ESR1 and breast cancer: Suppressing IQGAP1-mediated PI3K signaling using a cell-permeable peptide, IQ3, which contains the PI3K binding motif on IQGAP1, inhibited the survival of human breast cancer cells, regardless of the status of ER expression or the presence/absence of gain-of-function mutations in the PIK3CA gene, which encodes for the catalytic subunit of PI3K [48].