The role of innate immune cells as modulators of the tumor microenvironment in the metastasis and treatment of pancreatic cancer

Pancreatic cancer is a highly aggressive disease, which is often diagnosed late. Consequently, metastasis is common among newly diagnosed patients, leading to a poor prognosis and high mortality rates. The tumor microenvironment of pancreatic cancer, which comprises pancreatic cancer cells, stromal cells, and immune cells, as well as a multitude of extracellular components, plays a pivotal role in cancer progression and metastasis. Conventional immunotherapies focused on targeting the adaptive immune response have achieved suboptimal outcomes in patients with pancreatic cancer. Thus, the focus has shifted toward targeting innate immune cells, which can infiltrate the pancreatic tumor and contribute to the development and maintenance of the immunosuppressive microenvironment to promote tumor growth and metastasis. This review focuses on the roles of innate immune cells and their interactions in the shaping of an immunosuppressive tumor microenvironment to promote the metastasis of pancreatic cancer. In addition, we review strategies that target innate immune cells to remodel the immunosuppressive tumor microenvironment and improve the prognosis of pancreatic cancer.