Small molecule inhibitors of WNT signaling effectively induce apoptosis in acute myeloid leukemia cells

Abstract

In a significant proportion of acute myeloid leukemia (AML) cases the canonical WNT pathway is upregulated and targeting the WNT/LEF1 signaling cascade in AML may be a promising approach to develop new treatments for this entity. Recently two compounds (CGP049090 and PFK115-584) have been identified, which specifically inhibit complexation of beta-catenin (CTNNB1) and lymphoid enhancer-binding factor 1 (LEF1) leading to transcriptional inactivation of LEF1 in colon carcinoma cell lines. To evaluate the effect of WNT inhibition utilizing theses compounds with regard to their effectivity in AML we treated the AML cell lines Kasumi-1 and HL-60, primary AML blasts and healthy peripheral blood mononuclear cells (PBMCs) with varying concentrations of both substances. Treatment with both compounds for 24 h resulted in a significant killing of AML cell lines and primary AML blasts with 50% effective concentration doses (EC(50)) within the submicromolar range. PBMCs were not significantly affected as indicated by EC(50)-values 100-fold higher than for AML cells. Cell kill was mediated by apoptosis as indicated by induction of caspases 3 and 7 and cleavage of poly(ADP-ribose) polymerase (PARP) upon treatment. Furthermore, we could show that both compounds substantially decrease expression of CTNNB1/LEF1 target genes c-myc, cyclin D1 and survivin, proofing the specificity of the substances. This was shown in both, AML cell lines and most of the tested primary samples. Our data demonstrate that targeting this pathway seems to be an innovative approach in the treatment of AML.

β-Catenin signaling is required for TGF-β1-induced extracellular matrix production by airway smooth muscle cells

“…The experiments performed with the pharmacological inhibitor PKF115-584 indicate that at least TCF-4 plays an important role in the regulation of versican, collagen I␣1, and fibronectin expression by airway smooth muscle cells, since this inhibitor disrupts the interaction between nuclear ␤-catenin and TCF-4 (4,47,52). This fits with observations that indicate abundant expression of the TCF-4 transcription factor by mesenchymal cells (7,11).…”

“…To further verify the functional role of ␤-catenin/TCF interactions in TGF-␤ 1 -induced ECM gene expression, we pharmacologically inhibited ␤-catenin signaling by PKF115-584 a compound that disrupts the interaction of the transcriptionally active (nonphosphorylated) ␤-catenin/T-cell factor-4 (TCF-4) complex (4,47,52). In line with the findings obtained with ␤-catenin siRNA, PKF115-584 did not significantly affect basal expression of collagen I␣1 (P ϭ 0.432), fibronectin (P ϭ 0.693), or versican (P ϭ 0.394) but largely attenuated the TGF-␤ 1 -induced expression of these ECM genes (Fig.…”

Overexpression of LEF1 predicts unfavorable outcome in adult patients with B-precursor acute lymphoblastic leukemia

“…Furthermore, patients with high LEF1 expression should be considered for new molecular directed therapies, especially agents targeting the Wnt pathway 39 or demethylating drugs. 12 Recently, 2 small molecules have been identified that specifically inhibit the LEF1/␤-catenin complex and have shown promising in vitro efficacy in AML cell lines.…”

“…12 Recently, 2 small molecules have been identified that specifically inhibit the LEF1/␤-catenin complex and have shown promising in vitro efficacy in AML cell lines. 6,39 Of note, most relapses in B-precursor ALL patients with high LEF1 expression occurred early within the first year of remission, underlining the importance of adapted first-line therapies for this particular high-risk group. As Wnt signaling has been implicated in self-renewal of leukemic stem cells, [40][41][42] early relapse of patients with LEF1 overexpression might reflect a survival advantage of leukemic stem cells because of LEF1 expression.…”

High expression of lymphoid enhancer-binding factor-1 (LEF1) is a novel favorable prognostic factor in cytogenetically normal acute myeloid leukemia

“…2,33,34 Leukemogenic fusion genes and gene mutations can induce Wnt signaling in AML, aberrant activation of the Wnt effector ␤-catenin has been detected in primary AML samples, and small-molecule Wnt pathway inhibitors are cytotoxic for AML blasts. 3,5,35 Our group previously showed that overexpression of Lef-1 in murine BM leads to disturbed hematopoiesis and, ultimately, to the development of myeloid and lymphoid leukemias. 10 Interestingly, the myeloid leukemias arising in this model originated from a leukemic stem cell with lymphoid characteristics and showed coexpression of lymphoid markers.…”