UPR modulation in breast cancer stem-like cells has been less explored, yet it has been shown that BIP is enriched in these subpopulations isolated from multiple breast cancer cell lines [63] and activation of the IRE1/XBP1 branch was related to the maintenance breast cance stem cells, their tumorigenicity and resistance to chemotherapy [64,65]. Here, XBP1 is linked to breast carcinoma.