Pharmacologic inhibition of Wnt3a signaling impedes tumor growth of OCI-Ly3 lymphoma. (A) Exposure of 6 × 10³ sorted OCI Ly3 SP- and 130 × 10³ nonSP cells to different agents modulated the canonical wnt pathway, showing no effect on the rare colony formation from non-SP cells by any agent. Enhanced colony formation from SP cells was observed by recombinant Wnt3a (100 ng/mL) and the GSK-3-β inhibitor SB-216763 (5 mM), in contrast to neutralizing antibody against Wnt3a (20 µg/mL) and tankyrase inhibitor XAV939 (5 µM) suppressing colony formation from SP cells (1-way ANOVA, **P < .05, ****P < 0001). (B) When added to growing tumors in ovo, XAV939 reduced gross tumor growth (right; 1-way ANOVA, P < .0001), associated with an increasing loss of tumor cell infiltrates in the stroma of the implants (left; hematoxylin and eosin stain, original magnification ×100). (C) Equimolar concentrations of the wnt palmitoylation inhibitor IWP2 and the axin2 inhibitor IWR1 inhibited colony formation from 5 × 10³ unsorted OCI Ly3 cells in semisolid media (1-way ANOVA, P < .0001). (D) Wnt inhibition by XAV939 reduced cellular β-catenin levels as detected by western blot. (E) XAV939 arrested cell proliferation compared with untreated or vehicle-treated controls (1-way ANOVA, ***P = .0041). DMSO, dimethylsulfoxide.