Background: Vascular endothelial growth factor (VEGF) is a potent pro-angiogenic signal associated with the growth and metastasis of tumors. In addition, VEGF has also been implicated in the suppression of immune cell function. The purpose of this study was to characterize VEGF secretion, receptor expression and effect of soluble VEGF neutralization in human lymph node cells both at rest and during activation.
Methods: Human lymph nodes derived from patients with melanoma (IRB CASE 3610) containing T cells, B cells, monocyte/macrophages and dendritic cells were cultured with anti-CD3/CD28 beads and IL-2 in order to induce an inflammatory response in vitro. Culture supernatant was assayed for the presence of soluble VEGF on days 4, 7, 11 and 14 of culture. Multiparameter FACS analysis was performed to assess the cell surface expression of VEGF receptor subtypes 1 and 2 over the 14-day culture period. In addition, intracellular expression of cytokines within effector T cells was assessed at the end of the culture. Finally, a parallel culture containing a VEGF neutralizing antibody was performed to assess the effect of VEGF neutralization on effector T cell phenotype. High-throughput T cell receptor CDR3 sequencing was used to determine the molecular sequence of the variable region of the T cell receptors (ImmunoSEQ, Seattle, WA).
Results: VEGF was measureable in the culture supernatant on days 4 and beyond. The proportion of cells expressing intracellular VEGF peaked at day 4 and subsequently decreased. CD11b+(monocyte/macrophage), CD11c+ (dendritic cells) and CD19+ (B) cells had the highest proportion of cells which expressed intracellular VEGF. VEGF R1 and R2 were not constitutively expressed on resting immune cells, but receptor expression was upregulated upon activation of the T cells in vitro. Day 14 T cells demonstrated intracellular IFN-γ, IL-2 and TNF-α. The addition of VEGF-blocking antibody in the culture of MDLN cells effectively neutralized the amount of soluble VEGF detected in the culture supernatant at all days. The addition of the VEGF-blocking antibody also increased the proportion of T cells expressing intracellular IFN-γ as compared T cells in the non-VEGF blocked culture and resulted in distinct molecularly defined T cell clones.
Conclusion: These results confirm that soluble VEGF is produced by immune cells during activation, even in the absence of tumor. VEGF receptor expression on lymph node immune cell subsets is constitutive, but low, and then upregulated during in vitro activation of T cells, presumably due to secondary cytokine production. Neutralization of soluble VEGF resulted in qualitative differences in effector cytokine expression and T cell receptor sequences. Whether the effect on these T cells is direct via VEGF interaction with the cognate receptor or from an indirect effect on antigen-presenting cells is currently under investigation.
Citation Format: Madeleine P. Strohl, Hallie Graor, Mei Zhang, Anthony Visioni, John Ammori, Isabelle Rivers-McCue, Julian Kim. Immunomodulatory effects of VEGF on human lymph node antigen-presenting and lymphoid cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 16. doi:10.1158/1538-7445.AM2014-16