Exposure to U0126 for 24 h reduced active β-catenin protein expression in parental MDA-MB468 and MDA-MB231 breast cancer cells (Supplementary Figure 4A and 4B), demonstrating that β-catenin is a downstream target of ERK1/2 suggesting that WNT5A-induced inhibition of ERK1/2 activity is a possible cause of its inhibitory effect on β-catenin in these cells. The gene discussed is MAPK3; the disease is breast cancer.