Due to the rapid proliferation of cancer cells and their easy exposure to a low-nutrient, low-vascularization and hypoxic environment, endoplasmic reticulum stress-related proteins, such as GRP78, activating transcription factor 6 (activating transcription factor 6, ATF6), inositol-requiring enzyme 1 (IRE1), protein kinase RNA-like endoplasmic reticulum kinase (protein kinase RNA-like ER kinase, PERK) are overexpressed in many types of tumors. Here, HSPA5 is linked to cancer.