No abstract

Adipose stem/stromal cells (ASCs) after isolation produce numerous angiogenic growth factors. This justifies their use to promote angiogenesis per transplantation. In parallel, local coimplantation of ASC with endothelial cells (ECs) leading to formation of functional vessels by the donor cells suggests the existence of a mechanism responsible for fine-tuning ASC paracrine activity essential for vasculogenesis. As expected, conditioned media (CM) from ASC promoted ECs survival, proliferation, migration, and vasculogenesis. In contrast, media from EC-ASC cocultures had neutral effects upon EC responses. Media from cocultures exhibited lower levels of vascular endothelial growth factor (VEGF), hepatic growth factor, angiopoietin-1, and stromal cell-derived factor-1 compared with those in ASC CM. Activin A was induced in ASC in response to EC exposure and was responsible for overall antivasculogenic activity of EC-ASC CM. Except for VEGF, activin A diminished secretion of all tested factors by ASC. Activin A mediated induction of VEGF expression in ASC, but also upregulated expression of VEGF scavenger receptor FLT-1 in EC in EC-ASC cocultures. Blocking the FLT-1 expression in EC led to an increase in VEGF concentration in CM. In vitro pre-exposure of ASC to low number of EC before subcutaneous coimplantation with EC resulted in decrease in vessel density in the implants. In vitro tests suggested that activin A was partially responsible for this diminished ASC activity. This study shows that neovessel formation is associated with induction of activin A expression in ASC; this factor, by affecting the bioactivity of both ASC and EC, directs the crosstalk between these complementary cell types to establish stable vessels. STEM CELLS 2015;33:3039-3051 SIGNIFICANCE STATEMENTThis is the first study demonstrating that direct interaction of adipose stromal cells (ASC) with endothelial cells (EC) shifts the composition of factors secreted by ASC. ASC exposure to EC dramatically decreases ASC secretion of multiple angiogenic factors. Moreover, EC-ASC interaction induces secretion of angiostatic factor activin A by ASC. Current approaches using ASC for vascular therapies are based on the hypothesis that locally delivered ASC will provide their therapeutic effect by the secretion of angiogenic factors. However, the findings of this study suggest that ASC paracrine activity may substantially change after injection, therefore potentially diminishing the effect of therapy.

Immunostimulatory cytokines can enhance anti-tumor immunity and are part of the therapeutic armamentarium for cancer treatment. We have previously reported that post-transplant lymphoma patients have an acquired deficiency of signal transducer and activator of transcription 4, which results in defective IFNγ production during clinical immunotherapy. With the goal of further improving cytokine-based immunotherapy, we examined the effects of a soybean peptide called lunasin that synergistically works with cytokines on natural killer (NK) cells. Peripheral blood mononuclear cells of healthy donors and post-transplant lymphoma patients were stimulated with or without lunasin in the presence of IL-12 or IL-2. NK activation was evaluated, and its tumoricidal activity was assessed using in vitro and in vivo tumor models. Chromatin immunoprecipitation assay was performed to evaluate the histone modification of gene loci that are regulated by lunasin and cytokine. Adding lunasin to IL-12- or IL-2-stimulated NK cells demonstrated synergistic effects in the induction of IFNG and GZMB involved in cytotoxicity. The combination of lunasin and cytokines (IL-12 plus IL-2) was capable of restoring IFNγ production by NK cells from post-transplant lymphoma patients. In addition, NK cells stimulated with lunasin plus cytokines displayed higher tumoricidal activity than those stimulated with cytokines alone using in vitro and in vivo tumor models. The underlying mechanism responsible for the effects of lunasin on NK cells is likely due to epigenetic modulation on target gene loci. Lunasin represents a different class of immune modulating agent that may augment the therapeutic responses mediated by cytokine-based immunotherapy.