Activated status of Hedgehog pathway in oral squamous cell carcinoma (OSCC): the door is still open

The Hedgehog (Hh) signaling pathway is essential for regulation of cell differentiation and organ formation in a concentration-dependent manner during embryonic development. Also, this pathway is important to the maintenance of adult stem cells. Studies have shown that three members of this family are present in mammals: Sonic hedgehog (SHH), Desert hedgehog (DHH) and Indian hedgehog (IHH), all of which encode secreted proteins (1).