PIK3CB and cancer: Characterization of two resultant helical and kinase domain mutant p110β proteins, E633K and D1067V, respectively, has revealed that these PIK3CB mutations activate PI3K-dependent signaling, increase cancer cell proliferation and promote tumourigenic growth.20,21 In a multicenter genome-wide sequencing study of metastatic castrate-resistant prostate cancer (mCRPC), Robinson et al.22 identified a small patient cohort with somatic mutations in PIK3CB, including two patients with mutations that result in an E1051K point mutation in the kinase domain of p110β.