In response to ER stress, cancer cells initiate an evolutionarily conserved signaling process called the unfolded protein response, which is coordinated by three endoplasmic reticulum transmembrane binding sensors: inositol requires kinase enzyme 1 α (IRE1 α), activating transcription factor 6 (ATF6) and protein kinase R-like endoplasmic reticulum kinase (PERK) [35]. Here, ATF6 is linked to cancer.