XBP1 and cancer: Indeed, IRE1α endonuclease inhibitors such as toyocamycin, STF-083010 4μ8C, MKC-3946, and B-I09, which prevent XBP1 splicing, have been successfully exploited in MM [41,42], and other cancers [43] and could be considered as a therapeutic strategy to diminish cancer cell ability to live in harsh microenvironment conditions, such as hypoxia and nutrient deprivation, leading to increased drug sensitivity and reduced angiogenesis.