Expression of Wilms? tumor gene 1 at different stages of acute myeloid leukemia and analysis of its major splice variants

Abstract

WT1 is a transcription factor involved in differentiation and proliferation of acute myeloid leukemia (AML) blasts and is expressed in 90% of cases, as determined by nested reverse transcription polymerase chain reaction (RT-PCR). It is proposed to be a key molecule in leukemia promotion. To assess the relevance of WT1 expression, we analyzed blood and bone marrow samples from 58 AML patients (37 at diagnosis, 8 in hematological remission, and 13 at relapse) for the level of WT1 expression, using quantitative real-time RT-PCR. In addition, 21 randomly chosen samples were also analyzed for the quantitative expression of the main WT1 splice variants. As expected, samples from patients at the time of diagnosis or relapse showed significantly higher WT1 expression compared to samples from patients in remission or control samples. No striking difference in expression levels was found between various French-American-British (FAB) subtypes. The level of WT1 expression observed in patients at the time of initial diagnosis was similarly high in patients at relapse. Expression of the four main isoforms (E5+/KTS+, E5-/KTS+, E5+/KTS-, and E5-/KTS-) was found in all samples with significantly higher expression levels of the E5+ variants. Together, these findings support the potential of WT1 as a target for novel treatment approaches in AML.

Antiapoptotic function of 17AA(+)WT1 (Wilms' tumor gene) isoforms on the intrinsic apoptosis pathway

“…All of the four isoforms were expressed in primary human solid cancers, including lung cancer (Oji et al, 2002), HNSCC (Oji et al, 2003a), and sarcoma (Ueda et al, 2003) and human primary leukemia (Siehl et al, 2000). Among the four WT1 isoforms, WT1 17AA( þ )KTS( þ ) isoform was dominantly expressed in all of the cancers examined.…”

Real-time PCR quantification of major Wilms’ tumor gene 1 (WT1) isoforms in acute myeloid leukemia, their characteristic expression patterns and possible functional consequences

“…[28][29][30][31] In AML, significantly higher expression levels of EX5[ þ ] variants at diagnosis and at relapse have been detected. 26,32,33 In addition, the alternative AWT1 transcript has been found to be overexpressed in leukemia samples. 15,34 Functional studies suggest that many of WT1 effects are related to particular WT1 isoforms.…”

Wilms' tumor protein 1: an early target of progestin regulation in T-47D breast cancer cells that modulates proliferation and differentiation

“…The ratio of Wt1 splice variants was calculated essentially as described in Siehl et al (2004). It was assumed that splicing of the E5 and KTS exons was independent, and the relative C t values were adjusted for reaction efficiency.…”