Role Of Spleen Tyrosine Kinase Research Articles

A pathological study on the efficacy of Syk inhibitors in a Candida albicans-induced aortic root vasculitis murine model

BackgroundThe activation of innate immunity may be involved in the development of Candida albicans-induced murine vasculitis, which resembles Kawasaki disease (KD) vasculitis. This study aimed to histologically clarify the time course of the development of vasculitis in this model in detail and to estimate the potential role of spleen tyrosine kinase (Syk) inhibitors in KD vasculitis. Methods and ResultsDBA/2 male mice were intraperitoneally injected with a vasculitis-inducing substance and treated with a Syk inhibitor (R788 or GS-9973). Systemic vasculitis, especially in the aortic annulus area, was histologically evaluated. Regarding lesions in the aortic annulus area, some mice in the untreated control group already showed initiation of vasculitis 1 day after the final injection of a vasculitis-inducing substance. The vasculitis expanded over time. Inflammation occurred more frequently at the aortic root than at the coronary artery. The distribution of inflammatory cells was limited to the intima, intima plus adventitia, or all layers. In the Syk inhibitor-treated groups, only one mouse had vasculitis at all observation periods. The severity and area of the vasculitis were reduced by both Syk inhibitors. ConclusionCandida albicans-induced murine vasculitis may occur within 1 day after the injection of a vasculitis-inducing substance. Additionally, Syk inhibitors suppress murine vasculitis.

Spleen tyrosine kinase inhibitor R406 has both antiviral and anti-inflammatory effects on severe influenza A infection.

Death due to severe influenza is usually a fatal complication of a dysregulated immune response more than the acute virulence of an infectious agent. Although spleen tyrosine kinase (SYK) as a critical immune signaling molecule and therapeutic target plays roles in airway inflammation and acute lung injury, the role of SYK in influenza virus infection is not clear. Here, we investigated the antiviral and anti-inflammatory effects of SYK inhibitor R406 on influenza infection through a coculture model of human alveolar epithelial (A549) and macrophage (THP-1) cell lines and mouse model. The results showed that R406 treatment increased the viability of A549 and decreased the pathogenicity and mortality of lethal influenza virus in mice with influenza A infection, decreased levels of intracellular signaling molecules under the condition of inflammation during influenza virus infection. Combination therapy with oseltamivir further ameliorated histopathological damage in the lungs of mice and further delayed the initial time to death compared with R406 treatment alone. This study demonstrated that phosphorylation of SYK is involved in the pathogenesis of influenza, and R406 has antiviral and anti-inflammatory effects on the treatment of the disease, which may be realized through multiple pathways, including the already reported SYK/STAT/IFNs-mediated antiviral pathway, as well as TNF-α/SYK- and SYK/Akt-based immunomodulation pathway.

Immunomodulatory role of spleen tyrosine kinase in chronic inflammatory and autoimmune diseases.

The high prevalence of chronic inflammatory diseases or autoimmune reactions is a major source of concern and affects the quality of life of patients. Chronic inflammatory or autoimmune diseases are associated with many diseases in humans, including asthma, rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease and cancer. Splenic tyrosine kinase (SYK) is a non-receptor tyrosine kinase that plays an important role in immune receptor signalling in immune and inflammatory responses. This is a review article in which we searched for keywords "splenic tyrosine kinase", "inflammation" and "autoimmune diseases" in published literature such as Pubmed and Web of Science to collect relevant information and then conducted a study focusing on the latest findings on the involvement of SYK in chronic inflammatory or autoimmune diseases. This paper reviews the regulation of Fcγ, NF-κB, B cell and T cell-related signalling pathways by SYK, which contributes to disease progression in chronic inflammatory and autoimmune diseases such as airway fibrosis, inflammatory skin disease and inflammatory bowel disease. This paper shows that SYK plays an important role in chronic inflammatory and autoimmune diseases. syk targets hematological, autoimmune and other inflammatory diseases and therefore, inhibition of SYK expression or blocking its related pathways may provide new ideas for clinical prevention and treatment of inflammatory or autoimmune diseases.

Inhibition of spleen tyrosine kinase decreases donor specific antibody levels in a rat model of sensitization

Antibody mediated rejection is a major cause of renal allograft loss. Circulating preformed donor specific antibodies (DSA) can result as a consequence of blood transfusion, pregnancy or prior transplantation. Current treatment strategies are limited due to partial or transient efficacy, adverse side-effects or patient unsuitability. Previous in vivo studies exploring autoimmune diseases have shown that spleen tyrosine kinase (SYK) signalling is involved in the development of pathogenic autoantibody. The role of SYK in allogenic antibody production is unknown, and we investigated this in a rodent model of sensitization, established by the transfusion of F344 whole blood into LEW rats. Two-week treatment of sensitized rats with selective SYK inhibitor fostamatinib strongly blocked circulating DSA production without affecting overall total immunoglobulin levels, and inhibition was sustained up to 5 weeks post-completion of the treatment regimen. Fostamatinib treatment did not affect mature B cell subset or plasma cell levels, which remained similar between non-treated controls, vehicle treated and fostamatinib treated animals. Our data indicate fostamatinib may provide an alternative therapeutic option for patients who are at risk of sensitization following blood transfusion while awaiting renal transplant.

Role of spleen tyrosine kinase in liver diseases.

Spleen tyrosine kinase (SYK) is a non-receptor tyrosine kinase expressed in most hematopoietic cells and non-hematopoietic cells and play a crucial role in both immune and non-immune biological responses. SYK mediate diverse cellular responses via an immune-receptor tyrosine-based activation motifs (ITAMs)-dependent signalling pathways, ITAMs-independent and ITAMs-semi-dependent signalling pathways. In liver, SYK expression has been observed in parenchymal (hepatocytes) and non-parenchymal cells (hepatic stellate cells and Kupffer cells), and found to be positively correlated with the disease severity. The implication of SYK pathway has been reported in different liver diseases including liver fibrosis, viral hepatitis, alcoholic liver disease, non-alcoholic steatohepatitis and hepatocellular carcinoma. Antagonism of SYK pathway using kinase inhibitors have shown to attenuate the progression of liver diseases thereby suggesting SYK as a highly promising therapeutic target. This review summarizes the current understanding of SYK and its therapeutic implication in liver diseases.

Spleen tyrosine kinase inhibition is an effective treatment for established vasculitis in a pre-clinical model

The anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitides (AAV) are a group of life-threatening multi-system diseases characterized by necrotising inflammation of small blood vessels and crescentic glomerulonephritis. ANCA are thought to play a direct pathogenic role. Previous studies have shown that spleen tyrosine kinase (SYK) is phosphorylated during ANCA-induced neutrophil activation in vitro. However, the role of SYK in vivo is unknown. Here, we studied its role in the pathogenesis of experimental autoimmune vasculitis, a pre-clinical model of myeloperoxidase-ANCA-induced pauci-immune systemic vasculitis in the Wistar Kyoto rat. Up-regulation of SYK expression in inflamed renal and pulmonary tissue during early autoimmune vasculitis was confirmed by immunohistochemical and transcript analysis. R406, the active metabolite of fostamatinib, a small molecule kinase inhibitor with high selectivity for SYK, inhibited ANCA-induced pro-inflammatory responses in rat leucocytes in vitro. In an in vivo study, treatment with fostamatinib for 14 days after disease onset resulted in rapid resolution of urinary abnormalities, significantly improved renal and pulmonary pathology, and preserved renal function. Short-term exposure to fostamatinib did not significantly affect circulating myeloperoxidase-ANCA levels, suggesting inhibition of ANCA-induced inflammatory mechanisms in vivo. Finally, SYK expression was demonstrated within inflammatory glomerular lesions in ANCA-associated glomerulonephritis in patients, particularly within CD68+ve monocytes/macrophages. Thus, our data indicate that SYK inhibition warrants clinical investigation in the treatment of AAV.

SYK inhibition with fostamatinib in Waldenström's macroglobulinemia: In vitro cell based assays.

e19047 Background: Waldenström's macroglobulinemia (WM) is characterized by accumulation of IgM secreting neoplastic B cells in the bone marrow (BM). B-cell antigen receptor (BCR) signaling plays a pivotal role in the regulation of integrin-mediated retention of lymphoma cells in the BM. Signaling through the BCR leads to activation of spleen tyrosine kinase (SYK) and downstream kinases which play a role in lymphoma pathobiology. The Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib targets BCR-controlled signaling and integrin-mediated adhesion in WM cells, but patients with WM may become refractory to ibrutinib treatment. As SYK signaling is upstream of BTK, we explored the effect of the SYK inhibitor R406 (the active metabolite of fostamatinib) on BCR mediated signaling and cell adhesion in WM. Methods: MWCL-1 cells were treated with R406, CAL101 (PI3 kinase inhibitor) or ibrutinib at concentrations up to 10µM and stimulated with anti-IgM antibodies or PMA. The cells were transferred to plates coated with fibronectin to assess cell adhesion. For the proliferation assays, MWCL-1 cells or primary B cells were pretreated with kinase inhibitors, followed by stimulation of primary B cells with anti-IgM. Results: Anti-IgM or PMA alone stimulated the adhesion of MWCL-1 on fibronectin. The addition of R406 had a comparable effect to ibrutinib on inhibition of IgM mediated cell adhesion (IC50 = 0.32µM), consistent with the effect of both compounds on BCR mediated signaling. Neither compound affected PMA induced cell adhesion, indicating that the effect on IgM mediated cell adhesion was not due to toxicity. Lack of off-target toxicity was further confirmed in the MWCL-1 proliferation assays where the compounds showed less potency than in BCR-mediated assays. Comparable inhibition of adhesion and proliferation was seen with CAL101. Conclusions: Preliminary preclinical studies with R406 show that SYK is involved in BCR mediated signaling and cell adhesion in WM. CAL101 mediated inhibition of adhesion further confirmed the role of SYK, which is upstream of PI3K. R406 was as effective as ibrutinib in blocking WM cell adhesion. Further studies of SYK inhibition with fostamatinib as a potential treatment option for WM are warranted.

Spleen tyrosine kinase‑induced JNK‑dependent NLRP3 activation is involved in diabetic cardiomyopathy.

Diabetic cardiomyopathy (DCM) is a leading contributor to the increased morbidity and mortality rates associated with diabetes. Persistent inflammation has previously been reported to be involved in the pathogenesis of DCM. However, the exact underlying molecular mechanisms remain to be fully elucidated. In the present study, the role of spleen tyrosine kinase (Syk) and c‑Jun N‑terminal kinase (JNK) in NLR family pyrin domain‑containing 3 (NLRP3 inflammasome) activation in DCM were investigated in vivo and in vitro. Streptozotocin (65 mg/kg) was injected intraperitoneally into Sprague‑Dawley rats to induce a rat model of diabetes. Neonatal rat cardiomyocytes and H9c2 cells were cultured to detect the expression of JNK, NLRP3 and its associated downstream molecules, following treatment with Syk/JNK inhibitor or Syk/JNK‑small interfering (si)RNA in high glucose (HG) conditions. It was revealed that the protein and mRNA expression levels of phospho (p)‑Syk, p‑JNK, NLRP3 and its associated downstream molecules, including interleukin (IL)‑1β, were upregulated in vivo and in vitro. The JNK inhibitor significantly decreased the expression of NLRP3 and its downstream molecules in neonatal rat cardiomyocytes and H9c2 cells treated with HG. Furthermore, Syk‑siRNA and the Syk inhibitor markedly inhibited the HG‑induced activation of JNK, followed by the downregulation of NLRP3 and its downstream molecules at the mRNA and protein levels in cells. Therefore, it was demonstrated that the HG‑induced activation of NLRP3 was mediated by the activation of Syk/JNK, which subsequently increased the protein expression levels of mature IL‑1β, suggesting that the Syk/JNK/NLRP3 signaling pathway serves a critical role in the pathogenesis of DCM.

Abstract 3844: TAK-659, a SYK kinase inhibitor, demonstrates preclinical antitumor activity in solid tumor models

Abstract TAK-659 is a highly potent, reversible inhibitor of spleen tyrosine kinase (SYK) and fms related tyrosine kinase 3 (FLT3) that is currently being investigated in Phase I and II clinical trials. SYK is expressed ubiquitously in hematopoietic cells, and abnormal function of SYK has been implicated in several types of hematopoietic malignancies, including diffuse large B-cell lymphoma (DLBCL), chronic lymphocytic leukemia (CLL), and peripheral T-cell lymphoma (PTCL). Although there are considerable data supporting a role for SYK signaling in hematological cancers, data on the relevance of SYK in solid tumors are emerging. The literature suggests that SYK expression plays a role in the growth of breast and ovarian cancers, and the pancreatic adenocarcinoma microenvironment has been shown to be B-cell rich, giving us a basis to explore the activity of TAK-659 in these indications. Furthermore, ovarian cancer patients with recurrent disease have been shown to have an increase in pSYK at the time of relapse versus at diagnosis, suggesting a role for SYK in chemoresistance. The ability of TAK-659 to inhibit ex vivo colony formation of cells with the ability to grow anchorage independently in semi-solid medium was examined in 31 different human tumor xenografts. TAK-659 showed concentration-dependent inhibition of tumor colony growth in 5/31 tumor models tested, including gastric, breast, and ovarian cancers. Pre-clinically, TAK-659 has exhibited significant antitumor activity in a number of mouse xenograft models of solid tumors. We demonstrate here that daily oral administration of TAK-659 at 60mg/kg over 21 days leads to significant antitumor activity in primary human tumor models of gastric, pancreatic, triple negative breast (TNBC), and ovarian cancers, all of which express pSYK. Significant anti-tumor activity was also observed in the HCC70 TNBC xenograft model which does not express total SYK, demonstrating that TAK-659 may have anti-tumor effects beyond the inhibition of pSYK signaling. A decrease in myeloid derived suppressor cells was seen following TAK-659 treatment in this xenograft model, suggesting an immunomodulatory response may be driving the antitumor activity. Taken together, these data along with published information support the rationale for the investigation of TAK-659 in solid tumor cancer indications. Citation Format: Jessica J. Sappal, Matthew Theisen, Zhongmin Xiang, Stephen Tirrell, Rudy Christmas, Jie Yu, Mengkun Zhang, Karuppiah Kannan. TAK-659, a SYK kinase inhibitor, demonstrates preclinical antitumor activity in solid tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3844.

Fluorescent Tracking of Yeast Division Clarifies the Essential Role of Spleen Tyrosine Kinase in the Intracellular Control of Candida glabrata in Macrophages.

Macrophages play a critical role in the elimination of fungal pathogens. They are sensed via cell surface pattern-recognition receptors and are phagocytosed into newly formed organelles called phagosomes. Phagosomes mature through the recruitment of proteins and lysosomes, resulting in addition of proteolytic enzymes and acidification of the microenvironment. Our earlier studies demonstrated an essential role of Dectin-1-dependent activation of spleen tyrosine kinase (Syk) in the maturation of fungal containing phagosomes. The absence of Syk activity interrupted phago-lysosomal fusion resulting in arrest at an early phagosome stage. In this study, we sought to define the contribution of Syk to the control of phagocytosed live Candida glabrata in primary macrophages. To accurately measure intracellular yeast division, we designed a carboxyfluorescein succinimidyl ester (CFSE) yeast division assay in which bright fluorescent parent cells give rise to dim daughter cells. The CFSE-labeling of C. glabrata did not affect the growth rate of the yeast. Following incubation with macrophages, internalized CFSE-labeled C. glabrata were retrieved by cellular lysis, tagged using ConA-647, and the amount of residual CFSE fluorescence was assessed by flow cytometry. C. glabrata remained undivided (CFSE bright) for up to 18 h in co-culture with primary macrophages. Treatment of macrophages with R406, a specific Syk inhibitor, resulted in loss of intracellular control of C. glabrata with initiation of division within 4 h. Delayed Syk inhibition after 8 h was less effective indicating that Syk is critically required at early stages of macrophage–fungal interaction. In conclusion, we demonstrate a new method of tracking division of C. glabrata using CFSE labeling. Our results suggest that early Syk activation is essential for macrophage control of phagocytosed C. glabrata.

Calcium phosphate particles stimulate interleukin-1β release from human vascular smooth muscle cells: A role for spleen tyrosine kinase and exosome release

AimsCalcium phosphate (CaP) particle deposits are found in several inflammatory diseases including atherosclerosis and osteoarthritis. CaP, and other forms of crystals and particles, can promote inflammasome formation in macrophages leading to caspase-1 activation and secretion of mature interleukin-1β (IL-1β). Given the close association of small CaP particles with vascular smooth muscle cells (VSMCs) in atherosclerotic fibrous caps, we aimed to determine if CaP particles affected pro-inflammatory signalling in human VSMCs. Methods and resultsUsing ELISA to measure IL-1β release from VSMCs, we demonstrated that CaP particles stimulated IL-1β release from proliferating and senescent human VSMCs, but with substantially greater IL-1β release from senescent cells; this required caspase-1 activity but not LPS-priming of cells. Potential inflammasome agonists including ATP, nigericin and monosodium urate crystals did not stimulate IL-1β release from VSMCs. Western blot analysis demonstrated that CaP particles induced rapid activation of spleen tyrosine kinase (SYK) (increased phospho-Y525/526). The SYK inhibitor R406 reduced IL-1β release and caspase-1 activation in CaP particle-treated VSMCs, indicating that SYK activation occurs upstream of and is required for caspase-1 activation. In addition, IL-1β and caspase-1 colocalised in intracellular endosome-like vesicles and we detected IL-1β in exosomes isolated from VSMC media. Furthermore, CaP particle treatment stimulated exosome secretion by VSMCs in a SYK-dependent manner, while the exosome-release inhibitor spiroepoxide reduced IL-1β release. ConclusionsCaP particles stimulate SYK and caspase-1 activation in VSMCs, leading to the release of IL-1β, at least in part via exosomes. These novel findings in human VSMCs highlight the pro-inflammatory and pro-calcific potential of microcalcification.

Genetic and Pharmacological Dissection of the Role of Spleen Tyrosine Kinase (Syk) in Intestinal Inflammation and Immune Dysfunction in Inflammatory Bowel Diseases.

The DNAX adaptor protein 12 (DAP12) is a transmembrane adaptor molecule that signals through the activation of Syk (Spleen Tyrosine Kinase) in myeloid cells. The purpose of this study is to investigate the role of DAP12 and Syk pathways in inflammatory bowel diseases (IBDs). DAP12 deficient and DAP12 transgenic, overexpressing an increased amount of DAP12, mice and Syk deficient mice in the C57/BL6 background were used for these studies. Colitis was induced by administering mice with dextran sulfate sodium (DSS), in drinking water, or 2,4,6-trinitrobenzene sulfonic acid (TNBS), by intrarectal enema. Abundant expression of DAP12 and Syk was detected in colon samples obtained from Crohn's disease patients with expression restricted to immune cells infiltrating the colonic wall. In rodents development of DSS colitis as measured by assessing severity of wasting diseases, global colitis score,and macroscopic and histology scores was robustly attenuated in DAP12-/- and Syk-/- mice. In contrast, DAP12 overexpression resulted in a striking exacerbation of colon damage caused by DSS. Induction of colon expression of proinflammatory cytokines and chemokines in response to DSS administration was attenuated in DAP12-/- and Syk-/- mice, whereas opposite results were observed in DAP12 transgenic mice. Treating wild-type mice with a DAP-12 inhibitor or a Syk inhibitor caused a robust attenuation of colitis induced by DSS and TNBS. DAP12 and Syk are essential mediators in inflammation-driven immune dysfunction in murine colitides. Because DAP12 and Syk expression is upregulated in patients with active disease, present findings suggest a beneficial role for DAP12 and Syk inhibitors in IBD.

SYK protects cardiocytes against anoxia and hypoglycemia-induced injury in ischemic heart failure

Spleen tyrosine kinase (SYK), a non-receptor protein tyrosine kinase, is reported to be related to cell survival after A/H (anoxia/hypoglycemia) insult. However, the role of SYK in cardiocyte survival under A/H injury remains unclear. In this study, we aimed to gain insight into the role and molecular mechanism of SYK in cardiocytes exposed to A/H stress. The mRNA and protein expressions of SYK in H9c2 cardiocytes exposed to A/H injury, separately detected by real-time quantitative PCR and Western blot, were both robustly up-regulated. Then we overexpressed SYK in H9c2 with A/H injury, and found that cell viability was significantly increased and LDH leakage was decreased. Moreover, apoptosis measured by annexin V–fluorescein isothiocyanate/propidium iodide and reactive oxygen species (ROS) identified by 2′, 7′-dichlorofluorescin diacetate were markedly inhibited in H9c2 with A/H injury following SYK overexpression. Furthermore, we observed that SYK could induce HO-1 expression by regulating the Akt phosphorylation level in H9c2 with A/H injury, protecting H9c2 from the injury induced by A/H treatment.

Up regulation of Spleen Tyrosine Kinase in ballooned hepatocytes with Mallory‐Denk Bodies in Alcoholic Liver Disease

Liver injury from alcohol abuse causes balloon hepatocytes and MDB formation. Mallory‐Denk bodies (MDBs) are found in 70% to 75% of patients with alcoholic hepatitis (AH). MDBs are composed of intracellular aggregations of misfolded proteins in ballooned hepatocytes. To determine the mechanism of balloon degeneration and MDB formation in hepatocytes, we evaluated the role of spleen tyrosine kinase (Syk) which is associated with transmembrane receptors to mediate numerous signal transductions downstream of these receptors. Spleen tyrosine kinase is widely expressed in hematopoietic cells and modulates several signaling pathways including PIK3/AKT and p7056 pathways. These pathways are important in regulating the cell cycle and are actively involved in mediating cell adhesion. Dysregulation of the PI3K/Akt pathway is implicated in a number of human diseases including cancer, diabetes, cardiovascular disease and neurological diseases. In this study, liver biopsy sections fixed in formalin and embedded in paraffin (FFPE) were used from patients with alcoholic hepatitis (AH). The results show that the expression of Syk protein is up regulated by RNAseq and real time PCR analyses in the alcoholic hepatitis patients compared to controls. The results were also supported by using IHC fluorescent intensity staining morphometric system. Morphometric quantification of fluorescent intensity showed a two fold increase in Syk in the cells forming MDBs compared to surrounding normal hepatocytes. Interestingly, the upregulation of Syk protein is co‐localized with ubiquitinated proteins in the cytoplasm of balloon cell hepatocytes which have formed MDBs. This observation demonstrates the role of Syk as a potential multifunctional target in protein quality control mechanism of hepatocytes when ER stress is activated.

Inhibition of spleen tyrosine kinase activation ameliorates inflammation, cell death, and steatosis in alcoholic liver disease.

The spectrum of alcoholic liver disease (ALD) is a major cause of mortality with limited therapies available. Because alcohol targets numerous signaling pathways in hepatocytes and in immune cells, the identification of a master regulatory target that modulates multiple signaling processes is attractive. In this report, we assessed the role of spleen tyrosine kinase (SYK), a nonreceptor tyrosine kinase, which has a central modulatory role in multiple proinflammatory signaling pathways involved in the pathomechanism of ALD. Using mouse disease models that represent various phases in the progression of human ALD, we found that alcohol, in all of these models, induced SYK activation in the liver, both in hepatocytes and liver mononuclear cells. Furthermore, significant SYK activation also occurred in liver samples and peripheral blood mononuclear cells of patients with ALD/alcoholic hepatitis compared to controls. Functional inhibition of SYK activation in vivo abrogated alcohol-induced hepatic neutrophil infiltration, resident immune cell activation, as well as inflammasome and extracellular signal-regulated kinase 1 and 2-mediated nuclear factor kappa B activation in mice. Strikingly, inhibition of SYK activation diminished alcohol-induced hepatic steatosis and interferon regulatory factor 3-mediated apoptosis. Our data demonstrate a novel, functional, and multicellular role for SYK phosphorylation in modulating immune cell-driven liver inflammation, hepatocyte cell death, and steatosis at different stages of ALD. These novel findings highlight SYK as a potential multifunctional target in the treatment of alcoholic steatohepatitis. (Hepatology 2016;64:1057-1071).

Abstract 2465: Spleen tyrosine kinase (SYK) in neuroblastoma tumorigenesis

Abstract Tyrosine kinases play an important role in tumorigenesis by contributing to the regulation of cell proliferation and survival, and are therefore among the most attractive drug targets. SYK is a non-receptor tyrosine kinase highly expressed in cells of hematopoietic origin where it contributes to immune receptor signaling. The role of SYK in cancer is best understood in hematological malignancies where it promotes survival, and SYK inhibition has been shown to be a promising therapeutic approach. For solid tumors the role of SYK remains double-edged, as it has been found to promote but also suppress tumor development dependent on the cancer type. Besides its role in survival signaling SYK has also been found to contribute to drug resistance in several malignancies. Neuroblastoma (NB) is a malignancy of early childhood. Although there have been great advances in the treatment of NB during the past 30 years, the prognosis for high- risk patients remains poor. In this study we have evaluated SYK as a potential drug target in NB. Examination of gene expression datasets indicated a correlation between high expression of SYK and poor prognosis in NB. Screening of NB cell lines showed that SYK mRNA was present in the majority of NB cells lines whereas the SYK protein was detected less frequently. However, SYK was detectable in NB tumor tissue using immunohistochemistry. The efficacy of different, commercially available, SYK inhibitors was evaluated by comparing the neuroblastoma cell lines SH-SY5Y (high SYK expression) and SK-N-BE(2) (low SYK expression) using a cell viability assay. While one inhibitor displayed a markedly stronger effect on the viability of SH-SY5Y cells compared to SK-N-BE(2) the effect of the other inhibitors appears to be less specific. To confirm that SYK inhibition leads to decreased cell proliferation SYK specific siRNA was used. After 48h incubation the cell viability of SH-SY5Y cells was decreased by approximately 25%. Our findings indicate that SYK may be a possible drug target in neuroblastoma. To further evaluate its potential, combination studies using SYK inhibitors and cytostatic drugs will be performed. Citation Format: Conny Tuemmler, Gianina Dumitriu, Julia Cserna, Ugo L. Moens, Per Kogner, John Inge Johnsen, Baldur Sveinbjørnsson. Spleen tyrosine kinase (SYK) in neuroblastoma tumorigenesis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2465.

Therapeutic Benefits of Spleen Tyrosine Kinase Inhibitor Administration on Binge Drinking-Induced Alcoholic Liver Injury, Steatosis, and Inflammation in Mice.

Binge drinking is increasingly recognized as an important cause of liver disease with limited therapeutic options for patients. Binge alcohol use, similar to chronic alcohol consumption, induces numerous deregulated signaling events that drive liver damage, steatosis, and inflammation. In this article, we evaluated the role of spleen tyrosine kinase (SYK), which modulates numerous signaling events previously identified linked in the development alcohol-induced liver pathology. A 3-day alcohol binge was administered to C57BL/6 female mice, and features of alcoholic liver disease were assessed. Some mice were treated daily with intraperitoneal injections of a SYK inhibitor (R406; 5 to 10mg/kg body weight) or drug vehicle control. Liver and serum samples were collected and were assessed by Western blotting, biochemical, ELISA, electrophoretic mobility shift assays, real-time quantitative polymerase chain reaction, and histopathological analysis. We found that binge drinking induced significant SYK activation (SYK(Y525/526) ) with no change in total SYK expression in the liver. Functional inhibition of SYK activation using a potent SYK inhibitor, R406, was associated with a significant decrease in alcohol-induced hepatic inflammation as demonstrated by decreased phospho-nuclear factor kappa beta (NF-κB) p65, NF-κB nuclear binding, tumor necrosis factor-alpha, and monocyte chemoattractant protein-1 mRNA in the liver. Compared to vehicle controls, SYK inhibitor treatment decreased alcohol binge-induced hepatocyte injury indicated by histology and serum alanine aminotransferase. Strikingly, SYK inhibitor treatment also resulted in a significant reduction in alcohol-induced liver steatosis. Our novel observations demonstrate the role of SYK, activation in the pathomechanism of binge drinking-induced liver disease highlighting SYK a potential multifaceted therapeutic target.

Spleen tyrosine kinase regulates mammary epithelial cell proliferation in mammary glands of dairy cows

Spleen tyrosine kinase (SYK) is a nonreceptor tyrosine kinase that has been considered a hematopoietic cell-specific signal transducer involved in cell proliferation and differentiation. However, the role of SYK in normal mammary gland is still poorly understood. Here we show that SYK is expressed in mammary glands of dairy cows. Expression of SYK was higher in dry period mammary tissues than in lactating mammary tissues. Knockdown and overexpression of SYK affected dairy cow mammary epithelial cell proliferation as well as the expression of signal molecules involved in proliferation, including protein kinase B (PKB, also known as AKT1), p42/44 mitogen-activated protein kinase (MAPK), and signal transducer and activator of transcription 5 (STAT5). Dual-luciferase reporter assay showed that SYK increased the transcriptional activity of the AKT1 promoter, and cis-elements within the AKT1 promoter region from −439 to −84 bp mediated this regulation. These results suggest that SYK affects mammary epithelial cell proliferation by activating AKT1 at the transcriptional level in mammary glands of dairy cows, which is important for the mammary remodeling process in dry cows as well as for increasing persistency of lactation in lactating cows.

A role for spleen tyrosine kinase in renal fibrosis in the mouse obstructed kidney

AimsSpleen tyrosine kinase (Syk) is a non-receptor tyrosine kinase involved in the signalling pathways of the B cell receptor, Fcγ-receptor and some leukocyte integrins. However, Syk can also be expressed by some non-haematopoietic cell types, although whether Syk signalling in these cells contributes to the pathogenesis of kidney disease is unknown. To address this question, we examined the function of Syk in antibody-independent renal interstitial fibrosis in the unilateral ureteric obstruction (UUO) model. Main methodsGroups of C57BL/6J mice were treated with a selective Syk inhibitor (CC0417, 30mg/kg/bid), vehicle, or no treatment, from the time of surgery until being killed 7days later. Key findingsA substantial accumulation of interstitial Syk+ cells was seen in the UUO kidney. Double staining identified Syk expression by infiltrating macrophages and by a subset of α-SMA+ myofibroblasts. CC0417 treatment substantially reduced the Syk+ cell population in conjunction with a reduction in both myofibroblast and macrophage accumulation. This was associated with a substantial reduction in collagen IV deposition and mRNA levels of pro-fibrotic (collagen I, collagen IV, fibronectin, α-SMA, TGF-β1 and PAI-1) and pro-inflammatory molecules (MCP-1, TNF-α and NOS2). CC0417 treatment reduced both PDGF-B mRNA levels and Ki67+ proliferating interstitial cells in the UUO kidney. Furthermore, CC0417 inhibited PDGF-AB induced ERK activation and cell proliferation of cultured primary kidney fibroblasts. SignificanceThis study has identified a pathologic role for Syk in renal interstitial fibrosis. Syk inhibitors may have therapeutic potential in chronic fibrotic kidney disease.

Spleen Tyrosine Kinase Confers Paclitaxel Resistance in Ovarian Cancer

Adaptive chemoresistance and consequent tumor recurrence present major obstacles to the improvement of the prognosis and quality-of-life of patients with advanced-stage ovarian cancer. In this issue of Cancer Cell, Yu and colleagues describe the critical role of spleen tyrosine kinase (SYK) in paclitaxel resistance by modulating the stability of microtubules.