Abstract B28: Dynamic interplay between type I collagen signaling and invasion in pancreatic cancer

Abstract

Abstract The stroma of pancreatic cancer can restrict as well as promote tumor progression. Why the stroma exhibits these paradoxical functions remains unclear. One of the major components of the pancreatic cancer stroma is fibrillar type I collagen. High levels of collagen in primary tumor specimens have been associated with poor survival and resistance to therapy in pancreatic cancer patients. To determine the effects of type I collagen on cancer cell behavior, we performed intravital confocal microscopic imaging in mice. We used mice that expressed GFPtopaz fused to the α2 chain of type I collagen under control of a 3.6kb fragment of the COL1A1 promoter [α2(I)-col-GFP mice]. Live imaging of pancreatic tumors, formed after orthotopic injection of cells derived from the classical KPC mouse models, showed that type I collagen architecture in the tumors was heterogeneous. Strikingly, we observed that invasive cancer cells migrated out of the tumors on linear type I collagen. Linearization of collagen fibers through cross-linking, catalyzed by lysyl oxidases (LOXs), is inversely correlated with metastasis-free survival in breast cancer. However, in our pancreatic cancer model, inhibiting LOX promoted collagen linearization, tumor growth and metastatic spread. Elevated collagen-mediated signaling, through activation of focal adhesion kinase (FAK) and discoidin domain receptor (DDR1), was also observed in the tumors treated with lysyl oxidase inhibitor. Lysyl oxidase inhibition also promoted cell contractility as shown by elevated phosphorylated mysosin light chain 2 (p-MLC2) in vivo and by in collagen contractility assays in vitro. TGF-β signaling is a potent stimulator of collagen secretion and of invasive behavior, and it is aberrantly regulated in pancreatic cancer. We observed that lysyl oxidase inhibitor increased phosphorylated Smad3, a downstream effector of TGF-β signaling. Together, our data suggest that the influence of collagen on tumor behavior depends on its architecture. In areas of linear collagen, we find high cancer cell motility out of the tumors and this correlates with increased FAK and TGF-β signaling activity. The architecture-specific function of collagen could potentially explain the paradoxical role for the stroma in pancreatic cancer progression. Citation Format: Mario A. Shields, Pascal Maguin, Sarah L. Dallas, Mikala Egeblad.{Authors}. Dynamic interplay between type I collagen signaling and invasion in pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr B28.