The regulation of HIF-1α is considered to be realized by pVHL-mediated ubiquitin-26S proteasome pathway at a posttranscriptional level. The discovery of a class of small noncoding RNAs, called microRNAs, implies alternative mechanism of regulation of HIF-1α. Here, we show that miR-20b plays an important role in fine-tuning the adaptation of tumor cells to oxygen concentration. The inhibition of miR-20b increased the protein levels of HIF-1α and VEGF in normoxic tumor cells; the increase of miR-20b in hypoxic tumor cells, nevertheless, decreased the protein levels of HIF-1α and VEGF. By using luciferase reporter vector system, we confirmed that miR-20b directly targeted the 39UTR of Hif1a and Vegfa. On the other hand, the forced overexpression of HIF-1α in normoxic tumor cells downregulated miR-20b expression. However, HIF-1α knockdown in hypoxic tumor cells caused the increase of miR-20b. The differential expression of miR-20b has important biological significance in tumor cells, either enhancing the growth or favoring the survival of tumor cells upon the oxygen supply. Thus, we identify a novel molecular regulation mechanism through which miR-20b regulates HIF-1α and VEGF and is regulated by HIF-1α so to keep tumor cells adapting to different oxygen concentrations.

IL-17 is a pivotal proinflammatory molecule in asthmatics. However, the cellular source of IL-17 in asthma has not been identified to date. In this study, we report that macrophages rather than Th17 cells are the main producer of IL-17 in allergic inflammationrelated to asthma. After OVA challenge in a mouse model mimicking allergic asthma, the increased IL-17+ cells in the lung were mainly CD11b F4/80 macrophages, instead of T cells or others. Importantly, IL-17+ alveolar macrophages (AMs), but not IL-17+ interstitial macrophages, were significantly increased after allergen challenge. The increase of IL-17+ AMs was not due to the influx of IL-17+ macrophages from circulation or other tissues, but ascribed to the activation of AMs by mediator(s) secreted by IgE/OVA-activated mast cells. Depleting alveolar macrophages or neutralizing IL-17 prevented the initiation of OVA-induced asthma-related inflammation by inhibiting the increase of inflammatory cells and inflammatory factors in bronchoalveolar lavage fluid. Th2 cytokine IL-10 could down-regulate IL-17 expression in alveolar macrophages. The increased IL-17 and the decreased IL-10 in bronchoalveolar lavage fluid were further confirmed in asthmatic patients. These findings suggest that IL-17 is mainly produced by macrophages but not Th17 cells in allergic inflammation related to asthma. Mast cell-released mediators up-regulate the expression of IL-17 by macrophages, whereas IL-10 down-regulates IL-17 expression.

t that tumor-infiltrating mast cells remodel tumor microenvironment and promote tumorgrowth. Mast cell infiltration and activation in tumors were mainly mediated by tumor-derived stem cell factor (SCF) and its receptor c-Kit on mast cells. Low concentrations of SCF efficiently induced the chemotactic migration of mast cells. Tumor-infiltrating mast cells, activated by higher concentrations of SCF, expressed multiple proinflammatory factors and increased IL-17 expression in tumors. The activity of NF-κB and AP-1 in tumor cells was intensified in the mast cell–remodeled inflammatory microenvironment. SCFactivated mast cells also exacerbated tumor immunosuppression by releasing adenosine and increasing T regulatory cells, which augmented the suppression of T cells and natural killer cells in tumors. These findings emphasize that the remodeling of the tumor microenvironment can actually be initiated by tumor cell–released SCF and suggest that mast cells are not only a participator but also a critical regulator of inflammation and immunosuppression in the tumor microenvironment.

Immunotherapy can effectively suppress tumor, yet complete tumor eradication occurs infrequently. The metastatic potential of remnant tumor cells after immunotherapy and the underlying mechanisms have not been fully elucidated. Here, we report that the termination of immunotherapy strikingly increases the metastatic potential of remnant melanoma. This is mainly due to the withdrawal of IFN-γ after immunotherapy. The relief of IFN-γ stress led to the increase of ανβ3 integrin expression in B16 cells, which increased the adhesion of B16 cells to fibrinogen, fibronectin and laminin. Through ανβ3 signaling, the activation of FAK, upregulation of cdc2, production of active MMP-2 and MMP-9 and actin polymerization were intensified in B16 cells stimulated with ECM molecules 24 h after the withdrawal of IFN-γ. The i.v. injection of such tumor cells into mice resulted in more metastatic tumor nodes in lung and shortened the survival of mice. The pitfall of immunotherapy termination can be remedied by the administration of recombinant CBD-HepII polypeptide of fibronectin, which effectively inhibits ανβ3 signaling. These findings suggest that the risk of tumor metastasis can be increased after the termination of immunotherapy, due to the withdrawal of IFN-γ and that targeting ανβ3 signaling pathway can improve the therapeutic effect of immunotherapeutic approaches by reducing such metastaticrisk.

Condylomata acuminata derived from the infection of human papillomavirus is a common sexually transmitted disease. AlthoughT cell-mediated cellular immunity is considered as the main arm against such infection, the regulation of T cell immune responses in genital condylomata is unclear to date. In this study, we analyzed FOXP3+ regulatory T cells in genital condylomata of patients.The results show that FOXP3+ regulatory T cells with suppressive function accumulated in large warts. Consistently, the immunosuppressive milieu in large warts was characterized by high expression of IL-10 and TGF-β1 and low expression of IL-2 and IFN-γ. The responsiveness of wart-infiltrating T cells both in vitro and in vivo can be increased by depleting FOXP3+ T cells. The accumulation of FOXP3+ regulatory T cells in large warts can be partly ascribed to the chemotaxis of CCL17 and CCL22, derived from Langerhans cells and macrophages in wart. Although such accumulation favors the local immunosuppression, it seems not to influence the systemic immunity. In conclusion, these findings demonstrate that FOXP3+ regulatory T cells play an important role in genital condylomata, which has multiple implications in the comprehensive treatment of condylomata acuminata.

The use of costimulatory molecules targeting distinct T-cell signaling pathways has provided a means for triggering and enhancing antitumor immunity; however, it is still not fully understood what types of costimulatory molecules are suitable for the combination in tumor therapy.Our purpose in this study is to establish an effective antitumor immune approach byusing costimulatory molecule 4-1BBL in combinationwith soluble PD-1.

The contribution of bacterial infection to tumorigenesis is usually ascribed to infection-associated inflammation. An alternate view is that direct interaction of bacteria with tumor cells promotes tumor progression. Here, we show that the microenvironment of large tumors favors bacterial survival, which in turn directly accelerates tumor growth by activatingtumor cell Toll-like receptors (TLR). Listeria monocytogenes (Lm)sur vives in the microenvironment of large but not small tumors, resulting in the promotion of tumor growth. Lm did not affect the percentage of regulatory T cells or myeloid suppressor cells in the tumor. Through TLR2 signaling, Lm activated mitogen-activated protein kinases and nuclear factor-κB in tumor cells, resulting in the increased production of nitric oxide and interleukin-6 and increased proliferation of tumor cells. All of these effects were abrogated by silencingexpression of TLR2, but not TLR4. The interaction of Helicobacter pylori with tumor cells from gastric carcinoma patients resulted in similar effects. These findings provide a new insight into infection-associated tumorigenesis and illustrate the importance of antibiotic therapy to treat tumors with bacterial infiltration.

In addition to direct effect on tumor cells, the tumor-promoting activity of CCL2 has been ascribed to its role in chemoattracting tumor-associated macrophages. However it is unclear whether CCL2 also attracts other immune regulatory cells during tumor development. In this study, we confirmed the ubiquitous expression of CCR2 in myeloid suppressor cells (MSCs), a main inducer for tumor immune evasion, and identified that cancer patient-derived CCL2 mediated the migration of MSCs to tumors in vitro, which could be interdicted by antibodies neutralizing CCL2 or blocking CCR2. In mouse tumor model, the adoptively transferred CCR2-/-MSCs could not migrate to either tumor or spleen as efficiently as WT MSCs. The absence of CCL2/CCR2 signaling hindered both MSC migration and MSC-promoted tumor growth. Our data provide evidence that CCL2/CCR2 pathway plays a pivotal role in MSC migration, which is a novel mechanism through which CCL2 promotes tumor growth.

Toll-like receptor (TLR) and interferon-γ (IFN-γ) signaling pathways are important for both innate and adaptive immune responses.However, the cross-talk between these two signaling pathways is incompletely understood. Here we show that IFN- and LPS synergistically induce the expression of proinflammatory factors, including interleukin-1 (IL-1), IL-6, IL-12, NO, and tumor necrosis factor-α(TNF-α). Comparable synergism was observed between IFN-γ and peptidoglycan (PGN; a TLR2 ligand) and poly(I:C) (a TLR3 ligand) in the induction of IL-12 promoter activity. IFN-γ enhanced lipopolysaccharide (LPS)-induced ERK and JNK phosphorylation but had no effect on LPS-induced NF-κB activation.Interestingly, we found that IRF-8/-macrophages were impaired in the activation of LPS-induced ERK and JNK and the production of proinflammatory cytokines induced by LPS or IFN-γ plus LPS.Retroviral transduction of IRF-8 into IRF-8/-macrophages rescued ERK and JNK activation. Furthermore, co-immunoprecipitation experiments show that IRF-8 physically interacts with TRAF6 at a binding site between amino acid residues 356 and 305 of IRF-8. Transfection of IRF-8 enhanced TRAF6 ubiquitination, which is consistent with a physical interaction of IRF-8 with TRAF6. Taken together, the results suggest that the interaction of IRF-8 with TRAF6 modulates TLR signaling and may contribute to the crosstalk between IFN-γ and TLR signal pathways.

The accumulation of myeloid suppressor cells (MSCs) is associated with immune suppression in tumor-bearing mice and in cancer patients. The suppressive activity of MSC correlates with the expression of the myeloid markers Gr-1, CD115 (macrophage colony-stimulating factor receptor), and F4/80. Gr-1+CD115+MSCs, in addition to being able to suppress T-cell proliferation in vitro, can induce the development of Foxp3+Tregulatory cells (Treg) in vivo, which are anergic and suppressive. Furthermore, the secretion of interleukin (IL)-10 and transforming growth factor-B by Gr-1+CD115+ MSCs was induced and enhanced, respectively,on IFN-; stimulation. The development of Treg requires antigen-associated activation of tumor-specific T cells, depends on the presence of IFN-; and IL-10, and is independent of the nitric oxide-mediated suppressive mechanism by MSC. Our data provide evidence that Gr-1+CD115+MSC can mediate the development of Treg in tumor-bearing mice and show a novel immune suppressive mechanism by which MSCs can suppress antitumor responses.