VEGF-C Promotes Immune Tolerance in B16 Melanomas and Cross-Presentation of Tumor Antigen by Lymph Node Lymphatics

Abstract

Tumor expression of the lymphangiogenic factor VEGF-C is correlated with metastasis and poor prognosis, and although VEGF-C enhances transport to the draining lymph node (dLN) and antigen exposure to the adaptive immune system, its role in tumor immunity remains unexplored. Here, we demonstrate that VEGF-C promotes immune tolerance in murine melanoma. In B16 F10 melanomas expressing a foreign antigen (OVA), VEGF-C protected tumors against preexisting antitumor immunity and promoted local deletion of OVA-specific CD8(+) T cells. Naive OVA-specific CD8(+) T cells, transferred into tumor-bearing mice, were dysfunctionally activated and apoptotic. Lymphatic endothelial cells (LECs) in dLNs cross-presented OVA, and naive LECs scavenge and cross-present OVA in vitro. Cross-presenting LECs drove the proliferation and apoptosis of OVA-specific CD8(+) T cells ex vivo. Our findings introduce a tumor-promoting role for lymphatics in the tumor and dLN and suggest that lymphatic endothelium in the local microenvironment may be a target for immunomodulation.

Lymphatic vessel density is associated with CD8+ T cell infiltration and immunosuppressive factors in human melanoma

“…In concert with primary tumors, our study identifies immune suppressive molecules in tumor-draining LNs, suggesting that immune mechanisms operating in metastatic LNs 25 , 37 , 61 , 62 may at least in part be similar to those in primary tumors. 63 In contrast to primary tumors, we found a significant correlation between LECs and FoxP3 + lymphocytes.…”

“…38-40 In human melanoma, increased intra- and peritumoral LVD as well as the lymphatic growth factor VEGF-C strongly correlate with metastatic dissemination. 17 , 33 , 41-43 Lymphatic vessels may support migration of tumor cells, but may also modulate immune cells, as recently demonstrated in primary tumors and draining LNs in mice, 24 , 25 , 44 raising the possibility that lymphatics mediate immune suppression and poor clinical outcome in cancer patients. 19 , 31 , 42 Because corresponding human data are missing, we performed a very wide IHC analysis.…”

“…35 , 36 Furthermore, VEGF-C overexpression in mouse melanoma promoted an immune suppressive microenvironment in primary and downstream LNs. 24 , 25 To address the potential role of VEGF-C in modulating host anti-tumor immunity in human melanoma, we quantified tumor sections immunostained for VEGF-C and immune markers. Interestingly, in the earliest stages of primary melanoma (melanoma in situ ), we found strong positive correlations between VEGF-C expression and iNOS (Fig.…”

“…24 Furthermore, tumor-associated LECs may directly cross-present tumor antigens to CD8 + T cells and render them dysfunctional in the tumor microenvironment. 25 , 26 LECs can also inhibit the maturation of dendritic cells, 27 secrete inhibitory molecules such as indoleamine 2,3-dioxygénase (IDO), inducible nitric oxide synthase (iNOS) and transforming growth factor beta (TGF-β), and impair T cell activation through expression of inhibitory receptor ligands (e.g. programmed cell death ligand 1 and 2 (PD-L1 and 2)).…”

Immunomodulatory Roles of Lymphatic Vessels in Cancer Progression

“…Large or opsonized antigens are taken up by subcapsular macrophages, whereas smaller antigens flow into small conduits lined with follicular DCs in which they can be taken up directly by antigen-specific B cells (21). On the other hand, LECs have access to all lymph-borne antigens, and it was recently shown that LECs can actively scavenge these antigens, process them intracellularly, and cross-present them to T cells for deletional tolerance (22,23), which is discussed in more detail later. Furthermore, LECs can retain antigen for long periods of time and may play a role in recalling memory T cells (24).…”