UNLABELLEDThis study was aimed to explore the value of detecting the expression levels of MLL-AF9 (mixed lineage leukemia, MLL) fusion gene during the treatment of acute myeloid leukemia (AML) by real-time fluorescence quantitative PCR (RQ-PCR), and to evaluate its prognostic significance in monitoring minimal residual disease (MRD). The expression levels of 11 patients with MLL-AF9 fusion gene positive were detected precisely by RQ-PCR during the treatment in order to analyze the correlation of detection results with clinical manifestations. The results showed that the expression levels of MLL-AF9 fusion gene in patients at initial diagnosis were 1.3%-55.28%.

RESULTSobtained from 5 patients who received chemotherapy alone during the interval between first and second courses of chemotherapy indicated that 2 patients with <0.1% of MLL-AF9 fusion gene expression levels all achieved hematologic complete remission and survived, while the remaining 3 patients with ≥ 0.1% of MLL-AF9 fusion gene did not achieve hematologic complete remission and only 1 case survived. Moreover, results obtained from 6 transplant patients within a month before the transplantation suggested that 4 of them with < 0.1% of MLL-AF9 fusion gene expression levels survived without relapses, while the remaining 2 patients with ≥ 0.1% of MLL-AF9 fusion gene expression levels relapsed and died. Besides, MLL-AF9 fusion gene expression levels were ≥ 0.1% within one month before the morphological relapse of bone marrow in 2 recurrent patients. It is concluded that the detecting the expression level of MLL-AF9 fusion gene by RQ-PCR is an effective and accurate method to quantify and monitor the MRD level of MLL-AF9 gene positive AML patients and may be used for early detecting molecular relapse of AML.