TP53 and cancer: In 2015, the Asian Cancer Research Group (ACRG) developed a new categorization based on gene expression data from 300 primary gastric tumors and identified four distinct subtypes: microsatellite stability/epithelial-mesenchymal transition (MSS/EMT), microsatellite-unstable tumors (MSI), microsatellite stable TP53-active (MSS/TP53+) and microsatellite stable TP53-inactive (MSS/TP53-) [14].