Extracellular matrix architecture promotes immunosuppressive microenvironments in pancreatic cancer

Abstract

• While it is now becoming clear that heterogeneous stromal architectures in tumors are critical drivers of disease progression and resistance to therapy, our understanding interactions between stromal architecture and key immune cell populations is extremely limited. In both human and murine tissues, we quantitatively define distinct TAM behaviors defined by matrix architectures.’ • We further establish through quantitative analysis of cell alignment that extracellular matrix patterns, which provide contact guidance, promote anisotropic TAM cell shapes that drive polarization. In this context, traction force anisotropies dictate the orientation and directional persistence of cells that encounter guidance cues. This results in TAMs that upregulate markers associated with alternatively activated macrophages. • We demonstrate that the physical mechanism governing TAM shape through interactions with aligned collagen fibers not only upregulate markers of alternatively activated macrophages, but results in robust immunosuppression of CD8+ T cells with significant reductions in both T cell proliferation and migration. • We demonstrate that the fibroinflammatory response associated with pancreatitis, a significant risk factor for developing PDA, results in formation of matrix architectures that are conducive for macrophage alignment and polarization (toward alternatively activated macrophages), suggesting that risk-producing fibroinflammatory disease may prime the stroma to maintain, or later facilitate, local immunosuppression. • To uncover molecular mechanisms associated with our identified physical mechanism, we examined key mechanotransduction signaling pathways and identify focal adhesion kinase (FAK) as a targetable molecular regulator of the macrophage polarization process. To rigorously test our conclusions, we performed a series in vitro and in vivo experiments targeting FAK. Analysis of aligned TAM phenotypes in vivo in genetically engineered murine models following inhibition of FAK demonstrates a shift in matrix induced TAM polarization. Thus, our data suggest that targeting FAK, or other therapeutic strategies to re-engineer tumor microenvironments could reduce immunosuppression in TMEs. It may be beneficial to employ stroma targeting strategies to treat precursor diseases such as pancreatitis to remove stromal architectures that increase risk for establishing early immunosuppression. . Pancreatic ductal adenocarcinoma (PDA) is an aggressive cancer with poor clinical outcomes, due in part to altered fibrotic environments and striking immune dysfunction. Physical properties within tumors, such as aligned extracellular matrix (ECM) fiber architectures, are fundamental to cancer progression and outcome. However, the influence of ECM alignment on immune cell localization and function within tumors, particularly PDA, remains largely unexplored. Here, analysis of mouse and human PDA reveal an inextricable link between collagen architecture and the distribution of immunosuppressive macrophages in both early preinvasive disease and invasive carcinomas. In vitro characterization of primary macrophages demonstrates alignment alone is sufficient to induce elongation, polarization, and immunosuppressive activity, including suppression of CD8+ T cell proliferation and motility. Analysis reveals differential focal adhesion kinase (FAK) activity in aligned macrophages, while FAK inhibition (FAKi) disrupts the immunosuppressive phenotype that emerges from encountering ECM alignment. Furthermore, FAKi in vivo significantly reduces the correlation between elongated immunosuppressive macrophages and aligned collagen, further highlighting the opportunity for FAKi to target stromal immunity. Importantly, the correlation between aligned collagen and immunosuppressive macrophages is also observed in human chronic pancreatitis, a known PDA risk factor that has recently been shown to prime stromal ECM alignments for early dissemination, suggesting that precursor disease is also likely to create stromal memory conducive to early immunosuppression. Taken together, these results support a model in which collagen architecture supports early establishment and maintenance of an immunosuppressive microenvironments and defines a role for targeting stromal matrices to “reprogram” patient immunity.

Topics & Concepts