ESR1 and breast cancer: Previously reported gene expression analysis of 249 ERα+ breast cancers revealed upregulation of several Wnt pathway genes (TCF7L2, MSX2, WNT5A, and TNFRSF11B) in PIK3CA-mutant versus wild-type tumors44, suggesting there may be a functional link between PI3Kα and Wnt signaling in ER+ breast cancer.