γ-Catenin Overexpression in AML Patients May Promote Tumor Cell Survival via Activation of the Wnt/β-Catenin Axis

BACKGROUND: Canonical Wnt/β-catenin signaling is frequently dysregulated in acute myeloid leukemia (AML) and has been implicated in leukemogenesis. γ-catenin was previously demonstrated to be associated with the nuclear localization of β-catenin, the central mediator, and to exert oncogenic effects in AML; however, the underlying mechanisms remain unclear. Our study aimed to investigate the expression characteristics of γ-catenin in AML patients, explore the mechanisms by which γ-catenin regulates β-catenin, and discuss the feasibility of targeting γ-catenin for AML treatment. METHODS: The mRNA expression levels of γ-catenin in AML patients were measured by qRT-PCR. Cell proliferation was examined via Cell Counting Kit-8 (CCK-8) assays. The expression levels of related proteins were measured via Western blotting. Specific siRNA was used to modulate the expression level of the γ-catenin gene. Apoptosis and cell cycle distribution were quantified by flow cytometry. The subcellular localization of γ-catenin and β-catenin was examined via immunofluorescence with a confocal laser scanning microscope. RESULTS: Overexpression of γ-catenin was frequently observed in AML and correlated with poor prognosis. Consistent with this finding, suppression of γ-catenin in the AML cell line THP-1 induced growth inhibition, promoted apoptosis and blocked β-catenin nuclear translocation. Interestingly, γ-catenin knockdown sensitized THP-1 cells to cytotoxic chemotherapeutic agents such as cytarabine and homoharringtonine and further inhibited β-catenin nuclear localization. Moreover, our data implied the relationship between γ-catenin and GSK3β (whose effect on β-catenin is mediated by its own phosphorylation), which may be the principal mechanism underlying the anti-AML effect of γ-catenin inhibition. CONCLUSION: Taken together, our results revealed a potential role of γ-catenin in AML pathogenesis–mainly through the inhibition of GSK3β-mediated nuclear localization of β-catenin–and indicate that targeting γ-catenin might offer new AML treatments.