Role of the tumor microenvironment in pancreatic cancer

Pancreatic cancer remains a highly recalcitrant disease despite the development of systemic chemotherapies. New treatment options are thus urgently required. Dense stromal formation, so‐called “desmoplastic stroma,” plays controversial roles in terms of pancreatic cancer growth, invasion, and metastasis. Cells such as cancer‐associated fibroblasts, endothelial cells, and immune cells comprise the tumor microenvironment of pancreatic cancer. Pancreatic cancer is considered an immune‐quiescent disease, but activation of immunological response in pancreatic cancer may contribute to favorable outcomes. Herein, we review the role of the tumor microenvironment in pancreatic cancer, with a focus on immunological aspects.