Identification Of Human Tumor Antigens Research Articles

Triosephosphate isomerase and peroxiredoxin 6, two novel serum markers for human lung squamous cell carcinoma

There is currently substantial interest in the identification of human tumor antigens for the diagnosis and immunotherapy of cancer. In our previous study, secretion character and up-regulation of triosephosphate isomerase were observed in lung squamous cell carcinoma, and autoantibodies against triosephosphate isomerase and peroxiredoxin 6 were detected in the sera from over 25% of patients, but in none of the healthy controls. In this study, peroxiredoxin 6 was also found at higher levels in the sera of the patients. Up-regulated triosephosphate isomerase and peroxiredoxin 6 were further validated by enzyme-linked immunosorbent assay in an additional 61 lung squamous cell carcinoma patients, 23 lung adenocarcinoma patients, 56 other types of carcinoma patients, 12 benign lung disease patients, and 59 healthy controls. We found that both triosephosphate isomerase and peroxiredoxin 6 were specifically elevated in lung squamous cell carcinoma sera compared with other groups, with the exception of peroxiredoxin 6 in lung adenocarcinoma patients. Positive correlation between triosephosphate isomerase and distant metastasis was found. At the cut-off point 0.221 (optical density value) on the receiver operating characteristic curve, triosephosphate isomerase could comparatively discriminate lung squamous cell carcinoma from healthy controls with a sensitivity of 65.6%, specificity 84.7%, and total accuracy 75%. For peroxiredoxin 6, at the cut-off point 0.151, it could discriminate the two groups with a sensitivity of 70.5%, specificity 62.7%, and total accuracy 65.8%. With both triosephosphate isomerase and peroxiredoxin 6, discriminant analysis results showed that 68.9% of the lung squamous cell carcinoma and 83.1% of healthy controls were correctly classified. We concluded that triosephosphate isomerase and peroxiredoxin 6 could be markers for lung squamous cell carcinoma.

Molecular pathological approaches to human tumor immunology

Research on human tumor immunology has greatly advanced in the past two decades. Many immunogenic tumor antigens have been identified, and some of these antigens entered in clinical trials. Consequently, it has been shown that these antigens can inhibit tumor growth in patients to some extent, indicating that they act as potent immunogenic therapeutic vaccines in cancer patients with malignancies originating from various tissues. These patients had antigen-specific cytotoxic T-lymphocyte (CTL) responses when assessed on tetramer, enzyme-linked immunospot (ELISPOT), T-cell clonotype and CTL induction efficiency. Thus, it has become clear that human tumor vaccines can evoke clinical and immunological anti-tumor responses in patients. The tumor regression effects of tumor vaccines, however, are generally low, and it is obvious that current vaccination protocols are generally too weak to provide substantial and satisfactory clinical benefits. This means that other drastic and more potent clinical and immunological protocols are required in cancer immunotherapy. To find such efficient protocols the basic immunological and biological properties of cancers must be investigated. In the present review the identification of human tumor antigens recognized on CTL and the clinical trials are introduced. Next, the most recent analysis of human cancer-initiating cell (cancer stem cell)-associated antigens is described. These antigens might be able to act as 'universal, general and fundamental' tumor antigens. Also present is the authors' recent study for increasing cross-presentation efficiency in dendritic cells and subsequent enhancement of human leukocyte antigen (HLA)-class I-restricted peptide antigenicity by using HSP90 and ORP150 molecular chaperones that act as endogenous Toll-like receptor ligands. In addition to the aforementioned manipulation of the positive loop of tumor immunity, it is necessary to regulate and intervene in the negative loop. In particular, the potential of the expression of HLA class I molecule regulation by epigenetic mechanisms will be discussed. Finally, the type of basic and clinical tumor immunology research highly required currently, and in the very near future, are described.

An experimental strategy for quantitative analysis of the humoral immune response to prostate cancer antigens using natural protein microarrays

The identification of human tumor antigens has potential utility in the diagnosis and treatment of cancers. We demonstrate here a complete strategy to profile immunoreactivity and identify tumor antigens from proteins derived from tumor cell lines. Microarrays of proteins produced from 2-D LC fractionation of prostate tumor cell-line lysates were used to profile immunoreactivity in the sera of prostate cancer patients and control subjects. Cancer-associated immunoreactivity to distinct groups of chromatography fractions was present in about 50% of the patients, with greater immunoreactivity present in patients with non-organ-confined cancer than in patients with organ-confined cancer. We grouped the immunoreactive fractions by similarities in elution order and patterns of immunoreactivity to guide and interpret the MS analysis of selected fractions, which was used to identify the proteins that may be responsible for the immunoreactivity. As a complementary method to further characterize and validate the immunoreactivity of the proteins identified by mass spectrometry, we demonstrate the use of focused microarrays of recombinant proteins. Disease-associated immunoreactivity was confirmed for one of the identified proteins, human Kallikrein 11. These results demonstrate a practical approach to screening, identifying, and validating immunoreactive proteins that could be applied to diverse studies on humoral immune responses.

Identification of Human Tumor Antigens by Serological Analysis of Recombinant cDNA Expression Libraries (SEREX)

The structural definition of human tumor antigens recognized by the autologous host has been a long-standing challenge in tumor immunology. The growing list of human tumor antigens recognized by autologous antibodies or cytotoxic T lymphocytes provides convincing evidence for immune recognition of cancer by the host of origin, as well as attractive targets for vaccine-based approaches to cancer therapy. In this regard, an approach called SEREX (serological analysis of recombinant cDNA expression libraries) has broad applicability to the analysis of the humoral immune response to cancer antigens. This method involves immunoscreening cDNA libraries prepared from tumor specimens with sera from cancer patients in order to identify gene products recognized by IgG antibody. Clones identified by SEREX can be directly sequenced, providing immediate structural definition of the antigenic target, and their expression profiles can be readily determined, providing information regarding their tissue distribution. Application of this technique has led to the discovery of a number of provocative tumor antigens.

Identification of human tumor antigens and its implications for diagnosis and treatment of cancer

Human tumor antigens recognized by T cells have been identified by means of various molecular biological and immunological methods, including cDNA expression cloning with patients' T cells and antibodies, cDNA subtraction using RDA and PCR differential display, systematic gene analysis such as DNA sequencing, CGH, DNA chip/microarray and SAGE, in vitro T cell induction and immunization of HLA transgenic mice. The identification of human tumor antigens has led to a better understanding of the nature of tumor antigens, anti-tumor immune responses in patients before and after immunotherapy, and tumor escape mechanisms. The information obtained from these researches has enabled us to develop and improve immunotherapy by attempting to overcome the identified problems, including intrinsically low immunogenicity of tumor antigens and several escape mechanisms, such as regulatory T cell induction. The existence of immunogenic unique antigens derived from genetic alterations in tumor cells, and the varied immunogenicity of shared tumor antigens among patients due to differing expression in tumor cells and immunoreactivity of patients, indicates that individualized immunotherapy should ideally be performed. The identified antigens will also be useful for development of diagnostic methods and molecular targeting therapy for cancer.

Identification of human tumor antigens recognized by T-cells and their use for immunotherapy.

Identification of human tumor antigens led to development of new immunotherapies for patients with cancer. Identification of T-cell epitopes allowed us to monitor antitumor T-cell responses quantitatively and qualitatively during immunotherapy as well as to develop more efficient immunotherapies with sufficient amounts of antigens in more immunogenic forms. Various immunotherapies, passive immunotherapies, including adoptive transfer of tumor reactive T-cells or allogeneic antigen-specific donor T-cells, and active immunization with identified tumor antigens or dendritic cells pulsed with tumor antigens are being evaluated in clinical trials. Although tumor regression has been observed in some patients, further improvement is required.

Exploitation of the B cell repertoire for the identification of human tumor antigens.

The screening of tumor-derived expression libraries for antigens that are detected by high-titer immunoglobulin G antibodies from the sera of patients with cancer using serological identification of antigens by recombinant expression cloning (SEREX) allows for the systematic search for antigens of human cancers. SEREX has led to the identification of a plentitude of new tumor antigens in many different tumor entities. These antigens, many of which are encoded by hitherto unknown genes, can be grouped into different classes. Serologically defined human tumor antigens facilitate the identification of antigenic peptides recognized by tumor-specific T lymphocytes, thus providing a molecular basis for polyvalent peptide-based and gene therapeutic vaccine strategies in a wide variety of human neoplasms. Finally, many of the antigens identified using SEREX seem to play a functional role in the pathogenesis of malignant disease.

Exploitation of the antibody repertoire of cancer patients for the identification of human tumor antigens.

The screening of tumor-derived expression libraries for antigens which are recognized by high titered IgG antibodies present in autologous sera of the cancer patients by SEREX (serological identification of antigens by recombinant expression cloning) allows for the systematic identification of antigens in human cancers. SEREX has led to the definition of a plentitude of new tumor antigens in many different tumor entities. The majority of the antigens are encoded by hitherto unknown genes and can be grouped into different classes of antigens. The abundance of serologically defined human tumor antigens is not only of relevance for tumor biology and serodiagnosis of cancer, but also facilitates the identification of proteins recognized by tumor specific T lymphocytes, thus providing a molecular basis for polyvalent peptide-based and gene-therapeutic vaccine strategies in a wide variety of human neoplasms.

Serological identification of human tumor antigens

Using the antibody repertoire of cancer patients for the systematic search for human tumor antigens, a plenitude of new human tumor antigens has been identified demonstrating that many human tumors elicit multiple immune responses in the autologous host. The abundance of serologically defined human tumor antigens facilitates the identification of T cell dependent antigens and provides a basis for peptide and gene therapy vaccine strategies in a wide variety of human cancers.

Vaccine Trials for the Clinician: Prospects for Tumor Antigens

Recent insights in antigen presentation, the identification of human tumor antigens, and the demonstration of MHC class-I-restricted cytotoxic T lymphocyte (CTL) recognition of peptides encoded by tumor antigen have renewed the interest and enthusiasm for the development of cancer vaccines. Melanoma serves as a paradigm of an immunogenic human tumor, and several tumor antigens, including MAGE, MART-1/Melan-A and gp100, recognized by CTLs, have now been isolated. Candidate antigens for novel vaccine trials may include HLA class-I-binding tumor peptides that serve as CTL epitopes, whole tumor protein, or DNA-based vaccines. Requirements for the use of peptides are that the patient's tumor presents the relevant CTL epitopes as used in the vaccine and expresses the appropriate MHC class-I-restricting molecule. Immunological monitoring may be facilitated when using peptide-based vaccines. Because optimal presentation of tumor antigens may depend on provision of appropriate costimulatory signals, it may be more advantageous to administer professional antigen-presenting cells (APCs), such as dendritic cells (DCs) pulsed with tumor peptide or protein, to cancer patients. Developments in molecular genetics have led to a new approach in vaccines consisting of cancer cells genetically engineered to express immunomodulatory molecules. This may result in increased antitumor responses to both gene-modified as well as unmodified tumor cells. The therapeutic approach is extended to vaccination trials with recombinant viruses containing the genes encoding tumor antigens, minigenes containing multiple CTL epitopes, or double recombinant vectors engineered to express both the tumor antigen and immunostimulatory molecules. Clinical peptide, protein and DNA-based vaccine trials have recently been initiated. Thus far, exciting clinical remissions were obtained in melanoma patients following vaccination with HLA-A1-binding MAGE-3 peptide and in B-cell lymphoma patients immunized with autologous DCs pulsed with anti-idiotype protein, i.e., the individual patient's unique tumor antigen. Also, following injection of foreign HLA-B7 DNA into cutaneous melanoma metastases, T-cell migration into treated lesions and enhanced cellular immunity at the site of the tumor were shown in some patients. These encouraging results suggest that effective new vaccines in cancer will be identified.

In vitro priming to tumor-associated proteins.

Cancer can be cured in mice by adoptive transfer of T cells specific for the malignant cells or by vaccination to tumor-specific antigens. The application of immunotherapy to the treatment of human cancer hinges on the identification of human tumor antigens to which specific immunity can be elicited.