Metformin inhibited Wnt/β-catenin signaling in both Caki-1 and Caki-2 renal cancer cells. Western blot analyses are shown for (A,B) Wnt3a, (C,D) p-LRP6 (Ser1490), (E,F) GSK-3β (Ser9) and (G,H) p-β-catenin (Ser33/37/Thr41) protein in Caki-1 and Caki-2 cells incubated in the absence (control) or presence of metformin (2, 5, and 10 mM). Images are representative of three independent experiments per group. (B,D,F,H) Histograms represent pooled densitometry data normalized to β-actin expressed as the percentage of control. Data are presented as mean ± SEM. * P < 0.05; ** P < 0.001; and *** P < 0.0001 vs. control.