Understanding the immune landscape and tumor microenvironment of pancreatic cancer to improve immunotherapy.

Immunotherapy has revolutionized cancer treatment for several hematologic and solid organ malignancies; however, pancreatic cancer remains unresponsive to conventional immunotherapies. Several characteristics of pancreatic cancer present challenges to successful treatment with immunotherapy, including its aggressive biology, poor immunogenicity, and abundant desmoplastic stroma which can impede effector T cell infiltration and promote an immunosuppressive microenvironment. In this review, we evaluate the current understanding of the immune and stromal landscapes of pancreatic cancer, discuss the successes and failures of stroma-targeted therapies, and highlight how stroma-directed therapies may be synergistic with immunotherapy.