DNA IN-SITU HYBRIDIZATION OF INDIVIDUAL COLONIES TO DETERMINE LINEAGEDERIVATION IN LEUKEMIA

The degree of lineage commitment of the hematopoietic stem cell in chr onic myelomonocytic leukemia (CMML) and in acute myelogenous leukemia (AML) remains debatable and may be heterogeneous depending on the pati ent subgroup. In this study, we have used a modification of DNA in sit u hybridization which adapts this technique to the analysis of karyoty pe in single hematopoietic colonies. By utilizing a digoxigenin-labele d chromosome 7 probe, we demonstrate that, in patients with monosomy 7 , both erythroid and myelomonocytic progenitors can be karyotypically aberrant. In addition, significant levels of diploid clonogenic cells persist (as reflected by the presence of between 14% and 43% diploid c olonies) despite the detection of only monosomy 7-bearing bane marrow metaphases as assessed by standard cytogenetic techniques. Our observa tions demonstrate that digoxigenin-based DNA in situ hybridization (DI SH) can be performed on individually microaspirated colonies for deter mination of lineage derivation. This technique may also be applicable to the detection of minimal residual disease with clonogenic potential and for assessing the interaction between normal and leukemic precurs ors.