The Fearon laboratory studies the interaction between cancer and the immune system. Our underlying premise is that the tumor microenvironment is immune suppressive because cancer cells elicit responses characteristic of wound healing and tissue regeneration. This approach has led to the finding that activated fibroblasts in the tumor stroma mediate immune suppression in several mouse models of cancer, including the autochthonous model of pancreatic ductal adenocarcinoma of the Tuveson lab. Our understanding of the basis of immune suppression is evolving, but we know that it involves the production of the chemokine, CXCL12, by the fibroblastic stromal cells, binding of this CXCL12 by pancreatic cancer cells, and exclusion of T cells from the vicinity of the cancer cells. T cell exclusion, which also occurs in several types of human adenocarcinomas, causes antagonists of T cell checkpoints to be ineffective, despite the presence of cancer-specific CD8+ T cells. This immune suppression is interrupted by administering AMD3100, an inhibitor of CXCR4, the receptor for CXCL12, which leads to the rapid accumulation of T cells amongst cancer cells, thereby uncovering the efficacy of anti-PD-L1 and eliminating cancer cells. Since human pancreatic cancer has certain immunological characteristics of the mouse model, a phase 1 clinical trial of AMD3100 in patients with pancreatic cancer will be initiated in 2015. Some of our next steps are to determine the biological process that causes cancer cells to express non-mutated, shared antigens, and the means by which dormant metastases escape immune elimination.