Patient-derived organoids of bladder cancer recapitulate antigen expression profiles and serve as a personal evaluation model for CAR-T cells in vitro

Objectives. Recent advances in patient-derived cancer organoids have opened a new avenue for personalised medicine. We aimed to establish an in vitro technological platform to evaluate chimeric antigen receptor (CAR)-T cell-mediated cytotoxicity against bladder cancer. Methods. Patient-derived bladder cancer organoids (BCOs) were derived using classic medium containing R-spondin 1 and noggin. The features of BCOs were characterised via H&E, whole-exome sequencing and immunofluorescence of specific markers. Surface antigen expression profiles of the recently identified CAR-recognisable targets were determined with a panel of antibodies via immunohistochemistry. A co-cultivation system consisting of BCOs and engineered T cells targeting a specific antigen was utilised to test its efficacy to model immunotherapy by cytotoxic assays and ELISA. Results. Bladder cancer organoid lines of basal and luminal subtypes were established. The histopathological morphology, genomic alteration, and specific marker expression profiles showed that the BCO lines retained the characteristics of the original tumors. Among all tested CAR-recognisable antigens in other solid tumors, MUC1 was simultaneously expressed in organoids and parental tumor tissues. Given the surface antigen profiles, second-generation CAR-T cells targeting MUC1 were prepared for modelling in vitro immunotherapy responses in BCOs. Specific immune cytotoxicity occurred only in the MUC1(+) organoids but not in the MUC1(-) organoids or control CAR-T cells. Conclusion. Patient-derived BCOs recapitulate the heterogeneity and key features of parental cancer tissues, and these BCOs could be useful for preclinical testing of CAR-T cells in vitro.