ERN1 and glioblastoma: What few inhibitors of IRE1 exist target its endonuclease domain [64–67] rather than the kinase activity, since the conformational status of the protein rather than its kinase function is key for the endonuclease activity [68] (however, FDA-approved sunitinib, an inhibitor of several receptor tyrosine kinases, does appear to affect IRE1 [69], and has been used in numerous clinical trials for GBM patients).