A mutated beta-catenin gene encodes a melanoma-specific antigen recognized by tumor infiltrating lymphocytes

Persistence of multiple tumor-specific T-cell clones is associated with complete tumor regression in a melanoma patient receiving adoptive cell transfer therapy

The authors recently reported that adoptive immunotherapy with autologous tumor-reactive tumor infiltrating lymphocytes (TILs) immediately following a conditioning nonmyeloablative chemotherapy regimen resulted in an enhanced clinical response rate in patients with metastatic melanoma. These observations led to the current studies, which are focused on a detailed analysis of the T-cell antigen reactivity as well as the in vivo persistence of T cells in melanoma patient 2098, who experienced a complete regression of all metastatic lesions in lungs and soft tissues following therapy. Screening of an autologous tumor cell cDNA library using transferred TILs resulted in the identification of novel mutated growth arrest-specific gene 7 (GAS7) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene transcripts. Direct sequence analysis of the expressed T-cell receptor beta chain variable regions showed that the transferred TILs contained multiple T-cell clonotypes, at least six of which persisted in peripheral blood for a month or more following transfer. The persistent T cells recognized both the mutated GAS7 and GAPDH. These persistent tumor-reactive T-cell clones were detected in tumor cell samples obtained from the patient following adoptive cell transfer and appeared to be represented at higher levels in the tumor sample obtained 1 month following transfer than in the peripheral blood obtained at the same time. Overall, these results indicate that multiple tumor-reactive T cells can persist in the peripheral blood and at the tumor site for prolonged times following adoptive transfer and thus may be responsible for the complete tumor regression in this patient.

AIM-2: a novel tumor antigen is expressed and presented by human glioma cells

Antigen isolated from Immunoselected Melanoma-2 (AIM-2) was recently identified using melanoma-reactive CD8 T cells. AIM-2 antigen is expressed in a wide variety of tumor types, including neuroectodermal tumors, as well as breast, ovarian and colon carcinomas. In this study, we analyzed AIM-2 expression in glioblastoma multiforme (GBM) in primary cultured cells and established GBM cell lines. We found that the primary GBM cell lines expressed 88.4% and 93.0% of non-spliced and spliced AIM-2, respectively. Five out of seven of the established GBM cell lines expressed both non-spliced and spliced AIM-2. Furthermore, the C9 CTL clone, which is specific for AIM-2 peptide (RSDSGQQARY), efficiently recognized GBM tumor cells in an antigen-specific and HLA-A1 restricted manner. IFN-gamma treatment of the GBM tumor cells dramatically increased HLA-A1 expression levels and, consequently, increased CTL recognition of the treated tumor cells. More importantly, seven out of 12 HLA-A1 and AIM-2 positive patients from our dendritic cell clinical trial generated AIM-2 specific CTL activity in their PBMC after vaccinations. These data indicate that AIM-2 could be used as a tumor antigen target for monitoring vaccine trials or to develop antigen specific active immunotherapy for glioma patients.

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.

T cells associated with tumor regression recognize frameshifted products of the CDKN2A tumor suppressor gene locus and a mutated HLA class I gene product

The dramatic tumor regression observed following adoptive T cell transfer in some patients has led to attempts to identify novel Ags to understand the nature of these responses. Nearly complete regression of multiple metastatic melanoma lesions was observed in patient 1913 following adoptive transfer of autologous tumor-infiltrating lymphocytes. The autologous 1913 melanoma cell line expressed a mutated HLA-A11 class I gene product that was recognized by the bulk tumor-infiltrating lymphocytes as well as a dominant T cell clone derived from this line. A second dominant T cell clone, T1D1, did not recognize the mutated HLA-A11 product, but recognized an allogeneic melanoma cell line that shared expression of HLA-A11 with the parental tumor cell line. Screening of an autologous melanoma cDNA library with clone T1D1 T cells in a cell line expressing the mutated HLA-A11 gene product resulted in the isolation of a p14ARF transcript containing a 2-bp deletion in exon 2. The T cell epitope recognized by T1D1, which was encoded within the frameshifted region of the deleted p14ARF transcript, was also generated from frameshifted p14ARF or p16INK4a transcripts that were isolated from two additional melanoma cell lines. The results of monitoring studies indicated that T cell clones reactive with the mutated HLA-A11 gene product and the mutated p14ARF product were highly represented in the peripheral blood of patient 1913 1 wk following adoptive transfer, indicating that they may have played a role in the nearly complete tumor regression that was observed following this treatment.

Identification of an SSX-2 epitope presented by dendritic cells to circulating autologous CD4+ T cells

Accumulating evidence supports the requirement for both tumor-specific CD8(+) and CD4(+) T cell responses for efficient tumor rejection to occur. Because of its expression in different tumor types, the cancer/testis Ag encoded by the synovial sarcoma X breakpoint 2 (SSX-2) gene is among the most relevant candidates for the development of generic cancer vaccines. The immunogenicity of SSX-2 has been previously corroborated by detection of specific humoral and CD8(+) T cell responses in cancer patients. In this study we report identification of the first CD4(+) T cell epitope encoded by SSX-2. The identified epitope mapped to the 19-34 region of the protein and was recognized by CD4(+) T cells from an Ag-expressing melanoma patient in association with HLA-DPB1*0101. The absence of detectable response in healthy donors and other patients suggests that SSX-2-specific CD4(+) T cells in the responder patient had been previously expanded in vivo in response to the autologous tumor. The epitope did not appear to be presented on the surface of tumor cells at levels sufficient to allow direct recognition. In contrast, it was efficiently presented by autologous dendritic cells, supporting the concept that processing by professional APC is the main pathway through which the CD4(+) T cell immunoresponse to tumor Ags occurs in vivo.

Evaluation of melanoma vaccines with molecularly defined antigens by ex vivo monitoring of tumor-specific T cells

Immunotherapy of melanoma is aimed to mobilize cytolytic CD8+ T cells playing a central role in protective immunity. Despite numerous clinical vaccine trials, only few patients exhibited strong antigen-specific T-cell activation, stressing the need to improve vaccine strategies. For a rational development, we propose to focus on molecularly defined vaccine components, and evaluate their immunogenicity with highly reproducible and standardized methods for ex vivo immune monitoring. Careful immunogenicity comparison of vaccine formulations in phase I/II studies allow to select optimized vaccines for subsequent clinical efficacy testing in large scale phase III trials.

A phase I trial of cytotoxic T-lymphocyte precursor-oriented peptide vaccines for colorectal carcinoma patients

In most protocols of peptide-based vaccination, no consideration has been paid to whether or not peptide-specific cytotoxic T-lymphocyte (CTL) precursors are pre-existent in cancer patients. Initiation of immune boosting through vaccination is better than that of immune priming to induce prompt and strong immunity. In this study, 10 human histocompatibility leukocyte antigen-A24⁺ patients with advanced colorectal carcinomas were treated with up to four peptides that had been positive for pre-vaccination measurement of peptide-specific CTL precursors in the circulation (CTL precursor-oriented peptide vaccine). No severe adverse effect was observed, although local pain and fever of grade I or II were observed. Post-vaccination peripheral blood mononuclear cells (PBMCs) from five patients demonstrated an increased peptide-specific immune response to the peptides. Increased CTL response to cancer cells was detected in post-vaccination PBMCs of five patients. Antipeptide immunoglobulin G became detectable in post-vaccination sera of seven patients. Three patients developed a positive delayed-type hypersensitivity response to at least one of the peptides administrated. One patient was found to have a partial response; another had a stable disease, sustained through 6 months. These results encourage further development of CTL precursor-oriented vaccine for colorectal cancer patients.

[Development of immunotherapy for cancer: lessons from melanoma research]

Identification of human melanoma antigens by various molecular biological and immunological techniques and evaluation of tumor reactive T cells in patients with the identified tumor antigen and HLA tetramer technology, not only provided us more profound understanding of anti-tumor immune responses in human, but also led to reveal basic problems in each step towards immunological tumor rejection, including systemic suppressive mechanisms such as regulatory T cell induction and local inhibitory environment in tumors. Based on these results obtained from the basic and clinical researches, various improvements have been applied for immunotherapy, including active immunization with modified antigenic peptides and recombinant virus, T cell adoptive transfer with lymphodepletive pretreatment, and administration of anti-CTLA-4 Ab, although further improvement is necessary. The translational research performed on melanoma, would facilitate development of immunotherapy for other cancers.

Tumor antigens for cancer immunotherapy: therapeutic potential of xenogeneic DNA vaccines

Preclinical animal studies have convincingly demonstrated that tumor immunity to self antigens can be actively induced and can translate into an effective anti-tumor response. Several of these observations are being tested in clinical trials. Immunization with xenogeneic DNA is an attractive approach to treat cancer since it generates T cell and antibody responses. When working in concert, these mechanisms may improve the efficacy of vaccines. The use of xenogeneic DNA in overcoming immune tolerance has been promising not only in inbred mice with transplanted tumors but also in outbred canines, which present with spontaneous tumors, as in the case of human. Use of this strategy also overcomes limitations seen in other types of cancer vaccines. Immunization against defined tumor antigens using a xenogeneic DNA vaccine is currently being tested in early phase clinical trials for the treatment of melanoma and prostate cancers, with proposed trials for breast cancer and Non-Hodgkin's Lymphoma.

Development of immunotherapy for pancreatic cancer

: Human tumor antigens recognized by T cells have been recently identified in various cancers, including pancreatic cancer. With the identified antigens, new immunotherapies can be developed using more efficient immunologic intervention (due to sufficient amounts of antigens in a more immunogenic form), as well as more quantitative and qualitative immunomonitoring. Various immunotherapies for patients with various cancers, including pancreatic cancer, are currently under evaluation in clinical trials. These include adoptive transfer of tumor reactive T cells and LAK cells; nonmyeloablative stem cell transplantation; active immunization with the identified tumor antigens, various tumor-derived products, dendritic cells pulsed with tumor antigens, and gene-modified tumor cells. Although these efforts in the realm of pancreatic cancer are still limited, various groups in Japan continue to be actively involved in this field of research.

Mutant α-actinin-4 promotes tumorigenicity and regulates cell motility of a human lung carcinoma

The precise role of alpha-actinin-4 encoding gene (ACTN4) is not very well understood. It has been reported to elicit tumor suppressor activity and to regulate cellular motility. To further assess the function of human ACTN4, we studied a lung carcinoma cell line expressing a mutated alpha-actinin-4, which is recognized as a tumor antigen by autologous CD8(+) cytotoxic T lymphocytes (CTL). Confocal immunofluorescence microscopy indicated that, while wild-type (WT) alpha-actinin-4 stains into actin cytoskeleton and cell surface ruffles, the mutated protein is only dispersed in the cytoplasm of the lung carcinoma cells. This loss of association with the cell surface did not appear to correlate with a decrease in in vitro alpha-actinin-4 crosslinking to filamentous (F)-actin. Interestingly, experiments using cell lines stably expressing ACTN4 demonstrated that as opposed to WT gene, mutant ACTN4 was unable to inhibit tumor cell growth in vitro and in vivo. Moreover, the expression of mutant alpha-actinin-4 resulted in the loss of tumor cell capacity to migrate. The identification of an inactivating mutation in ACTN4 emphasizes its role as a tumor suppressor gene and underlines the involvement of cytoskeleton alteration in tumor development and metastasis.

Differential quantitative analysis of MHC ligands by mass spectrometry using stable isotope labeling

Currently, no method allows direct and quantitative comparison of MHC-presented peptides in pairs of samples, such as transfected and untransfected, tumorous and normal or infected and uninfected tissues or cell lines. Here we introduce two approaches that use isotopically labeled reagents to quantify by mass spectrometry the ratio of peptides from each source. The first method involves acetylation and is both fast and simple. However, higher peptide recoveries and a finer sensitivity are achieved by the second method, which combines guanidination and nicotinylation, because the charge state of peptides can be maintained. Using differential acetylation, we identified a beta catenin-derived peptide in solid colon carcinoma overpresented on human leucocyte antigen-A (HLA-A)(*)6801. Guanidination/nicotinylation was applied to keratin 18-transfected cells and resulted in the characterization of the peptide RLASYLDRV (HLA-A(*)0201), exclusively presented on the transfectant. Thus, we demonstrate methods that enable a pairwise quantitative comparison leading to the identification of overpresented MHC ligands.

Identification of tumor antigens and T-cell epitopes, and its clinical application

The capability of antigen-specific CD8(+) and CD4(+) T lymphocytes to mediate antitumor immunity has generated remarkable interest in the identification of target antigens and their epitopes. The classical strategy to define tumor antigens is based on the employment of in vivo sensitized tumor-reactive T lymphocytes from cancer patients. These lymphocytes are used to screen an autologous tumor cDNA expression library for the target antigen. Alternatively, antibodies from the serum of cancer patients can be applied to screen a tumor-derived phage expression library for immunogenic cellular structures. In addition, potential target antigens have been selected by gene expression profiling searching for overexpressed gene products in neoplastic cells compared with normal tissues. B-cell target structures and overexpressed gene products have to be verified as T-cell antigens by the strategy of "reverse immunology." Therefore, T cells are sensitized in vitro by autologous dendritic cells loaded with predicted antigenic peptide ligands for a given HLA allele or with the global antigen. These different approaches led to the identification of a still growing number of antigenic peptides providing the basis for the development of new active and passive immunotherapies and for the monitoring of spontaneous and vaccine-induced T-cell responses. Some of these antigens and/or their epitopes are now validated in different clinical regimens for their capability to mediate potent T-cell immunity in cancer patients.

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.

A gene expressed exclusively in acute B lymphoblastic leukemias

Representational difference analysis, a cDNA subtraction approach, was used to identify genes that are expressed in acute leukemia but not in normal hematological tissues. We isolated a cDNA fragment from a cell line derived from a B cell acute lymphoblastic leukemia bearing two Philadelphia chromosomes. The cDNA derives from an orphan gene that was named BLACE. BLACE is located in region 7q36 and encodes a major 5.3-kb transcript and several alternatively spliced minor transcripts. Significant expression of BLACE was detected by RT-PCR and quantitative RT-PCR in bone marrow samples from B cell acute lymphoblastic leukemia patients. BLACE was not or was scarcely expressed in other types of hematological malignancies, in normal tissues, and in solid tumors.

A3 adenosine receptor activation in melanoma cells: association between receptor fate and tumor growth inhibition

Activation of the Gi protein-coupled A3 adenosine receptor (A3AR) has been implicated in the inhibition of melanoma cell growth by deregulating protein kinase A and key components of the Wnt signaling pathway. Receptor activation results in internalization/recycling events that play an important role in turning on/off receptor-mediated signal transduction pathways. Thus, we hereby examined the association between receptor fate, receptor functionality, and tumor growth inhibition upon activation with the agonist 1-deoxy-1-[6-[[(3-iodophenyl)-methyl]amino]-9H-purine-9-yl]-N-methyl-beta-D-ribofuranuronamide (IB-MECA). Results showed that melanoma cells highly expressed A3AR on the cell surface, which was rapidly internalized to the cytosol and "sorted" to the endosomes for recycling and to the lysosomes for degradation. Receptor distribution in the lysosomes was consistent with the down-regulation of receptor protein expression and was followed by mRNA and protein resynthesis. At each stage, receptor functionality was evidenced by the modulation in cAMP level and the downstream effectors protein kinase A, glycogen synthase kinase-3beta, c-Myc, and cyclin D1. The A3AR antagonist MRS 1523 counteracted the internalization process as well as the modulation in the expression of the signaling proteins, demonstrating that the responses are A3AR-mediated. Supporting this notion are the in vivo studies showing tumor growth inhibition upon IB-MECA treatment and reverse of this response when IB-MECA was given in combination with MRS 1523. In addition, in melanoma tumor lesions derived from IB-MECA-treated mice, the expression level A3AR and the downstream key signaling proteins were modulated in the same pattern as was seen in vitro. Altogether, our observations tie the fate of A3AR to modulation of downstream molecular mechanisms leading to tumor growth inhibition both in vitro and in vivo.

Identification of a colorectal tumor-associated antigen (COA-1) recognized by CD4(+) T lymphocytes

Only a limited number of target molecules have been shown to be recognized by colon tumor-reactive T cells, limiting the options for the development of immunotherapies for patients with colon cancer. The current studies were undertaken in an attempt to generate tumor-reactive T cells that could be used to identify and characterize novel colon tumor-associated antigens. Multiple CD4(+) T-cell clones isolated either from tumor-infiltrating lymphocytes or peripheral blood mononuclear cells that were sensitized in vitro with autologous tumor cells from a colon cancer patient, 1869, recognized autologous tumor cells in a class II HLA-DR-restricted manner. One of the peripheral blood mononuclear cell clones, clone C111, was used to screen pools of clones that were generated from an autologous colon tumor cell line cDNA library. A cDNA clone that was isolated encoded a protein that was termed colorectal tumor-associated antigen-1 (COA-1). This product was recognized in the context of the two autologous HLA-DRbeta1 alleles, HLA-DRbeta1*0402 and DRbeta1*1301. The nucleotide sequence of the COA-1 transcript was nearly identical to multiple expressed sequence tag sequences that encode variants of Socius, a protein that was found recently to bind to members of the Rnd family of GTPases. The COA-1 gene was expressed at relatively comparable levels in colorectal and melanoma tumor cells, EBV-infected B cells, normal B cells, and cultured fibroblast cell lines. However, the gene that was isolated from normal cell types contained a single nucleotide substitution, resulting in an amino acid change near the COOH terminus of the protein. Although the minimal epitope recognized by CD4(+) cells was encoded by sequences that were upstream from this substitution, C111 T cells did not appear to recognize the normal gene product. Therefore, this alteration may either affect the localization or the processing of this gene product, which may at least in part be responsible for the differential recognition of tumor and normal cells.

Adoptive-cell-transfer therapy for the treatment of patients with cancer

Adoptive immunotherapy--the isolation of antigen-specific cells, their ex vivo expansion and activation, and subsequent autologous administration--is a promising approach to inducing antitumour immune responses. The molecular identification of tumour antigens and the ability to monitor the persistence and transport of transferred cells has provided new insights into the mechanisms of tumour immunotherapy. Recent studies have shown the effectiveness of cell-transfer therapies for the treatment of patients with selected metastatic cancers. These studies provide a blueprint for the wider application of adoptive-cell-transfer therapy, and emphasize the requirement for in vivo persistence of the cells for therapeutic efficacy.

The Wnt signaling pathway in solid childhood tumors

The Wnt signaling pathway has long been known to direct growth and patterning during embryonic development. Recent evidence also implicates this pathway in the development of childhood tumors of the liver, the kidney, the brain, and the pancreas. Here, we review the current evidence on how constitutive activation of the Wnt signaling pathway may occur in hepato-, nephro-, medullo- and pancreatoblastomas. With particular emphasis the mutational activation of CTNNB1, an emerging major oncogene in solid childhood tumors, is discussed.

Molecular and functional analysis of tyrosinase-related protein (TRP)-2 as a cytotoxic T lymphocyte target in patients with malignant glioma

Tyrosinase-related protein (TRP)-2 is an immunogenic antigen in melanoma. The authors sought to investigate whether TRP-2 could be a potential target for patients with malignant glioma. RT-PCR analysis demonstrated that TRP-2 was present in 51.2% of primary tumor cell lines derived from patients with glioblastoma multiforme (GBM). The percentage of TRP-2-6b, TRP-2-INT2, TRP-2-LT, and TRP-2-8b isoform expression in all tested GBM cells was 13.9%, 34.9%, 41.9%, and 39.5%, respectively. TRP-2 protein expression was detected in GBM cells and tumor tissues by Western blot and immunohistochemistry. In addition, an HLA-A2-restricted cytotoxic T cell clone that recognizes the TRP-2(180-188) peptide (SVYDFFVWL) specifically lysed the TRP-2 positive GBM cells in a HLA-A2 restricted manner. In addition, the level of TRP-2 mRNA expression, as determined by real-time quantitative RT-PCR, correlated with the level of CTL recognition as measured by IFN-gamma secretion (R = 0.90; p < 0.01). To further test the immunogenicity of TRP-2 in glioma, PBMCs from a healthy donor were primed in vitro using autologous dendritic cells (DCs) pulsed with irradiated GBM cells. These in vitro generated T cells specifically lysed T2 cells pulsed with TRP-2(180-188) peptide and TRP-2 positive GBM cell lines. Most importantly, TRP-2(180-188) specific CTL frequency in four patients' PBMC who were both HLA-A2 and TRP-2 positive was significantly (p < 0.01) increased, respectively, after vaccinations with DCs pulsed with autologous tumor lysate. The authors' studies demonstrate that TRP-2 could be a useful antigen target for monitoring or developing immunotherapeutic strategies for glioma patients.

Identification of a mutated receptor-like protein tyrosine phosphatase kappa as a novel, class II HLA-restricted melanoma antigen

Recent studies increasingly point to a pivotal role of CD4(+) T cells in human anti-tumor immune response. Here we show that lymphocytes purified from a tumor-infiltrated lymph node of a melanoma patient that had remained disease free for 10 years after surgical resection of a lymph node metastasis comprised oligoclonal class II HLA-restricted CD4(+) T cells recognizing the autologous tumor cells in vitro. In fact, the CD4(+) T cell clones isolated from these lymphocytes displayed a tumor-specific, cytotoxic activity in addition to a Th1-like cytokine profile. By a genetic approach, a peptide derived from a mutated receptor-like protein tyrosine phosphatase kappa was identified as a novel HLA-DR10-restricted epitope for all the melanoma-specific CD4(+) T cell clones. The immunogenic peptide was shown to contain the mutated residue that was crucial for T cell recognition and activation. Moreover, a systemic immunity against the mutated peptide was detectable in the patient's peripheral blood T lymphocytes obtained during the disease-free period of follow-up. These findings further support the relevance of CD4(+) T cells directed against mutated epitopes in tumor immunity and provide the rationale for a possible usage of mutated, tumor-specific Ags for immunotherapy of human cancer.

Beta-catenin in the melanocyte lineage

beta-Catenin is a multifunctional protein involved in cell-cell adhesion, intracellular signalling and gene transcription. It has been implicated in the development of various lineages, including neural crest derivatives. Melanocytes are derived from neural crest cells and beta-catenin is expressed throughout the development of this cell lineage. The multifunctional activity of beta-catenin is directly associated with its participation in multi protein-protein interactions. The cell-cell adhesion function of beta-catenin is mediated by the large cadherin cell adhesion molecule family, the intracellular signalling function by its interaction with GSK3beta, and the gene transcription activity by the four known LEF/TCF DNA binding-proteins. Here, we review the known beta-catenin interacting factors and targets involved in the development and transformation of melanocytes and in particular its role in the expression of the crucial gene of melanocyte development, Mitf.

Immunological evaluation of CTL precursor-oriented vaccines for advanced lung cancer patients

Recent clinical trials of peptide vaccine for cancer patients have rarely resulted in tumor regression. One of the reasons for this failure could be an insufficient induction of anti-tumor responses in these regimens, in which peptide-specific memory cytotoxic T lymphocytes (CTLs) were not measured prior to vaccination. We investigated in this study whether pre-vaccination measurement of peptide-specific CTLs can provide any advantages in lung cancer patients receiving peptide vaccination with regard to safety and immunological responses. Ten patients with advanced lung cancer received vaccination with peptides under a regimen of CTL precursor-oriented vaccination, in which pre-vaccination peripheral blood mononuclear cells (PBMCs) were at first screened for reactivity in vitro to each of 14 peptides, followed by in vivo administration of only the reactive peptides. Profiles of the vaccinated peptides varied markedly among the 10 patients. This regimen was generally well-tolerated, although local skin reactions, diarrhea, and colitis were observed in 8, 2, and 1 patient, respectively. Increased CTL responses against the immunized peptides and tumor cells were observed in the post-vaccination PBMCs from 4 of 8 and 3 of 10 patients tested, respectively. Peptide-specific IgG became detectable in post-vaccination sera in 4 of 10 patients tested, and these 4 patients had a long progression-free survival. Furthermore, the median survival time of 9 patients with non-small cell lung cancer was 668.0 +/- 164.2 days. These results encourage further development of CTL precursor-oriented peptide vaccination for lung cancer patients.

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.

Immunity to melanoma: unraveling the relation of tumor immunity and autoimmunity

Cancer cells express self-antigens that are weakly recognized by the immune system. Even though responses against autologous cells are difficult to induce, the immune system is still able to mount a response against cancer. The discovery of the molecular identity of antigens that are recognized by the immune system of melanoma patients has led to the elucidation of tumor immunity at a cellular and molecular level. Multiple pathways in both the priming and effector phases of melanoma rejection have been described. Animal models' active immunotherapies for melanoma show a requirement for the cellular compartment of the immune system in the priming phase, primarily CD4+T cells. More diverse elements are required for the effector phase, including components from the innate immune system (macrophages, complement and/or natural killer cells) and from the adaptive immune system (CD8+T cells and B cells). Minor differences in amino-acid sequences of antigens must determine the particular mechanisms involved in tumor rejection. Since the immune system contains T and B cells that recognize and reject autologous cells, a consequence of tumor immunity is potential autoimmunity. There are distinct pathways for tumor immunity and autoimmunity. The requirements for autoimmunity at the priming phase seem to be CD4+/IFN-gamma dependent while the effector mechanisms are alternative and redundant. Vitiligo (autoimmune hypopigmentation) can be mediated by T cells, FcgammaR+macrophages and/or complement.

Analysis of a shared pancreatic cancer antigen recognized by an HLA-A*2601-restricted cytotoxic T-lymphocyte clone

INTRODUCTION

We have generated HLA-A*2601-restricted CD8+ CTL clones against an autologous pancreatic cancer cell line.

AIMS

To characterize the antigen expressed on the cancer cells.

METHODOLOGY

We assessed cytotoxic activities and cytokine production of these CTL clones reacting against cancer cell lines that stably or transiently expressed the HLA-A*2601 gene.

RESULTS

These CTL clones recognized 4 of 10 allogeneic pancreatic cancer cell lines and a gallbladder cancer cell line in the context of HLA-A*2601. However, the CTL clones did not recognize three hepatocellular carcinoma cell lines, two esophageal squamous cell carcinoma cell lines, or a lung adenocarcinoma cell line.

CONCLUSIONS

Thus, the CTL clones may recognize a shared, but not ubiquitously expressed, tumor antigen on pancreatic and gallbladder cancer cells.

Cancer/testis-associated genes: identification, expression profile, and putative function

Cancer/testis-associated genes (CTAs) are a subgroup of tumor antigens with a restricted expression in testis and malignancies. During the last decade, many of these immunotherapy candidate genes have been discovered using various approaches. Most of these genes are localized on the X-chromosome, often as multigene families. Methylation status seems to be the main, but not the only regulator of their specific expression pattern. In testis, CTAs are exclusively present in cells of the germ cell lineage, though there is a lot of variation in the moment of expression during different stages of sperm development. Likewise, there is also a lot of heterogeneity in the expression of CTAs in melanoma samples. Clues regarding functionality of CTAs for many of these proteins point to a role in cell cycle regulation or transcriptional control. Better insights in the function of these genes may shed light on the link between spermatogenesis and tumor growth and could be of use in anti-tumor therapies. This review outlines the CTA family and focuses on their expression and putative function during male germ cell development and melanocytic tumor progression.

Normal tissue depresses while tumor tissue enhances human T cell responses in vivo to a novel self/tumor melanoma antigen, OA1

Antitumor T cells often recognize targets that are nonmutated "self" tissue differentiation Ags, but the relative impact of Ag expression by normal and transformed tissue for a human self/tumor Ag has not been studied. To examine the influence of self-tolerance mechanisms on the function of self/tumor-specific T cell responses in humans, we sought to identify an Ag that was expressed, processed, and presented in an MHC-restricted fashion by tumor cells, but for which there was the human equivalent of a "knockout." In this study, we report the first immunological characterization of a melanoma/melanocyte differentiation Ag, called OA1, which meets these criteria. This Ag, an X chromosome-encoded melanoma/melanocyte differentiation Ag, was completely deleted in a male patient. Using a newly identified HLA-A*2402-restricted epitope (LYSACFWWL) to study T cell tolerance, we found that OA1-specific T cell reactivity was more than five SD higher in the knockout patient that in normal controls. These data provide compelling evidence for T cell tolerance to OA1 in humans. Most surprisingly, we found elevated levels of OA1-specific T cells in patients with metastatic malignant melanoma, indicating that the tumor-bearing state partially reversed tolerance observed in normal (non-"knockout") individuals. Taken together, these findings indicated that tolerance can exist for self/tumor Ags in humans, and that this tolerance could be partially abrogated by the growth of the tumor, increasing the reactivity of tumor Ag-specific T cells. Thus, the tumor-bearing state reverses, in part, the tolerance of T cells that results from the normal expression of tissue differentiation Ags.

Identification and characterization of a novel cancer/testis antigen gene CAGE-1

Serological analysis of cDNA expression library (SEREX) was employed to identify cancer-associated genes. By screening cDNA expression libraries with sera of patients with lung cancers, we identified a total of 49 genes that specifically reacted with the sera of patients with lung cancers. Among these, we characterized a novel gene with expression pattern similar to that of cancer/testis antigens. Its open reading frame is 1920 bp in size and encodes for putative protein composed of 639 amino acids. Southern blot analysis reveals that this gene exists as single copy. In vitro transcription/translation and Western blot analysis confirm that this gene encodes a protein of 73 kDa in size. The comparison of cDNA and genomic sequences reveals that it is composed of 11 exons and 10 introns. This gene displays testis-specific expression among normal tissues, and wide expression among various cancer tissues and cancer cell lines. A study using GFP fusion construct reveals mainly nuclear localization of CAGE-1 protein. The expression of this clone is relatively higher in cancer tissues compared with their surrounding non-cancerous tissues. This suggests that overexpression of CAGE-1 may be associated with the progression of tumor. Because of its association with cancer, this gene was named cancer-associated gene-1 (CAGE-1). Given the fact that several cancer/testis antigens reportedly induce cytolytic T lymphocyte (CTL) reactions, it is reasonable that this gene will be a valuable target for cancer immunotherapy. The exact functional role of CAGE-1 in tumorigenesis remains to be seen.

Identification of bladder cancer antigens recognized by IgG antibodies of a patient with metastatic bladder cancer

To identify tumor antigens useful for the diagnosis and treatment of patients with bladder cancer, a lambda phage cDNA library constructed from a high-grade bladder cancer cell line was screened with autologous serum from a patient with metastatic bladder cancer. Forty-eight distinct antigens were isolated. By evaluating the immunogenicity and the tissue-specific expression, KU-BL-1 and KU-BL-2 were identified as immunogenic antigens with restricted tissue expression. KU-BL-1 was found to be a putative human lipoic acid synthetase with a metal-binding site, CXXXCXXC, that was expressed in bladder cancer cell lines and most bladder cancer tissues, as well as normal bladder mucosa and testis tissues. Immunoglobulin (Ig)G antibody to KU-BL-1 was detected in 2 of 28 patients with bladder cancer, but not in 30 healthy individuals. KU-BL-2 was found to be a putative human kelch-like protein that was homologous to Drosophila kelch, with a BTB/POZ domain and kelch repeats. KU-BL-2 was expressed in bladder cancer cell lines, most bladder cancer tissues, testis and heart, but not in normal bladder mucosa. IgG antibody to KU-BL-2 was detected in 8 of 28 patients with bladder cancer, but not in 16 healthy individuals. Tumor reactive T cells were induced from peripheral blood mononuclear cells (PBMC) by stimulation with one of the HLA-A24 binding KU-BL-2 peptides. Therefore, KU-BL-1 and KU-BL-2, which showed preferential expression in bladder cancer with restricted expression in normal tissues, as well as immunogenicity in multiple patients with bladder cancer, may be useful for the development of diagnostic and therapeutic methods for patients with bladder cancer.

Nuclear accumulation of beta-catenin protein in Wilms' tumours

The wnt-signalling pathway plays an important role during both normal kidney development and Wilms' tumourigenesis. Activation of this pathway involves stabilization, intracellular accumulation, and nuclear translocation of the beta-catenin protein and may be caused by specific mutations in the beta-catenin gene itself. Such mutations have been found in about 15% of Wilms' tumours. This study has analysed the intracellular levels and subcellular distribution of beta-catenin protein in 36 primary Wilms' tumour specimens and has correlated these results with the mutational status of the beta-catenin gene. Immunohistochemistry detected faint cytoplasmic and strong membranous expression of beta-catenin protein in the epithelial compartment of all tumours examined. In contrast, nuclear immunoreactivity for beta-catenin was detected in 9 of 9 Wilms' tumours containing a mutation of the beta-catenin gene and in 15 of 27 Wilms' tumours without detectable beta-catenin mutation. Nuclear positivity, in each case, was found to be very strong, but was usually present only in a fraction of cells ranging from 5% to 10%. Among the different histological subcompartments, blastemal and mesenchymal cell nuclei preferentially stained positive, whereas cells of epithelial differentiation displayed nuclear localization of beta-catenin protein in only a single case. Furthermore, nuclear positive cells were found in Wilms' tumours of all stages and in tumours of both favourable and unfavourable histology. These data support the idea that activation of the wnt-signalling pathway is a key oncogenic step in Wilms' tumourigenesis and that it probably involves transcriptional activation of critical target genes, carried out by beta-catenin protein in the nucleus. The fact that nuclear immunoreactivity specific for beta-catenin was detected in a significant number of Wilms' tumours in the absence of beta-catenin mutations suggests that genetic defects affecting other members of the wnt-signalling pathway may contribute to the development of Wilms' tumours in those cases.

Melanoma vaccines

The identification of antigens on tumor cells has led to significant contributions to the field of immunotherapy. One of the most active areas under investigation in cancer immunotherapy is the development of vaccines against melanoma antigens. Induction of immunity against tumor antigens can follow multiple routes using different mechanisms. Crucial to the development of active immunization and other immunotherapies is the discovery and understanding of the molecular identity of antigens and the mechanisms involved in tumor immunity, as well as escape from immunity. In this review, we will discuss strategies to induce active immunity against melanoma.

Multiple HLA class II-restricted melanocyte differentiation antigens are recognized by tumor-infiltrating lymphocytes from a patient with melanoma

Dramatic clinical responses were observed in patient 888 following the adoptive transfer of autologous tumor-infiltrating lymphocytes (TIL). Previously, extensive analysis of the specificity of class I-restricted T cells from patient 888 TIL has revealed that these T cells recognize a mutated, as well as several nonmutated tumor Ags. Additional studies that were conducted on TIL from patient 888 indicated that they contained CD4-positive T cells that recognized the autologous tumor that had been induced to express HLA class II molecules. Tumor-reactive CD4-positive T cell clones were isolated from TIL and tested for their ability to react with Ags that are recognized by HLA class I-restricted, melanoma-reactive T cells. Using this approach, T cell clones were identified that recognized an epitope expressed in both the tyrosinase-related protein 1 and tyrosinase-related protein 2 Ags in the context of the HLA-DRbeta1*1502 class II gene product. Additional clones were found to recognize an epitope of gp100 in the context of the same HLA-DR restriction element. These observations provide an impetus to develop strategies directed toward generating HLA class II-restricted tumor-reactive T cells.

Melanoma vaccines

The incidence of malignant melanoma is increasing faster than that of any other malignancy in the United States, and therefore this disease represents a significant health threat now and in the future. The impact of conventional systemic therapy for metastatic melanoma is minimal, with best response rates for conventional therapy nearing only 30% and cure rates well below 10%. This justifies the development of immunotherapy as a new treatment modality for patients with melanoma. This review summarizes the most recent findings and the newest approaches in the design of vaccines for melanoma. The antigens associated with melanoma and their uses in the vaccine development are described. Possible clinical applications of the new vaccines for melanoma and future directions for their development are also discussed.

Antitumor cytotoxic T-lymphocyte response in human lung carcinoma: identification of a tumor-associated antigen

We have isolated several cytotoxic T lymphocyte (CTL) clones from lymphocytes infiltrating a lung carcinoma of a patient with long survival. These clones showed a CD3+, CD8+, CD4-, CD28- phenotype and expressed a T-cell receptor (TCR) encoded either by Vbeta8-Jbeta1.5 or Vbeta22-Jbeta1.4 rearrangements. Functional studies indicated that these clones mediated a high human leukocyte antigen (HLA)-A2.1-restricted cytotoxic activity against the autologous tumor cell line. Interestingly, TCRbeta chain gene usage indicated that CTL clones identified in vitro were selectively expanded in vivo at the tumor site as compared to autologous peripheral blood lymphocytes (PBL). These findings provide evidence that an immune response may take place in non-small cell lung carcinoma and that effector T cells may contribute to tumor regression. Further study indicated that the CTL clones recognized the same decamer peptide encoded by a mutated alpha-actinin-4 gene. Using tetramers of soluble HLA-A2 molecules loaded with the mutated antigenic peptide, we have derived several anti-alpha-actinin-4 T-cell clones from patient PBL. These CTL, recognizing a truly tumor-specific antigen, may play a role in the clinical evolution of this lung cancer patient. Adoptive transfer of CTL clones in a SCID/NOD mice model transplanted with autologous tumor supported their antitumor effect in vivo.

Immunity to cancer: attack and escape in T lymphocyte-tumor cell interaction

Tumor cells may express antigens which are recognized in a form of HLA/peptide complexes by T cells. The frequency at which different antigens are seen by T cells of melanoma patients and healthy donors was evaluated by human leukocyte antigen (HLA)/peptide tetramer technology which stains T cells bearing the specific receptor for a given epitope. By this technique, it was found that the majority of metastatic melanoma patients can recognize differentiation antigens (particularly Melan-A/MART-1), whereas such a recognition is scanty in the early phase of the disease and in healthy subjects. Despite the presence of melanoma-specific T cells infiltrating tumor lesions, tumor rejection rarely occurs. Among the different mechanisms of such inefficient antitumor response, this review discusses the possible anti-T-cell counterattack mediated by FasL-positive tumor cells, and shows that FasL is located in the cytoplasm of melanoma cells and is transported in the tumor microenvironment through the release of melanosomes. Additionally, mechanisms of suboptimal T cell activation through tumor cell expression of peptide analogs with antagonist activity are described, together with the possibility of overcoming such anergy induction by the usage of optimized tumor epitopes. Down-modulation of HLA expression by target tumor cells and its multiple mechanisms is also considered. Finally, we discuss the role of inducible nitric oxide synthases in determining the inhibition of apoptosis in melanoma cells, which can make such tumor cells resistant to the T-cell attack.

Enhancing antitumor immune responses: intracellular peptide delivery and identification of MHC class II-restricted tumor antigens

The importance of T-cell-mediated antitumor immunity has been demonstrated in both animal models and human cancer therapy. The identification of major histocompatibility complex (MHC) class I-restricted tumor antigens has generated a resurgence of interest in immunotherapy for cancer. However, recent studies suggest that therapeutic strategies that have mainly focused on the use of CD8+ T cells (and MHC class I-restricted tumor antigens) may not be effective in eliminating cancer cells in patients. Novel strategies have been developed for enhancing T-cell responses against cancer by prolonging antigen presentation of dendritic cells to T cells and the inclusion of MHC class II-restricted tumor antigens. identification of MHC class II-restricted tumor antigens, which are capable of stimulating CD4+ T cells, not only aids our understanding of the host immune responses against cancer antigens, but also provides opportunities for developing effective cancer vaccines.

Ultraviolet radiation and tumor immunity

Ultraviolet (UV) radiation induces a specific tolerance toward UV-induced skin tumors. This phenomenon has been known and studied for more than 25 years, but the mechanisms by which protective tumor immunity or tumor tolerance is induced are still largely obscure. In parallel with these studies, short-term assays on UV-induced immunosuppression and tolerance toward simple chemicals (e.g., dinitrochlorobenzene) have been analyzed, particularly with respect to the role of cytokines (most notably, interleukin (IL)-10 vs IL-12). However, these short-term assays are not likely to be fully adequate models of the long-term UV-induced tumor tolerance. The important nodal points of action in these immune reactions appear to be the T cells and the antigen-presenting cells (APCs) that prime them. The main focus should probably be on CD8(+) T cells as the ultimate effector of the cytotoxic response against UV-induced skin cancers. APC-mediated activation of these cells depends strongly on cosignaling of CD4(+) T cells. In a tumor tolerant state the activity of the cytotoxic CD8(+) T cells appears to be inhibited through CTLA-4(+) and natural killer T cells. The latter cells are CD1-restricted, which indicates the importance of "unconventional" antigens to UV-induced tumor tolerance.

Molecular genetic analysis of malignant melanomas for aberrations of the WNT signaling pathway genes CTNNB1, APC, ICAT and BTRC

Aberrant activation of the Wnt signaling pathway has been reported in different human tumor types, including malignant melanomas. We investigated 37 malignant melanomas (15 primary tumors and 22 metastases) for alterations of 4 genes encoding members of this pathway, i.e., CTNNB1 (beta-catenin gene, 3p22.1), APC (adenomatous polyposis coli gene, 5q22.2), BTRC (beta-transducin repeat-containing protein gene, 10q24.3) and ICAT (inhibitor of beta-catenin and Tcf-4, 1p36.2). Mutational analysis of CTNNB1 identified somatic mutations in 1 primary melanoma and 1 melanoma metastasis from 2 different patients (5%). Both mutations affected the N-terminal degradation box of beta-catenin, which is important for the regulation of beta-catenin homeostasis. Another primary melanoma carried a somatic APC missense mutation within the known mutation cluster region in exon 15. Fourteen tumors (40%) showed LOH at microsatellite markers on 1p36. None of the tumors had lost both copies of the ICAT gene, but 1 melanoma metastasis carried a somatic point mutation altering the translation start codon of ICAT. Real-time RT-PCR showed markedly reduced ICAT transcript levels (<or=20% relative to normal skin and benign melanocytic nevi) in 28/36 malignant melanomas (78%), including 13/14 tumors with LOH on 1p36. Allelic loss on 10q was detected in 15 tumors (44%). We found neither mutations nor complete loss of expression of the BTRC gene in our melanoma series. Taken together, our results indicate that the Wnt pathway may be altered in malignant melanomas by different mechanisms, including rare somatic mutations in CTNNB1, APC or ICAT, as well as low or absent expression of ICAT transcripts.

Tumor-associated antigens as possible targets for immune therapy in head and neck cancer: comparative mRNA expression analysis of RAGE and GAGE genes

Specific immune therapy targeting residual areas of cancer cells may emerge as a powerful treatment strategy for head and neck squamous cell carcinoma (HNSCC). In order to define possible targets for immune therapy, we evaluated the frequency of two groups of tumor antigens-the RAGE and GAGE families-by means of reverse transcriptase polymerase chain reaction using primary HNSCCs (n = 28), mucosa specimens as normal controls (n = 10) and HNSCC cell lines (n = 6). By means of specific primer selection we could differentiate between RAGE-1, -2, -3 and -4, as well as between two groups of GAGE genes (GAGE-1,2,7 vs GAGE-3,4,5,6,8). While all mucosa tissues (from smokers and non-smokers) were negative for both antigen families, 24/28 investigated tumors were positive for up to 5 tumor antigens. Among the RAGE genes, RAGE-1-positive tumors were the most abundant (8/28), followed by RAGE-2 (7/28) and RAGE-4 (6/28). Differences in the locations of HNSCCs were reflected by different RAGE family members being expressed most frequently: larynx, RAGE-1; oropharynx, RAGE-2; and hypopharynx, RAGE-4. Primers against GAGE-1,2,7 and GAGE-3,4,5,6,8 revealed 6/27 and 16/27 positive tumors, respectively. This report suggests that RAGE genes and GAGE-3,4,5,6,8 may be promising candidates for specific immune therapy in HNSCC.

Evidence for involvement of Wnt signaling pathway in IB-MECA mediated suppression of melanoma cells

The A3 adenosine receptor, A3AR, belongs to the family of Gi proteins, which upon induction, suppresses the formation of cAMP and its downstream effectors. Recent studies have indicated that activation of A3AR by its agonist, IB-MECA, results in growth inhibition of malignant cells. Here we demonstrate the ability of IB-MECA to decrease the levels of protein kinase A, a downstream effector of cAMP, and protein kinase B/Akt in melanoma cells. Examination of glycogen synthase kinase 3beta, GSK-3beta, whose phosphorylation is controlled by protein kinase A and B, showed a substantial decrease in the levels of its phosphorylated form and an increase in total GSK-3beta levels in IB-MECA treated melanoma cells. This observation suggests that the treatment of cells with IB-MECA augments the activity of GSK-3beta in the cells. Evaluation of beta-catenin, a key component of Wnt signaling pathway which, upon phosphorylation by GSK-3beta rapidly ubiquitinates, showed a substantial decrease in its level after IB-MECA treatment. Accordingly, the level of beta-catenin responsive cell growth regulatory genes including c-myc and cyclin D1 was severely declined upon treatment of the cells with IB-MECA. These observations which link cAMP to the Wnt signaling pathway provide mechanistic evidence for the involvement of Wnt pathway via its key elements GSK-3beta and beta-catenin in the anti-tumor activity of A3AR agonists.

Cancer immunotherapy with peptide-based vaccines: what have we achieved? Where are we going?

Many human tumor-associated antigens (TAAs) have recently been identified and molecularly characterized. When bound to major histocompatibility complex molecules, TAA peptides are recognized by T cells. Clinical studies have therefore been initiated to assess the therapeutic potential of active immunization or vaccination with TAA peptides in patients with metastatic cancer. So far, only a limited number of TAA peptides, mostly those recognized by CD8(+) T cells in melanoma patients, have been clinically tested. In some clinical trials, partial or complete tumor regression was observed in approximately 10%-30% of patients. No serious side effects have been reported. The clinical responses, however, were often not associated with a detectable T-cell-specific antitumor immune response when patients' T cells were evaluated in ex vivo assays. In this review, we analyze the available human TAA peptides, the potential immunogenicity (i.e., the ability to trigger a tumor-specific T-cell response) of TAA peptides in vitro and ex vivo, and the potential to construct slightly modified forms of TAA peptides that have increased T-cell stimulatory activity. We discuss the available data from clinical trials of TAA peptide-based vaccination (including those that used dendritic cells to present TAA peptides), identify possible reasons for the limited clinical efficacy of these vaccines, and suggest ways to improve the clinical outcome of TAA peptide-based vaccination for cancer patients.

Identification of a mutated fibronectin as a tumor antigen recognized by CD4+ T cells: its role in extracellular matrix formation and tumor metastasis

CD4+ T cells play an important role in orchestrating host immune responses against cancer, particularly by providing critical help for priming and extending the survival of CD8+ T cells. However, relatively little is known about major histocompatibility complex class II-restricted human tumor antigens capable of activating CD4+ T cells. Here, we describe the identification of a mutated fibronectin (FN) as a tumor antigen recognized by human histocompatibility leukocyte antigen-DR2-restricted CD4+ T cells. Deoxyribonucleic acid (DNA) sequencing analysis indicated that this gene contains a mutation that results in the substitution of lysine for glutamic acid and gives rise to a new T cell epitope recognized by CD4+ T cells. Tumor cells harboring the mutant FN resulted in the loss of FN matrix formation and the gain of metastatic potential based on the migration pattern compared with that of tumor cells that express wild-type FN. Additional experiments using cell lines stably expressing the mutated FN cDNA demonstrated that the point mutation in FN was responsible for the loss of FN staining in extracellular matrices and the enhancement of tumor cell migration. These findings represent the first demonstration that a mutated gene product recognized by CD4+ T cells is directly involved in tumor metastasis, which indicates the importance of CD4+ T cells in controlling the spread of tumor cells to distant anatomic sites.

Potential mouse tumor model for pre-clinical testing of mage-specific breast cancer vaccines

Currently, there is a lack of suitable pre-clinical mouse models for testing and optimization of experimental cancer vaccines. Here, in situ developed mammary tumors of MMTV-v-Ha-ras and MMTV-c-myc transgenic mice and normal mammary, liver, spleen, and testis were screened for expression of tumor-associated antigens (TAA) Mage-b1/2/3 by reverse-transcriptase polymerase chain reaction (RT-PCR) and Southern blot hybridization. Mage-b1/2/3 are homologues of the human TAA MAGE-B1/2/3. Expression of these human MAGE genes has been found in tumors of various histological types, including breast cancer. Mage-specific RT-PCR products (using primers that amplify all three Mage-b1/2/3) were detected in mammary tumors of the MMTV-v-Ha-ras and MMTV-c-myc transgenic mice and in testis, but not in other normal tissues. RT-PCR products obtained from the mammary tumors (using primers that amplify the complete protein-encoding region of Mage-b1/2/3) were cloned and sequenced, and appeared to be most homologous with Mage-b3. Comparison of the Mage-b3 gene in mammary tumors and normal tissues suggest that somatic mutations did not occur in the Mage-b3 gene of the ras- and myc-induced mammary tumors. In addition, no differences were found between the Mage-b3 cDNA of testis, the only normal tissue that expresses Mage-b3, and Mage-b3 in genomic DNA of normal kidney, where Mage-b3 is silent. The MMTV-v-Ha-ras and MMTV-c-myc transgenic mice of this study are the first immune competent mouse models with in situ developed mammary tumors in which the expression of Mage-b3 TAA has been demonstrated. This makes them potentially suitable as a mouse model for pre-clinical testing of Mage-specific cancer vaccines in vivo.

Cleavage and polyadenylation specificity factor (CPSF)-derived peptides can induce HLA-A2-restricted and tumor-specific CTLs in the majority of gastrointestinal cancer patients

To identify CTL-directed antigens in gastrointestinal cancer, we have investigated antigens recognized by the HLA-A2-restricted CTL line established from T cells infiltrating into colon cancer and report herein cleavage and polyadenylation specificity factor (CPSF) as a potent antigen holding peptides capable of inducing CTLs. Five peptides at amino acid positions 250-258, 392-400, 534-542, 1296-1304 and 1359-1368 of CPSF, which were recognized by the CTL line, were found to have the ability to induce HLA-A2-restricted and tumor-specific CTLs in peripheral blood mononuclear cells of the majority (69%, 11/16) of gastrointestinal cancer patients with different HLA-A2 subtypes. Thus, these peptides might be appropriate molecules for use in the peptide-based specific immunotherapy of HLA-A2(+) patients with gastrointestinal cancers.