For example, [18F]-FDG PET has been shown to be a surrogate marker of sensitivity to PI3K inhibition by NVP-BEZ235 and NVP-BKM120 in human HNSCC (FaDu) and mouse mammary (EMT6) 3D tumour spheroids in vitro[54], and of response following 100 mg/kg LY294002, 10 mg/kg PF-04691502 or 35 mg/kg NVP-BEZ235 in colorectal, lung and ovarian tumour xenografts and/or mouse models in vivo[12], [17], [55]. The gene discussed is PIK3CA; the disease is head and neck squamous cell carcinoma.