Korean J Lab Med.  2007 Oct;27(5):305-312. 10.3343/kjlm.2007.27.5.305.

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

• Kim HR
• Shin JH
• Lee JN
• Lee EY

• KMID: 1781527
• DOI: http://doi.org/10.3343/kjlm.2007.27.5.305

Abstract

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.

Keyword

WT1 gene expression; Real time quantitative PCR; Acute myelogenous leukemia; Minimal residual disease

MeSH Terms

Adaptor Proteins, Signal Transducing/analysis
Adult
Aged
Aged, 80 and over
Female
Follow-Up Studies
Gene Expression
*Genes, Wilms Tumor
Humans
Leukemia, Myelomonocytic, Acute/*diagnosis/mortality/therapy
Male
Middle Aged
Neoplasm, Residual
Polymerase Chain Reaction
Prognosis
Survival Analysis
WT1 Proteins/*analysis/genetics

Figure

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  Fig. 1. WT1 amplication plot and standard curve. (A) Amplication plot of a 10-fold serial dilution of standard K562 cDNA (ranging from 10−5 to 100). The amplication plot shows an increase of reporter fluorescence during amplication. (x-axis, number of cycle; y-axis, relative fluorescence intensity). (B) Standard curve of K562 cDNA dilution for real-time PCR. The standard curve shows a linear correlation between the Ct value (y-axis) and the logarithm of the initial concentration of the standard K562 cDNA (x-axis).

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  Fig. 2. WT1 expression at diagnosis (N=27) according to FAB subtypes.

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  Fig. 3. WT1 expression at diagnosis (n=27) according to different molecular or cytogenetic prognostic subgroups of AML. Favorable: t(15;17), t(8;21), t(16;16); Intermediate: +8, +11, t(12;18) and normal karyotype; Adverse: −7, del(11)(q23), and complex karyotype as the presence of 3 or more abnormalities.

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  Fig. 4. Kaplan-Meier plot of event free survival of patients with WT1 expression above or below 0.001.

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  Fig. 5. Longitudinal monitoring of WT1 level in four exemplary patients with relapse. Arrows on the top of the graph indicate the time points of hematologic relapse.

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