PIK3CA mutant ER+ breast cancers exhibit an RNA expression profile of enhanced Wnt/β-catenin signaling, including up-regulation of Wnt target genes (AXIN2, LEF1, MYCN) and other components such as transcriptional regulators (TCF7L1, TCF7L2, CTNNB1), receptors (FZD4, FZD7) and ligands (WNT5A). Here, CTNNB1 is linked to breast cancer.