XBP1 and pachyonychia congenita: Chip-Seq data of all pancreatic samples available in ENCODE, as well as PANC-1 pancreatic cancer cells (see the “Methods” section), allowed us to find that, in comparison to normal pancreas, the H3K27Ac mark present in the XBP1 promoter is completely lost in PANC-1 cells and is reduced in a sample of a Pancreatic Intraepithelial Neoplasia 1B, a PC precursor (Fig. 2).