Pancreatic ductal adenocarcinomas are highly malignant cancers characterized by extensive invasion into surrounding tissues, metastasis to distant organs, and a limited response to therapy. A main feature of pancreatic ductal adenocarcinomas is desmoplasia, which leads to extensive deposition of collagen I. We have demonstrated that collagen I can induce epithelialmesenchymal transition (EMT) in pancreatic cancer cells. A hallmark of EMT is an increase in the expression of the mesenchymal cadherin N-cadherin. Previously we showed up-regulation of N-cadherin promotes tumor cell invasion and that collagen I-induced EMT is mediated by two collagen receptors, ␣21-integrin and discoidin domain receptor 1 (DDR1). DDR1 is a receptor-tyrosine kinase widely expressed during embryonic development and in many adult tissues and is also highly expressed in many different cancers. In the signaling pathway initiated by collagen, we have shown proline-rich tyrosine kinase 2 (Pyk2) is downstream of DDR1. In this study we found isoform b of DDR1 is responsible for collagen I-induced up-regulation of N-cadherin and tyrosine 513 of DDR1b is necessary. Knocking down Shc1, which binds to tyrosine 513 of DDR1b via its PTB (phosphotyrosine binding) domain, eliminates the upregulation of N-cadherin. The signaling does not require a functional SH2 domain or the tyrosine residues commonly phosphorylated in Shc1 but is mediated by the interaction between a short segment of the central domain of Shc1 and the proline-rich region of Pyk2. Taken together, these data illustrate DDR1b, but not DDR1a, mediates collagen I-induced N-cadherin up-regulation, and Shc1 is involved in this process by coupling to both DDR1 and Pyk2.Pancreatic cancer is currently the fourth leading cause of cancer-related mortality in the United States with a 5-year survival rate of ϳ6% (American Cancer Society, 2014). This unfortunate outcome is mainly due to the aggressive behavior of this cancer and the lack of symptoms early in the disease. One of the major features of pancreatic cancer is that during the early stages an extensive stromal reaction occurs called desmoplasia. A dense stroma forms, which consists of myofibroblasts (pancreatic stellate cells), abundant extracellular matrix, and different types of inflammatory cells including macrophages, mast cells, lymphocytes, and plasma cells (1, 2). The extracellular matrix components include collagens, fibronectin, hyaluronic acid, and proteoglycans, whereas the major part is type I collagen (3, 4).The atypical stroma plays many roles in pancreatic cancer. It changes the normal architecture of pancreatic tissue and induces an abnormal configuration of blood and lymphatic vessels resulting in a hypovascular and hypoxic microenvironment. It also presents a barrier to drug delivery and promotes tumor immunologic tolerance (2, 4). Previously, our laboratory showed that collagen I can induce epithelial-mesenchymal transition (EMT) 2 -like changes in pancreatic cancer mediated by two collagen receptors, ␣21-integrin and ...