Collagen density regulates the activity of tumor-infiltrating T cells

Abstract

BackgroundTumor progression is accompanied by dramatic remodeling of the surrounding extracellular matrix leading to the formation of a tumor-specific ECM, which is often more collagen-rich and of increased stiffness. The altered ECM of the tumor supports cancer growth and metastasis, but it is unknown if this effect involves modulation of T cell activity. To investigate if a high-density tumor-specific ECM could influence the ability of T cells to kill cancer cells, we here studied how T cells respond to 3D culture in different collagen densities.MethodsT cells cultured in 3D conditions surrounded by a high or low collagen density were imaged using confocal fluorescent microscopy. The effects of the different collagen densities on T cell proliferation, survival, and differentiation were examined using flow cytometry. Cancer cell proliferation in similar 3D conditions was also measured. Triple-negative breast cancer specimens were analyzed for the number of infiltrating CD8+ T cells and for the collagen density. Whole-transcriptome analyses were applied to investigate in detail the effects of collagen density on T cells. Computational analyses were used to identify transcription factors involved in the collagen density-induced gene regulation. Observed changes were confirmed by qRT-PCR analysis.ResultsT cell proliferation was significantly reduced in a high-density matrix compared to a low-density matrix and prolonged culture in a high-density matrix led to a higher ratio of CD4+ to CD8+ T cells. The proliferation of cancer cells was unaffected by the surrounding collagen-density. Consistently, we observed a reduction in the number of infiltrating CD8+ T-cells in mammary tumors with high collagen-density indicating that collagen-density has a role in regulating T cell abundance in human breast cancer.Whole-transcriptome analysis of 3D-cultured T cells revealed that a high-density matrix induces downregulation of cytotoxic activity markers and upregulation of regulatory T cell markers. These transcriptional changes were predicted to involve autocrine TGF-β signaling and they were accompanied by an impaired ability of tumor-infiltrating T cells to kill autologous cancer cells.ConclusionsOur study identifies a new immune modulatory mechanism, which could be essential for suppression of T cell activity in the tumor microenvironment.Electronic supplementary materialThe online version of this article (10.1186/s40425-019-0556-6) contains supplementary material, which is available to authorized users.

Engineering T cells to enhance 3D migration through structurally and mechanically complex tumor microenvironments

“…architecture and mechanics) also strongly influence T cell infiltration, and their ability to effectively distribute throughout, and sample, the entire tumor mass. Indeed, the complex stromal reaction in solid tumors can limit access and effective distribution of T cells creating antitumor immunityfree sanctuaries (Elahi-Gedwillo et al, 2019;Hartmann et al, 2014;Kuczek et al, 2019;Salmon et al, 2012;Stromnes et al, 2017). Furthermore, many solid tumors are rich with aligned extracellular matrix (ECM) networks (Best et al, 2019;Provenzano et al, 2006;Ray et al, 2017a) , which provide contact guidance for carcinoma cells (Provenzano et al, 2006(Provenzano et al, , 2008Tabdanov et al, 2018aTabdanov et al, , 2018b, and can also direct migration of infiltrated T cells in solid tumors (Hartmann et al, 2014;Salmon et al, 2012;Wolf et al, 2003).…”

Fractal dimension, occupancy and hotspot analyses of B cell spatial distribution predict clinical outcome in breast cancer

“…It may be that the paths that B and T cells travel along have a branching structure because these cells have to go around physical obstacles such as other cells, blood vessels, and collagen fibers. In addition, T cells are known to follow along the outside of blood vessels and collagen fibers (34,35) which can have a branching architecture.…”

Collagen Density Modulates the Immunosuppressive Functions of Tumor-Associated Macrophages

“…Recently, we have demonstrated that a high collagen density can also directly downregulate the cytotoxic activity of T cells and instead make them more regulatory 15 . Together with the findings of this study, these observations suggest that the collagen density within tumors could be centrally engaged in the formation of an immunosuppressive TME and thus be one of the mechanisms limiting the efficacy of immunotherapy.…”

“…The density and structure of the tumor ECM have been linked to a poor prognosis of several cancers such as breast cancer 8 , pancreatic cancer 9 , gastric cancer 10 , and oral squamous cell carcinomas 11 , but the reason for this correlation is still not clear. It has been demonstrated in vitro that the density and stiffness of the ECM can affect various cell types, including mesenchymal stem cells 12 , fibroblasts 13,14 , T cells 15 , and cancer cells 7,16,17 . This includes the differentiation of mesenchymal stem cells towards a neurogenic or osteogenic lineage when cultured on soft or stiff matrices, respectively 12 , and the stimulation of malignant transformation of two breast epithelial cell lines when cultured on stiff matrices 16 .…”