ERN1 and cancer: 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).