[Drug Discovery Targeting an Amino Acid Transporter for Diagnosis and Therapy]

Nutrients are essential for all living organisms. Because growing cancer cells have strong metabolic demands, nutrient transporters are constitutively increased to facilitate the nutrient uptake. Among these nutrient transporters, L-type amino acid transporter 1 (LAT1), which transports large neutral amino acids including essential amino acids, is critical for cancer growth. Therefore, LAT1 has been considered as an attractive target for diagnosis and therapy of cancers. We have developed several lines of compounds for cancer diagnosis and therapy. To diagnose cancer by using positron emission tomography (PET) probes, we have created amino acid derivatives which are selectively transported by LAT1 and accumulated in cancer cells. In addition to amino acid derivatives as the LAT1 inhibitors, we also have made non-amino acid small compounds as anti-cancer drugs which inhibit LAT1 function and suppress tumor growth. The LAT1 targeting anti-cancer drug showed low toxicity but strong effects on various types of cancer cells in animal models. The novel PET probe is approved for clinical research and the new anti-cancer drug has been under clinical trial. Small compounds targeting the amino acid transporter bring us new tools for cancer diagnosis and therapy.