Autophagy inhibition enhances Natural Killer cell- based therapy in high-risk Medulloblastoma

Medulloblastoma (MB) is the most common pediatric brain tumor with Group3 (G3) subtype characterized by poor prognosis and therapy relapse. Autophagy is a self-degradative process increased in G3 MB stem cells (MBSCs) to contribute stemness and survival (Nazio et al., 2021). A promising therapeutic value in the treatment of high-risk MB is represented by Natural Killer cells (NKs)-based immunotherapy but it requires complementary approaches that break im- mune tolerance. To date, the role of autophagy-mediated mechanisms in regulating tumour heterogeneity and immune cells infiltration capability in the context of brain TME remains un- known as well as the role of autophagy in NK/CAR-NK mediated therapy is completely unex- plored. Herein, we are investigating the role of autophagy inhibition as a druggable mechanism to increase NK recognition and killing against MB G3. By flow cytometry analysis, we found low levels of NK-related activating ligands (ULBPs, CD155, CD112, MICA/B) in G3 cell lines and MBSCs derived by MB G3 patients compared to SHH subgroup. Intriguingly, genetic and pharmacologic inhibition of autophagy is able to increase NK-related ligand expression on cell surface of MB G3 cells. Additionally, by means of 2D and 3D models of MB G3 cells, we found that autophagy inhibition increases NK degranulation and MB G3 sensitiveness to NK-mediated cytotoxicity. Im- munotherapeutic strategies aimed at restoring and increasing the cytotoxic activity of NK cells in solid tumors, including the adoptive transfer of NK cells, are currently employed in preclinical and clinical studies. New strategies are necessary to make NK cells more resistant to the meta- bolically restrictive TME as well as to immunosuppressive molecules generated by the tumor. The completion of our project would be helpful to design a novel therapeutic approach for chil- dren with high-risk MB, aiming to a higher clinical response rate coupled with less toxicity as compared to conventional therapies.