Rectal epithelial cell mitosis and expression of macrophage migration inhibitory factor are increased 3 years after Roux-en-Y gastric bypass (RYGB) for morbid obesity: implications for long-term neoplastic risk following RYGB Prashant Kant, 1 Anita Sainsbury, 1 Karen R Reed, 2 Stephen G Pollard, 3 Nigel Scott, 4 Alan R Clarke, 2 P Louise Coletta, 1 Mark A Hull 1 ABSTRACT Background Rectal epithelial cell mitosis and crypt size, as well as expression of proinflammatory genes including macrophage migration inhibitory factor (MIF), are increased 6 months after Roux-en-Y gastric bypass (RYGB) in morbidly obese patients. Tests were carried out to determine whether these putative colorectal cancer risk biomarkers remained elevated long term after RYGB, and the mechanistic basis, as well as the functional consequences, of Mif upregulation in intestinal epithelial cells was investigated. Methods Rectal mucosa and blood were obtained a median of 3 years after RYGB from the original cohort of patients with RYGB (n¼19) for crypt microdissection, real- time PCR, immunohistochemistry for MIF and immunoassay of proinflammatory markers. Immunohistochemistry for Mif and bromodeoxyuridine labelling were performed on AhCre + mouse and Apc Min/+ mouse (with and without functional Mif alleles) intestine, respectively. Results Rectal epithelial cell mitosis and crypt size remained elevated 3 years after RYGB compared with preoperative values (1.7- and 1.5-fold, respectively; p<0.05). There was a 40-fold (95% CI 13 to 125) increase in mucosal MIF transcript levels at 3 years associated with increased epithelial cell MIF protein levels. Conditional Apc loss in AhCre + mice led to increased epithelial cell Mif content. Mif deficiency in Apc Min/+ mice was associated with a combined defect in intestinal epithelial cell proliferation and migration, which was reflected by the longitudinal clinical data. Conclusions Mucosal abnormalities persist 3 years after RYGB and include elevation of the protumorigenic cytokine MIF, which is upregulated following Apc loss and which contributes to intestinal epithelial cell homeostasis. These observations should prompt clinical studies of colorectal neoplastic risk after RYGB. INTRODUCTION Considerable epidemiological evidence links obesity and increased risk of colorectal cancer (CRC). 1 The RR of CRC in overweight (defined as a body mass index (BMI) of 25e29.9 kg/m 2 ) and obese (BMI >30 kg/m 2 ) individuals is w1.5e2.5 compared with normal weight (BMI 18.5e25 kg/m 2 ) controls, 1 with a similar RR for colorectal adenoma. 2e5 Recent forecasts predict a continued rise in the prevalence of obesity in the UK to >30% < Additional figures are published online only. To view these files please visit the journal online (http://gut.bmj. com). 1 Leeds Institute of Molecular Medicine, Wellcome Trust Brenner Building, St James’s University Hospital, Leeds, UK 2 Cardiff School of Biosciences, University of Cardiff, Cardiff, Wales, UK 3 Department of Obesity Surgery, St James’s University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK 4 Department of Histopathology, St James’s University Hospital, Leeds Teaching Hospitals NHS Trust, Leeds, UK Correspondence to Prof Mark A Hull, Leeds Institute of Molecular Medicine, Wellcome Trust Brenner Building, St James’s University Hospital, Leeds LS9 7TF, UK; m.a.hull@leeds.ac.uk Revised 22 December 2010 Accepted 27 December 2010 Published Online First 8 February 2011 Significance of this study What is already known about the subject? < Roux-en-Y gastric bypass (RYGB) is increasingly performed in morbidly obese patients. < Six months after RYGB, there is increased rectal mucosal crypt size and epithelial cell mitosis, as well as increased mucosal proinflammatory gene expression (including cyclooxygenase-2 (COX-2) and macrophage migration inhibitory factor (MIF)). < It is not known whether these changes represent a short-term postoperative phenom- enon or persist in the long term. < Rectal crypt parameters such as mitosis frequency may be biomarkers of future colo- rectal cancer risk, and several proinflammatory factors such as cyclooxygenase-2 (COX-2) and MIF have protumorigenic properties. What are the new findings? < Rectal crypt parameters remain persistently abnormal at least 3 years after RYGB. < Rectal epithelial cell expression of MIF is elevated long term. < Mif is upregulated following loss of the Adeno- matous polyposis coli (Apc) tumour suppressor gene in mouse intestinal epithelial cells. < Mif contributes to mouse intestinal epithelial cell homeostasis, and the effect of Mif deletion in the Apc Min/+ mouse is compatible with our clinical association of increased mitosis frequency and MIF upregulation. How might it impact on clinical practice in the foreseeable future? < Persistent rectal mucosal changes in putative biomarkers of future CRC risk at least 3 years after RYGB should prompt clinical evaluation of colorectal adenoma incidence post-RYGB. < MIF is a potential target for chemoprevention of CRC using small molecule inhibitors. Gut 2011;60:893e901. doi:10.1136/gut.2010.230755 893 Stomach group.bmj.com on November 12, 2013 - Published by gut.bmj.com Downloaded from