RETREG1 and breast cancer: In breast cancers, it has been established that hypoxia induces both UPR and ER-phagy to maintain ER homeostasis, in which HSPA5 binds to Family with sequence similarity 134, member B (FAM134B) to target [180] the damaged areas of the ER into autophagosomes, while the loss of FAM134B decreases the viability of breast cancer cells.