Pten deletion in the hematopoietic stem cells (HSC) causes a
myeloproliferative disorder, which may subsequently develop into a T-cell
acute lymphoblastic leukemia (
T-ALL). β-
catenin expression was dramatically increased in the c-KitmidCD3+Lin-
leukemia stem cells (LSC) and was critical for
T-ALL development. Therefore, the inactivation of β-
catenin in LSC may have a potential to eliminate the LSC. In this study, we investigated the mechanism of enhancement of the β-
catenin expression and subsequently used a
drug to inactivate β-
catenin expression in
T-ALL. Western blot (WB) analysis revealed an increased level of β-
catenin in the leukemic cells, but not in the pre-leukemic cells. Furthermore, the WB analysis of the thymic cells from different stages of
leukemia development showed that increased expression of β-
catenin was not via the pS9-GSK3β signaling, but was dependent on the pT308-Akt activation.
Miltefosine (
Hexadecylphosphocholine) is the first oral anti-Leishmania
drug, which is a
phospholipid agent and has been shown to inhibit the PI3K/Akt activity. Treatment of the PtenΔ/Δ leukemic mice with
Miltefosine for different durations demonstrated that the pT308-Akt and the β-
catenin expressions were inhibited in the
leukemia blast cells.
Miltefosine treatment also suppressed the TGFβ1/Smad3 signaling pathway. Analysis of TGFβ1 in the sorted subpopulations of the blast cells showed that TGFβ1 was secreted by the CD3+CD4- subpopulation and may exert effects on the subpopulations of both CD3+CD4+ and CD3+CD4-
leukemia blast cells. When a TGFβR1 inhibitor,
SB431542 was injected into the PtenΔ/Δ leukemic mice, the Smad3 and β-
catenin expressions were down-regulated. On the basis of the results, we conclude that
Miltefosine can suppress
leukemia by degrading β-
catenin through repression of the pT308-Akt and TGFβ1/Smad3 signaling pathways. This study demonstrates a possibility to inhibit Pten loss-associated
leukemia genesis via targeting Akt and Smad3.