Human Pancreatic Cancer Cells Induce a MyD88-Dependent Stromal Response to Promote a Tumor-Tolerant Immune Microenvironment.

Cancer cells exert mastery over the local tumor-associated stroma (TAS) to configure protective immunity within the tumor microenvironment. The immunomodulatory character of pancreatic lysates of patients with cancer differs from those with pancreatitis. In this study, we evaluated the cross-talk between pancreatic cancer and its TAS in primary human cell culture models. Upon exposure of TAS to pancreatic cancer cell-conditioned media, we documented robust secretion of IL6 and IL8. This TAS response was MyD88-dependent and sufficient to directly suppress both CD4+ and CD8+ T-cell proliferation, inducing Th17 polarization at the expense of Th1. We found that patients possessed a similar shift in circulating effector memory Th17:Th1 ratios compared with healthy controls. The TAS response also directly suppressed CD8+ T-cell-mediated cytotoxicity. Overall, our results demonstrate how TAS contributes to the production of an immunosuppressive tumor microenvironment in pancreatic cancer. Cancer Res; 77(3); 672-83. ©2016 AACR. ©2016 American Association for Cancer Research.