PubMed Health⌕ Search

Biomedical subjects

B Van den Eynde

Publications and source records attributed to B Van den Eynde.

At least 19 recordsLinked to original sources
PubMed2003

[A new mechanism of tumor resistance to the immune system, based on tryptophan breakdown by indoleamine 2,3-dioxygenase].

T lymphocytes represent the main effectors of the immune response that can lead to tumor rejection, which represents the aim of various approaches of immunotherapy that are currently tested. However, in many cases, tumor cells appear to resist immune rejection. We have recently uncovered a new mechanism of tumoral immune resistance based on the expression by tumor cells of indoleamine 2,3-dioxygenase (IDO), an enzyme that rapidly degrades tryptophan, an amino acid that is crucial to sustain proliferation of T lymphocytes. We showed that most human tumors constitutively express IDO. We also observed that expression of IDO by immunogenic mouse tumor cells, prevents their rejection by pre-immunized mice. This effect is accompanied by a lack of accumulation of specific T cells at the tumor site, and can be partly reverted by systemic treatment of mice with an inhibitor of IDO, in the absence of noticeable toxicity. These results suggest that the efficacy of therapeutic vaccination of cancer patients might be improved by concomitant administration of an IDO inhibitor.

Humans↗
PubMed1999

Characterization of the GAGE genes that are expressed in various human cancers and in normal testis.

The GAGE-1 gene was identified previously as a gene that codes for an antigenic peptide, YRPRPRRY, which was presented on a human melanoma by HLA-Cw6 molecules and recognized by a clone of CTLs derived from the patient bearing the tumor. By screening a cDNA library from this melanoma, we identified five additional, closely related genes named GAGE-2-6. We report here that further screening of this library led to the identification of two more genes, GAGE-7B and -8. GAGE-1, -2, and -8 code for peptide YRPRPRRY. Using another antitumor CTL clone isolated from the same melanoma patient, we identified antigenic peptide, YYWPRPRRY, which is encoded by GAGE-3, -4, -5, -6, and -7B and which is presented by HLA-A29 molecules. Genomic cloning of GAGE-7B showed that it is composed of five exons. Sequence alignment showed that an additional exon, which is present only in the mRNA of GAGE-1, has been disrupted in gene GAGE-7B by the insertion of a long interspersed repeated element retroposon. These GAGE genes are located in the p11.2-p11.4 region of chromosome X. They are not expressed in normal tissues, except in testis, but a large proportion of tumors of various histological origins express at least one of these genes. Treatment of normal and tumor cultured cells with a demethylating agent, azadeoxycytidine, resulted in the transcriptional activation of GAGE genes, suggesting that their expression in tumors results from a demethylation process.

Amino Acid Sequence↗
PubMed1999

A structure-based approach to designing non-natural peptides that can activate anti-melanoma cytotoxic T cells.

Tumor antigens presented by major histocompatibility complex (MHC) class I molecules and recognized by CD8(+) cytotoxic T lymphocytes (CTLs) may generate an efficient antitumor immune response after appropriate immunization. Antigenic peptides can be used in vivo to induce antitumor or antiviral immunity. The efficiency of naked peptides may be greatly limited by their degradation in the biological fluids. We present a rational, structure-based approach to design structurally modified, peptidase-resistant and biologically active analogues of human tumor antigen MAGE-1.A1. This approach is based on our understanding of the peptide interaction with the MHC and the T cell receptor and its precise degradation pathway. Knowledge of these mechanisms led to the design of a non-natural, minimally modified analogue of MAGE-1.A1, [Aib2, NMe-Ser8]MAGE-1.A1, which was highly peptidase-resistant and bound to MHC and activated MAGE-1.A1-specific anti-melanoma CTLs. Thus, we showed that it is possible to structurally modify peptide epitopes to obtain analogues that are still specifically recognized by CTLs. Such analogues may represent interesting leads for antitumor synthetic vaccines.

Amino Acid Substitution↗
PubMed1996

A mutated HLA-A2 molecule recognized by autologous cytotoxic T lymphocytes on a human renal cell carcinoma.

Many human tumor cells have been shown to express antigens that are recognized by autologous cytotoxic T lymphocytes (CTL) and the molecular nature of a number of melanoma antigens has been defined recently. Here we describe the characterization of an antigen recognized on a renal cell carcinoma by autologous CTL clones. This antigen is encoded by the HLA-A2 gene present in the tumor cells. The sequence of this gene differs from the HLA-A2 sequence found in autologous peripheral blood lymphocytes by a point mutation that results in an arginine to isoleucine exchange at residue 170, which is located on the alpha-helix of the alpha 2 domain. Transfection experiments with the normal and mutated HLA-A2 cDNA demonstrated that this amino acid replacement was responsible for the recognition of the HLA-A2 molecule expressed on the tumor cells. The mutant HLA-A2 gene was also detected in the original tumor tissue from the patient, excluding the possibility that the mutation had appeared in vitro. Thus, HLA class I molecules carrying a tumor-specific mutation can be involved in the recognition of tumor cells by autologous CTL.

Aged↗
PubMed1995

A new family of genes coding for an antigen recognized by autologous cytolytic T lymphocytes on a human melanoma.

Human melanoma MZ2-MEL expresses several distinct antigens that are recognized by autologous cytolytic T lymphocytes (CTL). Some of these antigens are encoded by genes MAGE-1, MAGE-3, and BAGE, which are expressed in a large fraction of tumors of various histological types but are silent in normal adult tissues with the exception of testis. We report here the identification of the gene coding for MZ2-F, another antigen recognized by autologous CTL on MZ2-MEL cells. This gene, which was named GAGE-1, is not related to any presently known gene. It belongs to a family of genes that are expressed in a variety of tumors but not in normal tissues, except for the testis. Antigenic peptide YRPRPRRY, which is encoded by GAGE-1, is recognized by anti-MZ2-F CTL on class I molecule HLA-Cw6. The two genes of the GAGE family that code for this peptide, namely GAGE-1 and GAGE-2, are expressed in a significant proportion of melanomas (24%), sarcomas (25%), non-small cell lung cancers (19%), head and neck tumors (19%), and bladder tumors (12%). About 50% of melanoma patients carry on their tumor at least one of the presently defined antigens encoded by the MAGE, BAGE, and GAGE genes.

Amino Acid Sequence↗
PubMed1995

New tumor antigens recognized by T cells.

A series of tumor cell antigens that are recognized by cytolytic T lymphocytes has been characterized this year. Besides the antigens derived from proteins specifically expressed in tumors, many melanoma antigens derive from melanocytic differentiation proteins. In addition, antigens unique to individual tumors result from mutations in ubiquitously expressed genes.

Amino Acid Sequence↗
PubMed1994

Human gene MAGE-3 codes for an antigen recognized on a melanoma by autologous cytolytic T lymphocytes.

Human melanoma cell line MZ2-MEL expresses several antigens recognized by autologous cytolytic T lymphocyte (CTL) clones. We reported previously the identification of a gene, named MAGE-1, that codes for one of these antigens named MZ2-E. We show here that antigen MZ2-D, which is present on the same tumor, is encoded by another member of the MAGE gene family named MAGE-3. Like MAGE-1, MAGE-3 is composed of three exons and the large open reading frame is entirely located in the third exon. Its sequence shows 73% identity with MAGE-1. Like MZ2-E, antigen MZ2-D is presented by HLA-A1. The antigenic peptide of MZ2-D is a nonapeptide that is encoded by the sequence of MAGE-3 that is homologous to the MAGE-1 sequence coding for the MZ2-E peptide. Competition experiments using single Ala-substituted peptides indicated that amino acid residues Asp in position 3 and Tyr in position 9 were essential for binding of the MAGE-1 peptide to HLA-A1. Gene MAGE-3 is expressed in many tumors of several types, such as melanoma, head and neck squamous cell carcinoma, lung carcinoma and breast carcinoma, but not in normal tissues except for testes. It is expressed in a larger proportion of melanoma samples than MAGE-1. MAGE-3 encoded antigens may therefore have a wide applicability for specific immunotherapy of melanoma patients.

Adult↗
PubMed1994

Localization of two cytotoxic T lymphocyte epitopes and three anchoring residues on a single nonameric peptide that binds to H-2Ld and is recognized by cytotoxic T lymphocytes against mouse tumor P815.

Mouse mastocytoma P815 expresses tumor antigens P815A and P815B encoded by a single gene called P1A and carried by a single peptide named P1A 35-43 (NH2-Leu-Pro-Tyr-Leu-Gly-Trp-Leu-Val-Phe-COOH). P1A 35-43 is presented to anti-P815A and anti-P815B cytotoxic T lymphocytes (CTL) by major histocompatibility complex (MHC) H-2Ld molecules. In order to determine the individual role played by each amino acid residue of P1A 35-43 in binding to H-2Ld and in recognition by anti-A and anti-B T cell receptors (TcR), a series of P1A35-43 peptides substituted by alanine at single positions was synthesized and tested for binding to H-2Ld and for CTL recognition. Binding to H-2Ld was estimated by measuring the ability of the peptide to up-regulate cell surface expression of H-2Ld. We found that three residues were important for interaction of P1A 35-43 with H-2Ld. Two of them, Pro at position 2 and Phe at position 9 were consistent with the described H-2Ld binding motif. A third residue, Trp at position 6, was also required for effective MHC binding of the tumor antigen. CTL sensitization assays showed that alanine substitution at position 7 (Leu) or at position 8 (Val) dramatically affected peptide recognition by anti-A CTL while positions 3 (Tyr) and 4 (Leu) were critical for recognition by anti-B CTL. We conclude that Pro2, Trp6 and Phe9 constitute the anchor residues of P1A 35-43 to H-2Ld, whereas the dipeptidyl sequences Tyr3-Leu4 and Leu7-Val8 form the core epitopes recognized by the TcR of anti-P815B and anti-P815A CTL, respectively.

Amino Acid Sequence↗
PubMed1994

Identification and characterization of the tumor-specific P1A gene product.

In murine mastocytoma P815, gene P1A directs the expression of antigens P815A and B which are the target of a T cell-mediated rejection response in syngeneic animals. This gene is expressed at a high level in various tumors, but is silent in normal tissues except testis and placenta; its activation is thus possibly related to malignant transformation. An anti-synthetic peptide rabbit antiserum reacted by immunoblotting with a cellular protein migrating near 40 kDa on SDS-PAGE. The immunoreactive protein was detected only in lysates from cells which express antigen P815A: P1.HTR mastocytoma cells and, after transfection with cosmids carrying the P1A gene, the antigen-loss variant P0.HTR cells and DAP-3 H-2Ld fibroblasts. The identity of this protein as the P1A gene product was confirmed by cell-free transcription-translation of the P1A cDNA, the product of which also migrated near 40 kDa in SDS-PAGE and was captured by protein A-Sepharose in the presence of the antiserum. Subcellular fractionation by differential and isopycnic centrifugation indicated that the P1A protein is associated with cytoplasmic membranes demonstrating a broad distribution with respect to size and density. Immunofluorescence microscopy also revealed a cytoplasmic signal, particularly intense in small vesicles, which coincides with that produced by an anti-mouse type I collagen guinea pig antiserum except near the cell periphery where the P1A signal is weaker. We conclude that the P1A protein is bound to membranes of the secretory pathway, at a concentration which goes increasing from the endoplasmic reticulum to secretion vesicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Tumor antigens recognized by T lymphocytes.

Transplantation experiments have demonstrated that most mouse tumors express antigens that can constitute targets for rejection responses mediated by syngeneic T lymphocytes. For human tumors, autologous cultures mixing tumor cells and blood lymphocytes or tumor-infiltrating lymphocytes have produced CD8+ and CD4+ cytolytic T cell (CTL) clones that recognize tumor cells specifically. Attempts to identify the target antigens by biochemical fractionation of tumor cells up to now have failed, with the important exception of the identification of underglycosylated mucins present on breast and pancreatic carcinomas. Gene transfection approaches have proved more successful. A gene family named MAGE codes for antigens recognized by autologous CTL on a melanoma tumor. These genes are not expressed in normal tissues except for testis. They are expressed in many tumors of several histological types. Differentiation antigens coded by genes such as tyrosinase are also recognized on human melanoma by autologous CTL. The identification of human tumor rejection antigens opens new possibilities for systematic approaches to the specific immune therapy of cancer.

Animals↗
PubMed1992

Transfection and expression of a gene coding for a human melanoma antigen recognized by autologous cytolytic T lymphocytes.

Human melanoma line MZ2-MEL expresses several antigens recognized by autologous cytolytic T lymphocytes (CTL). As a first step towards the cloning of the gene coding for one of these antigens, we tried to obtain transfectants expressing the antigen. The DNA recipient cell was a variant of MZ2-MEL which had been selected with a CTL clone for the loss of antigen E. It was cotransfected with genomic DNA of the original melanoma line and with selective plasmid pSVtkneo beta. Geneticin-resistant transfectants were obtained at a frequency of 2 x 10(-4). These transfectants were then screened for their ability to stimulate the production of tumor necrosis factor by the anti-E CTL clone. One transfectant expressing antigen E was identified among 70,000 drug-resistant transfectants. Its sensitivity to lysis by the anti-E CTL was equal to that of the original melanoma cell line. When this transfectant was submitted to immunoselection with the anti-E CTL clone, the resulting antigen-loss variants were found to have lost several of the transfected pSVtkneo beta sequences. This indicated that the gene coding for the antigen had been integrated in the vicinity of pSVtkneo beta sequences, as expected for cotransfected DNA.

Antigens, Neoplasm↗
PubMed1992

Molecular definition of tumor antigens recognized by T lymphocytes.

Several tumor antigens recognized by T cells have now been identified at the molecular level. Various mechanisms can account for their expression: activation of normally silent genes; point mutations; chromosome translocations; and post-translational modifications of proteins. This led to the notion that potential tumor-rejection antigens can be shared by a significant proportion of human tumors. This may have important implications in cancer immunotherapy, especially since tumors expressing a defined antigen can be identified on the basis of the expression of the relevant gene.

Animals↗
PubMed1992

Identification of tumour rejection antigens recognized by T lymphocytes.

On the basis of the results reviewed here, there are two major mechanisms whereby tumour rejection antigens may arise. The first mechanism is mutational. Point mutations occurring in a large variety of genes may produce new antigenic peptides, either by providing them with the ability to bind to MHC class I molecules or by providing them with a new epitope (Fig. 2). The second mechanism is the activation of a gene that is silent in normal tissues and for which no strong natural tolerance has been established. Plausible candidates for the mutational mechanism are the "tumour specific transplantation antigens" observed on methylcholanthrene induced tumours and tumours induced by ultraviolet light. The diversity of these antigens appears to be very large, like that of the tum- antigens. Moreover, these tumours have been obtained with high doses of carcinogens, which are proven mutagens. On the other hand, a P815 tumour rejection antigen appears to arise through the activation of a silent gene, and it may turn out that this is the rule for most tumour rejection antigens. It is our hope that other genes coding for mouse and human tumour rejection antigens will soon be identified, so that it will become clear whether the activational mechanism is the rule or the exception. In our view, this is a crucial issue. Insofar as tumour rejection antigens result from mutations, they may be highly specific for every individual tumour. The tumour specific nature of these antigens would then be easily ascertained. However, active immunization of cancer patients would require that a tumour cell line be obtained from each patient, a most unpractical prospect. If, on the other hand, production of tumour rejection antigens results from the activation of a normal gene, then there is a good probability that the same gene may be activated in many different tumours, being perhaps preferentially shared by tumours of the same histological type. This would probably not result in the expression of the same antigen in all these tumours, because the patients would differ in their presenting molecules, which are determined by their HLA haplotype. However, a subset of the tumours expressing the same "tumour rejection" gene should share the same class I restricting element, so that all of these patients could be immunized with a cell that would express the gene and carry the appropriate HLA molecule.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

A gene encoding an antigen recognized by cytolytic T lymphocytes on a human melanoma.

Many human melanoma tumors express antigens that are recognized in vitro by cytolytic T lymphocytes (CTLs) derived from the tumor-bearing patient. A gene was identified that directed the expression of antigen MZ2-E on a human melanoma cell line. This gene shows no similarity to known sequences and belongs to a family of at least three genes. It is expressed by the original melanoma cells, other melanoma cell lines, and by some tumor cells of other histological types. No expression was observed in a panel of normal tissues. Antigen MZ2-E appears to be presented by HLA-A1; anti-MZ2-E CTLs of the original patient recognized two melanoma cell lines of other HLA-A1 patients that expressed the gene. Thus, precisely targeted immunotherapy directed against antigen MZ2-E could be provided to individuals identified by HLA typing and analysis of the RNA of a small tumor sample.

Antigens, Neoplasm↗