[Imaging of biological character of cancer using positron emission tomography(PET)]

There are two types of radiopharmaceuticals for cancer imaging with PET. The first target is a marker of cancer proliferation, and positron-labeled analogs of glucose, amino acid, and nucleic acid are commonly used for this purpose. 18F-FDG is a typical tracer of this approach. The second target is visualization of cancer-specific biological characters. In Tohoku University, we developed 18F-fluorodeoxygalactose(18F-FDGal), 18F-SAV03M, and 18F-FRP170 as tracers of the second category. 18F-FDGal is metabolized and trapped in the tissue by liver-specific galactose metabolic enzymes. It is used for detecting well-differentiated hepatocellular carcinoma which originated from liver cells and still maintains the enzymes. 18F-SAV03M is a substrate for matrix metalloproteinase-2 and was developed for the visualization of tumor invasiveness. 18F-FRP170 was developed for the visualization of hypoxic cancer cells which cause radiotherapy and chemotherapy resistance. In addition, the uses of labeled antisense oligonucleotide and aptamers were introduced for the visualization of specific mRNA and proteins expression.