TNFSF15 facilitates the differentiation of CD11b+ myeloid cells into vascular pericytes in tumors

OBJECTIVE

Immature vasculature lacking pericyte coverage substantially contributes to tumor growth, drug resistance, and cancer cell dissemination. We previously demonstrated that tumor necrosis factor superfamily 15 (TNFSF15) is a cytokine with important roles in modulating hematopoiesis and vascular homeostasis. The main purpose of this study was to explore whether TNFSF15 might promote freshly isolated myeloid cells to differentiate into CD11b+ cells and further into pericytes.

METHODS

A model of Lewis lung cancer was established in mice with red fluorescent bone marrow. After TNFSF15 treatment, CD11b+ myeloid cells and vascular pericytes in the tumors, and the co-localization of pericytes and vascular endothelial cells, were assessed. Additionally, CD11b+ cells were isolated from wild-type mice and treated with TNFSF15 to determine the effects on the differentiation of these cells.

RESULTS

We observed elevated percentages of bone marrow-derived CD11b+ myeloid cells and vascular pericytes in TNFSF15-treated tumors, and the latter cells co-localized with vascular endothelial cells. TNFSF15 protected against CD11b+ cell apoptosis and facilitated the differentiation of these cells into pericytes by down-regulating Wnt3a-VEGFR1 and up-regulating CD49e-FN signaling pathways.

CONCLUSIONS

TNFSF15 facilitates the production of CD11b+ cells in the bone marrow and promotes the differentiation of these cells into pericytes, which may stabilize the tumor neovasculature.

Human group3 innate lymphoid cells express DR3 and respond to TL1A with enhanced IL-22 production and IL-2-dependent proliferation

Death receptor 3 (DR3, TNFRSF25) is expressed by activated lymphocytes and signaling by its ligand, TL1A, enhances cytokine expression and proliferation. Recent studies show that DR3 is also present on murine type 2 innate lymphoid cells (ILC2s). Here, we show that DR3 is expressed by IL-22-producing human group 3 innate lymphoid cells (ILC3s). Stimulation of ILC3s with exogenous TL1A alone had no impact on cytokine production or proliferation. Addition of TL1A to IL-1β + IL-23 significantly enhanced the amount IL-22 produced by ILC3s as well as the percentage IL-22- and IL-8-producing cells. Addition of TL1A to IL-1β + IL-23 also augmented ILC3 proliferation. Mechanistically, this occurred through the upregulation of CD25 and responsiveness to IL-2 stimulation. The combination of TL1A, IL-1β+ IL-23, and IL-2 expanded ILC3s while IL-1β+ IL-23 did not increase proliferation above controls. After 2 weeks of expansion, ILC3s maintained their phenotype, transcription factor expression, and function (IL-22 production). These findings identify DR3 as a costimulatory molecule on ILC3s that could be exploited for ex vivo expansion and clinical use.

Naive and activated T cells display differential responsiveness to TL1A that affects Th17 generation, maintenance, and proliferation

Tumor necrosis factor (TNF)-like cytokine (TL1A) is a T-cell costimulator that bolsters cytokine-induced activation through death receptor 3 (DR3). To explore the relationship between T-cell activation and TL1A responsiveness, flow cytometry profiled DR3 expression in resting and activated T cells. In human CD4(+) T cells, DR3 was induced rapidly following activation and expressed prominently by interleukin (IL)-17-secreting T cells (Th17). Splenic T cells from wild-type and DR3-deficient mice showed that TL1A activation of DR3 inhibits Th17 generation (81 ± 2.6% at 100 ng/ml TL1A) from naive T cells. This response was not associated with suppression of T-cell proliferation. Using neutralizing antibodies or T cells derived from genetically modified mice, TL1A inhibition of Th17 development was found to be independent of IL-2, IL-27, γIFN, IFNAR1, and STAT1. Under suboptimal TCR activation, TL1A continued to block IL-17A secretion, however, the reduced threshold of TCR engagement was now linked with an increase in TL1A-driven proliferation. In contrast, fully committed Th17 cells displayed an altered TL1A responsiveness and in the absence of TCR costimulation supported the maintenance of T cell IL-17A expression. Consequently, TL1A orchestrates unique outcomes in naive and effector T-helper cells, which may affect the proliferation, differentiation and maintenance of Th17 cells in peripheral compartments and inflamed tissues.