Class I PI3Ks are divided into four catalytic isoforms, p110α, p110β, p110γ and p110δ, and they are encoded by PIK3CA, PIK3CB, PIK3CG and PIK3CD, respectively.3 Among the four class I catalytic isoforms, PIK3CA is mentioned commonly in human cancer due to its frequent mutations.6 The time point of pathway activation varies among cancer types and patients. This evidence concerns the gene PIK3CB and cancer.