PIK3CA and neoplasm: The PIK3CA gene encoding PI3Kα is commonly mutated (Samuels et al., 2004), rendering tumours more dependent on PI3Kα signalling (Liu et al., 2011; André et al., 2019), whereas loss of the tumour suppressor PTEN confers PI3Kβ dependency (Jia et al., 2008; Wee et al., 2008).