BHLHA15 and neoplasm: The process of establishing an organoid-transplanted s.c. tumour-derived MGA cell line is shown in Fig. 1A. Normal wild-type (WT) gastric epithelial organoids were isolated from Trp53flox/flox;Cdh1flox/flox;Mist1-CreER C57BL/6 J mouse and induced into Trp53−/−Cdh1−/− (tc−/−) mouse GC organoids ex vivo.