MOLECULAR CARCINOGENESIS MMP9 Expression in Oesophageal Adenocarcinoma Is Upregulated With Visceral Obesity and Is Associated With Poor Tumour Differentiation Emma H. Allott, 1 Joanne Lysaght, 1 Mary Clare Cathcart, 1 Claire L. Donohoe, 1 Robert Cummins, 2 Sarah A. McGarrigle, 3 Elaine Kay, 2 John V. Reynolds, 1,3 and Graham P. Pidgeon 1 * 1 Department of Surgery, Institute of Molecular Medicine, Trinity College Dublin, Dublin, Ireland 2 Department of Histopathology, Beaumont Hospital, Royal College of Surgeons Ireland, Dublin, Ireland 3 St James’ Hospital, Dublin, Ireland Overweight and obesity is linked to increased incidence and mortality of many cancer types. Of all cancers, oeso- phageal adenocarcinoma (OAC) displays one of the strongest epidemiological links with obesity, accounting for up to 40% of cases, but molecular pathways driving this association remain largely unknown. This study aimed to elucidate mechanisms underpinning the association of obesity and cancer, and to determine if visceral obesity is associated with aggressive tumour biology in OAC. Following co-culture with visceral adipose tissue explants, expression of genes involved in tumour cell invasion and metastasis (matrix metalloproteinase (MMP)2 and MMP9) were upregulated be- tween 10-fold (MMP2) and 5000-fold (MMP9), and expression of tumour suppressor p53 was downregulated 2-fold in OAC cell lines. Western blotting confirmed these results at the protein level, while zymographic analysis detected increased activity of MMPs in OAC cell lines following co-culture with adipose tissue explants. When OAC cell lines were cultured with adipose tissue conditioned media (ACM) from visceral adipose tissue, increased proliferative, mi- gratory and invasive capacity of tumour cells was observed. In OAC patient tumour biopsies, elevated gene expression of MMP9 was associated with visceral obesity, measured by visceral fat area, while increased gene expression of MMP9 and decreased gene expression of tumour suppressor p53 was associated with poor tumour differentiation. These novel data highlight an important role for visceral obesity in upregulation of pro-tumour pathways contributing to aggressive tumour biology, and may ultimately lead to development of stratified treatment for viscerally obese OAC patients. ß 2011 Wiley Periodicals, Inc. Key words: adipose tissue; pro-tumour; invasion; obesity-associated cancer INTRODUCTION The incidence of overweight and obesity has reached pandemic proportions in modern society, affecting two-thirds of the US and over half of the European population [1,2]. Excess adiposity has been estimated to account for up to 14% of all can- cer deaths in men and 20% in women in the US [3]. While the epidemiological link is now well de- scribed for an ever-expanding list of cancers [4,5], the molecular mechanisms linking obesity and cancer remain poorly defined. It is now known that excess visceral (abdominal) adiposity is more strongly associated with metabolic deregulation and disease states than overall obesity [6,7]. The strong association of visceral obesity with Barrett’s oesophagus [8,9] and oesophageal adenocarcinoma (OAC) [10] suggests that altered metabolic activity of visceral adipose tissue in obesity may play a fun- damental role in the development of this cancer. Oesophageal cancer is the eighth most common cancer worldwide but the sixth most common cause of cancer-related mortality, indicating the aggressive nature of this disease [11]. Incidence of this highly lethal cancer in Europe and the U.S. has risen rapidly in the last 15 yr, mirroring the exponential rise in obesity [12,13]. Oesophageal cancer is an aggressive disease associated with a poor 5-yr survival of only 15% [12] due in part to early lymphatic and haematogenous dissemination [14] implying that pathways involved in tumour invasion and metastasis are of great significance. Proteolytic cleavage of the extracellular matrix (ECM), necessary for invasion and metastasis to oc- cur, is carried out by proteases such as the matrix metalloproteinases (MMPs). Of particular interest Abbreviations: OAC, oesophageal adenocarcinoma; ECM, extra- cellular matrix; WC, waist circumference; VFA, visceral fat area; ACM, adipose tissue conditioned media. The authors declare that they have no competing interests. *Correspondence to: Department of Surgery, Institute of Molec- ular Medicine, Trinity Centre for Health Sciences, St James’ Hospi- tal, Trinity College Dublin, Dublin 8, Ireland. Received 8 June 2011; Revised 18 October 2011; Accepted 19 October 2011 DOI 10.1002/mc.21840 Published online in Wiley Online Library (wileyonlinelibrary.com). ß 2011 WILEY PERIODICALS, INC.