It is well known that Endoplasmic Reticulum (ER) stress could induce cell apoptosis or cell death in many tumor categories, including breast cancer [4], neuroectodermal tumor [5], HCC [6], etc. ER stress could activate unfolded protein response (UPR) whose signaling network consists of three stress sensors, namely protein kinase RNA like ER kinase (PERK) or RNA-dependent protein kinase-like kinase, inositol-requiring enzyme 1α (IRE1α), and activating transcription factor 6 (ATF6) [7]. The gene discussed is ATF6; the disease is breast cancer.