Further, mass spectrometric analysis of the protein-binding network in glioblastoma cells identified USP15 as an interacting partner that is homologous to the E6-AP carboxyl terminus (HECT) domain-containing E3 ubiquitin protein ligase 1 HECTD1, whose mouse homolog has been associated with an inhibitory effect on the Wnt pathway. Here, USP15 is linked to glioblastoma.