Although DDX3 is thought to play a role in Wnt signaling, cells that harbor an APC mutation were less sensitive to RK-33 than cells with wild-type APC. Since CTNNB1 and DDX3X mutations co-occur in Wnt-type medulloblastomas [7–9], we hypothesized that DDX3 dependency may be higher in cells with other genetic aberrations in the Wnt-signaling pathway, like mutations in the gene encoding β-catenin. Here, APC is linked to medulloblastoma.