Spectral Karyotyping in Cancer Cytogenetics

Cancer is a genetic disease. Gene mutations are not only responsible for rare hereditary forms of human cancer, but for the sporadic forms of human malignancies as well. Many of these specific genetic defects in cancer cells can be visualized as chromosomal aberrations. Conventional cytogenetic analysis of metaphase chromosomes from human malignancies is a first screening step to identify chromosomal aberrations. Since the introduction of chromosome banding techniques in 1970 by Caspersson et al. (1 ), significant knowledge of chromosomal aberrations especially in hematologic malignancies as well as sarcomas has been gained. In these malignancies, specific balanced translocations were identified and have led to the cloning of the genes involved at many breakpoints. These aberrations have proven to be of significant etiologic, diagnostic, prognostic, as well as therapeutic relevance, especially in leukemias. While cytogenetic analyses have been exceedingly valuable for the description of chromosomal abnormalities in hematologic malignancies and in sarcomas, epithelial cancers were more difficult to study. This is owing, in part, not only to the accessibility of malignant cells and subsequently metaphases for cytogenetic analysis in leukemias, but also to the nature of reciprocal translocations, which provided more immediate entry points for positional cloning efforts.