Moreover, cellular stress signaling, such as ER stress-induced activation of the UPR via the ER stress signaling proteins ATF6, IRE1 and PERK and ER stress-mediated activation of NF-κB, occurs largely identical in MCF-7 cells [60, 61] like in non-cancer MECs, thus, allowing to use the MCF-7 cell line specifically for studying the potential of 1,25D3 to modulate ER stress-induced NF-κB-driven inflammatory response in MECs. Here, ATF6 is linked to cancer.