PIK3CA and cancer: PI3K/AKT is one of the most frequently genetically dysregulated pathways in human cancers, due to somatic mutations and amplification of oncogenes such as PIK3CA (encoding the p110α catalytic subunit of class I PI3K) and AKT1, as well as inactivation of tumor suppressors such as phosphatase and tensin homolog (PTEN) and inositol polyphosphate 4-phosphatase type II (INPP4B) (1, 6).