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 losse s of several other chromosomes are found in bone marrow cells of leuke mia patients. Chromosomal heterogeneity of interphase cell populations was studied by fluorescence in situ hybridization (FISH) with centrom eric 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 di seases. Particularly, the data obtained by both routes of analysis wer e compared quantitatively. As the most prominent result, all aberratio ns found by classical karyotyping were redetected by interphase cytoge netics, but additional aberrant clones could be observed among the int erphase cell populations. The frequencies of the cell clones with hype rsomies were in, general higher in metaphase than in interphase, and, vice versa, monosomic cells were found more frequently in interphase t han in metaphase. Single aberrant karyotypes in all cases were redetec ted as microclones of interphase cells. Interphase cytogenetics using FISH, therefore, was shown not only to be a reliable measure of the ge nomic heterogeneity of leukemic cell populations but, in addition, to be a valuable and informative supplement to routine leukemia cytogenet ics with regard to the detection of microclones which, later an, could dominate the progression of the malignant disease.