Identification of Cancer Antigens in Breast Cancer by the SEREX Expression Cloning Method

Autoantibodies as biomarkers for breast cancer diagnosis and prognosis

Breast cancer is the most common cancer in women worldwide and is a substantial public health problem. Screening for breast cancer mainly relies on mammography, which leads to false positives and missed diagnoses and is especially non-sensitive for patients with small tumors and dense breasts. The prognosis of breast cancer is mainly classified by tumor, node, and metastasis (TNM) staging, but this method does not consider the molecular characteristics of the tumor. As the product of the immune response to tumor-associated antigens, autoantibodies can be detected in peripheral blood and can be used as noninvasive, presymptomatic, and low-cost biomarkers. Therefore, autoantibodies can provide a possible supplementary method for breast cancer screening and prognosis classification. This article introduces the methods used to detect peripheral blood autoantibodies and the research progress in the screening and prognosis of breast cancer made in recent years to provide a potential direction for the examination and treatment of breast cancer.

Autoantibodies in Early Detection of Breast Cancer

In spite of the progress made in treatment and early diagnosis, breast cancer remains a major public health issue worldwide. Although modern image-based screening modalities have significantly improved early diagnosis, around 15% to 20% of breast cancers still go undetected. In underdeveloped countries, lack of resources and cost concerns prevent implementing mammography for routine screening. Noninvasive, low-cost, blood-based markers for early breast cancer diagnosis would be an invaluable alternative that would complement mammography screening. Tumor-specific autoantibodies are excellent biosensors that could be exploited to monitor disease-specific changes years before disease onset. Although clinically informative autoantibody markers for early breast cancer screening have yet to emerge, progress has been made in the development of tools to discover and validate promising autoantibody signatures. This review focuses on the current progress toward the development of autoantibody-based early screening markers for breast cancer.See all articles in this CEBP Focus section, "NCI Early Detection Research Network: Making Cancer Detection Possible."

Tumor-associated antigens identified early in mouse mammary tumor development can be effective vaccine targets

Breast cancer vaccines composed of antigens identified by serological analysis of cDNA expression libraries (SEREX) induce antigen specific immune responses in patients but have had disappointing clinical benefits. While many attempts to modify the adjuvants and vaccine method have been tried, one issue not addressed was whether the SEREX tumor-associated antigens identified from late stages of disease were ideal targets. We questioned in the transgenic TgMMTV-neu mouse model whether the antigen repertoire is distinct between early and late stage breast cancer and whether the antigens identified via SEREX from transgenic mice with early or late stage tumors would elicit differential anti-tumor effects to address this question. Three early stage antigens, Pdhx, Stk39, and Otud6B, were identified from a SEREX screen of mice prior to development of palpable lesions. Formulated into a vaccine, each early antigen inhibited tumor growth (p < 0.0001). The antigens identified from mice with late stage tumors (Swap70, Gsn, and Arhgef2) were unable to inhibit tumor growth when used as vaccines (for example Gsn p = 0.26). Each of the three early stage antigens were essential for tumor survival in syngeneic mouse tumor cells and in human breast cancer cell lines across breast cancer subtypes. Silencing protein expression of the early antigens increased apoptosis (p < 0.0001 for all antigens in mouse and p < 0.05 for all antigens in human triple negative breast cancer) and decreased survival (p < 0.0001 for all antigens in mouse and human triple negative and HER2 positive breast cancer). Overexpression of the early stage antigens in women with breast cancer predicted worse prognosis (p = 0.03) while overexpression of late stage antigens did not impact prognosis (p = 0.09). These data suggest that antigens expressed earlier in breast tumor development and functionally relevant to breast tumor growth may be more effective targets for therapeutic breast cancer vaccines than antigens identified in later disease.

Immunoproteomics Methods and Techniques

The varied landscape of the adaptive immune response is determined by the peptides presented by immune cells, derived from viral or microbial pathogens or cancerous cells. The study of immune biomarkers or antigens is not new, and classical methods such as agglutination, enzyme-linked immunosorbent assay, or Western blotting have been used for many years to study the immune response to vaccination or disease. However, in many of these traditional techniques, protein or peptide identification has often been the bottleneck. Recent progress in genomics and mass spectrometry have led to many of the rapid advances in proteomics approaches. Immunoproteomics describes a rapidly growing collection of approaches that have the common goal of identifying and measuring antigenic peptides or proteins. This includes gel-based, array-based, mass spectrometry-based, DNA-based, or in silico approaches. Immunoproteomics is yielding an understanding of disease and disease progression, vaccine candidates, and biomarkers. This review gives an overview of immunoproteomics and closely related technologies that are used to define the full set of protein antigens targeted by the immune system during disease.

Cancer-testis antigens: Unique cancer stem cell biomarkers and targets for cancer therapy

Cancer-testis antigens (CTAs) are considered as unique and promising cancer biomarkers and targets for cancer therapy. CTAs are multifunctional protein group with specific expression patterns in normal embryonic and adult cells and various types of cancer cells. CTAs are involved in regulating of the basic cellular processes during development, stem cell differentiation and carcinogenesis though the biological roles and cell functions of CTA families remain largely unclear. Analysis of CTA expression patterns in embryonic germ and somatic cells, pluripotent and multipotent stem cells, cancer stem cells and their cell descendants indicates that rearrangements of characteristic CTA profiles (aberrant expression) could be associated with cancer transformation and failure of the developmental program of cell lineage specification and germ line restriction. Therefore, aberrant CTA profiles can be used as panels of biomarkers for diagnoses and the selection of cancer treatment strategies. Moreover, immunogenic CTAs are prospective targets for cancer immunotherapy. Clinical trials testing broad range of cancer therapeutic vaccines against antigens of MAGEA and NY-ESO-1 families for treating various cancers have shown mixed clinical efficiency, safety and tolerability, suggesting the requirement of in-depth research of CTA expression in normal and cancer stem cells and extensive clinical trials for improving cancer immunotherapy technologies. This review focuses on recent advancement in study of CTAs in normal and cancer cells, particularly in normal and cancer stem cells, and provides a new insight into CTA expression patterns during normal and cancer stem cell lineage development. Additionally, new approaches in development of effective CTA-based therapies exclusively targeting cancer stem cells will be discussed.

Novel serum autoantibodies against talin1 in multiple sclerosis: Possible pathogenetic roles of the antibodies

In the pathogenesis of multiple sclerosis (MS), B cell/antibody-related mechanisms have recently received attention. To investigate the role of autoantibody in MS, we performed SEREX which can identify autoantibody cyclopedically. We identified serum antibodies against cytoskeletal protein talin1, and the levels of whom were remarkably higher in 39 MS than 43 normal controls (P < 0.01) and 35 disease controls (P = 0.06), and in MS patients without oligoclonal bands than ones with them. Moreover, we found negative-correlations between serum anti-talin1 antibody and IgG index in MS (P = 0.03). Anti-talin1 antibody exists in MS patients' sera, which may have some protective factor.

Immunoproteomics: current technology and applications

The varied landscape of the adaptive immune response is determined by the peptides presented by immune cells, derived from viral or microbial pathogens or cancerous cells. The study of immune biomarkers or antigens is not new and classical methods such as agglutination, enzyme-linked immunosorbent assay, or Western blotting have been used for many years to study the immune response to vaccination or disease. However, in many of these traditional techniques, protein or peptide identification has often been the bottleneck. Recent advances in genomics and proteomics, has led to many of the rapid advances in proteomics approaches. Immunoproteomics describes a rapidly growing collection of approaches that have the common goal of identifying and measuring antigenic peptides or proteins. This includes gel based, array based, mass spectrometry, DNA based, or in silico approaches. Immunoproteomics is yielding an understanding of disease and disease progression, vaccine candidates, and biomarkers. This review gives an overview of immunoproteomics and closely related technologies that are used to define the full set of antigens targeted by the immune system during disease.

Advances in understanding the role of metallopanstimulin-1 in tumors

Metallopanstimulin-1 (MPS-1), belonging to the ribosomal protein S27E family, is ubiquitously expressed in all normal tissues except the brain and placenta. In addition, MPS-1 is highly expressed in malignant tumors and cells. MPS-1 as a tumor marker or tumor-associated antigen has been extensively studied in head and neck cancer and breast cancer. MPS-1 is highly expressed in gastric cancer. Knockdown of MPS-1 expression inhibits the growth of cancer cells both in vitro and in vivo and induces spontaneous apoptosis of gastric cancer cells by repressing the NF-κB signaling pathway. In addition, MPS-1 is also highly expressed in colonic cancer and has a close relationship with the degree of malignancy and prognosis. Therefore, MPS-1 may be a novel potential therapeutic target for cancers.

Cancer/testis (CT) antigens: potential targets for immunotherapy

Cancer/testis (CT) antigens are protein antigens with normal expression restricted to adult testicular germ cells, and yet are aberrantly activated and expressed in a proportion of various types of human cancer. At least a subset of this group of antigens has been found to elicit spontaneous humoral and cell-mediated immune responses in cancer patients, raising the possibility that these antigens could be cancer vaccine targets. More than 100 CT antigen genes have been reported in the literature, with approximately 30 being members of multigene families on the X chromosome, so-called CT-X genes. Most CT-X genes are expressed at the spermatogonia stage of spermatogenesis, and their functions are mostly unknown. In cancer, the frequency of CT antigen expression is highly variable among different tumor types, but is more often expressed in high-grade late-stage cases in general. Cancer vaccine trials based on CT antigens MAGE-A3 and NY-ESO-1 are currently ongoing, and these antigens may also play a role in antigen-specific adoptive T-cell transfer and in the immunomodulation approach of cancer therapy.

Identification of a novel prostate cancer-associated tumor antigen

BACKGROUND

The identification of antigens that distinguish cancer cells from normal cells is of major importance for the definition of therapeutic targets in human malignancies. Using sera from cancer patients, we have previously reported on the identification of immunologically recognized proteins that belong to the family of cancer testis antigens (CTAs).

METHODS

A normal testicular cDNA library was screened with pooled allogeneic sera from patients with prostate cancer using a modified SEREX approach. Subsequently we have identified and characterized a novel antigen, T21, with an expression pattern similar to that of CTAs. mRNA expression of T21 was determined using a panel of whole tissues and prostate cell lines using Q-RT-PCR. For laser microdissection, fresh prostate cancer and benign tissue was obtained using our novel validated harvesting technique. Protein expression and cellular localization of T21 were assessed in prostate cell lines using Western blotting, confocal microscopy and flow cytometry.

RESULTS

T21 showed tissue-restricted mRNA expression in gastric, kidney and prostate cancers, and in normal testis and prostate tissues. Following laser microdissection, T21 was significantly over-expressed in malignant compared to benign prostatic epithelium. We have demonstrated expression of T21 at the protein level and confocal microscopy on PC3 cells probed with a T21-monospecific antibody revealed cytoplasmic localization of T21 protein.

CONCLUSIONS

The highly restricted expression pattern of T21 makes it an attractive vaccine target for prostate cancer. Several CTAs reportedly induce cytotoxic T-lymphocyte responses, therefore it is reasonable to assume that T21 will be a valuable target for cancer immunotherapy.

The identification of human tumour antigens: Current status and future developments

The biggest challenge facing us today in cancer control and prevention is the identification of novel biomarkers for detection and improved therapeutic interventions to reduce mortality and morbidity rates. Biomarkers are important indicators to inform us of the physiological state of the cell at a specific time. It is now clear that malignant transformation occurs by changes in cellular DNA and protein expression with subsequent clonal proliferation of the altered cells. The affected genes and their expressed protein products or biomarkers are those involved in the normal growth and maintenance of the cancerous cells. These biomarkers could prove pivotal for the identification of early cancer and people at risk of developing cancer. Altered proteins or changes in gene expression in malignant cells may lead to the expression of tumour antigens recognised by host immune system. In this review we discuss current research into the molecular technologies making possible the global genomic-wide analysis of changes in DNA (genotyping), RNA expression (transcriptomics) and protein expression (proteomics) that have accelerated the rate of new biomarker/tumour antigen discovery. To gain a comprehensive understanding of the physiology and pathophysiology of cancer an approach that harmoniously integrates the various 'omic' platforms are key to unraveling the complexity 'needle-in-a-haystack' quality of biomarker/tumour antigen discovery.

Identification of tumor associated antigens recognized by IgG from tumor-infiltrating B cells of lung cancer: correlation between Ab titer of the patient's sera and the clinical course

We previously demonstrated that TIB recognize tumor antigens and produce antibodies against them. In the present study, we identified three tumor antigens recognized by TIB in lung cancer and evaluated whether changes in the antibody titer against these antigens correlated with the patient's clinical course. A lung cancer cell line, G603L, was established from a primary lung tumor of a patient, G603. Seven months later, adrenal metastasis was detected and surgically resected. The latter tumor was mildly infiltrated with B cells and xenotransplanted into SCID mice to obtain human IgG. A cDNA library was constructed from G603L and SEREX was carried out using TIB-derived IgG. The sero-reactive clones were sequenced and one of these antigens was revealed to be MAGE-B2 whereas the others were novel antigens. In the immuno-monitoring of the patient's sera, high antibody titer against MAGE-B2 was observed before operation and the titer decreased after resection of the primary tumor. It was elevated again at the time of adrenal metastasis, but then decreased after resection. The change in antibody titer against the second antigen was similar to MAGE-B2, and the antibody titer against the third antigen was low before the primary operation but increased at the time of recurrence. Our results suggest that TIB recognized tumor antigens and the antibody titers against these antigens were changed along with the patient's clinical course. Therefore, these antibodies could be used as tumor markers for the patient.

Identification of specific autoantigens in Sjögren's syndrome by SEREX

We carried out SEREX (serological analysis of antigens by recombinant cDNA expression cloning) using sera from patients with Sjögren's syndrome (SjS) and investigated the frequencies of autoantibodies against autoantigens identified by SEREX in the sera of healthy individuals (HI) and patients with SjS, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). IFI16 and two kelch-like proteins, KLHL12 and KLHL7, were found to be novel autoantigens in SjS by SEREX. A markedly high frequency of anti-IFI16 autoantibodies was observed in the sera of SjS (SjS, 70%; RA, 13%; SLE, 33%; HI, 0%). Interestingly, all serum samples from SjS demonstrated immunoreactivity against one or both of IFI16 and SS-B/La. The presence of autoantibodies against KLHL12 and KLHL7 in the sera was significantly specific to SjS (23% and 17%, respectively), as they were not detected in RA, SLE or HI. Furthermore, we confirmed that transcripts of these autoantigens were expressed preferentially in the salivary glands and immuno-privileged testes. Our results suggest these autoantigens may be useful as serological markers for the clinical diagnosis of SjS and may play a crucial role as organ-specific autoantigens in the aetiopathogenesis of SjS. This study warranted clinical evaluations of autoantibodies against IFI16, KLHL12 and KLHL7 in combination with anti-SS-B/La autoantibodies.

Identification of tumour antigens by serological analysis of cDNA expression cloning

The identification of antigens that distinguish normal cells from cancer cells is an important challenge in the field of tumour immunology and immunotherapy. The immunoscreening of cDNA expression libraries constructed from human tumour tissues with antibodies in sera from cancer patents (SEREX: serological identification of antigens by recombinant expression cloning) provides a powerful approach to identify immunogenic tumour antigens. To date, over 2,000 tumour antigens have been identified from a variety of malignancies using SEREX. These antigens can be classified into several categories, of which the cancer/testis (CT) antigens appear to be the most attractive candidates for vaccine development. The SEREX-defined tumour antigens facilitate the identification of epitopes (antigenic peptides) recognised by antigen-specific cytotoxic T lymphocytes (CTLs) and provide a basis for peptide vaccine and gene therapy in a wide variety of human cancers. Moreover, some of these antigens seem to play a functional role in the pathogenesis of cancer.

Expression of cancer/testis (CT) antigens in lung cancer

Cancer/testis (CT) antigens are considered promising candidates for vaccine-based immunotherapy. The aim of this study was to investigate which CT antigens should be targeted in immunotherapy of Japanese lung cancer. To determine the expression of 12 CT antigens in Japanese primary lung cancers and cell lines, a reverse-transcription polymerase chain reaction (RT-PCR) analysis was performed. Among 46 primary lung cancers, high expression rates were found for MAGE-3 (41%, 19/46), and SSX-4 (35%, 16/46). A similar pattern of CT antigen expression was observed in 29 lung cancer cell lines. The expression frequency of a certain CT antigen, namely NY-ESO-1, in Japanese cases was drastically different from that in Caucasians. Polyvalent CT antigen vaccine may be effective to increase the number of lung cancer patients eligible for cancer-specific immunotherapy. Vaccination with MAGE-3 and SSX-1 would cover 57% of all patients, with three antigens, MAGE-3, SSX-1, and MAGE-4, would cover 65%, and with four antigens, MAGE-3, SSX-1, MAGE-4 and SSX-4, would cover 70%. Simultaneous expression of two or more CT antigens was observed in 25/46 (54%) primary lung cancers and 18/29 (62%) lung cancer cell lines. Polyvalent CT antigen vaccines may be also effective to reduce a chance of emergence of antigen loss variants, thus preventing tumors from escaping from the immune system. For this purpose, vaccination with combinations of MAGE-3 with MAGE-6, SSX-4, MAGE-1 or BAGE may be effective for a quarter of Japanese lung cancer patients. In addition, in silico surveys of dbEST database were used for identification of new CT antigens. We identified a novel gene, TES101RP, expressed only in some small cell lung cancers (SCLC) and in testis, as confirmed by RT-PCR analysis.

Dendritic cells and tumor immunity

Researchers and clinicians have tried for decades to use the mechanisms of immunity for the fight against cancer. Early attempts aimed at the instrumentation of soluble immune mediators such as antibodies or cytotoxic proteins for the therapy of malignancies. Major improvements in understanding the induction and regulation of cellular immunity have now made it possible to generate effector cells in cancer patients which are specific for the neoplastic disease. At the beginning of every cellular immune reaction against cancers tumor antigens have to be presented to T cells in order to activate them and drive them into clonal expansion. This is done by antigen presenting cells, the most powerful of which is the dendritic cell (DC). While DC were hard to isolate initially, they can be generated in large numbers in vitro today and manipulated in multiple ways before given back to a patient to induce tumor immunity. Thus, a great amount of hope lies in the use of DC as inducers of tumor immunity. However, the first clinical studies, which have now been completed with only limited success make clear, that still a lot of open questions remain to be answered. This review tries to give an overview of this rapidly developing field, mentioning the major conceptual approaches and techniques, but also discussing important caveats. The next years will show whether we can improve our understanding of DC biology and the mechanisms of immune induction strongly enough to effectively employ DC for immunotherapy of cancer.