Combination of cytogenetic analysis and molecular screening in patients with de novo acute myeloid leukemia.

Nowadays the role of genetic findings in determining the diagnosis, therapy and prognosis of acute myeloid leukemia (AML) has become more valuable. To improve and validate the detection of clonal chromosomal aberrations in leukemia, we designed a combined application of karyotyping with multiplex reverse transcription-polymerase chain reaction (RT-PCR) and fluorescence in situ hybridization (FISH), and addressed the expression and distribution of fusion genes among the subtypes of Chinese adult patients with de novo AML. Multiplex RT-PCR assays were performed on 477 samples from newly diagnosed AML patients, and cytogenetic data were obtained from 373 of them by R or G banding techniques and those in some cases were confirmed by FISH. The PCR products in some suspected cases were tested by two-directional sequencing. The results showed that except unqualified samples, fusion genes were detected by multiplex RT-PCR in 211 of 474 patients (44.51%), including AML1-ETO, CBFβ-MYH11, PML-RARα, PLZF-RARα, NPM-RARα, MLL rearrangements, BCR-ABL, DEK-CAN, SET-CAN, TEL-PDGFR, TLS-ERG, AML1-MDS1 (EVI-1). In 373 patients, who took both multiplex RT-PCR and karyotype analysis, the detection rate of chromosomal aberrations by using multiplex RT-PCR and karyotyping was 160/373 (42.89%) and 179/373 (47.98%) respectively, and the combination could optimize the detection rate of clonal genetic abnormalities to 216/373 (57.90%). The PCR results from 11 cases "normal" in karyotyping but abnormal in RT-PCR for MLL rearrangements were confirmed by two-directional sequencing. It is concluded that karyotype studies remain the cornerstone for genetic testing; conventional cytogenetics and molecular-based methods are complementary tests for the detection of clonal genetic aberrations in AML, especially for the cryptic or submicroscopic aberrations. Once a genetic marker has been identified by combined analysis, it could be used to monitor residual disease during/after chemotherapy, by quantitative RT-PCR and/or FISH.