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Published on: January 28, 2014
Delimiting the use of comparative genomic hybridization in human myeloid neoplastic disorders
E Gebhart1, I Verdorfer, W Saul
1Institute of Human Genetics, University of Erlangen-Nurnberg, D-91054 Erlangen, Germany.
Insights
Comparative genomic hybridization (CGH) reliably detects genomic imbalances in myeloproliferative disorders. This technique can identify deletions as small as 5-7 Mb, even in cases with low mosaicism.
Area of Science:
- Genetics
- Hematology
- Oncology
Background:
- Hematopoietic disorders provide a valuable model for assessing the resolving power of comparative genomic hybridization (CGH).
- Classical cytogenetic techniques are standard for diagnosing myeloproliferative disorders but have limitations in detecting subtle genomic changes.
Purpose of the Study:
- To evaluate the diagnostic utility and resolving power of CGH in myeloproliferative disorders.
- To determine the minimum level of mosaicism and deletion size detectable by CGH in these conditions.
Main Methods:
- Comparative genomic hybridization (CGH) was performed on DNA from 38 myeloproliferative disorders (23 acute, 15 chronic).
- CGH analysis was repeated with reversely labeled probes in most cases for validation.
- Image analysis system (ISIS 3) on a Zeiss axioplan microscope was used for photometric evaluation.
Main Results:
- CGH successfully detected target anomalies in all cases with an affected cell population of 23% or higher.
- The lowest detection limit was 23% in a case with a 20q deletion.
- Smallest detectable deletions were estimated at 5-7 Mb (two bands on 20q), and CGH identified imbalances missed by routine cytogenetics.
Conclusions:
- CGH is a reliable and sensitive technique for studying human leukemia and myeloproliferative disorders.
- The study clarifies the resolving power of CGH, demonstrating its capability to detect clinically relevant genomic imbalances.
- Reverse labeling confirmed the reproducibility and accuracy of CGH findings.
Abstract:
Hematopoietic disorders can be used as a suitable tool of additional information on the actual resolving power of comparative genomic hybridization (CGH). Therefore, CGH examination was performed of DNA extracted from 23 acute and 15 chronic myeloproliferative disorders which had just been analyzed using classical cytogenetic techniques. In nearly all cases CGH analysis was repeated with reversely labeled probes. A Zeiss axioplan microscope was equipped with the ISIS 3 system for photometric evaluation of the CGH data. A main group was selected of 34 cases showing karyotypic mosaics when routinely diagnosed by classical cytogenetics. The grade of mosaicism was basically 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 informative genomic imbalance could be analyzed. Every target anomaly irrespective of its type could be detected in all cases with an affected cell population 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 deletion. The smallest deletions of two bands on 20q which could visually be detected 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 reliability of CGH studies on human leukemia, but also further contribute to a clearer definition of the limits of the resolving power of this technique.
