KLK7 and gastric cancer: Recent study showed that molecular classification dividing gastric cancer into four subtypes: (1) tumors positive for Epstein–Barr virus, which display recurrent PIK3CA mutations, (2) extreme DNA hypermethylation, (3) amplification of JAK2, CD274 (PD-L1) and PDCD1LG2 (PD-L2); (4) microsatellite unstable tumors (Microsatellite instability, MSI), which show elevated mutation rates, including mutations of genes encoding targetable oncogenic signalling proteins [27].