Medulloblastomas (MB) are devastating brain tumors originating in the cerebellum most commonly in children. There are four distinct subgroups of medulloblastoma: WNT (wingless), SHH (sonic hedgehog), group 3, and group 4. The most malignant tumors possess an aggressive phenotype characterized by c-Myc amplification and deletions to chromosome 17p; they belong to group 3. Prior investigations into the significance of genes on 17p revealed that miR-1253, which is found on locus 17p13.3, is significantly downregulated in medulloblastoma and has important tumor suppressive properties. Amongst its oncogenic targets is B7-H3 (CD276), a highly deregulated oncoprotein that attenuates the immune response to MB tumors. We chose to elucidate the oncogenic properties of B7-H3 in group 3 MB using synthetic inhibitors. After screening 100,000 different compounds for: 1) docking ability, 2) oral bioavailability, 3) potential CNS activity, and 4) number of metabolic side reactions, we selected two N-terminal inhibitors: B7-H3-Ni1 and B7-H3-Ni3. In HDMB03 cells (with c-Myc amplification and i17q), we found an IC50 of 3.7 M for B7-H3-Ni1 and no discernible effect of B7-H3-Ni3. We confirmed CD276 expression inhibition using B7-H3-Ni1 via Western blotting and concurrently noted elevations in cleaved PARP (apoptosis) and reduction in p-Akt (proliferation marker), providing us preliminary insights into the mechanism of inhibition. Notably, a remarkable decline in migration and wound healing and abrogation of colony formation were observed with B7-H3-Ni1. Collectively, our findings substantiate the inhibitory properties of B7-H3-Ni1 in vitro, potentially serving as a therapeutic agent for in vivo group 3 MB tumors.https://digitalcommons.unmc.edu/surp2021/1049/thumbnail.jp
