N-methylnitrosourea aggravates gastrointestinal polyposis in Lkb1+/- mice

Abstract

Peutz-Jeghers patients develop hamartomatous polyps and carcinomas of the gastrointestinal tract. Cyclooxygenase-2 accelerates polyp growth in Lkb1+/- mice modelling Peutz-Jeghers polyposis. In this study, we aimed to evaluate the effect of the mutagenic carcinogen N-methylnitrosourea (MNU) on gastrointestinal tumourigenesis in Lkb1+/- mice and to investigate the role of cyclooxygenase-2 on the tumourigenesis. We treated 40 Lkb1+/- and 51 wild-type mice with MNU, 10 mice from both groups received the cyclooxygenase-2 inhibitor celecoxib. Carcinogen-treated Lkb1+/- mice displayed worse survival (60%) than treated wildtype (100%, P = 0.028) or untreated Lkb1+/- mice (92%, P = 0.045). Also, the gastrointestinal tumour burden was almost 10-fold higher in carcinogen-treated (2181 mm3) than in untreated (237 mm3, P = 0.00045) Lkb1+/- mice. Celecoxib was much less efficient in reducing tumourigenesis in MNU-treated mice (by 23%; 1686 mm3) than in untreated mice (76%; 58 mm3). Surprisingly, the increase in tumour burden in MNU-treated mice was not accompanied by consistent histological changes, with only a single focus of epithelial dysplasia noted. This study suggests that MNU promotes Peutz-Jeghers polyposis independently from the acceleration by cyclooxygenase-2. © The Author 2013. Published by Oxford University Press. All rights reserved.