A. P. Stark1, W. Sheppard1, X. Jung1, K. Hertzer1, A. Moro1, H. Chang1, M. Xu1, O. J. Hines1, G. Eibl1 1University Of California – Los Angeles,Department Of Surgery,Los Angeles, CA, USA
Introduction: Epithelial-mesenchymal transition (EMT) is increasingly considered to be a necessary first step in the development of invasive disease. Accordingly, loss of the epithelial marker E-cadherin is associated with decreased survival in human pancreatic ductal adenocarcinoma (PDAC). Alarmingly, EMT has been demonstrated prior to tumor formation in a mouse model of PDAC—and is accelerated by inflammation. Obesity is a known pro-inflammatory state and an established risk factor for PDAC. We have previously demonstrated accelerated pancreatic tumorigenesis as a result of a high fat, high calorie diet; however, the direct effect of diet-induced obesity on EMT and E-cadherin expression is unknown.
Methods: Conditional KrasG12D (KC) mice were fed a control diet (CD; 3726 kcal/kg, 12% fat) or a high fat, high calorie diet (HFCD; 4536 kcal/kg, 40% fat). Mice were weighed weekly. To demonstrate the spectrum of pancreatic epithelial neoplasia (PanIN 1-3), cohorts were sacrificed at 3 and 9 months of age. Pancreata were preserved in formalin and embedded in paraffin. Immunohistochemistry (IHC) was performed using antibody against E-cadherin. Immunoreactivity was characterized by staining intensity, location (cell membrane, cytoplasm, nucleus), and proportion of positive cells.
Results: For the 3-month cohort, implementation of the diet led to significantly increased weight gain among HFCD mice (n=7) vs. CD mice (n=7), 15.8gm vs. 5.6gm (p<.001). In the 9-month cohort, HFCD mice (n=7) also had higher average weight gain compared to CD mice (n=5), 19.8gm vs. 12.9gm (p = .007). Compared to CD-fed animals, mice fed the HFCD for 3 and 9 months showed more robust inflammatory features in the pancreas as demonstrated by a loss of acinar tissue and formation of desmoplasia. Mice fed the HFCD for 9 months had more severe pathology than mice fed the HFCD for 3 months. No invasive cancer was detected. Overall, E-cadherin expression was ubiquitous, strong, and membranous regardless of diet in both 3- and 9- month cohorts. Staining intensity was intermittently decreased in higher-grade PanIN lesions, but no differences between groups were noticed (See Figure 1).
Conclusions: Despite evidence of more advanced disease, KC mice fed a HFCD did not show evidence of grossly altered E-cadherin expression. If early EMT is part of the mechanism underlying diet-induced acceleration of pancreatic tumorigenesis, it may occur despite E-cadherin expression.
