AGR2 and cancer: Based on a literature search, AGR2 has been demonstrated to be upregulated upon ER stress, and ER stress-related molecules, such as protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1 (IRE1) and activating transcription factor 6 (ATF6), are dysregulated in many cancer types [16].