ERN1 and glioblastoma: Glutamine deprivation is linked to the expression of the Endoplasmic Reticulum to Nucleus Signalling 1/Inositol Requiring Enzyme 1 (ERN1/IRE1) in the context of glioblastoma [56], a gene coding for a protein that acts as a detector for unfolded proteins in the endoplasmic reticulum.