XBP1 and neoplasm: Activation of the unfolded protein response (UPR) is a hallmark event in tumor cells, which serves as a pivotal mechanism for cell survival under the high‐pressure microenvironments caused by rapid proliferation, such as nutrient deficiency, hypoxia, and acid‐base disorders.[8] The inositol‐requiring enzyme 1α (IRE1α)–X‐box–binding protein 1 (XBP1) pathway is the most conserved UPR signaling.