ERN1 and breast cancer: Western blot analyses demonstrated that MCF7 breast cancer cells that transiently overexpressed CCDC170 expressed higher levels of IRE1α (P = 0.018), cleaved poly [ADP-ribose] polymerase (PARP, an apoptotic regulatory protein; P = 0.001) and Caspase-7 (P = 0.001) and lower levels of Bcl-2 (an apoptosis-inhibiting protein; P = 0.013) than control cells under endoplasmic reticulum stress (Figure 5B, 5C).