With regard to activation of the canonical Wnt pathway, we observed that RSPO3‐driven breast tumors expressed the Wnt/β‐catenin target genes Axin2, Wif1, Znrf3, and Ctnnb1 itself, however at significantly lower levels than their WNT1‐driven counterparts (Figure 4C). Here, WIF1 is linked to breast neoplasm.