The fundamental concept of cancer stem cell and the progress in cancer stem cell research

Stem cell is defined as the cell having the ability of self-renew and differentiation. Due to the development of flow cytometric analysis and immunodeficient mouse model, stem cell research had dramatically progressed. Based on the knowledge of normal stem cell, concept of cancer stem cell, which have self-renewal ability and tumorigenic potential in immunodeficient mouse, have been established. Cancer stem cell population in various cancers has been identified using cell surface markers, such as CD44, and therapeutic strategies have been developing. Moreover, as accumulating the knowledge of cancer stem cell, it has revealed that cancer stem cell has high plasticity. We introduce here the evolving cancer stem cell concept.