Abstract
BACKGROUND: Medulloblastoma (MB) is a lethal pediatric malignancy of the cerebellum. Among MB’s molecular subgroups, Sonic Hedgehog (SHH) is the most abundant and it is characterized by alterations of key components of the SHH development pathway. However, the molecular mechanisms driving SHH-MB require to further be unveiled to design more effective therapies. Recently, we identified formins, well-known players of cytoskeletal dynamics, as regulators of SHH signaling able to affect SHH-MB growth. METHODS: Luciferase functional assays, western-blot and RT-qPCR have been performed to analyze the effect of formins on GLI1 (the final effector of SHH signaling) transcriptional activity and expression. Proliferation assays and Brillouin microscopy have been carried out on primary murine SHH-MB cells to test the effect of formins on SHH-MB growth and stiffness. RESULTS: We demonstrated that formins have a dual role in the regulation of SHH signaling, either positive or negative. The modulation of formins expression in SHH-dependent cell models affect GLI1 transcriptional activity and expression. Moreover, formins show opposite protein expression levels during the development of murine cerebellum, and their modulation impair the proliferation of granule cell progenitors (GCPs), the cells of origin of MB. Interestingly, formins protein levels are highly altered in SHH-MB samples. Notably, the overexpression or the genetic silencing of formins in SHH-MB primary cells from Math1-Cre/Ptc1(fl/fl) mice significantly impact on the cell proliferation as consequence of modulated GLI1 expression levels and the stiffness of primary SHH-MB cells, thus suggesting that formins could affect tumor cell motility and invasiveness. CONCLUSIONS: Our findings identify formins as regulators of SHH signaling and illuminate on the role of cytoskeleton in SHH-MB for the design of innovative interventions.