XBP1 and breast cancer: Numerous studies have shown that the UPR can promote the proliferation of tumors such as liver cancer, melanoma, and breast cancer through various signaling cascades such as IRE1/XBP1/JNK, IRE1/XBP1/IL-6/STAT3, and IRE1/TRAF2/NF-κB [23, 24, 28, 29].