PIK3CA and neoplasm: The activities of these enzymes, and therefore inhibition of PI3K, can be assessed using metabolic imaging; for example, PET measurements of the uptake, phosphorylation, and trapping of the glucose analog, 2-deoxy-2-[18F]fluorodeoxyglucose ([18F]FDG), catalyzed by HK-II, and 13C magnetic resonance spectroscopy (MRS) measurements of hyperpolarized 13C label exchange between [1-13C]pyruvate and the endogenous tumor lactate pool, catalyzed by LDHA (Brindle, 2008).