Primary cilia and Sonic hedgehog signaling in adrenal gland physiology and cancer

The adrenal gland is the major steroidogenic organ in mammals, and the Sonic hedgehog (SHH) pathway is particularly important for its development and homeostatic maintenance. In addition, the SHH pathway upregulation has been observed in adrenocortical carcinoma, a rare but deadly cancer. However, many aspects of how the spatial pattern of SHH secretion and signal reception is established and how this pathway signals during cancer remain less clear. Recent studies show that in the adrenal gland, as in other vertebrate tissues, the primary cilium and ciliary-specific proteins are particularly important for SHH pathway activity. Thus, the presence of primary cilia in the adrenal capsule could be limiting the SHH signaling effects to the adrenocortical progenitors in this region.