Our group and others have shown that EGFR plays a key role in signal transduction pathways that drive the malignant phenotype (5–9), and suppression of EGFR signaling in breast cancer has been reported to control cancer growth by a few key mechanisms, including suppression of cancer stem cell populations (10–13), enhanced apoptosis via suppression of downstream MAPK/PI3K pathways (14–18), reversal of epithelial–mesenchymal transition (19), and converting an immunosuppressive tumor microenvironment to an immunoactive phenotype (20). This evidence concerns the gene PIK3CA and cancer.