[Correlation of FLT3 gene expression level and internal tandem duplication mutation in acute myeloid leukemia and its clinical significance].

Objective: To evaluate the prevalence of FLT3 gene expression and internal tandem duplication (ITD) mutation in acute myeloid leukemia (AML) patients and its clinical significance.

Methods: The expression level of FLT3 mRNA was detected with real-time quantitative RT-PCR (RQ-PCR) technique in 152 bone marrow samples from 129 AML patients. The ITD of the FLT3 gene (FLT3/ITD) was detected in 75 de novo AML patients by reverse transcription polymerase chain reaction (RT-PCR).

Results: The expression levels of FLT3 mRNA was 0.0020(0.0006 - 0.0040) in normal controls, and 0.1041 (0 - 33.8736) in 80 de novo AML patients (P = 0.001). FLT3/ITDs were found in 11 (14.7%) of 75 de novo AML patients. The FLT3 expression levels in patients with FLT3/ITD were 0.0297 to 33.8736 with a median level of 0.2200, and in those without FLT3/ITD were 0 to 26.2200 with a median level of 0.0975. The FLT3 expression levels in the former patients were higher than that in the latter ones, but there was no statistical significance (P = 0.093). The complete remission (CR) rate was lower in acute promyelocytic leukemia (APL) patients with FLT3/ITD than in APL patients without FLT3/ITD (P = 0.015). In de novo AML other than APL patients without FLT3/ITD, the CR rate was lower in patients with higher levels of FLT3 expression (expression level > 0.04, CR rate 37.5%) than those with lower levels of FLT3 expression (expression level < 0.04, CR rate 100%). On follow-up of 20 patients, the FLT3 expression level was decreased at least one logarithm degree when they got CR, but it was no significant change in non-remission patients.

Conclusions: Quantification of FLT3 mRNA expression level and detection of FLT3/ITD in AML patients may serve as an index for evaluating therapeutic efficacy, predicting prognosis, and monitoring minimal residual disease.