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Natural killer (NK) cells eliminate cancer cells in a contact-dependent manner. However, how NK cells find cancer cells remain unclear. Here, using time-lapse imaging, we investigated how individual NK cells migrate toward cancer cells. Although naïve B16F10 cancer cells produce low levels of chemokines, IFN-γ-treated B16F10 cells secreted high levels of CXCL10, low levels of CCL5, but did not secrete CCL2, CCL7, or CXCL12. Wild-type NK cells migrated well toward cancer cells and killed them, whereas NK cells deficient in CXCR3 did not. CXCR3-deficient NK cells also showed slower migration speed than did wild-type NK cells. Taken together, our data show that NK cells find cancer cells, at least in part, by sensing CXCL10 produced by cancer cells and suggest that a strategy to increase CXCL10 secretion by cancer cells may improve the efficacy of NK cell-based immunotherapy.

Angelica dahurica is used in functional foods for the prevention and treatment of various diseases, such as inflammation and cancer. In the present study, we examined the effect of A. dahurica polysaccharide (ADP) on dendritic cell (DC) maturation. ADP increased the expressions of CD86 and MHC-II molecules, the production of IL-12, IL-1β, and TNF-α, and allogeneic T cell activation ability of DCs, and reduced DC endocytosis. As a mechanism of action, the knockdown of TLR4 with small interfering RNA decreased the ADP-induced production of nitric oxide and IL-12 by DCs, suggesting the membrane receptor candidate of ADP. After binding to TLR4, ADP increased the phosphorylation of ERK, JNK, and p38 MAPKs, and the nuclear translocation of NF-κB p50/p65. These results indicate that ADP activates DCs through TLR4 and downstream signalings.

Maturation of dendritic cells (DCs) is a critical factor for initiating the immune response. However, DC maturation is usually attenuated in the tumor microenvironment, which is an important immunological problem in DC-based immunotherapy against cancer. Here, we report the effect of a polysaccharide (PLP) isolated from Pueraria lobata on phenotypic and functional maturation of DCs. Phenotypic maturation was demonstrated by increased expression of CD40, CD86, and major histocompatibility complex I/II. PLP induced functional maturation of DCs, as shown by increased production of interleukin (IL)-12, IL-1β, and tumor necrosis factor-α, decreased antigen capture capacity, and enhanced allogenic T cell stimulation. In addition, PLP activated DCs generated from C3H/HeN mice with normal TLR4, but not DCs from C3H/HeJ mice with mutated TLR4, suggesting that the TLR4 is a membrane receptor of PLP. We showed that PLP increased ERK, JNK, and p38 mitogen-activated protein kinase phosphorylation, and nuclear translocation of the nuclear factor-kappaB p65 subunit, which are signaling molecules downstream of TLR4. These results indicate that PLP induced DC maturation through TLR4 signaling.

Maturation of dendritic cells (DCs) is usually attenuated in the tumor microenvironment, which is an important immunological problem in DC-based immunotherapy of cancer. In this study, we report the effect of a Mori fructus polysaccharide (MFP) on DC maturation. MFP was treated to DCs generated from mouse BM cells. MFP induced phenotypic maturation of DCs, as proven by the increased expression of CD40, CD80/86, and MHC-I/II molecules. MFP induced functional maturation of DCs, in that MFP increased the expression of IL-12, IL-1β, TNF-α, and IFN-β, decreased antigen capture capacity, and enhanced allogenic T cell stimulation. MFP efficiently induced maturation of DCs from C3H/HeN mice having normal toll-like receptor4 (TLR4), but not DCs from C3H/HeJ mice having mutated TLR4, suggesting that TLR4 might be one of the membrane receptors of MFP. As a mechanism of action, MFP increased phosphorylation of mitogen-activated protein kinase (MAPKs), and nuclear translocation of NF-κB p65 subunit, which were important signal molecules downstream from TLR4. These data suggest that MFP induces DC maturation through TLR4 and MFP can be used as an adjuvant in DC-based cancer immunotherapy.

CD226 is an activating receptor expressed on natural killer (NK) cells, CD8+ T cells, and other immune cells. Upon binding to its ligands expressed on target cells, CD226 activates intracellular signaling that triggers cytokine production and degranulation in NK cells. However, the role of CD226 in contact dynamics between NK and cancer cells has remained unclear. Our time-lapse images showed that individual wild-type CD226+ NK cells contacted B16F10 melanoma cells for 23.7 min, but Cd226−/− NK cells only for 12.8 min, although both NK cell subsets showed equal contact frequency over 4 h. On the surface of B16F10 cells, CD226+ cells stayed at the same site with oscillating movement (named stable contact), while Cd226−/− NK cells moved around at a velocity of 4 μm/min (named unstable contact). Consequently, Cd226−/− NK cells did not kill B16F10 cells in vitro and did not inhibit their metastasis into the lung in vivo. Taken together, our data demonstrate that CD226 enables prolonged stable interaction between NK and cancer cells, which is needed for efficient killing of cancer cells.