ID1 and glioblastoma: The ID proteins have been implicated in many processes involved in oncogenesis (Lasorella et al., 2014), and importantly, ID1 was shown to be upregulated by TGF-β in tumor cells isolated from pathological pleural fluids from patients with ER− and ER+ metastatic breast cancer, and also in patient-derived glioblastomas (Anido et al., 2010; Padua et al., 2008).