Immunohistochemical staining was performed by simply incubating tissue microarrays overnight with antibodies against VEGFR2 (55B11; Cell Signaling Technology, Danvers, MA, USA), EpCAM (323A3, in-house produced hybridoma), c-MET (SC10; Santa Cruz Biotechnology, Santa Cruz, CA, USA), CEA (A0155; Dako, Glustrup, Denmark), EGFR (E30; Dako), integrin v6(6

Immunohistochemical staining was performed by simply incubating tissue microarrays overnight with antibodies against VEGFR2 (55B11; Cell Signaling Technology, Danvers, MA, USA), EpCAM (323A3, in-house produced hybridoma), c-MET (SC10; Santa Cruz Biotechnology, Santa Cruz, CA, USA), CEA (A0155; Dako, Glustrup, Denmark), EGFR (E30; Dako), integrin v6(6. 2A; Biogen Idec MA Inc., Cambridge, MA, USA), HER2 (A0485; Dako), and uPAR (ATN-615, kindly provided by Prof A. P. The results of this study show that integrin v6, CEA, EGFR, and uPAR are suitable targets for tumor-specific imaging of pancreatic adenocarcinoma. Key words: Pancreatic adenocarcinoma, Periampullary adenocarcinoma, Molecular imaging, Image-guided surgery, Immunohistochemistry, Integrin v6, Carcinoembryonic antigen (CEA), Epithelial growth factor receptor (EGFR), Urokinase plasminogen activator receptor (uPAR) == Introduction == Pancreatic adenocarcinoma currently ranks the fourth leading cause of cancer-related death in the Western world, with a 5-year survival rate of less than 5 % PF-04979064 [1]. Radical surgical tumor resection is imperative to curative treatment of these patients as positive resection margins (defined as tumor cells present at the surface of the resection margins of the surgical specimen) are associated with a dramatic decrease in median overall survival [14]. Unfortunately, positive resection margins are common after pancreatic surgery and reported rates vary between 24 % and 76 % [57]. Adjuvant therapy cannot retaliate the poor survival outcome associated with residual disease [8]. The disappointing irradical resection rates after pancreatic surgery are due to our current inability to detect the true delineation of the tumor extent during surgery, which is further complicated by the intricate anatomy of the pancreas and the commonly present peritumoral inflammatory zone in pancreatic cancer. Conventional anatomic imaging modalities used for preoperative diagnosis, staging, and surgical planning include multiphase intravenous contrast-directed thin slice computed tomography, magnetic resonance imaging, endoscopic ultrasonography, and endoscopic retrograde cholangiopancreatography [9, 10]. However , the translation of these preoperative imaging techniques to the surgical field remains challenging and in the theater, the surgical oncologist solely has to rely on vision and manual palpation to discriminate between malignant and healthy pancreatic tissue, assisted by ultrasonography and pathologic evaluation of frozen tissue sections [10]. Intraoperative tumor-specific imaging offers the opportunity to significantly improve current practice by increasing the capability to obtain negative resection margins and visualize residual disease during pancreatic surgery. This novel imaging approach uses labeled receptor ligands, nanoparticles, antibodies, or antibody fragments targeting cancer-specific antigens on the tumor surface detected by positron emission tomography, single-photon emission computed tomography, ultrasonography, magnetic resonance, and/or near-infrared fluorescence imaging modalities [1113]. The feasibility of these imaging techniques has already successfully been proven in glioma and ovarian cancer surgery using respectively the fluorescent agents 5-aminolevulinic acid and folate conjugated to fluorescein isothiocyanate [11, 14]. Furthermore, the potential of image-guided surgery in pancreatic adenocarcinoma has been demonstrated by numerous preclinical studies using cancer-specific contrast agents targeting integrin v6, carcinoembryonic antigen (CEA), epithelial growth factor receptor (EGFR), human epidermal growth factor receptor (HER2), urokinase plasminogen activator receptor (uPAR), or vascular endothelial growth factor receptor 2 (VEGFR2) among others (Table1). Nevertheless, the orthotopic mouse models used in these studies are based on a small number of pancreatic adenocarcinoma cell lines originating from single patients and therefore less representative intended for the potential of these imaging probes in the overall population of pancreatic cancer patients. The translation from bench to bedside of this promising imaging strategy for pancreatic adenocarcinoma currently hinges on the lack of tumor-specific and thoroughly evaluated molecular targets expressed on the general population of pancreatic adenocarcinoma patients for the further development of tumor-targeting contrast agents [15, PF-04979064 16]. == Table 1 . == Overview of the characteristics and preclinical experience with tumor-specific imaging of integrin v6, carcinoembryonic antigen (CEA), hepatocyte growth factor receptor (cMET), epithelial growth factor receptor (EGFR), epithelial cell adhesion molecule (EpCAM), human epidermal growth factor receptor (HER2), urokinase plasminogen activator receptor (uPAR), and vascular endothelial growth factor receptor 2 (VEGFR2) in pancreatic adenocarcinoma animal models ATFamino terminal fragement, CTcomputed tomography, FDAFood and Drug Administration, HGFRhepatocyte growth factor receptor, MABmonoclonal antibody, MPIOmicroparticles of iron oxide, MSOTmultispectral optoacoustic tomographyNIRFnear-infrared fluorescence, NPIOnanoparticles of iron oxide, PCpancreatic cancer, PETpositron emission tomography, scFvsingle-chain antibody fragments, H3F3A SPECTsingle-photon emission computed tomography, uPAurokinase plasminogen activator, USultrasound, VEGFvascular endothelial growth factor, VEGFRvascular endothelial growth factor receptor, XIMABchimeric human-mouse antibodies Therefore , the aim of this study was to explore the suitability of integrin v6, CEA, hepatocyte growth factor receptor (cMET), EGFR, epithelial cell adhesion molecule PF-04979064 (EpCAM), HER2, uPAR, and VEGFR2 as molecular targets intended for tumor-targeted imaging of pancreatic adenocarcinoma patients. The primary endpoint of this study was to evaluate the ability of these markers to distinguish between normal pancreatic tissue and pancreatic and periampullary PF-04979064 adenocarcinoma by performing immunohistochemistry on surgical specimen.