Spatial heterogeneity of immune regulators drives dynamic changes of local immune responses, affecting disease outcomes in pancreatic cancer.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is considered a low immunogenic tumor with "cold" tumor microenvironment (TME) and is mostly unresponsive to immune checkpoint blockade therapies. Here we decipher the impact of intratumoral heterogeneity of immune determinants on antitumor response. We performed spatial proteomic and transcriptomic analyses and multiplexed immunofluorescence on multiple tumor regions, including tumor center (TC) and invasive front (IF), from 220 PDAC-patients, classified according to their transcriptomic immune signaling into high-immunogenic (HI-PDACs, n=54) and low-immunogenic tumors (LI-PDACs, n=166). Spatial compartments (tumor: Pancytokeratin+/CD45- and leukocytes: Pancytokeratin-/CD45+) were defined by fluorescent imaging. HI-PDACs exhibited higher densities of cytotoxic T lymphocytes with upregulation of T-cell priming-associated immune determinants, including CD40, ITGAM, GITR, CXCL10, GZMB, IFNG and HLA-DR, which was significantly more prominent at the IF than the TC. In contrast, LI-PDACs exhibited immune evasive TMEs with downregulation of immune determinants and a negative gradient from TC to IF. Patients with HI-PDACs had significantly better outcomes; however, they showed more frequently exhausted immune phenotypes. Our results indicate strategic differences in the regulation of immune determinants, which lead to different levels of effectiveness of antitumor responses between high- and low-immunogenic tumors and dynamic spatial changes, which affect the evolution of immune evasion and patient outcomes. This supports coevolution of tumor and immune cells and may help define therapeutic vulnerabilities to improve antitumor immunity and harness the responsiveness to immune checkpoint inhibitors in PDAC patients.