SEREX identification of new tumor antigens linked to melanoma-associated retinopathy

Plasma Antiretinal Autoantibody Profiling and Diagnostic Efficacy in Patients With Autoimmune Retinopathy

PURPOSE

To evaluate plasma antiretinal autoantibody (ARA) profiling and diagnostic efficacy for autoimmune retinopathy (AIR).

DESIGN

A multicenter, diagnostic evaluation study.

METHODS

Forty-nine patients with a clinical diagnosis of AIR, disease controls including 20 patients with retinitis pigmentosa (RP), and 30 normal controls were included. Plasma samples from patients were analyzed for the presence of 6 ARAs, including recoverin, α-enolase, carbonic anhydrase II, heat shock protein 60, aldolase C, and cone-rod homeobox/cone-rod retinal dystrophy 2 using western blotting.

RESULTS

Autoantibody detection rates against cone-rod homeobox/cone-rod retinal dystrophy 2, heat shock protein 60, and aldolase C in AIR were 67.3%, 40.8%, and 42.9%, respectively, which were higher than those in RP and normal controls (P < .001, P < .001, and P = .007, respectively), but recoverin, α-enolase, and carbonic anhydrase II were not different from other control groups (P = .117, P = .774, and P = .467, respectively). Among ARAs, antirecoverin antibody was the most specific, as it was found in 3 (6.1%) patients with AIR and none of the control groups. As the number of detected ARAs increased, the probability of AIR increased (odds ratio: 1.913; P < .001; 95% confidence interval: 1.456-2.785). The positive number of ARAs was significantly higher when photoreceptor disruption was observed on optical coherence tomography, or severe dysfunction was observed in electroretinography (P = .022 and P = .029, respectively).

CONCLUSIONS

The profiles of ARAs in the AIR group were different from those in the RP and normal controls. The higher number of positive ARAs suggests a higher possibility of AIR diagnosis. ARAs should be used as adjunct tools for the clinical diagnosis of AIR.

Paraneoplastic ocular syndrome: a pandora's box of underlying malignancies

Paraneoplastic syndromes affecting the visual system are a group of conditions that arise in the systemic malignancy framework. In this review, we have provided a detailed and comprehensive overview of the published literature on the various ophthalmic paraneoplastic manifestations. A systematic review of many databases has been performed to identify ample literature on the paraneoplastic syndromes related to ophthalmology. We have discussed here the clinical features, pathogenesis, and treatment strategies of various ophthalmic paraneoplastic syndromes. It can be challenging to distinguish these disorders from their non-paraneoplastic counterparts and to determine the appropriate systemic assessment for the tumour responsible, to have a proper approach towards the management of the syndrome. METHOD: We searched PubMed, Science Direct and Journal of Ophthalmology for studies published in English between 1995 and April 2020, incorporating the general search term "paraneoplastic ocular syndrome" with connecting terms relevant to subheadings-e.g. Key search terms were cancer-associated retinopathy, (CAR), melanoma-associated retinopathy, (MAR), paraneoplastic retinopathy, autoimmune retinopathy, autoimmune-related retinopathy, and optic neuropathy, (ARRON), acute zonal occult outer retinopathy, (AZOOR), paraneoplastic vitelliform maculopathy, paraneoplastic vitelliform retinopathy, bilateral diffuse uveal melanocytic proliferation, (BDUMP), paraneoplastic optic neuropathy, (PON), polyneuropathy, organomegaly, endocrinopathy, monoclona gammopathy, and skin changes syndrome (POEMS) and various other terms. References from identified studies have been reviewed and included if deemed appropriate, valid, and scientifically important. If referenced in a selected English paper, we contemplated papers in other languages too. We preferentially selected papers that have been published in the last 10 years, but we have included relevant older references.

Current Techniques to Accurately Measure Anti-retinal Autoantibodies

Introduction

Autoimmune retinopathy (AR) is a sight-threating retinal disorder that is mediated by autoantibodies (AAbs) against retinal proteins. The visual paraneoplastic syndromes, including cancer-associated retinopathy (CAR) and melanoma-associated retinopathy (MAR) are mediated by anti-retinal AAbs. A number of immunochemical techniques have been used to detect serum anti-retinal autoantibodies in patients to help with autoimmune diagnosis.

Area covered

We review techniques used for serum autoantibody evaluation in patients with suspected autoimmune retinopathy.

Expert opinion

Detection of serum AAbs have served as the standard diagnostic tool for autoimmune retinopathies and for management of retinal disorders. An identification of anti-retinal autoantibody or multiple autoantibodies can be useful for not only for diagnosis of autoimmune retinopathies but also for management of retinal disorders. We propose that the line-blotting technique used in conjunction with immunohistochemistry are the best and most reliable assays for detection of serum anti-retinal AAb in the context of clinical history and findings. Clinician should recognize that the majority of antigenic targets identified to date in retinal autoimmunity are ubiquitously expressed proteins (e.g. enolase), which may be difficult to reconcile with the specific patterns of retinal damage observed in CAR, MAR, or AR.

Adoptive Cell Therapy Targeting Neoantigens: A Frontier for Cancer Research

Adoptive cell therapy (ACT) is a kind of immunotherapy in which T cells are genetically modified to express a chimeric antigen receptor (CAR) or T cell receptor (TCR), and ACT has made a great difference in treating multiple types of tumors. ACT is not perfect, and it can be followed by severe side effects, which hampers the application of ACT in clinical trials. One of the most promising methods to minimize side effects is to endow adoptive T cells with the ability to target neoantigens, which are specific to tumor cells. With the development of antigen screening technologies, more methods can be applied to discover neoantigens in cancer cells, such as whole-exome sequencing combined with mass spectrometry, neoantigen screening through an inventory-shared neoantigen peptide library, and neoantigen discovery via trogocytosis. In this review, we focus on the side effects of existing antigens and their solutions, illustrate the strategies of finding neoantigens in CAR-T and TCR-T therapies through methods reported by other researchers, and summarize the clinical behavior of these neoantigens.

Are Anti-Retinal Autoantibodies a Cause or a Consequence of Retinal Degeneration in Autoimmune Retinopathies?

Autoantibodies (AAbs) against various retinal proteins have been associated with vision loss in paraneoplastic and non-paraneoplastic autoimmune retinopathies (AR). There are two major paraneoplastic syndromes associated anti-retinal AAbs, cancer-associated retinopathy (CAR), and melanoma-associated retinopathy. Some people without a cancer diagnosis may present symptoms of CAR and have anti-retinal AAbs. The etiology and pathogenesis of those entities are not fully understood. In this review, we provide evidence for the role of AAbs in retinal death and degeneration. Studies of epitope mapping for anti-recoverin, anti-enolase, and anti-carbonic anhydrase II revealed that although patients' AAbs may recognize the same retinal protein as normal individuals they bind to different molecular domains, which allows distinguishing between normal and diseased AAbs. Given the great diversity of anti-retinal AAbs, it is likely some antibodies have greater pathogenic potential than others. Pathogenic, but not normal antibodies penetrate the target cell, reach their specific antigen, induce apoptosis, and impact retinal pathophysiology. Photoreceptors, dying by apoptosis, induced by other than immunologic mechanisms produce substantial amounts of metabolic debris, which consequently leads to autoimmunization and enhanced permeability of the blood-retinal barrier. AAbs that were made as a part of anti-cancer response are likely to be the cause of retinal degeneration, whereas others, generated against released antigens from damaged retina, contribute to the progression of retinopathy. Altogether, AAbs may trigger retinal degeneration and may also exacerbate the degenerative process in response to the release of sequestered antigens and influence disease progression.

Multiplex bead-based measurement of humoral immune responses against tumor-associated antigens in stage II melanoma patients of the EORTC18961 trial

Purpose: Determine the prognostic and predictive significance of tumor associated antigen (TAA)-specific serum antibodies in melanoma patients of a large adjuvant vaccination phase III trial. Patients and methods: Serum IgG antibodies were measured against a panel of 43 antigens by a bead-based multiplex assay in 970 stage II melanoma patients of the EORTC18961 trial, evaluating adjuvant ganglioside GM2-KLH/QS-21 vaccination versus observation. Primary end point was relapse-free survival (RFS). Patients' sera at baseline, after 12 and 48 weeks of study treatment and at the last available time point (at recurrence/remission) were evaluated. Results: Prognostic clinical variables are gender, surgical confirmation of lymph node-negative status, Breslow thickness and ulceration of the primary. Prognostic spontaneous antibody responses were associated with a significant dismal (GM2, Rhod_E2, SSX2) or good prognosis (CyclinB1, SCYE1v1) for RFS, distant metastasis-free (DMFS) or overall survival (OS). Predictive spontaneous antibody responses based on significant interaction with treatment were RhodN p = 0.02, Rab38 p = 0.04 for RFS, RhodE2 p = 0.006, Recoverin p = 0.04 for DMFS and RhodE2 p = 0.003; Recoverin p = 0.04, NA17.A p = 0.04, for OS respectively. The subgroups of patients according to antibody responses for RFS were determined for RhodN sero-negative (n = 849, HR = 1.07, p = 0.6); RhodN sero-positive (n = 121,HR = 0.42, p = 0.01) and Rab38 sero-negative (n = 682, HR = 1.12, p = 0.42), Rab38 sero-positive (n = 288, HR = 0.65, p = 0.04) patients respectively. Conclusion: We identified prognostic serum antibody responses against TAA in stage II melanoma patients. A set of antibody responses correlated with a beneficial outcome for GM2 vaccination.

Serum Autoantibody Profiling of Patients with Paraneoplastic and Non-Paraneoplastic Autoimmune Retinopathy

PURPOSE

Although multiple serum antiretinal autoantibodies (ARAs) have been reported in patients with paraneoplastic and non-paraneoplastic autoimmune retinopathy ((n)pAIR), not all retinal antigens involved in (n)pAIR are specified. This study aims to serologically identify patients with presumed (n)pAIR through determination of both known and unknown ARAs by autoantibody profiling.

METHODS

An antigen suspension bead array using 188 different antigens representing 97 ocular proteins was performed to detect ARAs in serum samples of patients with presumed (n)pAIR (n = 24), uveitis (n = 151) and cataract (n = 21). Logistic regressions were used to estimate the associations between ocular antigens and diagnosis. Validation of interphotoreceptor matrix proteoglycan 2 (IMPG2) and recoverin antigens was performed by immunohistochemistry and immunoblot, respectively.

RESULTS

Samples of patients with presumed (n)pAIR exhibited a broad spectrum of ARAs. We identified retinal antigens that have already been described previously (e.g. recoverin), but also identified novel ARA targets. Most ARAs were not specific for (n)pAIR since their presence was also observed in patients with cataract or uveitis. High titers of autoantibodies directed against photoreceptor-specific nuclear receptor and retinol-binding protein 3 were more common in patients with presumed (n)pAIR compared to uveitis (p = 0.015 and p = 0.018, respectively). The presence of all other ARAs did not significantly differ between groups. In patients with presumed (n)pAIR, anti-recoverin autoantibodies were the most prevalent ARAs. Validation of bead array results by immunohistochemistry (anti-IMPG2) and immunoblot (anti-recoverin) showed concordant results in (n)pAIR patients.

CONCLUSIONS

Patients with (n)pAIR are characterized by the presence of a broad spectrum of ARAs. The diagnosis of (n)pAIR cannot be based on the mere presence of serum ARAs, as these are also commonly present in uveitis as well as in age-related cataract patients.

Prognostic significance of spontaneous antibody responses against tumor-associated antigens in malignant melanoma patients

Distribution, patterns and prognostic impact of spontaneous antibody responses against different tumor-associated antigens (TAAs) in malignant melanoma patients are unknown so far and were investigated in this study for the first time in a large cohort at different stages of the disease, identifying new prognostic biomarkers for malignant melanoma. Serum samples from 365 melanoma patients (97 Stage I melanoma patients, 87 Stage II, 92 Stage III and 89 Stage IV) and 100 age and gender matched healthy control donors were analyzed. Samples were drawn at the time of diagnosis (Stages I-III) or at time of diagnosis of distant metastasis (Stage IV). Applying a novel multiplex assay, humoral immune responses against 29 TAAs were determined and the association between response and patient survival was investigated. Antibody responses were mainly found in melanoma patients and all tested antigens elicited immune responses in all disease stages. Antibody responses against single antigens were either associated with poor prognosis and/or shorter progression-free survival (PFS) or had no influence. While in Stages I-III significant associations were observed between an antibody response and overall survival or PFS, among Stage IV patients, no significant association was found. Multivariate analyses identified specific humoral immune responses as prognostic factors independently of age, chemotherapy and immunotherapy. Antibody responses against specific TAA in Stage I-III melanoma patients correlate with poor prognosis and/or shorter PFS. These results may help to design clinical studies in order to evaluate the potential of these responses as prognostic serological biomarkers.

Autoantibodies to transient receptor potential cation channel, subfamily M, member 1 in a Japanese patient with melanoma-associated retinopathy

PURPOSE

To report a case of melanoma-associated retinopathy (MAR) in a Japanese patient found to have autoantibodies to transient receptor potential cation channel, subfamily M, member 1 (TRPM1).

CASE

An 82-year-old man presented with blurred vision OS as well as night blindness and photopsia OU. Fundus photography, fluorescein angiography, and spectral domain-optical coherence tomography findings were essentially normal. Goldmann perimetry revealed a relative central scotoma, including the blind spot in the right eye, as well as a relative scotoma around a blind spot OS. The full-field scotopic electroretinograms showed a "negative-type" pattern OU, suggestive of extensive bipolar cell dysfunction. Systemic examination revealed that the patient had malignant melanoma of the anus with lung metastasis. Autoantibodies to TRPM1 were detected in the serum of the patient by immunoblot analysis. Vitreous opacity developed during follow-up. The visual symptoms and vitreous opacity of the patient were markedly improved after oral prednisolone therapy. The patient died as a result of widespread metastasis of the melanoma at 11 months after his first visit.

CONCLUSION

The present case is the first reported instance of MAR positive for autoantibodies to TRPM1 in an Asian patient.

Diagnostic features of the autoimmune retinopathies

The term autoimmune retinopathy encompasses a spectrum of rare autoimmune diseases that affect retinal function, often but not exclusively at the level of the photoreceptor. They typically present with painless visual loss, which may be accompanied by normal fundus examination. Some are progressive, often rapidly. They present a diagnostic challenge because there are no standardised clinical or laboratory based diagnostic criteria. Included within the spectrum are cancer-associated retinopathy, melanoma-associated retinopathy and presumed non-paraneoplastic autoimmune retinopathy. Differentiation from other retinopathies can be challenging, with overlap in symptoms, signs, and investigation findings, and an absence of pathognomonic features. However, technological developments in ophthalmic imaging and serological investigation over the past decade are adding novel dimensions to the investigation and classification of patients with these rare diseases. This review addresses the clinical, imaging, and serological features of the autoimmune retinopathies, and discusses the relative strengths and limitations of candidate diagnostic features.

New targets for the immunotherapy of colon cancer-does reactive disease hold the answer?

Colorectal cancer (CRC) is one of the most commonly diagnosed cancers in both men and women, posing a serious demographic and economic burden worldwide. In the United Kingdom, CRC affects 1 in every 20 people and it is often detected once well established and after it has spread beyond the bowel (Stage IIA-C and Stage IIIA-C). A diagnosis at such advanced stages is associated with poor treatment response and survival. However, studies have identified two sub-groups of post-treatment CRC patients--those with good outcome (reactive disease) and those with poor outcome (non-reactive disease). We aim to review the state-of-the-art for CRC with respect to the expression of cancer-testis antigens (CTAs) and their identification, evaluation and correlation with disease progression, treatment response and survival. We will also discuss the relationship between CTA expression and regulatory T-cell (Treg) activity to tumorigenesis and tumor immune evasion in CRC and how this could account for the clinical presentation of CRC. Understanding the molecular basis of reactive CRC may help us identify more potent novel immunotherapeutic targets to aid the effective treatment of this disease. In this review, based on our presentation at the 2012 International Society for the Cell and Gene Therapy of Cancer annual meeting, we will summarize some of the most current advances in CTA and CRC research and their influence on the development of novel immunotherapeutic approaches for this common and at times difficult to treat disease.

Autoantibodies in melanoma-associated retinopathy target TRPM1 cation channels of retinal ON bipolar cells

Melanoma-associated retinopathy (MAR) is characterized by night blindness, photopsias, and a selective reduction of the electroretinogram b-wave. In certain cases, the serum contains autoantibodies that react with ON bipolar cells, but the target of these autoantibodies has not been identified. Here we show that the primary target of autoantibodies produced in MAR patients with reduced b-wave is the TRPM1 cation channel, the newly identified transduction channel in ON bipolar cells. Sera from two well characterized MAR patients, but not from a control subject, stained human embryonic kidney cells transfected with the TRPM1 gene, and Western blots probed with these MAR sera showed the expected band size (∼180 kDa). Staining of mouse and primate retina with MAR sera revealed immunoreactivity in all types of ON bipolar cells. Similar to staining for TRPM1, staining with the MAR sera was strong in dendritic tips and somas and was weak or absent in axon terminals. This staining colocalized with GFP in Grm6-GFP transgenic mice, where GFP is expressed in all and only ON bipolar cells, and also colocalized with Gα(o), a marker for all types of ON bipolar cells. The staining in ON bipolar cells was confirmed to be specific to TRPM1 because MAR serum did not stain these cells in a Trpm1(-/-) mouse. Evidence suggests that the recognized epitope is likely intracellular, and the sera can be internalized by retinal cells. We conclude that the vision of at least some patients with MAR is compromised due to autoantibody-mediated inactivation of the TRPM1 channel.

Identification of autoantibodies against TRPM1 in patients with paraneoplastic retinopathy associated with ON bipolar cell dysfunction

Background

Paraneoplastic retinopathy (PR), including cancer-associated retinopathy (CAR) and melanoma-associated retinopathy (MAR), is a progressive retinal disease caused by antibodies generated against neoplasms not associated with the eye. While several autoantibodies against retinal antigens have been identified, there has been no known autoantibody reacting specifically against bipolar cell antigens in the sera of patients with PR. We previously reported that the transient receptor potential cation channel, subfamily M, member 1 (TRPM1) is specifically expressed in retinal ON bipolar cells and functions as a component of ON bipolar cell transduction channels. In addition, this and other groups have reported that human TRPM1 mutations are associated with the complete form of congenital stationary night blindness. The purpose of the current study is to investigate whether there are autoantibodies against TRPM1 in the sera of PR patients exhibiting ON bipolar cell dysfunction.

Methodology/Principal Findings

We performed Western blot analysis to identify an autoantibody against TRPM1 in the serum of a patient with lung CAR. The electroretinograms of this patient showed a severely reduced ON response with normal OFF response, indicating that the defect is in the signal transmission between photoreceptors and ON bipolar cells. We also investigated the sera of 26 patients with MAR for autoantibodies against TRPM1 because MAR patients are known to exhibit retinal ON bipolar cell dysfunction. Two of the patients were found to have autoantibodies against TRPM1 in their sera.

Conclusion/Significance

Our study reveals TRPM1 to be one of the autoantigens targeted by autoantibodies in at least some patients with CAR or MAR associated with retinal ON bipolar cell dysfunction.

Immunologic biomarkers as correlates of clinical response to cancer immunotherapy

Over the last few years, several newly developed immune-based cancer therapies have been shown to induce clinical responses in significant numbers of patients. As a result, there is a need to identify immune biomarkers capable of predicting clinical response. If there were laboratory parameters that could define patients with improved disease outcomes after immunomodulation, product development would accelerate, optimization of existing immune-based treatments would be facilitated and patient selection for specific interventions might be optimized. Although there are no validated cancer immunologic biomarkers that are predictive of clinical response currently in widespread use, there is much published literature that has informed investigators as to which markers may be the most promising. Population-based studies of endogenous tumor immune infiltrates and gene expression analyses have identified specific cell populations and phenotypes of immune cells that are most likely to mediate anti-tumor immunity. Further, clinical trials of cancer vaccines and other cancer directed immunotherapy have identified candidate immunologic biomarkers that are statistically associated with beneficial clinical outcomes after immune-based cancer therapies. Biomarkers that measure the magnitude of the Type I immune response generated with immune therapy, epitope spreading, and autoimmunity are readily detected in the peripheral blood and, in clinical trials of cancer immunotherapy, have been associated with response to treatment.

Melanoma-associated retinopathy: a paraneoplastic autoimmune complication

OBJECTIVES

To study 11 patients with melanoma-associated retinopathy (MAR) to clarify the reliability of various methods of diagnostic testing, to determine the underlying antigenic retinal proteins, and to study the clinical histories and types of associated melanomas.

METHODS

Clinical data were obtained from patients with melanoma who developed marked visual problems. Testing included electroretinography, kinetic visual fields, comparative studies of Western blots, and indirect immunohistologic examination to detect antiretinal antibodies, as well as proteomic studies to identify underlying antigenic retinal proteins.

RESULTS

Patients with MAR typically have rapid onset of photopsias, scotomata, and loss of central or paracentral vision. Ophthalmoscopy seldom shows significant changes early, but electroretinograms are abnormal. Results of Western blots and immunohistologic examination can show antiretinal antibodies but not always. Most patients (9 of 11) had a strong family history of autoimmune disorders. Any type of melanoma (cutaneous, choroidal, ciliary body, or choroidal nevi) may be associated with this paraneoplastic autoimmune reactivity. MAR may precede or follow the diagnosis of melanoma. Patients with MAR have the same antigenic retinal proteins that have been associated with cancer-associated retinopathy. In addition, 2 new antigenic retinal proteins, aldolase A and aldolase C, were found.

CONCLUSIONS

There was a high prevalence of positive family histories of autoimmune disease in patients with MAR. To confirm the disorder, multiple clinical and serum diagnostic techniques (Western blot or indirect immunohistologic examination) are needed. Two newly observed antigenic retinal proteins, aldolase A and aldolase C, are associated with MAR.

Proteome-based analysis of serologically defined tumor-associated antigens in cutaneous lymphoma

Information on specificities of serological responses against tumor cells in cutaneous lymphoma patients is relatively restricted. To advance the knowledge of serological immune responses against and to assess the scope of tumor antigenicity of cutaneous lymphoma, 1- and 2-dimensional Western blot analyses with sera from patients were combined with proteomics-based protein identification. Testing sera from 87 cutaneous lymphoma patients by 1-dimensional Western blot analysis, 64 cases of seroreactivity against lymphoma cells were found. The positive responses were relatively weak, restricted to few antigens in each case, and heterogeneous. To identify the antigens, proteins of the mycosis fungoides cell line MyLa and primary tumor cells were separated by 2-dimensional gel electrophoresis, Western-blotted and probed with heterogeneous and autologous patient sera. The antigens were identified from silver-stained replica gels by MALDI-TOF mass spectrometry. 14 different antigens were assigned and identified with this proteome-serological approach. Only one, vimentin, had been reported before, the other 13 are new antigens for cutaneous lymphomas.

Proteome serological determination of tumor-associated antigens in melanoma

Proteome serology may complement expression library-based approaches as strategy utilizing the patients' immune responses for the identification pathogenesis factors and potential targets for therapy and markers for diagnosis. Melanoma is a relatively immunogenic tumor and antigens recognized by melanoma-specific T cells have been extensively studied. The specificities of antibody responses to this malignancy have been analyzed to some extent by molecular genetic but not proteomics approaches. We screened sera of 94 melanoma patients for anti-melanoma reactivity and detected seropositivity in two-thirds of the patients with 2–6 antigens per case detected by 1D and an average of 2.3 per case by 2D Western blot analysis. For identification, antigen spots in Western blots were aligned with proteins in 2-DE and analyzed by mass spectrometry. 18 antigens were identified, 17 of which for the first time for melanoma. One of these antigens, galectin-3, has been related to various oncogenic processes including metastasis formation and invasiveness. Similarly, enolase has been found deregulated in different cancers. With at least 2 of 18 identified proteins implicated in oncogenic processes, the work confirms the potential of proteome-based antigen discovery to identify pathologically relevant proteins.

Autoantibody targets and their cancer relationship in the pathogenicity of paraneoplastic retinopathy

Paraneoplastic retinopathies (PR), including cancer-associated retinopathy (CAR) or the closely related melanoma-associated retinopathy (MAR) occur in a small subset of patients with retinal degeneration and systemic cancer. This autoimmune syndrome is characterized by sudden, progressive loss of vision in association with circulating anti-retinal autoantibodies. The PR syndromes are heterogeneous, may produce a number of ocular symptoms, and may be associated with several different neoplasms, including lung, breast, prostate, gynecological, and colon cancer, melanoma, and hematologic malignancies. We examined the onset of retinopathy in correlation to the diagnosis of cancer and the presence of specific anti-retinal autoantibodies in PR patients. In some patients without diagnosed malignant tumors, the onset of ocular symptoms and the presence of autoantibodies preceded the diagnosis of cancer by months to years, including anti-recoverin, anti-transducin-alpha, and anti-carbonic anhydrase II antibodies. Although anti-retinal autoantibodies may not be a good predictor of a specific neoplasm, they can be used as biomarkers for different subtypes of retinopathy. Identification of autoantibodies involved in autoimmune-mediated PR will help elucidate the mechanisms underlying the PR syndromes and develop targeted therapies for these sight-threatening disorders.

Human endogenous retrovirus K triggers an antigen-specific immune response in breast cancer patients

Recent evidence indicates that human cancer cells reactivate the expression of latent human endogenous retroviral (HERV) proteins. However, the extent to which cancer patients mount de novo immune responses against expressed HERV elements is unclear. In this study, we determined the extent of HERV-K env expression in human breast cancer (BC) and whether both humoral and cell-mediated immunity against HERV-K can be found in BC patients. We found HERV-K env protein expression in 88% of BC (n = 119) but not in normal breast (n = 76) tissues. ELISA screening assays detected significant titers of anti-HERV-K env IgG in a large proportion of BC patients. T-cell responses against HERV-K were also detected in peripheral blood mononuclear cells (PBMC) from BC patients stimulated with autologous dendritic cells pulsed with HERV-K env SU antigens. These responses included induction of T-cell proliferation (P = 0.0043), IFN-gamma production measured by enzyme-linked immunospot (P < 0.0001), and multiplex cytokine secretion (P = 0.0033). Multiplex cytokine analysis found a T-helper 1 cytokine response, including interleukin (IL)-2 (P = 0.0109), IL-6 (P = 0.0396), IL-8 (P = 0.0169), and IP-10 (P = 0.0045) secretion during in vitro stimulation of BC PBMC with HERV-K antigen. We also found HERV-K-specific CTLs that were capable of lysing target cells expressing HERV-K env protein in BC patients but not in normal female controls without cancer. These findings suggest that retroviral gene products are capable of acting as tumor-associated antigens activating both T-cell and B-cell responses in BC patients.

Paraneoplastic syndromes in neuro-ophthalmology

PURPOSE OF REVIEW

The aim of this review is to discuss and highlight the recent advances in our understanding of paraneoplastic syndromes in neuro-ophthalmology and their significance.

RECENT FINDINGS

The pathophysiologic mechanism in neuro-ophthalmic paraneoplastic syndromes involves an immune response triggered by aberrant expression of onconeuronal antigens that cross-react with antigens in the visual system. Recently, 18-fluoro-deoxy-glucose/positron emission tomography with computed tomography scanning has emerged as a useful modality in diagnosing occult tumors responsible for paraneoplastic syndromes. Paraneoplastic optic neuropathy has been recently associated with the anti-CV2/CRMP-5 antibody. The use of serologic analysis of recombinantly expressed clones (SEREX) has led to the identification of new antigens associated with melanoma-associated retinopathy, such as visual arrestin, rhodopsin, titin, and mitofilin. Calcium-channel blockers and alemtuzumab have been found to improve visual function in cancer-associated retinopathy. Rituximab has been found to be effective in childhood opsoclonus-myoclonus syndrome.

SUMMARY

A high index of suspicion is needed to diagnose neuro-ophthalmic paraneoplastic syndromes. There have been recent advances in our understanding of the pathophysiology and treatment of these disorders. This will facilitate early treatment of causative occult tumors and improves the prognosis.

RETINAL AUTOANTIBODIES

Retinal autoantibodies, commonly referred to as antiretinal antibodies (ARA), have been implicated in the pathogenicity of a variety of immune-mediated visual disorders. In the paraneoplastic syndrome, cancer-associated retinopathy (CAR), ARA with their targeted retinal antigens have been identified. There are many other infectious, inflammatory as well as degenerative retinopathies associated with the presence of ARA. More than 15 ARA have been identified in CAR. For these autoantibodies, the autoantigens still remain unknown. Recoverin, a calcium-binding retinal protein involved in the reversal of the phototransduction cascade, is well established as the most common CAR autoantigen. The proposed mechanism of antibody-mediated degeneration involves molecular mimicry and loss of peripheral tolerance to residing retinal antigens. In vitro, ARA have been shown to cause apoptotic death of photoreceptors. Questions remain though, regarding the access and penetration of these antibodies into the retina. Furthermore, the titer of ARA does not always correlate with clinical disease status. There exists lack of standardization of antibody and antigen detection. Thus, results from different laboratories cannot exactly be compared. Sensitivity and specificity for the detection of pathogenic ARA is also lacking. Though there are many caveats, presence of ARA still serves as an adjunctive study for the clinician to confirm a diagnosis, which often is difficult to make. The study of ARA serves as an excellent model for the elucidation of pathological mechanisms underlying autoimmune retinopathy and its allied disorders.

Photoreceptor proteins as cancer-retina antigens

Melanocytes, melanoma and photoreceptor cells are of neuroectodermal origin and have a certain sensitivity to light. In this study, we present evidence for photoreceptor proteins that are responsible for visual transduction and its regulation function as a new class of cancer antigens in melanoma. Visual rhodopsin, transducin, cGMP-phosphodiesterase 6, cGMP-dependent channels, guanylyl cyclase, rhodopsin kinase, recoverin and arrestin are expressed in melanoma and can induce antibody responses in patients. Melanocytes also express mRNA of all photoreceptor genes besides transducin, but were devoid of the corresponding protein, which was tested for rhodopsin, cGMP-phosphodiesterase, guanylyl cyclase and recoverin. Furthermore, we show for the first time that some healthy tissues express mRNA of these genes, but never protein. Expression profiles and autoantibody responses were confirmed in the MT/ret and the HGF(tg)/Ink4a(-/-) transgenic mouse melanoma models. We propose a molecular transition of cancer-retina antigens from mRNA expression in melanocytes to protein expression in melanoma. Our work provides the basis for analyzing regulation of photoreceptor gene expression in normal and malignant cells as well as possible therapeutic tumor targeting using the newly defined class of cancer-retina antigens.

Recoverin as a cancer-retina antigen

In photoreceptor cells the Ca(2+) -binding protein recoverin controls phosphorylation of the visual receptor rhodopsin by inhibiting rhodopsin kinase (GRK-1). It can also serve as a paraneoplastic antigen in the development of retinal degeneration in some patients with cancer. The aberrant expression of recoverin in cancer cells and the presence of autoantibodies against recoverin are essential for the occurrence of cancer-associated retinopathy, which finally results in the apoptosis of photoreceptor cells. Noteworthy in cancer patients, the aberrant recoverin expression and the appearance of autoantibodies against recoverin are more frequent than paraneoplastic syndromes. We suggest the term "cancer-retina antigens" for this kind of proteins like recoverin that are solely expressed in retina and tumor tissues and evoke antibodies and/or T cells in patients with cancer. The rare development of a paraneoplastic syndrome is possibly caused by this immune response and probably depends on further events allowing to overcome the blood-retina barrier and the immune privileged status of the retina. It is still unknown whether aberrantly expressed recoverin could have a specific function in cancer cells, though it is suggested that it can be functionally associated with G-protein-coupled receptor kinases. This paper reviews the present knowledge on paraneoplastic syndromes associated with the aberrant expression of recoverin. A possible application of recoverin as a potential target for immunotherapy of cancer is discussed.

Mitofilin and titin as target antigens in melanoma-associated retinopathy

Melanoma-associated retinopathy (MAR) is a rare paraneoplastic syndrome in patients with melanoma. Since the onset of MAR symptoms is often associated with tumor progression or recrudescence of metastases, MAR-related symptoms are prognostic relevant. The pathomechanism underlying MAR is supposed to result from antibody production against yet unknown melanoma-associated antigens that are also expressed in retinal tissue, leading to the destruction of retinal cells and resulting in defective signal transduction. Only a 35 kDa protein in Müller glial cells, a 22 kDa neuronal antigen and retinal transducin have been identified as MAR-associated antigens to date. To identify additional antigens potentially involved in the pathogenesis of MAR, we screened a retina cDNA phage library for reactivity with antibodies in the sera from 9 patients with MAR or subclinical MAR using the serological analysis of recombinantly expressed clones (SEREX) approach. Six sera from melanoma patients without evidence of MAR and 10 sera from healthy donors served as controls. Mitofilin and titin were identified as antigens against which antibodies were found exclusively in sera of MAR patients, but not in the sera of MM patients without MAR or healthy donors. This is the first study to demonstrate that titin is highly expressed from retinal tissue and melanoma. The fact that none of the MAR-associated antigens detected to date by their capacity to elicit a humoral immune response is located on the cell surface questions a major pathogenetic role of the respective antibodies and suggests that cellular, rather than humoral mechanisms are operative in the primary immune attack against the retina in MAR.

Paraneoplastic syndromes affecting the nervous system

The paraneoplastic neurologic disorders (PND) are a diverse group of diseases characterized by the presence of neurologic dysfunction in the setting of a remote cancer. PND can affect almost any part of the nervous system, and are most commonly associated with lung cancer (small cell) and gynecologic tumors. Laboratory studies have demonstrated that an autoimmune response links the neurologic disorder and the cancer, and established a model whereby the cancer is believed to initiate the syndrome by expressing a protein antigen normally expressed in the nervous system, leading to anti-tumor immune response followed by autoimmune neurologic symptoms. We review the currently known PND and their pathogenesis.