XBP1 and breast cancer: This includes promoting the proliferation of breast cancer cells via its IRE1–XBP1 pathway [26]; mediating tumor cell apoptosis through the IRE1/TRAF2/ASK1/JNK pathway [47, 48], controlling IRE1 signaling via GPCRs and subsequently activating EMT to foster tumor metastasis [74]; or promoting tumor invasion through the IRE1–XBP1 pathway, reflecting the multifaceted role of IRE1 in tumor development.