/K‐ATPase Mimetic pNaKtide

Cells contain a large pool of non‐pumping Na/K‐ATPase that participates in signal transduction. Here, we show that the surface expression of Na/K‐ATPase is significantly reduced in human prostate carcinoma and cancer cell lines because of increased endocytosis. This down‐regulation impairs the ability of Na/K‐ATPase to regulate key signaling processes. Supplement of the Na/K‐ATPase or pNaKtide, a mimetic peptide derived from Na/K‐ATPase, normalizes the defective signal transduction. Consequently, these treatments stimulates apoptosis, inhibits growth and migration in cultures of cancer cells. Moreover, administration of pNaKtide inhibits angiogenesis and growth of tumor xenograft. Thus, the new findings demonstrate the in vivo effectiveness of pNaKtide, and suggest that the defect in Na/K‐ATPase‐mediated signal transduction may be targeted for developing anti‐cancer therapeutics.