We have carried out a descriptive analysis of losses and gains of chromosomal segments in gastrointestinal tumorigenesis by unbiased DNA fingerprinting. This method generates a profile of differences between tumor and normal genomes which we call """"""""amplotype"""""""". This amplotype represents a molecular karyotype because the chromosomal location of the fingerprinting bands is previously known. We have detected the losses and gains of novel chromosomal regions in the vast majority of colorectal metastic carcinomas. These alterations unmask the presence of genes with positive and negative roles in cell growth or survival (cancer genes) that are under positive or negative selection during tumorigenesis. This renewal grant application focuses on the role played in tumorigenesis by moderate gains of genetic material. Our goals are first, to continue this descriptive amplotype analysis, and second, to search for some of the novel cancer genes that we have discovered in these chromosomal regions. We will generate a """"""""high density"""""""" amplotype of colorectal cancer to complete the search for novel cancer genes and to determine if the gains of some chromosomal regions involve the selection for increased levels of wild type or mutant positive cancer genes, with or without the loss of negative cancer genes from the same chromosomal regions. These experiments should yield additional novel information regarding the peculiarities of the genetic alterations underlying gastrointestinal tumorigenesis which can be uniquely addressed with the amplotype approach. They will also test the hypothesis that the presence in the same chromosomal region of positive and negative cancer genes provides a safety mechanism for neoplasia, by obstructing the unfolding of their oncogenic potential. We also propose to determine whether c-myc is the only relevant positive cancer gene in a region of common gain at chromosome 8q24; to map the precise location and start the isolation by positional cloning of the negative cancer gene(s) which we have assigned to chromosome 4q13-24; and to search for the cancer gene(s) in a region of common gains at chromosome 13 by structural (mapping) and functional(DNA transfection and tumorigenicity assays) approaches. These experiments should provide a better estimation of the involvement of known cancer genes (i.e. c- myc) in colorectal tumorigenesis, and may lead to the isolation of novel positive and negative cancer genes at chromosomes 13 and 4, which appear to be required for colorectal cancer development and/or metastatic dissemination, respectively.
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