Gastric organoid tumor explants. Gastric organoids with the indicated genotypes are shown. (a) Tumor volumes were measured over time post-injection and plotted according to genotype of the driver combinations being tested. This includes Cdh1-/-;Trp53-/- as shown in blue and Cdh1-/-;Trp53-/-;Tgfbr2 shRNA as shown in red. Error bars represent SEM. Asterisk (*) indicates P <0.01 for Cdh1-/-;Trp53-/-;Tgfbr2 shRNA compared to Cdh1-/-;Trp53-/- tumor volumes. (b, c) With different driver combinations, transformed gastric organoids were dissociated and subcutaneously (s.c.) injected into the flanks of immunodeficient NOG mice. Images indicated tumor growth at 30×days post injection. (d, e) Histological analysis of tumors confirms the presence of poorly differentiated adenocarcinoma with signet ring features, as indicated by the yellow arrows, only in the Cdh1-/-;Trp53-/-;Tgfbr2 shRNA organoids. After flank injections with dissociated organoids, histological analysis of murine lungs after 30×days revealed metastatic gastric adenocarcinoma with signet ring features at low (f) and high (g) magnification.