br essential for the development
essential for the development of an eﬀective diagnosis and treatments for this disease.
Pancreatic cancer is characterized by a dense stroma called des-moplasia, which plays a crucial role during tumor development [4,5]. The LSL-KrasG12D/+;LSL-Trp53R172H/+;Pdx-1-Cre (KPC) genetically en-gineered mouse model of pancreatic cancer faithfully recapitulating this histopathological feature of the human disease . KPC mice therefore represent a potentially powerful tool to understand the pathophy-siology of human pancreatic cancer . However, in the primary tu-mors of KPC mice, unlike human pancreatic tumors, cancer cell inva-sion into the local pancreatic parenchyma is macroscopically and microscopically apparent before tumor cell dissemination or the for-mation of metastases. Such aggressive local invasion in the KPC mouse
∗ Corresponding author. Department of Surgery and Oncology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Fukuoka, 812-8582, Japan.
∗∗ Corresponding author. E-mail addresses: [email protected] (K. Ohuchida), [email protected] (M. Nakamura).
model may result from the fact that these mice have been engineered to express oncogenic Kras in all types of pancreatic epithelia, including duct, acinar, and islet cells. In the KPC mouse model, a small number of dominant cancer 71-63-6 invade a wide range of pancreatic parenchyma . This suggests that, in contrast to the human pancreas, the pancreas of the KPC mouse, which is composed of acinar cells with Kras or p53 mutation, provides a specific microenvironment conducive to the local invasion of pancreatic cancer cells within the pancreatic parenchyma.
Ductal lesions such as acinar-to-ductal metaplasia (ADM) are fre-quently observed in the pancreas of mice in which PDX-1-positive progenitor cells express oncogenic KrasG12D [9–11]. In preliminary studies, we observed that ADM-like lesions frequently formed around the tumors of KPC mice. ADM induction is dependent upon the phe-notypic plasticity of pancreatic acinar cells, and is accompanied by an altered gene expression, which includes a decrease in acinar markers, and the acquisition of ductal markers [12–14]. ADM is common in chronic pancreatitis where acinar atrophy and fibrosis are extensive [15,16]. ADM has been described in humans and mice, especially in the context of carcinogenesis [17,18]. Furthermore, in human pancreatic tissues, the surrounding acinar atrophy accompanying ADM is also as-sociated with pancreatic intraepithelial neoplasia (PanIN), a precursor lesion of pancreatic cancer . This suggests that acinar atrophy ac-companying ADM is involved in pancreatic carcinogenesis associated with PanIN. We have previously observed acinar atrophy frequently associated with fibrosis remodeling in the invasive fronts of human and murine pancreatic tumors . However, changes in acini morphology, such as acinar atrophy with ADM within the invasive front of a locally invasive tumor, have yet to be examined.
The aim of this study was to determine whether ADM exists within the invasive front of pancreatic cancer and whether the change in acinar morphology is associated with local tumor invasion. In human resected pancreatic cancer tissues, we observed ADM-like lesions in the invasive front of the tumor where acinar atrophy was apparent. We further demonstrate that cancer-associated ADM lesions induce des-moplasia and tumor cell invasion of the local parenchyma in a mouse model of pancreatic cancer. We demonstrate for the first time that ADM is a distinct characteristic of the invasive front in pancreatic cancer.
2. Materials and methods
Detailed information is provided in the Supplementary Materials and methods.
2.1. Human pancreatic tissues
Tissue samples were obtained from patients who underwent surgical resection for pancreatic cancer at Kyushu University Hospital. The study was approved by the Ethics Committee of Kyushu University and conducted according to the Ethical Guidelines for Human Genome/ Gene Research enacted by the Japanese Government and the Helsinki Declaration.
Human and mouse tissues were cut into 4-μm-thick sections and then subjected to hematoxylin and eosin (H&E) staining. In addition, immunohistochemistry was performed using rabbit anti-transforming growth factor alpha (TGFα; ab9585, Abcam, Cambridge, UK; 1:100 dilution), mouse anti-CK19 (sc-376126, Santa Cruz Biotechnology, Dallas TX, USA; 1:100 dilution), mouse anti-amylase (sc-46657, Santa Cruz Biotechnology; 1:100 dilution), or mouse anti-α-smooth muscle actin (αSMA) (#M0851, Dako, 1:100) primary antibody, followed by incubation with secondary antibody (En Vision System; K4002, Dako, Troy, MI, USA).