DNA in situ hybridization of individual colonies to determine lineage derivation in leukemia

The degree of lineage commitment of the hematopoietic stem cell in chronic myelomonocytic leukemia (CMML) and in acute myelogenous leukemia (AML) remains debatable and may be heterogeneous depending on the patient subgroup. In this study, we have used a modification of DNA in situ hybridization which adapts this technique to the analysis of karyotype in single hematopoietic colonies. By utilizing a digoxigenin-labeled 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 colonies) despite the detection of only monosomy 7-bearing bone marrow metaphases as assessed by standard cytogenetic techniques. Our observations demonstrate that digoxigenin-based DNA in situ hybridization (DISH) can be performed on individually microaspirated colonies for determination 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 precursors.