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Published on: March 5, 2018
Molecular diagnostics of promyelocytic leukaemia
Janusz Kocki1, Maria Constantinou, Maria Cioch
1Department of Medical Genetics, Medical University of Lublin, Lublin, Poland. janusz.kocki@inetia.pl
Abstract:
Acute promyelocytic leukaemia (APL) is characterised by proliferation of abnormal promyelocytes. The reciprocal translocation between the long arms of chromosomes 15 and 17, and the fusion between the retinoic acid receptor (RARa) gene, and PML gene, is unique to APL. Because of unsuccessful cytogenetic analysis of conventional G-banding technique (mitoses were not observed), we diagnosed three non-treatment patients with APL by following molecular methods: reverse transcription-polymerase chain reaction (RT-PCR), fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH). At the time of diagnosis our patients showed reciprocal translocation t(15;17)(q22;q12) in all cases studied (66-85% of positive bone marrow cells). With the use of CGH we observed the unbalanced chromosomal aberrations: losses of 5q13.1, 5q31.3, 9p21 regions, gain of 5q32 region and trisomy of 18 chromosome.
Insights
Molecular methods diagnosed acute promyelocytic leukaemia (APL) in three patients when conventional cytogenetics failed. These methods identified the characteristic t(15;17) translocation and additional chromosomal abnormalities in APL.
Area of Science:
- Hematology
- Oncology
- Cytogenetics
Background:
- Acute promyelocytic leukaemia (APL) is a distinct subtype of leukaemia characterized by abnormal promyelocyte proliferation.
- A unique hallmark of APL is the reciprocal translocation t(15;17), leading to the fusion of the retinoic acid receptor alpha (RARa) and PML genes.
Purpose of the Study:
- To diagnose APL in patients where conventional G-banding cytogenetic analysis was unsuccessful due to lack of observable mitoses.
- To confirm the presence of the characteristic t(15;17) translocation and identify other chromosomal aberrations in APL patients using molecular techniques.
Main Methods:
- Reverse transcription-polymerase chain reaction (RT-PCR) for gene fusion detection.
- Fluorescence in situ hybridization (FISH) for chromosomal translocation analysis.
- Comparative genomic hybridization (CGH) for identifying copy number variations and chromosomal imbalances.
Main Results:
- The reciprocal translocation t(15;17)(q22;q12) was confirmed in 66-85% of bone marrow cells across all three diagnosed APL patients.
- Comparative genomic hybridization (CGH) revealed unbalanced chromosomal aberrations, including losses in regions 5q13.1, 5q31.3, and 9p21.
- Additional findings from CGH included a gain in the 5q32 region and trisomy of chromosome 18.
Conclusions:
- Molecular diagnostic methods like RT-PCR, FISH, and CGH are crucial for diagnosing APL, especially when conventional cytogenetics is limited.
- The study confirms the high prevalence of the t(15;17) translocation in APL.
- CGH identified specific unbalanced chromosomal aberrations associated with APL, providing further insights into the disease's genetic landscape.