RelB regulates basal and proinflammatory induction of conjunctival CCL2.

Purpose: This study investigated the involvement of NF-kB in regulating postoperative conjunctival inflammation.Methods: Experimental surgery was performed as described for the mouse model of conjunctival scarring. Expression of NF-κB in postoperative conjunctival tissues or conjunctival fibroblasts were assessed by real-time PCR, immunoblotting and immunofluorescence analyses. Downregulation of RelB was achieved using small interfering RNA. Cellular cytokine secretion was determined using multiplex cytokine assay.Results: RelB was the most highly induced member of the NF-kB family on day 2 post-surgery. Elevated RelB may be found associated with vimentin-positive cells and fibroblasts in vivo and in vitro. In conjunctival fibroblasts, RelB may be induced by TNF-α but not TGF-ß2 while its silencing caused selective induction of CCL2 secretion by both basal and TNF-α-stimulated fibroblasts.Conclusions: High RelB induction in the inflammatory phase and the selective modulation of CCL2 suggest a specific anti-inflammatory role for RelB in the postoperative conjunctiva.

The NF-κB subunit RelB regulates the migration and invasion abilities and the radio-sensitivity of prostate cancer cells.

NF-κB subunits play important roles in carcinogenesis of a variety of human malignancies and response to cancer therapy; however, the contribution of an individual subunit has not been thoroughly defined. Constitutive activation of the canonical NF-κB subunit is a critical event in prostate carcinogenesis. Recent findings point out that RelB, which contributes to the non-canonical NF-κB activity, functions importantly in the prostate cancer progression. Here, we investigated systemically the functional roles of RelB in prostate cancer and examine its significance as a therapeutic target. Targeting RelB using short hairpin RNA approach in androgen-independent DU145 prostate cancer cells interfered with various biological behaviors of cells. We observed that RelB knockdown inhibited prostate cancer cell growth, migration, and invasion, and enhanced proteasome inhibitor sensitivity. The altered expression of anti-apoptotic gene Bcl-2 played critical roles in regulating both spontaneous and radiation-induced apoptosis in the presence of RelB knockdown. For the first time, we showed that RelB knockdown significantly attenuated the migration and invasion of DU145 prostate cancer cells, due to the reduction of integrin ß-1. Collectively, we provided evidence that RelB functioned as an oncogene in prostate cancer. Developing a RelB-targeted therapeutic intervention, is valuable in treating advanced, metastatic prostate cancer.

Molecular Response of Human Monocytes Following Interaction with Colon Cancer Cells by Pre-treatment with Low-dose Lipopolysaccharide.

BACKGROUND/AIM: The increased mRNA expression of chemotaxis- and angiogenesis-related factors in human monocytes following interaction with colon cancer cells has been shown to be suppressed by pre-treatment with low-dose lipopolysaccharide (LPS) (100 pg/ml). It has been demonstrated that low-dose LPS reduced the expression of RelB, a member of the nuclear factor (NF)-κB transcription factor family, in mouse macrophages and the NF-κB signaling pathway was important for tumor initiation and growth in tumor-associated macrophages. In addition, the signal transducer and activator of transcription 3 (STAT3) regulated innate immunity via Toll-like receptor (TLR)4 signaling. In the present study, the mRNA expression of signaling pathway- and suppression-related genes in human monocytes following a low-dose LPS treatment and subsequent interaction with colon cancer cells was investigated, in order to assess the molecular response. MATERIALS AND METHODS: The human monocyte cell line THP-1 was treated with LPS and, subsequently, co-cultured with the human colon cancer cell line DLD-1. The mRNA expression of various genes was then analyzed using quantitative real-time polymerase chain reaction (PCR). RESULTS: The mRNA expression of RelB, STAT3, interleukin (IL)-10 and transforming growth factor (TGF)-ß in THP-1 cells following interaction with DLD-1 cells was suppressed by pre-treatment with low-dose LPS (100 pg/ml). CONCLUSION: Treating human monocytes with low-dose LPS may be useful for suppressing tumor progression and may be valuable for maintaining homeostasis.

Decreased expression of the NF-κB family member RelB in lung fibroblasts from Smokers with and without COPD potentiates cigarette smoke-induced COX-2 expression.

BACKGROUND: Heightened inflammation, including expression of COX-2, is associated with COPD pathogenesis. RelB is an NF-κB family member that attenuates COX-2 in response to cigarette smoke by a mechanism that may involve the miRNA miR-146a. There is no information on the expression of RelB in COPD or if RelB prevents COX-2 expression through miR-146a. METHODS: RelB, Cox-2 and miR-146a levels were evaluated in lung fibroblasts and blood samples derived from non-smokers (Normal) and smokers (At Risk) with and without COPD by qRT-PCR. RelB and COX-2 protein levels were evaluated by western blot. Human lung fibroblasts from Normal subjects and smokers with and without COPD, along with RelB knock-down (siRNA) in Normal cells, were exposed to cigarette smoke extract (CSE) in vitro and COX-2 mRNA/protein and miR-146a levels assessed. RESULTS: Basal expression of RelB mRNA and protein were significantly lower in lung cells derived from smokers with and without COPD, the latter of which expressed more Cox-2 mRNA and protein in response to CSE. Knock-down of RelB in Normal fibroblasts increased Cox-2 mRNA and protein induction by CSE. Basal miR-146a levels were not different between the three groups, and only Normal fibroblasts increased miR-146a expression in response to smoke. There was a positive correlation between systemic RelB and Cox-2 mRNA levels and circulating miR-146a levels were higher only in GOLD stage I subjects. CONCLUSIONS: Our data indicate that RelB attenuates COX-2 expression in lung structural cells, such that loss of pulmonary RelB may be an important determinant in the aberrant, heightened inflammation associated with COPD pathogenesis.

Constitutive activation of NF-κB signaling by NOTCH1 mutations in chronic lymphocytic leukemia.

NOTCH1 mutations occur in approximately 10% of patients with chronic lymphocytic leukemia (CLL). However, the relationship between the genetic aberrations and tumor cell drug resistance or disease progression remains unclear. Frameshift deletions were detected by gene sequencing in the NOTCH1 PEST domain in three naive CLL patients. These mutations were associated with chromosomal abnormalities including trisomy 12 or 13q deletion. Of note, one of the patients developed Richter's transformation during FCR treatment. Immunofluorescent and western blot analyses revealed a markedly higher intracellular domain of NOTCH (ICN) expression in the mutated cells compared with their unmutated counterparts and normal CD19+ B lymphocytes (P<0.01 and P<0.001, respectively). In addition, strong DNA-κB binding activities were observed in the mutant cells by gel shift assays. RT-PCR analysis revealed elevated RelA mRNA expression in the mutant cells, while RelB levels were variable. Reduced levels of RelA and RelB mRNA were observed in unmutated CLL and normal B cells. Compared to unmutated CLL and normal B cells, increased apoptosis occurred in the mutant cells in the presence of GSI (ICN inhibitor) and PDTC (NF-κB inhibitor), particularly under the synergistic effects of the two drugs (P=0.03). Moreover, IKKα and IKKß, the active components in the NF-κB pathway, were markedly inhibited following prolonged treatment with GSI and PDTC. These results suggested that NOTCH1 mutations constitutively activate the NF-κB signaling pathway in CLL, which is likely related to ICN overexpression, indicating NOTCH1 and NF-κB as potential therapeutic targets in the treatment of CLL.

Inhibitory effects of fucoxanthinol on the viability of human breast cancer cell lines MCF-7 and MDA-MB-231 are correlated with modulation of the NF-kappaB pathway.

Fucoxanthin is a carotenoid present in the chloroplasts of brown seaweeds. When ingested, it is metabolized mainly to fucoxanthinol in the gastrointestinal tract by digestive enzymes. These compounds have been shown to have many beneficial health effects. The present study was designed to evaluate the molecular mechanisms of action of fucoxanthin and/or of its metabolite fucoxanthinol against viability of estrogen-sensitive MCF-7 and estrogen-resistant MDA-MB-231 breast cancer cell lines. Fucoxanthin and fucoxanthinol reduced the viability of MCF-7 and MDA-MB-231 cells in dose- and time-dependent manners as a result of increased apoptosis. Furthermore, fucoxanthinol-induced apoptosis was more potent than that of fucoxanthin and correlated, for MDA-MB-231 cells, with inhibitory actions on members of the NF-κB pathway p65, p50, RelB, and p52. Being overexpressed and regulated by NF-κB in different types of cancers, the transcription factor SOX9 was also decreased at the nuclear level by fucoxanthin and fucoxanthinol in MDA-MB-231. Taken together, the current results suggest that fucoxanthinol and fucoxanthin could be potentially effective for the treatment and/or prevention of different types of cancers, including breast cancer.

Attenuation of inflammatory mediator production by the NF-κB member RelB is mediated by microRNA-146a in lung fibroblasts.

Lung inflammation can result from exposure to multiple types of inflammatory stimuli. Fibroblasts, key structural cells in the lung that are integral to inflammation and wound healing, produce inflammatory mediators after exposure to stimuli such as IL-1ß. We and others have shown that the NF-κB member RelB has anti-inflammatory properties in mice. Little is known, however, about the anti-inflammatory role of RelB in human cells and how it functions. MicroRNAs (miRNAs), a novel class of small, noncoding RNAs, can mediate inflammatory signaling pathways, including NF-κB, through regulation of target gene expression. Our goal was to analyze the anti-inflammatory properties of RelB in human lung fibroblasts. We hypothesized that RelB regulates inflammatory mediator production in lung fibroblasts in part through a mechanism involving miRNAs. To accomplish this, we transfected human lung fibroblasts with a plasmid encoding RelB and small interfering (si)RNA targeting RelB mRNA to overexpress and downregulate RelB, respectively. IL-1ß, a powerful proinflammatory stimulus, was used to induce NF-κB-driven inflammatory responses. RelB overexpression reduced IL-1ß-induced cyclooxygenase (Cox)-2, PGE2, and cytokine production, and RelB downregulation increased Cox-2 expression and PGE2 production. Furthermore, RelB overexpression increased IL-1ß-induced expression of miRNA-146a, an NF-κB-dependent miRNA with anti-inflammatory properties, whereas RelB downregulation reduced miRNA-146a. miR-146a overexpression ablated the effects of RelB downregulation on IL-1ß-induced Cox-2, PGE2, and IL-6 production, suggesting that RelB mediates IL-1ß-induced inflammatory mediator production in lung fibroblasts through miRNA-146a. RelB and miRNA-146a may therefore be new therapeutic targets in the treatment of lung inflammation caused by various agents and conditions.

RelB inhibits cell proliferation and tumor growth through p53 transcriptional activation.

The alternative nuclear factor-kappaB (NF-κB) -activation pathway proceeds via inducible p100 processing, leading to the activation of RelB-containing dimers. This pathway is aberrantly activated in several types of tumors; however, a direct role for RelB in the control of cell proliferation is still largely unexplored. Here, we demonstrate that RelB provides cell proliferation-inhibitory signals in murine fibroblasts. In agreement with these results, RelB ectopic expression inhibits xenograft tumor growth in vivo, whereas RelB knockdown enhances it. Significantly, we show that RelB inhibits cell proliferation and tumor growth in a p53-dependent manner. Mechanistic studies indicate that RelB regulates the transcription of the p53 tumor-suppressor gene through direct recruitment to the p53 promoter, thus increasing both p53 protein levels and expression of p53 target genes such as p21. Our findings define a novel link between NF-κB and growth-inhibitory pathways involving the RelB-dependent transcriptional upregulation of p53. Furthermore, they suggest that inhibition of RelB in some tumor types that retain wild-type p53 may diminish rather than improve therapeutic responses.

Salmonella transforms follicle-associated epithelial cells into M cells to promote intestinal invasion.

Salmonella Typhimurium specifically targets antigen-sampling microfold (M) cells to translocate across the gut epithelium. Although M cells represent a small proportion of the specialized follicular-associated epithelium (FAE) overlying mucosa-associated lymphoid tissues, their density increases during Salmonella infection, but the underlying molecular mechanism remains unclear. Using in vitro and in vivo infection models, we demonstrate that the S. Typhimurium type III effector protein SopB induces an epithelial-mesenchymal transition (EMT) of FAE enterocytes into M cells. This cellular transdifferentiation is a result of SopB-dependent activation of Wnt/ß-catenin signaling leading to induction of both receptor activator of NF-κB ligand (RANKL) and its receptor RANK. The autocrine activation of RelB-expressing FAE enterocytes by RANKL/RANK induces the EMT-regulating transcription factor Slug that marks epithelial transdifferentiation into M cells. Thus, via the activity of a single secreted effector, S. Typhimurium transforms primed epithelial cells into M cells to promote host colonization and invasion.

NFκB signaling is important for growth of antiestrogen resistant breast cancer cells.

Resistance to endocrine therapy is a major clinical challenge in current treatment of estrogen receptor-positive breast cancer. The molecular mechanisms underlying resistance are yet not fully clarified. In this study, we investigated whether NFκB signaling is causally involved in antiestrogen resistant cell growth and a potential target for re-sensitizing resistant cells to endocrine therapy. We used an MCF-7-derived cell model for antiestrogen resistant breast cancer to investigate dependence on NFκB signaling for antiestrogen resistant cell growth. We found that targeting NFκB preferentially inhibited resistant cell growth. Antiestrogen resistant cells expressed increased p50 and RelB, and displayed increased phosphorylation of p65 at Ser529 and Ser536. Moreover, transcriptional activity of NFκB after stimulation with tumor necrosis factor α was enhanced in antiestrogen resistant cell lines compared to the parental cell line. Inhibition of NFκB signaling sensitized tamoxifen resistant cells to the growth inhibitory effects of tamoxifen but was not sufficient to fully restore sensitivity of fulvestrant resistant cells to fulvestrant. In support of this, depletion of p65 with siRNA in tamoxifen resistant cells increased sensitivity to tamoxifen treatment. Our data provide evidence that NFκB signaling is enhanced in antiestrogen resistant breast cancer cells and plays an important role for antiestrogen resistant cell growth and for sensitivity to tamoxifen treatment in resistant cells. Our results imply that targeting NFκB might serve as a potential novel treatment strategy for breast cancer patients with resistance toward antiestrogen.

Lentiviral-mediated shRNA against RelB induces the generation of tolerogenic dendritic cells.

OBJECTIVE: Lentiviral-mediated shRNA against RelB was used to produce tolerogenic dendritic cells from murine bone marrow derived dendritic cells (BMDCs). METHOD: RelB expression in the BMDCs was silenced by lentivirus carrying RelB shRNA. The apoptosis rate and surface markers of DCs were assessed by flow cytometry. IL-12,IL-10,TGF-ß1 secreted by DCs and DNA binding capacity of NF-κB subunits in the nucleus were measured by ELISA, independently. MLR was used to analyze the capacity of DCs to inhibit immune response. RESULTS: RelB expression was significantly inhibited in DCs following lentiviral mediated delivery of RelB specific shRNA. The RelB shRNA-DC produced lower IL-12 and higher IL-10 than mature dendritic cells (mDCs) and silencing control DCs. There was no difference in the apoptosis rate between shRNA RelB-DCs and mDCs. The expression levels of co-stimulatory molecules (CD80, CD86 and CD83) and MHC-II class molecule were lower in the RelB shRNA-DCs than in the mDCs and silencing control DCs. In addition, RelB shRNA also inhibited the RelB DNA binding capacity but had no effect on other NF-κB subunits. The shRNA RelB-DCs can significantly inhibit mixed lymphocyte reaction (MLR) and down-regulate Th1 cytokines and prompt the production of Th2 cytokines. CONCLUSION: Our results indicate RelB shRNA transfection of DCs can induce the immature status, and produce tolerogenic DCs.

The IKKα-dependent NF-κB p52/RelB noncanonical pathway is essential to sustain a CXCL12 autocrine loop in cells migrating in response to HMGB1.

HMGB1 is a chromatin architectural protein that is released by dead or damaged cells at sites of tissue injury. Extracellular HMGB1 functions as a proinflammatory cytokine and chemoattractant for immune effector and progenitor cells. Previously, we have shown that the inhibitor of NF-κB kinase (IKK)ß- and IKKα-dependent NF-κB signaling pathways are simultaneously required for cell migration to HMGB1. The IKKß-dependent canonical pathway is needed to maintain expression of receptor for advanced glycation end products, the ubiquitously expressed receptor for HMGB1, but the target of the IKKα non-canonical pathway was not known. In this study, we show that the IKKα-dependent p52/RelB noncanonical pathway is critical to sustain CXCL12/SDF1 production in order for cells to migrate toward HMGB1. Using both mouse bone marrow-derived macrophages and mouse embryo fibroblasts (MEFs), it was observed that neutralization of CXCL12 by a CXCL12 mAb completely eliminated chemotaxis to HMGB1. In addition, the HMGB1 migration defect of IKKα KO and p52 KO cells could be rescued by adding recombinant CXCL12 to cells. Moreover, p52 KO MEFs stably transduced with a GFP retroviral vector that enforces physiologic expression of CXCL12 also showed near normal migration toward HMGB1. Finally, both AMD3100, a specific antagonist of CXCL12's G protein-coupled receptor CXCR4, and an anti-CXCR4 Ab blocked HMGB1 chemotactic responses. These results indicate that HMGB1-CXCL12 interplay drives cell migration toward HMGB1 by engaging receptors of both chemoattractants. This novel requirement for a second receptor-ligand pair enhances our understanding of the molecular mechanisms regulating HMGB1-dependent cell recruitment to sites of tissue injury.

RelB enhances prostate cancer growth: implications for the role of the nuclear factor-kappaB alternative pathway in tumorigenicity.

The nuclear factor-kappaB (NF-kappaB) classic pathway is thought to be critical for tumorigenesis, but little is known about the role of the NF-kappaB alternative pathway in cancer development. Recently, high constitutive nuclear levels of RelB have been observed in human prostate cancer specimens with high Gleason scores. Here, we used four complementary approaches to test whether RelB contributes to tumorigenicity of prostate cancer. Inhibiting RelB in aggressive androgen-independent PC-3 cells by stable or conditional expression of a dominant-negative p100 mutant significantly reduced the incidence and growth rate of tumors. The decrease in tumorigenicity coincided with a reduction in the NF-kappaB target interleukin-8 (IL-8). Consistently, down-regulation of RelB by small interfering RNA targeting also reduced tumor growth and decreased levels of IL-8. Conversely, stable expression of RelB in androgen-responsive LNCaP tumors increased the circulating IL-8 levels. Taken together, these results reveal a tumor-supportive role of RelB, implicate the NF-kappaB alternative pathway as a potential target for preventing prostate cancer, and suggest the use of IL-8 as a marker for prostate cancer prognosis.

Effector and regulatory T-cell function is differentially regulated by RelB within antigen-presenting cells during GVHD.

Antigen-presenting cells (APCs) are critical for the initiation of graft-versus-host disease (GVHD), although the responsible APC subset and molecular mechanisms remain unclear. Because dendritic cells (DCs) are the most potent APCs and the NF-kB/Rel family member RelB is associated with DC maturation and potent APC function, we examined their role in GVHD. Within 4 hours of total body irradiation, RelB nuclear translocation was increased and restricted to CD11c(hi) DCs within the host APC compartment. Furthermore, the transient depletion of CD11c(hi) donor DCs that reconstitute in the second week after transplantation resulted in a transient decrease in GVHD severity. By using RelB(-/-) bone marrow chimeras as transplant recipients or RelB(-/-) donor bone marrow, we demonstrate that the induction and maintenance of GVHD is critically dependent on this transcription factor within both host and donor APCs. Critically, RelB within APCs was required for the expansion of donor helper T cell type 1 (Th1) effectors and subsequent alloreactivity, but not the peripheral expansion or function of donor FoxP3(+) regulatory T cells. These data suggest that the targeted inhibition of nuclear RelB translocation within APCs represents an attractive therapeutic strategy to dissociate effector and regulatory T-cell function in settings of Th1-mediated tissue injury.

Benzo(a)pyrene inhibits growth and functional differentiation of mouse bone marrow-derived dendritic cells. Downregulation of RelB and eIF3 p170 by benzo(a)pyrene.

In this study, we have investigated effects of benzo(a)pyrene (BP) on growth and functional differentiation of mouse bone marrow (BM)-derived dendritic cells (DC). 1 microM BP dramatically inhibited growth of BM cultured in the presence of granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin-4 (IL-4). Although little alterations in surface expression of CD11c, major histocompatibility complex (MHC II), and CD86 molecules characteristic of mature DC were induced by BP, production of cytokines including IL-12, IL-10, and TNF-alpha, and allogeneic T cell stimulating ability were severely impaired. Some of the effects of BP were dependent on arylhydrocarbon receptor (AhR), because alpha-naphthoflavone, an AhR antagonist, suppressed the effects of BP on IL-12 production and T cell stimulating ability, but not on DC proliferation. Expression of RelB, a transcription factor necessary for DC differentiation and function, and eIF3 p170, a subunit of eukaryotic translation initiation factor (eIF)3, was reduced upon BP treatment.

[Relationship between surface molecules and RelB gene expression in DC2.4 cell line].

OBJECTIVE: To explore the relationship between the expression of the nuclear factor-kappaB transcription factor RelB gene and the surface molecules in DC2.4 cell line. METHODS: DC2.4 cell line was cultured in complete RPMI 1640 medium, whose morphology was observed with optical microscope and the intracellular structures with transmission electron microscope. Flow cytometry was performed to analyze the surface markers of the cells, including MHC-II, CD86 and CD40, and RelB mRNA expression was detected by RT-PCR. RESULTS: Under optical microscope, the cells appeared irregular in shape with obvious dendritic cell processes, and electron microscopy revealed homogenous fat drops and phagocytic vesicles in the cytoplasm. Flow cytometry demonstrated low expression levels of MHC-II and CD40, but high level of CD86 molecules. Low-level expression of RelB mRNA was detected by RT-PCR, resembling its expression level in bone marrow-derived DC with immature phenotype. CONCLUSION: DC2.4 is a mouse bone marrow dendritic cell line with strong phagocytic capacity, and the low expression of both RelB gene and surface CD40 molecules suggests an immature dendritic cell line.

Induction of RelB participates in endotoxin tolerance.

Using a THP-1 human promonocyte model of endotoxin tolerance that simulates the sepsis leukocyte phenotype, we previously showed that tolerant cells remain responsive to LPS endotoxin with degradation of IkappaB in the cytosol and nuclear translocation and accumulation of p50 and p65 NF-kappaB transcription factors. Despite this, endotoxin-inducible NF-kappaB-dependent innate immunity genes, like IL-1beta, remained transcriptionally unresponsive in the tolerant phenotype, similar to the endotoxin tolerance observed in sepsis patients. In this study, we examined this paradox and found that RelB, another member of the NF-kappaB family, is induced during the establishment of tolerance. RelB expression correlated with IL-1beta repression, and sepsis patients showed increased RelB when compared with normal controls. Transient expression of RelB inhibited IL-1beta in endotoxin-responsive cells. In the inverse experiment, small inhibitory RNAs decreased RelB expression in tolerant cells and restored endotoxin induction of IL-1beta. When we examined tolerant cell extracts, we found transcriptionally inactive NF-kappaB p65/RelB heterodimers. Taken together, our findings demonstrate that RelB can repress proinflammatory gene expression, and suggest that RelB expression in sepsis patient blood leukocytes may play a role in the endotoxin-tolerant phenotype.

Daxx represses expression of a subset of antiapoptotic genes regulated by nuclear factor-kappaB.

Daxx is a nuclear protein that localizes to PML oncogenic domains, sensitizes cells to apoptosis, and functions as a transcriptional repressor. We found that Daxx represses the expression of several antiapoptotic genes regulated by nuclear factor-kappaB, including cIAP2, in human tumor cell lines. Daxx interacts with RelB and inhibits RelB-mediated transcriptional activation of the human cIAP2 gene promoter. Daxx also forms complexes with RelB while bound to its target sites in the cIAP2 promoter, as shown by electrophoretic mobility shift assays and chromatin immunoprecipitation experiments. Using cells from daxx-/- mouse embryos, we observed that levels of the corresponding murine c-IAP mRNA and protein are increased in cells lacking Daxx. Conversely, c-IAP mRNA and protein levels were reduced in relB-/- cells. Taken together, these observations provide a mechanism that links two previously ascribed functions of Daxx: transcriptional repression and sensitization to apoptosis.

[Identification of effective siRNA sequence for RelB silencing in murine dendritic cells with siRNA cassette].

OBJECTIVE: To construct small interfering RNA (siRNA) expression cassette targeting murine RelB gene and identify the most effective siRNA sequence against RelB gene in murine bone marrow-derived dendritic cells (DCs). METHODS: Three expression cassettes namely R1/siRNA, R2/siRNA and R3/siRNA targeting the sites 1027, 302 and 1121 of RelB gene, respectively, were constructed by PCR approach and transfected into cultured murine myeloid DCs by catione liposome Advant-Gene. After incubation for 24 hours in a incubator containing 5% CO(2) at 37 degrees C, the DCs were stimulated by lipopolysaccharide (LPS), and RelB gene expression in DCs were then detected by RT-PCR and immunofluorescence. RESULTS: RT-PCR and immunofluorescence assay showed that the expression of RelB gene in DCs transfected with R2/siRNA could not be upregulated by LPS stimulation, but transfection with R1/siRNA or R3/siRNA failed to produce such effect. CONCLUSION: R2/siRNA is an effective sequence for RelB silencing, and can be a useful means to construct new tolerogenic DC, RNAi RelB DC, for clinical immunotolerance induction.