Chromosome abnormalities in human cancer

The karyotypic changes in malignant turner cells are unevenly distributed t hroughout the human genome. Modern cancer cytogenetics showed that differen t chromosomal bands are preferentially involved in rearrangements in differ ent neoplasms and specific aberrations were identified. Due to the availabi lity of bone marrow cells first insights were done into pathogenesis of hem atologic malignancies and were accompanied by elucidation of the role of ch romosomal translocations and deletions. Deletions result very often in loss of a tumor suppressor genes whereas specific translocations and inversions lead to the two principal consequences: 1. new fusion gene encoding chimer ic protein is created-mostly in myeloid disorders, 2. gene for the immunogl obulin or T-cell receptor is moved near to the proto-oncogene and enhaces i ts activity - mostly for lymphoid disorders. All three above mentioned rear rangements were later on proved in solid tumors as well. The breakpoints of many translocations specific for different hematologic and solid tumors ha ve been cloned and serve as molecular markers for diagnosis. Cytogenetic an alyses are part of the routine workout of the patients. A variety of molecu lar techniques are now available for wide genome screening of alterations i n copy number, structure and expression of genes and DNA sequences. Molecul ar cytogenetics has special methods: fluorescence in situ hybridization (FI SH), comparative genomic hybridization (CGH), spectral karyotyping (SKY) an d multicolor FISH (mFISH). Except for the basic research of human neoplasia s all these methods are used routinely to monitor the effect of the treatme nt and follow the residual tumor cells after chemotherapy and/or bone marro w transplantation.