Sox9 is a transcription factor with an HMG-box DNA binding domain that has homology to the HMG domain of the mammalian testis-determining factor, SRY . Sox9 regulates several important processes during embryonic development including chondrogenesis, during which it contributes to skeletal formation and digit specification . Sox9 also coordinates with steroidogenic factor-1 to direct Sertoli cell-specific expression of anti-Mullerian hormone during embryogenesis, thereby contributing to male sex determination . In addition, Sox9 is reportedly involved in the maintenance of adult stem cell populations, including multipotent neural stem cells , hair follicle stem cells , and mammary stem cells . Recent interest has focused on the role of Sox9 in tumor biology. For example, research studies have shown that Sox9 expression in lung adenocarcinoma induces a mesenchymal phenotype in tumor cells . Other research studies have shown that YAP1 induced upregulation of Sox9 confers cancer stem cell like properties on esophageal cancer cells . Moreover, Sox9 expression has been linked with several other tumor types including ovarian, prostate, and pancreatic malignancies .