Background. Despite a considerable effort, the majority of acute myeloid leukaemia (AML) patients do not have
a suitable specific molecular marker for monitoring minimal residual disease (MRD). The results of some studies suggest
the Wilms tumour gene (WT1) as a possible molecular marker of MRD.
Methods and Results. We measured the expression of WT1 at diagnosis and during treatment of the acute myeloid
leukaemia (AML) patients. The expression of WT1 was measured by the quantitative real-time RT-PCR in peripheral
leukocytes from 56 AML at diagnosis and 7 patients with AML transformed from myelodysplastic syndromes
(MDS). The WT1 expression was significantly elevated (up to 3 orders of magnitude) in peripheral blood samples
(PB) of AML patients at diagnosis compared to PB samples of healthy donors (P<0.0001). The level of WT1 expression
depends particularly on FAB AML subtype, with the highest being found in AML patients with subtypes M4,
M1, M3 and AML transformed from MDS. Conversely, AML patients with M2 and with the presence of AML1/ET0
at presentation showed a significantly lower expression of the WT1 gene compared to the remaining AML patients at
presentation (P = 0,005). Further, sequence samples of 12 AML patients under long-term surveillance were tested for
the WT1 expression in parallel with the expression of specific MRD markers - fusion genes: AML1/ETO,
PML/RARα and CBFB/MYH11. The levels of WT1 gene expression and the above specific fusion genes significantly
correlated. Moreover, 14 patients without the specific MRD marker were tested for the WT1 expression. The
results show that haematological relapses were associated with the rise of expression of the specific fusion genes and
with the WT1 gene expression. The rise of WT1 expression above the level seen in leucocytes from peripheral blood
and/or bone marrow of healthy donors – in four patients under long-term surveillance the „molecular relapse” predicted
ongoing haematological relapses as early as 2 months in advance.
Conclusions. Our results, in accordance with some of the previously published ones, show that WT1 expression
seems to be a suitable marker of minimal residual disease in AML patients.
leukemia, acute myeloid leukaemia, Wilms tumor 1, minimal residual disease.