R-spondin-2, also known as RSPO2, synergizes with Wnt to activate beta-catenin. RSPO2 is secreted proteins that regulate beta-catenin signaling. Activator of the beta-catenin signaling cascade leads to TCF-dependent gene activation. Action both in the canonical Wnt / beta- catenin-dependent pathway, possibly via a direct interaction with Wnt proteins, and in a Wnt-independent beta catenin pathway through a receptor signaling pathway that may not use frizzled / LRP receptors. Probably also acts as a ligand for frizzled and LRP receptors. The encoding gene Rspo2 was identified as a novel common integration site for the mouse mammary tumor virus in viral induced mouse mammary tumors. Rspo2 and Rspo2 / Wnt1 tumors contained many spindle cells, consistent with an epithelial-mesenchymal transformation phenotype. When Rspo2 and Rspo2 / Wnt1 tumor cells were transferred into naive mice, they exhibited greater metastatic activity than cells derived from Wnt1 tumors.