Melanoma-Associated Antigen Gene - Assignment Example

 Melanoma-Associated Antigen Gene The first human (mammalian) members of the MAGE (Melanoma-associated antigen) gene family that have been described are expressed in tumor cells but silent in normal adult tissues except in the male germ line. They encode strictly tumor-specific antigens that represent attractive targets for cancer immunotherapy. However, other members of the family were recently found to be expressed in normal cells, indicating that the family is larger and more disparate than initially expected. MAGE-like genes have also been identified in non-mammalian species, like the zebrafish or Drosophila melanogaster. Although no MAGE homologous sequences have been identified in Caenorhabditis elegans, Saccharomyces cerevisiae or Schizosaccharomyces pombe, MAGE sequences have been found in several vegetal species, including Arabidopsis thaliana. A database screening was performed to identify all of the recorded members of both classes of human MAGE genes. This report provided an overview of the MAGE family and proposed a general nomenclature for all of the MAGE genes identified thus far. The MAGE-D genes were particularly well conserved between man and mouse, suggesting that they exert important functions. In addition, the genomic structure of the MAGE-D genes indicates that one of them corresponds to the founder member of the family, and that all of the other MAGE genes are retrogenes derived from that common ancestral gene. MAGE-A1 belongs to a group of germline-specific genes that rely primarily on DNA methylation for repression in somatic tissues. In many types of tumors, the promoter of these genes becomes demethylated and transcription becomes activated. MAGE-A1 acts as a transcriptional repressor. MAGE -A1, the first characterized cancer-germline gene, belongs to a family of twelve genes located on the X chromosome in region q28 (5,6). GENE FAMILY Genes of the MAGE family have their entire coding sequences located in the last exon, which shows 64 to 85% identity with that of MAGE 1 (De Plaen et al., 1994). (An exception is MAGE D2, 300470). The coding sequences predict the main structural features of all MAGE proteins, in contrast, the promoters and first exons of the MAGE genes show considerable variability, possibly enabling the same function to be expressed under different transcriptional controls. In their annotation of the DNA sequence of the human X chromosome and the predicted proteome, Ross et al. (2005) noted that the MAGE domain was present in 32 genes. In comparison, only 4 other MAGE genes had been reported in the rest of the genome: MAGE F1 (609267) on chromosome 3, and MAGE L2 (605283), NDN (602117), and NDNL2 (608243) in the proximal portion of the long arm of chromosome 15. The MAGE gene products are members of the cancer-testis (CT) antigen group, which are characterized by their expression in a number of cancer types, while their expression in normal tissues is solely or predominantly in testis. This expression profile had led to the suggestion that the CT antigens are potential targets for tumor immunotherapy. Ross et al. (2005) stated that the X chromosome gene set they described contained 99 CT antigen genes, including novel members of the MAGE, GAGE, SSX, LAGE, CSAGE, and NXF families. Ross et al. (2005) predicted that approximately 10% of the genes on the X chromosome are of the CT antigen type. The remarkable enrichment for CT antigen genes on this chromosome relative to the rest of the genome may be indicative of a male advantage associated with these genes. Recessive alleles that are beneficial to males are expected to become fixed more rapidly on the X chromosome than on an autosome. If these alleles are detrimental to females, their expression could become restricted to male tissues as they rise to fixation. The CT antigen genes on the X chromosome are also notable for the expansion of various gene families by duplication. This degree of duplication is perhaps an indication of selection in males for increased copy number. In this context, it was noted that the MAGE family has independently expanded on the X chromosome in both human and mouse lineages. Many antigens recognized by autologous T lymphocytes have been identified on human melanoma. Melanoma patients usually mount a spontaneous T cell response against their tumor. But at some point, the responder T cells become ineffective, probably because of a local immuno-suppressive process occurring at the tumor sites. Therapeutic vaccination of metastatic melanoma patients with these antigens is followed by tumor regressions only in a small minority of the patients. The T cell responses to the vaccines show correlation with the tumor regressions. The local immuno-suppression may be the cause of the lack of vaccination effectiveness that is observed in most patients. In patients who do respond to the vaccine, the anti-vaccine T cells probably succeed in reversing focally this immuno-suppression and trigger a broad activation of other anti tumor T cells, which proceed to destroy the tumor. Scientists have identified a new antigenic peptide presented by HLA-Cw7 and encoded by several MAGE genes using dendritic cells transduced with lentiviruses. Antigens encoded by MAGE genes are of particular interest for cancer immunotherapy because they are tumor specific and shared by tumors of different histological types. Several clinical trials are in progress with MAGE peptides, proteins, recombinant poxviruses, and dendritic cells (DC) pulsed with peptides or proteins. MAGE Genes are Potential Cancer Immunotherapy targets. Hepatocellular carcinoma tumor-specific immunotherapy makes use of MAGE gene products.  Research has demonstrated that the activation of human MAGE genes leads to the expression of a set of tumor rejection antigens. These antigens are recognized by cytotoxic T lymphocytes (CTL’s). Several of these genes are also discussed in Van der Bruggen et al., Science 254: 1643 (1991). It is now clear that the various genes of the MAGE family are expressed in tumor cells, and can serve as markers for the diagnosis of such tumors, as well as for other purposes discussed therein. It has also been found that, when comparing homologous regions of various MAGE genes to the region of the MAGE-1 gene coding for the relevant nonapeptide, there is a great deal of homology. Indeed, these observations lead to one of the aspects of the invention, which is a family of nonapeptides all of which have the same N-terminal and C-terminal amino acids. These nonapeptides can be used for various purposes, which includes their use as immunogens, either alone or coupled to carrier peptides. Nonapeptides are of sufficient size to constitute an antigenic epitope, and the antibodies generated there to may then be used to identify the nonapeptide, either as it exists alone, or as part of a larger polypeptide. Therapeutic Vaccination Trials- To evaluate the toxicity, anti tumoral effectiveness, and immunogenicity of repeated vaccinations with ALVAC miniMAGE-1/3, a recombinant canary pox virus containing a minigene encoding antigenic peptides MAGE-3 (168-176) and MAGE-1 (161-169), which are presented by HLA-A1 and B35 on tumor cells and can be recognized by cytolytic T lymphocytes (CTLs). The vaccination schedule comprised four sequential injections of the recombinant virus, followed by three booster vaccinations with the MAGE-3 (168-176) and MAGE-1 (161-169) peptides. The vaccines were administered, both intradermally and subcutaneously, at 3-week intervals. Forty patients with advanced cancer were treated, including 37 melanoma patients. The vaccines were generally well tolerated with moderate adverse events, consisting mainly of transient inflammatory reactions at the virus injection sites. Among the 30-melanoma patients assessable for tumor response, a partial response was observed in one patient, and disease stabilization in two others. The remaining patients had progressive disease. Among the patients with stable or progressive disease, five showed evidence of tumor regression. A CTL response against the MAGE-3 vaccine antigen was detected in three of four patients with tumor regression, and in only one of 11 patients without regression. Repeated vaccination with ALVAC miniMAGE-1/3 is associated with tumor regression and with a detectable CTL response in a minority of melanoma patients. There is a significant correlation between tumor regression and CTL response. The contribution of vaccine-induced CTL in the tumor regression process is discussed in view of the immunologic events that could be analyzed in detail in one patient. To evaluate toxicity, tumor evolution and immunologic response following administration of a fixed dose of a recombinant MAGE-3 protein by subcutaneous and intradermal routes in the absence of immunologic adjuvant. Thirty-two patients with detectable metastatic melanoma expressing gene MAGE-3 were included and 30 received at least one injection with a fixed dose of a Prot D-MAGE-3 fusion protein. The immunization schedule included 6 intradermal and subcutaneous injections at 3-week intervals. Afterward, patients without major tumor progression who required other treatments received additional vaccinations at increasing time intervals. The vaccine was generally well tolerated. Among the 26 patients who received at least 4 vaccinations, we observed 1 partial response and 4 mixed responses. For these 5 responding patients, time to progression varied from 3.5 to 51+ months. An anti-MAGE-3 CD4 T-lymphocyte response was detected in 1 out of the 5 responding patients. The majority of patients had no anti-MAGE-3 antibody response. The clinical and immunologic responses generated by the vaccine are rather limited. Nevertheless, given the potential antitumor efficacy and the very mild toxicity of vaccinations, further studies combining MAGE proteins and/or peptides with potent immunologic adjuvant are warranted, not only in metastatic melanoma, but also in the adjuvant setting. References: De Plaen, E.; Arden, K.; Traversari, C.; Gaforio, J. J.; Szikora, J. -P.; De Smet, C.; Brasseur, F.; Van der Bruggen, P.; Lethe, B.; Lurquin, C.; Brasseur, R.; Chomez, P.; De Backer, O.; Cavenee, W.; Boon, T.: Structure, chromosomal localization, and expression of 12 genes of the MAGE family. Immunogenetics 40: 360-369, 1994. Ross, M. T.; Grafham, D. V.; Coffey, A. J.; Scherer, S.; McLay, K Muzny, D.; Platzer, M.; Howell, G. R.; Burrows, C.; Bird, C. P.; Frankish, A.; Lovell, F. L.; and 270 others: The DNA sequence of the human X chromosome. Nature 434: 325-337, 2005. Van der Bruggen, P.; Traversari, C.; Chomez, P.; Lurquin, C.; De Plaen, E.; Van den Eynde, B.; Knuth, A.; Boon, T.: A gene encoding an antigen recognized by cytolytic T lymphocytes on a human melanoma. Science 25 4: 1643-1647, 1991. Ludwig Institute for Cancer Research, Brussels Branch, and B-1200 Brussels, Belgium; email: thierry.boon@bru.licr.org,benoit.vandeneynde@bru.licr.org, pierre.vanderbruggen@bru.licr.org, and patrick.chomez@bru.licr.org 2 Cellular Genetics Unit, Universite de Louvain, B-1200 Brussels, Belgium; email: coulie@gece.ucl.ac.be. Read More