The coiled-coil domain of Stat3 is essential for its SH2 domain-mediated receptor binding and subsequent activation induced by epidermal growth factor and interleukin-6

JAK-STAT Signaling in Autoimmunity and Cancer

The JAK-STAT pathway is an essential cell survival signaling that regulates gene expressions related to inflammation, immunity and cancer. Cytokine receptors, signal transducer and activator of transcription (STAT) proteins, and Janus kinases (JAKs) are the critical component of this signaling cascade. When JAKs are stimulated by cytokines, STAT phosphorylation, dimerization, and nuclear translocation occur, which eventually impacts gene transcription. Dysregulation of JAK-STAT signaling is linked with various autoimmune diseases, including rheumatoid arthritis, psoriasis, and inflammatory bowel disease. This pathway is constitutively activated in human malignancies and leads to tumor cell survival, proliferation, and immune evasion. Oncogenic mutations in the JAK and STAT genes have been found in solid tumors, leukemia, and lymphoma. Targeting the JAK-STAT pathway is a viable and promising therapeutic strategy for the treatment of autoimmune diseases and cancers.

STAT3 signaling enhances tissue expansion during postimplantation mouse development

Signal transducer and activator of transcription (STAT)3 signaling has been studied extensively using mouse embryonic stem cells. Zygotic deletion of Stat3 enables embryo implantation, but thereafter, mutants resemble non-affected littermates from the previous day until around mid-gestation. This probably results from the loss of serine-phosphorylated STAT3, the predominant form in early postimplantation embryonic tissues associated with mitochondrial activity. Bulk RNA sequencing of isolated mouse epiblasts confirmed developmental delay transcriptionally. Single-cell RNA sequencing revealed the exclusion of derivatives of Stat3 null embryonic stem cells exclusively from the erythroid lineage of mid-gestation chimeras. We show that Stat3 null embryonic stem cells can differentiate into erythroid and hematopoietic lineages in vitro but become outcompeted when mixed with wild-type cells. Our results implicate a role for STAT3 in the temporal control of embryonic progression, particularly in tissues requiring rapid cell division, such as postimplantation epiblast and hematopoietic lineages. Interestingly, mutations in STAT3 are associated with short stature in humans.

An allosteric inhibitor targeting the STAT3 coiled-coil domain selectively suppresses proliferation of breast cancer

Signal transducer and activator of transcription 3 (STAT3) remains a challenging and attractive therapeutic target in cancer research. The coiled-coil domain (CCD) of STAT3 represents a novel site for targeted intervention, distinct from the Src-homology 2 domain, and plays a crucial role in regulating the earlier activation and biological function of STAT3 in cell proliferation, survival and invasion of breast cancer cells. We previously reported K116, N'-(1-(2,4-dihydroxyphenyl)ethylidene)thiophene-2-carbohydrazide, as a potent allosteric inhibitor specifically targeting the STAT3 CCD. This study aimed to investigate the antiproliferation effect of K116 on breast cancer cells in vitro and in vivo. The results showed that K116 inhibited the proliferation of breast cancer cell lines in a dose-dependent manner by reducing the phosphorylation of STAT3 Lyr705 and did not inhibit the proliferation of HGC-27 and A549 cells nor their STAT3 Lyr705 phosphorylation. Compared with Stattic (STAT3 SH2 inhibitor), K116 selectively inhibited the proliferation of breast cancer cells. Furthermore, K116 (20 μM) directly monitored STAT3 stabilization and engagement within MDA-MB-468 cells, without affecting STAT1, STAT5, and Akt1. K116 induced apoptosis and inhibited migration as well as pY705STAT3 nuclear translocation and transcriptional activity of STAT3. In addition, K116 (30 mg kg-1) markedly suppressed tumor growth and inhibited STAT3 activity in a 4T1 cell-derived murine breast cancer model. Overall, our results provided pharmacological evidence supporting future clinical investigation of K116 as a promising STAT3 CCD allosteric inhibitor for breast cancer treatment.

Investigating the Potential Therapeutic Targeting of the JAK-STAT Pathway in Cerebrovascular Diseases: Opportunities and Challenges

Cerebrovascular disease (CVD) is a significant neurological condition resulting from pathological changes in the brain's blood supply and is currently the leading cause of death and disability worldwide. The progression of CVD is closely associated with endothelial damage, plaque formation, and thrombosis, driven by long-term alterations in vascular endothelial cells, smooth muscle cells, microglia, and other immune-inflammatory cells. Among the key molecular pathways involved, the Janus kinase/signal transducer and activator of transcription (JAK-STAT) signaling pathway plays a central role. Dysregulation of the JAK-STAT pathway is implicated in the pathogenesis of CVD by influencing the aforementioned cell types and associated pathological processes. Importantly, the role of the JAK-STAT pathway varies across different types of CVD and throughout different stages of disease progression (e.g., pre-morbid, acute, and chronic phases). This review examines the composition, activation, and regulation of the JAK-STAT pathway and summarizes recent findings on its involvement in CVD. We discuss the distinct roles of JAK-STAT signaling in various CVD conditions, the potential reasons for these differences, and explore the clinical translational prospects and technical challenges of targeting the JAK-STAT pathway for therapeutic intervention in CVD.

Novel carbazole attenuates vascular remodeling through STAT3/CIAPIN1 signaling in vascular smooth muscle cells

This study investigated the molecular mechanism of phenotypic switching of vascular smooth muscle cells (VSMCs), which play a crucial role in vascular remodeling using 9H-Carbazol-3-yl 4-aminobenzoate (CAB). CAB significantly attenuated platelet-derived growth factor (PDGF)-induced VSMC proliferation and migration. CAB suppressed PDGF-induced STAT3 activation by directly binding to the SH2 domain of STAT3. Downregulation of STAT3 phosphorylation by CAB attenuated CIAPIN1/JAK2/STAT3 axis through a decrease in CIAPIN1 transcription. Furthermore, abrogated CIAPIN1 decreased KLF4-mediated VSMC dedifferentiation and increased CDKN1B-induced cell cycle arrest and MMP9 suppression. CAB inhibited intimal hyperplasia in injury-induced neointima animal models by inhibition of the CIAPIN1/JAK2/STAT3 axis. However, CIAPIN1 overexpression attenuated CAB-mediated suppression of VSMC proliferation, migration, phenotypic switching, and intimal hyperplasia. Our study clarified the molecular mechanism underlying STAT3 inhibition of VSMC phenotypic switching and vascular remodeling and identified novel active CAB. These findings demonstrated that STAT3 can be a major regulator to control CIAPIN1/JAK2/STAT3 axis that may be a therapeutic target for treating vascular proliferative diseases.

Computational screening and molecular dynamics of natural compounds targeting the SH2 domain of STAT3: a multitarget approach using network pharmacology

SH2 (Src Homology 2) domains play a crucial role in phosphotyrosine-mediated signaling and have emerged as promising drug targets, particularly in cancer therapy. STAT3 (Signal Transducer and Activator of Transcription 3), which contains an SH2 domain, plays a pivotal role in cancer progression and immune evasion because it facilitates the dimerization of STAT3, which is essential for their activation and subsequent nuclear translocation. SH2 domain-mediated STAT3 inhibition disrupts this binding, reduces phosphorylation of STAT3, and impairs dimerization. This study employed an in silico approach to screen potential natural compounds that could target the SH2 domain of STAT3 and inhibit its function. The phytomolecules (182455) were retrieved from the ZINC 15 database and were docked using various modes like HTVS, SP, and XP. The phytomolecules exhibiting higher binding affinity were selected. MM-GBSA was performed to determine binding free energy, and the QikProp tool was utilized to assess the pharmacokinetic properties of potential hit compounds, narrowing down the list of candidates. Molecular dynamics simulations, thermal MM-GBSA, and WaterMap analysis were performed on compounds that exhibited favorable binding affinities and pharmacokinetic characteristics. Based on docking scores and binding interactions, ZINC255200449, ZINC299817570, ZINC31167114, and ZINC67910988 were identified as potential STAT3 inhibitors. ZINC67910988 demonstrated superior stability in molecular dynamics simulation and WaterMap analysis. Furthermore, DFT was performed to determine energetic and electronic properties, and HOMO and LUMO sites were predicted for electronic structure calculation. Additionally, network pharmacology was performed to map the compounds' interactions within biological networks, highlighting their multitarget potential. Compound-target networks elucidate the relationships between compounds and multiple targets, along with their associated pathways and help to minimize off-target effects. The identified lead compound showed strong potential as a STAT3 inhibitor, warranting further validation through in vitro and in vivo studies.

Rlip76 in ageing and Alzheimer's disease: Focus on oxidative stress and mitochondrial mechanisms

RLIP76 (Rlip), a stress-responsive protein, plays a multifaceted role in cellular function. This protein acts primarily as a glutathione-electrophile conjugate (GS-E) transporter, crucial for detoxifying hazardous compounds and converting them into mercapturic acids. RLIP76 also modulates cytoskeletal motility and membrane plasticity through its role in the Ral-signaling pathway, interacting with RalA and RalB, key small GTPases involved in growth and metastasis. Beyond its ATP-dependent transport functions in various tissues, RLIP76 also demonstrates GTPase Activating Protein (GAP) activity towards Rac1 and Cdc42, with a preference for Ral-GTP over Ral-GDP. Its functions span critical physiological processes including membrane dynamics, oxidative stress response, and mitochondrial dynamics. The protein's widespread expression and evolutionary conservation underscore its significance. Our lab discovered that Rlip interacts with Alzheimer's disease (AD) proteins, amyloid beta and phosphorylated and induce oxidative stress, mitochondrial dysfnction and synaptic damage in AD. Our in vitro studies revealed that overexpression of Rlip reduces mitochondrial abnormalities. Further, our in vivo studies (Rlip+/- mice) revealed that a partial reduction of Rlip in mice (Rlip+/-), leads to mitochondrial abnormalities, elevated oxidative stress, and cognitive deficits resembling late-onset AD, emphasizing the protein's crucial role in neuronal health and disease. Finally, we discuss the experimental cross-breedings of overexpression of mice Rlip TG/TG or Rlip + /- mice with Alzheimer's disease models - earlyonset 5XFAD, late-onset APPKI and Tau transgenic mice, providing new insights into RLIP76's role in AD progression and development. This review summarizes RLIP76's structure, function, and cellular pathways, highlighting its implications in AD and its potential as a therapeutic target.

A novel STAT3 CCD inhibitor for suppressing macrophage activation and lipopolysaccharide-induced acute lung injury

BACKGROUND

Signal transducer and activator of transcription 3 (STAT3) has a crucial role in inflammation in lipopolysaccharide (LPS)-induced acute lung injury (ALI). The current study aimed at developing a novel STAT3 coiled-coil domain (CCD) inhibitor for suppression of inflammatory response in LPS-induced ALI.

METHOD

Molecular docking and binding affinity were proceeded and determined that K134 bond to STAT3 CCD. Then K134 [(E)-N'-(1-(2,4-dihydroxyphenyl)ethylidene)-2-(o-tolyloxy)acetohydrazide] was applied to RAW264.7 macrophages for further ex vivo investigation of possible mechanism. The intratracheal injection of LPS-induced ALI model of C57BL/6j mice was established for evaluating therapeutic effect of K134 on ALI and inflammation in vivo. iNOS and pro-inflammatory cytokines, including TNF-α, IL-1β and IL-6, in BALF of LPS-induced ALI were also determined.

RESULTS

Molecular docking results disclosed that Asn175 and Gln202 were involved in K134 binding to STAT3 CCD and its binding affinity was at 4.68 μM. Moreover, further tests showed that K134 blunted activation and the subsequent STAT3 phosphorylation in LPS-treated macrophages. Also, K134 (30 mg/kg) alleviated LPS-induced lung injury and blocked STAT3 phosphorylation in lung. Further, K134 decreased iNOS, pro-inflammatory cytokines, inflammatory cell infiltration and NO production of LPS-induced ALI. Preliminary safety evaluation indicated that K134 had a favorable safety profile at the dose of 30 mg/kg.

CONCLUSIONS

We identified a novel inhibitor of STAT3 CCD, K134, which markedly attenuated LPS-induced ALI inflammation by targeting STAT3 phosphorylation. This supports a possible future use of K134 in treating inflammatory diseases involving activation of STAT3-mediated pathways.

Medicinal chemistry perspective of JAK inhibitors: synthesis, biological profile, selectivity, and structure activity relationship

JAK-STAT signalling pathway was discovered more than quarter century ago. The JAK-STAT pathway protein is considered as one of the crucial hubs for cytokine secretion which mediates activation of different inflammatory, cellular responses and hence involved in different etiological factors. The various etiological factors involved are haematopoiesis, immune fitness, tissue repair, inflammation, apoptosis, and adipogenesis. The presence of the active mutation V617K plays a significant role in the progression of the JAK-STAT pathway-related disease. Consequently, targeting the JAK-STAT pathway could be a promising therapeutic approach for addressing a range of causative factors. In this current review, we provided a comprehensive discussion for the in-detail study of anatomy and physiology of the JAK-STAT pathway which contributes structural domain rearrangement, activation, and negative regulation associated with the downstream signaling pathway, relationship between different cytokines and diseases. This review also discussed the recent development of clinical trial entities. Additionally, this review also provides updates on FDA-approved drugs. In the current investigation, we have classified recently developed small molecule inhibitors of JAK-STAT pathway according to different chemical classes and we emphasized their synthetic routes, biological evaluation, selectivity, and structure-activity relationship.

Inhibition of STAT3: A promising approach to enhancing the efficacy of chemotherapy in medulloblastoma

Medulloblastoma is a type of brain cancer that primarily affects children. While chemotherapy has been shown to be effective in treating medulloblastoma, the development of chemotherapy resistance remains a challenge. One potential therapeutic approach is to selectively inhibit the inducible transcription factor called STAT3, which is known to play a crucial role in the survival and growth of tumor cells. The activation of STAT3 has been linked to the growth and progression of various cancers, including medulloblastoma. Inhibition of STAT3 has been shown to sensitize medulloblastoma cells to chemotherapy, leading to improved treatment outcomes. Different approaches to STAT3 inhibition have been developed, including small-molecule inhibitors and RNA interference. Preclinical studies have shown the efficacy of STAT3 inhibitors in medulloblastoma, and clinical trials are currently ongoing to evaluate their safety and effectiveness in patients with various solid tumors, including medulloblastoma. In addition, researchers are also exploring ways to optimize the use of STAT3 inhibitors in combination with chemotherapy and identify biomarkers that can predict treatment that will help to develop personalized treatment strategies. This review highlights the potential of selective inhibition of STAT3 as a novel approach for the treatment of medulloblastoma and suggests that further research into the development of STAT3 inhibitors could lead to improved outcomes for patients with aggressive cancer.

Exploring Novel Frontiers: Leveraging STAT3 Signaling for Advanced Cancer Therapeutics

Signal Transducer and Activator of Transcription 3 (STAT3) plays a significant role in diverse physiologic processes, including cell proliferation, differentiation, angiogenesis, and survival. STAT3 activation via phosphorylation of tyrosine and serine residues is a complex and tightly regulated process initiated by upstream signaling pathways with ligand binding to receptor and non-receptor-linked kinases. Through downstream deregulation of target genes, aberrations in STAT3 activation are implicated in tumorigenesis, metastasis, and recurrence in multiple cancers. While there have been extensive efforts to develop direct and indirect STAT3 inhibitors using novel drugs as a therapeutic strategy, direct clinical application remains in evolution. In this review, we outline the mechanisms of STAT3 activation, the resulting downstream effects in physiologic and malignant settings, and therapeutic strategies for targeting STAT3. We also summarize the pre-clinical and clinical evidence of novel drug therapies targeting STAT3 and discuss the challenges of establishing their therapeutic efficacy in the current clinical landscape.

Role of STAT3 in pancreatic cancer

Pancreatic cancer remains a serious and deadly disease, impacting people globally. There remain prominent gaps in the current understanding of the disease, specifically regarding the role of the signal transducer and activator of transcription (STAT) family of proteins in pancreatic tumors. STAT proteins, particularly STAT3, play important roles in pancreatic cancer, especially pancreatic ductal adenocarcinoma (PDAC), which is the most prevalent histotype. The role of STAT3 across a continuum of molecular processes, such as PDAC tumorigenesis and progression, immune escape, drug resistance and stemness, and modulation of the tumor microenvironment (TME), are only a tip of the iceberg. In some ways, the role of STAT3 in PDAC may hold greater importance than that of oncogenic Kirsten rat sarcoma virus (KRAS). This makes STAT3 a highly attractive target for developing targeted therapies for the treatment of pancreatic cancer. In this review, the current knowledge of STAT3 in pancreatic cancer has been summarized, particularly relating to STAT3 activation in cancer cells, cells of the TME, and the state of targeting STAT3 in pre-clinical and clinical trials of PDAC.

Natural bioactive compounds and STAT3 against hepatocellular carcinoma: An update

Hepatocellular carcinoma (HCC) is a challenging and very fatal liver cancer. The signal transducer and activator of transcription 3 (STAT3) pathway is a crucial regulator of tumor development and are ubiquitously active in HCC. Therefore, targeting STAT3 has emerged as a promising approach for preventing and treating HCC. Various natural bioactive compounds (NBCs) have been proven to target STAT3 and have the potential to prevent and treat HCC as STAT3 inhibitors. Numerous kinds of STAT3 inhibitors have been identified, including small molecule inhibitors, peptide inhibitors, and oligonucleotide inhibitors. Due to the undesirable side effects of the conventional therapeutic drugs against HCC, the focus is shifted to NBCs derived from plants and other natural sources. NBCs can be broadly classified into the categories of terpenes, alkaloids, carotenoids, and phenols. Most of the compounds belong to the family of terpenes, which prevent tumorigenesis by inhibiting STAT3 nuclear translocation. Further, through STAT3 inhibition, terpenes downregulate matrix metalloprotease 2 (MMP2), matrix metalloprotease 9 (MMP9) and vascular endothelial growth factor (VEGF), modulating metastasis. Terpenes also suppress the anti-apoptotic proteins and cell cycle markers. This review provides comprehensive information related to STAT3 abrogation by NBCs in HCC with in vitro and in vivo evidences.

Immunological dimensions of neuroinflammation and microglial activation: exploring innovative immunomodulatory approaches to mitigate neuroinflammatory progression

The increasing life expectancy has led to a higher incidence of age-related neurodegenerative conditions. Within this framework, neuroinflammation emerges as a significant contributing factor. It involves the activation of microglia and astrocytes, leading to the release of pro-inflammatory cytokines and chemokines and the infiltration of peripheral leukocytes into the central nervous system (CNS). These instances result in neuronal damage and neurodegeneration through activated nucleotide-binding domain and leucine-rich repeat containing (NLR) family pyrin domain containing protein 3 (NLRP3) and nuclear factor kappa B (NF-kB) pathways and decreased nuclear factor erythroid 2-related factor 2 (Nrf2) activity. Due to limited effectiveness regarding the inhibition of neuroinflammatory targets using conventional drugs, there is challenging growth in the search for innovative therapies for alleviating neuroinflammation in CNS diseases or even before their onset. Our results indicate that interventions focusing on Interleukin-Driven Immunomodulation, Chemokine (CXC) Receptor Signaling and Expression, Cold Exposure, and Fibrin-Targeted strategies significantly promise to mitigate neuroinflammatory processes. These approaches demonstrate potential anti-neuroinflammatory effects, addressing conditions such as Multiple Sclerosis, Experimental autoimmune encephalomyelitis, Parkinson's Disease, and Alzheimer's Disease. While the findings are promising, immunomodulatory therapies often face limitations due to Immune-Related Adverse Events. Therefore, the conduction of randomized clinical trials in this matter is mandatory, and will pave the way for a promising future in the development of new medicines with specific therapeutic targets.

DBF4 Dependent Kinase Inhibition Suppresses Hepatocellular Carcinoma Progression and Potentiates Anti-Programmed Cell Death-1 Therapy

The progression of hepatocellular carcinoma (HCC) remains a huge clinical challenge, and elucidation of the underlying molecular mechanisms is critical to develop effective therapeutic strategy. Dumbbell former 4 (DBF4) complexes with cell division cycle 7 (CDC7) to form DBF4-dependent kinase (DDK), playing instrumental roles in tumor cell survival, whereas its roles in HCC remain elusive. This study revealed that DBF4 expression was upregulated in HCC and constituted an independent prognostic factor of patient survival. We identified p65 as an upstream inducer which increased DBF4 expression by directly binding to its promoter. DBF4 accelerated HCC cell proliferation and tumorigenesis in vitro and in vivo. Mechanistically, DBF4 complexed with CDC7 to bind to the coiled coil domain of STAT3 and activate STAT3 signaling through XPO1-mediated nuclear exportation. Notably, p65 enhanced the nuclear transport of DDK and DDK-STAT3 interaction by transcriptionally upregulating XPO1. DBF4 expression positively correlated with activated STAT3 and XPO1 in HCC tissues. Furthermore, combining DDK inhibitor XL413 with anti-PD-1 immunotherapy dramatically suppressed HCC growth and prolonged the survival of HCC-bearing mouse. Our findings reveal that DDK activates STAT3 pathway and facilitates HCC progression, and demonstrate the proof of the concept of targeting DDK to improve the efficacy of HCC immunotherapy.

Regulation of the JAK/STAT signaling pathway: The promising targets for cardiovascular disease

Individuals have known that Janus kinase (JAK) signal transducer and activator of transcription (STAT) signaling pathway was involved in the growth of the cell, cell differentiation courses advancement, immune cellular survival, as well as hematopoietic system advancement. Researches in the animal models have already uncovered a JAK/STAT regulatory function in myocardial ischemia-reperfusion injury (MIRI), acute myocardial infarction (MI), hypertension, myocarditis, heart failure, angiogenesis and fibrosis. Evidences originating in these studies indicate a therapeutic JAK/STAT function in cardiovascular diseases (CVDs). In this retrospection, various JAK/STAT functions in the normal and ill hearts were described. Moreover, the latest figures about JAK/STAT were summarized under the background of CVDs. Finally, we discussed the clinical transformation prospects and technical limitations of JAK/STAT as the potential therapeutic targets for CVDs. This collection of evidences has essential meanings for the clinical application of JAK/STAT as medicinal agents for CVDs. In this retrospection, various JAK/STAT functions in the normal and ill hearts were described. Moreover, the latest figures about JAK/STAT were summarized under the background of CVDs. Finally, we discussed the clinical transformation prospects and toxicity of JAK/STAT inhibitors as potential therapeutic targets for CVDs. This collection of evidences has essential meanings for the clinical application of JAK/STAT as medicinal agents for CVDs.

JAK/STAT Signaling and Cervical Cancer: From the Cell Surface to the Nucleus

The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway constitutes a rapid signaling module from the cell surface to the nucleus, and activates different cellular responses, such as proliferation, survival, migration, invasion, and inflammation. When the JAK/STAT pathway is altered, it contributes to cancer progression and metastasis. STAT proteins play a central role in developing cervical cancer, and inhibiting the JAK/STAT signaling may be necessary to induce tumor cell death. Several cancers show continuous activation of different STATs, including cervical cancer. The constitutive activation of STAT proteins is associated with a poor prognosis and overall survival. The human papillomavirus (HPV) oncoproteins E6 and E7 play an essential role in cervical cancer progression, and they activate the JAK/STAT pathway and other signals that induce proliferation, survival, and migration of cancer cells. Moreover, there is a crosstalk between the JAK/STAT signaling cascade with other signaling pathways, where a plethora of different proteins activate to induce gene transcription and cell responses that contribute to tumor growth. Therefore, inhibition of the JAK/STAT pathway shows promise as a new target in cancer treatment. In this review, we discuss the role of the JAK/STAT pathway components and the role of the HPV oncoproteins associated with cellular malignancy through the JAK/STAT proteins and other signaling pathways to induce tumor growth.

Evolving cognition of the JAK-STAT signaling pathway: autoimmune disorders and cancer

The Janus kinase (JAK) signal transducer and activator of transcription (JAK-STAT) pathway is an evolutionarily conserved mechanism of transmembrane signal transduction that enables cells to communicate with the exterior environment. Various cytokines, interferons, growth factors, and other specific molecules activate JAK-STAT signaling to drive a series of physiological and pathological processes, including proliferation, metabolism, immune response, inflammation, and malignancy. Dysregulated JAK-STAT signaling and related genetic mutations are strongly associated with immune activation and cancer progression. Insights into the structures and functions of the JAK-STAT pathway have led to the development and approval of diverse drugs for the clinical treatment of diseases. Currently, drugs have been developed to mainly target the JAK-STAT pathway and are commonly divided into three subtypes: cytokine or receptor antibodies, JAK inhibitors, and STAT inhibitors. And novel agents also continue to be developed and tested in preclinical and clinical studies. The effectiveness and safety of each kind of drug also warrant further scientific trials before put into being clinical applications. Here, we review the current understanding of the fundamental composition and function of the JAK-STAT signaling pathway. We also discuss advancements in the understanding of JAK-STAT-related pathogenic mechanisms; targeted JAK-STAT therapies for various diseases, especially immune disorders, and cancers; newly developed JAK inhibitors; and current challenges and directions in the field.

Pharmacological updates of nifuroxazide: Promising preclinical effects and the underlying molecular mechanisms

Nifuroxazide (NFX) is a safe nitrofuran antibacterial drug used clinically to treat acute diarrhea and infectious traveler diarrhea or colitis. Recent studies revealed that NFX displays multiple pharmacological effects, including anticancer, antioxidant, and anti-inflammatory effects. NFX has potential roles in inhibiting thyroid, breast, lung, bladder, liver, and colon cancers and osteosarcoma, melanoma, and others mediated by suppressing STAT3 as well as ALDH1, MMP2, MMP9, Bcl2 and upregulating Bax. Moreover, it has promising effects against sepsis-induced organ injury, hepatic disorders, diabetic nephropathy, ulcerative colitis, and immune disorders. These promising effects appear to be mediated by suppressing STAT3 as well as NF-κB, TLR4, and β-catenin expressions and effectively decreasing downstream cytokines TNF-α, IL-1β, and IL-6. Our review summarizes the available studies on the molecular biological mechanisms of NFX in cancer and other diseases and it is recommended to translate the studies in experimental animals and cultured cells and repurpose NFX in various diseases for scientific evidence based on human studies.

Aberrant function of pathogenic STAT3 mutant proteins is linked to altered stability of monomers and homodimers

STAT3 mutations, predominantly in the DNA-binding domain (DBD) and Src-homology 2 domain (SH2D), cause rare cases of immunodeficiency, malignancy, and autoimmunity. The exact mechanisms by which these mutations abrogate or enhance STAT3 function are not completely understood. Here, we examined how loss-of-function (LOF) and gain-of-function (GOF) STAT3 mutations within the DBD and SH2D affect monomer and homodimer protein stability as well as their effect on key STAT3 activation events, including recruitment to phosphotyrosine (pY) sites within peptide hormone receptors, tyrosine phosphorylation at Y705, dimerization, nuclear translocation, and DNA binding. The DBD LOF mutants showed reduced DNA binding when homodimerized, whereas the DBD GOF mutants showed increased DNA binding. DBD LOF and GOF mutants showed minimal changes in other STAT3 functions or in monomer or homodimer protein stability. However, SH2D LOF mutants demonstrated reduced conformational stability as either monomers or homodimers, leading to decreased pY-peptide recruitment, tyrosine phosphorylation, dimerization, nuclear localization, and DNA binding. In contrast, cancer-causing SH2D GOF mutants showed increased STAT3 homodimer stability, which increased their DNA binding. Of note, a small-molecule inhibitor of STAT3 that targets the tyrosine phosphopeptide-binding pocket within the STAT3 SH2D potently inhibited cell proliferation driven by STAT3 SH2D GOF mutants. These findings indicate that the stability of STAT3 protein monomer and homodimer is critical for the pathogenesis of diseases caused by SH2D LOF and GOF mutations and suggest that agents that modulate STAT3 monomer and/or homodimer protein stability may have therapeutic value in diseases caused by these mutations.

Genomic distribution of signal transducer and activator of transcription (STAT) family in colorectal cancer

JAK/STAT pathway has been widely acknowledged in the development of human cancers. However, the role of different phosphorylated STAT proteins translocating into nucleus in transcription activation of target genes is not fully understood. In present research, ChIP-seq was carried on to investigate the genome-wide distribution of the activated STAT1, STAT2, STAT3, STAT5 and STAT6 in colorectal cancer HCT-116 cells. Our observations indicated that the homodimers rather than heterodimers of STAT protein predominantly occupied on genomic DNA. STAT3 accounted for the largest proportion among all STAT proteins HCT-116 cells. Furthermore, the biased binding motif targeted by different STAT homodimers suggested the distinct biological functions. Here, we noticed that NR5A2 was a specific co-activator of STAT3 by DNA motif analysis. Co-IP assay determined that NR5A2 indeed interacted with STAT3 homodimer rather than other homodimers or heterodimers. NR5A2 knockdown resulted in a reduced binding affinity of STAT3 homodimer in the original regions. Taken together, we characterize the genome-wide landscape of activated STAT proteins, and reveal the differences of binding patterns as well as the target genes and associated functions between homodimer and heterodimer of STAT proteins in HCT-116 cells. We also present some new findings and possible mechanisms regarding the role of NR5A2 on STAT3 in CRC. Our findings may provide new insights into the design of STAT inhibitors to treat CRC and other diseases.

Identifying NFKB1, STAT3, and CDKN1A as Baicalein's Potential Hub Targets in Parkinson's Disease-related α-synuclein-mediated Pathways by Integrated Bioinformatics Strategies

BACKGROUND

The overexpression, accumulation, and cell-to-cell transmission of α-synuclein leads to the deterioration of Parkinson's disease (PD). Previous studies suggest that Baicalein (BAI) can bind to α-synuclein and inhibit α-synuclein aggregation and secretion. However, it is still unclear whether BAI can intervene with the pathogenic molecules in α-synuclein-mediated PD pathways beyond directly targeting α-synuclein per se.

METHODS

This study aimed to systematically investigate BAI's potential targets in PD-related A53T mutant α-synuclein-mediated pathways by integrating data mining, network pharmacological analysis, and molecular docking simulation techniques.

RESULTS

The results suggest that BAI may target genes that are dysregulated in synaptic transmission, vesicle trafficking, gene transcription, protein binding, extracellular matrix formation, and kinase activity in α-synucleinmediated pathways. NFKB1, STAT3, and CDKN1A are BAI's potential hub targets in these pathways.

CONCLUSION

Our findings highlight BAI's potentiality to modulate α-synuclein-mediated pathways beyond directly targeting α-synuclein per se.

Requirement for STAT3 and its target, TFCP2L1, in self-renewal of naïve pluripotent stem cells in vivo and in vitro

We previously demonstrated gradual loss of epiblast during diapause in embryos lacking components of the LIF/IL6 receptor. Here, we explore the requirement for the downstream signalling transducer andactivator of transcription STAT3 and its target, TFCP2L1, in maintenance of naïve pluripotency. Unlike conventional markers, such as NANOG, which remains high in epiblast until implantation, both STAT3 and TFCP2L1 proteins decline during blastocyst expansion, but intensify in the embryonic region after induction of diapause, as observed visually and confirmed using our image-analysis pipeline, consistent with our previous transcriptional expression data. Embryos lacking STAT3 or TFCP2L1 underwent catastrophic loss of most of the inner cell mass during the first few days of diapause, indicating involvement of signals in addition to LIF/IL6 for sustaining naïve pluripotency in vivo. By blocking MEK/ERK signalling from the morula stage, we could derive embryonic stem cells with high efficiency from STAT3 null embryos, but not those lacking TFCP2L1, suggesting a hitherto unknown additional role for this essential STAT3 target in transition from embryo to embryonic stem cells in vitro. This article has an associated First Person interview with the first author of the paper.

The JAK-STAT Signaling Pathway in Epilepsy

Epilepsy is defined as spontaneous recurrent seizures in the brain. There is increasing evidence that inflammatory mediators and immune cells are involved in epileptic seizures. As more research is done on inflammatory factors and immune cells in epilepsy, new targets for the treatment of epilepsy will be revealed. The Janus kinase-signal transducer and transcriptional activator (JAKSTAT) signaling pathway is strongly associated with many immune and inflammatory diseases, At present, more and more studies have found that the JAK-STAT pathway is involved in the development and development of epilepsy, indicating the JAK-STAT pathway's potential promise as a target in epilepsy treatment. In this review, we discuss the composition, activation, and regulation of the JAK-STAT pathway and the relationship between the JAK-STAT pathway and epilepsy. In addition, we summarize the common clinical inhibitors of JAK and STAT that we would expect to be used in epilepsy treatment in the future.

Allosteric regulation in STAT3 interdomains is mediated by a rigid core: SH2 domain regulation by CCD in D170A variant

Signal Transducer and Activator of Transcription 3 (STAT3) plays a crucial role in cancer development and thus is a viable target for cancer treatment. STAT3 functions as a dimer mediated by phosphorylation of the SRC-homology 2 (SH2) domain, a key target for therapeutic drugs. While great efforts have been employed towards the development of compounds that directly target the SH2 domain, no compound has yet been approved by the FDA due to a lack of specificity and pharmacologic efficacy. Studies have shown that allosteric regulation of SH2 via the coiled-coil domain (CCD) is an alternative drug design strategy. Several CCD effectors have been shown to modulate SH2 binding and affinity, and at the time of writing at least one drug candidate has entered phase I clinical trials. However, the mechanism for SH2 regulation via CCD is poorly understood. Here, we investigate structural and dynamic features of STAT3 and compare the wild type to the reduced function variant D170A in order to delineate mechanistic differences and propose allosteric pathways. Molecular dynamics simulations were employed to explore conformational space of STAT3 and the variant, followed by structural, conformation, and dynamic analysis. The trajectories explored show distinctive conformational changes in the SH2 domain for the D170A variant, indicating long range allosteric effects. Multiple analyses provide evidence for long range communication pathways between the two STAT3 domains, which seem to be mediated by a rigid core which connects the CCD and SH2 domains via the linker domain (LD) and transmits conformational changes through a network of short-range interactions. The proposed allosteric mechanism provides new insight into the understanding of intramolecular signaling in STAT3 and potential pharmaceutical control of STAT3 specificity and activity.

STAT3 Inhibitors: A Novel Insight for Anticancer Therapy of Pancreatic Cancer

The signal transducer and activator of transcription (STAT) is a family of intracellular cytoplasmic transcription factors involved in many biological functions in mammalian signal transduction. Among them, STAT3 is involved in cell proliferation, differentiation, apoptosis, and inflammatory responses. Despite the advances in the treatment of pancreatic cancer in the past decade, the prognosis for patients with pancreatic cancer remains poor. STAT3 has been shown to play a pro-cancer role in a variety of cancers, and inhibitors of STAT3 are used in pre-clinical and clinical studies. We reviewed the relationship between STAT3 and pancreatic cancer and the latest results on the use of STAT3 inhibitors in pancreatic cancer, with the aim of providing insights and ideas around STAT3 inhibitors for a new generation of chemotherapeutic modalities for pancreatic cancer.

Molecular mechanism, regulation, and therapeutic targeting of the STAT3 signaling pathway in esophageal cancer (Review)

Esophageal cancer (EC) is the seventh most common cancer globally, and the overall 5‑year survival rate is only 20%. Signal transducer and activator of transcription 3 (STAT3) is aberrantly activated in EC, and its activation is associated with a poor prognosis. STAT3 can be activated by canonical pathways such as the JAK/STAT3 pathway as well as non‑canonical pathways including the Wnt/STAT3 and COX2/PGE2/STAT3 pathways. Activated STAT3, present as phosphorylated STAT3 (p‑STAT3), can be transported into the nucleus to regulate downstream genes, including VEGF, cyclin D1, Bcl‑xL, and matrix metalloproteinases (MMPs), to promote cancer cell proliferation and induce resistance to therapy. Non‑coding RNAs, including microRNAs (miRNAs/miRs), circular RNAs (circRNAs), and long non‑coding RNAs (lncRNAs), play a vital role in regulating the STAT3 signaling pathway in EC. Several miRNAs promote or suppress the function of STAT3 in EC, while lncRNAs and circRNAs primarily promote the effects of STAT3 and the progression of cancer. Additionally, various drugs and natural compounds can target STAT3 to suppress the malignant behavior of EC cells, providing novel insights into potential EC therapies.

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.

The JAK/STAT signaling pathway: from bench to clinic

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway was discovered more than a quarter-century ago. As a fulcrum of many vital cellular processes, the JAK/STAT pathway constitutes a rapid membrane-to-nucleus signaling module and induces the expression of various critical mediators of cancer and inflammation. Growing evidence suggests that dysregulation of the JAK/STAT pathway is associated with various cancers and autoimmune diseases. In this review, we discuss the current knowledge about the composition, activation, and regulation of the JAK/STAT pathway. Moreover, we highlight the role of the JAK/STAT pathway and its inhibitors in various diseases.

The JAK/STAT signaling pathway: from bench to clinic

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway was discovered more than a quarter-century ago. As a fulcrum of many vital cellular processes, the JAK/STAT pathway constitutes a rapid membrane-to-nucleus signaling module and induces the expression of various critical mediators of cancer and inflammation. Growing evidence suggests that dysregulation of the JAK/STAT pathway is associated with various cancers and autoimmune diseases. In this review, we discuss the current knowledge about the composition, activation, and regulation of the JAK/STAT pathway. Moreover, we highlight the role of the JAK/STAT pathway and its inhibitors in various diseases.

Epigenetic Signaling of Cancer Stem Cells During Inflammation

Malignant tumors pose a great challenge to human health, which has led to many studies increasingly elucidating the tumorigenic process. Cancer Stem Cells (CSCs) have profound impacts on tumorigenesis and development of drug resistance. Recently, there has been increased interest in the relationship between inflammation and CSCs but the mechanism underlying this relationship has not been fully elucidated. Inflammatory cytokines produced during chronic inflammation activate signaling pathways that regulate the generation of CSCs through epigenetic mechanisms. In this review, we focus on the effects of inflammation on cancer stem cells, particularly the role of signaling pathways such as NF-κB pathway, STAT3 pathway and Smad pathway involved in regulating epigenetic changes. We hope to provide a novel perspective for improving strategies for tumor treatment.

STAT3 as a Potential Target for Tumor Suppressive Effects of 15-Deoxy-Δ12,14-prostaglandin J2 in Triple Negative Breast Cancer

STAT3 plays a prominent role in proliferation and survival of tumor cells. Thus, STAT3 has been considered to be a prime target for development of anti-cancer therapeutics. The electrophilic cyclopentenone prostaglandin,15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) has been well recognized for its capability to modulate intracellular signaling pathways involved in cancer cell growth and progression. We previously reported that 15d-PGJ₂ had potent cytotoxicity against harvey-ras transformed human mammary epithelial cells through direct interaction with STAT3. In this study, we have attempted to verify the inhibitory effects of 15d-PGJ₂ on STAT3 signaling in human breast tumor cells. The triple negative breast cancer cell lines, MDA-MB-231 and MDA-MB-468 displaying constitutive phosphorylation of STAT3 on the tyrosine 705 (Tyr705) residue, underwent apoptosis upon inhibition of STAT3 by 15d-PGJ₂. In contrast, estrogen receptor positive MCF-7 breast cancer cells that do not exhibit elevated STAT3 phosphorylation were much less susceptible to 15d-PGJ₂-induced apoptosis as assessed by PARP cleavage. Furthermore, 15d-PGJ₂ inhibited interleukin-6-induced tyrosine phosphorylation of STAT3 in LNCaP cells. According to molecular docking studies, 15d-PGJ₂ may preferentially bind to the cysteine 259 residue (Cys259) present in the coiled-coil domain of STAT3. Site-directed mutagenesis of STAT3 identified Cys259 to be the critical amino acid for the 15d-PGJ₂-induced apoptosis as well as epithelial-to-mesenchymal transition. Taken together, these findings suggest STAT3 inactivation through direct chemical modification of its Cys259 as a potential therapeutic approach for treatment of triple negative breast cancer treatment.

Requirement of Histone Deacetylase 6 for Interleukin-6 Induced Epithelial-Mesenchymal Transition, Proliferation, and Migration of Peritoneal Mesothelial Cells

Aims: Influenced by microenvironment, human peritoneal mesothelial cells (HPMCs) acquired fibrotic phenotype, which was identified as the protagonist for peritoneal fibrosis. In this study, we examined the role of histone deacetylase 6 (HDAC6) for interleukin-6 (IL-6) induced epithelial-mesenchymal transition (EMT), proliferation, and migration of HPMCs. Methods: The role of HDAC6 in IL-6-elicited EMT of HPMCs was tested by morphological observation of light microscope, immunoblotting, and immune-fluorescence assay; and the function of HDAC6 in proliferation and migration of HPMCs was examined by CCK-8 assay, wound healing experiment, and immunoblotting. Results: IL-6 stimulation significantly increased the expression of HDAC6. Treatment with tubastatin A (TA), a highly selective HDAC6 inhibitor, or silencing of HDAC6 with siRNA decreased the expression of HDAC6. Moreover, TA or HDAC6 siRNA suppressed IL-6-induced EMT, as evidenced by decreased expressions of α-SMA, Fibronectin, and collagen I and the preserved expression of E-cadherin in cultured HPMCs. Mechanistically, HDAC6 inhibition suppressed the expression of transforming growth factor β (TGFβ) receptor I (TGFβRI), phosphorylation of Smad3, secretion of connective tissue growth factor (CTGF), and transcription factor Snail. On the other hand, the pharmacological inhibition or genetic target of HDAC6 suppressed HPMCs proliferation, as evidenced by the decreased optical density of CCK-8 and the expressions of PCNA and Cyclin E. The migratory rate of HPMCs also decreased. Mechanistically, HDAC6 inhibition blocked the activation of JAK2 and STAT3. Conclusion: Our study illustrated that IL-6-induced HDAC6 not only regulated IL-6 itself downstream JAK2/STAT3 signaling but also co-activated the TGF-β/Smad3 signaling, leading to the change of the phenotype and mobility of HPMCs. HDAC6 could be a potential therapeutic target for the prevention and treatment of peritoneal fibrosis.

ZIPK activates the IL-6/STAT3 signaling pathway and promotes cisplatin resistance in gastric cancer cells

Gastric cancer is one of the most common malignant cancers globally. Chemotherapy resistance remains a major obstacle in the treatment of gastric cancer, and the molecular mechanisms underlying drug resistance are still not well understood. We previously reported that Zipper interacting protein kinase (ZIPK), also known as death‐associated protein kinase3, exerts an oncogenic effect on gastric cancer via activation of Akt/NF‐κB signaling and promotion of stemness. Here, we explored the roles of ZIPK in cisplatin resistance. We report that ZIPK enhances cell proliferation and invasion and reduces the antitumor activity of cisplatin in gastric cancer. In addition, our western blot data suggest that ZIPK activated the IL‐6/STAT3 signaling pathway. Furthermore, ZIPK increased the expression of IL‐6 and multidrug‐resistance genes. Using the STAT3 inhibitor stattic to block the IL‐6/STAT3 signaling pathway strongly increased the sensitivity of ZIPK‐expressed cells to cisplatin. In conclusion, ZIPK may play a role in cisplatin resistance through activation of the IL‐6/ STAT3 signaling pathway. Inhibition of STAT3 in gastric cancer overexpressing ZIPK might have potential to improve the efficacy of cisplatin.

Novel STAT-3 gain-of-function variant with hypogammaglobulinemia and recurrent infection phenotype

Signal transducer and activator of transcription 3 (STAT‐3) gain‐of‐function (GOF) syndrome is an early‐onset monogenic inborn error of immunity characterized by multi‐organ autoimmune disorders, growth failure and lymphoproliferation. We describe that STAT‐3 GOF syndrome may be presented with hypogammaglobulinemia and recurrent severe upper and lower respiratory tract infections. In addition, the patient had lymphoproliferation, short stature and interstitial lung disease. Chest computerized tomography examinations showed mild bronchiectasis with areas of non‐fibrosing alveolar‐interstitial disease and maldevelopment of bilateral first ribs. Using Sanger sequencing, we revealed a novel c.508G>C, p.D170H STAT‐3 variant affecting the coiled coil domain of STAT‐3. Functional studies confirmed that p.D170H was a GOF variant, as shown by increased phosphorylated STAT‐3 (pSTAT‐3) and STAT‐3 transcriptional activity. Our observation suggests that STAT‐3 GOF syndrome can manifest in early childhood with hypogammaglobulinemia and recurrent severe respiratory tract infections. We suggest that patients with lymphoproliferation, hypogammaglobulinemia and severe recurrent infections should be screened for STAT‐3 variants, even if autoimmune manifestations are missing.

Design and synthesis of 2-Substituted-4-benzyl-5-methylimidazoles as new potential Anti-breast cancer agents to inhibit oncogenic STAT3 functions

STAT3 signaling is known to be associated with tumorigenesis and further cancer cell-intrinsic activation of STAT3 leads to altered regulation of several oncogenic processes. Given the importance of STAT3 in cancer development and progression particularly breast cancer, it is crucial to discover new chemical entities of STAT3 inhibitor to develop anti-breast cancer drug candidates. Herein, 4-benzyl-2-benzylthio-5-methyl-1H-imidazole (2a) and 4-benzyl-5-methyl-2-[(2,6-difluorobenzyl)thio]-1H-imidazole (2d) from a group of thirty imidazole-bearing compounds showed greater STAT3 inhibition than their lead compounds VS1 and the oxadiazole derivative MD77. Within all tested compounds, ten derivatives effectively inhibited the growth of the two tested breast cancer cells with IC₅₀ values ranging from 6.66 to 26.02 µM. In addition, the most potent derivatives 2a and 2d inhibited the oncogenic function of STAT3 as seen in the inhibition of colony formation and IL-6 production of breast cancer cell lines. Modeling studies provided evidence for the possible interactions of the synthesized compounds with the key residues of the STAT3-SH2 domain. Collectively, our present study suggests 2-substituted-4-benzyl-5-methylimidazoles are a new class of anti-cancer drug candidates to inhibit oncogenic STAT3 function.

Targeting STAT3: A crucial modulator of sepsis

Signal transducer and activator of transcription 3 (STAT3) is a cellular signal transcription factor that has recently attracted a great deal of attention. It can trigger a variety of genes transcription in response to cytokines and growth factors stimulation, which plays an important role in many cellular biological processes involved in anti/proinflammatory responses. Sepsis is a life-threatening organ dysfunction resulting from dysregulated host responses to infection. As a converging point of multiple inflammatory responses pathways, accumulating studies have presented the elaborate network of STAT3 in sepsis pathophysiology; these results generally indicate a promising therapeutic application for targeting STAT3 in the treatment of sepsis. In the present review, we evaluated the published literature describing the use of STAT3 in the treatment of experimental and clinical sepsis. The information presented here may be useful for the design of future studies and may highlight the potential of STAT3 as a future biomarker and therapeutic target for sepsis.

15-Deoxy-Δ12,14 -prostaglandin J2 binds and inactivates STAT3 via covalent modification of cysteine 259 in H-Ras-transformed human breast epithelial cells

Signal transducer and activator of transcription 3 (STAT3) has been considered as a potential target for development of anticancer therapeutics. Here, we report a novel mechanism by which the cyclopentenone prostaglandin, 15-deoxy-Δ^12,14 -prostaglandin J₂ (15d-PGJ₂ ) functions as an allosteric inhibitor of STAT3. 15d-PGJ₂ inhibits phosphorylation, dimerization, nuclear translocation, and transcriptional activity of STAT3 in H-Ras-transformed human mammary epithelial cells (MCF10A-Ras) through the Michael addition reaction at cysteine 259 of STAT3. Comparative studies with 15d-PGJ₂ analogues reveal that both C12-C13 and C9-C10 double bonds conjugated to the carbonyl group in the cyclopentenone ring of 15d-PGJ₂ are essential for STAT3 binding. Antiproliferative and pro-apoptotic activities of 15d-PGJ₂ in MCF10A-Ras cells are attributable to covalent modification of STAT3 on Cys259, and mimic the effects induced by mutation of this amino acid.

LncRNA-encoded polypeptide ASRPS inhibits triple-negative breast cancer angiogenesis

In this study, Wang et al. demonstrate that lncRNA-encoded polypeptide ASRPS is down-regulated in TNBC. ASRPS regulates angiogenesis and may serve as a novel prognostic marker and therapeutic target for TNBC.

Triple-negative breast cancer (TNBC) is a subtype of breast cancer (BC) with the most aggressive phenotype and poor overall survival. Using bioinformatics tools, we identified LINC00908 encoding a 60–aa polypeptide and differentially expressed in TNBC tissues. We named this endogenously expressed polypeptide ASRPS (a small regulatory peptide of STAT3). ASRPS expression was down-regulated in TNBCs and associated with poor overall survival. We showed that LINC00908 was directly regulated by ERα, which was responsible for the differential down-regulation of LINC00908 in TNBCs. ASRPS directly bound to STAT3 through the coiled coil domain (CCD) and down-regulated STAT3 phosphorylation, which led to reduced expression of VEGF. In human endothelial cells, a mouse xenograft breast cancer model, and a mouse spontaneous BC model, ASRPS expression reduced angiogenesis. In a mouse xenograft breast cancer model, down-regulation of ASRPS promoted tumor growth, and ASRPS acted as an antitumor peptide. We presented strong evidence that LINC00908-encoded polypeptide ASRPS represented a TNBC-specific target for treatment.

Transcriptome response comparison between vector and non-vector aphids after feeding on virus-infected wheat plants

BACKGROUND

Plant viruses maintain intricate interactions with their vector and non-vector insects and can impact the fitness of insects. However, the details of their molecular and cellular mechanisms have not been studied well. We compared the transcriptome-level responses in vector and non-vector aphids (Schizaphis graminum and Rhopalosiphum padi, respectively) after feeding on wheat plants with viral infections (Barley Yellow Dwarf Virus (BYDV) and Wheat dwarf virus (WDV), respectively). We conducted differentially expressed gene (DEG) annotation analyses and observed DEGs related to immune pathway, growth, development, and reproduction. And we conducted cloning and bioinformatic analyses of the key DEG involved in immune.

RESULTS

For all differentially expressed gene analyses, the numbers of DEGs related to immune, growth, development, reproduction and cuticle were higher in vector aphids than in non-vector aphids. STAT5B (signal transducer and activator of transcription 5B), which is involved in the JAK-STAT pathway, was upregulated in R. padi exposed to WDV. The cloning and bioinformatic results indicated that the RpSTAT5B sequence contains a 2082 bp ORF encoding 693 amino acids. The protein molecular weight is 79.1 kD and pI is 8.13. Analysis indicated that RpSTAT5B is a non-transmembrane protein and a non-secreted protein. Homology and evolutionary analysis indicated that RpSTAT5B was closely related to R. maidis.

CONCLUSIONS

Unigene expression analysis showed that the total number of differentially expressed genes (DEGs) in the vector aphids was higher than that in the non-vector aphids. Functional enrichment analysis showed that the DEGs related to immunity, growth and reproduction in vector aphids were higher than those in non-vector aphids, and the differentially expressed genes related to immune were up-regulated. This study provides a basis for the evaluation of the response mechanisms of vector/non-vector insects to plant viruses.

STAT3, the Challenge for Chemotherapeutic and Radiotherapeutic Efficacy

Chemoradiotherapy is one of the most effective and extensively used strategies for cancer treatment. Signal transducer and activator of transcription 3 (STAT3) regulates vital biological processes, such as cell proliferation and cell growth. It is constitutively activated in various cancers and limits the application of chemoradiotherapy. Accumulating evidence suggests that STAT3 regulates resistance to chemotherapy and radiotherapy and thereby impairs therapeutic efficacy by mediating its feedback loop and several target genes. The alternative splicing product STAT3β is often identified as a dominant-negative regulator, but it enhances sensitivity to chemotherapy and offers a new and challenging approach to reverse therapeutic resistance. We focus here on exploring the role of STAT3 in resistance to receptor tyrosine kinase (RTK) inhibitors and radiotherapy, outlining the potential of targeting STAT3 to overcome chemo(radio)resistance for improving clinical outcomes, and evaluating the importance of STAT3β as a potential therapeutic approach to overcomes chemo(radio)resistance. In this review, we discuss some new insights into the effect of STAT3 and its subtype STAT3β on chemoradiotherapy sensitivity, and we explore how these insights influence clinical treatment and drug development for cancer.

Targeting Janus Kinases and Signal Transducer and Activator of Transcription 3 to Treat Inflammation, Fibrosis, and Cancer: Rationale, Progress, and Caution

Before it was molecularly cloned in 1994, acute-phase response factor or signal transducer and activator of transcription (STAT)3 was the focus of intense research into understanding the mammalian response to injury, particularly the acute-phase response. Although known to be essential for liver production of acute-phase reactant proteins, many of which augment innate immune responses, molecular cloning of acute-phase response factor or STAT3 and the research this enabled helped establish the central function of Janus kinase (JAK) family members in cytokine signaling and identified a multitude of cytokines and peptide hormones, beyond interleukin-6 and its family members, that activate JAKs and STAT3, as well as numerous new programs that their activation drives. Many, like the acute-phase response, are adaptive, whereas several are maladaptive and lead to chronic inflammation and adverse consequences, such as cachexia, fibrosis, organ dysfunction, and cancer. Molecular cloning of STAT3 also enabled the identification of other noncanonical roles for STAT3 in normal physiology, including its contribution to the function of the electron transport chain and oxidative phosphorylation, its basal and stress-related adaptive functions in mitochondria, its function as a scaffold in inflammation-enhanced platelet activation, and its contributions to endothelial permeability and calcium efflux from endoplasmic reticulum. In this review, we will summarize the molecular and cellular biology of JAK/STAT3 signaling and its functions under basal and stress conditions, which are adaptive, and then review maladaptive JAK/STAT3 signaling in animals and humans that lead to disease, as well as recent attempts to modulate them to treat these diseases. In addition, we will discuss how consideration of the noncanonical and stress-related functions of STAT3 cannot be ignored in efforts to target the canonical functions of STAT3, if the goal is to develop drugs that are not only effective but safe. SIGNIFICANCE STATEMENT: Key biological functions of Janus kinase (JAK)/signal transducer and activator of transcription (STAT)3 signaling can be delineated into two broad categories: those essential for normal cell and organ development and those activated in response to stress that are adaptive. Persistent or dysregulated JAK/STAT3 signaling, however, is maladaptive and contributes to many diseases, including diseases characterized by chronic inflammation and fibrosis, and cancer. A comprehensive understanding of JAK/STAT3 signaling in normal development, and in adaptive and maladaptive responses to stress, is essential for the continued development of safe and effective therapies that target this signaling pathway.

Role of JAK/STAT3 Signaling in the Regulation of Metastasis, the Transition of Cancer Stem Cells, and Chemoresistance of Cancer by Epithelial-Mesenchymal Transition

The JAK/STAT3 signaling pathway plays an essential role in various types of cancers. Activation of this pathway leads to increased tumorigenic and metastatic ability, the transition of cancer stem cells (CSCs), and chemoresistance in cancer via enhancing the epithelial–mesenchymal transition (EMT). EMT acts as a critical regulator in the progression of cancer and is involved in regulating invasion, spread, and survival. Furthermore, accumulating evidence indicates the failure of conventional therapies due to the acquisition of CSC properties. In this review, we summarize the effects of JAK/STAT3 activation on EMT and the generation of CSCs. Moreover, we discuss cutting-edge data on the link between EMT and CSCs in the tumor microenvironment that involves a previously unknown function of miRNAs, and also discuss new regulators of the JAK/STAT3 signaling pathway.

Stafia-1: a STAT5a-Selective Inhibitor Developed via Docking-Based Screening of in Silico O-Phosphorylated Fragments

We present a new approach for the identification of inhibitors of phosphorylation-dependent protein-protein interaction domains, in which phenolic fragments are adapted by in silico O-phosphorylation before docking-based screening. From a database of 10 369 180 compounds, we identified 85 021 natural product-derived phenolic fragments, which were virtually O-phosphorylated and screened for in silico binding to the STAT3 SH2 domain. Nine screening hits were then synthesized, eight of which showed a degree of in vitro inhibition of STAT3. After analysis of its selectivity profile, the most potent inhibitor was then developed to Stafia-1, the first small molecule shown to preferentially inhibit the STAT family member STAT5a over the close homologue STAT5b. A phosphonate prodrug based on Stafia-1 inhibited STAT5a with selectivity over STAT5b in human leukemia cells, providing the first demonstration of selective in vitro and intracellular inhibition of STAT5a by a small-molecule inhibitor.

Distinct molecular response patterns of activating STAT3 mutations associate with penetrance of lymphoproliferation and autoimmunity

Germline STAT3 gain-of-function (GOF) mutations have been linked to poly-autoimmunity and lymphoproliferation with variable expressivity and incomplete penetrance. Here we studied the impact of 17 different STAT3 GOF mutations on the canonical STAT3 signaling pathway and correlated the molecular results with clinical manifestations. The mutations clustered in three groups. Group 1 mutants showed altered STAT3 phosphorylation kinetics and strong basal transcriptional activity. They were associated with the highest penetrance of lymphoproliferation and autoimmunity. Group 2 mutants showed a strongly inducible transcriptional reporter activity and were clinically less penetrant. Group 3 mutants were mostly located in the DNA binding domain and showed the strongest DNA binding affinity despite a poor transcriptional reporter response. Thus, the GOF effect of STAT3 mutations is determined by a heterogeneous response pattern at the molecular level. The correlation of response pattern and clinical penetrance indicates a significant contribution of mutation-determined effects on disease manifestations.

Imatinib modulates pro-inflammatory microenvironment with angiostatic effects in experimental lung carcinogenesis

Lung cancer has second highest rate of incidence and mortality around the world. Smoking cigarettes is the main stream cause of lung carcinogenesis along with other factors such as spontaneous mutations, inactivation of tumor suppressor genes. The present study was aimed to identify the mechanistic role of Imatinib in the chemoprevention of experimental lung carcinogenesis in rat model. Gross morphological observations for tumor formation, histological examinations, RT-PCR, Western blotting, fluorescence spectroscopy and molecular docking studies were performed to elucidate the chemopreventive effects of Imatinib and support our hypothesis by various experiments. It is evident that immuno-compromised microenvironment inside solid tumors is responsible for tumor progression and drug resistance. Therefore, it is inevitable to modulate the pro-inflammatory signaling inside solid tumors to restrict neoangiogenesis. In the present study, we observed that Imatinib could downregulate the inflammatory signaling and also attributed angiostatic effects. Moreover, Imatinib also altered the biophysical properties of BAL cells such as plasma membrane potential, fluidity and microviscosity to restrict their infiltration and thereby accumulation to mount immuno-compromised environment inside the solid tumors during angiogenesis. Our molecular docking studies suggest that immunomodulatory and angiostatic properties of Imatinib could be either independent of each other or just a case of synergistic pleiotropy. Imatinib was observed to activate the intrinsic or mitochondrial pathway of apoptosis to achieve desired effects in cancer cell killings. Interestingly, binding of Imatinib inside the catalytic domain of PARP-1 also suggests that it has caspase-independent properties in promoting cancer cell deaths.

Balancing STAT Activity as a Therapeutic Strategy

Driven by dysregulated IL-6 family member cytokine signaling in the tumor microenvironment (TME), aberrant signal transducer and activator of transcription (STAT3) and (STAT5) activation have been identified as key contributors to tumorigenesis. Following transformation, persistent STAT3 activation drives the emergence of mesenchymal/cancer-stem cell (CSC) properties, important determinants of metastatic potential and therapy failure. Moreover, STAT3 signaling within tumor-associated macrophages and neutrophils drives secretion of factors that facilitate metastasis and suppress immune cell function. Persistent STAT5 activation is responsible for cancer cell maintenance through suppression of apoptosis and tumor suppressor signaling. Furthermore, STAT5-mediated CD4+/CD25+ regulatory T cells (T_regs) have been implicated in suppression of immunosurveillance. We discuss these roles for STAT3 and STAT5, and weigh the attractiveness of different modes of targeting each cancer therapy. Moreover, we discuss how anti-tumorigenic STATs, including STAT1 and STAT2, may be leveraged to suppress the pro-tumorigenic functions of STAT3/STAT5 signaling.

AlloFinder: a strategy for allosteric modulator discovery and allosterome analyses

Allostery tweaks innumerable biological processes and plays a fundamental role in human disease and drug discovery. Exploration of allostery has thus been regarded as a crucial requirement for research on biological mechanisms and the development of novel therapeutics. Here, based on our previously developed allosteric data and methods, we present an interactive platform called AlloFinder that identifies potential endogenous or exogenous allosteric modulators and their involvement in human allosterome. AlloFinder automatically amalgamates allosteric site identification, allosteric screening and allosteric scoring evaluation of modulator-protein complexes to identify allosteric modulators, followed by allosterome mapping analyses of predicted allosteric sites and modulators in human proteome. This web server exhibits prominent performance in the reemergence of allosteric metabolites and exogenous allosteric modulators in known allosteric proteins. Specifically, AlloFinder enables identification of allosteric metabolites for metabolic enzymes and screening of potential allosteric compounds for disease-related targets. Significantly, the feasibility of AlloFinder to discover allosteric modulators was tested in a real case of signal transduction and activation of transcription 3 (STAT3) and validated by mutagenesis and functional experiments. Collectively, AlloFinder is expected to contribute to exploration of the mechanisms of allosteric regulation between metabolites and metabolic enzymes, and to accelerate allosteric drug discovery. The AlloFinder web server is freely available to all users at http://mdl.shsmu.edu.cn/ALF/.

The STAT5b Linker Domain Mediates the Selectivity of Catechol Bisphosphates for STAT5b over STAT5a

STAT family proteins are important mediators of cell signaling and represent therapeutic targets for the treatment of human diseases. Most STAT inhibitors target the protein-protein interaction domain, the SH2 domain, but specificity for a single STAT protein is often limited. Recently, we developed catechol bisphosphates as the first inhibitors of STAT5b demonstrated to exhibit a high degree of selectivity over the close homologue STAT5a. Here, we show that the amino acid in position 566 of the linker domain, not the SH2 domain, is the main determinant of specificity. Arg566 in wild-type STAT5b favors tight binding of catechol bisphosphates, while Trp566 in wild-type STAT5a does not. Amino acid 566 also determines the affinity for a tyrosine-phosphorylated peptide derived from the EPO receptor for STAT5a and STAT5b, demonstrating the functional relevance of the STAT5 linker domain for the adjacent SH2 domain. These results provide the first demonstration that a residue in the linker domain can determine the affinity of nonpeptidic small-molecule inhibitors for the SH2 domain of STAT proteins. We propose targeting the interface between the SH2 domain and linker domain as a novel design approach for the development of potent and selective STAT inhibitors. In addition, our data suggest that the linker domain could contribute to the enigmatically divergent biological functions of the two STAT5 proteins.