P4HB and colorectal carcinoma: BIP regulates the expression of inositol-requiring enzyme 1a (IRE1a), C/EBP homologous protein (CHOP), and protein disulfide isomerase (PDI) during ER stress; and consistent with increased BIP, the levels of CHOP, PDI, and IRE1a were also elevated (Fig 5A and 5B), providing further support for the hypothesis that NaB induced ER stress in CRC cells.