We deleted the Trp53 gene with the use of the CRISPR-Cas9 system and then introduced the gene for K-RasG12V in tumor cells isolated from K19-Wnt1/C2mE mice, in which both Wnt and prostaglandin E2 signaling pathways are activated in the gastric mucosa [27] (Supplementary Figure 4A). Here, KRT19 is linked to neoplasm.