SOX9 is a transcription factor that controls cell fate decision during the development and homeostasis of a broad range of tissues, and is expressed in a wide range of cancers. SOX9 deletion prevents tumorigenesis in prostatic and pancreatic mouse cancer models. Overexpression of SOX9 inhibits apoptosis and promotes proliferation, invasion, and migration, whereas downregulation of SOX9 impaired invasion and growth in vitro and in vivo. SOX9 has been well recognized for its capacity in stemness maintenance of neural stem cell (NSC). Gain- and loss-of-function studies indicated that SOX9 was essential for multipotent NSC formation.