RSPO1 and Ewing sarcoma: Recently, LGR5 was found to potentiate Wnt/β-catenin signaling in HEK293T cells[25] and in Ewing sarcoma[33], and LGR5 was found to function as a receptor of R-spondins to enhance Wnt-induced LRP phosphorylation[25, 31, 42] and then activate Wnt/β-catenin signaling.