Clinical significances of WT1 gene and AML1-ETO fusion gene expression for monitoring minimal residual disease in children with acute myeloid leukemia

Abstract

Objective To explore the diagnostic value of WT1 gene and AML1-ETO fusion gene in the monitoring of minimal residual disease (MRD) and prediction of relapse in childhood acute myeloid leukemia (AML). Methods From May 2007 to March 2015, a total of 13 AML1-ETO fusion gene positive AML children and 15 leukemia fusion gene negative AML children who received initial treatment in Department of Pediatrics in Sichuan Provincial People's Hospital were enrolled as study objects, and divided into fusion gene positive group (n=13) and fusion gene negative group (n=15). Relative expression levels of WT1 gene and AML1-ETO fusion gene were detected by real-time fluorescence quantitative reverse transcription-polymerase chain reaction (qRT-PCR) technique in bone marrow samples from children of two groups at the beginning of treatment and during follow-up period. Correlation of relative expression levels of WT1 gene and AML1-ETO fusion gene were analyzed by SPSS statistical software. The sensitivity, specificity, accuracy, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio of MRD predicting relapse were calculated and compared. Kaplan-Meier method was used to compare the relapse-free survival (RFS) rate between two groups and to assess MRD on the prediction of relapse. The study protocol was approved by the Ethical Review Board of investigation in Human Being of Sichuan Provincial People's Hospital.Informed consent was obtained from all participants. Results ①The relative expression levels of WT1 gene and AML1-ETO fusion gene were positively correlated in 83 bone marrow samples from 13 cases of fusion gene positive group (R2=0.874, P 0.05) at the time points of first diagnosis, first induction of remission, and relapse. ③After the first time induction of remission in the fusion gene positive group children, AML1-ETO quantitative levels as predictive relapse of diagnostic indicators were the highest in the sensitivity, accuracy, positive predictive value, negative predictive value as 85.7%, 76.9%, 75.0% and 80.0% respectively and negative likelihood ratio was minimum as 0.29. The specificity of WT1 gene in the fusion gene negative group was highest as 71.4%. ④After the first time induction of remission, there were 8 patients whose relative expression levels of AML1-ETO fusion gene were more than 0.01 in fusion gene positive group. Among these 8 cases, 6 patients relapsed and relapse rate was 75.0%. Relative expression levels of AML1-ETO fusion gene in other 5 cases were less than 0.01. Among the 5 cases, 1 patient relapsed and relapse rate was 20.0%. The difference of relapse rate between patents whose relative expression levels of AML1-ETO fusion gene were more and less than 0.01 was statistically significant (χ2=13.0, P=0.000). Up to the time of the follow-up , RFS rate of the patients with the relative expression level of AML1-ETO fusion gene more than 0.01 was significantly lower than that of patients with the relative expression level less than 0.01 (P=0.001). ⑤ After the first time induction of remission, there were 8 patients whose relative expression levels of WT1 gene were more than 0.01 in fusion gene negtive group. Among these 8 cases, 6 patients relapsed and relapse rate was 75.0%. Relative expression levels of WT1 gene in other 7 cases were less than 0.01. Among the 7 cases, 1 case relapsed and relapse rate was 14.3%. The difference of relapse rate between patients whose relative expression levels of WT1 gene were more and less than 0.01 was statistically significant (χ2=15.0, P=0.000). Up to the time of the follow-up , RFS rate of the patients with the relative expression level of WT1 gene more than 0.01 was significantly lower than that of patients with the relative expression level less than 0.01 (P=0.004). Conclusions AML1-ETO fusion gene is suitable for monitoring the MRD of AML children with fusion gene positive. WT1 gene is more suitable for detecting MRD and predicting relapse in AML children with fusion gene negative. It may indicate relapse when WT1 and AML1-ETO fusion gene relative expression levels significantly increased. Key words: Leukemia, myeloid, acute; gene, Wilms' tumor; AML1-ETO fusion gene, human; Neoplasm, residual; Polymerase chain reaction