The activity of the Akt pathway is counteracted by the PI(3,4,5)P3 phosphatase, PTEN, and mutations in or haploinsufficiency of PTEN are frequently observed in human tumours (Li et al, 1998; Cantley and Neel, 1999; Ramaswamy et al, 1999; Sun et al, 1999). This evidence concerns the gene PTEN and neoplasm.