Spotlight on the Diagnosis of Acute Promyelocytic Leukemia (AML-M3) Using Karyotyping, FISH and Quantitative Real-Time PCR

Objective: This study aimed to confirm the diagnosis of AML-M3 and the frequency of occurrence of the breakpoint cluster region (bcr1) in patients provisionaly diagnosed according to FAB classification. Cytologenetic and molecular genetics methods were used. Methods: Bone marrow (BM) or Peripheral Blood (PB) samples collected from 27 AML-M3 patients (During the period 2005 through 2007) were subjected to conventional karyotyping G-banding, detection of t (15;17) was performed by Fluorescence In Situ Hybridization (FISH) and PML-RARA gene rearrangements were detected by Quantitative Real-Time Reverse Transcriptase Polymerase Chain Reaction (QR-RT-PCR). Results: Karyotyping was successful in 24 out of 27 samples. Four patients out of 24 had a t (15;17), 17 had normal karyotype and 3 had other abnormalities. The results obtained by FISH technique corresponded with karyotype results and revealed positivity in another 3 samples. QR-RT-PCR demonstrated bcr1 positivity in the 4 patients diagnosed by Karyotyping with t (15;17) and in the 8 patients can not diagnosed by Cytogenetic methods. Conclusion: Despite the fact that cytogenetics permit the identification of many chromosomal changes within a sample, FISH analysis is more sensitive when the karyotype fails to find out the t (15;17). Furthermore, QR-RT-PCR appears to be the only suitable approach to detect the molecular events underlying hematological malignancies and provides informations on the correlation between different levels of disease at early phases of therapy and clinical outcome. Keywords: Acute promyelocytic leukemia (APL), karyotyping, Fluorescence In Situ Hybridization (FISH),quantitative Realtime reverse transcriptase polymerase chain reaction (QR-RT-PCR), PML/ RARA gene rearrangement Egypt. J. Hum. Genet Vol. 9 (1) 2008: pp. 121-13