Neuroimmunology of the paraneoplastic neurological degenerations

Prediction of Seropositivity in Suspected Autoimmune Encephalitis by Use of Radiomics: A Radiological Proof-of-Concept Study

In this study, we sought to evaluate the capabilities of radiomics and machine learning in predicting seropositivity in patients with suspected autoimmune encephalitis (AE) from MR images obtained at symptom onset. In 83 patients diagnosed with AE between 2011 and 2022, manual bilateral segmentation of the amygdala was performed on pre-contrast T2 images using 3D Slicer open-source software. Our sample of 83 patients contained 43 seropositive and 40 seronegative AE cases. Images were obtained at our tertiary care center and at various secondary care centers in North Rhine-Westphalia, Germany. The sample was randomly split into training data and independent test data. A total of 107 radiomic features were extracted from bilateral regions of interest (ROIs). Automated machine learning (AutoML) was used to identify the most promising machine learning algorithms. Feature selection was performed using recursive feature elimination (RFE) and based on the determination of the most important features. Selected features were used to train various machine learning algorithms on 100 different data partitions. Performance was subsequently evaluated on independent test data. Our radiomics approach was able to predict the presence of autoantibodies in the independent test samples with a mean AUC of 0.90, a mean accuracy of 0.83, a mean sensitivity of 0.84 and a mean specificity of 0.82, with Lasso regression models yielding the most promising results. These results indicate that radiomics-based machine learning could be a promising tool in predicting the presence of autoantibodies in suspected AE patients. Given the implications of seropositivity for definitive diagnosis of suspected AE cases, this may expedite diagnostic workup even before results from specialized laboratory testing can be obtained. Furthermore, in conjunction with recent publications, our results indicate that characterization of AE subtypes by use of radiomics may become possible in the future, potentially allowing physicians to tailor treatment in the spirit of personalized medicine even before laboratory workup is completed.

NOVA1 acts as an oncogenic RNA-binding protein to regulate cholesterol homeostasis in human glioblastoma cells

NOVA1 is a neuronal RNA-binding protein identified as the target antigen of a rare autoimmune disorder associated with cancer and neurological symptoms, termed paraneoplastic opsoclonus-myoclonus ataxia. Despite the strong association between NOVA1 and cancer, it has been unclear how NOVA1 function might contribute to cancer biology. In this study, we find that NOVA1 acts as an oncogenic factor in a GBM (glioblastoma multiforme) cell line established from a patient. Interestingly, NOVA1 and Argonaute (AGO) CLIP identified common 3' untranslated region (UTR) targets, which were down-regulated in NOVA1 knockdown GBM cells, indicating a transcriptome-wide intersection of NOVA1 and AGO-microRNA (miRNA) targets regulation. NOVA1 binding to 3'UTR targets stabilized transcripts including those encoding cholesterol homeostasis related proteins. Selective inhibition of NOVA1-RNA interactions with antisense oligonucleotides disrupted GBM cancer cell fitness. The precision of our GBM CLIP studies point to both mechanism and precise RNA sequence sites to selectively inhibit oncogenic NOVA1-RNA interactions. Taken together, we find that NOVA1 is commonly overexpressed in GBM, where it can antagonize AGO2-miRNA actions and consequently up-regulates cholesterol synthesis, promoting cell viability.

Seronegative paraneoplastic encephalomyelitis in occult colonic carcinoma

Paraneoplastic neurological syndromes are immune-mediated neurological attacks triggered by malignancies. They are commonly associated with lung, breast, thymus, gynaecological and haematological malignancies. We report a case of a male patient in his late 40s with paraneoplastic encephalomyelitis due to a colonic adenocarcinoma emphasising a low threshold for extensive cancer evaluation in all subacutely presenting neurological syndromes. We also emphasise that the absence of a positive onconeural antibody does not preclude the diagnosis of a paraneoplastic syndrome.

Epilepsy, Immunity and Neuropsychiatric Disorders

Several studies have focused on the emerging role of immunity and inflammation in a wide range of neurological disorders. Autoimmune diseases involving central nervous system share well defined clinical features including epileptic seizures and additional neuropsychiatric symptoms, like cognitive and psychiatric disturbances. The growing evidence about the role of immunity in the pathophysiologic mechanisms underlying these conditions lead to the concept of autoimmune epilepsy. This relatively-new term has been introduced to highlight the etiological and prognostic implications of immunity in epileptogenesis. In this review, we aim to discuss the role of autoimmunity in epileptogenesis and its clinical, neurophysiological, neuroimaging and therapeutic implications. Moreover, we wish to address the close relationship between immunity and additional symptoms, particularly cognitive and psychiatric features, which deeply impact clinical outcomes in these patients. To assess these aspects, we first analyzed Rasmussen's encephalitis. Subsequently, we have covered autoimmune encephalitis, particularly those associated with autoantibodies against surface neuronal antigens, as these autoantibodies express a direct immune-mediated mechanism, different from those against intracellular antigens. Then, we discussed the connection between systemic immune disorders and neurological manifestations. This review aims to highlight the need to expand knowledge about the role of inflammation and autoimmunity in the pathophysiology of neurological disorders and the importance to early recognize these clinical entities. Indeed, early identification may result in faster recovery and a better prognosis.

Opsoclonus-myoclonus syndrome associated with neuroblastoma: Insights into antitumor immunity

Opsoclonus-myoclonus syndrome (OMS) is a rare neurological disorder. Half of these cases occur in children with neuroblastoma. Neuroblastoma patients with OMS usually have better oncological outcomes than those without OMS even after stratification by tumor stage and age, indicating that factors mediating OMS may also inhibit tumor cell proliferation. Although the mechanisms underlying OMS remain undefined, the cytokines and lymphocytes alterations in the cerebrospinal fluid support the concept that it is a pattern of neuroinflammation due to an autoimmune effect. The presence of lymphoid follicles consisting of follicular dendritic cells, CD20⁺ B lymphocytes, CD3⁺ T lymphocytes, and CD68⁺ macrophages in the tumor microenvironment in OMS-associated neuroblastoma support the autoimmune nature of this disorder. This review focuses on the clinical and genetic features of OMS-associated neuroblastoma, and we update readers on immune features of neuroblastoma with or without OMS to gain insights into antitumor immunity as it relates to tumor biology and prognosis.

A scoping review on paraneoplastic autoimmune limbic encephalitis (PALE) psychiatric manifestations

The term limbic encephalitis has been used with an oncological precedent for over 50 years and, since then, has been applied in relation to multiple antibodies found in its etiological process. Over the last decade, the psychiatric community has brought paraneoplastic autoimmune limbic encephalitis (PALE) to a new light, scattering the once known relationships between said screened antibodies responsible for causing limbic encephalitis. Due to the fact that some individuals with this condition have a psychiatric syndrome as an initial manifestation, the aim of this updated scoping review is to reestablish a causal relationship between the onconeuronal autoantibodies, both intracellular and extracellular, possible underlying malignancies and subsequent neuropsychiatric syndrome. In pair with it, there is the idea of sketching a cleaner thorough picture of what poses as psychiatric symptoms as well as possible therapeutics. Even though the always evolving epistemology of the neurosciences achieved a significant unveiling of what includes PALE in its relevant pathological subgroups, the amount of gray literature still is much superior, appealing to a further research with more randomized controlled trials, with larger populations, so that the results corroborate the small amount of data that already exist and posteriorly be applied in the general population.

A Breakdown of Immune Tolerance in the Cerebellum

Cerebellar dysfunction can be associated with ataxia, dysarthria, dysmetria, nystagmus and cognitive deficits. While cerebellar dysfunction can be caused by vascular, traumatic, metabolic, genetic, inflammatory, infectious, and neoplastic events, the cerebellum is also a frequent target of autoimmune attacks. The underlying cause for this vulnerability is unclear, but it may be a result of region-specific differences in blood–brain barrier permeability, the high concentration of neurons in the cerebellum and the presence of autoantigens on Purkinje cells. An autoimmune response targeting the cerebellum—or any structure in the CNS—is typically accompanied by an influx of peripheral immune cells to the brain. Under healthy conditions, the brain is protected from the periphery by the blood–brain barrier, blood–CSF barrier, and blood–leptomeningeal barrier. Entry of immune cells to the brain for immune surveillance occurs only at the blood-CSF barrier and is strictly controlled. A breakdown in the barrier permeability allows peripheral immune cells uncontrolled access to the CNS. Often—particularly in infectious diseases—the autoimmune response develops because of molecular mimicry between the trigger and a host protein. In this review, we discuss the immune surveillance of the CNS in health and disease and also discuss specific examples of autoimmunity affecting the cerebellum.

Paraneoplastic cerebellar degeneration: Yo antibody alters mitochondrial calcium buffering capacity

Aim

Neurodegeneration is associated with dysfunction of calcium buffering capacity and thereby sustained cellular and mitochondrial calcium overload. Paraneoplastic cerebellar degeneration (PCD), characterized by progressive Purkinje neurone degeneration following paraneoplastic Yo antibody internalization and binding to cerebellar degeneration‐related protein CDR2 and CDR2L, has been linked to intracellular calcium homeostasis imbalance due to calbindin D_28k malfunction. Therefore, we hypothesized that Yo antibody internalization affects not only calbindin calcium binding capacity, but also calcium‐sensitive mitochondrial‐associated signalling, causing mitochondrial calcium overload and thereby Purkinje neurone death.

Methods

Immunohistochemically, we evaluated cerebellar organotypic slice cultures of rat brains after inducing PCD through the application of Yo antibody‐positive PCD patient sera or purified antibodies against CDR2 and CDR2L how pharmacologically biased mitochondrial signalling affected PCD pathology.

Results

We found that Yo antibody internalization into Purkinje neurons caused depletion of Purkinje neurone calbindin‐immunoreactivity, cannabinoid 1 receptor over‐activation and alterations in the actions of the mitochondria permeability transition pore (MPTP), voltage‐dependent anion channels, reactive oxygen species (ROS) and Na⁺/Ca²⁺ exchangers (NCX). The pathological mechanisms caused by Yo antibody binding to CDR2 or CDR2L differed between the two targets. Yo‐CDR2 binding did not alter the mitochondrial calcium retention capacity, cyclophilin D‐independent opening of MPTP or activity of NCX.

Conclusion

These findings suggest that minimizing intracellular calcium overload toxicity either directly with cyclosporin‐A or indirectly with cannabidiol or the ROS scavenger butylated hydroxytoluene promotes mitochondrial calcium homeostasis and may therefore be used as future neuroprotective therapy for PCD patients.

Thymoma Associated with Myasthenia and Autonomic anti-Hu Paraneoplastic Neuropathy

Along with myasthenia, other paraneoplastic neurological syndromes (PNS) may occur in thymoma. Anti-Hu antibodies and a clinical “anti-Hu syndrome” characterized by encephalitis and/or painful neuropathies have been reported in only three patients at the time of the diagnosis of thymoma. We describe a severe anti-Hu-related autonomic neuropathy with gastrointestinal paresis and intestinal pseudo-obstruction with malabsorption that occurred concomitantly with the worsening of myasthenic symptoms long after the initial diagnosis of thymoma in a young patient. The clinical anti-Hu syndrome preceded the radiological diagnosis of thymoma recurrence. Treatment with plasma exchange led to a transient improvement of neurological symptoms.

Clinicopathological features of neuroblastic tumors with opsoclonus-myoclonus-ataxia syndrome: Follicular structure predicts a better neurological outcome

Neuroblastic tumors (NT) with opsoclonus-myoclonus syndrome (OMS) display characteristic histological features, such as lymphocytic infiltration with lymphoid follicles, indicating an underlying immune response. We retrospectively assessed NT patients from 2001 to 2016. Five cases of NT with OMS and 76 cases of NT without OMS were histopathologically reviewed in this study. The grade of lymphocytic infiltration was evaluated. The number of follicles was counted and the presence or absence of lymphoid follicles was recorded for each case. We also confirmed the presence or absence of follicular dendritic cells (FDCs). We investigated the relationship between the histopathological and clinical findings of NT with OMS. Lymphocytic infiltration was observed in all cases; however, the precise follicular structure was occasionally unclear. Patients with clear follicular structures displayed germinal centers including tingible body macrophages and FDCs. All patients without neurological sequelae demonstrated a clear follicular structure with a FDC meshwork pattern. The interval between OMS onset and the detection and initial treatment of NT was typically longer in patients with neurological sequelae compared to those without neurological sequelae. Early detection and treatment of NT with OMS at the phase of a clear follicular formation with multiple FDC may provide favorable neurological outcomes.

Detection of brain-directed autoantibodies in the serum of non-small cell lung cancer patients

Antibodies against brain proteins were identified in the plasma of cancer patients and are defined to cause paraneoplastic neurological syndromes. The profiles of brain-directed antibodies in non-small cell lung cancer (NSCLC) are largely unknown. Here, for the first time, we compared autoantibodies against brain proteins in NSCLC (n = 18) against those present in age-matched non-cancer control subjects (n = 18) with a similar life-style, habit, and medical history. Self-recognizing immunoglobulin (IgG) are primarily directed against cells in the cortex (P = 0.008), hippocampus (P = 0.003–0.05), and cerebellum (P = 0.02). More specifically, IgG targets were prominent in the pyramidal, Purkinje, and granule cell layers. Furthermore, autoimmune IgG signals were localized to neurons (81%), astrocytes (48%), and endothelial (29%) cells. While cancer sera yielded overall higher intensity signals, autoantigens of 100, 65, 45, 37, and 30 kDa molecular weights were the most represented. Additionally, a group of 100 kDa proteins seem more prevalent in female adenocarcinoma patients (4/5, 80%). In conclusion, our results revealed autoantigen specificity in NSCLC, which implicitly depends on patient’s demographics and disease history. Patients at risk for lung cancer but with no active disease revealed that the immune profile in NSCLC is disease-dependent.

Paraneoplastic epilepsy

Epilepsy can be a manifestation of paraneoplastic syndromes which are the consequence of an immune reaction to neuronal elements driven by an underlying malignancy affecting other organs and tissues. The antibodies commonly found in paraneoplastic encephalitis can be divided into two main groups depending on the target antigen: 1) antibodies against neuronal cell surface antigens, such as against neurotransmitter (N-methyl-d-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), gamma-aminobutyric acid (GABA)) receptors, ion channels (voltage-gated potassium channel (VGKC)), and channel-complex proteins (leucine rich, glioma inactivated-1 glycoprotein (LGI1) and contactin-associated protein-2 (CASPR2)) and 2) antibodies against intracellular neuronal antigens (Hu/antineuronal nuclear antibody-1 (ANNA-1), Ma2/Ta, glutamate decarboxylase 65 (GAD65), less frequently to CV2/collapsin response mediator protein 5 (CRMP5)). In this review, we provide a comprehensive survey of the current literature on paraneoplastic epilepsy indexed by the associated onconeuronal antibodies. While a range of seizure types can be seen with paraneoplastic syndromes, temporal lobe epilepsy is the most common because of the association with limbic encephalitis. Early treatment of the paraneoplastic syndrome with immune modulation/suppression may prevent the more serious potential consequences of paraneoplastic epilepsy.

Proteolytic degradation and potential role of onconeural protein cdr2 in neurodegeneration

Cerebellar degeneration-related protein 2 (cdr2) is expressed in the central nervous system, and its ectopic expression in tumor cells of patients with gynecological malignancies elicits immune responses by cdr2-specific autoantibodies and T lymphocytes, leading to neurological symptoms. However, little is known about the regulation and function of cdr2 in neurodegenerative diseases. Because we found that cdr2 is highly expressed in the midbrain, we investigated the role of cdr2 in experimental models of Parkinson's disease (PD). We found that cdr2 levels were significantly reduced after stereotaxic injection of 1-methyl-4-phenylpyridinium (MPP(+)) into the striatum. cdr2 levels were also decreased in the brains of post-mortem PD patients. Using primary cultures of mesencephalic neurons and MN9D cells, we confirmed that MPP(+) reduces cdr2 in tyrosine hydroxylase-positive dopaminergic neuronal cells. The MPP(+)-induced decrease of cdr2 was primarily caused by calpain- and ubiquitin proteasome system-mediated degradation, and cotreatment with pharmacological inhibitors of these enzymes or overexpression of calcium-binding protein rendered cells less vulnerable to MPP(+)-mediated cytotoxicity. Consequently, overexpression of cdr2 rescued cells from MPP(+)-induced cytotoxicity, whereas knockdown of cdr2 accelerated toxicity. Collectively, our findings provide insights into the novel regulatory mechanism and potentially protective role of onconeural protein during dopaminergic neurodegeneration.

PNMA2 mediates heterodimeric interactions and antagonizes chemo-sensitizing activities mediated by members of PNMA family

PNMA2, a member of the Paraneoplastic Ma Family (PNMA), was identified through expression cloning by using anti-sera from patients with paraneoplastic disorder. Tissue expression studies showed that PNMA2 was predominantly expressed in normal human brain; however, the protein was shown to exhibit abnormal expression profile as it was found to be expressed in a number of tumour tissues obtained from paraneopalstic patients. The abnormal expression profile of PNMA2 suggests that it might play an important role in tumorigenesis; however, apart from protein expression and immunological studies, the physiological role of PNMA2 remains unclear. In order to determine potential role of PNMA2 in tumorigenesis, and its functional relationship with PNMA family members, MOAP-1 (PNMA4) and PNMA1, expression constructs encoding the respective proteins were generated for both in vitro and in vivo studies. Our investigations showed that over-expressed MOAP-1 and PNMA1 promoted apoptosis and chemo-sensitization in MCF-7 cells as evidenced by condensed nuclei and Annexin-V positive MCF-7 cells; however, the effects mediated by these proteins were significantly inhibited or abolished when co-expressed with PNMA2 in MCF-7 cells. Furthermore, co-immunoprecipitation study showed that PNMA1 and MOAP-1 failed to associate with each other but readily formed respective heterodimer with PNMA2, suggesting that PNMA2 functions as antagonist of MOAP-1 and PNMA1 through heterodimeric interaction.

A destructive feedback loop mediated by CXCL10 in central nervous system inflammatory disease

Objective

Paraneoplastic neurologic disorders (PND) are autoimmune diseases associated with cancer and ectopic expression of a neuronal antigen in a peripheral tumor. Patients with PND harbor high‐titer antibodies and T cells in their serum and cerebrospinal fluid (CSF) that are specific to the tumor antigen, and treatment with the immunosuppressant FK506 (tacrolimus) decreases CSF white blood cell counts. The objective of this study was to determine the effect of FK506 on CSF chemokine levels in PND patients.

Methods

CSF samples before and after FK506 treatment were tested by multiplex assay for the presence of 27 cytokines. Follow‐up in vitro experiments aimed to determine whether T cells secrete CXCL10 in response to cognate antigen.

Results

Here we report that PND patients harbor high levels of the chemokine CXCL10 in their CSF. CXCL10 is a cytokine that recruits CXCR3⁺ cells such as activated T cells, and we found that FK506 treatment specifically decreased CSF CXCL10 from among 27 cytokines tested. In vitro, CXCL10 was only produced during antigen‐specific cognate interactions between T cells and antigen‐presenting cells (APCs) when interferon‐γ (IFNγ) receptors were present on the T cell.

Interpretation

These results support a model in which antigen‐specific T cell stimulation by PND APCs triggers IFNγ, followed by CXCL10 production and further lymphocyte recruitment, suggesting that treatments targeting T cells or CXCL10 in the central nervous system (CNS) may interrupt a destructive positive feedback loop present in CNS inflammation. Ann Neurol 2015;78:619–629

Paving the Way to Understand Autoantibody-Mediated Epilepsy on the Molecular Level

Correct function of neuronal networks is enabled by a delicate interplay among neurons communicating with each other. One of the keys is the communication at chemical synapses where neurotransmitters like glutamate, GABA, and glycine enable signal transfer over the synaptic cleft. Thereby, the neurotransmitters are released from the presynapse and bind as ligands to specific receptors at the postsynaptic side to allow for modulation of the postsynaptic membrane potentials. The postsynaptic electrical signal, which is highly modulated by voltage-gated ion channels, spreads over the dendritic tree and is thus integrated to allow for generation of action potentials at the axon hillock. This concert of receptors and voltage-gated ion channels depends on correct function of all its components. Misfunction of receptors and/or voltage-gated potassium channels (VGKC) leads to diverse adverse effects in patients. Such malfunctions can be the result of inherited genetic alterations or pharmacological side effects by drugs. Recently, autoantibodies targeting receptor or channel complexes like NMDAR, AMPAR, GABA-receptors, glycine receptors, LGI1 or CASPR2 (previously termed as VGKC-complex antibodies) have been discovered. The presence of specific autoantibodies against these targets associates with severe forms of antibody-mediated encephalitis. Understanding the molecular details of autoantibody actions on receptor and VGKC complexes is highly desirable and may open the path to develop specific therapies to treat humoral autoimmune encephalitis. Here, we summarize the current knowledge and discuss technical approaches to fill the gap of knowledge. These techniques include electrophysiology, biochemical approaches for epitope mapping, and in silico modeling to simulate molecular interactions between autoantibody and its molecular target.

Paraneoplastic CDR2 and CDR2L antibodies affect Purkinje cell calcium homeostasis

Paraneoplastic cerebellar degeneration (PCD) is characterized by loss of Purkinje cells (PCs) associated with progressive pancerebellar dysfunction in the presence of onconeural Yo antibodies. These antibodies recognize the cerebellar degeneration-related antigens CDR2 and CDR2L. Response to PCD therapy is disappointing due to limited understanding of the neuropathological mechanisms. Here, we report the pathological role of CDR antibodies on the calcium homeostasis in PCs. We developed an antibody-mediated PCD model based on co-incubation of cerebellar organotypic slice culture with human patient serum or rabbit CDR2 and CDR2L antibodies. The CDR antibody-induced pathology was investigated by high-resolution multiphoton imaging and biochemical analysis. Both human and rabbit CDR antibodies were rapidly internalized by PCs and led to reduced immunoreactivity of calbindin D_28K (CB) and L7/Pcp-2 as well as reduced dendritic arborizations in the remaining PCs. Washout of the CDR antibodies partially recovered CB immunoreactivity, suggesting a transient structural change in CB calcium-binding site. We discovered that CDR2 and CB co-immunoprecipitate. Furthermore, the expression levels of voltage-gated calcium channel Cav2.1, protein kinase C gamma and calcium-dependent protease, calpain-2, were increased after CDR antibody internalization. Inhibition of these signaling pathways prevented or attenuated CDR antibody-induced CB and L7/Pcp-2 immunoreactivity loss, morphological changes and increased protein expression. These results signify that CDR antibody internalization causes dysregulation of cell calcium homeostasis. Hence, drugs that modulate these events may represent novel neuroprotective therapies that limit the damaging effects of CDR antibodies and prevent PC neurodegeneration.

Imbalance in circulating T lymphocyte subsets contributes to Hu antibody-associated paraneoplastic neurological syndromes

Paraneoplastic neurological syndromes (PNS) are associated with small cell lung cancer (SCLC) and Hu antibodies, which are considered to have an immune-mediated etiology. As a pathogenic role for Hu antibodies (Hu-Ab) in PNS could not be demonstrated, the cellular immune response against the Hu proteins has been further investigated. To delve deeper into the hypothesized cell-mediated immune pathogenesis of these syndromes, imbalances within circulating T lymphocyte subsets were investigated to determine their significance in Hu antibody-associated PNS. The circulating T lymphocyte subsets were analyzed in untreated patients with SCLC, PNS and Hu-Ab (n=10), SCLC without PNS (n=10) and healthy controls (n=12) using flow cytometry. Patients with PNS and SCLC, had a variety of changes within their circulating T lymphocyte subsets, which included; lymphopenia of the CD3(+)and CD4(+) T cells, increased proportions of total activated T cells and activated CD4(+) T cells, and reduced numbers of CD4(+) and CD25(+) regulatory T cells (Treg). These results suggest that the excessive activation of T cells and dysfunction of Treg contribute to Hu antibody-associated PNS.

A prospective open-label study of sirolimus for the treatment of anti-Hu associated paraneoplastic neurological syndromes

BACKGROUND

Several lines of evidence suggest a T cell-mediated immune response in paraneoplastic neurological syndromes with anti-Hu antibodies (Hu-PNS). In order to investigate whether suppression of T cell-mediated immune responses in Hu-PNS patients improved their neurological outcome, we performed a prospective open-label, single-arm study on sirolimus.

METHODS

Seventeen progressive Hu-PNS patients were treated with sirolimus with an intended treatment duration of 8 weeks. Primary outcome measures were (i) functional improvement, defined as a decrease of one or more points on the modified Rankin Scale (mRS), and (ii) improvement of neurological impairment, defined as an increase of one or more points on the Edinburgh Functional Impairment Tests (EFIT).

RESULTS

One patient showed improvement on both clinical scales (mRS and EFIT). This patient presented with limbic encephalitis and improved dramatically from an mRS score of 3 to mRS 1. Another patient, with subacute sensory neuronopathy, remained stable at mRS 2 and improved one point on the EFIT scale. The other patients showed no improvement on the primary outcome measures. Median survival was 21 months.

CONCLUSION

We conclude that treatment of Hu-PNS patients with sirolimus may improve or stabilize their functional disabilities and neurological impairments. However, the effects of this T cell-targeted therapy were not better than reported in trials on other immunotherapies for Hu-PNS. Trial Registration https://www.clinicaltrialsregister.eu/ctr-search/trial/2008-000793-20/NL.

Paraneoplastic neuropathies

PURPOSE OF REVIEW

This review describes relevant advances in paraneoplastic neuropathies with emphasis on particular syndromes and the impact of new therapies.

RECENT FINDINGS

Sensory neuronopathy may present with symptoms that do not raise the suspicion of a paraneoplastic origin. A recent study on sensory neuronopathies of different causes identified paraneoplastic cases in a group of older (>60 years) male patients with subacute onset early pain, and frequent involvement of the arms. Paraneoplastic sensorimotor polyneuropathies may be confused with chronic inflammatory demyelinating polyneuropathy (CIDP) and in lymphomas with direct infiltration of nerves (neurolymphomatosis). Recent neurophysiological studies indicate that the polyneuropathy of POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M component, and skin changes) can be differentiated from CIDP by the presence of diffuse demyelination and more severe axonal loss. Neuropathy in Waldenström macroglobulinemia is heterogeneous. Up to 38% have demyelinating features and the rest show axonal degeneration due to different causes (dysimmune, amyloidosis, or tumoral infiltration). Isolated case reports suggest that the combination of cyclophosphamide and rituximab may be effective in paraneoplastic neuronopathies. Lenalidomide and dexamethasone are effective to control the neuropathy of POEMS patients who are not suitable for or progress after autologous stem cell transplantation.

SUMMARY

Clinical and neurophysiological studies are helpful to correctly identify particular paraneoplastic neuropathies.

Neurologic complications of lung cancer

Neurologic complications of lung cancer are a frequent cause of morbidity and mortality. Tumor metastasis to the brain parenchyma is the single most common neurologic complication of lung cancer, of any histologic subtype. The goal of radiation therapy and in some cases surgical resection for patients with brain metastases is to improve or maintain neurologic function, and to achieve local control of the brain lesion(s). Metastasis of lung cancer to the spinal epidural space requires urgent evaluation and treatment. Early diagnosis and modern surgical and radiotherapy techniques improve neurologic outcome for most patients. Leptomeningeal metastasis is a less common but ominous occurrence in patients with lung cancer. Lung carcinomas can also occasionally metastasize to the brachial plexus, skull base, dura, or pituitary. Paraneoplastic neurologic disorders are uncommon but important complications of lung carcinoma, and are generally the presenting feature of the tumor. Paraneoplastic disorders are believed to be caused by an autoimmune humoral or cellular attack against shared "onconeural" antigens. The most frequent paraneoplastic disorders in patients with lung cancer are Lambert-Eaton myasthenic syndrome, and multifocal paraneoplastic encephalomyelitis, both mainly occurring in association with small-cell lung carcinoma. There is a variety of other paraneoplastic disorders affecting the central and peripheral nervous systems. Some affected patients have a good neurologic outcome, while others are left with severe permanent neurologic disability.

Elevated numbers of regulatory T cells, central memory T cells and class-switched B cells in cerebrospinal fluid of patients with anti-Hu antibody associated paraneoplastic neurological syndromes

Multi-parametric flow cytometry was used to study lymphocyte subsets and dendritic cells in paired blood and CSF samples from 11 newly diagnosed patients with progressive anti-Hu antibody associated paraneoplastic neurological syndromes (Hu-PNS), 9 patients with other inflammatory neurologic disorders (IND), and 12 patients with other non-inflammatory neurologic disorders (OND). Hu-PNS patients had elevated numbers of regulatory T cells, central memory T cells, class-switched B cells and dendritic cells in their CSF. These findings support the hypothesis that the immune system is locally activated in Hu-PNS, and suggests common etiological pathways between Hu-PNS and other inflammatory central nervous system disorders.

The diagnosis and treatment of limbic encephalitis

The term limbic encephalitis (LE) was first introduced in 1968. While this disease was initially considered rare and is often fatal with very few treatment options, several reports published in the last decade provide a better description of this condition as well as possible causes and some cases of successful treatment. The clinical manifestation of LE is primarily defined by the subacute onset of short-term memory loss, seizures, confusion and psychiatric symptoms suggesting the involvement of the limbic system. In addition, EEG often shows focal or generalized slow wave or epileptiform activity, and MRI findings reveal hyperintense signals of the medial temporal lobes in T2-weighted or FLAIR images. The current literature suggests that LE is not a single disorder but is comprised of a group of autoimmune disorders predominantly affecting the limbic system. Before the diagnosis of LE can be determined, other causes of subacute encephalopathy must be excluded, especially those resulting from infectious aetiologies. LE has previously been regarded as a paraneoplastic phenomenon associated with the classical onconeuronal antibodies that are primarily directed against intracellular antigens. However, recent literature suggests that LE is also associated with antibodies that are directed against cell surface antigens, and these cases of LE display a much weaker association to the neoplasm. The treatment options for LE largely depend on the aetiology of the disease and involve the removal of the primary neoplasm. Therefore, a search for the underlying tumour is mandatory. In addition, immunotherapy has been successful in a significant number of patients where LE is not associated with cancer.

Modulator of Apoptosis 1: A Highly Regulated RASSF1A-Interacting BH3-Like Protein

Modulator of apoptosis 1 (MOAP-1) is a BH3-like protein that plays key roles in both the intrinsic and extrinsic modes of cell death or apoptosis. MOAP-1 is part of the Ras association domain family 1A (RASSF1A)/MOAP-1 pro-apoptotic extrinsic signaling pathway that regulates apoptosis by utilizing death receptors such as tumor necrosis factor α (TNFα) or TNF-related apoptosis-inducing ligand (TRAIL) to inhibit abnormal growth. RASSF1A is a bona fide tumor suppressor gene that is epigenetically silenced by promoter-specific methylation in numerous human cancers. MOAP-1 is a downstream effector of RASSF1A that promotes Bax activation and cell death and is highly regulated during apoptosis. We speculate that MOAP-1 and RASSF1A are important elements of an “apoptotic checkpoint” that directly influences the outcome of cell death. The failure to regulate this pro-apoptotic pathway may result in the appearance of cancer and possibly other disorders. Although loss of RASSF1A expression is frequently observed in human cancers, it is currently unknown if MOAP-1 expression may also be affected during carcinogenesis to result in uncontrolled malignant growth. In this article, we will summarize what is known about the biological role(s) of MOAP-1 and how it functions as a downstream effector to RASSF1A.

Three sensitive assays do not provide evidence for circulating HuD-specific T cells in the blood of patients with paraneoplastic neurological syndromes with anti-Hu antibodies

Anti-Hu antibody-associated paraneoplastic neurological syndromes (Hu-PNSs) are severe and often precede the detection of a malignancy, usually small-cell lung cancer. In Hu-PNS, it is hypothesized that neuronal cells are destroyed by T cells targeted against HuD, a protein expressed by small-cell lung cancer cells and neurons. There is only limited evidence for the existence of HuD-specific T cells. To detect these T cells in the blood of Hu-PNS patients, we employed 3 highly sensitive assays that included T cell stimulation with dendritic cells (DCs) to specifically expand the number of any HuD-specific T cells. A total of 17 Hu-PNS patients were tested with 1 or more of the following 3 assays: (1) tetramer staining after stimulation of T cells with conventionally generated DCs (n = 9), (2) interleukin (IL)-13 enzyme-linked immunosorbent spot (ELISpot; n = 3), IL-4 and IL-5 and interferon (IFN)-γ multiplex cytokine bead array (n = 2) to assay cytokine production by T cells after stimulation with conventionally generated DCs, and (iii) IFN-γ ELISpot and tetramer staining after T cell stimulation with accelerated co-cultured DCs (n = 11). No circulating HuD-specific T cells were found. We suggest that either autoaggressive T cells in Hu-PNS are not targeted against HuD or that their numbers in the blood are too low for detection by highly sensitive techniques.

A case of follicular lymphoma associated with paraneoplastic cerebellar degeneration

Paraneoplastic neurological disorders (PND) are neurological effects of malignancy that are recognized as immune-mediated disorders caused by aberrant expression of a tumor antigen that is normally expressed in the nervous system. We report a case of cerebellar ataxia which turned out to be paraneoplastic cerebellar degeneration, a subtype of PND that develops cerebellar symptoms, that was caused by follicular lymphoma. After chemotherapy, the patient attained sufficient improvement of cerebellar symptoms along with complete remission of lymphoma. Paraneoplastic cerebellar degeneration should be recognized as a rare complication of lymphoma as it is important to start proper treatment before the neurological symptoms become irreversible.

Narcolepsy with hypocretin/orexin deficiency, infections and autoimmunity of the brain

The loss of hypothalamic hypocretin/orexin (hcrt) producing neurons causes narcolepsy with cataplexy. An autoimmune basis for the disease has long been suspected and recent results have greatly strengthened this hypothesis. Narcolepsy with hcrt deficiency is now known to be associated with a Human Leukocyte Antigen (HLA) and T-cell receptor (TCR) polymorphisms, suggesting that an autoimmune process targets a single peptide unique to hcrt-cells via specific HLA-peptide-TCR interactions. Recent data have shown a robust seasonality of disease onset in children and associations with Streptococcus Pyogenes, and influenza A H1N1-infection and H1N1-vaccination, pointing towards processes such as molecular mimicry or bystander activation as crucial for disease development. We speculate that upper airway infections may be common precipitants of a whole host of CNS autoimmune complications including narcolepsy.

[N-methyl-d-aspartate receptor antibody encephalitis: a treatable disorder involving B-lymphocytes. A report of two patients]

INTRODUCTION

N-methyl-D-aspartate receptor antibody (anti-NMDA-r AB) encephalitis has been recently identified. We report two cases illustrating the clinical features, response to immunomodulatory treatment and involvement of B-lymphocytes that characterizes this disorder.

CASE REPORTS

These patients illustrated the classic clinical features of anti-NMDA-r AB encephalitis including occurrence in young female, presence of severe neurological and psychiatric manifestations with confusion, seizures, mutism, hypovigilence and involuntary movements, and inflammatory cerebrospinal fluid. Both patients improved after immunotherapy. In case 1, the encephalitis was associated with an ovarian teratoma containing neuronal elements. In case 2, there was no tumor identified. A brain biopsy showed prominent perivascular B-cells infiltrates with some T-cells distributed in the brain parenchyma.

CONCLUSION

Anti-NMDA-r AB encephalitis is certainly not rare and needs to be promptly recognized and treated. An associated neoplasia is inconstant and the pathophysiology involves humoral immunity.

Onconeural antibodies in patients with neurological symptoms: detection and clinical significance

BACKGROUND

Onconeural antibodies are strongly associated with cancer and paraneoplastic neurological syndromes (PNS). Most of these antibodies are well-characterized (antibodies against Hu, Yo, Ri, CRMP5, amphiphysin, Ma2 and Tr) and are in common use for the diagnosis of definite PNS.

MATERIALS AND METHODS

Literature on detection and clinical significance of onconeural antibodies were identified by using relevant search terms in PubMed and reviewed.

CONCLUSIONS

The onconeural antibodies are directed against intracellular antigens and their pathogenic role is still largely unknown. They are highly specific markers of paraneoplastic aetiology in patients with neurological symptoms. Detection of an onconeural antibody in a patient with neurological symptoms should lead to prompt investigation for cancer. However, absence of detectable onconeural antibodies does not exclude the PNS diagnosis. In particular, failure to detect antibodies in patients without classical PNS symptoms may result in less vigorous cancer screening and diagnostic delay. Neuronal antibodies that are directed to synaptic proteins or proteins of the cell membrane are also associated with neurological symptoms, and probably have pathogenic effects. The association between these antibodies and cancer is less robust, and they are usually not included among the onconeural antibodies.

Autoimmunity associated with immunotherapy of cancer

In this age of promise of new therapies for cancer, immunotherapy is emerging as an exciting treatment option for patients. Vaccines and cytokines are being tested extensively in clinical trials, and strategies using monoclonal antibodies and cell transfer are mediating dramatic regression of tumors in patients with certain malignancies. However, although initially advocated as being more specific for cancer and having fewer side effects than conventional therapies, it is becoming increasingly clear that many immunotherapies can lead to immune reactions against normal tissues. Immunotoxicities resulting from treatment can range from relatively minor conditions, such as skin depigmentation, to severe toxicities against crucial organ systems, such as liver, bowel, and lung. Treatment-related toxicity has correlated with better responses in some cases, and it is probable that serious adverse events from immune-mediated reactions will increase in frequency and severity as immunotherapeutic approaches become more effective. This review introduces immunotherapeutic approaches to cancer treatment, provides details of toxicities arising from therapy, and discusses future potential ways to avoid or circumvent these side effects.

RNA regulation in neurologic disease and cancer

The paraneoplastic neurologic diseases (PNDs) are brain degenerations that develop in the setting of clinically inapparent cancers. PNDs arise when common cancers express brain proteins, triggering an anti-tumor immune response and tumor immunity. Research on these brain-cancer proteins has revealed a new world of neuron-specific RNA binding proteins whose functions may be aberrantly used by tumor cells. Efforts to gain insight into their function has led to the development of new methods and strategies to understand RNA protein regulation in living tissues.

The onconeural antigen cdr2 is a novel APC/C target that acts in mitosis to regulate c-myc target genes in mammalian tumor cells

Cdr2 is a tumor antigen expressed in a high percentage of breast and ovarian tumors and is the target of a naturally occurring tumor immune response in patients with paraneoplastic cerebellar degeneration, but little is known of its regulation or function in cancer cells. Here we find that cdr2 is cell cycle regulated in tumor cells with protein levels peaking in mitosis. As cells exit mitosis, cdr2 is ubiquitinated by the anaphase promoting complex/cyclosome (APC/C) and rapidly degraded by the proteasome. Previously we showed that cdr2 binds to the oncogene c-myc, and here we extend this observation to show that cdr2 and c-myc interact to synergistically regulate c-myc-dependent transcription during passage through mitosis. Loss of cdr2 leads to functional consequences for dividing cells, as they show aberrant mitotic spindle formation and impaired proliferation. Conversely, cdr2 overexpression is able to drive cell proliferation in tumors. Together, these data indicate that the onconeural antigen cdr2 acts during mitosis in cycling cells, at least in part through interactions with c-myc, to regulate a cascade of actions that may present new targeting opportunities in gynecologic cancer.

Update on paraneoplastic neurological syndromes

PURPOSE OF REVIEW

To describe specificities and new advances in treatment of paraneoplastic neurological syndromes (PNS).

RECENT FINDINGS

PNS are defined as neurological syndromes of unknown cause that often antedate the diagnosis of an underlying cancer that is usually not clinically evident. The clinical signs of PNS are accurately described and 'classical' PNS have been established. Within the context of these syndromes, the concept of limbic encephalitis has evolved dramatically in the last 2 years due to the description of new auto-antibodies. The diagnosis and treatment of the associated cancer remains the key goal of the clinical management of PNS. However, the specific treatment of the neurological symptoms primarily depends on the immunological findings.

SUMMARY

There is increasing recognition of an extensive array of PNS and of several paraneoplastic antibodies as biological markers of these disorders. Basic immunological studies support the pathogenic role of some of these antibodies. Others are only markers of the disease.

Encephalitis with herpes simplex-2 in the cerebrospinal fluid and anti-RI (ANNA-2) antibodies: an infectious or a paraneoplastic syndrome?

We report on a 70-year-old woman with partial complex status epilepticus who was initially diagnosed with herpes simplex-2 (HSV-2) encephalitis, based on brain magnetic resonance imaging (MRI) findings, cerebrospinal fluid (CSF) lymphocytic pleocytosis and HSV-2 DNA detection by polymerase chain reaction (PCR) in the CSF, but without improvement on intravenous acyclovir. Anti-Ri antibodies were positive and computed tomography (CT) investigations revealed a small cell carcinoma at biopsy suggesting paraneoplastic encephalitis. The outcome was unfavourable and the autopsy showed typical features of paraneoplastic encephalitis but no evidence of viral inclusions. This case report is interesting because: (1) it is the first report of an autopsy proven paraneoplastic widespread encephalitis with anti-Ri antibodies; (2) despite a positive HSV-2 PCR in the CSF, there was no sign of herpetic infections of the nervous system; and (3) it illustrates the fact that if paraneoplastic antibodies are usually good markers of the underlying tumour, they are not always predictive of neurological deficits.

Patients with lung cancer and paraneoplastic Hu syndrome harbor HuD-specific type 2 CD8+ T cells

Paraneoplastic neurologic disorders (PNDs) offer an uncommon opportunity to study human tumor immunity and autoimmunity. In small cell lung cancer (SCLC), expression of the HuD neuronal antigen is thought to lead to immune recognition, suppression of tumor growth, and, in a subset of patients, triggering of the Hu paraneoplastic neurologic syndrome. Antigen-specific CTLs believed to contribute to disease pathophysiology were described 10 years ago in paraneoplastic cerebellar degeneration. Despite parallel efforts, similar cells have not been defined in Hu patients. Here, we have identified HuD-specific T cells in Hu patients and provided an explanation for why their detection has been elusive. Different Hu patients harbored 1 of 2 kinds of HuD-specific CD8+ T cells: classical IFN-gamma-producing CTLs or unusual T cells that produced type 2 cytokines, most prominently IL-13 and IL-5, and lacked cytolytic activity. Further, we found evidence that SCLC tumor cells produced type 2 cytokines and that these cytokines trigger naive CD8+ T cells to adopt the atypical type 2 phenotype. These observations demonstrate the presence of an unusual noncytotoxic CD8+ T cell in patients with the Hu paraneoplastic syndrome and suggest that SCLC may evade tumor immune surveillance by skewing tumor antigen-specific T cells to this unusual noncytolytic phenotype.

[Paraneoplastic neurological syndromes]

BACKGROUND

Paraneoplastic neurological syndromes constitute a heterogenous group of diseases, which often cause severe neurological symptoms. Extensive research during the last 20 years has led to identification of new antigenic targets and inclusion of additional clinical conditions into this group of syndromes.

MATERIAL AND METHODS

The article is based on a non-systematic search of PubMed and the author's own experience with antibody analysis, treatment of patients and research within the field.

RESULTS AND INTERPRETATION

Paraneoplastic neurological syndromes affect less than 1 % of all patients with cancer. The etiology is probably autoimmune, and involves immune responses (cellular and humoral) against antigens shared by tumor cells and normal neurons. Many, but not all patients harbour onconeural antibodies (in serum and spinal fluid), which are highly useful diagnostic markers for a paraneoplastic etiology. The cornerstone of therapy is treatment of the underlying tumor, but additional immunosuppressive therapy is often administered.

Paraneoplastic neurological syndromes: a review

BACKGROUND

Paraneoplastic neurologic syndromes (PNS) constitute a rare group of disorders resulting from damage to the nervous system in the setting of cancer physically unrelated to the tumor site. PNS are believed to result from an autoimmune attack of normal neuronal tissue, spurred by similar neuronal antigens ectopically expressed by tumor cells.

REVIEW SUMMARY

The most common PNS are reviewed and also their association with specific onconeural antibodies, some directly pathogenic, others whose role in the disease process is less clear-cut. This diversity in pathogenesis is likely due to the relative role of humoral versus cellular immunity in PNS. Virtually any cancer may result in PNS but certain tumors, small cell lung cancer, gynecologic cancers (breast and ovarian), thymoma, and plasma cell tumors are more frequently encountered. In most instances, immunosuppressive therapy is unhelpful and outcome is poor.

CONCLUSIONS

PNS have diverse presentations, affecting both the central and peripheral nervous system and commonly, it is the PNS, not cancer that is the presenting symptom. Only subsequently, after onconeural antibodies are discovered or cancer is found, is PNS diagnosed. Neurologists should familiarize themselves with these rare syndromes and treatment principles, as rapid detection and treatment of the underlying tumor offer the best chance for recovery or prevention of further neurologic deterioration.

Effective immunosuppressant therapy with cyclophosphamide and corticosteroids in paraneoplastic cerebellar degeneration

Paraneoplastic cerebellar degeneration (PCD) is a rare immune mediated phenomenon often associated with cancer of the ovarian. Hitherto, tumor dissection is the mainstay in therapy while immunomodulatory treatment regimes often fail. Here we report on an 86 year old female patient who developed a severe pancerebellar syndrome. Clinical course, onconeural (anti-Yo) antibodies and detection of ovarian cancer suggest the assumption of PCD as the most probable diagnosis. We initiated a high-dose course of corticosteroids followed by a single dose of cyclophosphamide (600 mg/day). Surprisingly patient's condition improved and stabilized within days subsequent to cyclophosphamide application. This case demonstrates the benefit of immunosuppressive therapy in an anti-Yo positive patient with severe PCD secondary to an ovarian cancer.

CRMP5 antibodies in patients with small-cell lung cancer or thymoma

The collapsin response mediator protein 5 (CRMP5) antibody is usually associated with paraneoplastic neurological syndrome (PNS) and small-cell lung cancer (SCLC) or thymoma. The objective of this study was to assess the frequency of CRMP5 antibodies in patients with such tumours and to see if the presence of antibodies was associated with prognosis in these cancers. A multi-well adapted immunoprecipitation assay using radiolabelled recombinant CRMP5 protein, produced by coupled in vitro transcription/translation, was used for the detection of CRMP5 antibodies. Sera from 200 patients with SCLC, 73 patients with thymoma and myasthenia gravis (MG) and from 300 healthy blood donors were examined for CRMP5 antibodies. Positive sera were also examined by immunofluorescence and immune blots. The serological results were compared with disease severity of the patients with thymoma or SCLC. CRMP5 antibodies were detected in 10/200 (5%) of the SCLC, 9/73 (12%) of the thymomas and in 2/300 (0.6%) of the healthy controls by immunoprecipitation. The antibodies were less frequently detected by immunofluorescence or immune blots. There was no significant correlation between CRMP5 antibodies and disease severity. CRMP5 antibodies are more than twice as frequent, and the antibody levels are higher in patients with thymoma and MG than in patients with SCLC. The antibodies are correlated to these tumours, but not to disease severity.