Background
Wnt/Fzd signaling is known to play a pervasive influence in hematopoietic stem cell maintenance, T-cell development in the thymus and function as well as an important role in T-cell acute lymphoblastic leukemia (T-ALL) establishment. We have previously described a recurrent rearrangement involving the WNT10Blocus (WNT10BR) expressing a transcript variant (WNT10BIVS1) in acute myeloid leukemia. To determine the occurrence of this rearrangement in T-ALL we analyzed retrospectively an italian cohort of patients (n=20) and detected the WNT10BRrearrangement with a high prevalence (14/20).
We also confirmed the relevance of these findings to human disease, detecting the molecular circuit triggered by the WNT10B over-expression using the MOLT-4 T-ALL cell model.In this report, we examined the expression of components of the Wnt signaling cascade mediated by WNT10B and the effects of specific gene silencing by short hairpin RNA (shRNA) and exposure to the potent PORCN inhibitor (LGK974), or the TGFbRI inhibitor (A83-01) on the WNT10B-mediated Wnt signaling activation.
Methods
We used the T-ALL model MOLT-4 cell line to assess the WNT10B/FZD signaling axis driven by WNT10BR. In order to identify interaction between WNT10B and FZD receptors we performed in situ proximity ligation assay (PLA) a method used to visualize protein-protein interactions.MOLT4 cells were infected with WNT10B/WNT10BIVS1-shRNA silencing lentiviral vectors versus empty vector control and treated with increased concentration of LGK974 or A83-01, subsequently the effects of pharmacological inhibition on the WNT10B/FZD interactions and on Wnt effector proteins were evaluated by PLA and expression analyses. Cell proliferation and cell death were measured by EdU assay and Annexin-V/Propidium Iodide (PI) analyses.
Results
We found that WNT10BRdrives Wnt signaling activity in T-ALL through interaction of WNT10B with FZD6 receptor. The effects of WNT10B/FZD6 interaction on Wnt-mediated signal in MOLT-4 were interfered by short hairpin RNAs (shRNAs)-mediated gene silencing and by small molecules-mediated disruption of Wnt-dependent signaling. We performed WNT10BIVS1knockdown or pharmacological inhibition of WNT10B release by the porcupine (PORCN) inhibitor LGK974 and these in turn progressively down-modulate WNT10B/FZD6 protein complex formation and significantly impairs intracellular effectors and leukemic expansion. Finally, we induced interference to the WNT10B/FZD6 protein complex formation by exposure to the TGFbRI inhibitor A83-01 via inhibiting FZD6 expression, confirming its role in the WNT10B-mediated signaling activation.
Conclusion
Our study describes the molecular circuit of WNT10BR-mediated activation and highlight a strategy for a major improvement in T-ALL treatment.By altering FZD6-WNT10B complex formation, may provide the basis for therapeutic strategies to eradicate leukemic stem cells in patients selectively deployed depending on the underlying genetics of disease.
Disclosures
No relevant conflicts of interest to declare.
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