While the previously studied homozygous Tg(K5-COX-2/675+/+) mouse line on the NMRI outbred background showed up with pronounced epithelial dysplasia in skin epidermis, mammary gland, urinary bladder and pancreas15, 20, the congenic heterozygous Tg(K5-COX/675+/wt) (C) mouse line on the C57BL/6N background used in this study displayed spontaneously less pronounced histological changes in pancreas when comparing 12-months-old transgenic and WT cohorts (SFig. 2). Here, PTGS2 is linked to intraepithelial neoplasia.