ERN1 and neuroblastoma: ER stress (tunicamycin) activated three branches of the UPR; the PERK, IRE1α, and ATF6 branches, as indicated by the induction of CHOP transcription (Harding et al, 2000), XBP1 splicing (Yoshida et al, 2001; Calfon et al, 2002), and HERP expression (Kokame et al, 2001; Yamamoto et al, 2007), respectively, in the SH-SY5Y neuroblastoma cell line (Fig 2C).