While the IRE1α pathway is critical for differentiation, it is also co-opted by malignant plasma cells in multiple myeloma, where its inhibition suppresses the secretion of not only immunoglobulin light chains but also key growth factors and cytokines, such as vascular endothelial growth factor (VEGF), IL-1α, IL-6, and IL-8 (72). This evidence concerns the gene VEGFA and plasma cell myeloma.