Cilia can promote or suppress tumour growth, depending on the nature of the tumour-initiating event, as reported by two studies in this week’s Nature Medicine.

Primary cilia are specialised appendages that extend from the surface of many cell types and have been implicated in cell signalling. They are crucial during foetal development for signalling pathways mediated by a protein known as Hedgehog. As Hedgehog has also been implicated in cancers, Jeremy Reiter, Arturo Alvarez-Buylla and their respective colleagues explored the possible contribution of primary cilia to tumour formation.

Studying two types of cancer, basal cell carcinoma and medulloblastoma, the two groups independently found that cilia could favour or inhibit tumour formation in mice. If the tumour was triggered by the expression of Smoothened, a well-known activator of Hedgehog, removal of cilia blocked tumour formation. But if the tumour was initiated by the expression of Gli2, a molecule downstream of Hedgehog, then removal of cilia accelerated tumour growth.

These data disclose an unexpected dual role of cilia on cancer. Further analysis of their role may lead to better understanding of tumour development and treatment.

DOI: 10.1038/nm.2011
DOI: 10.1038/nm.2020