ID1 and glioblastoma: 1) In Glioblastoma, PGE2-mediated induction of ID1 is required for optimal tumor cell self-renewal and radiation resistance[16]. 2) ID1 overexpression in GBM cells increased radioresistance[17]. 3) Id1 and Id3 co-expression seems associated with a poor clinical outcome in patients with locally advanced NSCLC treated with definitive chemoradiotherapy[18]. 4) In GBM, a significant correlation (P < 0.001) was found between radiotherapy efficacy and ID1 expression levels with respect to overall survival and knockdown of ID1 increased radiosensitivity in vitro[19]