ANPEP and lung cancer: Kuriki et al. found promising probes lysine-histidine-HMRG (KH-HMRG) for gastric cancer (negative staining) and lysine-lysine-HMRG (KK-HMRG) for lung cancer from among 380 types of HMRG-based fluorescent probes, which detect tumor tissues with high expression of puromycin-sensitive aminopeptidase (PSA) and aminopeptidase N (APN), respectively (22).