Incidence and Prognostic Impact of WT-1 Gene Exon7 and 9 Mutations in Acute Promyelocytic Leukemia

Wilms’ tumor gene 1 (WT1) gene mutation has been reported to be a prognostic factor in normalcytogenetic acute myeloid leukemia (AML) patients. Higher rates of mutation in the WT1 gene have been reported in several tumors including normal-cytogenetic AML patients. Data regarding WT1 mutations in acute promyelocytic leukemia (APL) is very scarce. In this study, we evaluated the incidence and impact of WT1 mutation on the outcome of APL patients.

A total of 92 patients diagnosed with APL were studied in three distinct groups: early mortality, relapsed, and persistent complete remission. Genomic DNA of bone marrow samples of patients was analyzed. For quantification of expression levels of the WT1 gene, real-time quantitative PCR (rqPCR) was performed by a real-time PCR system. WT1 mutation and its impact on prognosis were considered the primary endpoint of the study. Statistical analysis was performed with STATA.

WT1 mutation frequency was 6.25% in the early mortality group (1/16 patients), 13.16% in the relapse group (5/38 patients), and 7.89% in the persistent complete remission group (3/38 patients). 8 mutations were in exon 7 and one mutation in exon 9. WT1 mutation in the relapse group was associated with a trend toward worse disease-free survival (DFS) while overall survival (OS) was not affected by WT1 mutation in univariate analysis. Patients with no mutations in WT1 and FLT3/ITD had better overall survival and diseasefree survival compared to patients with mutations in the WT1 gene or FLT3/ITD in the relapse group.

The frequency of WT1 gene mutations does not differ significantly between patients with early mortality, relapse, and persistent complete remission. The presence of WT1 mutation is associated with higher relapse and lower survival rates in relapse group patients.