A New Chemical Carcinogenesis Model Using Normal Canine Bladder Organoids

<p>It is important to clarify the mechanism of carcinogenesis by chemical substances in order to explore methods for cancer prevention and treatment. However, the number of chemical substances is enormous, and searching for them in conventional long-term carcinogenicity tests is time-consuming and labor-intensive. Therefore, we focused on a 3D organoid culture method that can reproduce in vivo epithelial tissue structure and gene expression patterns on a culture dish. Our laboratory has established a method for culturing cancer stem cells or canine bladder cancer organoids in the urine of dogs with bladder cancer. Furthermore, we have succeeded in producing canine normal bladder organoids from bladder mucosa cells noninvasively collected from healthy dogs. In this study, we treated canine normal bladder organoids with bladder carcinogens (2-Acetylaminofluorene and N-Butyl-N-(4-hydroxybutyl)nitrosamine) for 6 days, respectively, and then examined cancer stem cell markers (CD 44) and a DNA damage marker (γ-H2AX), which has been focused on in the early detection of bladder cancer. In addition, we evaluated the tumorigenic potential of the chemical-treated organoids by transplanting them into immunocompromised mice, and verified the usefulness of canine normal bladder organoids as a novel carcinogenesis model. The results suggest that 2-AAF-treated canine normal bladder organoids may have elicited the initiation of carcinogenesis. When 2-AAF-treated bladder organoids were transplanted into immunodeficient mice, tumor formation was observed at 2 weeks after transplantation. However, tumor regression was observed at 4 weeks after transplantation, and the conditions of chemical exposure to organoids are being reexamined.</p>