Tumor evolution during metastasis

Cancer is a genetic disorder triggered by germline and somatic DNA mutations. Strong somatic mutations can induce cellular growth continuously, which increases the probability of developing secondary somatic mutations. Loss of function in genes related to DNA damage repair and homologous recombination may increase genetic instability. Genetic instability is one of the characteristic signs of cancer, which causes genetic aberrations in the tumor cell population and results in clonal divergence. In particular, somatic mutations in subclonal populations may lead to intratumoral heterogeneity and tumor evolution. Subclonal tumor cells may show phenotypes, such as treatment resistance, metastasis, and relapse, which result in poor clinical outcomes. Comprehensive molecular and genomic analyses of cancer have enabled us to understand cancer biology, especially in the area of tumorigenesis, which provides the foundation for the development of targeted therapeutics, such as tyrosine kinase inhibitors. Recently, we analyzed the cancer genome at the single-cell level using microfluidic devices and nucleic acid amplification methods. With advancements in single-cell genomic technology, we can study tumor heterogeneity as well as the tumor microenvironment.