Sonic hedgehog pathway for the treatment of inflammatory diseases: implications and opportunities for future research

The Sonic hedgehog (Shh) signaling pathway is an essential pathway in the human body that plays an important role in embryogenesis and tissue homeostasis. Aberrant activation of this pathway has been linked to the development of different diseases, ranging from cancer to immune dysregulation and infections.Uncontrolled activation of the pathway through sporadic mutations or other mechanisms is associated with cancer development and progression in various malignancies, such as basal cell carcinoma, medulloblastoma, pancreatic cancer, breast cancer and small-cell lung carcinoma. Targeted inhibition of the pathway components has therefore emerged as an attractive and validated therapeutic strategy for the treatment of a wide range of cancers. Currently, two main components of the pathway, the smoothened receptor and the glioma-associated oncogene homolog transcriptional factors, have been investigated for the development of targeted drugs, leading to the marketing authorization of three smoothened receptor inhibitors for the treatment of basal cell carcinoma and acute myeloid leukemia.The Shh pathway also seems to be involved in regulating the immune response, possibly playing a role in immune system evasions by tumors, development of autoimmune diseases, such as rheumatoid arthritis and Crohn's disease, airway inflammation, and diseases related to aberrant activation of T-helper 2 cellular response, such as allergy, atopic dermatitis, and asthma.Finally, the Shh pathway is involved in pathogen-mediated infection, including influenza-A and, more recently, SARS-CoV-2 viruses. Therefore, agents that inhibit the Shh signaling pathway might be used to treat pathogenic infections, shifting the therapeutic approach from strain-specific treatments to host-based strategies that target highly conserved host targets.