Role of STATs as downstream signal transducers in Src family kinase-mediated tumorigenesis

Development of FRET Biosensor to Characterize CSK Subcellular Regulation

C-terminal Src kinase (CSK) is the major inhibitory kinase for Src family kinases (SFKs) through the phosphorylation of their C-tail tyrosine sites, and it regulates various types of cellular activity in association with SFK function. As a cytoplasmic protein, CSK needs be recruited to the plasma membrane to regulate SFKs' activity. The regulatory mechanism behind CSK activity and its subcellular localization remains largely unclear. In this work, we developed a genetically encoded biosensor based on fluorescence resonance energy transfer (FRET) to visualize the CSK activity in live cells. The biosensor, with an optimized substrate peptide, confirmed the crucial Arg107 site in the CSK SH2 domain and displayed sensitivity and specificity to CSK activity, while showing minor responses to co-transfected Src and Fyn. FRET measurements showed that CSK had a relatively mild level of kinase activity in comparison to Src and Fyn in rat airway smooth muscle cells. The biosensor tagged with different submembrane-targeting signals detected CSK activity at both non-lipid raft and lipid raft microregions, while it showed a higher FRET level at non-lipid ones. Co-transfected receptor-type protein tyrosine phosphatase alpha (PTPα) had an inhibitory effect on the CSK FRET response. The biosensor did not detect obvious changes in CSK activity between metastatic cancer cells and normal ones. In conclusion, a novel FRET biosensor was generated to monitor CSK activity and demonstrated CSK activity existing in both non-lipid and lipid raft membrane microregions, being more present at non-lipid ones.

Enantiomer-Dependent Supramolecular Immunosuppressive Modulation for Tissue Reconstruction

Modulating the properties of biomaterials in terms of the host immune response is critical for tissue repair and regeneration. However, it is unclear how the preference for the cellular microenvironment manipulates the chiral immune responses under physiological or pathological conditions. Here, we reported that in vivo and in vitro oligopeptide immunosuppressive modulation was achieved by manipulation of macrophage polarization using chiral tetrapeptide (Ac-FFFK-OH, marked as FFFK) supramolecular polymers. The results suggested that chiral FFFK nanofibers can serve as a defense mechanism in the restoration of tissue homeostasis by upregulating macrophage M2 polarization via the Src-STAT6 axis. More importantly, transiently acting STAT6, insufficient to induce a sustained polarization program, then passes the baton to EGR2, thereby continuously maintaining the M2 polarization program. It is worth noting that the L-chirality exhibits a more potent effect in inducing macrophage M2 polarization than does the D-chirality, leading to enhanced tissue reconstruction. These findings elucidate the crucial molecular signals that mediate chirality-dependent supramolecular immunosuppression in damaged tissues while also providing an effective chiral supramolecular strategy for regulating macrophage M2 polarization and promoting tissue injury repair based on the self-assembling chiral peptide design.

Ropivacaine inhibits the proliferation and metastasis of gastric cancer cells via the SNX10/SRC/STAT3 pathway

Gastric cancer currently has no effective treatment due to its high metastasis and heterogeneity. It has been reported that ropivacaine (Rop) can inhibit the growth, migration, and invasion of gastric cancer. However, the therapeutic mechanism of Rop still needs to be further explored to provide insights for its clinical application. This study aimed to explore the effects of Rop on the growth, migration, and invasion of gastric cancer cells and the underlying mechanisms. The expression levels of SNX10 were assessed in gastric cancer tissues and cell line AGS by qRT-PCR. Cell Counting Kit-8 (CCK8) assay, wound-healing assay, and transwell assay were then used to examine the effects of Rop on the AGS cell viability, migration, invasion, and proliferation, respectively. Additionally, colony formation assay was used to measure cell proliferation ability, and flow cytometry was used to detect apoptosis level. Protein levels of SNX10, SRC, and STAT3 were detected by western blot. According to the experimental results, the decreased SNX10 mRNA expression was observed in gastric cancer tissue and cell line AGS. Rop inhibited the proliferation, migration, and invasion of AGS cells, but promoted apoptosis and upregulated SNX10 expression. Moreover, Rop inhibited the expression of MMP-2 and MMP-9, phosphorylation of SRC and STAT3. SNX10 knockdown could reverse Rop-induced anticancer effects. Collectively, Rop showed a potential role in preventing proliferation and metastasis of gastric cancer. The action mechanism of Rop may be related to the upregulation of SNX10 expression and further inhibition of SRC/STAT3 signaling pathway. Our findings provide new insights into the anticancer properties of Rop.

The Role of Inflammation-Associated Factors in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC), which originates in the head or neck tissues, is characterized by high rates of recurrence and metastasis. Inflammation is important in HNSCC prognosis. Inflammatory cells and their secreted factors contribute to the various stages of HNSCC development through multiple mechanisms. In this review, the mechanisms through which inflammatory factors, signaling pathways, and cells contribute to the initiation and progression of HNSCC have been discussed in detail. Furthermore, the diagnostic and therapeutic potential of targeting inflammation in HNSCC has been discussed to gain new insights into improving patient prognosis.

Investigating regulated signaling pathways in therapeutic targeting of non-small cell lung carcinoma

Non-small cell lung carcinoma (NSCLC) is the most common malignancy worldwide. The signaling cascades are stimulated via genetic modifications in upstream signaling molecules, which affect apoptotic, proliferative, and differentiation pathways. Dysregulation of these signaling cascades causes cancer-initiating cell proliferation, cancer development, and drug resistance. Numerous efforts in the treatment of NSCLC have been undertaken in the past few decades, enhancing our understanding of the mechanisms of cancer development and moving forward to develop effective therapeutic approaches. Modifications of transcription factors and connected pathways are utilized to develop new treatment options for NSCLC. Developing designed inhibitors targeting specific cellular signaling pathways in tumor progression has been recommended for the therapeutic management of NSCLC. This comprehensive review provided deeper mechanistic insights into the molecular mechanism of action of various signaling molecules and their targeting in the clinical management of NSCLC.

Pulsed electric fields stimulate microglial transmitter release of VEGF, IL-8 and GLP-1 and activate endothelial cells through paracrine signaling

As action potentials propagate along an axon, pulsed extracellular electric fields (E-fields) are induced. We investigated the role of E-fields in activating microglia cells and affecting capillary function and found that E-fields control human microglia secretions in concert with purinergic factors. We generated E-fields by applying transcranial pulsed electromagnetic fields (T-PEMF) identical to those appearing outside neurons as action potentials propagate. T-PEMF alone enhanced mRNA synthesis for VEGF, IL-8, IL-6 and the proglucagon gene as well as the PC1/3 enzyme that cleaves the proglucagon protein to glucagon and GLP-1 proteins. We found that T-PEMF enhanced secretion from microglia of VEGF, IL-8 and GLP-1 proteins having angiogenic and proliferative profiles. Interestingly, T-PEMF and purinergic transmitters together enhanced secretions confirming synergy between their actions. ATP also induced nitric oxide (NO) syntheses in distinct locations in the nucleus and the mRNA synthesis for the responsible iNOS was reduced by T-PEMF. When the microglia-secretory fluid was added to brain endothelial cells we saw vivid Ca²⁺ signaling and enhanced transcription of mRNA for IL-8 and VEGF. Our previous work shows that applying T-PEMF to the human brain provides up to 60% remission for patients with refractory depressions within 8 weeks and improvements for Parkinson patients. Thus, physiological E-fields activate microglia, work synergistically with neurotransmitters, and cause paracrine secretions which cause activation of capillaries. Application of these E-Fields is effective for treating refractory depressions and appear promising for treating neurodegenerative brain diseases.

A reversible SRC-relayed COX2 inflammatory program drives resistance to BRAF and EGFR inhibition in BRAFV600E colorectal tumors

BRAF^V600E mutation confers a poor prognosis in metastatic colorectal cancer (CRC) despite combinatorial targeted therapies based on the latest understanding of signaling circuitry. To identify parallel resistance mechanisms induced by BRAF-MEK-EGFR co-targeting, we used a high-throughput kinase activity mapping platform. Here we show that SRC kinases are systematically activated in BRAF^V600E CRC following targeted inhibition of BRAF ± EGFR and that coordinated targeting of SRC with BRAF ± EGFR increases treatment efficacy in vitro and in vivo. SRC drives resistance to BRAF ± EGFR targeted therapy independently of ERK signaling by inducing transcriptional reprogramming through β-catenin (CTNNB1). The EGFR-independent compensatory activation of SRC kinases is mediated by an autocrine prostaglandin E₂ loop that can be blocked with cyclooxygenase-2 (COX2) inhibitors. Co-targeting of COX2 with BRAF + EGFR promotes durable suppression of tumor growth in patient-derived tumor xenograft models. COX2 inhibition represents a drug-repurposing strategy to overcome therapeutic resistance in BRAF^V600E CRC.

The STAT family: Key transcription factors mediating crosstalk between cancer stem cells and tumor immune microenvironment

Signal transducer and activator of transcription (STAT) proteins compose a family of transcription factors critical for cancer stem cells (CSCs), and they are involved in maintaining stemness properties, enhancing cell proliferation, and promoting metastasis. Recent studies suggest that STAT proteins engage in reciprocal communication between CSCs and infiltrate immune cell populations in the tumor microenvironment (TME). Emerging evidence has substantiated the influence of immune cells, including macrophages, myeloid-derived suppressor cells, and T cells, on CSC survival through the regulation of STAT signaling. Conversely, dysregulation of STATs in CSCs or immune cells contributes to the establishment of an immunosuppressive TME. Thus, STAT proteins are promising therapeutic targets for cancer treatment, especially when used in combination with immunotherapy. From this perspective, we discuss the complex roles of STATs in CSCs and highlight their functions in the crosstalk between CSCs and the immune microenvironment. Finally, cutting-edge clinical trial progress with STAT signaling inhibitors is summarized.

Extracellular vesicles from focal segmental glomerulosclerosis pediatric patients induce STAT3 activation and mesangial cell proliferation

Introduction

Primary focal segmental glomerulosclerosis (FSGS), a major cause of end-stage kidney disease (ESKD) in adolescents and young adults, is attributable to recognized genetic mutations in a minority of cases. For the majority with idiopathic primary FSGS, the cause of the disease is unknown. We hypothesize that extracellular vesicle (EVs), that carry information between podocytes and mesangial cells, may play a key role in disease progression.

Material & methods

A total of 30 participants (20 primary nephrotic syndrome/ 10 healthy controls) were enrolled in this study. Primary nephrotic syndrome subjects were grouped based on pathologic diagnosis. The FSGS group was compared to healthy control subjects based on demographic and clinical findings. EVs were isolated from the urine of each group before being characterized by Western blotting, transmission electron microscopy, and nanoparticle tracking analysis. The effects of the EVs from each group on normal human mesangial cells and activation of certain pathways were then investigated.

Results

Based on demographic and clinical findings, mean serum creatinine was significantly higher in the FSGS group than the normal healthy control group. The mean size of the EVs in the FSGS group was significantly higher than the healthy control group. The mesangial cells that were challenged with EVs isolated from FSGS patients showed significant upregulation of STAT-3, PCNA, Ki67, and cell proliferation.

Discussion

Our data demonstrate that EVs from FSGS patients stimulate mesangial cell proliferation in association with upregulation of the phospho-STAT-3 pathway. Additional studies are planned to identify the molecular cargo within the EVs from FSGS patients that contribute to the pathogenesis of FSGS.

Emerging therapies for autosomal dominant polycystic kidney disease with a focus on cAMP signaling

Autosomal dominant polycystic kidney disease (ADPKD), with an estimated genetic prevalence between 1:400 and 1:1,000 individuals, is the third most common cause of end stage kidney disease after diabetes mellitus and hypertension. Over the last 3 decades there has been great progress in understanding its pathogenesis. This allows the stratification of therapeutic targets into four levels, gene mutation and polycystin disruption, proximal mechanisms directly caused by disruption of polycystin function, downstream regulatory and signaling pathways, and non-specific pathophysiologic processes shared by many other diseases. Dysfunction of the polycystins, encoded by the PKD genes, is closely associated with disruption of calcium and upregulation of cyclic AMP and protein kinase A (PKA) signaling, affecting most downstream regulatory, signaling, and pathophysiologic pathways altered in this disease. Interventions acting on G protein coupled receptors to inhibit of 3′,5′-cyclic adenosine monophosphate (cAMP) production have been effective in preclinical trials and have led to the first approved treatment for ADPKD. However, completely blocking cAMP mediated PKA activation is not feasible and PKA activation independently from cAMP can also occur in ADPKD. Therefore, targeting the cAMP/PKA/CREB pathway beyond cAMP production makes sense. Redundancy of mechanisms, numerous positive and negative feedback loops, and possibly counteracting effects may limit the effectiveness of targeting downstream pathways. Nevertheless, interventions targeting important regulatory, signaling and pathophysiologic pathways downstream from cAMP/PKA activation may provide additive or synergistic value and build on a strategy that has already had success. The purpose of this manuscript is to review the role of cAMP and PKA signaling and their multiple downstream pathways as potential targets for emergent therapies for ADPKD.

Activation of signaling pathways in models of t(6;9)-acute myeloid leukemia

Patients within the WHO-subgroup of t(6;9)-positive acute myeloid leukemia (AML) differ from other AML subgroups as they are characterised by younger age and a grim prognosis. Leukemic transformation can often be attributed to single chromosomal aberrations encoding oncogenes, in the case of t(6;9)-AML to the fusion protein DEK-CAN (also called DEK-NUP214). As being a rare disease there is the urgent need for models of t(6;9)-AML. The only cell line derived from a t(6;9)-AML patient currently available is FKH1. By using phospho-proteomics on FKH1 cells, we found a strongly activated ABL1 kinase. Further investigation revealed the presence of ETV6-ABL1. This finding renders necessary to determine DEK-CAN- and ETV6-ABL1-related features when using FKH1. This can be done as ETV6-ABL1 activity in FKH1 is responsive to imatinib. Nevertheless, we provided evidence that both SFK and mTOR activation in FKH1 are DEK-CAN-related features as they were activated also in other t(6;9) and DEK-CAN-positive models. The activation of STAT5 previously shown to be strong in t(6;9)-AML and activated by DEK-CAN is regulated in FKH1 by both DEK-CAN and ETV6-ABL1. In conclusion, FKH1 cells still represent a model for t(6;9)-AML and could serve as model for ETV6-ABL1-positive AML if the presence of these leukemia-inducing oncogenes is adequately considered.Taken together, all our results provide clear evidence of novel and specific interdependencies between leukemia-inducing oncogenes and cancer signaling pathways which will influence the design of therapeutic strategies to better address the complexity of cancer signaling.

The story of EGFR: from signaling pathways to a potent anticancer target

EGFR is a member of the ERBB family. It plays a significant role in cellular processes such as growth, survival and differentiation via the activation of various signaling pathways. EGFR deregulation is implicated in various human malignancies, and therefore EGFR has emerged as an attractive anticancer target. EGFR inhibition using strategies such as tyrosine kinase inhibitors and monoclonal antibodies hinders cellular proliferation and promotes apoptosis in cancer cells in vitro and in vivo. EGFR inhibition by tyrosine kinase inhibitors has been shown to be a better treatment option than chemotherapy for advanced-stage EGFR-driven non-small-cell lung cancer, yet de novo and acquired resistance limits the clinical benefit of these therapeutic molecules. This review discusses the cellular signaling pathways activated by EGFR. Further, current therapeutic strategies to target aberrant EGFR signaling in cancer and mechanisms of resistance to them are highlighted.

STAT3 regulates inflammatory cytokine production downstream of TNFR1 by inducing expression of TNFAIP3/A20

Tumour Necrosis Factor (TNF) potently induces a transient inflammatory response that must be downregulated once any invasive stimulus has resolved. Yet, how TNF‐induced inflammation is shut down in normal cells is incompletely understood. The present study shows that STAT3 was activated in mouse embryo fibroblasts (MEFs) by treatment with TNF or an agonist antibody to TNFR1. STAT3 activation was inhibited by pharmacological inhibition of the Jak2 tyrosine kinase that associates with TNFR1. To identify STAT3 target genes, global transcriptome analysis by RNA sequencing was performed in wild‐type MEFs and MEFs from STAT3 knockout (STAT3^KO) mice that were stimulated with TNF, and the results were validated at the protein level by using multiplex cytokine assays and immunoblotting. After TNF stimulation, STAT3^KO MEFs showed greater gene and protein induction of the inflammatory chemokines Ccl2, Cxcl1 and Cxcl10 than WT MEFs. These observations show that, by activating STAT3, TNF selectively modulates expression of a cohort of chemokines that promote inflammation. The greater induction by TNF of chemokines in STAT3^KO than WT MEFs suggested that TNF induced an inhibitory protein in WT MEFs. Consistent with this possibility, STAT3 activation by TNFR1 increased the expression of Tnfaip3/A20, a ubiquitin modifying enzyme that inhibits inflammation, in WT MEFs but not in STAT3^KO MEFs. Moreover, enforced expression of Tnfaip3/A20 in STAT3^KO MEFs suppressed proinflammatory chemokine expression induced by TNF. Our observations identify Tnfaip3/A20 as a new downstream target for STAT3 which limits the induction of Ccl2, Cxcl1 and Cxcl10 and inflammation induced by TNF.

Loss of Polycystin-1 causes cAMP-dependent switch from tubule to cyst formation

Autosomal dominant polycystic kidney disease is the most common monogenic disease that causes end-stage renal failure. It primarily results from mutations in the PKD1 gene that encodes for Polycystin-1. How loss of Polycystin-1 translates into bilateral renal cyst development is mostly unknown. cAMP is significantly involved in cyst enlargement but its role in cyst initiation has remained elusive. Deletion of Polycystin-1 in collecting duct cells resulted in a switch from tubule to cyst formation and was accompanied by an increase in cAMP. Pharmacological elevation of cAMP in Polycystin-1-competent cells caused cyst formation, impaired plasticity, nondirectional migration, and mis-orientation, and thus strongly resembled the phenotype of Polycystin-1-deficient cells. Mis-orientation of developing tubule cells in metanephric kidneys upon loss of Polycystin-1 was phenocopied by pharmacological increase of cAMP in wildtype kidneys. In vitro, cAMP impaired tubule formation after capillary-induced injury which was further impaired by loss Polycystin-1.

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Loss of Polycystin-1 switches renal cells from tubule to cyst formation

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Deletion of Polycystin-1 leads to increase in cAMP

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Elevation of cAMP in wildtype cells phenocopies Polycystin-1-deficient features

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Features are: impaired plasticity, nondirectional migration, and mis-orientation

The roles of epidermal growth factor receptor in viral infections

Viruses are intracellular pathogen that exploit host cellular machinery for their propagation. Extensive research on virus-host interaction have shed light on an alternative antiviral strategy that targets host cell factors. Epidermal growth factor receptor (EGFR) is a versatile signal transducer that is involved in a range of cellular processes. Numerous studies have revealed how viruses exploit the function of EGFR in different stages of viral life cycle. In general, viruses attach onto the host cell surface and interacts with EGFR to facilitate viral entry, viral replication and spread as well as evasion from host immunosurveillance. Moreover, virus-induced activation of EGFR signalling is associated with mucin expression, tissue damage and carcinogenesis that contribute to serious complications. Herein, we review our current understanding of roles of EGFR in viral infection and its potential as therapeutic target in managing viral infection. We also discuss the available EGFR-targeted therapies and their limitations.

Stat3 Signaling Pathway: A Future Therapeutic Target for Bone-Related Diseases

Signal transducer and activator of transcription 3 (Stat3) is activated by phosphorylation and translocated to the nucleus to participate in the transcriptional regulation of DNA. Increasing evidences point that aberrant activation or deletion of the Stat3 plays a critical role in a broad range of pathological processes including immune escape, tumorigenesis, and inflammation. In the bone microenvironment, Stat3 acts as a common downstream response protein for multiple cytokines and is engaged in the modulation of cellular proliferation and intercellular interactions. Stat3 has direct impacts on disease progression by regulating mesenchymal stem cells differentiation, osteoclast activation, macrophage polarization, angiogenesis, and cartilage degradation. Here, we describe the theoretical basis and key roles of Stat3 in different bone-related diseases in combination with in vitro experiments and animal models. Then, we summarize and categorize the drugs that target Stat3, providing potential therapeutic strategies for their use in bone-related diseases. In conclusion, Stat3 could be a future target for bone-related diseases.

HIPK2 directs cell type-specific regulation of STAT3 transcriptional activity in Th17 cell differentiation

SignificanceSTAT3 (signal transducer and activator of transcription 3) is a master transcription factor that organizes cellular responses to cytokines and growth factors and is implicated in inflammatory disorders. STAT3 is a well-recognized therapeutic target for human cancer and inflammatory disorders, but how its function is regulated in a cell type-specific manner has been a major outstanding question. We discovered that Stat3 imposes self-directed regulation through controlling transcription of its own regulator homeodomain-interacting protein kinase 2 (Hipk2) in a T helper 17 (Th17) cell-specific manner. Our validation of the functional importance of the Stat3-Hipk2 axis in Th17 cell development in the pathogenesis of T cell-induced colitis in mice suggests an approach to therapeutically treat inflammatory bowel diseases that currently lack a safe and effective therapy.

STAT3 pathway in cancers: Past, present, and future

Signal transducer and activator of transcription 3 (STAT3), a member of the STAT family, discovered in the cytoplasm of almost all types of mammalian cells, plays a significant role in biological functions. The duration of STAT3 activation in normal tissues is a transient event and is strictly regulated. However, in cancer tissues, STAT3 is activated in an aberrant manner and is induced by certain cytokines. The continuous activation of STAT3 regulates the expression of downstream proteins associated with the formation, progression, and metastasis of cancers. Thus, elucidating the mechanisms of STAT3 regulation and designing inhibitors targeting the STAT3 pathway are considered promising strategies for cancer treatment. This review aims to introduce the history, research advances, and prospects concerning the STAT3 pathway in cancer. We review the mechanisms of STAT3 pathway regulation and the consequent cancer hallmarks associated with tumor biology that are induced by the STAT3 pathway. Moreover, we summarize the emerging development of inhibitors that target the STAT3 pathway and novel drug delivery systems for delivering these inhibitors. The barriers against targeting the STAT3 pathway, the focus of future research on promising targets in the STAT3 pathway, and our perspective on the overall utility of STAT3 pathway inhibitors in cancer treatment are also discussed.

Dihydrotanshinone I inhibits the growth of hepatoma cells by direct inhibition of Src

BACKGROUND

Liver cancer is one of the leading causes of cancer-related death worldwide. Dihydrotanshinone I (DHI) was shown to inhibit the growth of several types of cancer. However, research related to hepatoma treatment using DHI is limited.

PURPOSE

Here, we explored the inhibitory effect of DHI on the growth of hepatoma cells, and investigated the underlying molecular mechanisms.

METHODS

The proliferation of Hep3B, SMCC-7721 and SK-Hep1 hepatoma cells was evaluated using the MTS and Edu staining assay. Hepatoma cell death was analyzed with a LIVE/DEAD Cell Imaging Kit. The relative expression and phosphorylation of proto-oncogene tyrosine-protein kinase Src (Src) and signal transducer and activator of transcription-3 (STAT3) proteins in hepatoma cells, as well as the expression of other protein components, were measured by western blotting. The structural interaction of DHI with Src proteins was evaluated by molecular docking, molecular dynamics simulation, surface plasmon resonance imaging and Src kinase inhibition assay. Src overexpression was achieved by infection with an adenovirus vector encoding human Src. Subsequently, the effects of DHI on tumor growth inhibition were further validated using mouse xenograft models of hepatoma.

RESULTS

In vitro studies showed that treatment with DHI inhibited the proliferation and promoted cell death of Hep3B, SMCC-7721 and SK-Hep1 hepatoma cells. We further identified and verified Src as a direct target of DHI by using molecular stimulation, surface plasmon resonance image and Src kinase inhibition assay. Treatment with DHI reduced the in vitro phosphorylation levels of Src and STAT3, a transcription factor regulated by Src. In the xenograft mouse models, DHI dose-dependently suppressed tumor growth and Src and STAT3 phosphorylation. Moreover, Src overexpression partly abrogated the inhibitory effects of DHI on the proliferation and cell death in hepatoma cells.

CONCLUSION

Our results suggest that DHI inhibits the growth of hepatoma cells by direct inhibition of Src.

SRC kinase-mediated signaling pathways and targeted therapies in breast cancer

Breast cancer (BC) has been ranked the most common malignant tumor throughout the world and is also a leading cause of cancer-related deaths among women. SRC family kinases (SFKs) belong to the non-receptor tyrosine kinase (nRTK) family, which has eleven members sharing similar structure and function. Among them, SRC is the first identified proto-oncogene in mammalian cells. Oncogenic overexpression or activation of SRC has been revealed to play essential roles in multiple events of BC progression, including tumor initiation, growth, metastasis, drug resistance and stemness regulations. In this review, we will first give an overview of SRC kinase and SRC-relevant functions in various subtypes of BC and then systematically summarize SRC-mediated signaling transductions, with particular emphasis on SRC-mediated substrate phosphorylation in BC. Furthermore, we will discuss the progress of SRC-based targeted therapies in BC and the potential future direction.

Fusion Genes Altered in Adult Malignant Gliomas

Malignant gliomas are highly heterogeneous brain tumors in molecular genetic background. Despite the many recent advances in the understanding of this disease, patients with adult high-grade gliomas retain a notoriously poor prognosis. Fusions involving oncogenes have been reported in gliomas and may serve as novel therapeutic targets to date. Understanding the gene fusions and how they regulate oncogenesis and malignant progression will contribute to explore new approaches for personalized treatment. By now, studies on gene fusions in gliomas remain limited. However, some current clinical trials targeting fusion genes have presented exciting preliminary findings. The aim of this review is to summarize all the reported fusion genes in high-grade gliomas so far, discuss the characterization of some of the most popular gene fusions occurring in malignant gliomas, as well as their function in tumorigenesis, and the underlying clinical implication as therapeutic targets.

Effects of Fatty Acid Oxidation and Its Regulation on Dendritic Cell-Mediated Immune Responses in Allergies: An Immunometabolism Perspective

Type 1 allergies, involve a complex interaction between dendritic cells and other immune cells, are pathological type 2 inflammatory immune responses against harmless allergens. Activated dendritic cells undergo extensive phenotypic and functional changes to exert their functions. The activation, differentiation, proliferation, migration, and mounting of effector reactions require metabolic reprogramming. Dendritic cells are important upstream mediators of allergic responses and are therefore an important effector of allergies. Hence, a better understanding of the underlying metabolic mechanisms of functional changes that promote allergic responses of dendritic cells could improve the prevention and treatment of allergies. Metabolic changes related to dendritic cell activation have been extensively studied. This review briefly outlines the basis of fatty acid oxidation and its association with dendritic cell immune responses. The relationship between immune metabolism and effector function of dendritic cells related to allergic diseases can better explain the induction and maintenance of allergic responses. Further investigations are warranted to improve our understanding of disease pathology and enable new treatment strategies.

Inhibition of STAT3 enhances sensitivity to tamoxifen in tamoxifen-resistant breast cancer cells

BACKGROUND

The mechanisms of endocrine resistance are complex, and deregulation of several oncogenic signalling pathways has been proposed. We aimed to investigate the role of the EGFR and Src-mediated STAT3 signalling pathway in tamoxifen-resistant breast cancer cells.

METHODS

The ER-positive luminal breast cancer cell lines, MCF-7 and T47D, were used. We have established an MCF-7-derived tamoxifen-resistant cell line (TamR) by long-term culture of MCF-7 cells with 4-hydroxytamoxifen. Cell viability was determined using an MTT assay, and protein expression levels were determined using western blot. Cell cycle and annexin V staining were analysed using flow cytometry.

RESULTS

TamR cells showed decreased expression of estrogen receptor and increased expression of EGFR. TamR cells showed an acceleration of the G1 to S phase transition. The protein expression levels of phosphorylated Src, EGFR (Y845), and STAT3 was increased in TamR cells, while phosphorylated Akt was decreased. The expression of p-STAT3 was enhanced according to exposure time of tamoxifen in T47D cells, suggesting that activation of STAT3 can cause tamoxifen resistance in ER-positive breast cancer cells. Both dasatinib (Src inhibitor) and stattic (STAT3 inhibitor) inhibited cell proliferation and induced apoptosis in TamR cells. However, stattic showed a much stronger effect than dasatinib. Knockdown of STAT3 expression by siRNA had no effect on sensitivity to tamoxifen in MCF-7 cells, while that enhanced sensitivity to tamoxifen in TamR cells. There was not a significant synergistic effect of dasatinib and stattic on cell survival. TamR cells have low nuclear p21(Cip1) expression compared to MCF-7 cells and inhibition of STAT3 increased the expression of nuclear p21(Cip1) in TamR cells.

CONCLUSIONS

The EGFR and Src-mediated STAT3 signalling pathway is activated in TamR cells, and inhibition of STAT3 may be a potential target in tamoxifen-resistant breast cancer. An increase in nuclear p21(Cip1) may be a key step in STAT3 inhibitor-induced cell death in TamR cells.

Activation of STAT transcription factors by the Rho-family GTPases

The Rho-family of small GTPases are biological molecular switches that are best known for their regulation of the actin cytoskeleton. Through their activation and stimulation of downstream effectors, the Rho-family control pathways involved in cellular morphology, which are commonly activated in cancer cell invasion and metastasis. While this makes them excellent potential therapeutic targets, a deeper understanding of the downstream signalling pathways they influence will be required for successful drug targeting. Signal transducers and activators of transcription (STATs) are a family of transcription factors that are hyper-activated in most cancer types and while STATs are widely understood to be activated by the JAK family of kinases, many additional activators have been discovered. A growing number of examples of Rho-family driven STAT activation, largely of the oncogenic family members, STAT3 and STAT5, are being identified. Cdc42, Rac1, RhoA, RhoC and RhoH have all been implicated in STAT activation, contributing to Rho GTPase-driven changes in cellular morphology that lead to cell proliferation, invasion and metastasis. This highlights the importance and therapeutic potential of the Rho-family as regulators of non-canonical activation of STAT signalling.

The Many Faces of JAKs and STATs Within the COVID-19 Storm

The positive-sense single stranded RNA virus, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), resulted in a global pandemic with horrendous health and economic consequences not seen in a century. At a finer scale, immunologically, many of these devastating effects by SARS-CoV-2 can be traced to a "cytokine storm" resulting in the simultaneous activation of Janus Kinases (JAKs) and Signal Transducers and Activators of Transcription (STAT) proteins downstream of the many cytokine receptor families triggered by elevated cytokines found in Coronavirus Disease 2019 (COVID-19). In this report, cytokines found in the storm are discussed in relation to the JAK-STAT pathway in response to SARS-CoV-2 and the lessons learned from RNA viruses and previous Coronaviruses (CoVs). Therapeutic strategies to counteract the SARS-CoV-2 mediated storm are discussed with an emphasis on cell signaling and JAK inhibition.

Src-Yap1 signaling axis controls the trophectoderm and epiblast lineage differentiation in mouse embryonic stem cells

The tyrosine kinase Src is highly expressed in embryonic stem cells (ESCs) and ESC-differentiated cells, however, its functional role remains obscured. Here, we constitutivelyexpressed Src in mouse ESCs and found these cells retained comparable levels of the core pluripotent factors, such as Oct4 and Sox2, while promoted the expression of epiblast lineage markers and restrained trophoblast lineage markers compared to the control ESCs. Knockdown of Src in mouse ESCs showed the opposite effect. Directly differentiation of these ESCs to epiblast and trophoblast lineage cells revealed that Src activation dramatically accelerated the production of epiblast-like cells and inhibited the induction of trophoblast-like cells in vitro. Mechanistically, we found Src activation enhanced the Yap1-Tead interaction and their transcriptional output in mouse ESCs through specially upregulating Yap1 tyrosine phosphorylation. Subsequently, we found that overexpression of Yap1 in mouse ESCs phenocopied the differentiation patterns of Src overexpressing cells in vitro. Moreover, inhibition of Src kinase activity by Dasatinib or Yap1/Tead-mediated transcription with Verteporfin reversed the differentiation patterns of Src overexpressing ESCs. Taken together, our results unravel a novel Src-Yap1 regulatory axis during mouse ESC differentiation to trophectoderm and epiblast lineage cells in vitro.

LRG1 Promotes Metastatic Dissemination of Melanoma through Regulating EGFR/STAT3 Signalling

Although less common, melanoma is the deadliest form of skin cancer largely due to its highly metastatic nature. Currently, there are limited treatment options for metastatic melanoma and many of them could cause serious side effects. A better understanding of the molecular mechanisms underlying the complex disease pathophysiology of metastatic melanoma may lead to the identification of novel therapeutic targets and facilitate the development of targeted therapeutics. In this study, we investigated the role of leucine-rich α-2-glycoprotein 1 (LRG1) in melanoma development and progression. We first established the association between LRG1 and melanoma in both human patient biopsies and mouse melanoma cell lines and revealed a significant induction of LRG1 expression in metastatic melanoma cells. We then showed no change in tumour cell growth, proliferation, and angiogenesis in the absence of the host Lrg1. On the other hand, there was reduced melanoma cell metastasis to the lungs in Lrg1-deficient mice. This observation was supported by the promoting effect of LRG1 in melanoma cell migration, invasion, and adhesion. Mechanistically, LRG1 mediates melanoma cell invasiveness in an EGFR/STAT3-dependent manner. Taken together, our studies provided compelling evidence that LRG1 is required for melanoma metastasis but not growth. Targeting LRG1 may offer an alternative strategy to control malignant melanoma.

Emerin Represses STAT3 Signaling through Nuclear Membrane-Based Spatial Control

Emerin is the inner nuclear membrane protein involved in maintaining the mechanical integrity of the nuclear membrane. Mutations in EMD encoding emerin cause Emery–Dreifuss muscular dystrophy (EDMD). Evidence is accumulating that emerin regulation of specific gene expression is associated with this disease, but the exact function of emerin has not been fully elucidated. Here, we show that emerin downregulates Signal transducer and activators of transcription 3 (STAT3) signaling, activated exclusively by Janus kinase (JAK). Deletion mutation experiments show that the lamin-binding domain of emerin is essential for the inhibition of STAT3 signaling. Emerin interacts directly and co-localizes with STAT3 in the nuclear membrane. Emerin knockdown induces STAT3 target genes Bcl2 and Survivin to increase cell survival signals and suppress hydrogen peroxide-induced cell death in HeLa cells. Specifically, downregulation of BAF or lamin A/C increases STAT3 signaling, suggesting that correct-localized emerin, by assembling with BAF and lamin A/C, acts as an intrinsic inhibitor against STAT3 signaling. In C2C12 cells, emerin knockdown induces STAT3 target gene, Pax7, and activated abnormal myoblast proliferation associated with muscle wasting in skeletal muscle homeostasis. Our results indicate that emerin downregulates STAT3 signaling by inducing retention of STAT3 and delaying STAT3 signaling in the nuclear membrane. This mechanism provides clues to the etiology of emerin-related muscular dystrophy and may be a new therapeutic target for treatment.

Germline STAT3 gain-of-function mutations in primary immunodeficiency: Impact on the cellular and clinical phenotype

Signal transducer and activator of transcription 3 (STAT3) is a key transcription factor involved in regulation of immune cell activation and differentiation. Recent discoveries highlight the role of germline activating STAT3 mutations in inborn errors of immunity characterized by early-onset multi-organ autoimmunity and lymphoproliferation. Much progress has been made in defining the clinical spectrum of STAT3 GOF disease and unraveling the molecular and cellular mechanisms underlying this disease. In this review, we summarize our current understanding of the disease and discuss the clinical phenotype, diagnostic approach, cellular and molecular effects of STAT3 GOF mutations and therapeutic concepts for these patients.

Targeting STAT3 with Proteolysis Targeting Chimeras and Next-Generation Antisense Oligonucleotides

STAT3 has been recognized for its key role in the progression of cancer, where it is frequently upregulated or constitutively hyperactivated, contributing to tumor cell proliferation, survival, and migration, as well as angiogenesis and suppression of antitumor immunity. Given the ubiquity of dysregulated STAT3 activity in cancer, it has long been considered a highly attractive target for the development of anticancer therapies. Efforts to target STAT3, however, have proven to be especially challenging, perhaps owing to the fact that transcription factors lack targetable enzymatic activity and have historically been considered "undruggable." Small-molecule inhibitors targeting STAT3 have been limited by insufficient selectivity and potency. More recently, therapeutic approaches that selectively target STAT3 protein for degradation have been developed, offering novel strategies that do not rely on inhibition of upstream pathways or direct competitive inhibition of the STAT3 protein. Here, we review these emerging approaches, including the development of STAT3 proteolysis targeting chimera agents, as well as preclinical and clinical studies of chemically stabilized antisense molecules, such as the clinical agent AZD9150. These therapeutic strategies may robustly reduce the cellular activity of oncogenic STAT3 and overcome the historical limitations of less selective small molecules.

A Rab escort protein regulates the MAPK pathway that controls filamentous growth in yeast

MAPK pathways regulate different responses yet can share common components. Although core regulators of MAPK pathways are well known, new pathway regulators continue to be identified. Overexpression screens can uncover new roles for genes in biological processes and are well suited to identify essential genes that cannot be evaluated by gene deletion analysis. In this study, a genome-wide screen was performed to identify genes that, when overexpressed, induce a reporter (FUS1-HIS3) that responds to ERK-type pathways (Mating and filamentous growth or fMAPK) but not p38-type pathways (HOG) in yeast. Approximately 4500 plasmids overexpressing individual yeast genes were introduced into strains containing the reporter by high-throughput transformation. Candidate genes were identified by measuring growth as a readout of reporter activity. Fourteen genes were identified and validated by re-testing: two were metabolic controls (HIS3, ATR1), five had established roles in regulating ERK-type pathways (STE4, STE7, BMH1, BMH2, MIG2) and seven represent potentially new regulators of MAPK signaling (RRN6, CIN5, MRS6, KAR2, TFA1, RSC3, RGT2). MRS6 encodes a Rab escort protein and effector of the TOR pathway that plays a role in nutrient signaling. MRS6 overexpression stimulated invasive growth and phosphorylation of the ERK-type fMAPK, Kss1. Overexpression of MRS6 reduced the osmotolerance of cells and phosphorylation of the p38/HOG MAPK, Hog1. Mrs6 interacted with the PAK kinase Ste20 and MAPKK Ste7 by two-hybrid analysis. Based on these results, Mrs6 may selectively propagate an ERK-dependent signal. Identifying new regulators of MAPK pathways may provide new insights into signal integration among core cellular processes and the execution of pathway-specific responses.

STAT4 targets KISS1 to promote the apoptosis of ovarian granulosa cells

Background

In mammals, it is known that the estradiol-17β (E2) is mainly synthetized in ovarian granulosa cells (GCs), and the excessive apoptosis of GCs induces the follicular atresia. Many studies have implicated the essential role of KISS1, with the pro-synthetic effect of E2 and the anti-apoptotic effect on GCs, in the mammalian folliculogenesis, and several STAT4 potential binding sites were previously predicted on the promoter of KISS1 in pigs. However, the biological effects of STAT4 on GCs and the molecular regulation between STAT4 and KISS1 remained largely unknown.

Methods

Using the porcine GCs as the cellular model, the overexpression plasmid, small interfering RNA, 5′-deletion and luciferase assay were applied to investigate the molecular mechanisms for STAT4 regulating the expression of KISS1.

Results

In this study, the STAT4 negatively regulated the mRNA and protein levels of KISS1 in porcine GCs, and the mRNA level of STAT4 was observed to significantly decrease from immature to mature follicles, which was inversed with that of KISS1. The relative luciferase activity of KISS1 promoter was significantly increased with deletion of the fourth potential binding site (− 305/− 295), and ChIP further confirmed that the STAT4 bound at − 305/− 295 region of KISS1. Besides, the STAT4 significantly regulated the mRNA levels of PDK1, FOXO3 and TSC2 of PI3K signaling pathway to promote the cell apoptosis and the percentage of cells at G0/G1 phase of cell cycle in GCs. Alternatively, the STAT4 significantly decreased the mRNA levels of CYP17, 3B-HSD, 17B-33 HSD, ESR1, and ESR2, as well as the concentration of E2 in GCs. Furthermore, interfering with the expression of STAT4 was observed to significantly stimulate the pro-synthetic effect of E2 and anti-apoptotic effect of KISS1 in GCs.

Conclusions

Collectively, the STAT4 might directly target at − 305/− 295 region of KISS1 to negatively regulate the transcription of KISS1, promote the cell apoptosis via PI3K signaling pathway, suppress the synthesis of E2 through the estrogen signaling pathway in porcine GCs. These proposed works could provide useful insight in further investigations on the molecular functionalities of STAT4 and KISS1 in the folliculogenesis of mammals.

Polycyclic polyprenylated acylphloroglucinols from Garcinia xanthochymus fruits exhibit antitumor effects through inhibition of the STAT3 signaling pathway

The fruits of Garcinia xanthochymus can be eaten raw or processed into jams, preserves and vinegar. They provide not only vitamin and protein nutrients, but also pharmacologically active compounds, among which polycyclic polyprenylated acylphloroglucinols (PPAPs) are a major class. According to the literature, PPAPs exhibited good anti-cancer effects. This study investigated the antitumor effects and the underlying mechanism of S1 (the regioisomeric mixture of xanthochymol and guttiferone E) and S2 (the regioisomeric mixture of isoxanthochymol and cycloxanthochymol) isolated from the fruits of G. xanthochymus. In an H22 allograft mouse model, S1 and S2 could suppress the liver tumor growth and phosphorylation of STAT3. Computational modeling showed that S1 and S2 could form hydrogen bonds with the SH2 domain of STAT3. In HepG2 and MCF-7 cell lines, S1 and S2 downregulated the expression of p-STAT3^Tyr705. Moreover, S1 and S2 inhibited the phosphorylation of JAK2 and Src, which are the upstream kinases of STAT3, and the expression of various STAT3-regulated genes, including anti-apoptotic (Bcl-XL, Mcl-1 and survivin), proliferative (cyclin D1) and angiogenic (VEGF) genes. As a result, S1 and S2 arrested the cell cycle and induced cell apoptosis, which were proved by the activation of cleaved caspase-3 and caspase-8. These results demonstrated that S1 and S2 from G. xanthochymus exhibited antitumor effects through the inactivation of STAT3, and could be promising candidates for cancer treatment.

STAT3 and AKT signaling pathways mediate oncogenic role of NRSF in hepatocellular carcinoma

Neuron-restrictive silencer factor (NRSF) is a zinc finger protein that acts as a negative transcriptional regulator by recruiting histone deacetylases and other co-factors. It plays a crucial role in nervous system development and is recently reported to be involved in tumorigenesis in a tumor type-dependent manner; however, the role of NRSF in hepatocellular carcinoma (HCC) tumorigenesis remains unclear. Here, we found that NRSF expression was up-regulated in 27 of 49 human HCC tissue samples examined. Additionally, mice with conditional NRSF-knockout in the liver exhibited a higher tolerance against diethylnitrosamine (DEN)-induced acute liver injury and were less sensitive to DEN-induced HCC initiation. Our results showed that silencing NRSF in HepG2 cells using RNAi technology significantly inhibited HepG2 cell proliferation and severely hindered their migration and invasion potentials. Our results demonstrated that NRSF plays a pivotal role in promoting DEN-induced HCC initiation via a mechanism related to the STAT3 and AKT signaling pathways. Thus, NRSF could be a potential therapeutic target for treating human HCC.

Beneficial effect of STAT3 decoy oligodeoxynucleotide transfection on organ injury and mortality in mice with cecal ligation and puncture-induced sepsis

Sepsis is a major clinical challenge with unacceptably high mortality. The signal transducers and activators of transcription (STAT) family of transcription factors is known to activate critical mediators of cytokine responses, and, among this family, STAT3 is implicated to be a key transcription factor in both immunity and inflammatory pathways. We investigated whether in vivo introduction of synthetic double-stranded STAT3 decoy oligodeoxynucleotides (ODNs) can provide benefits for reducing organ injury and mortality in mice with cecal ligation and puncture (CLP)-induced polymicrobial sepsis. We found that STAT3 was rapidly activated in major end-organ tissues following CLP, which was accompanied by activation of the upstream kinase JAK2. Transfection of STAT3 decoy ODNs downregulated pro-inflammatory cytokine/chemokine overproduction in CLP mice. Moreover, STAT3 decoy ODN transfection significantly reduced the increases in tissue mRNAs and proteins of high mobility group box 1 (HMGB1) and strongly suppressed the excessive elevation in serum HMGB1 levels in CLP mice. Finally, STAT3 decoy ODN administration minimized the development of sepsis-driven major end-organ injury and led to a significant survival advantage in mice after CLP. Our results suggest a critical role of STAT3 in the sepsis pathophysiology and the potential usefulness of STAT3 decoy ODNs for sepsis gene therapy.

STAT3 transcription factor as target for anti-cancer therapy

STATs constitute a large family of transcription activators and transducers of signals that have an important role in many cell functions as regulation of proliferation and differentiation of the cell also regulation of apoptosis and angiogenesis. STAT3 as a member of that family, recently was discovered to have a vital role in progression of different types of cancers. The activation of STAT3 was observed to regulate multiple gene functions during cancer-like cell proliferation, differentiation, apoptosis, metastasis, inflammation, immunity, cell survival, and angiogenesis. The inhibition of STAT3 activation has been an important target for cancer therapy. Inhibitors of STAT3 have been used for a long time for treatment of many types of cancers like leukemia, melanoma, colon, and renal cancer. In this review article, we summarize and discuss different drugs inhibiting the action of STAT3 and used in treatment of different types of cancer.

Regulation of cell activation by A20 through STAT signaling in acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the hematologic malignancy characterized by the aberrant proliferation of immature lymphoid cells. A20 is a deubiquitinase gene that inhibits functional activation of immune cells mediated through NF-κB/STAT pathways and frequently found inactivated in lymphoma. IL-6 is a pro-inflammatory cytokine secreted by immune cells under the pathogenic conditions and regulated by STAT signaling. Little is known about the role of A20 in regulating the function of ALL blasts and underlying molecular mechanisms. The present study, therefore, explored whether A20 expression contributes to IL-6 induced cell migration and activation of myeloid cells in ALL. To this end, blood samples of thirty-five adult ALL patients were examined. Gene expression profile was determined by quantitative RT-PCR, immunophenotype by flow cytometry, secretion of inflammatory cytokines by ELISA, and cell migration by a transwell migration assay. As a result, the expression of A20 was inactivated in ALL. Immunophenotypic analysis indicated that percent of CD11b⁺CD40⁺ expressing cells present in ALL was significantly reduced when transfected with PEM-T easy A20. Importantly, IL6-induced CXCL12-mediated migration of ALL blasts was dependent on the presence of A20. The inhibitory effects of A20 on activated myeloid cells and migration of ALL blasts were mediated through the STAT pathway upon IL-6 challenge. In addition, the CA-125 level was much higher in elderly females than either young female or male ALL patients or healthy donors. In conclusion, the inhibitory effects of A20 on activation of ALL blasts are expected to affect the immune response to treatment for adult ALL patients.

STAT signaling in polycystic kidney disease

The most common form of polycystic kidney disease (PKD) in humans is caused by mutations in the PKD1 gene coding for polycystin1 (PC1). Among the many identified or proposed functions of PC1 is its ability to regulate the activity of transcription factors of the STAT family. Most STAT proteins that have been investigated were found to be aberrantly activated in kidneys in PKD, and some have been shown to be drivers of disease progression. In this review, we focus on the role of signal transducer and activator of transcription (STAT) signaling pathways in various renal cell types in healthy kidneys as compared to polycystic kidneys, on the mechanisms of STAT regulation by PC1 and other factors, and on the possibility to target STAT signaling for PKD therapy.

SRC-Family Kinases in Acute Myeloid Leukaemia and Mastocytosis

Protein tyrosine kinases have been recognized as important actors of cell transformation and cancer progression, since their discovery as products of viral oncogenes. SRC-family kinases (SFKs) play crucial roles in normal hematopoiesis. Not surprisingly, they are hyperactivated and are essential for membrane receptor downstream signaling in hematological malignancies such as acute myeloid leukemia (AML) and mastocytosis. The precise roles of SFKs are difficult to delineate due to the number of substrates, the functional redundancy among members, and the use of tools that are not selective. Yet, a large num ber of studies have accumulated evidence to support that SFKs are rational therapeutic targets in AML and mastocytosis. These two pathologies are regulated by two related receptor tyrosine kinases, which are well known in the field of hematology: FLT3 and KIT. FLT3 is one of the most frequently mutated genes in AML, while KIT oncogenic mutations occur in 80-90% of mastocytosis. Studies on oncogenic FLT3 and KIT signaling have shed light on specific roles for members of the SFK family. This review highlights the central roles of SFKs in AML and mastocytosis, and their interconnection with FLT3 and KIT oncoproteins.

KIT and Melanoma: Biological Insights and Clinical Implications

Melanoma, originating from epidermal melanocytes, is a heterogeneous disease that has the highest mortality rate among all types of skin cancers. Numerous studies have revealed the cause of this cancer as related to various somatic driver mutations, including alterations in KIT-a proto-oncogene encoding for a transmembrane receptor tyrosine kinase. Although accounting for only 3% of all melanomas, mutations in c-KIT are mostly derived from acral, mucosal, and chronically sun-damaged melanomas. As an important factor for cell differentiation, proliferation, and survival, inhibition of c-KIT has been exploited for clinical trials in advanced melanoma. Here, apart from the molecular background of c-KIT and its cellular functions, we will review the wide distribution of alterations in KIT with a catalogue of more than 40 mutations reported in various articles and case studies. Additionally, we will summarize the association of KIT mutations with clinicopathologic features (age, sex, melanoma subtypes, anatomic location, etc.), and the differences of mutation rate among subgroups. Finally, several therapeutic trials of c-KIT inhibitors, including imatinib, dasatinib, nilotinib, and sunitinib, will be analyzed for their success rates and limitations in advanced melanoma treatment. These not only emphasize c-KIT as an attractive target for personalized melanoma therapy but also propose the requirement for additional investigational studies to develop novel therapeutic trials co-targeting c-KIT and other cytokines such as members of signaling pathways and immune systems.

The "Janus" Role of C/EBPs Family Members in Cancer Progression

CCAAT/enhancer-binding proteins (C/EBPs) constitute a family of transcription factors composed of six members that are critical for normal cellular differentiation in a variety of tissues. They promote the expression of genes through interaction with their promoters. Moreover, they have a key role in regulating cellular proliferation through interaction with cell cycle proteins. C/EBPs are considered to be tumor suppressor factors due to their ability to arrest cell growth (contributing to the terminal differentiation of several cell types) and for their role in cellular response to DNA damage, nutrient deprivation, hypoxia, and genotoxic agents. However, C/EBPs can elicit completely opposite effects on cell proliferation and cancer development and they have been described as both tumor promoters and tumor suppressors. This "Janus" role of C/EBPs depends on different factors, such as the type of tumor, the isoform/s expressed in cells, the type of dimerization (homo- or heterodimerization), the presence of inhibitory elements, and the ability to inhibit the expression of other tumor suppressors. In this review, we discuss the implication of the C/EBPs family in cancer, focusing on the molecular aspects that make these transcription factors tumor promoters or tumor suppressors.

Rhus verniciflua Stokes extract suppresses migration and invasion in human gastric adenocarcinoma AGS cells

BACKGROUND/OBJECTIVES

Many studies have suggested that Rhus verniciflua Stokes (RVS) and its extract are anticancer agents. However, RVS had limited use because it contains urushiol, an allergenic toxin. By improving an existing allergen-removal extraction method, we developed a new allergen-free Rhus verniciflua Stokes extract (RVSE) with higher flavonoid content. In this study, we examined whether RVSE inhibits the ability of AGS gastric cancer cells to migrate and invade.

MATERIALS/METHODS

The flavonoids content of RVSE was analyzed by HPLC. The effects of RVSE on migration and invasion in AGS cells were analyzed by each assay kit. Matrix metalloproteinase (MMP)-9, plasminogen activator inhibitor-1 (PAI-1) and urokinase-type plasminogen activator (uPA) protein expression was analyzed by protein antibody array. The Phosphorylation of signal transducer and activator of transcription (STAT) 3 were assayed by Western blot analysis.

RESULTS

RVSE treatment with 0-100 μg/mL dose-dependently reduced the ability of AGS cells to migrate and invade. Notably, treatment with RVSE strongly inhibited the expression of MMP-9 and uPA and the phosphorylation of STAT3. In contrast, RVSE treatment dramatically increased the expression of PAI-1. These results indicate that the inhibition of MMP-9 and uPA expression and STAT3 phosphorylation and the stimulation of PAI-1 expression contributed to the decreased migration and invasion of AGS cells treated with RVSE.

CONCLUSIONS

These results suggest that RVSE may be used as a natural herbal agent to reduce gastric cancer metastasis.

Genotypic and Phenotypic Characteristics of Acute Promyelocytic Leukemia Translocation Variants

Acute promyelocytic leukemia (APL) is a special disease entity of acute myeloid leukemia (AML). The clinical use of all-trans retinoic acid (ATRA) has transformed APL into the most curable form of AML. The majority of APL cases are characterized by the fusion gene PML-RARA. Although the PML-RARA fusion gene can be detected in almost all APL cases, translocation variants of APL have been reported. To date, this is the most comprehensive review of these translocations, discussing 15 different variants. Reviewed genes involved in APL variants include: ZBTB16, NPM, NuMA, STAT5b, PRKAR1A, FIP1L1, BCOR, NABP1, TBLR1, GTF2I, IRF2BP2, FNDC3B, ADAMDTS17, STAT3, and TFG. The genotypic and phenotypic features of APL translocations are summarized. All reported studies were either case reports or case series indicating the rarity of these entities and limiting the ability to drive conclusions regarding their characteristics. However, reported variants have shown variable clinical and morphological features, with diverse responsiveness to ATRA.

Calcitonin gene-related peptide inhibits angiotensin II-induced NADPH oxidase-dependent ROS via the Src/STAT3 signalling pathway

We had previously demonstrated that the calcitonin gene‐related peptide (CGRP) suppresses the oxidative stress and vascular smooth muscle cell (VSMC) proliferation induced by vascular injury. A recent study also indicated that CGRP protects against the onset and development of angiotensin II (Ang II)‐induced hypertension, vascular hypertrophy and oxidative stress. However, the mechanism behind the effects of CGRP on Ang II‐induced oxidative stress is unclear. CGRP significantly suppressed the level of reactive oxygen species (ROS) generated by NADPH oxidase in Ang II‐induced VSMCs. The Ang II‐stimulated activation of both Src and the downstream transcription factor, STAT3, was abrogated by CGRP. However, the antioxidative effect of CGRP was lost following the expression of constitutively activated Src or STAT3. Pre‐treatment with H‐89 or CGRP_8–37 also blocked the CGRP inhibitory effects against Ang II‐induced oxidative stress. Additionally, both in vitro and in vivo analyses show that CGRP treatment inhibited Ang II‐induced VSMC proliferation and hypertrophy, accompanied by a reduction in ROS generation. Collectively, these results demonstrate that CGRP exhibits its antioxidative effect by blocking the Src/STAT3 signalling pathway that is associated with Ang II‐induced VSMC hypertrophy and hyperplasia.

Molecular Mechanism of Pancreatic Stellate Cells Activation in Chronic Pancreatitis and Pancreatic Cancer

Activated pancreatic stellate cells (PSCs) are the main effector cells in the process of fibrosis, a major pathological feature in pancreatic diseases that including chronic pancreatitis and pancreatic cancer. During tumorigenesis, quiescent PSCs change into an active myofibroblast-like phenotype which could create a favorable tumor microenvironment and facilitate cancer progression by increasing proliferation, invasiveness and inducing treatment resistance of pancreatic cancer cells. Many cellular signals are revealed contributing to the activation of PSCs, such as transforming growth factor-β, platelet derived growth factor, mitogen-activated protein kinase (MAPK), Smads, nuclear factor-κB (NF-κB) pathways and so on. Therefore, investigating the role of these factors and signaling pathways in PSCs activation will promote the development of PSCs-specific therapeutic strategies that may provide novel options for pancreatic cancer therapy. In this review, we systematically summarize the current knowledge about PSCs activation-associated stimulating factors and signaling pathways and hope to provide new strategies for the treatment of pancreatic diseases.

Inhibition of Tyrosine-Phosphorylated STAT3 in Human Breast and Lung Cancer Cells by Manuka Honey is Mediated by Selective Antagonism of the IL-6 Receptor

Aberrantly high levels of tyrosine-phosphorylated signal transducer and activator of transcription 3 (p-STAT3) are found constitutively in ~50% of human lung and breast cancers, acting as an oncogenic transcription factor. We previously demonstrated that Manuka honey (MH) inhibits p-STAT3 in breast cancer cells, but the exact mechanism remained unknown. Herein, we show that MH-mediated inhibition of p-STAT3 in breast (MDA-MB-231) and lung (A549) cancer cell lines is accompanied by decreased levels of gp130 and p-JAK2, two upstream components of the IL-6 receptor (IL-6R) signaling pathway. Using an ELISA-based assay, we demonstrate that MH binds directly to IL-6Rα, significantly inhibiting (~60%) its binding to the IL-6 ligand. Importantly, no evidence of MH binding to two other cytokine receptors, IL-11Rα and IL-8R, was found. Moreover, MH did not alter the levels of tyrosine-phosphorylated or total Src family kinases, which are also constitutively activated in cancer cells, suggesting that signaling via other growth factor receptors is unaffected by MH. Binding of five major MH flavonoids (luteolin, quercetin, galangin, pinocembrin, and chrysin) was also tested, and all but pinocembrin could demonstrably bind IL-6Rα, partially (30-35%) blocking IL-6 binding at the highest concentration (50 μM) used. In agreement, each flavonoid inhibited p-STAT3 in a dose-dependent manner, with estimated IC50 values in the 3.5-70 μM range. Finally, docking analysis confirmed the capacity of each flavonoid to bind in an energetically favorable configuration to IL-6Rα at a site predicted to interfere with ligand binding. Taken together, our findings identify IL-6Rα as a direct target of MH and its flavonoids, highlighting IL-6R blockade as a mechanism for the anti-tumor activity of MH, as well as a viable therapeutic target in IL-6-dependent cancers.

Nobiletin Inhibits Cell Viability via the SRC/AKT/STAT3/YY1AP1 Pathway in Human Renal Carcinoma Cells

Nobiletin is a polymethoxy flavonoid isolated from Citrus depressa and Citrus reticulata. It has been reported that nobiletin can suppress tumors. We primarily explored the antitumor effects of nobiletin and the associated potential mechanisms in ACHN and Caki-2 renal carcinoma cells. A CCK-8 assay and cloning experiments were used to assess cell viability, and a transwell assay and scratch test were used to assess metastatic ability. The cell cycle was analyzed by flow cytometry, whereas apoptosis was analyzed using flow cytometry and a terminal dexynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay. Protein expression was examined by Western blot and immunofluorescence. Renal cancer cells were subcutaneously transplanted into nude mice for in vivo studies. The data showed that nobiletin administration significantly dose- and time-dependently suppressed renal cancer cell proliferation; moreover, nobiletin treatment induced cell cycle arrest in the G0/G1 phase and promoted apoptosis. Immunofluorescence analysis indicated that nobiletin decreased the nuclear localization of signal transducer and activator of transcription 3 (STAT3) and YY1-associated protein 1 (YY1AP1). Western blot showed that the levels of phosphorylated SRC, phosphorylated AKT serine/threonine kinase (AKT), and phosphorylated STAT3 were decreased, whereas that of phosphorylated YY1AP1 was increased. The results further showed that application of insulin-like growth factor 1 (IGF1) was able to reverse the nobiletin-induced changes in the levels of phosphorylated AKT, phosphorylated STAT3, and phosphorylated YY1AP1, and could also reverse the antitumor effects of nobiletin. The results of in vivo experiments showed that, compared to the control, tumor volume and weight were both reduced following nobiletin treatment. In conclusion, our study demonstrated that nobiletin can inhibit renal carcinoma cell viability and provides a novel therapeutic approach for the treatment of kidney cancer.