Abstract
A well-established preclinical model of pancreatic cancer needs to be established to facilitate research on new therapeutic targets. Recently established animal models of pancreatic cancer, including patient-derived tumor models and organoid models, are used for pre-clinical drug testing and biomarker discovery. These models have useful characteristics over conventional xenograft mouse models based on cell lines in preclinical studies, but still cannot accurately predict the clinical outcomes of new treatments and have not yet been broadly implemented in research. We employed pancreatic cancer organoid culture methods using the pancreatic cancer cell line S2-013, and performed pathological and immunohistochemical analyses to characterize tumor xenografts obtained from a mouse model implanted with S2-013 cell line-derived organoids. Serum levels of the pancreatic cancer tumor marker CA19-9 were measured by ELISA. We generated human pancreatic cancer organoids using a co-culture of S2-013 cells, human endothelial cells derived from human umbilical vein endothelial cells, and human mesenchymal stem cells, and established a mouse model with subcutaneously transplanted human pancreatic cancer organoids (S2-013-organoid model). Although blood clotting crater-like formation developed in the middle of subcutaneous xenografts in the S2-013-conventional model, created by subcutaneously injecting S2-013 cells into the right flank of nude mice, the size of xenografts in the S2-013-organoid model gradually increased without crater-like formation. Importantly, tumor xenografts obtained from the S2-013-organoid model exhibited a clinical human pancreatic cancer tissue-like cellular morphology, tissue architecture, and polarity, and actively formed cancer stroma containing mature blood vessels with the high expression of the vascular tight junction marker CD31. In subcutaneous xenografts of S2-013-conventional mice, no blood vessel density or widely expanding areas of necrotic regions were present. Consequently, serum levels of CA19-9 in the S2-013-organoid model correlated with tumor volumes. In addition, epithelial-mesenchymal transition, the conversion of epithelial cells to the mesenchymal phenotype, was observed in tumor xenografts of the S2-013-organoid model. The S2-013-organoid model provides tumor xenografts consisting of clinical human pancreatic cancer-like tissue formation with the effective development of vascularized stroma, and may be valuable for facilitating studies on pre-clinical drug testing and biomarker discovery.