In Vitro and In Vivo Models for Metastatic Intestinal Tumors Using Genotype-Defined Organoids.

It has been established that the accumulation of driver gene mutations causes malignant progression of colorectal cancer (CRC) through positive selection and clonal expansion, similar to Darwin's evolution. Following this multistep tumorigenesis concept, we previously showed the specific mutation patterns for each process of malignant progression, including submucosal invasion, epithelial mesenchymal transition (EMT), intravasation, and metastasis, using genetically engineered mouse and organoid models. However, we also found that certain populations of cancer-derived organoid cells lost malignant characteristics of metastatic ability, although driver mutations were not impaired, and such subpopulations were eliminated from the tumor tissues by negative selection. These organoid model studies have contributed to our understanding of the cancer evolution mechanism. We herein report the in vitro and in vivo experimental protocols to investigate the survival, growth, and metastatic ability of intestinal tumor-derived organoids. The model system will be useful for basic research as well as the development of clinical strategies.