The Syk tyrosine kinase suppresses malignant growth of human breast cancer cells

Integrative bioinformatics approach yields a novel gene expression risk model for prognosis and progression prediction in prostate cancer

Prostate cancer (PCa), a prevalent malignancy among elderly males, exhibits a notable rate of advancement, even when subjected to conventional androgen deprivation therapy or chemotherapy. An effective progression prediction model would prove invaluable in identifying patients with a higher progression risk. Using bioinformatics strategies, we integrated diverse data sets of PCa to construct a novel risk model predicated on gene expression and progression-free survival (PFS). The accuracy of the model was assessed through validation using an independent data set. Eight genes were discerned as independent prognostic factors and included in the prediction model. Patients assigned to the high-risk cohort demonstrated a diminished PFS, and the areas under the curve of our model in the validation set for 1-year, 3-year, and 5-year PFS were 0.9325, 0.9041 and 0.9070, respectively. Additionally, through the application of single-cell RNA sequencing to two castration-related prostate cancer (CRPC) samples and two hormone-related prostate cancer (HSPC) samples, we discovered that luminal cells within CRPC exhibited an elevated risk score. Subsequent molecular biology experiments corroborated our findings, illustrating heightened SYK expression levels within tumour tissues and its contribution to cancer cell migration. We found that the knockdown of SYK could inhibit migration in PCa cells. Our progression-related risk model demonstrated the potential prognostic value of SYK and indicated its potential as a target for future diagnosis and treatment strategies in PCa management.

Identification of natural product-based effective inhibitors of spleen tyrosine kinase (SYK) through virtual screening and molecular dynamics simulation approaches

Spleen tyrosine kinase (SYK) is a non-receptor tyrosine kinase that plays an essential role in signal transduction across different cell types. In the context of allergy and autoimmune disorders, it is a crucial regulator of immune receptor signaling in inflammatory cells such as B cells, mast cells, macrophages, and neutrophils. Developing SYK kinase inhibitors has gained significant interest for potential therapeutic applications in neurological and cancer-related conditions. The clinical use of the most advanced SYK inhibitor, Fostamatinib, has been limited due to its unwanted side effects. Thus, a more targeted approach to SYK inhibition would provide a more comprehensive treatment window. In this study, we used a virtual screening approach to identify potential SYK inhibitors from natural compounds from the IMPPAT database. We identified two compounds, Isolysergic acid and Michelanugine, which showed strong affinity and specificity for the SYK binding pocket. All-atom molecular dynamics (MD) simulations were also performed to explore the stability, conformational changes, and interaction mechanism of SYK in complexes with the identified compounds. The identified compounds might have the potential to be developed into promising SYK inhibitors for the treatment of various diseases, including autoimmune disorders, cancer, and inflammatory diseases. This work aims to identify potential phytochemicals to develop a new protein kinase inhibitor for treating advanced malignancies by providing an updated understanding of the role of SYK.Communicated by Ramaswamy H. Sarma.

Spleen tyrosine kinase facilitates the progression of papillary thyroid cancer regulated by the hsa_circ_0006417/miR-377-3p axis

Papillary thyroid cancer (PTC) is a prevalent malignancy worldwide. Spleen tyrosine kinase (SYK) is a crucial enzyme that participates in various biological processes, including cancer progression. This study aims to uncover the biological function of SYK in PTC. SYK expression patterns in PTC were evaluated using quantitative real time polymerase chain reaction (qRT-PCR), immunohistochemistry (IHC), and western blot. Cell function assays were performed to assess the effects of SYK on PTC. Bioinformatics analysis was conducted to identify intriguing microRNA (miRNA) and circular RNA (circRNA). Dual-Luciferase Reporter or RNA immunoprecipitation assays were used to investigate the correlation among SYK, miR-377-3p, and hsa_circ_0006417. SYK was upregulated in PTC. Overexpression of SYK exhibited a positive correlation with tumor size, lymph node metastasis, and unfavorable disease-free survival. Functional assays revealed that SYK exerted tumorigenic effect on PTC cells through mTOR/4E-BP1 pathway. Mechanistically, hsa_circ_0006417 and miR-377-3p regulated SYK expression, offering modulating its tumor-promoting effects. Collectively, SYK acts as an oncogene in PTC through mTOR/4E-BP1 pathway, which is regulated by the hsa_circ_0006417/miR-377-3p axis, thereby providing a potential alternative for PTC treatment.

Review and prospects of targeted therapies for Spleen tyrosine kinase (SYK)

Spleen tyrosine kinase (SYK) is a non-receptor tyrosine kinase. The dysregulation of SYK is closely related to the occurrence and development of allergic diseases, autoimmune diseases and cancer. SYK has become an attractive target for drug discovery due to its important biological functions. This article reviews the biological function of SYK, the relationship between SYK and disease, and therapies targeting SYK. In addition, inspired by new technologies such as proteolysis targeting chimeras (PROTACs) and phosphatase recruiting chimeras (PHORCs), we propose the development of new therapeutic approaches for targeting SYK, such as SYK PROTACs and SYK PHORCs, which may overcome deficiencies of existing methods.

Involvement of the AKT Pathway in Resistance to Erlotinib and Cabozantinib in Triple-Negative Breast Cancer Cell Lines

Resistance to protein tyrosine kinase inhibitors (TKIs) presents a significant challenge in therapeutic target development for cancers such as triple-negative breast cancer (TNBC), where conventional therapies are ineffective at combatting systemic disease. Due to increased expression, the receptor tyrosine kinases EGFR (epidermal growth factor receptor) and c-Met are potential targets for treatment. However, targeted anti-EGFR and anti-c-Met therapies have faced mixed results in clinical trials due to acquired resistance. We hypothesize that adaptive responses in regulatory kinase networks within the EGFR and c-Met signaling axes contribute to the development of acquired erlotinib and cabozantinib resistance. To test this, we developed two separate models for cabozantinib and erlotinib resistance using the MDA-MB-231 and MDA-MB-468 cell lines, respectively. We observed that erlotinib- or cabozantinib-resistant cell lines demonstrate enhanced cell proliferation, migration, invasion, and activation of EGFR or c-Met downstream signaling (respectively). Using a SILAC (Stable Isotope Labeling of Amino acids in Cell Culture)-labeled quantitative mass spectrometry proteomics approach, we assessed the effects of erlotinib or cabozantinib resistance on the phosphoproteome, proteome, and kinome. Using this integrated proteomics approach, we identified several potential kinase mediators of cabozantinib resistance and confirmed the contribution of AKT1 to erlotinib resistance in TNBC-resistant cell lines.

Cancer invasion and metastasis: Insights from murine pubertal mammary gland morphogenesis

Cancer invasion and metastasis accounts for the majority of cancer related mortality. A better understanding of the players that drive the aberrant invasion and migration of tumors cells will provide critical targets to inhibit metastasis. Postnatal pubertal mammary gland morphogenesis is characterized by highly proliferative, invasive, and migratory normal epithelial cells. Identifying the molecular regulators of pubertal gland development is a promising strategy since tumorigenesis and metastasis is postulated to be a consequence of aberrant reactivation of developmental stages. In this review, we summarize the pubertal morphogenesis regulators that are involved in cancer metastasis and revisit pubertal mammary gland transcriptome profiling to uncover both known and unknown metastasis genes. Our updated list of pubertal morphogenesis regulators shows that most are implicated in invasion and metastasis. This review highlights molecular linkages between development and metastasis and provides a guide for exploring novel metastatic drivers.

Cathepsin K inhibition induces Raptor destabilization and mitochondrial dysfunction via Syk/SHP2/Src/OTUB1 axis-mediated signaling

The Raptor signaling pathway is a critical point of intervention in the invasion and progression of cancer. The non-receptor tyrosine kinase Src-mediated phosphorylation of OTUB1-Y26 plays a critical role in Raptor stabilization, whereas cathepsin K inhibitor (odanacatib; ODN) and knockdown (siRNA) induce Raptor destabilization. However, the mechanisms involved in cathepsin K inhibition-induced OTUB1-Y26 phosphorylation in Raptor stabilization have not been yet elucidated. This study showed that cathepsin K inhibition activates SHP2, a tyrosine phosphatase, that dephosphorylates OTUB1 and destabilizes Raptor, whereas SHP2 deletion and pharmacological inhibition increase OTUB1-Y26 phosphorylation and Raptor expression. SHP2 deletion also led to the inhibition of ODN-induced mitochondrial ROS, fusion, and dysfunction. Furthermore, cathepsin K inhibition phosphorylated spleen tyrosine kinase (Syk) at Y525 and Y526, resulting in the SHP2-mediated dephosphorylation of OTUB1-Y26. Collectively, our findings identified Syk not only as an upstream tyrosine kinase required for SHP2 activation but also showed a critical mechanism that regulates ODN-induced Raptor downregulation and mitochondrial dysfunction. In conclusion, Syk/SHP2/Src/OTUB1 axis-mediated signaling can act as a therapeutic target in cancer management.

Epigenetic upregulation of spleen tyrosine kinase in cancer cells through p53-dependent downregulation of DNA methyltransferase

Syk is a tumor suppressor gene in some solid tumors. Currently, it remains unknown how Syk gene hypermethylation is controlled by DNA methyltransferase (DNMT) and p53. In colorectal cancer HCT116 cells, we found that protein and mRNA levels of Syk were much higher in WT than in p53^-/- cells. Both p53 inhibitor PFT-α and p53 silencing can reduce the protein and mRNA expression of Syk in WT cells, while DNMT inhibitor 5-Aza-2'-dC can increase Syk expression in p53^-/- cells. Interestingly, the DNMT expression in p53^-/- HCT116 cells was higher than that in WT cells. PFT-α can not only enhance Syk gene methylation but also increase DNMT1 protein and mRNA levels in WT HCT116 cells. In metastatic lung cancer cell lines A549 and PC9, which express WT p53 and gain function of p53, respectively, PFT-α can also downregulate Syk mRNA and protein expression. However, the Syk methylation level was increased by PFT-α in A549 but not in PC9 cells. Likewise, 5-Aza-2'-dC transcriptionally increased Syk gene expression in A549 cells, but not in PC9 cells. In summary methylation of Syk promoter requires DNMT1, and p53 can upregulate Syk expression via downregulation of DNMT1 at the transcriptional level.

Targeting the splicing isoforms of spleen tyrosine kinase affects the viability of colorectal cancer cells

Spleen tyrosine kinase (Syk) expression have been both positively and negatively associated with tumorigenesis. Our goal was to evaluate the contribution of Syk and its two splice variants, full length Syk (L) and short isoform Syk (S), in the tumor biology of colorectal cancer cells (CRC). The analysis of Syk expression in primary human colorectal tumors, as well as the analysis of TCGA database, revealed a high Syk mRNA expression score in colorectal cancer tumors, suggesting a tumor promotor role of Syk in CRC. Our analysis showed that Syk (L) isoform is highly expressed in the majority of the tumor tissues and that it remains expressed in tumors in which global Syk expression is downregulated, suggesting the dependence of tumors to Syk (L) isoform. We also identified a small cluster of tumor tissues, which express a high proportion of Syk (S) isoform. This specific cluster is associated with overexpressed genes related to translation and mitochondria, and down regulated genes implicated in the progression of mitosis. For our functional studies, we used short hairpin RNA tools to target the expression of Syk in CRC cells bearing the activating K-Ras (G13D) mutation. Our results showed that while global Syk knock down increases cell proliferation and cell motility, Syk (L) expression silencing affects the viability and induces the apoptosis of the cells, confirming the dependence of cells on Syk (L) isoform for their survival. Finally, we report the promising potential of compound C-13, an original non-enzymatic inhibitor of Syk isolated in our group. In vitro studies showed that C-13 exerts cytotoxic effects on Syk-positive CRC cells by inhibiting their proliferation and their motility, and by inducing their apoptosis, while Syk-negative cell lines viability was not affected. Moreover, the oral and intraperitoneal administration of C-13 reduced the tumor growth of CRC DLD-1 cells xenografts in Nude mice in vivo.

Tumor cell SYK expression modulates the tumor immune microenvironment composition in human cancer via TNF-α dependent signaling

BACKGROUND

The expression of SYK in cancer cells has been associated with both tumor promoting and tumor suppressive effects. Despite being proposed as anticancer therapeutic target, the possible role of SYK in modulating local adaptive antitumor immune responses remains uncertain. Using detailed analysis of primary human tumors and in vitro models, we reveal the immunomodulatory effect of SYK protein in human solid cancer.

METHODS

We spatially mapped SYK kinase in tumor cells, stromal cells and tumor-infiltrating leukocytes (TILs) in 808 primary non-small cell lung carcinomas (NSCLCs) from two cohorts and in 374 breast carcinomas (BCs) from two independent cohorts. We established the associations of localized SYK with clinicopathologic variables and outcomes. The immunomodulatory role of SYK on tumor cells was assessed using in vitro cytokine stimulation, transcriptomic analysis and selective SYK blockade using a small molecule inhibitor. Functional responses were assessed using cocultures of tumor cells with peripheral blood lymphocytes. T cell responses in baseline and post-treatment biopsies from patients with BC treated with a SYK inhibitor in a phase I clinical trial were also studied.

RESULTS

Elevated tumor cell or leukocyte SYK expression was associated with high CD4⁺ and CD8⁺ TILs and better outcome in both NSCLC and BC. Tumor cell SYK was associated with oncogenic driver mutations in EGFR or KRAS in lung adenocarcinomas and with triple negative phenotype in BC. In cultured tumor cells, SYK was upregulated by TNFα and required for the TNFα-induced proinflammatory responses and T cell activation. SYK blockade after nivolumab in a phase I clinical trial including three patients with advanced triple negative BC reduced TILs and T cell proliferation. Our work establishes the proinflammatory function of tumor cell SYK in lung and breast cancer. SYK signaling in cultured tumor cells is required for T cell activation and SYK blockade limits adaptive antitumor immune responses and tumor rejection in patients with cancer.

CONCLUSIONS

Together, our results establish the immunomodulatory role of SYK expression in human solid tumors. This information could be used to develop novel biomarkers and/or therapeutic strategies.

Apocynum Leaf Extract Suppresses the Progress of Atherosclerosis in Rats via the FKN/SYK/p38 Signal Pathway

To investigate the antiatherosclerotic effects of flavonoids extracted from Apocynum venetum (AVF) leaves in atherosclerotic rats and the underlying mechanisms, a total of 72 male Wistar rats were randomly divided into six groups: control group, model group, simvastatin group, low-dose AVF group, medium-dose AVF group, and high-dose AVF group. Atherosclerosis in rats was induced with a high-fat diet and an intraperitoneal injection of VD₃ once daily for three contiguous days at a total injection dose of 70 U/kg. At the end of the 13^th week, total serum cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) contents were measured. The hematoxylin-eosin (HE) staining was applied to evaluate the morphological changes. The ELISA method was used to detect related inflammatory factors and oxidative stress indicators. The corresponding protein expression and the mRNA level were detected by western blot analysis and reverse transcriptase PCR. HE staining showed that the thoracic aorta wall was thickened, and the aortic subendothelial foam cells and lipid vacuoles were reduced in the medium/high-AVF groups. Similarly, the TC, TG, LDL-C, and malondialdehyde (MDA) levels in the model group were significantly higher, but the HDL-C level and superoxide dismutase (SOD) activity were lower than those of the control group, and these effects were ameliorated by treatment with simvastatin or AVF. ELISA results showed that compared with the control group, the model group C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) results were significantly increased, and the medium AVF and high AVF could significantly reduce the expression of related inflammatory factors. The AVF inhibited intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin mRNA and related protein expression in the aorta in atherosclerotic rats. Western blot analysis also showed that AVF can significantly reduce the protein expression of fractalkine (FKN), spleen tyrosine kinase (SYK), and p38 mitogen-activated protein kinase (p38) in the rat aorta. We believe that the AVF can effectively reduce blood lipid levels in rats with atherosclerosis and delay atherosclerotic progression by inhibiting excessive inflammatory factors and inhibiting related adhesion factors. The underlying mechanism may be related to the FKN/SYK/p38 signaling pathway activity. Our results contribute to validating the traditional use of the Apocynum leaf extract in the treatment of atherosclerosis.

Analysis of SYK Gene as a Prognostic Biomarker and Suggested Potential Bioactive Phytochemicals as an Alternative Therapeutic Option for Colorectal Cancer: An In-Silico Pharmaco-Informatics Investigation

BACKGROUND

SYK gene regulates the expression of SYK kinase (Spleen tyrosine kinase), an important non-receptor protein-tyrosine kinase for immunological receptor-mediated signaling, which is also considered a tumor growth metastasis initiator. An onco-informatics analysis was adopted to evaluate the expression and prognostic value of the SYK gene in colorectal cancer (CRC), the third most fatal cancer type; of late, it may be a biomarker as another targeted site for CRC. In addition, identify the potential phytochemicals that may inhibit the overexpression of the SYK kinase protein and minimize the human CRC.

MATERIALS & METHODS

The differential expression of the SYK gene was analyzed using several transcriptomic databases, including Oncomine, UALCAN, GENT2, and GEPIA2. The server cBioPortal was used to analyze the mutations and copy number alterations, whereas GENT2, Gene Expression Profiling Interactive Analysis (GEPIA), Onco-Lnc, and PrognoScan were used to examine the survival rate. The protein-protein interaction network of SYK kinase and its co-expressed genes was conducted via Gene-MANIA. Considering the SYK kinase may be the targeted site, the selected phytochemicals were assessed by molecular docking using PyRx 0.8 packages. Molecular interactions were also observed by following the Ligplot+ version 2.2. YASARA molecular dynamics simulator was applied for the post-validation of the selected phytochemicals.

RESULTS

Our result reveals an increased level of mRNA expression of the SYK gene in colorectal adenocarcinoma (COAD) samples compared to those in normal tissues. A significant methylation level and various genetic alterations recurrence of the SYK gene were analyzed where the fluctuation of the SYK alteration frequency was detected across different CRC studies. As a result, a lower level of SYK expression was related to higher chances of survival. This was evidenced by multiple bioinformatics platforms and web resources, which demonstrated that the SYK gene can be a potential biomarker for CRC. In this study, aromatic phytochemicals, such as kaempferol and glabridin that target the macromolecule (SYK kinase), showed higher stability than the controls, and we have estimated that these bioactive potential phytochemicals might be a useful option for CRC patients after the clinical trial.

CONCLUSIONS

Our onco-informatics investigation suggests that the SYK gene can be a potential prognostic biomarker of CRC. On the contrary, SYK kinase would be a major target, and all selected compounds were validated against the protein using in-silico drug design approaches. Here, more in vitro and in vivo analysis is required for targeting SYK protein in CRC.

miR-96-5p is the tumor suppressor in osteosarcoma via targeting SYK

BACKGROUND

Osteosarcoma is a multiple malignant tumor in adolescents. MicroRNAs (MiRNAs) have been found to express abnormally in OS tissues and are considered as potential targets for OS prognosis and treatment.

METHODS

MiR-96-5p and SYK expression in clinical samples, osteoblast and OS cell lines were detected. The changes of cell proliferation, apoptosis, adhesion and metastasis of OS cells were detected by CCK-8, BrdU, caspase-3 activity and transwell assay. Dual luciferase report analysis and RNA pull-down were used to confirm binding relation of miR-96-5p and SYK.

RESULTS

MiR-96-5p was increased in OS tissue and cells. Moreover, miR-96-5p inhibits proliferation, adhesion and migration of HOS and Saos-2 cells, and promotes cell apoptosis. SYK has been identified to be targeted by miR-96-5p. Overexpressed SYK inhibits the suppressive impact of miR-96-5 on OS cells.

CONCLUSION

MiR-96-5p may function as an effective target in OS treatment.

Spleen tyrosine kinase (SYK) inhibitor PRT062607 protects against ovariectomy-induced bone loss and breast cancer-induced bone destruction

Osteolytic diseases, including breast cancer-induced osteolysis and postmenopausal osteoporosis, are attributed to excessive bone resorption by osteoclasts. Spleen tyrosine kinase (SYK) is involved in osteoclastogenesis and bone resorption, whose role in breast cancer though remains controversial. Effects of PRT062607 (PRT), a highly specific inhibitor of SYK, on the osteoclast and breast cancer functionalities are yet to be clarified. This study demonstrated the in vitro inhibitory actions of PRT on the osteoclast-specific gene expression, bone resorption, and osteoclastogenesis caused by receptor activator of nuclear factor kappa B ligand (RANKL), as well as its in vitro suppressive effects on the growth, migration and invasion of breast carcinoma cell line MDA-MB-231, which were achieved through PLCγ2 and PI3K-AKT-mTOR pathways. Further, we proved that PRT could prevent post-ovariectomy (OVX) loss of bone and breast cancer-induced bone destruction in vivo, which agreed with the in vitro outcomes. In conclusion, our findings suggest the potential value of PRT in managing osteolytic diseases mediated by osteoclasts.

Comparison of SYK Signaling Networks Reveals the Potential Molecular Determinants of Its Tumor-Promoting and Suppressing Functions

Spleen tyrosine kinase (SYK) can behave as an oncogene or a tumor suppressor, depending on the cell and tissue type. As pharmacological SYK inhibitors are currently evaluated in clinical trials, it is important to gain more information on the molecular mechanisms underpinning these opposite roles. To this aim, we reconstructed and compared its signaling networks using phosphoproteomic data from breast cancer and Burkitt lymphoma cell lines where SYK behaves as a tumor suppressor and promoter. Bioinformatic analyses allowed for unveiling the main differences in signaling pathways, network topology and signal propagation from SYK to its potential effectors. In breast cancer cells, the SYK target-enriched signaling pathways included intercellular adhesion and Hippo signaling components that are often linked to tumor suppression. In Burkitt lymphoma cells, the SYK target-enriched signaling pathways included molecules that could play a role in SYK pro-oncogenic function in B-cell lymphomas. Several protein interactions were profoundly rewired in the breast cancer network compared with the Burkitt lymphoma network. These data demonstrate that proteomic profiling combined with mathematical network modeling allows untangling complex pathway interplays and revealing difficult to discern interactions among the SYK pathways that positively and negatively affect tumor formation and progression.

Alcohol Intake and Alcohol-SNP Interactions Associated with Prostate Cancer Aggressiveness

Excessive alcohol intake is a well-known modifiable risk factor for many cancers. It is still unclear whether genetic variants or single nucleotide polymorphisms (SNPs) can modify alcohol intake's impact on prostate cancer (PCa) aggressiveness. The objective is to test the alcohol-SNP interactions of the 7501 SNPs in the four pathways (angiogenesis, mitochondria, miRNA, and androgen metabolism-related pathways) associated with PCa aggressiveness. We evaluated the impacts of three excessive alcohol intake behaviors in 3306 PCa patients with European ancestry from the PCa Consortium. We tested the alcohol-SNP interactions using logistic models with the discovery-validation study design. All three excessive alcohol intake behaviors were not significantly associated with PCa aggressiveness. However, the interactions of excessive alcohol intake and three SNPs (rs13107662 [CAMK2D, p = 6.2 × 10-6], rs9907521 [PRKCA, p = 7.1 × 10-5], and rs11925452 [ROBO1, p = 8.2 × 10-4]) were significantly associated with PCa aggressiveness. These alcohol-SNP interactions revealed contrasting effects of excessive alcohol intake on PCa aggressiveness according to the genotypes in the identified SNPs. We identified PCa patients with the rs13107662 (CAMK2D) AA genotype, the rs11925452 (ROBO1) AA genotype, and the rs9907521 (PRKCA) AG genotype were more vulnerable to excessive alcohol intake for developing aggressive PCa. Our findings support that the impact of excessive alcohol intake on PCa aggressiveness was varied by the selected genetic profiles.

Intratumor Heterogeneity Correlates With Reduced Immune Activity and Worse Survival in Melanoma Patients

Background

Human malignant melanoma is a highly aggressive, heterogeneous and drug-resistant cancer. Due to a high number of clones, harboring various mutations that affect key pathways, there is an exceptional level of phenotypic variation and intratumor heterogeneity (ITH) in melanoma. This poses a significant challenge to personalized cancer medicine. Hitherto, it remains unclear to what extent the heterogeneity of melanoma affects the immune microenvironment. Herein, we explore the interaction between the tumor heterogeneity and the host immune response in a melanoma cohort utilizing The Cancer Genome Atlas (TCGA).

Methods

Clonal Heterogeneity Analysis Tool (CHAT) was used to estimate intratumor heterogeneity, and immune cell composition was estimated using CIBERSORT. The Overall Survival (OS) among groups was analyzed using Kaplan-Meier curves with the log-rank test and multivariate cox regression. RNA-seq data were evaluated to identify differentially expressed immunomodulatory genes. The reverse phase protein array (RPPA) data platform was used to validate immune responses at protein level.

Results

Tumors with high heterogeneity were associated with decreased overall survival (p = 0.027). High CHAT tumors were correlated with less infiltration by anti-tumor CD8 T cells (p = 0.0049), T follicular cells (p = 0.00091), and M1 macrophages (p = 0.0028), whereas tumor-promoting M2 macrophages were increased (p = 0.02). High CHAT tumors correlated with a reduced expression of immunomodulatory genes, particularly Programmed Cell Death 1 (PD1) and its ligand PD-L1. In addition, high CHAT tumors exhibited lower immune Cytotoxic T lymphocytes (CTLs)-mediated toxicity pathway score (p = 2.9E-07) and cytotoxic pathway score (p = 2.9E-08). High CHAT tumors were also associated with a lower protein level of immune-regulatory kinases, such as lymphocyte-specific protein tyrosine kinase (LCK) (p = 3.4e-5) and spleen tyrosine kinase (SYK) (p = 0.0011).

Conclusions

Highly heterogeneous melanoma tumors are associated with reduced immune cell infiltration and immune response activation as well as decreased survival. Our results reveal that intratumor heterogeneity is an indicative factor for patient survival due to its impact on anti-tumor immune response.

Systematic Analysis of Spleen Tyrosine Kinase Expression and its Clinical Outcomes in Various Cancers

Background:

Spleen tyrosine kinase (SYK) is an important enzyme in the proliferation and differentiation of all hematopoietic tissues. Its role as a cancer driver is well documented in liquid tumors; however, cumulative evidence has suggested an opposite role in other tumor types.

Objectives:

To systematically assess the expression of SYK, its prognostic value and epigenetic status in different cancers using bioinformatics tools.

Methods:

In this bioinformatics study, Oncomine database and cBioPortal were used to study the SYK gene expression, Kaplan–Meier plotter to study its prognostic value and MethHC to assess the SYK gene methylation in various cancers.

Results:

From 542 unique analyses of the SYK gene, it was found to be overexpressed in bladder, breast and colon cancers but downregulated in leukemia, lymphoma and myeloma. Compared with normal tissues, breast and brain tumors showed an overexpression of the SYK gene, whereas lymphoma and leukemia had lower expression. The Kaplan–Meier survival analysis revealed that SYK expression in pancreatic, gastric, liver and lung patients were correlated with better overall survival. Using cBioPortal, prostate cancer was found to have the highest SYK gene mutation frequency, and the mean expression was highest in diffuse large B-cell lymphoma, acute myeloid leukemia and thymoma. Using the MethHC database, SYK promoter hypermethylation was found to be significantly higher in breast, renal, liver, lung, pancreatic, prostatic, skin and stomach cancers compared with the normal tissue (P < 0.005).

Conclusion:

The results of this study indicate the potential use of SYK as a diagnostic and therapeutic target for different type of cancers. However, further experimental data are required to validate these results before use of SYK in clinical settings.

Inhibition of SYK kinase does not confer a pro-proliferative or pro-invasive phenotype in breast epithelium or breast cancer cells

SYK has been reported to possess both tumour promotor and repressor activities and deletion has been linked to a pro-proliferative / pro-invasive phenotype in breast tumours. It is unclear whether this is a consequence of protein deletion or loss of kinase activity. The SYK inhibitor, BI 1002494, caused no increase in proliferation in breast cancer cells or primary mammary epithelial cells in 2D or 3D cultures, nor changes in proliferation (CD1/2, CDK4, PCNA, Ki67) or invadopodia markers (MMP14, PARP, phospho-vimentin Ser56). BI 1002494 did not alter SYK protein expression. There was no change in phenotype observed in 3D cultures after addition of BI 1002494. Thirteen weeks of treatment with BI 1002494 resulted in no ductal branching or cellular proliferation in the mammary glands of mice. An in silico genetic analysis in breast tumour samples revealed no evidence that SYK has a typical tumour suppressor gene profile such as focal deletion, inactivating mutations or lower expression levels. Furthermore, SYK mutations were not associated with reduction in survival and disease-free period in breast cancer patients. In conclusion, small molecule inhibition of the kinase function of SYK does not contribute to a typical tumour suppressor profile.

QuaDMutNetEx: a method for detecting cancer driver genes with low mutation frequency

BACKGROUND

Cancer is caused by genetic mutations, but not all somatic mutations in human DNA drive the emergence or growth of cancers. While many frequently-mutated cancer driver genes have already been identified and are being utilized for diagnostic, prognostic, or therapeutic purposes, identifying driver genes that harbor mutations occurring with low frequency in human cancers is an ongoing endeavor. Typically, mutations that do not confer growth advantage to tumors - passenger mutations - dominate the mutation landscape of tumor cell genome, making identification of low-frequency driver mutations a challenge. The leading approach for discovering new putative driver genes involves analyzing patterns of mutations in large cohorts of patients and using statistical methods to discriminate driver from passenger mutations.

RESULTS

We propose a novel cancer driver gene detection method, QuaDMutNetEx. QuaDMutNetEx discovers cancer drivers with low mutation frequency by giving preference to genes encoding proteins that are connected in human protein-protein interaction networks, and that at the same time show low deviation from the mutual exclusivity pattern that characterizes driver mutations occurring in the same pathway or functional gene group across a cohort of cancer samples.

CONCLUSIONS

Evaluation of QuaDMutNetEx on four different tumor sample datasets show that the proposed method finds biologically-connected sets of low-frequency driver genes, including many genes that are not found if the network connectivity information is not considered. Improved quality and interpretability of the discovered putative driver gene sets compared to existing methods shows that QuaDMutNetEx is a valuable new tool for detecting driver genes. QuaDMutNetEx is available for download from https://github.com/bokhariy/QuaDMutNetExunder the GNU GPLv3 license.

The Syk Kinase Promotes Mammary Epithelial Integrity and Inhibits Breast Cancer Invasion by Stabilizing the E-Cadherin/Catenin Complex

While first discovered in immunoreceptor signaling, the Syk protein kinase behaves as a tumor and metastasis suppressor in epithelial cells. Its reduced expression in breast and other carcinomas is correlated with decreased survival and increased metastasis risk, but its action mechanism remains largely unknown. Using phosphoproteomics we found that Syk phosphorylated E-cadherin and α-, β-, and p120-catenins on multiple tyrosine residues that concentrate at intercellular junctions. Increased Syk expression and activation enhanced E-cadherin/catenin phosphorylation, promoting their association and complex stability. In human breast cancer cells, Syk stimulated intercellular aggregation, E-cadherin recruitment and retention at adherens junctions, and promoted epithelial integrity, whereas it inhibited cell migration and invasion. Opposite effects were obtained with Syk knockdown or non-phosphorylatable mutant E-cadherin expression. Mechanistically, Syk stimulated the interaction of the E-cadherin/catenin complex with zonula occludens proteins and the actin cytoskeleton. Conditional Syk knockout in the lactating mouse mammary gland perturbed alveologenesis and disrupted E-cadherin localization at adherens junctions, corroborating the observations in cells. Hence, Syk is involved in the maintenance of the epithelial integrity of the mammary gland via the phosphorylation and stabilization of the E-cadherin/catenin adherens junction complex, thereby inhibiting cell migration and malignant tumor invasion.

Cyclin-dependent kinase 1-mediated AMPK phosphorylation regulates chromosome alignment and mitotic progression

AMP-activated protein kinase (AMPK), a heterotrimeric serine/threonine kinase and cellular metabolic sensor, has been found to regulate cell cycle checkpoints in cancer cells in response to energetic stress, to harmonize proliferation with energy availability. Despite AMPK's emergent association with the cell cycle, it still has not been fully delineated how AMPK is regulated by upstream signaling pathways during mitosis. We report, for the first time, direct CDK1 phosphorylation of both the catalytic α1 and α2 subunits, as well as the β1 regulatory subunit, of AMPK in mitosis. We found that AMPK-knockout U2OS osteosarcoma cells have reduced mitotic indexes and that CDK1 phosphorylation-null AMPK is unable to rescue the phenotype, demonstrating a role for CDK1 regulation of mitotic entry through AMPK. Our results also denote a vital role for AMPK in promoting proper chromosomal alignment, as loss of AMPK activity leads to misaligned chromosomes and concomitant metaphase delay. Importantly, AMPK expression and activity was found to be critical for paclitaxel chemosensitivity in breast cancer cells and positively correlated with relapse-free survival in systemically treated breast cancer patients.

Ki-67 and MCM6 labeling indices are correlated with overall survival in anaplastic oligodendroglioma, IDH1-mutant and 1p/19q-codeleted: a multicenter study from the French POLA network

Anaplastic oligodendroglioma (AO), IDH-mutant and 1p/19q codeleted (IDHmut+/1p19qcodel), is a high-grade glioma with only limited prognostic markers. The primary objective of this study was to evaluate, by immunohistochemistry, the prognostic value of two proliferation markers, MCM6 and Ki-67, in a large series of IDHmut+/1p19qcodel AO included in the POLA ("Prise en charge des Oligodendrogliomes Anaplasiques") French national multicenter network. We additionally examined the transcriptome obtained from this series to understand the functional pathways dysregulated with the mRNA overexpression of these two markers. The labeling indices (LI) of MCM6 and Ki-67 were obtained via computer-assisted color image analyses on immunostained AO tissues of the cohort (n = 220). Furthermore, a subgroup of AO (n = 68/220) was used to perform transcriptomic analyses. A high LI of either MCM6 (≥50%) or Ki-67 (≥15%) correlated with shorter overall survival, both in univariate (P = 0.013 and P = 0.004, respectively) and multivariate analyses (P = 0.027; multivariate Cox model including age, mitotic index, MCM6 and Ki-67). MCM6 and Ki-67 LI also correlated with overall survival in an additional retrospective cohort of 30 grade II IDHmut+/1p19qcodel oligodendrogliomas. The prognostic value of MCM6 mRNA level was confirmed in The Cancer Genome Atlas (TCGA) IDHmut+/1p19qcodel gliomas. The transcriptomic approach revealed that high transcriptional expressions of MCM6 and MKI67 were both linked positively with cell cycle progression, DNA replication, mitosis, pro-neural phenotype as well as neurogenesis, and negatively with microglial cell activation, immune response, positive regulation of myelination, oligodendrocyte development, beta-amyloid binding and postsynaptic specialization. In conclusion, the overexpression of MCM6 and/or Ki-67 is independently associated to shorter overall survival in IDHmut+/1p19qcodel AO. These two easy-to-use and cost-effective markers could thus be used concurrently in routine pathology practice. Additionally, the transcriptomic analyses showed that AO with high proliferation index have down-regulated immune response and lower microglial cells activation, and bears pro-neural phenotype.

Classic and Novel Signaling Pathways Involved in Cancer: Targeting the NF-κB and Syk Signaling Pathways

The nuclear factor kappa B (NF-κB) consists of a family of transcription factors involved in the regulation of a wide variety of biological responses. Growing evidence support that NF-κB plays a major role in oncogenesis as well as its well-known function in the regulation of immune responses and inflammation. Therefore, we made a review of the diverse molecular mechanisms by which the NF-κB pathway is constitutively activated in different types of human cancers and the potential role of various oncogenic genes regulated by this transcription factor in cancer development and progression. We also discussed various pharmacological approaches employed to target the deregulated NF-κB signaling pathway and their possible therapeutic potential in cancer therapy. Moreover, Syk (Spleen tyrosine kinase), non-receptor tyrosine kinase which mediates signal transduction downstream of a variety of transmembrane receptors including classical immune-receptors like the B-cell receptor (BCR), which can also activate the inflammasome and NF-κB-mediated transcription of chemokines and cytokines in the presence of pathogens would be discussed as well. The highlight of this review article is to summarize the classic and novel signaling pathways involved in NF-κB and Syk signaling and then raise some possibilities for cancer therapy.

Correlate the TP53 Mutation and the HRAS Mutation with Immune Signatures in Head and Neck Squamous Cell Cancer

Although immunotherapy has emerged as an effective therapeutic strategy for various cancers including head and neck squamous cell carcinomas (HNSCCs), only a subset of patients can benefit from such therapy. Hence, it is pressing to discover predictive biomarkers for cancer immunotherapy response. TP53 and HRAS mutations frequently occur in HNSCC and correlate with a worse prognosis in HNSCC. We extensively characterized the associations of TP53 mutations and HRAS mutations with HNSCC immunity based on multiple cancer genomics datasets. We compared the enrichment levels of 20 immune signatures between TP53-mutated and TP53-wildtype HNSCCs, and between HRAS-mutated and HRAS-wildtype HNSCCs, and found that TP53 mutations were associated with depressed immune signatures while HRAS mutations were associated with enhanced immune signatures in HNSCC. Moreover, we found multiple p53- and RAS-mediated pathways showing significant correlations with HNSCC immunity. Furthermore, we demonstrated that the association between TP53 mutation and tumor immunity was independent of the human papillomavirus (HPV) infection and smoking status in HNSCC. These data suggest that p53 and RAS may play important roles in regulating HNSCC immunity and that the TP53 and HRAS mutation status could be useful biomarkers for stratifying HNSCC patients responsive to immunotherapy.

SYK Inhibition Potentiates the Effect of Chemotherapeutic Drugs on Neuroblastoma Cells in Vitro

Neuroblastoma is a malignancy arising from the developing sympathetic nervous system and the most common and deadly cancer of infancy. New therapies are needed to improve the prognosis for high-risk patients and to reduce toxicity and late effects. Spleen tyrosine kinase (SYK) has previously been identified as a promising drug target in various inflammatory diseases and cancers but has so far not been extensively studied as a potential therapeutic target in neuroblastoma. In this study, we observed elevated SYK gene expression in neuroblastoma compared to neural crest and benign neurofibroma. While SYK protein was detected in the majority of examined neuroblastoma tissues it was less frequently observed in neuroblastoma cell lines. Depletion of SYK by siRNA and the use of small molecule SYK inhibitors significantly reduced the cell viability of neuroblastoma cell lines expressing SYK protein. Moreover, SYK inhibition decreased ERK1/2 and Akt phosphorylation. The SYK inhibitor BAY 61-3606 enhanced the effect of different chemotherapeutic drugs. Transient expression of a constitutive active SYK variant increased the viability of neuroblastoma cells independent of endogenous SYK levels. Collectively, our findings suggest that targeting SYK in combination with conventional chemotherapy should be further evaluated as a treatment option in neuroblastoma.

Expression of Syk and MAP4 proteins in ovarian cancer

Purpose

We have previously reported on the prognostic importance of the calpain family of proteins in ovarian cancer, especially calpain-2. Spleen tyrosine kinase (Syk) phosphorylates a variety of cytoskeletal proteins with studies suggesting potential interactions between Syk and conventional calpains. Microtubule-associated protein 4 (MAP4) has been reported to be regulated by Syk.

Methods

The current study assessed Syk and MAP4 protein expression, by immunohistochemistry on a tissue microarray comprised of cores from primary ovarian carcinomas (n = 575), to evaluate associations with patient clinical outcomes and other clinicopathological factors and sought to determine whether there were any correlations between the expression of Syk, MAP4 and the calpain system.

Results

MAP4 expression was significantly associated with ovarian cancer histological subtype (P < 0.001), stage (P = 0.001), grade (P < 0.001) and residual tumour (P = 0.005). Despite this finding, we found no significant association existing between MAP4 expression and overall survival. Syk expression was also found significantly associated with histological subtype (P < 0.001). Syk seems to play a contradictory role with respect to tumour progression: low cytoplasmic Syk expression was significantly associated with low stage (P = 0.013), and low nuclear Syk expression with chemo-resistance in patients treated with taxane-containing therapy (P = 0.006). Interestingly, despite the lack of association in the whole cohort, high nuclear Syk expression was significantly associated with better overall survival in certain subgroups (P = 0.001).

Conclusions

The current study indicates a lack of correlation between calpain-2 expression and Syk and MAP4. Syk, MAP4 and calpain-1 appeared to significantly correlate with each other in the whole cohort, with calpain-1 being more highly associated with MAP4 and Syk in mucinous carcinomas. Overall, the current results suggest that Syk, MAP4, and calpain-1 expression are correlated with each other and these proteins may be involved in early stages of tumour spread.

Electronic supplementary material

The online version of this article (10.1007/s00432-019-02856-9) contains supplementary material, which is available to authorized users.

SYK inhibition blocks proliferation and migration of glioma cells and modifies the tumor microenvironment

Background

Glioblastoma (GBM) is one of the most aggressive human brain tumors, with a median survival of 15-18 months. There is a desperate need to find novel therapeutic targets. Various receptor protein kinases have been identified as potential targets; however, response rates in clinical studies have been somewhat disappointing. Targeting the spleen tyrosine kinase (SYK), which acts downstream of a range of oncogenic receptors, may therefore show more promising results.

Methods

Kinase expression of brain tumor samples including GBM and low-grade tumors were compared with normal brain and normal human astrocytes by microarray analysis. Furthermore, SYK, LYN, SLP76, and PLCG2 protein expressions were analyzed by immunohistochemistry, western blot, and immunofluorescence of additional GBM patient samples, murine glioma samples, and cell lines. SYK was then blocked chemically and genetically in vitro and in vivo in 2 different mouse models. Multiphoton intravital imaging and multicolor flow cytometry were performed in a syngeneic immunocompetent C57BL/6J mouse GL261 glioma model to study the effect of these inhibitors on the tumor microenvironment.

Results

SYK, LYN, SLP76, and PLCG2 were found expressed in human and murine glioma samples and cell lines. SYK inhibition blocked proliferation, migration, and colony formation. Flow cytometric and multiphoton imaging imply that targeting SYK in vivo attenuated GBM tumor growth and invasiveness and reduced B and CD11b+ cell mobility and infiltration.

Conclusions

Our data suggest that gliomas express a SYK signaling network important in glioma progression, inhibition of which results in reduced invasion with slower tumor progression.

Endocrine Resistance in Hormone Receptor Positive Breast Cancer-From Mechanism to Therapy

The importance and role of the estrogen receptor (ER) pathway has been well-documented in both breast cancer (BC) development and progression. The treatment of choice in women with metastatic breast cancer (MBC) is classically divided into a variety of endocrine therapies, 3 of the most common being: selective estrogen receptor modulators (SERM), aromatase inhibitors (AI) and selective estrogen receptor down-regulators (SERD). In a proportion of patients, resistance develops to endocrine therapy due to a sophisticated and at times redundant interference, at the molecular level between the ER and growth factor. The progression to endocrine resistance is considered to be a gradual, step-wise process. Several mechanisms have been proposed but thus far none of them can be defined as the complete explanation behind the phenomenon of endocrine resistance. Although multiple cellular, molecular and immune mechanisms have been and are being extensively studied, their individual roles are often poorly understood. In this review, we summarize current progress in our understanding of ER biology and the molecular mechanisms that predispose and determine endocrine resistance in breast cancer patients.

Inhibition of ovarian tumor cell invasiveness by targeting SYK in the tyrosine kinase signaling pathway

Cell motility and invasiveness are prerequisites for dissemination, and largely account for cancer mortality. We have identified an actionable kinase, spleen tyrosine kinase (SYK), which is keenly tightly associated with tumor progression in ovarian cancer. Here, we report that active recombinant SYK directly phosphorylates cortactin and cofilin, which are critically involved in assembly and dynamics of actin filament through phosphorylation signaling. Enhancing SYK activity by inducing expression of a constitutively active SYK mutant, SYK130E, increased growth factor-stimulated migration and invasion of ovarian cancer cells, which was abrogated by cortactin knockdown. Similarly, SYK inhibitors significantly decreased invasion of ovarian cancer cells across basement membrane in real-time transwell assays and in 3D tumor spheroid models. SYK inactivation by targeted gene knockout or by small molecule inhibition reduced actin polymerization. Collectively, this study reported a new mechanism by which SYK signaling regulates ovarian cancer cell motility and invasiveness, and suggest a target-based strategy to prevent or suppress the advancement of ovarian malignancies.

Spleen Tyrosine Kinase as a Target Therapy for Pseudomonas aeruginosa Infection

Spleen tyrosine kinase (SYK) is a nonreceptor tyrosine kinase which associates directly with extracellular receptors, and is critically involved in signal transduction pathways in a variety of cell types for the regulation of cellular responses. SYK is expressed ubiquitously in immune and nonimmune cells, and has a much wider biological role than previously recognized. Several studies have highlighted SYK as a key player in the pathogenesis of a multitude of diseases. Pseudomonas aeruginosa is an opportunistic gram-negative pathogen, which is responsible for systemic infections in immunocompromised individuals, accounting for a major cause of severe chronic lung infection in cystic fibrosis patients and subsequently resulting in a progressive deterioration of lung function. Inhibition of SYK activity has been explored as a therapeutic option in several allergic disorders, autoimmune diseases, and hematological malignancies. This review focuses on SYK as a therapeutic target, and describes the possibility of how current knowledge could be translated for therapeutic purposes to regulate the immune response to the opportunistic pathogen P. aeruginosa.

Prognostic value of spleen tyrosine kinase in human solid tumors

Background

Spleen tyrosine kinase (SYK) was reported to be dysregulated in solid tumors and played an important role in cancer progression. However, the clinical and prognostic values of SYK in solid tumors remain unclear. This meta-analysis investigated the association between SYK expression and clinical outcomes in the patients with solid tumors.

Methods

A comprehensive literature search was conducted by screening the online electronic databases of PubMed, Embase, and the China National Knowledge Infrastructure. The hazard ratio (HR) with its corresponding 95% CI was used to explore the prognostic value of SYK.

Results

We analyzed a total of 1,075 patients from 10 studies, which met the criteria for this meta-analysis. Our pooled results demonstrated that a low expression of SYK did not correlate significantly with shorter overall survival (OS; HR=0.64, 95% CI: 0.34-1.21, P=0.169) or poorer disease-free survival (HR=0.51, 95% CI: 0.13-2.02, P=0.338). However, in a subgroup analysis based on tumor type and test method, under-expression of SYK was positively associated with worse OS in the groups of breast cancer (BC; HR=0.51, 95% CI: 0.32-0.80, P=0.003), hepatocellular carcinoma (HCC; HR=0.44, 95% CI: 0.29-0.69, P<0.001), methylation (HR=0.39, 95% CI: 0.30-0.51, P<0.001), and quantitative reverse transcription polymerase chain reaction (HR=0.24, 95% CI: 0.09-0.65, P=0.005).

Conclusion

This meta-analysis demonstrated that under-expression of SYK may serve as a predictive biomarker for poor prognosis in BC and HCC patients. In other solid tumors, the clinical usefulness should be confirmed by large-scale studies.

SYK expression level distinguishes control from BRCA1-mutated lymphocytes

Background

About 5%-10% of breast cancer and 10%-15% of ovarian cancer are hereditary. BRCA1 and BRCA2 are the most common germline mutations found in both inherited breast and ovarian cancers. Once these mutations are identified and classified, a course of action to reduce the risk of developing either ovarian or breast cancer - including surveillance and surgery - is carried out.

Purpose

The purpose of the current research is to characterize the gene expression differences between healthy cells harboring a mutation in BRCA1/2 genes and normal cells. This will allow detection of candidate genes and help identify women who carry functional BRCA1/2 mutations, which cannot always be detected by the available sequencing methods, for example, carriers of mutations found in regulatory sequences of the genes.

Materials and methods

Our cohort consisted of 50 healthy women, of whom 24 were individuals with BRCA1 or BRCA2 heterozygous mutations and 26 were non-carrier controls. RNA purified from non-irradiated lymphocytes of nine BRCA1/2 mutation carriers versus four control mutation-negative individuals was utilized for RNA-Seq analysis. The selected RNA-Seq transcripts were validated, and the levels of spleen tyrosine kinase (SYK) mRNA were measured by using real-time quantitative polymerase chain reaction.

Results

Differences in gene expression were found when comparing untreated lymphocytes of BRCA1/2 mutation carriers and controls. Among others, the SYK gene was identified as being differently expressed for BRCA1/2 mutation carriers. The expression level of SYK was significantly higher in untreated healthy lymphocytes of BRCA1 heterozygote carriers compared with controls, regardless of irradiation. In contrast to normal tissues, in cancerous breast tissues, the expression levels of the BRCA1 and SYK genes were not intercorrelated.

Conclusion

Collectively, our observations demonstrate that SYK may prove to be a good candidate for better diagnosis, treatment, and prevention of BRCA1 mutation-associated breast cancer.

Phosphorylated immunoreceptor tyrosine-based activation motifs and integrin cytoplasmic domains activate spleen tyrosine kinase via distinct mechanisms

Spleen tyrosine kinase (Syk) is involved in cellular adhesion and also in the activation and development of hematopoietic cells. Syk activation induced by genomic rearrangement has been linked to certain T-cell lymphomas, and Syk inhibitors have been shown to prolong survival of patients with B-cell lineage malignancies. Syk is activated either by its interaction with a double-phosphorylated immunoreceptor tyrosine-based activation motif (pITAM), which induces rearrangements in the Syk structure, or by the phosphorylation of specific tyrosine residues. In addition to its immunoreceptor function, Syk is activated downstream of integrin pathways, and integrins bind to the same region in Syk as does pITAM. However, it is unknown whether integrins and pITAM use the same mechanism to activate Syk. Here, using purified Syk protein and fluorescence-based enzyme assay we investigated whether interaction of the integrin β₃ cytoplasmic domain with the Syk regulatory domain causes changes in Syk activity similar to those induced by pITAM peptides. We observed no direct Syk activation by soluble integrin peptide, and integrin did not compete with pITAM-induced activation even though at high concentrations, the integrin cytoplasmic domain peptide competed with Syk's substrate. However, clustered integrin peptides induced Syk activation, presumably via a transphosphorylation mechanism. Moreover, the clustered integrins also activated a Syk variant in which tyrosines were replaced with phenylalanine (Y348F/Y352F), indicating that clustered integrin-induced Syk activation involved other phosphorylation sites. In conclusion, integrin cytoplasmic domains do not directly induce Syk conformational changes and do not activate Syk via the same mechanism as pITAM.

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

AIMS

Calcium 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 RESULTS

Using 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.

CONCLUSIONS

CaP 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.

Prediction of early-stage hepatocellular carcinoma using OncoScan chromosomal copy number aberration data

AIM

To identify chromosomal copy number aberrations (CNAs) in early-stage hepatocellular carcinoma (HCC) and analyze whether they are correlated with patient prognosis.

METHODS

One hundred and twenty patients with early-stage HCC were enrolled in our study, with the collection of formalin fixed, paraffin-embedded (FFPE) specimens and clinicopathological data. Tumor areas were marked by certified pathologists on a hematoxylin and eosin-stained slide, and cancer and adjacent non-cancerous tissues underwent extraction of DNA, which was analyzed with the Affymetrix OncoScan platform to assess CNAs and loss of heterozygosity (LOH). Ten individuals with nonmalignant disease were used as the control group. Another cohort consisting of 40 patients with stage I/II HCC were enrolled to analyze gene expression and to correlate findings with the OncoScan data.

RESULTS

Copy number amplifications occurred at chromosomes 1q21.1-q44 and 8q12.3-24.3 and deletions were found at 4q13.1-q35.2, 8p 23.2-21.1, 16q23.3-24.3, and 17p13.3-12, while LOH commonly occurred at 1p32.3, 3p21.31, 8p23.2-21.1, 16q22.1-24.3, and 17p 13.3-11 in early-stage HCC. Using Cox regression analysis, we also found that a higher percentage of genome change (≥ 60%) was an independent factor for worse prognosis in early-stage HCC (P = 0.031). Among the 875 genes in the OncoScan GeneChip, six were independent predictors of worse disease-free survival, of which three were amplified (MYC, ELAC2, and SYK) and three were deleted (GAK, MECOM, and WRN). Further, patients with HCC who exhibited ≥ 3 CNAs involving these six genes have worse outcomes compared to those who had < 3 CNAs (P < 0.001). Similarly, Asian patients with stage I HCC from The Cancer Genome Atlas harboring CNAs with these genes were also predicted to have poorer outcomes.

CONCLUSION

Patients with early-stage HCC and increased genome change or CNAs involving MYC, ELAC2, SYK, GAK, MECOM, or WRN are at risk for poorer outcome after resection.

Activated spleen tyrosine kinase promotes malignant progression of oral squamous cell carcinoma via mTOR/S6 signaling pathway in an ERK1/2-independent manner

Spleen tyrosine kinase (SYK), a non-receptor cytoplasmic tyrosine enzyme, is well known for its ability in certain pathways through immune receptors. Recently, SYK role in cancer has been widely studied. SYK plays a dual role as a tumor suppressor and tumor promoter. Nevertheless, its role in oral squamous cell carcinoma (OSCC) has not been fully investigated. In the current study, samples from OSCC tumors and adjacent normal counterparts were collected and SYK expression was evaluated by real-time qPCR. SYK mRNA expression in tumors was higher than the normal tissues. And high SYK expression was confirmed by immunohistochemistry analysis and closely related to worse overall survival. The expression of SYK mRNA and protein was detected in 2 of 4 OSCC cell lines. SYK pharmacological suppression and RNAi-mediated knockdown inhibited proliferation, migration, and invasion of SYK-positive cells by reducing phosphorylated ERK1/2 and mTOR levels. One inhibitor of MEK, PD98059, also suppressed the same cancer-associated phenotypes of SYK-positive cells by decreasing phosphorylated ERK1/2 but increasing phosphorylated mTOR. Piceatannol, one pharmacological inhibitor of SYK, attenuated tumor growth in vivo. Overall, our results revealed a novel mechanism triggered by SYK to increase OSCC tumoriogenesis and tumor progression.

Molecular mechanisms of breast cancer metastasis by gene expression profile analysis

Metastasis is the main cause of breast cancer‑related mortalities. The present study aimed to uncover the relevant molecular mechanisms of breast cancer metastasis and to explore potential biomarkers that may be used for prognosis. Expression profile microarray data GSE8977, which contained 22 stroma samples (15 were from normal breast and 7 were from invasive ductal carcinoma tumor samples), were obtained from the Gene Expression Omnibus database. Following data preprocessing, differentially expressed genes (DEGs) were selected based on analyses conducted using the linear models for microarray analysis package from R and Bioconductor software. The resulting data were used in subsequent function and pathway enrichment analyses, as well as protein‑protein interaction (PPI) network and subnetwork analyses. Transcription factors (TFs) and tumor‑associated genes were also identified among the DEGs. A total of 234 DEGs were identified, which were enriched in immune response, cell differentiation and cell adhesion‑related functions and pathways. Downregulated DEGs included TFs, such as the proto‑oncogene SPI1, pre‑B‑cell leukemia homeobox 3 (PBX3) and lymphoid enhancer‑binding factor 1 (LEF1), as well as tumor suppressors (TSs), such as capping actin protein, gelsolin like (CAPG) and tumor protein p53‑inducible nuclear protein 1 (TP53INP1). Upregulated DEGs also included TFs and tumor suppressors, consisting of transcription factor 7‑like 2 (TCF7L2) and pleiomorphic adenoma gene‑like 1 (PLAGL1). DEGs that were identified at the hub nodes in the PPI network and the subnetwork were epidermal growth factor receptor (EGFR) and spleen‑associated tyrosine kinase (SYK), respectively. Several genes crucial in the metastasis of breast cancer were identified, which may serve as potential biomarkers, many of which were associated with cell adhesion, proliferation or immune response, and may influence breast cancer metastasis by regulating these function or pathways.

Reconstruction and signal propagation analysis of the Syk signaling network in breast cancer cells

The ability to build in-depth cell signaling networks from vast experimental data is a key objective of computational biology. The spleen tyrosine kinase (Syk) protein, a well-characterized key player in immune cell signaling, was surprisingly first shown by our group to exhibit an onco-suppressive function in mammary epithelial cells and corroborated by many other studies, but the molecular mechanisms of this function remain largely unsolved. Based on existing proteomic data, we report here the generation of an interaction-based network of signaling pathways controlled by Syk in breast cancer cells. Pathway enrichment of the Syk targets previously identified by quantitative phospho-proteomics indicated that Syk is engaged in cell adhesion, motility, growth and death. Using the components and interactions of these pathways, we bootstrapped the reconstruction of a comprehensive network covering Syk signaling in breast cancer cells. To generate in silico hypotheses on Syk signaling propagation, we developed a method allowing to rank paths between Syk and its targets. We first annotated the network according to experimental datasets. We then combined shortest path computation with random walk processes to estimate the importance of individual interactions and selected biologically relevant pathways in the network. Molecular and cell biology experiments allowed to distinguish candidate mechanisms that underlie the impact of Syk on the regulation of cortactin and ezrin, both involved in actin-mediated cell adhesion and motility. The Syk network was further completed with the results of our biological validation experiments. The resulting Syk signaling sub-networks can be explored via an online visualization platform.

Label-free fingerprinting of tumor cells in bulk flow using inline digital holographic microscopy

Large-scale and label-free phenotyping of cells holds great promise in medicine, especially in cancer diagnostics and prognosis. Here, we introduce inline digital holography microscopy for volumetric imaging of cells in bulk flow and fingerprinting of flowing tumor cells based on two metrics, in-focus scattered intensity and cell diameter. Using planar distribution of immobilized particles, we identify the optimal recording distance and microscope objective magnification that minimizes the error in measurement of particle position, size and scattered intensity. Using the optimized conditions and the two metrics, we demonstrate the capacity to enumerate and fingerprint more than 100,000 cells. Finally, we highlight the power of our label-free and high throughput technology by characterizing breast tumor cell lines with different metastatic potentials and distinguishing drug resistant ovarian cancer cells from their parental cell line.

Central role of PI3K-SYK interaction in fibrinogen-induced lamellipodia and filopodia formation in platelets

The WAVE complex‐1, a complex of WAVE, Abi1, NAP1, PIR121, HSPC300, RacGTP and Arp2/3 proteins, and WASP complex‐1, a complex of WASP, Cdc42, PIP2, and Arp2/3 proteins, are involved in lamellipodia and filopodia formation, respectively. It is known that the two complexes have opposite dynamics. Furthermore, Rac has two guanine nucleotide exchange factors, Vav and Sos, whose role in activating Rac is not well understood. In this work, by the construction of signaling network, analysis, and mathematical modeling, I show that Sos generates a pulse of WAVE complex‐1, decreasing the response time of WAVE complex‐1 formation upon the stimulation of platelets by fibrinogen. Furthermore, I also show that the dynamics of WAVE and WASP complexes depends on PI3K–SYK interaction. In the absence of this interaction, the WAVE complex‐1 does not form and the WASP complex‐1 remains at the initial, sustained level. Thus, I show the significance of the two protein/protein complexes: Sos and PI3K–SYK interaction, in fibrinogen‐induced lamellipodia and filopodia formation in platelets.

HSP90 promotes Burkitt lymphoma cell survival by maintaining tonic B-cell receptor signaling

Burkitt lymphoma (BL) is an aggressive B-cell neoplasm that is currently treated by intensive chemotherapy in combination with anti-CD20 antibodies. Because of their toxicity, current treatment regimens are often not suitable for elderly patients or for patients in developing countries where BL is endemic. Targeted therapies for BL are therefore needed. In this study, we performed a compound screen in 17 BL cell lines to identify small molecule inhibitors affecting cell survival. We found that inhibitors of heat shock protein 90 (HSP90) induced apoptosis in BL cells in vitro at concentrations that did not affect normal B cells. By global proteomic and phosphoproteomic profiling, we show that, in BL, HSP90 inhibition compromises the activity of the pivotal B-cell antigen receptor (BCR)-proximal effector spleen tyrosine kinase (SYK), which we identified as an HSP90 client protein. Consistently, expression of constitutively active TEL-SYK counteracted the apoptotic effect of HSP90 inhibition. Together, our results demonstrate that HSP90 inhibition impairs BL cell survival by interfering with tonic BCR signaling, thus providing a molecular rationale for the use of HSP90 inhibitors in the treatment of BL.

Alternative splicing of spleen tyrosine kinase differentially regulates colorectal cancer progression

Spleen tyrosine kinase (SYK) has been reported as a potential tumor suppressor in colorectal cancer (CRC). However, the role of alternative splicing of SYK in carcinogenesis remains unclear. In the present study, SYK isoforms were overexpressed in the human CRC HCT 116 cell line using lentiviral expression vectors to investigate the biological functions of full length SYK [SYK(L)] and short form SYK [SYK(S)] in CRC. Real-time cellular analysis and the 5-ethynyl-2-deoxyuridine assay were used to detect the effects of SYK(L) and SYK(S) on cell proliferation. Cell cycle progression and migration were assessed via flow cytometry and Transwell assays, respectively. The results revealed that the recombinant lentivirus with SYK(L) overexpression significantly suppressed the proliferation and metastasis of CRC cells, while SYK(S) overexpression did not. In addition, MTS assays demonstrated that SYK(L) and SYK(S) increased the cellular sensitivity to 5-fluorouracil (5-FU), suggesting that SYK(L) and 5-FU produce a significant synergistic effect on CRC cell proliferation, while SYK(S) has an effect on modulating CRC 5-FU sensitivity. Furthermore, quantitative polymerase chain reaction results revealed that SYK(L) was downregulated in 69% of 26 pairs of CRC and adjacent non-cancerous tissues, whereas SYK(S) exhibited no significant differences between tumor and normal tissues. Overall, the present data provides evidence that SYK(L) is a tumor suppressor in CRC, and both SYK(L) and SYK(S) may serve as important predictors in the chemotherapeutic treatment of CRC.

The TRAF-interacting protein (TRAIP) is a novel E2F target with peak expression in mitosis

The TRAF-interacting protein (TRAIP) is an E3 ubiquitin ligase required for cell proliferation. TRAIP mRNA is downregulated in human keratinocytes after inhibition of the PI3K/AKT/mTOR signaling. Since E2F transcription factors are downstream of PI3K/AKT/mTOR we investigated whether they regulate TRAIP expression. E2F1 expression significantly increased the TRAIP mRNA level in HeLa cells. Reporter assays with the 1400bp 5′-upstream promoter in HeLa cells and human keratinocytes showed that E2F1-, E2F2- and E2F4-induced upregulation of TRAIP expression is mediated by 168bp upstream of the translation start site. Mutating the E2F binding site within this fragment reduced the E2F1- and E2F2-dependent promoter activities and protein-DNA complex formation in gel shift assays. Abundance of TRAIP mRNA and protein was regulated by the cell cycle with a peak in G2/M. Expression of GFP and TRAIP-GFP demonstrated that TRAIP-GFP protein has a lower steady-state concentration than GFP despite similar mRNA levels. Cycloheximide inhibition experiments indicated that the TRAIP protein has a half-life of around four hours. Therefore, the combination of cell cycle-dependent transcription of the TRAIP gene by E2F and rapid protein degradation leads to cell cycle-dependent expression with a maximum in G2/M. These findings suggest that TRAIP has important functions in mitosis and tumorigenesis.

DNA methylation and breast tumor clinicopathological features: The Western New York Exposures and Breast Cancer (WEB) study

We evaluated the association between methylation of 9 genes, SCGB3A1, GSTP1, RARB, SYK, FHIT, CDKN2A, CCND2, BRCA1, and SFN in tumor samples from 720 breast cancer cases with clinicopathological features of the tumors and survival. Logistic regression was used to estimate odds ratios (OR) of methylation and Cox proportional hazards models to estimate hazard ratios (HR) between methylation and breast cancer related mortality. Estrogen receptor (ER) and progesterone receptor (PR) positivity were associated with increased SCGB3A1 methylation among pre- and post-menopausal cases. Among premenopausal women, compared with Stage 0 cases, cases of invasive cancer were more likely to have increased methylation of RARB (Stage I OR = 4.7, 95% CI: 1.1-19.0; Stage IIA/IIB OR = 9.7, 95% CI: 2.4-39.9; Stage III/IV OR = 5.6, 95% CI: 1.1-29.4) and lower methylation of FHIT (Stage I OR = 0.2, 95% CI: 0.1-0.9; Stage IIA/IIB OR = 0.2, 95% CI: 0.1-0.8; Stage III/IV OR = 0.6, 95% CI: 0.1-3.4). Among postmenopausal women, methylation of SYK was associated with increased tumor size (OR = 1.7, 95% CI: 1.0-2.7) and higher nuclear grade (OR = 2.0, 95% CI 1.2-3.6). Associations between methylation and breast cancer related mortality were observed among pre- but not post-menopausal women. Methylation of SCGB3A1 was associated with reduced risk of death from breast cancer (HR = 0.41, 95% CI: 0.17-0.99) as was BRCA1 (HR = 0.41, 95% CI: 0.16-0.97). CCND2 methylation was associated with increased risk of breast cancer mortality (HR = 3.4, 95% CI: 1.1-10.5). We observed differences in methylation associated with tumor characteristics; methylation of these genes was also associated with breast cancer survival among premenopausal cases. Understanding of the associations of DNA methylation with other clinicopathological features may have implications for prevention and treatment.

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.

Spleen tyrosine kinase induces MUC5AC expression in human airway epithelial cell

BACKGROUND

MUC5AC, a major secreted mucin, is increased in chronic inflammatory airway disease. Spleen tyrosine kinase (SYK) is a mediator, which acts as an important regulator of intracellular signal transduction in the inflammatory response. SYK was originally identified in hematopoietic cells, and its expression in some nonhematopoietic cells, including respiratory epithelial cells, was recently demonstrated. However, the effects of SYK on mucin secretion in human airway epithelial cells have not been studied. The objective of this study was to investigate the effect and brief signaling pathways of SYK on MUC5AC expression in human airway epithelial cells.

METHODS

In mucin-producing human NCI-H292 cells and primary cultures of human nasal epithelial cells, the effects and signaling pathways of SYK on MUC5AC expression were investigated by reverse transcriptase-polymerase chain reaction, real-time polymerase chain reaction, enzyme immunoassay, and immunoblot analysis with several specific inhibitors and small interfering RNA (siRNA).

RESULTS

SYK induced MUC5AC expression. SYK activated significant phosphorylation of extracellular signal-related kinase (ERK)1/2 and p38 mitogen-activated protein kinase (MAPK) signaling pathways. SYK-induced MUC5AC expression was significantly attenuated by pretreatment with U0126 (ERK1/2 MAPK inhibitor) and SB203580 (p38 MAPK inhibitor). In addition, the knockdown of ERK2 and p38 MAPK by ERK2 and p38 MAPK siRNA significantly blocked SYK-induced MUC5AC expression.

CONCLUSION

These results indicated that SYK increased MUC5AC expression via ERK2 and p38 MAPK signaling pathways in human airway epithelial cells.

Insights into the allosteric regulation of Syk association with receptor ITAM, a multi-state equilibrium

The phosphorylation of interdomain A (IA), a linker region between tandem SH2 domains of Syk tyrosine kinase, regulates the binding affinity for association of Syk with doubly-phosphorylated ITAM regions of the B cell receptor. The mechanism of this allosteric regulation has been suggested to be a switch from the high-affinity bifunctional binding, mediated through both SH2 domains binding two phosphotyrosine residues of ITAM, to a substantially lower-affinity binding of only one SH2 domain. IA phosphorylation triggers the switch by inducing disorder in IA and weakening the SH2-SH2 interaction. The postulated switch to a single-SH2-domain binding mode is examined using NMR to monitor site-specific binding to each SH2 domain of Syk variants engineered to have IA regions that differ in conformational flexibility. The combined analysis of titration curves and NMR line-shapes provides sufficient information to determine the energetics of inter-molecular binding at each SH2 site along with an intra-molecular binding or isomerization step. A less favorable isomerization equilibrium associated with the changes in the SH2-SH2 conformational ensemble and IA flexibility accounts for the inhibition of Syk association with membrane ITAM regions when IA is phosphorylated, and refutes the proposed switch to single-SH2-domain binding. Syk localizes in the cell through its SH2 interactions, and this basis for allosteric regulation of ITAM association proposes for the first time a phosphorylation-dependent model to regulate Syk binding to alternate receptors and other signaling proteins that differ either in the number of residues separating ITAM phosphotyrosines or by having only one phosphotyrosine, a half ITAM.