AMBRA1 enhances Sonic Hedgehog signaling during cerebellar development and in medulloblastoma

AMBRA1 (autophagy and beclin 1 regulator 1) is primarily recognized as a tumor suppressor. However, its role as a tumor promoter has garnered increasing attention. Here, leveraging clinical data of an international multi-omic medulloblastoma (MB) cohort, we identified that elevated AMBRA1 protein levels, independently of its mRNA expression, correlate with poor prognosis in the Sonic Hedgehog subgroup (MB_SHH). Mechanistically, AMBRA1 enhances SHH signaling by stabilizing GLI1, the pathway's final effector, via inhibition of its βTrCP-mediated degradation. Additionally, AMBRA1 protein stability is modulated by the REN E3 ubiquitin ligase, a tumor suppressor gene lost in MB_SHH. Inhibition of AMBRA1 blocks MB_SHH growth in murine and patient-derived preclinical models. Moreover, combining AMBRA1 knockdown with FDA-approved SHH inhibitors enhances antitumor efficacy. These findings identify the AMBRA1/βTrCP/REN axis as a key regulatory mechanism in SHH signaling and discover an unrecognized function of AMBRA1 in MB_SHH, providing actionable insights into brain tumor biology.