While Mesd was discovered as a specialized molecular endoplasmic reticulum (ER) chaperone for the Wnt co-receptors LRP5 and LRP6 [10], [11], recombinant Mesd protein is able to bind to mature LRP5 and LRP6 on the cell surface, acts as a universal inhibitor of different LRP5/6 modulators, and suppresses Wnt/β-catenin signaling in Wnt-dependent cancer cells [8], [12]–[14]. The gene discussed is LRP5; the disease is cancer.