Development of an Orthotopic Patient-Derived Xenograft Model of Gastro-Esophageal Adenocarcinoma: A Single-Lineage Pilot Study

Patient-derived xenografts (PDXs) preserve relevant histopathological and molecular characteristics of human tumors but, when implanted subcutaneously, poorly reproduce the native tumor microenvironment and patterns of metastatic dissemination. We developed a patient-derived orthotopic xenograft (PDOX) model of gastroesophageal junction (GEJ) adenocarcinoma based on the submucosal implantation of traceable tumor fragments. GFP/luciferase-labeled patient-derived GEJ adenocarcinoma organoids were propagated in mice as subcutaneous PDXs. Tumor fragments were then implanted into the gastric submucosal layer of seven NOD-SCID mice using a specifically developed surgical technique. Primary orthotopic tumor growth was qualitatively monitored longitudinally by in vivo IVIS imaging, whereas distant organ-associated bioluminescent signals were assessed ex vivo in excised organs at the experimental endpoint. Histopathological examination confirmed local orthotopic tumor growth. All procedures were completed without intraoperative or postoperative complications. Local tumor growth was observed in all xenografts. Distant organ-associated bioluminescent signals were detected in the liver and lungs, with an additional bowel-associated signal observed in one animal. These preliminary proof-of-concept findings demonstrate the technical feasibility of submucosal orthotopic implantation and longitudinal in vivo monitoring. However, given the small exploratory cohort and the use of a single patient-derived tumor lineage, the biological fidelity and generalizability of the model remain to be established in larger studies incorporating multiple independent tumors and comparative histopathological and molecular analyses.