Wnt signaling inhibitor FH535 selectively inhibits cell proliferation and potentiates imatinib-induced apoptosis in myeloid leukemia cell lines

Wnt signaling pathway plays a major role in leukemogenesis of myeloid leukemia. Aberrancy in its regulation results in hyperactivity of the pathway contributing to leukemia propagation and maintenance. To investigate effects of Wnt pathway inhibition in leukemia, we used human leukemia cell lines (i.e., K562, HL60, THP1, and Jurkat) and several Wnt inhibitors, including XAV939, IWP2 and FH535. Our results showed that leukemia cell lines (>95 % cells) had increased endogenous levels of β-catenin as compared to mononuclear cells from healthy donors (0 %). Among the tested inhibitors, FH535 demonstrated a markedly suppressive effect (IC₅₀ = 358 nM) on mRNA levels of β-catenin target genes (LEF1, CCND1, and cMYC). In addition, FH535 significantly potentiated imatinib-induced apoptosis. Evaluation of erythrocyte and megakaryocyte lineage using flow cytometry demonstrated that the potentiation mechanism is independent of the developmental stage, and is more likely due to crosstalk between other pathways and β-catenin. FH535 also displayed antiproliferative properties in other cell lines used in this study. In summary, FH535 showed significantly high antiproliferative effects at submicromolar dosages, and additionally enhanced imatinib-induced apoptosis in human leukemia cell lines. Our results highlight its potential antileukemic promise when used in conjunction with other conventional therapeutic regimens.