Hypoxia promotes inflammatory fibroblast formation in pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma (PDAC) is a deadly malignancy characterized by poor response to all existing therapies. Although immunotherapy has shown great promise against multiple deadly cancers, it has been largely ineffective in PDAC. This lack of response is in part attributed to its extensive, fibroinflammatory stroma and hypoxic microenvironment. Cancer-associated fibroblasts (CAFs) are the predominant stromal cell type in PDAC, and single-cell transcriptomics of human and mouse PDAC has recently revealed a distinct CAF subpopulation, inflammatory CAFs (iCAFs). These inflammatory fibroblasts produce high levels of cytokines and chemokines in PDAC, and have the potential to contribute to its immunosuppressive microenvironment and tumorigenesis. By injecting a hypoxia probe into PDAC mouse models, we recently found that iCAFs predominantly reside in hypoxic tumor regions. We also observed that the hypoxia-related gene signature is positively enriched in iCAFs in human PDAC samples. Importantly, by exposing three-dimensional (3D) co-cultures of pancreatic cancer cells and fibroblasts to either hypoxia or normoxia, we showed that hypoxia induces IL1α from cancer cells and that IL1α is required for hypoxia-mediated iCAF formation. Our data implicate hypoxia as a critical regulator of tumor stroma. Efforts are ongoing to understand the role of hypoxia in the crosstalk between cancer cells, fibroblasts, and immune cells in driving an immunosuppressive tumor microenvironment. Supported by a grant from the NIH (T32 AI007413) and the University of Michigan Rackham Merit Fellowship.