It was reported elsewhere that five different PDI inhibitors were found to block apoptosis after accumulation of misfolded proteins in a PC12 cell-based model for Huntington disease.23 Furthermore, a downregulation of PDI in mouse embryonic fibroblasts reduced apoptosis upon treatment with different ER stress inducers.30 Therefore, our discovery is probably not restricted to colon carcinoma cell lines but rather displays a general control mechanism of PERK activation. This evidence concerns the gene P4HB and colon carcinoma.