Generation and characterization of feline colorectal adenocarcinoma organoids as a preclinical model.

Feline colorectal adenocarcinoma (FCC) is a locally invasive, highly metastatic malignant gastrointestinal tumor of colon or rectal mucosa in cats. When detected early, surgical resection may provide a promising prognosis. However, no clinical symptoms are observed in the early stages, and distant metastases or peritoneal dissemination are often already present at diagnosis. Therefore, after removal of the primary lesion, follow-up systemic therapy using anticancer drugs is required. However, the drugs currently used for FCC are not sufficiently effective in improving the prognosis, and it is necessary to develop novel and relevant preclinical models that accurately represent the disease. In this study, we developed three-dimensional culture models (organoids) from four FCC cases and examined their histopathological characteristics and drug-sensitivity profiles. FCC organoids were successfully generated and recapitulated the histological structure of the original tumor tissues. Furthermore, the FCC organoids expressed common markers (CK20 and CDX2) of FCC and exhibited tumorigenesis in vivo in mice. Cell viability assay showed that the FCC organoid lines exhibited different sensitivities to carboplatin, doxorubicin, and toceranib. Interestingly, the response of FCC organoids to toceranib varied among the lines and correlated well with the expression level of VEGFR-2, one of the target molecules of toceranib. These results suggested that FCC organoids can be used as preclinical models to advance molecular and therapeutic FCC research.