Although there might be another pathway affecting CRT expression of myeloma cells, these results suggest that the IRE1α-XBP1 pathway may play a more important role in the ICD of myeloma cells than the PERK-eIF2α pathway, indicating that PIs may induce CRT expression in myeloma cells by the different UPR pathway from other types of cancer cells (Figure 7B). This evidence concerns the gene ERN1 and plasma cell myeloma.