Cancer cells that leave the primary tumor can seed metastases in distant organs, and it is thought that this is a unidirectional process. Here we show that circulating tumor cells (CTCs) can also colonize their tumors of origin, in a process that we call "tumor self-seeding." Self-seeding of breast cancer, colon cancer, and melanoma tumors in mice is preferentially mediated by aggressive CTCs, including those with bone, lung, or brain-metastatic tropism. We find that the tumor-derived cytokines IL-6 and IL-8 act as CTC attractants whereas MMP1/collagenase-1 and the actin cytoskeleton component fascin-1 are mediators of CTC infiltration into mammary tumors. We show that self-seeding can accelerate tumor growth, angiogenesis, and stromal recruitment through seed-derived factors including the chemokine CXCL1. Tumor self-seeding could explain the relationships between anaplasia, tumor size, vascularity and prognosis, and local recurrence seeded by disseminated cells following ostensibly complete tumor excision.

Metastasis and chemoresistance in cancer are linked phenomena, but the molecular basis for this link is unknown. We uncovered a network of paracrine signals between carcinoma, myeloid, and endothelial cells that drives both processes in breast cancer. Cancer cells that overexpress CXCL1 and 2 by transcriptional hyperactivation or 4q21 amplification are primed for survival in metastatic sites. CXCL1/2 attract CD11b(+)Gr1(+) myeloid cells into the tumor, which produce chemokines including S100A8/9 that enhance cancer cell survival. Although chemotherapeutic agents kill cancer cells, these treatments trigger a parallel stromal reaction leading to TNF-α production by endothelial and other stromal cells. TNF-α via NF-kB heightens the CXCL1/2 expression in cancer cells, thus amplifying the CXCL1/2-S100A8/9 loop and causing chemoresistance. CXCR2 blockers break this cycle, augmenting the efficacy of chemotherapy against breast tumors and particularly against metastasis. This network of endothelial-carcinoma-myeloid signaling interactions provides a mechanism linking chemoresistance and metastasis, with opportunities for intervention.

The spondyloarthropathies are a group of rheumatic diseases that are associated with inflammation at anatomically distal sites, particularly the tendon-bone attachments (entheses) and the aortic root. Serum concentrations of interleukin-23 (IL-23) are elevated and polymorphisms in the IL-23 receptor are associated with ankyosing spondylitis, however, it remains unclear whether IL-23 acts locally at the enthesis or distally on circulating cell populations. We show here that IL-23 is essential in enthesitis and acts on previously unidentified IL-23 receptor (IL-23R)(+), RAR-related orphan receptor γt (ROR-γt)(+)CD3(+)CD4(-)CD8(-), stem cell antigen 1 (Sca1)(+) entheseal resident T cells. These cells allow entheses to respond to IL-23 in vitro-in the absence of further cellular recruitment--and to elaborate inflammatory mediators including IL-6, IL-17, IL-22 and chemokine (C-X-C motif) ligand 1 (CXCL1). Notably, the in vivo expression of IL-23 is sufficient to phenocopy the human disease, with the specific and characteristic development of enthesitis and entheseal new bone formation in the initial complete absence of synovitis. As in the human condition, inflammation also develops in vivo at the aortic root and valve, which are structurally similar to entheses. The presence of these entheseal resident cells and their production of IL-22, which activates signal transducer and activator of transcription 3 (STAT3)-dependent osteoblast-mediated bone remodeling, explains why dysregulation of IL-23 results in inflammation at this precise anatomical site.

Interleukin-17 (IL-17) has emerged as a central player in the mammalian immune system. Although this cytokine exerts a host-defensive role in many infectious diseases, it promotes inflammatory pathology in autoimmunity and other settings. A myriad of studies have focused on how IL-17-producing cells are generated. However, the means by which IL-17 achieves its effects, either for the benefit or the detriment of the host, are due in large part to the induction of new gene expression. Whereas many IL-17 target genes are common to different disease states, in some cases the effects of IL-17 differ depending on the target cell, infectious site or pathogen. Gene products induced by IL-17 include cytokines (IL-6, granulocyte-colony-stimulating factor, tumour necrosis factor-alpha), chemokines (CXCL1, CXCL2, CCL20, among many others), inflammatory effectors (acute-phase protesins, complement) and antimicrobial proteins (defensins, mucins). Different cell types appear to respond differently to IL-17 in terms of target gene expression, with notable differences seen in mesenchymal and epithelial cells compared with cells of haematopoietic origin. Here, we summarize the major IL-17 target genes that mediate this cytokine's activities in both autoimmune and chronic diseases as well as during various types of infections.

The interleukin (IL)-12p40 family of cytokines plays a critical role in the development of experimental autoimmune encephalomyelitis (EAE). However, the relative contributions of IL-12 and IL-23 to the pathogenic process remain to be elucidated. Here, we show that activation of uncommitted myelin-reactive T cells in the presence of either IL-12p70 or IL-23 confers encephalogenicity. Adoptive transfer of either IL-12p70- or IL-23-polarized T cells into naive syngeneic hosts resulted in an ascending paralysis that was clinically indistinguishable between the two groups. However, histological and reverse transcription-polymerase chain reaction analysis of central nervous system (CNS) tissues revealed distinct histopathological features and immune profiles. IL-12p70-driven disease was characterized by macrophage-rich infiltrates and prominent NOS2 up-regulation, whereas neutrophils and granulocyte-colony-stimulating factor (CSF) were prominent in IL-23-driven lesions. The monocyte-attracting chemokines CXCL9, 10, and 11 were preferentially expressed in the CNS of mice injected with IL-12p70-modulated T cells, whereas the neutrophil-attracting chemokines CXCL1 and CXCL2 were up-regulated in the CNS of mice given IL-23-modulated T cells. Treatment with anti-IL-17 or anti-granulocyte/macrophage-CSF inhibited EAE induced by transfer of IL-23-polarized, but not IL-12p70-polarized, cells. These findings indicate that autoimmunity can be mediated by distinct effector populations that use disparate immunological pathways to achieve a similar clinical outcome.

Influenza-related complications continue to be a major cause of mortality worldwide. Due to unclear mechanisms, a substantial number of influenza-related deaths result from bacterial superinfections, particularly secondary pneumococcal pneumonia. Here, we report what we believe to be a novel mechanism by which influenza-induced type I IFNs sensitize hosts to secondary bacterial infections. Influenza-infected mice deficient for type I IFN-alpha/beta receptor signaling (Ifnar-/- mice) had improved survival and clearance of secondary Streptococcus pneumoniae infection from the lungs and blood, as compared with similarly infected wild-type animals. The less effective response in wild-type mice seemed to be attributable to impaired production of neutrophil chemoattractants KC (also known as Cxcl1) and Mip2 (also known as Cxcl2) following secondary challenge with S. pneumoniae. This resulted in inadequate neutrophil responses during the early phase of host defense against secondary bacterial infection. Indeed, influenza-infected wild-type mice cleared secondary pneumococcal pneumonia after pulmonary administration of exogenous KC and Mip2, whereas neutralization of Cxcr2, the common receptor for KC and Mip2, reversed the protective phenotype observed in Ifnar-/- mice. These data may underscore the importance of the type I IFN inhibitory pathway on CXC chemokine production. Collectively, these findings highlight what we believe to be a novel mechanism by which the antiviral response to influenza sensitizes hosts to secondary bacterial pneumonia.

Neutrophils are a major component of the innate immune response. Their homeostasis is maintained, in part, by the regulated release of neutrophils from the bone marrow. Constitutive expression of the chemokine CXCL1CXCL1 and CXCL2, and CXCL2 expression was induced in endothelial cells during G-CSF-induced neutrophil mobilization. Collectively, these data suggest that CXCR2 signaling is a second chemokine axis that interacts antagonistically with CXCR4 to regulate neutrophil release from the bone marrow.

Neutrophils are the first to be recruited to a site of infection or a diseased site. Among various inflammatory mediators, CXC chemokines including IL-8 (CXCL8), MIP-2 (CXCL2), and KC (CXCL1) are the most critical for such recruitment. Neutrophils have been considered as effector cells that kill bacteria or destroy affected tissues mainly through the production of reactive oxygen species. Recent studies, however, revealed that neutrophils are involved in the production of chemokines in response to a variety of stimulants including LPS, TNF-alpha, and IFN-gamma, thereby contributing to immunomodulation. These functions are also regulated by selectins during infiltration into various sites. In this review, I summarize the current knowledge on this area and propose that neutrophils are a fascinating target for basic as well as clinical scientists.

Immune suppression increases the incidence of invasive fungal infections, particularly those caused by the opportunistic mold Aspergillus fumigatus. Previous investigations revealed that members of the TLR family are not absolutely required for host defense against A. fumigatus in nonimmunosuppressed hosts, suggesting that other pattern recognition receptors are involved. We show in this study that naive mice (i.e., not pharmacologically immunosuppressed) lacking the beta-glucan receptor Dectin-1 (Dectin-1(-/-)) are more sensitive to intratracheal challenge with A. fumigatus than control mice, exhibiting >80% mortality within 5 days, ultimately attributed to a compromise in respiratory mechanics. In response to A. fumigatus challenge, Dectin-1(-/-) mice demonstrated impaired IL-1alpha, IL-1beta, TNF-alpha, CCL3/MIP-1alpha, CCL4/MIP-1beta, and CXCL1/KC production, which resulted in insufficient lung neutrophil recruitment and uncontrolled A. fumigatus lung growth. Alveolar macrophages from Dectin-1(-/-) mice failed to produce proinflammatory mediators in response to A. fumigatus, whereas neutrophils from Dectin-1(-/-) mice had impaired reactive oxygen species production and impaired killing of A. fumigatus. We further show that IL-17 production in the lung after A. fumigatus challenge was Dectin-1 dependent, and that neutralization of IL-17 significantly impaired A. fumigatus clearance. Collectively, these results support a requisite role for Dectin-1 in in vivo defense against A. fumigatus.

BACKGROUND

T cells play an important role during the immune response that accompanies atherosclerosis. To date, the role for interleukin (IL)-17A in atherogenesis is not well defined. Here, we tested the hypothesis that atherosclerosis-prone conditions induce the differentiation of IL-17A-producing T cells, which in turn promote atherosclerosis.

RESULTS

IL-17A was found to be elevated in the plasma and tissues of apolipoprotein E-deficient (Apoe(-/-)) mice. IL-17A-expressing T cells were significantly increased in the aortas, spleen, and lamina propria of aged Apoe(-/-) mice compared with age-matched C57BL/6 mice. IL-17A(+) T cells resided in both adventitia and aortas of aged Apoe(-/-) mice fed a chow diet. Elevated levels of IL-17A(+) T cells were also detected in the aortas of 21-week-old Apoe(-/-) mice fed a Western diet for 15 weeks. IL-17A(+) T cells were characterized as predominantly CD4(+) T helper 17 (Th17) cells and gammadelta(+) T cells. Blockade of IL-17A in Apoe(-/-) mice by use of adenovirus-produced IL-17 receptor A reduced plaque burden in Apoe(-/-) mice fed a Western diet for 15 weeks. In addition, the treatment diminished circulating IL-6 and granulocyte colony-stimulating factor levels and limited CXCL1 expression and macrophage content within the aortas. Conversely, IL-17A treatment of whole aorta isolated from Apoe(-/-) mice promoted aortic CXCL1 expression and monocyte adhesion in an ex vivo adhesion assay.

CONCLUSIONS

These results demonstrate that atherosclerosis-prone conditions induce the differentiation of IL-17A-producing T cells. IL-17A plays a proatherogenic inflammatory role during atherogenesis by promoting monocyte/macrophage recruitment into the aortic wall.

Mortality related to adult respiratory distress syndrome (ARDS) ranges from 35% to 65%. Lung-protective ventilator strategies can reduce mortality during ARDS. The protective strategies limit tidal volumes and peak pressures while maximizing positive end-expiratory pressure. The efficacy of this approach is due to a reduction of shear-stress of the lung and release of inflammatory mediators. Ventilator-induced lung injury (VILI) is characterized by inflammation. The specific mechanism(s) that recruit leukocytes during VILI have not been elucidated. Because the murine CXC chemokines KC/CXCL1 and MIP-2/CXCL2/3, via CXCR2, are potent neutrophil chemoattractants, we investigated their role in a murine model of VILI. We compared two ventilator strategies in C57BL/6 mice: high peak pressure and high stretch (high peak pressure/stretch) versus low peak pressure/stretch for 6 hours. Lung injury and neutrophil sequestration from the high-peak pressure/stretch group were greater than those from the low-peak pressure/stretch group. In addition, lung expression of KC/CXCL1 and MIP-2/CXCL2/3 paralleled lung injury and neutrophil sequestration. Moreover, in vivo inhibition of CXCR2/CXC chemokine ligand interactions led to a marked reduction in neutrophil sequestration and lung injury. These findings were confirmed using CXCR2(-/-) mice. Together these experiments support the notion that increased expression of KC/CXCL1 and MIP-2/CXCL2/3 and their interaction with CXCR2 are important in the pathogeneses of VILI.

Neutrophil recruitment is an important early step in controlling tissue infections or injury. Here, we report that this influx depends on both tissue-resident mast cells and macrophages. Mice with mast cell deficiency recruit reduced numbers of neutrophils in the first few hours of intraperitoneal lipopolysaccharide (LPS) stimulation. Conversely, in mice with clodronate-ablated macrophages, neutrophils extravasate, but have limited ability to reach the peritoneal fluid. Tissue macrophages synthesize neutrophil chemoattractants CXCL1/CXCL2 (CXC chemokine ligands 1/2) in response to LPS. Mast cells also produce these chemokines of which a proportion are preformed in granules. Release of the granules and new CXCL1/CXCL2 synthesis is Toll-like receptor 4-dependent. Both in vivo studies with blocking monoclonal antibodies and in vitro chemotaxis experiments show the neutrophil response to mast cells and macrophages to be CXCL1/CXCL2-dependent. The data are in keeping with the model that mast cells, optimally positioned in close proximity to the vasculature, initiate an early phase of neutrophil recruitment by releasing the chemoattractants CXCL1/CXCL2. Having arrived within the stimulated tissue, neutrophils penetrate further in a macrophage-dependent manner. Therefore, we demonstrate a positive role for mast cells in tissue inflammation and define how this comes about with contribution from a second tissue cell, the macrophage.

Chronic inflammation of adipose tissue in obesity is by now an established phenomenon, but the initiating event(s) of the inflammatory cascade are still unknown. We hypothesized that neutrophil infiltration into adipose tissue may precede macrophage infiltration as in classical immune responses. Here we demonstrate that early (3 and 7 days) after initiating high-fat feeding of C57BL/6J mice, neutrophils transiently infiltrate the parenchyma of intra-abdominal adipose tissue. Mean periepdidymal fat myeloperoxidase expression (representing neutrophils) was significantly increased 3.5-fold (P < 0.01) and 2.9-fold (P < 0.03), at days 3 and 7 compared with day 0. Immunohistochemistry analysis demonstrated a physical binding between neutrophils and adipocytes, which was supported by in vitro adherence assay: mouse peritoneal neutrophils adhered to a monolayer of 3T3-L1 mouse adipocytes, in a manner dependent on their activation state, 41.9 +/- 3.7% or 29.5 +/- 2%, by PMA or the IL-8 analog CXCL1 (KC), respectively, compared with 24.8 +/- 1.5% in unstimulated neutrophils, respectively. The degree of surface exposure of CD11b (Mac-1) corresponded to the percentage of adhered neutrophils. The adherence was prevented by preincubating neutrophils or adipocytes with anti-CD11b or anti-ICAM-1 antibodies. Furthermore, immunoprecipitation of CD11b from lysates of a mixed neutrophil-adipocyte cell population resulted in coimmunoprecipitation of ICAM-1, indicating that the interaction is mediated by neutrophil CD11b and adipocyte ICAM-1.

In this study, we examined the biological action of IL-17 on human non-small cell lung cancer (NSCLC). Although IL-17 had no direct effect on the in vitro growth rate of NSCLC, IL-17 selectively augmented the secretion of an array of angiogenic CXC chemokines, including CXCL1, CXCL5, CXCL6, and CXCL8 but not angiostatic chemokines, by three different NSCLC lines. Endothelial cell chemotactic activity (as a measure of net angiogenic potential) was increased in response to conditioned medium from NSCLC stimulated with IL-17 compared with those from unstimulated NSCLC. Enhanced chemotactic activity was suppressed by neutralizing mAb(s) to CXCL1, CXCL5, and CXCL8 or to CXCR-2 but not to vascular endothelial growth factor-A. Transfection with IL-17 into NSCLC had no effect on the in vitro growth, whereas IL-17 transfectants grew more rapidly compared with controls when transplanted in SCID mice. This IL-17-elicited enhancement of NSCLC growth was associated with increased tumor vascularity. Moreover, treatment with anti-mouse CXCR-2-neutralizing Ab significantly attenuated the growth of both neomycin phosphotransferase gene-transfected and IL-17-transfected NSCLC tumors in SCID mice. A potential role for IL-17 in modulation of the human NSCLC phenotype was supported by the findings that, in primary NSCLC tissues, IL-17 expression was frequently detected in accumulating and infiltrating inflammatory cells and that high levels of IL-17 expression were associated with increased tumor vascularity. These results demonstrate that IL-17 increases the net angiogenic activity and in vivo growth of NSCLC via promoting CXCR-2-dependent angiogenesis and suggest that targeting CXCR-2 signaling may be a novel promising strategy to treat patients with NSCLC.

To investigate the immune response and mechanisms associated with severe coronavirus disease 2019 (COVID-19), we performed single-cell RNA sequencing on nasopharyngeal and bronchial samples from 19 clinically well-characterized patients with moderate or critical disease and from five healthy controls. We identified airway epithelial cell types and states vulnerable to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In patients with COVID-19, epithelial cells showed an average three-fold increase in expression of the SARS-CoV-2 entry receptor ACE2, which correlated with interferon signals by immune cells. Compared to moderate cases, critical cases exhibited stronger interactions between epithelial and immune cells, as indicated by ligand-receptor expression profiles, and activated immune cells, including inflammatory macrophages expressing CCL2, CCL3, CCL20, <em>CXCL1</em>, CXCL3, <em>CXCL1</em>0, IL8, IL1B and TNF. The transcriptional differences in critical cases compared to moderate cases likely contribute to clinical observations of heightened inflammatory tissue damage, lung injury and respiratory failure. Our data suggest that pharmacologic inhibition of the CCR1 and/or CCR5 pathways might suppress immune hyperactivation in critical COVID-19.

The miR-200 family is well known to inhibit the epithelial-mesenchymal transition, suggesting it may therapeutically inhibit metastatic biology. However, conflicting reports regarding the role of miR-200 in suppressing or promoting metastasis in different cancer types have left unanswered questions. Here we demonstrate a difference in clinical outcome based on miR-200's role in blocking tumour angiogenesis. We demonstrate that miR-200 inhibits angiogenesis through direct and indirect mechanisms by targeting interleukin-8 and CXCL1 secreted by the tumour endothelial and cancer cells. Using several experimental models, we demonstrate the therapeutic potential of miR-200 delivery in ovarian, lung, renal and basal-like breast cancers by inhibiting angiogenesis. Delivery of miR-200 members into the tumour endothelium resulted in marked reductions in metastasis and angiogenesis, and induced vascular normalization. The role of miR-200 in blocking cancer angiogenesis in a cancer-dependent context defines its utility as a potential therapeutic agent.

In models of acute lung injury, CXC chemokine receptor 2 (CXCR2) mediates migration of polymorphonuclear leukocytes (PMNs) into the lung. Since CXCR2 ligands, including CXCL1 and CXCL2/3, are chemotactic for PMNs, CXCR2 is thought to recruit PMNs by inducing chemotactic migration. In a model of PMN recruitment to the lung, aerosolized bacterial LPS inhalation induced PMN recruitment to the lung in wild-type mice, but not in littermate CXCR2-/- mice. Surprisingly, lethally irradiated wild-type mice reconstituted with CXCR2-/- BM still showed about 50% PMN recruitment into bronchoalveolar lavage fluid and into lung interstitium, but CXCR2-/- mice reconstituted with CXCR2-/- BM showed no PMN recruitment. Conversely, CXCR2-/- mice reconstituted with wild-type BM showed a surprisingly large defect in PMN recruitment, inconsistent with a role of CXCR2 on PMNs alone. Cell culture, immunohistochemistry, flow cytometry, and real-time RT-PCR were used to show expression of CXCR2 on pulmonary endothelial and bronchial epithelial cells. The LPS-induced increase in lung microvascular permeability as measured by Evans blue extravasation required CXCR2 on nonhematopoietic cells. Our data revealed what we believe to be a previously unrecognized role of endothelial and epithelial CXCR2 in LPS-induced PMN recruitment and lung injury.

Chemokines and their receptors have crucial roles in the trafficking of leukocytes, and are of particular interest in the context of the unique immune responses elicited in the central nervous system (CNS). The chemokine system CC ligand 2 (CCL2) with its receptor CC receptor 2 (CCR2), as well as the receptor CXCR2 and its multiple ligands CXCL1, CXCL2 and CXCL8, have been implicated in a wide range of neuropathologies, including trauma, ischemic injury and multiple sclerosis. This review aims to overview the current understanding of chemokines as mediators of leukocyte migration into the CNS under neuroinflammatory conditions. We will specifically focus on the involvement of two chemokine networks, namely CCL2/CCR2 and CXCL8/CXCR2, in promoting macrophage and neutrophil infiltration, respectively, into the lesioned parenchyma after focal traumatic brain injury. The constitutive brain expression of these chemokines and their receptors, including their recently identified roles in the modulation of neuroprotection, neurogenesis, and neurotransmission, will be discussed. In conclusion, the value of evidence obtained from the use of Ccl2- and Cxcr2-deficient mice will be reported, in the context of potential therapeutics inhibiting chemokine activity which are currently in clinical trial for various inflammatory diseases.

IL-17 plays an important role in host defense and autoimmunity via the induction of proinflammatory gene expression, particularly in combination with TNF-alpha. The molecular mechanisms by which IL-17 regulates such expression are not well understood. Using the mouse chemokine CXCL1 (KC) gene as a model, we have examined the effects of IL-17 alone or in combination with TNF-alpha on transcriptional and posttranscriptional events. Although treatment of mouse embryonic fibroblasts with IL-17 alone only modestly increased KC expression, the combination of IL-17 with TNF-alpha induced a synergistic response. IL-17 treatment exerted a strong posttranscriptional effect by extending the t1/2 of the highly unstable, TNF-alpha-induced KC mRNA. Using a tetracycline-regulated transgene in HeLa cells, we determined that IL-17 treatment alone promoted stabilization of KC mRNA in the absence of TNF-alpha. IL-17 treatment exerted little effect on KC transcription or NF-kappaB activation, suggesting that it primarily acts posttranscriptionally. We identified a number of other mRNAs whose t1/2 are prolonged in response to IL-17, suggesting that this is a common mechanism by which IL-17 promotes enhanced gene expression. Finally, activator of NF-kappaB1 protein (Act1), an adaptor protein recently implicated in IL-17 signaling, was necessary for IL-17-induced stabilization, and overexpression of Act1 resulted in stabilization of KC mRNA, indicating that events downstream of Act1 are sufficient to initiate this process. Thus, the synergy between TNF-alpha and IL-17 reflects their independent actions on KC gene expression; TNF-alpha serves as a stimulus to initiate transcription through activation of NF-kappaB, whereas IL-17 drives mRNA stabilization through an Act1-dependent pathway.

Chronic inflammation is a well-known risk factor for cancer. Proinflammatory mediators such as prostaglandin E2 (PGE2) promote colorectal tumor growth by stimulating angiogenesis, cell invasion, and cell growth, and inhibiting apoptosis. Molecules that regulate tumor-associated angiogenesis provide promising therapeutic targets for treatment of colorectal cancer (CRC) as indicated by the recent development of the novel anti-angiogenic agent bevacizumab (Avastin). However, use of this drug only prolongs survival by several months, highlighting the importance of finding more effective treatment regimens. We report here that PGE2 induces expression of CXCL1 (growth-regulated oncogene alpha), a pro-angiogenic chemokine, in human CRC cells. More importantly, CXCL1 released from carcinoma cells induces microvascular endothelial cell migration and tube formation in vitro. Furthermore, PGE2 promotes tumor growth in vivo by induction of CXCL1 expression, which results in increased tumor microvessel formation. These results have potential clinical significance because we found that CXCL1 expression correlates with PGE2 levels in human CRCs. Collectively, our findings show for the first time that CXCL1 is regulated by PGE2 and indicate that CXCL1 inhibitors should be evaluated further as potential anti-angiogenic agents for treatment of CRC.

Triple-negative breast cancers (TNBC) are aggressive with no effective targeted therapies. A combined database analysis identified 32 inflammation-related genes differentially expressed in TNBCs and 10 proved critical for anchorage-independent growth. In TNBC cells, an LPA-LPAR2-EZH2 NF-κB signaling cascade was essential for expression of interleukin (IL)-6, IL-8, and CXCL1. Concurrent inhibition of IL-6 and IL-8 expression dramatically inhibited colony formation and cell survival in vitro and stanched tumor engraftment and growth in vivo. A Cox multivariable analysis of patient specimens revealed that IL-6 and IL-8 expression predicted patient survival times. Together these findings offer a rationale for dual inhibition of IL-6/IL-8 signaling as a therapeutic strategy to improve outcomes for patients with TNBCs.

Acute-phase proteins (APPs) are an evolutionarily conserved family of proteins produced mainly in the liver in response to infection and inflammation. Despite vast pro- and antiinflammatory properties ascribed to individual APPs, their collective function during infections remains poorly defined. Using a mouse model of polymicrobial sepsis, we show that abrogation of APP production by hepatocyte-specific gp130 deletion, the signaling receptor shared by IL-6 family cytokines, strongly increased mortality despite normal bacterial clearance. Hepatic gp130 signaling through STAT3 was required to control systemic inflammation. Notably, hepatic gp130-STAT3 activation was also essential for mobilization and tissue accumulation of myeloid-derived suppressor cells (MDSCs), a cell population mainly known for antiinflammatory properties in cancer. MDSCs were critical to regulate innate inflammation, and their adoptive transfer efficiently protected gp130-deficient mice from sepsis-associated mortality. The hepatic APPs serum amyloid A and Cxcl1/KC cooperatively promoted MDSC mobilization, accumulation, and survival, and reversed dysregulated inflammation and restored survival of gp130-deficient mice. Thus, gp130-dependent communication between the liver and MDSCs through APPs controls inflammatory responses during infection.

The fundamental importance of chemokines for atherogenesis, progression, and destabilization of atherosclerotic plaques is now widely appreciated, but the degree of complexity, specificity, and cooperativity harnessed by these signal molecules to govern atherogenic cell recruitment and homeostasis is still being refined. Since the role of chemokines in atherosclerotic vascular disease has been reviewed in this journal, significant progress has been accomplished in defining the regulation of chemokine expression and function in atherosclerosis. In this update, we will highlight these recent developments, in particular the identification of components regulating the transcriptional machinery of the proatherogenic chemokine CCL5, distinct roles of its receptors CCR1 and CCR5 in plaque formation and immunobalance, and differential site- and stage-specific effects of T cell-activating chemokines and their receptors, eg, <em>CXCL1</em>0 and CXCR3. The contribution of the transmembrane chemokines CX(3)CL1 and <em>CXCL1</em>6 with their respective receptors CX(3)CR1 and CXCR6 in the recruitment of T cell and monocyte subsets and shear-mediated plaque modulation will be discussed. Finally, the role of CXCR2 and CXCR4, their respective ligands <em>CXCL1</em> and <em>CXCL1</em>2, and the noncanonical dual agonist MIF in atheroprogression will be dissected. The considerable leap in insight over recent years leads us to anticipate further advances in comprehending the role of chemokines in atherosclerosis, allowing targeted interventions for its prevention and therapy.

Toll-like receptors (TLRs) are pattern recognition receptors that serve an important function in detecting pathogens and initiating inflammatory responses. Upon encounter with foreign Ag, dendritic cells (DCs) go through a maturation process characterized by an increase in surface expression of MHC class II and costimulatory molecules, which leads to initiation of an effective immune response in naive T cells. The innate immune response to bacterial flagellin is mediated by TLR5, which is expressed on human DCs. Therefore, we sought to investigate whether flagellin could induce DC maturation. Immature DCs were cultured in the absence or presence of flagellin and monitored for expression of cell surface maturation markers. Stimulation with flagellin induced increased surface expression of CD83, CD80, CD86, MHC class II, and the lymph node-homing chemokine receptor CCR7. Flagellin stimulated the expression of chemokines active on neutrophils (IL-8/CXC chemokine ligand (CXCL)8, GRO-alpha/<em>CXCL1</em>, GRO-beta/CXCL2, GRO-gamma/CXCL3), monocytes (monocyte chemoattractant protein-1/CC chemokine ligand (CCL)2), and immature DCs (macrophage-inflammatory protein-1 alpha/CCL3, macrophage-inflammatory protein-1 beta/CCL4), but not chemokines active on effector T cells (IFN-inducible protein-10 kDa/<em>CXCL1</em>0, monokine induced by IFN-gamma/CXCL9, IFN-inducible T cell alpha chemoattractant/<em>CXCL1</em>1). However, stimulating DCs with both flagellin and IFN-inducible protein-10 kDa, monokine induced by IFN-gamma, and IFN-inducible T cell alpha chemoattractant expression, whereas stimulation with IFN-beta or flagellin alone failed to induce these chemokines. In functional assays, flagellin-matured DCs displayed enhanced T cell stimulatory activity with a concomitant decrease in endocytic activity. Finally, DCs isolated from mouse spleens or bone marrows were shown to not express TLR5 and were not responsive to flagellin stimulation. These results demonstrate that flagellin can directly stimulate human but not murine DC maturation, providing an additional mechanism by which motile bacteria can initiate an acquired immune response.