AMBRA1 as a novel positive regulator of the SHH pathway in medulloblastoma [RNA-Seq]

AMBRA1 (Autophagy and Beclin 1 Regulator 1) is a versatile scaffold protein involved in disparate processes including autophagy, cell cycle regulation, and tumorigenesis. While AMBRA1 is primarily recognized as a tumor suppressor, its dual function as a tumor promoter has garnered increasing attention. However, the role of AMBRA1 remains largely unexplored in many malignancies, particularly in brain tumors. Leveraging multiomic analysis of the largest human medulloblastoma (MB) cohort, we identify significantly elevated AMBRA1 protein levels in the Sonic Hedgehog subgroup (MBSHH) compared to other MB variants. Notably, AMBRA1 protein abundance, independent of its mRNA expression, correlates with poor prognosis, positioning AMBRA1 as a biomarker for MBSHH. Mechanistically, AMBRA1 enhances SHH signaling by stabilizing GLI1, the pathway's final effector, by inhibiting the βTrCP-mediated degradation of GLI1. Additionally, AMBRA1 protein stability is modulated by the REN E3 ubiquitin ligase, a tumor suppressor gene and antagonist of the SHH pathway. Genetic inhibition of AMBRA1 significantly blocks MBSHH growth in murine and patient-derived pre-clinical models, highlighting its therapeutic potential. Moreover, combining AMBRA1 knock-down with FDA-approved SHH inhibitors amplifies tumor suppression. These findings uncover the AMBRA1/βTrCP/REN axis as a key regulatory mechanism in SHH signaling, providing actionable insights into targeted therapies for MBSHH.