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Although increasing evidence links the gut microbiota with the development of colorectal cancer, the molecular mechanisms for microbiota regulation of tumorigenesis are not fully understood. Here, we found that a member of the TNFα-induced protein 8 (TNFAIP8) family called TIPE2 (TNFAIP8-like 2) was significantly upregulated in murine intestinal tumors and in human colorectal cancer, and colorectal cancer with high expression of Tipe2 mRNA associated with reduced survival time of patients. Consistent with these findings, TIPE2 deficiency significantly inhibited the development of colorectal cancer in mice treated with azoxymethane/dextran sodium sulfate and in Apcmin/+ mice. TIPE2 deficiency attenuated the severity of colitis by successfully resolving and restricting colonic inflammation and protected colonic myeloid cells from death during colitis. Transplantation of TIPE2-deficient bone marrow into wild-type mice successfully dampened the latter's tumorigenic phenotype, indicating a hematopoietic-specific role for TIPE2. Mechanistically, restricting the expansion of Enterobacteriaceae/Escherichia coli (E. coli) decreased intestinal inflammation and reduced the incidence of colonic tumors. Collectively, these data suggest that hematopoietic TIPE2 regulates intestinal antitumor immunity by regulation of gut microbiota. TIPE2 may represent a new therapeutic target for treating colorectal cancer.

Supplementary Data from Tumor Necrosis Factor-α–Induced Protein 8-Like 2 Fosters Tumor-Associated Microbiota to Promote the Development of Colorectal Cancer

Although increasing evidence links the gut microbiota with the development of colorectal cancer, the molecular mechanisms for microbiota regulation of tumorigenesis are not fully understood. Here, we found that a member of the TNFα-induced protein 8 (TNFAIP8) family called TIPE2 (TNFAIP8-like 2) was significantly upregulated in murine intestinal tumors and in human colorectal cancer, and colorectal cancer with high expression of Tipe2 mRNA associated with reduced survival time of patients. Consistent with these findings, TIPE2 deficiency significantly inhibited the development of colorectal cancer in mice treated with azoxymethane/dextran sodium sulfate and in Apcmin/+ mice. TIPE2 deficiency attenuated the severity of colitis by successfully resolving and restricting colonic inflammation and protected colonic myeloid cells from death during colitis. Transplantation of TIPE2-deficient bone marrow into wild-type mice successfully dampened the latter's tumorigenic phenotype, indicating a hematopoietic-specific role for TIPE2. Mechanistically, restricting the expansion of Enterobacteriaceae/Escherichia coli (E. coli) decreased intestinal inflammation and reduced the incidence of colonic tumors. Collectively, these data suggest that hematopoietic TIPE2 regulates intestinal antitumor immunity by regulation of gut microbiota. TIPE2 may represent a new therapeutic target for treating colorectal cancer.

Supplementary Figures with legends - Supplementary Figures S1 through S4. (1) Supplementary Figure S1 shows that upregulation of CD317 expression correlates with tumorigenesis (supplementary to fig. 1). (2) Supplementary Figure S2 shows CD317 promotes xenograft growth in vivo (Supplementary to Fig. 1). (3) Supplementary Figure S3 shows the effects of CD317 and its artificial mutants in cell cycle regulation (Supplementary to Fig. 2). (4) Supplementary Figure S4 shows that CD317 promotes cell cycle transition through lipid raft-dependent EGFR regulation (Supplementary to Figs 3 and 4). Supplementary Table S1 - Supplementary Table S1 lists the sequences of shRNAs and siRNAs. Supplementary Table S2 - Supplementary Table S2 lists primers of PCR and RT-PCR.

EGFR regulates various fundamental cellular processes, and its constitutive activation is a common driver for cancer. Anti-EGFR therapies have shown benefit in cancer patients, yet drug resistance almost inevitably develops, emphasizing the need for a better understanding of the mechanisms that govern EGFR activation. Here we report that CD317, a surface molecule with a unique topology, activated EGFR in hepatocellular carcinoma (HCC) cells by regulating its localization on the plasma membrane. CD317 was upregulated in HCC cells, promoting cell-cycle progression and enhancing tumorigenic potential in a manner dependent on EGFR. Mechanistically, CD317 associated with lipid rafts and released EGFR from these ordered membrane domains, facilitating the activation of EGFR and the initiation of downstream signaling pathways, including the Ras–Raf–MEK–ERK and JAK–STAT pathways. Moreover, in HCC mouse models and patient samples, upregulation of CD317 correlated with EGFR activation. These results reveal a previously unrecognized mode of regulation for EGFR and suggest CD317 as an alternative target for treating EGFR-driven malignancies.Significance:Activation of EGFR by CD317 in hepatocellular carcinoma cells suggests CD317 as an alternative target for treating EGFR-dependent tumors.

Cancer metastasis accounts for nearly 90% of all cancer deaths. Metastatic cancer progression requires both cancer cell migration to the site of the metastasis and subsequent proliferation after colonization. However, it has long been recognized that cancer cell migration and proliferation can be uncoupled; but the mechanism underlying this paradox is not well understood. Here we report that TNFAIP8 (tumor necrosis factor-α-induced protein 8), a “professional” transfer protein of phosphoinositide second messengers, promotes cancer cell migration or metastasis but inhibits its proliferation or cancer growth. TNFAIP8-deficient mice developed larger tumors, but TNFAIP8-deficient tumor cells completely lost their ability to migrate toward chemoattractants and were defective in colonizing lung tissues as compared to wild-type counterparts. Mechanistically, TNFAIP8 served as a cellular “pilot” of tumor cell migration by locally amplifying PI3K–AKT and Rac signals on the cell membrane facing chemoattractant; at the same time, TNFAIP8 also acted as a global inhibitor of tumor cell growth and proliferation by regulating Hippo signaling pathway. These findings help explain the migration–proliferation paradox of cancer cells that characterizes many cancers.

Genome-wide association studies have established that human REL is a susceptibility gene for lymphoid cancers and inflammatory diseases. REL is the hematopoietic member of the nuclear factor-κB (NF-κB) family and is frequently amplified in human lymphomas. However, the mechanism through which REL and its encoded protein c-Rel affect human lymphoma is largely unknown. Using both loss-of-function and gain-of-function approaches, we studied the roles of REL gene in human Jurkat leukemia cells. Compared with control Jurkat cells, REL knockout cells exhibited significant defects in cell growth and mitochondrial respiration. Genome-wide transcriptome analyses revealed that T cells lacking c-Rel had selective defects in the expression of inflammatory and metabolic genes including c-Myc. We found that c-Rel controlled the expression of c-Myc through its promotor, and expressing c-Myc in c-Rel-deficient lymphoma cells rescued their proliferative and metabolic defects. Thus, the human c-Rel-c-Myc axis controls lymphoma growth and metabolism and could be a therapeutic target for lymphomas.

The recent novel coronavirus disease (COVID-19) outbreak, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is seeing a rapid increase in infected patients worldwide. The host immune response to SARS-CoV-2 appears to play a critical role in disease pathogenesis and clinical manifestations. SARS-CoV-2 not only activates antiviral immune responses, but can also cause uncontrolled inflammatory responses characterized by marked pro-inflammatory cytokine release in patients with severe COVID-19, leading to lymphopenia, lymphocyte dysfunction, and granulocyte and monocyte abnormalities. These SARS-CoV-2-induced immune abnormalities may lead to infections by microorganisms, septic shock, and severe multiple organ dysfunction. Therefore, mechanisms underlying immune abnormalities in patients with COVID-19 must be elucidated to guide clinical management of the disease. Moreover, rational management of the immune responses to SARS-CoV-2, which includes enhancing anti-viral immunity while inhibiting systemic inflammation, may be key to successful treatment. In this review, we discuss the immunopathology of COVID-19, its potential mechanisms, and clinical implications to aid the development of new therapeutic strategies against COVID-19.

Immunotherapy that targets lymphoid cell checkpoints holds great promise for curing cancer. However, many cancer patients do not respond to this form of therapy. In addition to lymphoid cells, myeloid cells play essential roles in controlling immunity to cancer. Whether myeloid checkpoints exist that can be targeted to treat cancer is not well established. Here we show that c-Rel, a member of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) family, specified the generation of myeloid-derived suppressor cells by selectively turning on protumoral genes while switching off antitumoral genes through a c-Rel enhanceosome. c-Rel deficiency in myeloid cells markedly inhibited cancer growth in mice and pharmaceutical inhibition of c-Rel had the same effect. Combination therapy that blocked both c-Rel and the lymphoid checkpoint protein programmed cell death protein 1 was more effective in treating cancer than blocking either alone. Thus, c-Rel is a myeloid checkpoint that can be targeted for treating cancer. Li et al. report that c-Rel, a member of the NF-κB transcription factor family, acts as a checkpoint for antitumor immunity as it promotes the generation of myeloid-derived suppressor cells and its inhibition in myeloid cells suppresses tumor growth.

The intestine is a highly dynamic environment that requires tight control of the various inputs to maintain homeostasis and allow for proper responses to injury. It was recently found that the stem cell niche and epithelium is regenerated after injury by de-differentiated adult cells, through a process that gives rise to Sca1+ fetal-like cells and is driven by a transient population of Clu+ revival stem cells (revSCs). However, the molecular mechanisms that regulate this dynamic process have not been fully defined. Here we show that TNFAIP8 (also known as TIPE0) is a regulator of intestinal homeostasis that is vital for proper regeneration. TIPE0 functions through inhibiting basal Akt activation by the commensal microbiota via modulating membrane phospholipid abundance. Loss of TIPE0 in mice results in injury-resistant enterocytes, that are hyperproliferative, yet have regenerative deficits and are shifted towards a de-differentiated state. Tipe0−/− enterocytes show basal induction of the Clu+ regenerative program and a fetal gene expression signature marked by Sca1, but upon injury are unable to generate Sca-1+/Clu+ revSCs and could not regenerate the epithelium. This work demonstrates the role of TIPE0 in regulating the dynamic signaling that determines the injury response and enables intestinal epithelial cell regenerative plasticity., The molecular mechanisms that regulate intestinal Clu+ revival stem cells (revSCs) and their niche to enable regeneration in response to injury are unclear. Here, the authors show that mice without the phospholipid transport protein, TNFAIP8, causes less revSCs to be induced following injury.

TNFAIP8-like 2 (TIPE2) is a negative regulator of immune receptor signaling that maintains immune homeostasis. Dysregulated TIPE2 expression has been observed in several types of human immunological disorders. However, how TIPE2 expression is regulated remains to be determined. We report in this study that the SCFβ-TrCP E3 ubiquitin ligase regulates TIPE2 protein abundance by targeting it for ubiquitination and subsequent degradation via the 26S proteasome. Silencing of either cullin-1 or β-TrCP1 resulted in increased levels of TIPE2 in immune cells. TAK1 phosphorylated the Ser3 in the noncanonical degron motif of TIPE2 to trigger its interaction with β-TrCP for subsequent ubiquitination and degradation. Importantly, the amount of TIPE2 protein in immune cells determined the strength of TLR 4–induced signaling and downstream gene expression. Thus, our study has uncovered a mechanism by which SCFβ-TrCP E3 ubiquitin ligase regulates TLR responses.

To facilitate rational experimental design and fulfill the NIH requirement of including sex as a biologic variable, we examined the influences of genetic background and sex on responses to intervertebral disc (IVD) injury in the mouse tail. The goal of this study was to compare gene expression and histologic changes in response to a tail IVD injury (needle puncture) in male and female mice on the DBA and C57BL/6 (B6) backgrounds. We hypothesized that extracellular matrix gene expression in response to IVD injury differs between mice of different genetic backgrounds and sex. Consistent changes were detected in gene expression and histologic features after IVD injury in mice on both genetic backgrounds and sexes. In particular, expression of col1a1 and adam8 was higher in the injured IVD of DBA mice than B6 mice. Conversely, col2a1 expression was higher in B6 mice than DBA mice. Sex-associated differences were significant only in B6 mice, in which col2a1 expression was greater in male mice than in female. Histologic differences in response to injury were not apparent between DBA and B6 mice or between males and females. In conclusion, mouse tail IVD showed sex- and strain-related changes in gene expression and histology after needle puncture. The magnitude of change in gene expression differed with regard to genetic background and, to a lesser degree, sex.

Background Colorectal cancer (CRC) is the third leading cause of cancer in the United States, and inflammatory bowel disease patients have an increased risk of developing CRC due to chronic intestinal inflammation with it being the cause of death in 10% to 15% of inflammatory bowel disease patients. TIPE2 (TNF-alpha-induced protein 8-like 2) is a phospholipid transporter that is highly expressed in immune cells and is an important regulator of immune cell function. Methods The azoxymethane/dextran sulfate sodium murine model of colitis-associated colon cancer (CAC) was employed in Tipe2 –/– and wild-type mice, along with colonoid studies, to determine the role of TIPE2 in CAC. Results Early on, loss of TIPE2 led to significantly less numbers of visible tumors, which was in line with its previously described role in myeloid-derived suppressor cells. However, as time went on, loss of TIPE2 promoted tumor progression, with larger tumors appearing in Tipe2 –/– mice. This was associated with increased interleukin-22/STAT3 phosphorylation signaling. Similar effects were also observed in primary colonoid cultures, together demonstrating that TIPE2 also directly regulated colonocytes in addition to immune cells. Conclusions This work demonstrates that TIPE2 has dual effects in CAC. In the colonocytes, it works as a tumor suppressor. However, in the immune system, TIPE2 may promote tumorigenesis through suppressor cells or inhibit it through IL-22 secretion. Going forward, this work suggests that targeting TIPE2 for CRC therapy requires cell- and pathway-specific approaches and serves as a cautionary tale for immunotherapy approaches in general in terms of colon cancer, as intestinal inflammation can both promote and inhibit cancer.

The TIPE2 (tumor necrosis factor-alpha-induced protein 8-like 2) protein is a major regulator of cancer and inflammatory diseases. The availability of its sequence and structure, as well as the critical amino acids involved in its ligand binding, provides insights into its function and helps greatly identify novel drug candidates against TIPE2 protein. With the current advances in deep learning and molecular dynamics simulation-based drug screening, large-scale exploration of inhibitory candidates for TIPE2 becomes possible. In this work, we apply deep learning-based methods to perform a preliminary screening against TIPE2 over several commercially available compound datasets. Then, we carried a fine screening by molecular dynamics simulations, followed by metadynamics simulations. Finally, four compounds were selected for experimental validation from 64 candidates obtained from the screening. With surprising accuracy, three compounds out of four can bind to TIPE2. Among them, UM-164 exhibited the strongest binding affinity of 4.97 µM and was able to interfere with the binding of TIPE2 and PIP2 according to competitive bio-layer interferometry (BLI), which indicates that UM-164 is a potential inhibitor against TIPE2 function. The work demonstrates the feasibility of incorporating deep learning and MD simulation in virtual drug screening and provides high potential inhibitors against TIPE2 for drug development.

The lack of tumor infiltration by CD8

The maturation process of NK cells determines their functionality during which IL-15 plays a critical role. However, very few checkpoints specifically targeting this process have been discovered. Here, we report that TIPE2 expression gradually increased during NK cell ontogenesis correlating to their maturation stages in both mice and humans. NK-specific TIPE2 deficiency increased mature NK cells in mice, and these TIPE2-deficient NK cells exhibited enhanced activation, cytotoxicity, and IFN-γ production upon stimulation and enhanced response to IL-15 for maturation. Moreover, TIPE2 suppressed IL-15–triggered mTOR activity in both human and murine NK cells. Consequently, blocking mTOR constrained the effect of TIPE2 deficiency on NK cell maturation in response to IL-15. Last, NK-specific TIPE2-deficient mice were resistant to tumor growth in vivo. Our results uncover a potent checkpoint in NK cell maturation and antitumor immunity in both mice and humans, suggesting a promising approach of targeting TIPE2 for NK cell–based immunotherapies.

Myeloid-derived Suppressor Cells (MDSCs) are a sub-population of leukocytes that are important for carcinogenesis and cancer immunotherapy. During carcinogenesis or severe infections, inflammatory mediators induce MDSCs via aberrant differentiation of myeloid precursors. Although several transcription factors, including C/EBPβ, STAT3, c-Rel, STAT5, and IRF8, have been reported to regulate MDSC differentiation, none of them are specifically expressed in MDSCs. How these lineage-non-specific transcription factors specify MDSC differentiation in a lineage-specific manner is unclear. The recent discovery of the c-Rel−C/EBPβ enhanceosome in MDSCs may help explain these context-dependent roles. In this review, we examine several transcriptional regulators of MDSC differentiation, and discuss the concept of non-modular regulation of MDSC signature gene expression by transcription factors such as c-Rel and C/EBPß.

Aim: CD19 chimeric antigen receptor (CAR) T cells have been approved by the US FDA for treatment of relapsed and refractory (R/R) B-cell malignancies. Patients & methods: This study investigated the safety and efficacy of autologous 4-1BB costimulatory domain-engineered CD19 CAR-T cells in R/R B-cell lymphoma. Results: After CD19 CAR-T-cell infusion, severe cytokine release syndrome occurred in 28.6% (4/14) of the patients. The overall response rate was 77% with complete remission observed in 6/14 patients at 3 months. A higher tumor burden and grade 3–4 of myelosuppression after chemotherapy were associated with severe cytokine-release syndrome. Notably, combining CD19 CAR-T cells and PD-1 blockade, but not CD19 CAR-T cells alone, reduced intracranial tumor burden in a patient with central invasion of lymphoma. Conclusion: CD19 CAR-T cells could effectively induce tumor remission and PD-1 blockade might improve the efficacy in Chinese patients with R/R B-cell lymphoma.

Myocardial infarction (MI) is a leading cause of death worldwide for which there is no cure. Although cardiac cell death is a well-recognized pathological mechanism of MI, therapeutic blockade of cell death to treat MI is not straightforward. Death receptor 5 (DR5) and its ligand TRAIL [tumor necrosis factor (TNF)–related apoptosis- inducing ligand] are up-regulated in MI, but their roles in pathological remodeling are unknown. Here, we report that blocking TRAIL with a soluble DR5 immunoglobulin fusion protein diminished MI by preventing cardiac cell death and inflammation in rats, pigs, and monkeys. Mechanistically, TRAIL induced the death of cardiomyocytes and recruited and activated leukocytes, directly and indirectly causing cardiac injury. Transcriptome profiling revealed increased expression of inflammatory cytokines in infarcted heart tissue, which was markedly reduced by TRAIL blockade. Together, our findings indicate that TRAIL mediates MI directly by targeting cardiomyocytes and indirectly by affecting myeloid cells, supporting TRAIL blockade as a potential therapeutic strategy for treating MI.

BACKGROUND. Gastrointestinal acute graft-versus-host disease (GVHD) occurring after allogeneic hematopoietic cell transplant is an allo-reactive T cell and inflammatory cytokine driven organ injury with epithelial apoptosis as 1 of its hallmark findings and is associated with significant mortality. Tumor necrosis factor (TNF)-alpha-induced protein 8 (TNFAIP8 or TIPE) acts as a negative mediator of apoptosis via inhibition of caspase-3 activation, promotes cell proliferation and Tipe(−/−) deficiency is associated with increased inflammation. METHODS. To evaluate the role of TIPE in acute GVHD, naive C57BL/6 and Tipe(−/−) C57BL/6 mice were conditioned with 1000 cGy single dose total body irradiation, followed by transplantation of 10 million bone marrow cells and 20 million splenocytes from either syngeneic C57BL/6 or allogeneic BALB/c donors. RESULTS. Allo TIPE-deficient mice developed exacerbated gut GVHD compared with allo controls and had significantly decreased survival (6 wk overall survival: 85% versus 37%; P < 0.05), higher clinical GVHD scores, more profound weight loss, increased serum proinflammatory cytokines (interleukin-17A, TNF, interleukin-6, and interferon-γ). T-cell infiltration into the ileum was increased; epithelial proliferation was decreased along with significantly higher levels of chemokines KC and monokine induced by gamma interferon. Using bone marrow chimeric experiments, TIPE was found to have a role in both hematopoietic and nonhematopoietic cells. CONCLUSIONS. Absence of TIPE results in excessive inflammation and tissue injury after allo-HCT, supporting that TIPE confers immune homeostasis and has tissue-protective function during the development of gut GVHD and may be a potential future target to prevent or treat this complication after allogeneic HCT.

Lymphocytes are some of the most motile cells of vertebrates, constantly navigating through various organ systems. Their specific positioning in the body is delicately controlled by site-specific directional cues such as chemokines. While it has long been suspected that an intrinsic molecular pilot, akin to a ship’s pilot, guides lymphocyte navigation, the nature of this pilot is unknown. Here we show that the TIPE (TNF-α-induced protein 8-like) family of proteins pilot lymphocytes by steering them toward chemokines. TIPE proteins are carriers of lipid second messengers. They mediate chemokine-induced local generation of phosphoinositide second messengers, but inhibit global activation of the small GTPase Rac. TIPE-deficient T lymphocytes are completely pilot-less: they are unable to migrate toward chemokines despite their normal ability to move randomly. As a consequence, TIPE-deficient mice have a marked defect in positioning their T lymphocytes to various tissues, both at the steady-state and during inflammation. Thus, TIPE proteins pilot lymphocytes during migration and may be targeted for the treatment of lymphocyte-related disorders.

Cytokine release syndrome (CRS) remains to be a major adverse effect of chimeric antigen receptor T (CAR-T) cell therapy in B-cell acute lymphoblastic leukemia (B-ALL) and lymphoma. It was urgent to explore novel strategy for managing severe CRS. We conducted a clinical trial to assess the safety and efficacy of CD19-targeting CAR-T-cells in the treatment of relapsed and chemotherapy-refractory B-ALL and lymphoma. A 10-year-old boy with B-ALL who never achieved minimal residual disease (MRD) negative status after 5 courses of chemotherapy was enrolled into our study and received a total of 3.19×106/kg autologous CD19 CAR-T-cells. Before CAR-T-cell infusion, naive lymphocytes made up 41.8% of bone marrow cells, which were reduced to 1% at the 14th day after transfusion, with MRD

Tumour cells evade immune surveillance by upregulating the surface expression of programmed death-ligand 1 (PD-L1), which interacts with programmed death-1 (PD-1) receptor on T cells to elicit the immune checkpoint response1,2. Anti-PD-1 antibodies have shown remarkable promise in treating tumours, including metastatic melanoma2–4. However, the patient response rate is low4,5. A better understanding of PD-L1-mediated immune evasion is needed to predict patient response and improve treatment efficacy. Here we report that metastatic melanomas release extracellular vesicles, mostly in the form of exosomes, that carry PD-L1 on their surface. Stimulation with interferon-γ (IFN-γ) increases the amount of PD-L1 on these vesicles, which suppresses the function of CD8 T cells and facilitates tumour growth. In patients with metastatic melanoma, the level of circulating exosomal PD-L1 positively correlates with that of IFN-γ, and varies during the course of anti-PD-1 therapy. The magnitudes of the increase in circulating exosomal PD-L1 during early stages of treatment, as an indicator of the adaptive response of the tumour cells to T cell reinvigoration, stratifies clinical responders from non-responders. Our study unveils a mechanism by which tumour cells systemically suppress the immune system, and provides a rationale for the application of exosomal PD-L1 as a predictor for anti-PD-1 therapy. Melanoma cells release programmed death-ligand 1 (PD-L1) on the surface of circulating exosomes, suggesting a mechanism by which tumours could evade the immunesystem, and the potential application of exosomal PD-L1 to monitor patient responses to checkpoint therapies.

Decoy receptor 3 (DcR3) is abnormally up-regulated in many cancer cells. It may help cancer cells to escape from immune surveillance and establish metastatic lesions. However, whether DcR3 can be used as a biomarker for the diagnosis of cancer metastasis is unclear. In this study, sera from healthy controls and patients with different cancers were collected, and tested for their DcR3 levels by ELISA. Significantly elevated DcR3 levels were observed in the sera of patients with gastric cancer (2.04 ± 1.01, P = 0.0061), lymphoma (1.62 ± 0.75, P = 0.041), and breast cancer (1.53 ± 0.51, P = 0.023). DcR3 was found to be a suitable biomarker for identifying gastric cancer patients. Importantly, DcR3 was positively associated with platelet distribution width (PDW) (P = 2.45 × 10−6, R = 0.63) in metastatic cancers but negatively associated with hemoglobin (HGB) (P = 0.002, R = −0.59) and hematocrit (HCT) (P = 0.001, R = −0.62) in non-metastatic cancers. Combined with PDW, HGB and HCT, serum DcR3 could be used to predict the occurrence of cancer metastasis. These findings indicate that DcR3 could be used as a biomarker for the diagnosis of gastric cancer, and for cancer metastasis in combination with hematological traits.

The polarization of leukocytes toward chemoattractants is essential for the directed migration (chemotaxis) of leukocytes. How leukocytes acquire polarity after encountering chemical gradients is not well understood. We found here that leukocyte polarity was generated by TIPE2 (TNFAIP8L2), a transfer protein for phosphoinositide second messengers. TIPE2 functioned as a local enhancer of phosphoinositide-dependent signaling and cytoskeleton remodeling, which promoted leading-edge formation. Conversely, TIPE2 acted as an inhibitor of the GTPase Rac, which promoted trailing-edge polarization. Consequently, TIPE2-deficient leukocytes were defective in polarization and chemotaxis, and TIPE2-deficient mice were resistant to leukocyte-mediated neural inflammation. Thus, the leukocyte polarizer is a dual-role phosphoinositide-transfer protein and represents a potential therapeutic target for the treatment of inflammatory diseases.

TNFAIP8-like 2 (TIPE2) is a negative regulator of immune receptor signaling that maintains immune homeostasis. Dysregulated TIPE2 expression has been observed in several types of human immunological disorders. However, how TIPE2 expression is regulated remains to be determined. We report in this study that the SCF

Caspase-8 is a key integrator of cell survival and cell death decisions during infection and inflammation. Following engagement of tumor necrosis factor superfamily receptors or certain Toll-like receptors (TLRs), caspase-8 initiates cell-extrinsic apoptosis while inhibiting RIPK3-dependent programmed necrosis. In addition, caspase-8 has an important, albeit less well understood, role in cell-intrinsic inflammatory gene expression. Macrophages lacking caspase-8 or the adaptor FADD have defective inflammatory cytokine expression and inflammasome priming in response to bacterial infection or TLR stimulation. How caspase-8 regulates cytokine gene expression, and whether caspase-8–mediated gene regulation has a physiological role during infection, remain poorly defined. Here we demonstrate that both caspase-8 enzymatic activity and scaffolding functions contribute to inflammatory cytokine gene expression. Caspase-8 enzymatic activity was necessary for maximal expression of Il1b and Il12b, but caspase-8 deficient cells exhibited a further decrease in expression of these genes. Furthermore, the ability of TLR stimuli to induce optimal IκB kinase phosphorylation and nuclear translocation of the nuclear factor kappa light chain enhancer of activated B cells family member c-Rel required caspase activity. Interestingly, overexpression of c-Rel was sufficient to restore expression of IL-12 and IL-1β in caspase-8–deficient cells. Moreover, Ripk3(−/−)Casp8(−/−) mice were unable to control infection by the intracellular parasite Toxoplasma gondii, which corresponded to defects in monocyte recruitment to the peritoneal cavity, and exogenous IL-12 restored monocyte recruitment and protection of caspase-8–deficient mice during acute toxoplasmosis. These findings provide insight into how caspase-8 controls inflammatory gene expression and identify a critical role for caspase-8 in host defense against eukaryotic pathogens.

B cell receptor engagement induces naive B cells to differentiate and perform critical immune-regulatory functions. Acquisition of functional specificity requires that each cell navigate through checkpoints that control its survival, cell cycle entry, and proliferative expansion. Dynamic changes in BCR-induced calcium concentration critically regulate these checkpoints. Here we establish that variations in BCR signaling strength are encoded as calcium signals that tune each cell’s fate by dynamically regulating NF-κB, NFAT, and mTORC1 dependent control of gene expression. We find that weak BCR signaling induces apoptosis by failing to activate c-Rel-dependent Bcl-xL expression. Progressively stronger signals, which generate quantitatively distinct calcium signals, are required to promote c-Rel dependent survival, drive metabolic reprogramming, initiate cell cycle entry, and drive proliferation via NFAT-, mTORC1-, and Myc-dependent mechanisms. Finally, we establish the mechanism by which CD40 and PAMP costimulation decrease the calcium threshold for these key steps of B cell activation and differentiation. As altered BCR signaling is linked to autoimmunity and B cell malignancies, our results have important implications for understanding the pathogenesis of aberrant B cell differentiation.

Regulatory T (Treg) cells play an integral role in maintaining immune homeostasis and preventing autoimmune diseases. Forkhead box P3 expression marks the commitment of progenitor cells to the Treg lineage. Although the essential function of the nuclear factor (NF)-κB family transcription factor c-Rel in the regulation of natural Treg cells has been firmly established, little is known about whether c-Rel is involved in the in vivo generation of peripheral Treg cells (pTregs), which develop from mature CD4+ conventional T cells outside of the thymus. We sought to answer this question through the induction of pTregs in the eye and gut mucosa using ovalbumin-specific T cell receptor transgenic mice that do or do not express c-Rel. Our results showed that Tregs can be induced in the eye in a c-Rel-dependent manner when immune-mediated inflammation occurs. However, c-Rel is dispensable for the induction of pTregs in the gut mucosa after oral antigen administration. Thus, c-Rel may play distinct roles in regulating the development of pTregs in different organs. Abbreviations ACAID: Anterior Chamber-Associated Immune Deviation; ATF: activating transcription factor; CREB: cAMP responsive element-binding protein; DMEM: Dulbecco minimum essential medium; HBSS: Hanks Balanced Salt Solution; NFAT: Nuclear Factor of Activated T cells; PBS: Phosphate-buffered saline; PE: Phycoerythrin; WT: wild type.

Psoriasis is a chronic inflammatory disorder of the skin. Accumulating evidence indicates that the Rel gene, a member of the NF-κB family, is a risk factor for the disease. We sought to investigate whether psoriasis can be prevented by directly targeting the Rel gene transcript, i.e., the c-Rel mRNA. Using chemically-modified c-Rel specific siRNA (siRel) and poly(ethylene glycol)-b-poly(l-lysine)-b-poly(l-leucine) (PEG-PLL-PLLeu) micelles, we successfully knocked down the expression of c-Rel, and showed that the expression of cytokine IL-23, a direct target of c-Rel that can drive the development of IL-17-producing T cells, was markedly inhibited. More importantly, treating mice with siRel not only prevented but also ameliorated imiquimod (IMQ)-induced psoriasis. Mechanistic studies showed that siRel treatment down-regulated the expression of multiple inflammatory cytokines. Taken together, these results indicate that the susceptibility gene Rel can be targeted to treat and prevent psoriasis.