PI3K inhibition-related G2/M arrest has been documented in glioblastoma and gastrointestinal carcinoma cells and can be explained by the fact that several important proteins in the regulation of the G2/M cell cycle checkpoint (e.g. Chk1, Wee1) have been identified as targets of PI3K19,21,61–63. The gene discussed is CHEK1; the disease is glioblastoma.