RSPO3 and neoplasm: Additional targeting of Wnt signaling is applied in the case of inhibition of a single tumorigenic driver, a rare therapeutic opportunity in solid tumors, as previously mentioned; Storm and colleagues targeted a Wnt pathway component, RSPO3, in PTPRK-RSPO3-fusion positive colon tumors xenografts, which resulted in the initiation of differentiation, loss of stem cell function and inhibition of tumor growth (Storm et al., 2016).