Since metabolites may serve as prognostic or predictive biomarkers, we aimed to explore the effect of drugs inhibiting several components of PI3K signalling (see Fig. 1) on metabolite levels in breast cancer cells in vitro to determine whether or not metabolic changes detectable using 31P-NMR spectroscopy robustly reflect Akt pathway inhibition. The gene discussed is PIK3CA; the disease is breast carcinoma.