Role of Natural Killer Cells in Sonic Hedgehog driven Medulloblastoma

Medulloblastoma (MB) is the most common paediatric neoplasm of the CNS. Standard therapy is mainly curative; however, the severe side effects make immunotherapy an attractive therapeutic option. Natural Killer (NK) cells are innate lymphoid cells that can be used for adoptive cell therapy. Herein, we studied the role of NK cells in MB growth control, focusing on Sonic Hedgehog (SHH) subgroup, using the MB cell line DAOY. The contribution of SHH pathway on NK cell recruitment to MB was analysed performing an orthotopic xenograft of DAOY in nude mice treated with a pharmacological inhibitor of the SHH pathway. FACS analysis revealed higher percentage of NK cells in cerebella of treated mice compared to control group. Based on this in vivo evidence, we characterized the mechanism underlying NK cell recruitment. Pharmacological inhibition of the SHH pathway in DAOY raised the expression and secretion of chemokines involved in NK cell migration. Chemotaxis assay confirmed that these secreted molecules were functional. Successively, we assessed the ability of NK cells to recognize SHH-MB. By FACS analysis we determined the tumor line expression of ligands for the NKG2D and DNAM1 activating receptor. In particular, ULBP3 and ULBP2 were expressed at high levels. Moreover, we found that NK cells co-culture with DAOY induced degranulation that was reduced in the presence of anti-NKG2D and anti-DNAM1 blocking antibodies, suggesting an involvement of these receptors in triggering degranulation. Besides, DAOY increased the production of IFNγ in NK cells pre-activated of with suboptimal doses of IL12 and IL15. Our data provide evidence for a role of NK cells in the control of SHH-MB growth.