The cancer tissue shows extensive intratumor genetic heterogeneity. However, studies to identify genes involved in genetic heterogeneity during cancer progression have not been performed due to the lack of animal models. In this research, we aim to identify candidate cancer genes (CCGs) promoting cancer metastasis using the SB transposon system, which can generate genetically heterogenous cell population. To validate CCGs identified from SB screens, we plan to use the CRISPR-Cas9 technique to perform high-throughput validation in mice. Our results will give a new insight into the mechanisms to explain how genetically heterogenous cell population promotes malignant progression. Also our efforts to identify novel driver genes involved in cancer progression will help developing new drugs that target more advanced cancer.