4-1BB protects dendritic cells from prostate cancer-induced apoptosis

Prostaglandin E2 Inhibits Prostate Cancer Progression by Countervailing Tumor Microenvironment-Induced Impairment of Dendritic Cell Migration through LXRα/CCR7 Pathway

Migration and homing of dendritic cells (DCs) to lymphoid organs are quite crucial for T cell-induced immune response against tumor. However, tumor microenvironment can make some tumor cells escape immune response by impairing DC migration. Prostaglandin E2 (PGE2) plays important roles in initiating and terminating inflammatory responses. In this study, we investigated whether PGE2 could inhibit murine prostate cancer progression by countervailing tumor microenvironment-induced impairment of dendritic cell migration. We found that murine prostate cancer cell line RM-1-conditioned medium impaired chemotactic movement of marrow-derived DCs and splenic cDCs toward CC chemokine receptor-7 (CCR7) ligand CCL19 in vitro and migration to draining lymph gland in vivo. Meanwhile, it also induced LXRα activation and CCR7 inhibition on maturing DCs. However, the treatment of PGE2 rescued this impairment of DC migration with upregulation of CCR7 and inhibition of LXRα. Further, it was observed that PGE2 also increased MMP9 expression and activated Notch1 signaling on DCs. In RM-1-bearing mouse model, PGE2 treatment was identified to inhibit tumor growth and induce more tumor-infiltrating T cells and CD11c dendritic cells in tumor sites. Therefore, our findings may demonstrate a new perspective for therapeutic interventions on prostate cancer immunoescape.

Low-frequency ultrasound-induced VEGF suppression and synergy with dendritic cell-mediated anti-tumor immunity in murine prostate cancer cells in vitro

High tumor vascular endothelial growth factor (VEGF) levels are associated with poor treatment outcomes in prostate cancer (PCa), and immune deficiency in the PCa microenvironment, especially suppression of dendritic cell (DC) proliferation, has been confirmed. In this study, we (1) investigated whether VEGF participates in DC suppression in murine PCa cells (RM-1), (2) down-regulated VEGF expression using low-frequency ultrasound and microbubbles (UM), and (3) further explored any synergistic effect on immunological activation. DCs from the bone marrow of BALB/c mice were stimulated by the addition of cytokines (granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4)), and we analyzed their proliferation status via flow cytometric recognition of the surface antigen markers CD11c and CD83. The results demonstrated that co-culture with RM-1 cells markedly inhibited expression of the general marker CD11c and the mature marker CD83; UM weakened this inhibition by down-regulating VEGF expression. T lymphocytes were extracted from murine spleens, and CD4 and CD8a were identified as the biomarkers of activated cells participating in the anti-tumor immune response. When DCs, T lymphocytes and RM-1 cells were co-cultured, cell migration and invasion assays and cytoactive detection showed that UM could not only directly suppress PCa cell evolution but also promote activation of anti-tumor immunocytes in the VEGF-inhibited microenvironment.

Dendritic cell maturation and survival are differentially regulated by TNFR1 and TNFR2

The capacity of dendritic cells (DC) to regulate adaptive immunity is controlled by their maturation state and lifespan. Although TNF is a well-known maturation and survival factor for DC, the role of the two TNFR, TNFR1 and TNFR2, in mediating these effects is poorly understood. By using unique TNF variants that selectively signal through TNFR1 and/or TNFR2, we demonstrate differential functions of TNFR in human monocyte-derived and blood CD1c(+) DC. Activation of TNFR1, but not TNFR2, efficiently induced DC maturation, as defined by enhanced expression of cell surface maturation markers (CD83, CD86, and HLA-DR) as well as enhanced T cell stimulatory capacity. In contrast, both TNFR1 and TNFR2 significantly protected DC against cell death, indicating that innate signals can promote DC survival in the absence of DC maturation. We further show differential activation of NF-κB signaling pathways by the TNFR: TNFR1 activated both the p65 and p52 pathways, whereas TNFR2 triggered p52, but not p65, activation. Accordingly, the p65 NF-κB pathway only played a role in the prosurvival effect of TNFR1. However, cell death protection through both TNFR was mediated through the Bcl-2/Bcl-xL pathway. Taken together, our data show that TNFR1, but not TNFR2, signaling induces DC maturation, whereas DC survival can be mediated independently through both TNFR. These data indicate differential but partly overlapping responses through TNFR1 and TNFR2 in both inflammatory and conventional DC, and they demonstrate that DC maturation and DC survival can be regulated through independent signaling pathways.