TRIM33 and glioblastoma: In both cases, TRIM33 represses proliferation: murine cortical neural stem cells undergo excessive proliferation and fail to differentiate properly when TRIM33 is knocked out alongside SMAD4, indicative of potential redundancy in the pathway; whereas in human GBM, β-Catenin phosphorylation by PKCδ triggers its ubiquitination by TRIM33 and subsequent degradation, leading to suppression of tumor cell proliferation (Falk et al., 2014; Xue et al., 2015).