GBM tumors are composed of a heterogeneous combination of cells with distinct phenotypes and proliferative potential, which contributes to the therapeutic resistance of GBM.25,41 Our data suggest that Rab27b may contribute to GBM growth by promoting the proliferation of other subpopulations of intratumoral cells through EREG secretion after IR treatment. Here, RAB27B is linked to glioblastoma.