RNA-Binding Proteins as a Molecular Link between COPD and Lung Cancer

Chronic obstructive pulmonary disease (COPD) represents an independent risk factor for lung cancer development. Accelerated cell senescence, induced by oxidative stress and inflammation, is a common pathogenic determinant of both COPD and lung cancer. The post transcriptional regulation of genes involved in these processes is finely regulated by RNA-binding proteins (RBPs), which regulate mRNA turnover, subcellular localization, splicing and translation. Multiple pro-inflammatory mediators (including cytokines, chemokines, proteins, growth factors and others), responsible of lung microenvironment alteration, are regulated by RBPs. Several mouse models have shown the implication of RBPs in multiple mechanisms that sustain chronic inflammation and neoplastic transformation. However, further studies are required to clarify the role of RBPs in the pathogenic mechanisms shared by lung cancer and COPD, in order to identify novel biomarkers and therapeutic targets. This review will therefore focus on the studies collectively indicating the role of RBPs in oxidative stress and chronic inflammation as common pathogenic mechanisms shared by lung cancer and COPD.

Pulmonary Inflammatory Response in Lethal COVID-19 Reveals Potential Therapeutic Targets and Drugs in Phases III/IV Clinical Trials

Background: It is imperative to identify drugs that allow treating symptoms of severe COVID-19. Respiratory failure is the main cause of death in severe COVID-19 patients, and the host inflammatory response at the lungs remains poorly understood.

Methods: Therefore, we retrieved data from post-mortem lungs from COVID-19 patients and performed in-depth in silico analyses of single-nucleus RNA sequencing data, inflammatory protein interactome network, and shortest pathways to physiological phenotypes to reveal potential therapeutic targets and drugs in advanced-stage COVID-19 clinical trials.

Results: Herein, we analyzed transcriptomics data of 719 inflammatory response genes across 19 cell types (116,313 nuclei) from lung autopsies. The functional enrichment analysis of the 233 significantly expressed genes showed that the most relevant biological annotations were inflammatory response, innate immune response, cytokine production, interferon production, macrophage activation, blood coagulation, NLRP3 inflammasome complex, and the TLR, JAK-STAT, NF-κB, TNF, oncostatin M signaling pathways. Subsequently, we identified 34 essential inflammatory proteins with both high-confidence protein interactions and shortest pathways to inflammation, cell death, glycolysis, and angiogenesis.

Conclusion: We propose three small molecules (baricitinib, eritoran, and montelukast) that can be considered for treating severe COVID-19 symptoms after being thoroughly evaluated in COVID-19 clinical trials.

Exploring the oncostatin M (OSM) feed-forward signaling of glioblastoma via STAT3 in pan-cancer analysis

Background

Oncostatin M (OSM) has been reported to be a key regulating factor in the process of tumor development. Previous studies have demonstrated both the promotion and inhibition effects of OSM in tumors, therefore inspiring controversies. However, no systematic assessment of OSM across various cancers is available, and the mechanisms behind OSM-related cancer progression remain to be elucidated.

Methods

Based on The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) databases, we conducted a pan-cancer analysis on OSM to explore its tumor-related functions across cancers as well as its correlations with specific molecules, cells in the tumor microenvironment. Considering the results of pan-cancer analysis, we chose the specific tumor glioblastoma multiforme (GBM) to screen out the OSM-induced signaling pathways and intercellular communications in tumor progression. Wound scratch assay, invasion assay and qRT-PCR were performed to verify the biological effects of OSM on glioblastoma cells.

Results

Higher OSM level was found in most tumor tissues compared with corresponding normal tissues, and the enhanced OSM expression was observed to be strongly related to patients’ poor prognosis in several cancers. Moreover, the expression of OSM was associated with stromal and immune cell infiltration in the tumor microenvironment, and OSM-related immune checkpoint and chemokine co-expression were also observed. Our results suggested that OSM could communicate extensively with the tumor microenvironment. Taking GBM as an example, our study found that two critical signaling pathways in OSM-related tumor progression by KEGG enrichment analysis: Jak-STAT and NF-κB pathways. Single-cell RNA sequencing data analysis of GBM revealed that OSM was mainly secreted by microglia, and cell–cell interaction analysis proved that OSM-OSMR is an important pathway for OSM to stimulate malignant cells. In vitro, OSM treatment could facilitate the migration and invasion of glioblastoma cells, meanwhile promote the proneural-mesenchymal transition. The administration of STAT3 inhibitors effectively suppressed the OSM-mediated biological effects, which proved the key role of STAT3 in OSM signaling.

Conclusion

Taken together, our study provides a comprehensive understanding with regard to the tumor progression under the regulation of OSM. OSM seems to be closely related to chronic inflammation and tumor development in the tumor microenvironment. As an important inflammatory factor in the tumor microenvironment, OSM may serve as a potential immunotherapeutic target for cancer treatment, especially for GBM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02260-9.

Anti-CCL22 increases regulatory T cells in CD4+ T cells of rheumatoid arthritis patients via STAT5 pathway

Abnormality in the number and function of CD4⁺CD25⁺FOXP3⁺ regulatory T cells (Tregs) in peripheral blood has been linked to the initiation and progression of rheumatoid arthritis (RA). Effect of chemokine CCL22 on the number of Tregs in CD4⁺ T cells and the underlying mechanism were investigated. Downregulation of peripheral Tregs were observed while upregulation of serum chemokine CCL22 in RA patients. Tregs count and the expression of FOXP3 (Tregs function-related maker) and phosphorylated-signal transducer and activator of transcription 5 (p-STAT5) in CD4⁺ T cells from RA patients were increased while C-C chemokine receptor 4 (CCR4) was decreased by anti-CCL22 antibody, however, recombinant CCL22 resulted in the opposite effects in CD4⁺ T cells from the healthy control. STAT5 inhibitor significantly reversed the effects of anti-CCL22 antibody. Similarly, sinomenine, an anti-arthritis drug, which decreased CCL22 and CCR4, showed the same trends as the above events, and was reversed by recombinant CCL22 or STAT5 inhibitor. Collectively, anti-CCL22 induced the number of Tregs via STAT5 pathway, leading to expansion of Tregs and subsequently to control of the autoimmune reaction in RA patients. Our study provides s novel strategy for RA treatment.

A Subset of TREM2+ Dermal Macrophages Secretes Oncostatin M to Maintain Hair Follicle Stem Cell Quiescence and Inhibit Hair Growth

Hair growth can be induced from resting mouse hair follicles by topical application of JAK inhibitors, suggesting that JAK-STAT signaling is required for maintaining hair follicle stem cells (HFSCs) in a quiescent state. Here, we show that Oncostatin M (OSM), an IL-6 family cytokine, negatively regulates hair growth by signaling through JAK-STAT5 to maintain HFSC quiescence. Genetic deletion of the OSM receptor or STAT5 can induce premature HFSC activation, suggesting that the resting telogen stage is actively maintained by the hair follicle niche. Single-cell RNA sequencing revealed that the OSM source is not intrinsic to the hair follicle itself and is instead a subset of TREM2⁺ macrophages that is enriched within the resting follicle and deceases immediately prior to HFSC activation. In vivo inhibition of macrophage function was sufficient to induce HFSC proliferation and hair cycle induction. Together these results clarify how JAK-STAT signaling actively inhibits hair growth.

MiR-345-5p functions as a tumor suppressor in pancreatic cancer by directly targeting CCL8

BACKGROUND

Increasing evidence has demonstrated that microRNAs (miRNAs) are key regulators of human diseases and can serve as prognostic markers for several cancers, such as pancreatic ductal adenocarcinoma (PDAC). Previous studies have revealed various functions for miR-345-5p in several cancers. However, the role and potential mechanism of miR-345-5p in PDAC have not been resolved.

METHODS

Quantitative RT-PCR was performed to investigate the expression levels of miR-345-5p in pancreatic cancer tissues and cell lines, and the effect of miR-345-5p on the proliferation and invasiveness of pancreatic cancer was examined in Transwell assays with miR-345-5p overexpression. We used Western blot assay to explore the underlying mechanisms. Immunofluorescence staining was performed to examine changes in the cytoskeleton of PANC-1 cells in response to miR-345-5p. Luciferase assays were used to clarify the target and regulation mechanism of miR-345-5p.

RESULTS

miR-345-5p expression was downregulated in PDAC cells and tissues. Upregulated miR-345-5p expression inhibited the proliferation and metastasis of PDAC cells. We identified CCL8 as a direct target of miR-345-5p and found CCL8 expression was inversely correlated with miR-345-5p expression in PDAC samples. CCL8 could activate the NF-κB signaling pathway to promote the proliferation and invasiveness of PDAC cells. These results suggested that miR-345-5p inhibited PDAC progression by inactivating NF-κB signaling.

CONCLUSIONS

Here we demonstrated that miR-345-5p was a tumor-suppressive miRNA in pancreatic cancer progression by targeting CCL8. Our results suggest miR-345-5p may be a potential therapeutic biomarker for pancreatic cancer treatment.

Oncostatin M Suppresses Activation of IL-17/Th17 via SOCS3 Regulation in CD4+ T Cells

Oncostatin M (OSM) is a pleiotropic cytokine and a member of the IL-6 family. It has both proinflammatory and anti-inflammatory functions and is involved in the activation of STAT3 and STAT5. Rheumatoid arthritis is an autoimmune disease that causes chronic and excessive inflammation. Rheumatoid arthritis can lead to induction of Th17 cells, which express IL-17. The aim of this study was to measure the effects of OSM on the proliferation of regulatory T cells and Th17 cells from mice. IL-2 immune complex suppressed the development of collagen-induced arthritis in mice and altered the regulatory T/Th17 cell balance by increasing OSM expression. OSM mitigated the proliferation of Th17 cells and decreased the expression of IL-17 and IL-21. It promoted the activation of suppressor of cytokine signaling 3 (SOCS3), STAT3, and STAT5. Inhibition of SOCS3, STAT3, and STAT5 lessened the OSM-induced reduction in proliferation of Th17 cells. These observations suggest that OSM can inhibit Th17 differentiation by reciprocally controlling SOCS3, STAT3, and STAT5.

The PI3K inhibitor taselisib overcomes letrozole resistance in a breast cancer model expressing aromatase

Letrozole is a commonly used treatment option for metastatic hormone receptor-positive (HR+) breast cancer, but many patients ultimately relapse. Due to the importance of phosphoinositide-3 kinase (PI3K) in breast cancer, PI3K inhibitors such as taselisib are attractive for combination with endocrine therapies such as letrozole. Taselisib was evaluated as a single agent and in combination with letrozole in a breast cancer cell line engineered to express aromatase. The combination of taselisib and letrozole decreased cellular viability and increased apoptosis relative to either single agent. Signaling cross-talk between the PI3K and ER pathways was associated with efficacy for the combination. In a secreted factor screen, multiple soluble factors, including members of the epidermal and fibroblast growth factor families, rendered breast cancer cells non-responsive to letrozole. It was discovered that many of these factors signal through the PI3K pathway and cells remained sensitive to taselisib in the presence of the soluble factors. We also found that letrozole resistant lines have elevated PI3K pathway signaling due to an increased level of p110α, but are still sensitive to taselisib. These data provide rationale for clinical evaluation of PI3K inhibitors to overcome resistance to endocrine therapies in ER+ breast cancer.

Oncostatin M overexpression induces skin inflammation but is not required in the mouse model of imiquimod-induced psoriasis-like inflammation

Oncostatin M (OSM) has been reported to be overexpressed in psoriasis skin lesions and to exert proinflammatory effects in vitro on human keratinocytes. Here, we report the proinflammatory role of OSM in vivo in a mouse model of skin inflammation induced by intradermal injection of murine OSM-encoding adenovirus (AdOSM) and compare with that induced by IL-6 injection. Here, we show that OSM potently regulates the expression of genes involved in skin inflammation and epidermal differentiation in murine primary keratinocytes. In vivo, intradermal injection of AdOSM in mouse ears provoked robust skin inflammation with epidermal thickening and keratinocyte proliferation, while minimal effect was observed after AdIL-6 injection. OSM overexpression in the skin increased the expression of the S100A8/9 antimicrobial peptides, CXCL3, CCL2, CCL5, CCL20, and Th1/Th2 cytokines, in correlation with neutrophil and macrophage infiltration. In contrast, OSM downregulated the expression of epidermal differentiation genes, such as cytokeratin-10 or filaggrin. Collectively, these results support the proinflammatory role of OSM when it is overexpressed in the skin. However, OSM expression was not required in the murine model of psoriasis induced by topical application of imiquimod, as demonstrated by the inflammatory phenotype of OSM-deficient mice or wild-type mice treated with anti-OSM antibodies.

Signal transducer and activator of transcription 5 is implicated in disease activity in adult and juvenile onset systemic lupus erythematosus

The Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway is one of a handful of pleiotropic cascades used to transduce a multitude of signals for development and homeostasis in humans. It is the principal signaling mechanism for a wide array of cytokines and growth factors. Dysregulated cytokine action on immune cells plays an important role in the initiation and progress of systemic lupus erythematosus (SLE). In this study, we tried to assess the role of STAT5 in systemic lupus erythematosus and correlate its phosphorylation level with the disease activity. The activation of the STAT5 was assessed by measuring the level of expression of phosphorylated STAT5 (pSTAT5) using flow cytometry on the peripheral blood T and B cells in 58 SLE patients (40 adult and 18 juvenile onset) and on 23 healthy age- and sex-matched controls for both groups. Serum prolactin level was also assessed in the patients and control by ELISA. The study revealed that the level of pSTAT5 was higher in adult SLE patients than in healthy control (p = 0.001) and in juvenile-onset SLE patients versus age-matched control (p = 0.031). A positive correlation existed between the pSTAT5 levels and Systemic Lupus Activity Measure (SLAM) score and also with multiple clinical manifestations indicating a potential role of STAT5 signaling in pathogenesis SLE. The pSTAT5 signaling is implicated in the disease activity of SLE and may be a useful target of therapy by correcting the dysregulation of cytokines involved in the disease pathogenesis.

CCL8 and the Immune Control of Cytomegalovirus in Organ Transplant Recipients

Monitoring of cytomegalovirus cell-mediated immunity is a promising tool for the refinement of preventative and therapeutic strategies posttransplantation. Typically, the interferon-γ response to T cell stimulation is measured. We evaluated a broad range of cytokine and chemokines to better characterize the ex vivo host-response to CMV peptide stimulation. In a cohort of CMV viremic organ transplant recipients, chemokine expression-specifically CCL8 (AUC 0.849 95% CI 0.721-0.978; p = 0.003) and CXCL10 (AUC 0.841, 95% CI 0.707-0.974; p = 0.004)-was associated with control of viral replication. In a second cohort of transplant recipients at high-risk for CMV, the presence of a polymorphism in the CCL8 promoter conferred an increased risk of viral replication after discontinuation of antiviral prophylaxis (logrank hazard ratio 3.6; 95% CI 2.077-51.88). Using cell-sorting experiments, we determined that the primary cell type producing CCL8 in response to CMV peptide stimulation was the monocyte fraction. Finally, in vitro experiments using standard immunosuppressive agents demonstrated a dose-dependent reduction in CCL8 production. Chemokines appear to be important elements of the cell-mediated response to CMV infection posttransplant, as here suggested for CCL8, and translation of this knowledge may allow for the tailoring and improvement of preventative strategies.

Myocardial healing requires Reg3β-dependent accumulation of macrophages in the ischemic heart

Cardiac healing after myocardial ischemia depends on the recruitment and local expansion of myeloid cells, particularly macrophages. Here we identify Reg3β as an essential regulator of macrophage trafficking to the damaged heart. Using mass spectrometry-based secretome analysis, we found that dedifferentiating cardiomyocytes release Reg3β in response to the cytokine OSM, which signals through Jak1 and Stat3. Loss of Reg3β led to a large decrease in the number of macrophages in the ischemic heart, accompanied by increased ventricular dilatation and insufficient removal of neutrophils. This defect in neutrophil removal in turn caused enhanced matrix degradation, delayed collagen deposition and increased susceptibility to cardiac rupture. Our data indicate that OSM, acting through distinct intracellular pathways, regulates both cardiomyocyte dedifferentiation and cardiomyocyte-dependent regulation of macrophage trafficking. Release of OSM from infiltrating neutrophils and macrophages initiates a positive feedback loop in which OSM-induced production of Reg3β in cardiomyocytes attracts additional OSM-secreting macrophages. The activity of the feedback loop controls the degree of macrophage accumulation in the heart, which is instrumental in myocardial healing.

The enigmatic cytokine oncostatin m and roles in disease

Oncostatin M is a secreted cytokine involved in homeostasis and in diseases involving chronic inflammation. It is a member of the gp130 family of cytokines that have pleiotropic functions in differentiation, cell proliferation, and hematopoetic, immunologic, and inflammatory networks. However, Oncostatin M also has activities novel to mediators of this cytokine family and others and may have fundamental roles in mechanisms of inflammation in pathology. Studies have explored Oncostatin M functions in cancer, bone metabolism, liver regeneration, and conditions with chronic inflammation including rheumatoid arthritis, lung and skin inflammatory disease, atherosclerosis, and cardiovascular disease. This paper will review Oncostatin M biology in a historical fashion and focus on its unique activities, in vitro and in vivo, that differentiate it from other cytokines and inspire further study or consideration in therapeutic approaches.

JAK2 mutants (e.g., JAK2V617F) and their importance as drug targets in myeloproliferative neoplasms

The Janus kinase 2 (JAK2) mutant V617F and other JAK mutants are found in patients with myeloproliferative neoplasms and leukemias. Due to their involvement in neoplasia and inflammatory disorders, Janus kinases are promising targets for kinase inhibitor therapy. Several small-molecule compounds are evaluated in clinical trials for myelofibrosis, and ruxolitinib (INCB018424, Jakafi®) was the first Janus kinase inhibitor to receive clinical approval. In this review we provide an overview of JAK2V617F signaling and its inhibition by small-molecule kinase inhibitors. In addition, myeloproliferative neoplasms are discussed regarding the role of JAK2V617F and other mutant proteins of possible relevance. We further give an overview about treatment options with special emphasis on possible combination therapies.

Pulmonary expression of oncostatin M (OSM) promotes inducible BALT formation independently of IL-6, despite a role for IL-6 in OSM-driven pulmonary inflammation

Inducible BALT (iBALT) is associated with immune responses to respiratory infections as well as with local pathology derived from chronic inflammatory lung diseases. In this study, we assessed the role of oncostatin M (OSM) in B cell activation and iBALT formation in mouse lungs. We found that C57BL/6 mice responded to an endotracheally administered adenovirus vector expressing mouse OSM, with marked iBALT formation, increased cytokine (IL-4, IL-5, IL-6, IL-10, TNF-α, and IL-12), and chemokine (CXCL13, CCL20, CCL21, eotaxin-2, KC, and MCP-1) production as well as inflammatory cell accumulation in the airways. B cells, T cells, and dendritic cells were also recruited to the lung, where many displayed an activated phenotype. Mice treated with control adenovirus vector (Addl70) were not affected. Interestingly, IL-6 was required for inflammatory responses in the airways and for the expression of most cytokines and chemokines. However, iBALT formation and lymphocyte recruitment to the lung tissue occurred independently of IL-6 and STAT6 as assessed in gene-deficient mice. Collectively, these results support the ability of OSM to induce B cell activation and iBALT formation independently of IL-6 and highlight a role for IL-6 downstream of OSM in the induction of pulmonary inflammation.

Scrambled and fried: cigarette smoke exposure causes antral follicle destruction and oocyte dysfunction through oxidative stress

Cigarette smoke is a reproductive hazard associated with pre-mature reproductive senescence and reduced clinical pregnancy rates in female smokers. Despite an increased awareness of the adverse effects of cigarette smoke exposure on systemic health, many women remain unaware of the adverse effects of cigarette smoke on female fertility. This issue is compounded by our limited understanding of the molecular mechanisms behind cigarette smoke induced infertility. In this study we used a direct nasal exposure mouse model of cigarette smoke-induced chronic obstructive pulmonary disease to characterise mechanisms of cigarette-smoke induced ovotoxicity. Cigarette smoke exposure caused increased levels of primordial follicle depletion, antral follicle oocyte apoptosis and oxidative stress in exposed ovaries, resulting in fewer follicles available for ovulation. Evidence of oxidative stress also persisted in ovulated oocytes which escaped destruction, with increased levels of mitochondrial ROS and lipid peroxidation resulting in reduced fertilisation potential. Microarray analysis of ovarian tissue correlated these insults with a complex mechanism of ovotoxicity involving genes associated with detoxification, inflammation, follicular activation, immune cell mediated apoptosis and membrane organisation. In particular, the phase I detoxifying enzyme cyp2e1 was found to be significantly up-regulated in developing oocytes; an enzyme known to cause molecular bioactivation resulting in oxidative stress. Our results provide a preliminary model of cigarette smoke induced sub-fertility through cyp2e1 bioactivation and oxidative stress, resulting in developing follicle depletion and oocyte dysfunction.

Characterization of the rat oncostatin M receptor complex which resembles the human, but differs from the murine cytokine receptor

Evaluation of a pathophysiological role of the interleukin-6-type cytokine oncostatin M (OSM) for human diseases has been complicated by the fact that mouse models of diseases targeting either OSM or the OSM receptor (OSMR) complex cannot fully reflect the human situation. This is due to earlier findings that human OSM utilizes two receptor complexes, glycoprotein 130 (gp130)/leukemia inhibitory factor receptor (LIFR) (type I) and gp130/OSMR (type II), both with wide expression profiles. Murine OSM on the other hand only binds to the gp130/OSMR (type II) receptor complex with high affinity. Here, we characterize the receptor usage for rat OSM. Using different experimental approaches (knock-down of the OSMR expression by RNA interference, blocking of the LIFR by LIF-05, an antagonistic LIF variant and stably transfected Ba/F3 cells) we can clearly show that rat OSM surprisingly utilizes both, the type I and type II receptor complex, therefore mimicking the human situation. Furthermore, it displays cross-species activities and stimulates cells of human as well as murine origin. Its signaling capacities closely mimic those of human OSM in cell types of different origin in the way that strong activation of the Jak/STAT, the MAP kinase as well as the PI3K/Akt pathways can be observed. Therefore, rat disease models would allow evaluation of the relevance of OSM for human biology.

Primate-specific microRNA-637 inhibits tumorigenesis in hepatocellular carcinoma by disrupting signal transducer and activator of transcription 3 signaling

MiR-637 (microRNA-637) is a primate-specific miRNA belonging to the small noncoding RNA family, which represses gene regulation at the post-transcriptional expression level. Although it was discovered approximately 5 years ago, its biomedical significance and regulatory mechanism remain obscure. Our preliminary data showed that miR-637 was significantly suppressed in four HCC cell lines and, also, in most of the hepatocellular carcinoma (HCC) specimens, thereby suggesting that miR-637 would be a tumor suppressor in HCC. Simultaneously, the enforced overexpression of miR-637 dramatically inhibited cell growth and induced the apoptosis of HCC cells. The transcription factor, signal transducer and activator of transcription 3 (Stat3), is constitutively activated in multiple tumors, and aberrant Stat3 activation is linked to the promotion of growth and desensitization of apoptosis. Our study showed that Stat3 tyrosine 705 phosphorylation and several Stat3-regulated antiapoptotic genes were down-regulated in miR-637 mimics-transfected and Lv-miR637-infected HCC cells. In addition, miR-637 overexpression negatively regulated Stat3 phosphorylation by suppressing autocrine leukemia inhibitory factor (LIF) expression and exogenous LIF-triggered Stat3 activation and rescued cell growth in these cells. A nude mice model also demonstrated the above-described results, which were obtained from the cell model. Furthermore, we found that LIF was highly expressed in a large proportion of HCC specimens, and its expression was inversely associated with miR-637 expression.

CONCLUSION

Our data indicate that miR-637 acted as a tumor suppressor in HCC, and the suppressive effect was mediated, at least in part, by the disruption of Stat3 activation.

The human cutaneous chemokine system

Irrespective of the immune status, the vast majority of all lymphocytes reside in peripheral tissues whereas those present in blood only amount to a small fraction of the total. It has been estimated that T cells in healthy human skin outnumber those present in blood by at least a factor of two. How lymphocytes within these two compartments relate to each other is not well understood. However, mounting evidence suggest that the study of T cell subsets present in peripheral blood does not reflect the function of their counterparts at peripheral sites. This is especially true under steady-state conditions whereby long-lived memory T cells in healthy tissues, notably those in epithelial tissues at body surfaces, are thought to fulfill a critical immune surveillance function by contributing to the first line of defense against a series of local threats, including microbes, tumors, and toxins, and by participating in wound healing. The relative scarcity of information regarding peripheral T cells and the factors regulating their localization is primarily due to inherent difficulties in obtaining healthy tissue for the extraction and study of immune cells on a routine basis. This is most certainly true for humans. Here, we review our current understanding of T cell homing to human skin and compare it when possible with gut-selective homing. We also discuss candidate chemokines that may account for the tissue selectivity in this process and present a model whereby CCR8, and its ligand CCL1, selectively regulate the homeostatic migration of memory lymphocytes to skin tissue.

Alkylation of cysteine 468 in Stat3 defines a novel site for therapeutic development

Stat3 is a latent transcription factor that promotes cell survival and proliferation and is often constitutively active in multiple cancers. Inhibition of Stat3 signaling pathways suppresses cell survival signals and leads to apoptosis in cancer cells, suggesting direct inhibition of Stat3 function is a viable therapeutic approach. Herein, we identify a small molecule, C48, as a selective Stat3-family member inhibitor. To determine its mechanism of action, we used site-directed mutagenesis and multiple biochemical techniques to show that C48 alkylates Cys468 in Stat3, a residue at the DNA-binding interface. We further demonstrate that C48 blocks accumulation of activated Stat3 in the nucleus in tumor cell lines that overexpress active Stat3, leading to impressive inhibition of tumor growth in mouse models. Collectively, these findings suggest Cys468 in Stat3 represents a novel site for therapeutic intervention and demonstrates the promise of alkylation as a potentially effective chemical approach for Stat3-dependent cancers.

A receptor fusion protein for the inhibition of murine oncostatin M

Background

Most cytokines signal through heteromeric receptor complexes consisting of two or more different receptor subunits. Fusion proteins of the extracellular parts of receptor subunits turned out to be promising cytokine inhibitors useful in anti-cytokine therapy and cytokine research.

Results

We constructed receptor fusion proteins (RFP) consisting of the ligand binding domains of the murine oncostatin M (mOSM) receptor subunits mOSMR and mgp130 connected by a flexible linker as potential mOSM inhibitors. mgp130 is a shared cytokine receptor that is also used by other cytokines such as IL-6 and leukemia inhibitory factor (LIF). In this study we compare four types of mOSM-RFPs that contain either domains D1-D3 or domains D2-D3 of mgp130 and are arranged in two ways. Domain D1 of mgp130 turned out to be dispensable for mOSM-binding. However, the arrangement of the two receptor subunits is essential for the inhibitory activity. We found mOSM induced STAT3 phosphorylation to be suppressed only when the mOSMR fragment was fused in front of the mgp130 fragment.

Conclusions

mOSM-RFP consisting of D1-D4 of mOSMR and D2-D3 of mgp130 is a highly potent and specific inhibitor of mOSM. Since mOSM-RFP is encoded by a single gene it offers numerous possibilities for specific cytokine inhibition in gene delivery approaches based on viral vectors, transgenic animals and finally gene therapy.

Perspectives for the use of structural information and chemical genetics to develop inhibitors of Janus kinases

Gain-of-function mutations in the genes encoding Janus kinases have been discovered in various haematologic diseases. Jaks are composed of a FERM domain, an SH2 domain, a pseudokinase domain and a kinase domain, and a complex interplay of the Jak domains is involved in regulation of catalytic activity and association to cytokine receptors. Most activating mutations are found in the pseudokinase domain. Here we present recently discovered mutations in the context of our structural models of the respective domains. We describe two structural hotspots in the pseudokinase domain of Jak2 that seem to be associated either to myeloproliferation or to lymphoblastic leukaemia, pointing at the involvement of distinct signalling complexes in these disease settings. The different domains of Jaks are discussed as potential drug targets. We present currently available inhibitors targeting Jaks and indicate structural differences in the kinase domains of the different Jaks that may be exploited in the development of specific inhibitors. Moreover, we discuss recent chemical genetic approaches which can be applied to Jaks to better understand the role of these kinases in their biological settings and as drug targets.

Signal transduction--receptors, mediators, and genes

The 2008 annual meeting of the Signal Transduction Society covered a broad spectrum of topics, with signaling in immune cells as the special focus of the meeting. Many of the immune signaling talks concerned B and T lymphocytes in particular; the role of inflammatory cytokines in cancer progression was also addressed. Neoplastic development was also discussed with regard to aspects of cell cycle control, aging, and transformation. Topics extended to signaling pathways induced by bacteria, viruses, and environmental toxins, as well as those involved in differentiation, morphogenesis, and cell death. This international and interdisciplinary scientific gathering induced lively discussions and close interactions between participants.