Delimiting the use of comparative genomic hybridization in human myeloid neoplastic disorders

Hematopoietic disorders can be used as a suitable tool of additional inform ation on the actual resolving power of comparative genomic hybridization (C GH). Therefore, CGH examination was performed of DNA extracted from 23 acut e and 15 chronic myeloproliferative disorders which had just been analyzed using classical cytogenetic techniques. In nearly all cases CGH analysis wa s repeated with reversely labeled probes. A Zeiss Axioplan microscope was e quipped with the ISIS 3 system for photometric evaluation of the CGH data. A main group was selected of 34 cases showing karyotypic mosaics when routi nely diagnosed by classical cytogenetics. The grade of mosaicism was basica lly determined from the classical cytogenetic analysis and was additionally defined examining target anomalies by I-FISH analysis in 28 of the cases. The second group included 23 cases with deletions, and in 1 case another in formative genomic imbalance could be analyzed. Every target anomaly irrespe ctive of its type could be detected in all cases with an affected cell popu lation equalling or exceeding about 25%, but in none was it below 23%. This value was the lowest and was found in a case, with CGH-detected 20q deleti on. The smallest deletions of two bands on 20q which could visually be dete cted by CGH were estimated in the range of 5-7 Mb. CGH was also suitable to detect imbalances which were not clearly detected by routine cytogenetics. Reverse labelling, performed in nearly all cases, confirmed the result of the original CGH analysis. These data not only document the readiness and r eliability of CGH studies on human leukemia, but also further contribute to a clearer definition of the limits of the resolving power of this techniqu e.