Dense fibrosis and a robust macrophage infiltrate are key therapeutic barriers in pancreatic ductal adenocarcinoma (PDAC). CD40 activation can disrupt these barriers by inducing macrophages, originating from peripheral blood monocytes, to deplete fibrosis. The precise mechanism and therapeutic implications of this anti-fibrotic activity, though, remain unclear. Here, we report that IFN-gamma and CCL2 released systemically in response to a CD40 agonist cooperate to redirect a subset of Ly6C+CCR2+ monocytes/macrophages to infiltrate tumors and deplete fibrosis. Whereas CCL2 is required for Ly6C+ monocyte/macrophage infiltration, IFN-gamma is necessary for tumor-infiltrating monocytes/macrophages to shift the profile of matrix metalloproteinases (MMPs) in tumors leading to MMP-dependent fibrosis degradation. In addition, MMP13-dependent loss of extracellular matrix components induced by a CD40 agonist increased PDAC sensitivity to chemotherapy. Our findings demonstrate that fibrosis in PDAC is a bidirectional process that can be rapidly altered by manipulating a subset of tumor-infiltrating monocytes leading to enhanced chemotherapy efficacy.
- Received August 25, 2015.
- Revision received February 17, 2016.
- Accepted February 17, 2016.
- Copyright © 2016, American Association for Cancer Research.