Tyrosine Kinase Antibodies Research Articles

Fatigue in myasthenia gravis: risk factors and impact on quality of life.

ObjectivesEmerging evidence suggests that fatigue in myasthenia gravis (MG) is a relevant problem that negatively impacts activities of daily living (ADL). The relationship between fatigue and quality of life (QoL) has never been systematically explored in MG patients. The study aimed to assess the prevalence of fatigue and its relation to ADL and QoL as well as to identify factors associated with fatigue in MG.Material and MethodsThis was a cross‐sectional observational study in patients with confirmed diagnosis of MG independent of disease severity. Prevalence of fatigue was assessed using the Chalder Fatigue Scale (CFQ). Impact of fatigue on ADL and QoL was assessed by the MG activities of daily living profile (MG‐ADL) and the MG‐specific quality‐of‐life instrument (MG‐QoL), respectively. Association of fatigue with sociodemographics, clinical characteristics of MG, and comorbidities including mood and anxiety disorders as well as sleep disorders was investigated using multivariable logistic regression analyses.ResultsOverall, 200 MG patients were included. The observed rate of fatigue was 56.1%, of those 70.4% fulfilled the criteria of chronic fatigue (CF) with a duration of ≥6 months. Relevant fatigue was strongly associated to ADL and QoL. Factors associated with relevant fatigue were disease severity and depressive state. Furthermore, positive muscle‐specific tyrosine kinase (MuSK) antibody status showed a strong association with relevant fatigue.Conclusions MG patients have a high prevalence of fatigue which negatively impacts ADL and QoL. MG‐specific clinical characteristics are related to fatigue and might help to identify MG patients at risk for fatigue.

Thymolipoma-associated Myasthenia Gravis with High Titer of Anti-MuSKAb: A Case Report.

Myasthenia gravis (MG) is a neuromuscular junction disorder caused by pathogenic autoantibodies to some parts of the post-synaptic muscle endplates. About 85% of generalized MG patients have autoantibodies against post-synaptic acetyl-choline receptors (AChR). From the 10-15% of the remaining patients, 45-50% are positive for Muscle Specific Tyrosine Kinase-Antibody (MuSK-Ab). It is believed that the thymus has a critical role in the pathogenesis of the disease with AChR-Ab, specially in patients with thymic abnormalities. In contrast, the role of thymus gland in MG with anti-MuSK-Ab is not clearly obvious. Patients with this antibody virtually have normal or only minimal follicular hyperplastic thymus. The presence of anti-MuSK Ab in a thymolipomatous (an uncommon tumor of thymus) MG is an atypical and new finding of MG because of not only thymolipoma but the presence of anti-MuSK antibodies which makes this case different from the previous reports of the antibodies-associated MG. Here, we present a young woman with thymolipoma and MG (a very uncommon kind of tumor-associated MG) and high level of anti-MuSK-Ab.

Ocular myasthenia gravis with anti‐muscle‐specific tyrosine kinase antibodies: Two new cases and a systematic literature review

AbstractObjectiveMany myasthenia gravis (MG) patients with anti‐muscle‐specific tyrosine kinase (MuSK) antibodies have prominent oculobulbar symptoms or weaknesses of the neck and respiratory muscles. An ocular form of MG having anti‐MuSK antibodies (MuSK‐OMG) is very rare. We review the clinical features of two such cases.MethodsWe reviewed cases of patients with an ocular form of MG having anti‐MuSK antibodies, including two new cases.ResultsWe found seven published cases, plus two cases described in this report. The mean age at onset of these nine patients was 37.0 ± 17.7 years, and the mean disease duration (from ocular MG onset to report) was 47.0 ± 43.1 months. The clinical courses appeared benign, but heterogeneous. Five of the patients responded to pyridstigmine. Four patients received immunotherapy, which resulted in improvement. Our two patients had mild ocular symptoms. One patient was stable with no immunosuppressive treatment, and the other patient was treated with prednisolone and tacrolimus.ConclusionsCases of an ocular form of MG having anti‐MuSK antibodies do exist. The benign clinical courses and pharmacological responses to cholinesterase inhibitors imply that the antibodies might have different pathogenicities and specificities from those of MuSK‐generalized MG. The presence of anti‐MuSK antibodies should therefore be determined in ocular MG patients negative for anti‐acetylcholine receptor antibodies.

Name a brain protein, and an autoantibody shall be found!

Exciting studies on autoimmune mechanisms of neurologic disorders are leading to the continuous discovery of novel syndromes and autoantibodies of potential clinical utility. Two studies in this issue highlight this discovery process and how findings may be translated into clinical decisions. The first study pertains to the recent discovery of antibodies to cell-adhesion proteins of the nodal and paranodal regions in some patients with chronic inflammatory demyelinating polyneuropathy (CIDP) or Guillain-Barre syndrome. The isotype of these antibodies is usually IgG4, and the target antigens include, among others, contactin-1, neurofascins (NF186 and NF155), and gliomedin, which are important for glial-axonal interactions. Because diseases mediated by antibodies of the IgG4 isotype (such as myasthenia gravis with muscle-specific tyrosine kinase antibodies) often respond to rituximab, Querol et al.1 used a similar approach for 3 patients with severe CIDP and IgG4 antibodies to contactin-1 or NF-155 who were refractory to steroids and IV immunoglobulin (IVIg). Two of the patients had remarkable improvement, and the third showed mild improvement after 10 years of severe disease. As Lancaster and Scherer point out in their editorial, this preliminary observation should encourage determination of whether patients with CIDP who show a poor response to IVIg and steroids have associated IgG4 antibodies. In these cases, B cell–depleting drugs such as rituximab may be effective even after a prolonged course of severe disease.

Identification of the receptor tyrosine kinases (RTKs)-oriented functional targets of miR-206 by an antibody-based protein array

This study demonstrated the feasibility and benefit of an antibody-based experimental approach to identify microRNA functional targets from hundreds of predicted genes using miR-206 as an example. Using a receptor tyrosine kinase (RTK) antibody array, we identified 7 phosphorylated RTKs that were significantly differentially regulated after miR-206-mimic transfection. We then focused on MET, the most varied RTK, and bioinformatically constructed a MET-centred network using computationally predicted miR-206 targets. Within this network, we analyzed two validated targets, PAX3 and SNX2, and one candidate target, EIF4E, may account for the inhibitory effect of miR-206 on MET phosphorylation. Luciferase and Western-blot assays indicated that EIF4E was a direct target of miR-206. This concept may also be applicable for other microRNAs and other antibody array platforms.

Hypoxia enhances cholangiocarcinoma invasion through activation of hepatocyte growth factor receptor and the extracellular signal‑regulated kinase signaling pathway.

Hypoxia is associated with tumor progression and poor prognosis in several cancer types. The present study aimed to examine the contribution of hypoxia (1% O2) to cancer progression in a cholangiocarcinoma cell line, RMCCA-1. The molecular basis of the hypoxic response pathway was investigated. The results showed that hypoxia significantly accelerated cancer cell proliferation and enhanced cell invasion (P<0.05). By using receptor tyrosine kinase and intracellular signaling antibody array kits, an increased phosphorylation/activation of a number of signaling molecules, particularly hepatocyte growth factor receptor (Met) and extracellular signal-regulated kinase (ERK) 1/2, was identified. Inhibition of Met and ERK by small hairpin RNA and U0126, respectively, significantly inhibited hypoxia-induced the invasive potential of RMCCA-1 cells (P<0.05). However, according to immunohistochemical analysis, hypoxia-inducible factor-1α expression was not correlated with cancer staging or tumor differentiation in 44 samples of cholangicarcinoma cases. The findings of the present study emphasized the importance of Met/ERK pathway activation as a key molecular event that may be responsible for a more invasive phenotype in hypoxic tumors and suggest Met as a potential target for the treatment of cholangiocarcinoma.

Regulation of ERBB3/HER3 signaling in cancer.

ERBB3/HER3 is emerging as a molecular target for various cancers. HER3 is overexpressed and activated in a number of cancer types under the conditions of acquired resistance to other HER family therapeutic interventions such as tyrosine kinase inhibitors and antibody therapies. Regulation of the HER3 expression and signaling involves numerous HER3 interacting proteins. These proteins include PI3K, Shc, and E3 ubiquitin ligases NEDD4 and Nrdp1. Furthermore, recent identification of a number of HER3 oncogenic mutations in colon and gastric cancers elucidate the role of HER3 in cancer development. Despite the strong evidence regarding the role of HER3 in cancer, the current understanding of the regulation of HER3 expression and activation requires additional research. Moreover, the lack of biomarkers for HER3-driven cancer poses a big challenge for the clinical development of HER3 targeting antibodies. Therefore, a better understanding of HER3 regulation should improve the strategies to therapeutically target HER3 for cancer therapy.

Investigation of the impact of intravenous injection of mesenchymal stem cells from mouse bone marrow on muscle weakness and immunological parameters in experimental autoimmune myasthenia gravis model

Myasthenia gravis (MG) is a T cell dependent and antibody mediated autoimmune disease. Around 85% of the patients show AChR antibodies, 5% have muscle specific tyrosine kinase (MuSK) antibodies, whereas the remaining patients are seronegative. Although experimental autoimmune myasthenia gravis (EAMG) model has provided important information on MG pathogenesis, treatment strategies are still somewhat limited. In recent years, mesenchymal stem cells from human umbilical cord or blood marrow have been successfully tried in AChR related EAMG model, reducing muscle weakness and AChR reactive lymphocytes.

Abstract 5285: Protein phosphatases modulate kinase signaling mediated Wnt activation

Abstract Multiple growth factors, signaling through their respective kinase cascades, phosphorylate beta-catenin at specific Serine residues to cause its nuclear sequestration thereby fueling Wnt driven tumor cell proliferation. Our present work identifies a group of phosphatase genes that attenuate such growth factor mediated activation of Wnt signaling in colo-rectal cancer (CRC) cells. This proposed mechanism proposes an additional mode of regulation of Wnt activity in CRC cells. Using a lentiviral TCF-LEF reporter system, we isolated distinct SW480 (primary) and SW620 (metastatic) cell fractions based on their endogenous level of Wnt activity. Receptor Tyrosine Kinase (RTK) antibody arrays using cell lysates from these cell fractions identified that FGFR3, ALK and RET signaling pathways have a positive correlation with enhanced Wnt activity. Simultaneously qPCR arrays performed on these same cellular fractions identified a total of 10 phosphatase genes whose expression levels are significantly decreased with heightened Wnt activity, out of which 4 genes PHLPP, PHLPPL, PTPRK and PTPN6 are known to regulate the aforementioned RTK pathways. Of these phosphatase genes, PTPRK has been reported to undergo gene fusion events with RSPO3 (a non-canonical activator of Wnt) in CRC patients. Since the fusion gene product provides no additional Wnt activation that the wild-type RSPO3, we theorized that these fusion events occur either to allow CRC cells to utilize the enhanced promoter activity of the PTPRK gene promoter, or to nullify the Wnt attenuating properties of PTPRK. To test this hypothesis, we have presently cloned and identified PTPRK and RSPO3 gene promoter regions and wish to test their activity in distinct Wnt responsive cell fractions. Our work will allow a better understanding of how phosphatase genes may be involved in controlling the Wnt pathway and how their inactivation may contribute to CRC cell proliferation. Citation Format: Debasish Boral, Daotai Nie. Protein phosphatases modulate kinase signaling mediated Wnt activation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5285. doi:10.1158/1538-7445.AM2014-5285

Myopathy, muscle atrophy and tongue lipid composition in MuSK myasthenia gravis.

Myasthenia gravis (MG) associated with anti-muscle-specific tyrosine kinase (MuSK) antibodies differs in many aspects from typical presentation of acetylcholine receptor (AChR)-positive MG. Myopathy and muscle atrophy are observed in MuSK-positive MG patients, unlike AChR-positive patients with MG. That is why the aim of this study was to assess the presence of myopathy and muscle atrophy as well as the tongue lipid composition in our cohort of MuSK-positive MG patients. Clinical examination, electromyography (EMG) and proton magnetic resonance spectroscopy were performed in 31 MuSK-positive and 28 AChR-positive MG patients. Myopathic EMG was more frequent in MuSK compared to AChR MG patients. In AChR MG patients, myopathic EMG in facial muscles was more frequent after long-term corticosteroid treatment, which was not the case with MuSK-positive MG patients. Facial and/or tongue muscle atrophy was registered in 23 % of MuSK MG patients. Longer disease duration was observed in patients with clinical signs of tongue and/or facial muscle atrophy compared to those with normal tongue muscle. Intramyocellular lipid deposition in the tongue was present in 85.2 % of MuSK and 20 % of AChR MG patients. Female MuSK MG patients had more frequently electrophysiological signs of myopathy on the facial muscles and signs of intramyocellular lipid deposition in the tongue, compared to male patients with MuSK-positive MG. Myopathy, muscle atrophy and intramyocellular lipid deposition in the tongue are more frequent in MuSK-positive compared to AChR-positive MG patients.

Sunitinib suppress neuroblastoma growth through degradation of MYCN and inhibition of angiogenesis.

Neuroblastoma, a tumor of the peripheral sympathetic nervous system, is the most common and deadly extracranial tumor of childhood. The majority of high-risk neuroblastoma exhibit amplification of the MYCN proto-oncogene and increased neoangiogenesis. Both MYCN protein stabilization and angiogenesis are regulated by signaling through receptor tyrosine kinases (RTKs). Therefore, inhibitors of RTKs have a potential as a treatment option for high-risk neuroblastoma. We used receptor tyrosine kinase antibody arrays to profile the activity of membrane-bound RTKs in neuroblastoma and found the multi-RTK inhibitor sunitinib to tailor the activation of RTKs in neuroblastoma cells. Sunitinib inhibited several RTKs and demonstrated potent antitumor activity on neuroblastoma cells, through induction of apoptosis and cell cycle arrest. Treatment with sunitinib decreased MYCN protein levels by inhibition of PI3K/AKT signaling and GSK3β. This effect correlates with a decrease in VEGF secretion in neuroblastoma cells with MYCN amplification. Sunitinib significantly inhibited the growth of established, subcutaneous MYCN-amplified neuroblastoma xenografts in nude mice and demonstrated an anti-angiogenic effect in vivo with a reduction of tumor vasculature and a decrease of MYCN expression. These results suggest that sunitinib should be tested as a treatment option for high risk neuroblastoma patients.

Bone and Stem Cells. The next frontier in allogeneic hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for a majority of hematologic malignancies. However, this treatment procedure can still be associated with significant treatment-related mortality and morbidity, including regimen-related toxicity, graft-versus-host disease, and opportunistic infections. Recently, the advent of molecularly targeted therapy, such as tyrosine kinase inhibitors or antibody drugs, have changed the indications and techniques employed for allogeneic HSCT. In addition, as molecular pathogenesis of a variety of hematologic malignancies has become clear, it has been suggested that mutational profiling can potentially be used for risk stratification and to inform therapeutic decisions regarding patients with hematologic malignancies. Here, we review the knowledge regarding the current status and future directions for allogeneic HSCT in these backgrounds.

Clinical and Electrophysiologic Responses to Acetylcholinesterase Inhibitors in MuSK-Antibody-Positive Myasthenia Gravis: Evidence for Cholinergic Neuromuscular Hyperactivity.

Background and PurposePatients with muscle-specific tyrosine kinase (MuSK) antibody (MuSK-Ab)-positive myasthenia gravis (MG) show distinct responses to acetylcholinesterase inhibitors (AChEIs). Although clinical responses to AChEIs in MuSK-Ab MG are reasonably well known, little is known about the electrophysiologic responses to AChEIs. We therefore investigated the clinical and electrophysiologic responses to AChEIs in MuSK-Ab-positive MG patients.MethodsWe retrospectively reviewed the medical records and electrodiagnostic findings of 17 MG patients (10 MuSK-Ab-positive and 7 MuSK-Ab-negative patients) who underwent electrodiagnostic testing before and after a neostigmine test (NT).ResultsThe frequency of intolerance to pyridostigmine bromide (PB) was higher in MuSK-Ab-positive patients than in MuSK-Ab-negative patients (50% vs. 0%, respectively; p=0.044), while the maximum tolerable dose of PB was lower in the former (90 mg/day vs. 480 mg/day, p=0.023). The frequency of positive NT results was significantly lower in MuSK-Ab-positive patients than in MuSK-Ab-negative patients (40% vs. 100%, p=0.035), while the nicotinic side effects of neostigmine were more frequent in the former (80% vs. 14.3%, p=0.015). Repetitive compound muscle action potentials (R-CMAPs) developed more frequently after NT in MuSK-Ab-positive patients than in MuSK-Ab-negative patients (90% vs. 14.3%, p=0.004). The frequency of a high-frequency-stimulation-induced decrement-increment pattern (DIP) was higher in MuSK-Ab-positive patients than in MuSK-Ab-negative patients (100% vs. 17.7%, p=0.003).ConclusionsThese results suggest that MuSK-Ab-positive MG patients exhibit unique and hyperactive responses to AChEIs. Furthermore, R-CMAP and DIP development on a standard AChEI dose may be a distinct neurophysiologic feature indicative of MuSK-Ab-positive MG.

Critical vocal cord abductor paralysis as an emergency in myasthenia gravis

A 78-year-old woman was admitted for sudden-onset dyspnea, presenting with hypoxemia, stridor and pooling of saliva in the pharynx. One month earlier, she had complained of dysphagia and had been diagnosed with myasthenia gravis (MG) based on weakness of the proximal muscles, decremental response in repetitive nerve stimulation and positive anti-acetylcholine receptor antibodies (Myasthenia Gravis Foundation of America [MGFA] class IIb). Laryngoscopy disclosed severe bilateral vocal cord abductor paralysis (VCAP), which was improved to one-third of the maximum abduction by edrophonium injection (Fig. 1a, b). An emergency tracheostomy was required to avoid suffocation (MGFA class V). Immunosuppressive treatment improved symptoms including VCAP (Fig. 1c). A thymectomy was carried out and the involuted thymus was found. VCAP, a rare complication of MG, can be the first and sole manifestation of the disease.1 VCAP also occurs in patients with anti-muscle-specific receptor tyrosine kinase antibodies.2 When neurologists encounter dyspnea in MG, not only respiratory muscle weakness, but also VCAP should be considered, and indications of tracheostomy must be assessed immediately by laryngoscopy using edrophonium. The authors declare no conflicts of interests with respect to this article.

Myocilin Mediates Myelination in the Peripheral Nervous System through ErbB2/3 Signaling

The glaucoma-associated gene, myocilin, is expressed in ocular and non-ocular tissues including the peripheral nervous system, but its functions in these tissues remain poorly understood. We demonstrate that in sciatic nerve, myocilin is expressed in Schwann cells with high concentrations at the nodes of Ranvier. There, myocilin interacts with gliomedin, neurofascin, and NrCAM, which are essential for node formation and function. Treatment of isolated dorsal root ganglion cultures with myocilin stimulates clustering of the nodal proteins neurofascin and sodium channel Nav1.2. Sciatic nerves of myocilin null mice express reduced levels of several myelin-associated and basal membrane proteins compared with those of wild-type littermates. They also demonstrate reduced myelin sheath thickness and partial disorganization of the nodes. Myocilin signaling through ErbB2/3 receptors may contribute to these observed effects. Myocilin binds to ErbB2/ErbB3, activates these receptors, and affects the downstream PI3K-AKT signaling pathway. These data implicate a role for myocilin in the development and/or maintenance of myelination and nodes of Ranvier in sciatic nerve.

Perioperative Therapeutic Plasmapheresis

Perioperative Therapeutic Plasmapheresis

Myasthenia gravis in South Trinidad.

There is no previous research on Myasthenia Gravis (MG) in Trinidad and Tobago. This study sought to determine the prevalence and to characterize MG in South Trinidad. A cross-sectional study was performed over 30 months in South Trinidad to identify, interview and statistically analyse data on MG cases. Among 36 prevalent patients, female:male ratio was 1.6:1. Estimated MG point prevalence in South Trinidad on March 31, 2010 was 78 per million. Mean age of prevalent patients was 50.5 years. Mean age of onset was 35 years. A higher prevalence was detected in Africans than East Indians (178 vs 68 per million; p = 0.003). Ocular and extremity muscle weakness were the most common initial symptoms. Autoimmune conditions (mainly thyroid disease) co-existed in 25.7%. Treatment involved pyridostigmine and/or immunosuppressants for all except two that went into remission with just steroids. Generalized MG occurred in 60%; 42.9% expressed social and/or professional handicap. One case with suggestive clinical features tested positive for muscle specific tyrosine kinase antibody. While many features of MG in South Trinidad were similar to international data, the unique, statistically significant higher prevalence in Africans than East Indians warrants further research, given the paucity of reports from Africa and India. Patients with MG suffered a diminished quality of life, necessitating improved health planning.

胸腺腫を合併した抗筋特異的受容体チロシンキナーゼ抗体陽性重症筋無力症の1例

We report a 60-year-old male with thymoma-associated myasthenia gravis with anti-MuSK antibodies. In October 2010, he had diplopia, ptosis, and dysphagia. He was diagnosed to have MG in February 2011. The neurological examination disclosed external ophthalmoplegia, bilateral ptosis, mild dysphagia, and fatigability. Repetitive nerve stimulation of the right facial nerve showed CMAP decrement greater than 10%. Patients showed an improvement in ptosis after administration of edrophonium.Anti-acetylcholine receptor antibody was negative, and anti-muscle specific receptor tyrosine kinase antibody was 66.8 nmol/l (cut-off value: 0.05 nmol/l). Prednisolone (50 mg every other day) were started. Contrast-enhanced chest MRI showed a mediastinal mass suggestive of thymoma. Extended thymectomy was performed in March 2011. Histological examination disclosed a type B1 thymoma. After resection of the tumor, the symptoms of MG improved with prednisolone (100 mg every other day). This is a rare case of MG with anti-MuSK antibodies and thymoma, which has been reported previously only in 2 cases.

Regorafenib, the CORRECT way forward or just another GRIDlock?

Studies carried out through the past few decades have increased our understanding of the molecular mechanisms behind colorectal cancer (CRC) and gastrointestinal stromal tumours (GIST). The identification of some of the mutations that drive these types of cancer (such as mutations in KIT or PDGFRA in GIST, and mutations in KRAS in CRC) has allowed the development of tyrosine kinase inhibitors (TKI) and antibodies that have provided numerous treatment options improving considerably the clinical outcomes of patients with these malignancies.

Antibodies against Wnt receptor of muscle-specific tyrosine kinase in myasthenia gravis

Muscle-specific tyrosine kinase (MuSK) antibodies are detected in a proportion of myasthenia gravis (MG) patients who are negative for acetylcholine receptor (AChR) antibodies and have prominent bulbar weakness and crises. In the MuSK ectodomains, the immunoglobulin-like 1 and 2 domains (Ig1/2) mediate the agrin–Lrp4–MuSK signaling and the cysteine-rich domain (CRD) mediates the Wnt–MuSK–Dishevelled signaling; both contribute to AChR clustering. Immunoblotting against recombinant proteins showed MuSK Ig1/2 antibodies in 33 anti-AChR-negative MG patients; 10 patients of them (30%) were additionally positive for MuSK CRD antibodies. The result suggests that MuSK antibodies have heterogeneity in their binding to functional domains of MuSK.