These compounds include 11C-acetate (a precursor of membrane fatty acids) in prostate cancer [112], 11C-methionine (a precursor of S-adenosylmethionine, which is required for polyamine synthesis) in brain tumor [113], 18F-choline (a substrate of choline kinase in choline metabolism) in prostate cancer [114], and 18F-3′-fluoro-3′-deoxy-L-thymidine (18F-FLT) (a substrate of thymidine kinase [TK-2] in DNA synthesis and a specific marker of cell proliferation) [115]. The gene discussed is TK2; the disease is prostate cancer.