CpG oligodeoxynucleotides (ODN) activate immune cells to produce immune mediators by Toll-like receptor 9 (TLR9)-mediated signal transduction, which activates mitogen-activated protein kinases (MAPKs) and nuclear factor-κB (NF-κB) through the MyD88/IRAK/TRAF6 kinases cascade. However, the precise mechanisms of CpG ODN activation of immune cells have not been fully elucidated. The small GTP-binding protein Ras mediates MAPK activation in response to a variety of stimuli. Up to now, it is not clear whether Ras plays a role in CpG ODN signaling. In the present study, we found that the dominant-negative version of Ras (RasN17) and specific Ras inhibitor, FTI-277, inhibited CpG ODN-induced nitric oxide (NO) and tumor necrosis factor-α (TNF-α) production by murine macrophage cell line RAW264.7. While overexpression of wild-type Ras enhanced CpG ODN-induced extracellular signal-regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and NF-κB activation, overexpression of RasN17 inhibited CpG ODNinduced ERK, JNK, and NF-κB activation. RasN17 overexpression also inhibited CpG ODN-induced IRAK1/TRAF6 complex formation. Further studies revealed that CpG ODN activated Ras in a time-and dose-dependent manner, and Ras associated with TLR9 in a CpG ODN-dependent manner. Most interestingly, activation of Ras preceded the association of Ras with TLR9, giving rise to a possibility that Ras activation might not be dependent on the interaction between Ras and TLR9. Our data demonstrate for the first time that Ras can be activated by CpG ODN in macrophages, and Ras is involved in CpG ODN signaling as an early event by associating with TLR9 and promoting IRAK1/TRAF6 complex formation, and MAPK and NF-κB activation.

We report the cloning and functional characterization of human cyclin L2, a novel member of the cyclin family. Human cyclin L2 shares significant homology to cyclin L1, K, T1, T2, and C, which are involved in transcriptional regulation via phosphorylation of the C-terminal domain of RNA polymerase Ⅱ. The cyclin L2 protein contains an N-terminal "cyclin box" and C-terminal dipeptide repeats of alternating arginines and serines, a hallmark of the SR family of splicing factors. A new isoform and the mouse homologue of human cyclin L2 have also been cloned in this study. Human cyclin L2 is expressed ubiquitously in normal human tissues and tumor cells. We show here that cyclin L2 co-localizes with splicing factors SC-35 and 9G8 within nuclear speckles and that it associates with hyperphosphorylated, but not hypophosphorylated, RNA polymerase Ⅱ and CDK p110 PITSLRE kinase via its N-terminal cyclin domains. It can also associate with the SC-35 and 9G8 through its RS repeat region. Recombinant cyclin L2 protein can stimulate in vitro mRNA splicing. Overexpression of human cyclin L2 suppresses the growth of human hepatocellular carcinoma SMMC 7721 cells both in vitro and in vivo, inducing cellular apoptosis. This process involves up-regulation of p53 and Bax and decreased expression of Bcl-2. The data suggest that cyclin L2 represents a new member of the cyclin family, which might regulate the transcription and RNA processing of certain apoptosis-related factors, resulting in tumor cell growth inhibition and apoptosis.

Dendritic cell (DC)-based tumor vaccine represents a promising approach to the immunotherapy of malignant tumors. We prepared a novel type of DC-based vaccine, stable conjugates of DCs and EL4 cells transduced with cDNA of OVA (E.G7). Immunization with DC-E.G7 conjugates led to generation of T helper (Th) 1 cytokine-producing cells, antigen-specific CD8+T cells, and strong antitumor immunity that is dependent on both CD4+T cells and CD8+T cells. To further increase the potency of the vaccine, interleukin l8-transfected DCs were used to prepare the ILl8DC-E.G7 conjugates. Immunization with such conjugates significantly increased the production of Thl cytokine-producing cells and the number of antigen-specific CD8+T cells, as well as stronger antitumor immunity. Furthermore, the increased Thl cytokine production and stronger antitumor effect were not observed in mice depleted of IFN-γ. These data indicated that DC-tumor cell conjugates are a potent tumor vaccine. Interleukin l8 can be administrated using gene-transfected cells and enhances antitumor immunity, which is mainly mediated by IFN-γ.

Heat shock proteins (HSPs) are reported to act as effective adjuvants to elicit antitumor and anti-infection immunity. Here, we report that Hsp70-like protein 1 (Hsp70L1), a novel HSP derived from human dendritic cells (DCs), has potent adjuvant effects that polarize responses toward Th1. With a calculated molecular weight of 54.8kDa, Hsp70L1 is smaller in size than Hsp70 but resembles it both structurally and functionally. Hsp70L1 shares common receptors on DCs with Hsp70 and can interact with DCs, promoting DC maturation and stimulating secretion of the proinflammatory cytokines interleukin 12p70 (IL-12p70), IL-1β, tumor necrosis factor-α (TNF-α), and the chemokines IP-10, macrophage inflammatory protein-1α (MIP-1α), MIP-1β, and normal T cell expressed and secreted (RANTES). The induction of interferon-γ-inducible protein 10 (IP-10) secretion by Hsp70L1 is not shared by Hsp70, and other functional differences include more potent stimulation of DC IL-12p70, CC-chemokine, and CCR7 and CXCR4 expression by Hsp70L1. Immunization of mice with the hybrid peptide Hsp70L1-ovalbumin (OVA) 257-264 induces an OVA257-264specific Th1 response and cytotoxic T lymphocyte (CTL) that results in significant inhibition of E.G7-OVA tumor growth. The ability of Hsp70L1 to activate DCs indicates its potential as a novel adjuvant for use with peptide immunizations; the Hsp70L1 antigen peptide hybrid may serve as a more effective vaccine for the control of cancer and infectious diseases.

Migration of dendritic cells (DCs) into tissues and secondary lymphoid organs plays a crucial role in the initiation of innate and adaptive immunity. In this article, we show that cyclosporin A (CsA) impairs the migration of DCs both in vitro and in vivo. Exposure of DCs to clinical concentrations of CsA neither induces apoptosis nor alters development but does impair cytokine secretion, chemokine receptor expression, and migration. In vitro, CsA impairs the migration of mouse bone marrow-derived DCs toward macrophage inflammatory protein-3β (MIP-3β) and induces them to retain responsiveness to MIP-1α after lipopolysaccharide (LPS)-stimulated DC maturation, while in vivo administration of CsA inhibits the migration of DCs out of skin and into the secondary lymphoid organs. CsA impairs chemokine receptor and cyclooxygenase-2 (COX-2) expression normally triggered in LPS-stimulated DCs; administration of exogenous prostaglandin E2 (PGE2) reverses the effects of CsA on chemokine receptor expression and DC migration. Inhibition of nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathway signaling by CsA may be responsible for the CsA-mediated effects on the regulation of chemokine receptor and cyclooxygenase-2 (COX-2) expression. Impairment of DC migration due to inhibition of PGE2 production and regulation of chemokine receptor expression may contribute, in part, to CsAmediated immunosuppression.