ERN1 and glioblastoma: Abnormal activities of all UPR effectors (PERK, IRE1α, and ATF6) have been shown to be implicated in the survival, metastasis, angiogenesis, and chemoresistance of glioblastoma [42], pancreatic [43,44], lung [45], colon/colorectal [46,47], and urological [48] cancers at different stages of the disease.