Clinical Significance of Quantitation of WT1 Gene Expression for Minimal Residual Disease Monitoring of Acute Myelogenous Leukemia / 대한진단검사의학회지

BACKGROUND: Following induction chemotherapy for AML, a sensitive determination of minimal residual disease (MRD) in patients achieving complete remission (CR) should enable the detection of early relapse. This study was designed to verify if quantitative assessment of the Wilms' tumor (WT1) gene by real time polymerase chain reaction (RQ-PCR) can be used as a marker for MRD detection during the monitoring of AML. METHODS: WT1 gene expression was quantified by RQ-PCR in 31 patients with AML at diagnosis (27 patients) and during follow-up (29 patients) relative to ABL control gene. In four patients, the WT1 gene expression was analyzed in comparison to a second PCR marker, PML-RARA fusion transcript. Prognostic significance of WT1 gene expression was analyzed at diagnosis and at the primary CR evaluation. Longitudinal WT1 gene analysis was performed in 17 AML patients. RESULTS: At diagnosis, WT1 gene expression exceeded the control level in all of the patients. Higher levels of WT1 gene expression were not associated with shorter event free survival or overall survival at diagnosis. Higher levels of WT1 gene expression were associated with shorter event free survival after induction chemotherapy. Relapse was observed in eight of 17 patients analysed longitudinally, and an increase of WT1 gene expression preceded morphologic relapse in four patients with the fusion transcript negative. Concomitant monitoring of PML-RARA fusion transcript reveals the lack of a significant correlation withWT1 gene expression. CONCLUSIONS: Quantitation of WT1 gene expression could be used for MRD monitoring of AML and for the early detection of relapse, especially in patients lacking specific molecular markers.

Prognostic Significance of WT1 Gene Expression in Patients with Acute Leukemia / 대한진단검사의학회지

BACKGROUND: The Wilms' tumor gene (WT1) is located on chromosome 11p13. Several authors have shown that the expression of WT1 gene is associated with prognosis of acute leukemia. It was the aim of this study to investigate the relationship between WT1 positivity and the response to treatment in terms of rate of complete remissions (CR), and survival and to evaluate the prognostic value of WT1 expression in patients with acute leukemia. METHODS: We examined the presence of WT1 specific mRNA in bone marrow samples of 71 patients with acute leukemia at diagnosis (AML 39, ALL 32) by nested RT-PCR. The integrity and the amount of RNA were analyzed by amplification of the -actin gene as an internal control. The relative ratio of WT1 gene expression/ -actin was calculated and classified as not amplified (0), weakly amplified (1+), moderately amplified (2+), or strongly amplified (3+). RESULTS: Thirty-four (47.9%) of the patients with acute leukemia at diagnosis were WT1 PCR positive. Among the WT1 positive patients, 10 patients (14.1%) showed 1+, 20 patients (28.2%) 2+, and 4 patients (5.6%) 3+. The patients with WT1 mRNA expression were younger than those without it in AML. There was a tendency of a higher CR rates in WT1 negative patients than in WT1 positive ones (AML 61.9% vs. 50%, ALL 75.0% vs. 68.8%). The probability of 5 year survival was 62.2% for WT1 negative group and 44.1% for WT1 positive group in all patients. The median survival days accord-ing to levels of WT1 expression was 709 days for negative group, 310 days for 1+ or 2+ groups and 294 days for 3+ group. CONCLUSIONS: The present data suggest a clinical relevance of WT1 expression for the achieve-ment of CR and long term survival in acute leukemia. Analysis of WT1 expression with bone mar-row aspirates at the diagnosis of acute leukemia may be useful to predict prognosis.