PIK3CD and cancer: Activating mutations in the PIK3CA oncogene that encodes the p110α catalytic subunit of class Ia PI3K are common in a range of cancers, particularly breast, uterine, cervical and colorectal cancers, while mutations in other class I PI3K genes (PIK3CB, PIK3CD, PIK3CG) are less common [7, 8].