Chromosomal heterogeneity of aneuploid leukemic cell populations detected by conventional karyotyping and by fluorescence in situ hybridization (FISH).

Beside the frequent aneusomies of chromosomes # 7 and # 8 gains or losses of several other chromosomes are found in bone marrow cells of leukemia patients. Chromosomal heterogeneity of interphase cell populations was studied by fluorescence in situ hybridization (FISH) with centromeric DNA probes for chromosomes #2, #3, #4, #6, #9, #11, #12, #15, #16, #17, #18, #20, as well as X and Y which were found to be aberrant by routine karyotyping of 28 cases of various malignant hematopoietic diseases. Particularly, the data obtained by both routes of analysis were compared quantitatively. As the most prominent result, all aberrations found by classical karyotyping were redetected by interphase cytogenetics, but additional aberrant clones could be observed among the interphase cell populations. The frequencies of the cell clones with hypersomies were in general higher in metaphase than in interphase, and, vice versa, monosomic cells were found more frequently in interphase than in metaphase. Single aberrant karyotypes in all cases were redetected as microclones of interphase cells. Interphase cytogenetics using FISH, therefore, was shown not only to be a reliable measure of the genomic heterogeneity of leukemic cell populations but, in addition, to be a valuable and informative supplement to routine leukemia cytogenetics with regard to the detection of microclones which, later on, could dominate the progression of the malignant disease.