Diagnostic value of FISH combined with multiplex RT-PCR for detection of MLL rearrangement

AIM:To analyze the diagnostic value of fluorescence in situ hybridization(FISH) combined with reverse transcription-multiplex nested PCR(multiplex RT-PCR) for the detection of mixed-lineage leukemia(MLL) gene rearrangement from bone marrow aspirate in the patients with acute leukemia.METHODS: The bone marrow samples were obtained from 201 newly diagnosed acute leukemic patients in our hospital.MLL gene rearrangement was detected by both FISH and multiplex RT-PCR methods.FISH with the MLL dual color break-apart probe was performed following the procedures recommended by the manufacturer.Eleven common fusion transcripts of MLL were also determined by multiplex RT-PCR assay.Conventional cytogenetic analysis(CCA) was performed on all specimens to observe the abnormality of 11q23.RESULTS: MLL gene rearrangement was observed in 19 patients,including 13 cases(10.2%) of acute myeloid leukemia(AML) and 6 cases(8.2%) of acute lymphoid leukemia(ALL).Among the MLL positive specimens,the rate of MLL rearrangement detected by FISH combined with multiplex RT-PCR was 9.45%,but 5.47% by CCA merely.One case of MLL inversion and 3 cases of MLL amplification were found in 5 patients with normal karyotype and 3 patients with cytogenetic abnormalities uninvolving chromosome 11.Multiplex RT-PCR revealed 7 cases of dup(MLL) which failed to show in FISH and CCA.CONCLUSION: The combination of FISH and multiplex RT-PCR increases the sensitivity for detection of MLL rearrangement.