Inhibition of the Signal Transducer and Activator of Transcription-3 (STAT3) Signaling Pathway by 4-Oxo-1-Phenyl-1,4-Dihydroquinoline-3-Carboxylic Acid Esters

New supramolecules of bis(acylhydrazones)-linked bisphenol sulfide for Alzheimer's: targeting cholinesterases by in vitro and in silico approaches

In current research, two functional components, i.e., hydrazone and bisphenol sulfide were combined to get useful supramolecules in medicinal chemistry. Herein 25 new 4,4'-thiodiphenol bis-acylhydrazones were synthesized in good to excellent yields. Initially ethyl-2-chloroacetate was reacted with 4,4'-thiodiphenol, which was further reacted with excess hydrazine hydrate to produce 2,2'-((thiobis(4,1-phenylene))bis(oxy))di(acetohydrazide), which was then combined with various aromatic and aliphatic aldehydes to get the desired products (hydrazones, 4a-4y). The synthesized supramolecules were characterized by contemporary spectroscopic techniques such as 1H NMR, 13C NMR, and mass spectroscopy. The synthetic compound's cholinesterase blocking activity was tested against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes where compounds 4n, and 4h showed excellent inhibitory potential for AChE, while 4b, and 4h, demonstrated most potent inhibition of BChE. The starting compound (SM3) and compounds 4h and SM3 depicted excellent dual inhibitory capabilities for both enzymes. The chemical basis of anticholinesterase activity was investigated using a structure-based molecular docking approach. The biological significance and the ease of synthesis of this class of compounds should be considered in therapeutic development for Alzheimer's disease treatments.

A new synthetic derivative of cryptotanshinone KYZ3 as STAT3 inhibitor for triple-negative breast cancer therapy

Silencing STAT3 is confirmed as a promising therapeutic strategy for triple-negative breast cancer (TNBC) therapy to address the issue of its poor prognosis. In this study, the natural product cryptotanshinone was firstly remodeled and modified as a more effective STAT3 inhibitor by structure-based strategy. The synthetic derivative KYZ3 had 22-24-fold increase in antitumor activity than cryptotanshinone on two TNBC cell lines but had little effect on normal breast epithelial MCF-10A cells. Further investigation showed that KYZ3 inhibited persistent STAT3 phosphorylation. It also prevented the STAT3 protein nuclear translocation to regulate the expressions of the target oncogenes including Bax and Bcl-2. Furthermore, KYZ3 inhibited TNBC cell metastasis by decreasing the levels of MMP-9 which were directly regulated by activated STAT3. A STAT3 plasmid transfecting assay suggested that KYZ3 induced tumor cell apoptosis mainly by targeting STAT3. Finally, KYZ3 suppressed the growth of tumors resulting from subcutaneous implantation of MDA-MB-231 cells in vivo. Taken together, KYZ3 may be a promising cancer therapeutic agent for TNBC.

CD24 Expression and differential resistance to chemotherapy in triple-negative breast cancer

Breast cancer (BC) is a leading cause of cancer-related death in women. Adjuvant systemic chemotherapies are effective in reducing risks of recurrence and have contributed to reduced BC mortality. Although targeted adjuvant treatments determined by biomarkers for endocrine and HER2-directed therapies are largely successful, predicting clinical benefit from chemotherapy is more challenging. Drug resistance is a major reason for treatment failures. Efforts are ongoing to find biomarkers to select patients most likely to benefit from chemotherapy. Importantly, cell surface biomarkers CD44+/CD24- are linked to drug resistance in some reports, yet underlying mechanisms are largely unknown. This study focused on the potential role of CD24 expression in resistance to either docetaxel or doxorubicin in part by the use of triple-negative BC (TNBC) tissue microarrays. In vitro assays were also done to assess changes in CD24 expression and differential drug susceptibility after chemotherapy. Further, mouse tumor xenograft studies were done to confirm in vitro findings. Overall, the results show that patients with CD24-positive TNBC had significantly worse overall survival and disease-free survival after taxane-based treatment. Also, in vitro cell studies show that CD44+/CD24+/high cells are more resistant to docetaxel, while CD44+/CD24-/low cells are resistant to doxorubicin. Both in vitro and in vivo studies show that cells with CD24-knockdown are more sensitive to docetaxel, while CD24-overexpressing cells are more sensitive to doxorubicin. Further, mechanistic studies indicate that Bcl-2 and TGF-βR1 signaling via ATM-NDRG2 pathways regulate CD24. Hence, CD24 may be a biomarker to select chemotherapeutics and a target to overcome TNBC drug resistance.

Chemotherapy-Induced Ca2+ Release Stimulates Breast Cancer Stem Cell Enrichment

Breast cancer stem cells (BCSCs) play a critical role in tumor recurrence and metastasis. Exposure of breast cancer cells to chemotherapy leads to an enrichment of BCSCs. Here, we find that chemotherapy induces the expression of glutathione S-transferase omega 1 (GSTO1), which is dependent on hypoxia-inducible factor 1 (HIF-1) and HIF-2. Knockdown of GSTO1 expression abrogates carboplatin-induced BCSC enrichment, decreases tumor initiation and metastatic capacity, and delays tumor recurrence after chemotherapy. GSTO1 interacts with the ryanodine receptor RYR1 and promotes calcium release from the endoplasmic reticulum. Increased cytosolic calcium levels activate PYK2 → SRC → STAT3 signaling, leading to increased expression of pluripotency factors and BCSC enrichment. HIF inhibition blocks chemotherapy-induced GSTO1 expression and BCSC enrichment. Combining HIF inhibitors with chemotherapy may improve clinical outcome in breast cancer.

Mechanosensor polycystin-1 potentiates differentiation of human osteoblastic cells by upregulating Runx2 expression via induction of JAK2/STAT3 signaling axis

Polycystin-1 (PC1) has been proposed as a chief mechanosensing molecule implicated in skeletogenesis and bone remodeling. Mechanotransduction via PC1 involves proteolytic cleavage of its cytoplasmic tail (CT) and interaction with intracellular pathways and transcription factors to regulate cell function. Here we demonstrate the interaction of PC1-CT with JAK2/STAT3 signaling axis in mechanically stimulated human osteoblastic cells, leading to transcriptional induction of Runx2 gene, a master regulator of osteoblastic differentiation. Primary osteoblast-like PC1-expressing cells subjected to mechanical-stretching exhibited a PC1-dependent increase of the phosphorylated(p)/active form of JAK2. Specific interaction of PC1-CT with pJAK2 was observed after stretching while pre-treatment of cells with PC1 (anti-IgPKD1) and JAK2 inhibitors abolished JAK2 activation. Consistently, mechanostimulation triggered PC1-mediated phosphorylation and nuclear translocation of STAT3. The nuclear phosphorylated(p)/DNA-binding competent pSTAT3 levels were augmented after stretching followed by elevated DNA-binding activity. Pre-treatment with a STAT3 inhibitor either alone or in combination with anti-IgPKD1 abrogated this effect. Moreover, PC1-mediated mechanostimulation induced elevation of Runx2 mRNA levels. ChIP assays revealed direct regulation of Runx2 promoter activity by STAT3/Runx2 after mechanical-stretching that was PC1-dependent. Our findings show that mechanical load upregulates expression of Runx2 gene via potentiation of PC1-JAK2/STAT3 signaling axis, culminating to possibly control osteoblastic differentiation and ultimately bone formation.

Autocrine IL-10 activation of the STAT3 pathway is required for pathological macrophage differentiation in polycystic kidney disease

Polycystic kidney disease (PKD) is characterized by slow expansion of fluid-filled cysts derived from tubules within the kidney. Cystic expansion results in injury to surrounding parenchyma and leads to inflammation, scarring and ultimately loss of renal function. Macrophages are a key element in this process, promoting cyst epithelial cell proliferation, cyst expansion and disease progression. Previously, we have shown that the microenvironment established by cystic epithelial cells can ‘program’ macrophages, inducing M2-like macrophage polarization that is characterized by expression of markers that include Arg1 and Il10. Here, we functionally characterize these macrophages, demonstrating that their differentiation enhances their ability to promote cyst cell proliferation. This observation indicates a model of reciprocal pathological interactions between cysts and the innate immune system: cyst epithelial cells promote macrophage polarization to a phenotype that, in turn, is especially efficient in promoting cyst cell proliferation and cyst growth. To better understand the genesis of this macrophage phenotype, we examined the role of IL-10, a regulatory cytokine shown to be important for macrophage-stimulated tissue repair in other settings. Herein, we show that the acquisition of the pathological macrophage phenotype requires IL-10 secretion by the macrophages. Further, we demonstrate a requirement for IL-10-dependent autocrine activation of the STAT3 pathway. These data suggest that the IL-10 pathway in macrophages plays an essential role in the pathological relationship between cysts and the innate immune system in PKD, and thus could be a potential therapeutic target.

Summary: Macrophages in polycystic kidney disease are induced by cyst epithelial cell factors to perform pathological pro-proliferative functions through stimulation of an autocrine IL-10–STAT3 pathway.

Tumour cell population growth inhibition and cell death induction of functionalized 6-aminoquinolone derivatives

OBJECTIVES

A number of previous studies has provided evidence that the well-known anti-bacterial quinolones may have potential as anti-cancer drugs. The aim of this study was to evaluate potential anti-tumour activity and selectivity of a set of 6-aminoquinolones showing some chemical similarity to naphthyridone derivative CX-5461, recently described as innovative anti-cancer agent.

MATERIALS AND METHODS

In-house quinolones 1-8 and ad hoc synthesized derivatives 9-13 were tested on Michigan Cancer Foundation-7 (MCF-7) breast cancer cells and mesenchymal progenitor (MePR2B) cell lines, analysing their effects on the cell cycle and cell death using FACS methodology. Activation of p53 was evaluated by western blotting.

RESULTS

Benzyl esters 4, 5 and their amide counterparts 12, 13 drastically modulated MCF-7 cell cycles inducing DNA fragmentation and cell death, thus proving to be potential anti-tumour compounds. When assayed in non-tumour MePR2B cells, compounds 4 and 5 were cytotoxic while 12 and 13 had a certain degree of selectivity, with compound 12 emerging as the most promising. Western blot analysis revealed that severe p53-K382ac activation was promoted by benzylester 5. In contrast, amide 12 exerted only a moderate effect which was, however, comparable to that of suberoylanilide hydoxamic acid (SAHA).

CONCLUSIONS

Taken together, these results further reinforce evidence that quinolones have potential as anti-cancer agents. Future work will be focused on understanding compound 12 mechanisms of action, and to obtain more potent and selective compounds.

Novel aminotetrazole derivatives as selective STAT3 non-peptide inhibitors

The development of inhibitors blocking STAT3 transcriptional activity is a promising therapeutic approach against cancer and inflammatory diseases. In this context, the selectivity of inhibitors against the STAT1 transcription factor is crucial as STAT3 and STAT1 play opposite roles in the apoptosis of tumor cells and polarization of the immune response. A structure-based virtual screening followed by a luciferase-containing promoter assay on STAT3 and STAT1 signaling were used to identify a selective STAT3 inhibitor. An important role of the aminotetrazole group in modulating STAT3 and STAT1 inhibitory activities has been established. Optimization of the hit compound leads to 23. This compound inhibits growth and survival of cells with STAT3 signaling pathway while displaying a minimal effect on STAT1 signaling. Moreover, it prevents lymphocyte T polarization into Th17 and Treg without affecting their differentiation into Th1 lymphocyte.

Pyruvate kinase M2 regulates gene transcription by acting as a protein kinase

Pyruvate kinase isoform M2 (PKM2) is a glycolysis enzyme catalyzing conversion of phosphoenolpyruvate (PEP) to pyruvate by transferring a phosphate from PEP to ADP. We report here that PKM2 localizes to the cell nucleus. The levels of nuclear PKM2 correlate with cell proliferation. PKM2 activates transcription of MEK5 by phosphorylating stat3 at Y705. In vitro phosphorylation assays show that PKM2 is a protein kinase using PEP as a phosphate donor. ADP competes with the protein substrate binding, indicating that the substrate may bind to the ADP site of PKM2. Our experiments suggest that PKM2 dimer is an active protein kinase, while the tetramer is an active pyruvate kinase. Expression of a PKM2 mutant that exists as a dimer promotes cell proliferation, indicating that protein kinase activity of PKM2 plays a role in promoting cell proliferation. Our study reveals an important link between metabolism alteration and gene expression during tumor transformation and progression.

IL-27 enhances LPS-induced proinflammatory cytokine production via upregulation of TLR4 expression and signaling in human monocytes

IL-27, which is produced by activated APCs, bridges innate and adaptive immunity by regulating the development of Th cells. Recent evidence supports a role for IL-27 in the activation of monocytic cells in terms of inflammatory responses. Indeed, proinflammatory and anti-inflammatory activities are attributed to IL-27, and IL-27 production itself is modulated by inflammatory agents such as LPS. IL-27 primes LPS responses in monocytes; however, the molecular mechanism behind this phenomenon is not understood. In this study, we demonstrate that IL-27 priming results in enhanced LPS-induced IL-6, TNF-α, MIP-1α, and MIP-1β expression in human primary monocytes. To elucidate the molecular mechanisms responsible for IL-27 priming, we measured levels of CD14 and TLR4 required for LPS binding. We determined that IL-27 upregulates TLR4 in a STAT3- and NF-κB-dependent manner. Immunofluorescence microscopy revealed enhanced membrane expression of TLR4 and more distinct colocalization of CD14 and TLR4 upon IL-27 priming. Furthermore, IL-27 priming enhanced LPS-induced activation of NF-κB family members. To our knowledge, this study is the first to show a role for IL-27 in regulating TLR4 expression and function. This work is significant as it reveals new mechanisms by which IL-27 can enhance proinflammatory responses that can occur during bacterial infections.

Fragment-based drug design and drug repositioning using multiple ligand simultaneous docking (MLSD): identifying celecoxib and template compounds as novel inhibitors of signal transducer and activator of transcription 3 (STAT3)

We describe a novel method of drug discovery using MLSD and drug repositioning, with cancer target STAT3 being used as a test case. Multiple drug scaffolds were simultaneously docked into hot spots of STAT3 by MLSD, followed by tethering to generate virtual template compounds. Similarity search of virtual hits on drug database identified celecoxib as a novel inhibitor of STAT3. Furthermore, we designed two novel lead inhibitors based on one of the lead templates and celecoxib.

Identification of Niclosamide as a New Small-Molecule Inhibitor of the STAT3 Signaling Pathway

Inhibition of the signal transducer and activator of transcription 3 (STAT3) signaling pathway has been considered a novel therapeutic strategy to treat human cancers with constitutively active STAT3. In this study, we report the identification of niclosamide, an FDA-approved anthelmintic drug, as a new small-molecule inhibitor of the STAT3 signaling pathway. This compound potently inhibited the activation and transcriptional function of STAT3 and consequently induced cell growth inhibition, apoptosis, and cell cycle arrest of cancer cells with constitutively active STAT3. Our study provides a new promising lead compound with a salicylic amide scaffold for the development of STAT3 pathway inhibitors as novel molecularly targeted anticancer drugs.

Interleukin-23-induced interleukin-23 receptor subunit expression is mediated by the Janus kinase/signal transducer and activation of transcription pathway in human CD4 T cells

Interleukin (IL)-23 plays a critical role in the development of the T helper (Th) cell response and is responsible for the maintenance of the IL-17 producing subset of Th cells, Th17. IL-23 is a heterodimeric cytokine composed of IL-23p19 and IL-12p40 subunits, and the signaling pathway for IL-23 involves 2 receptor chains: IL-12Rβ1 and IL-23Rα. The IL-23 receptor complex is expressed on a number of cells, including natural killer cells, monocytes, macrophages, dendritic cells, and CD4 T cells. Currently, the molecular mechanisms governing expression of the IL-23 receptor chains, IL-23Rα and IL-12Rβ1, are not well understood. Our results show that IL-23 induces upregulation of IL-23Rα and IL-12Rβ1 expression in human CD4 T cells. Further, we demonstrate that inhibition of the Janus kinase/signal transducer and activation of transcription (JAK/STAT) pathway by SD-1029, a JAK2 inhibitor, 5'-deoxy-5'-(methylthio) adenosine, a STAT1 inhibitor, and STAT3 VII, a STAT3 inhibitor, were able to block IL-23-induced expression of IL-23 receptor subunits in the human SUPT-1 T cell line and in primary CD4 human T cells. Taken together, our results suggest a positive feedback regulation of the IL-23 receptor via IL-23-mediated activation of the JAK/STAT pathway.

Identification of a New Series of STAT3 Inhibitors by Virtual Screening

The signal transducer and activator of transcription 3 (STAT3) is considered to be an attractive therapeutic target for oncology drug development. We identified a N-[2-(1,3,4-oxadiazolyl)]-4-quinolinecarboxamide derivative, STX-0119, as a novel STAT3 dimerization inhibitor by a virtual screen using a customized version of the DOCK4 program with the crystal structure of STAT3. In addition, we used in vitro cell-based assays such as the luciferase reporter gene assay and the fluorescence resonance energy transfer-based STAT3 dimerization assay. STX-0119 selectively abrogated the DNA binding activity of STAT3 and suppressed the expression of STAT3-regulated oncoproteins such as c-myc and survivin in cancer cells. In contrast, a truncated inactive analogue, STX-0872, did not exhibit those activities. Oral administration of STX-0119 effectively abrogated the growth of human lymphoma cells in a SCC-3 subcutaneous xenograft model without visible toxicity. Structure-activity relationships of STX-0119 derivatives were investigated using the docking model of the STAT3-SH2 domain/STX-0119.

STAT3 inhibitors attenuate interferon-γ-induced neurotoxicity and inflammatory molecule production by human astrocytes

Activation of signal transducer and activator of transcription (STAT) 3 is observable in reactive astrocytes under certain neuropathological conditions. Interferon (IFN)-γ is shown to activate STAT3 in cultured rodent astrocytes. Here we investigated the effects of inhibiting STAT3 signaling on IFNγ-activated human astrocytes since we have recently demonstrated that human astrocytes become neurotoxic when stimulated by IFNγ. We found that 5'-deoxy-5'-(methylthio)adenosine (MTA) (300 μM), S3I-201 (10 μM), STAT3 inhibitor VII (3 μM) and JAK-inhibitor I (0.3 μM) had anti-neurotoxic effects on IFN-γ (50 U/ml)-activated astrocytes and U373-MG astrocytoma cells. Another inhibitor, AG490 (30 μM) had no significant effect. The active inhibitors also attenuated IFN-γ-induced phosphorylation of Tyr(705)-STAT3 and astrocytic expression of intercellular adhesion molecule-1 (ICAM-1). They also decreased astrocytic production of IFN-γ-inducible T cell α chemoattractant (I-TAC). AG490, which did not affect the Tyr(705)-STAT3 phosphorylation or ICAM-1 expression, nevertheless reduced the I-TAC secretion. Because these results indicate that pharmacological inhibition of STAT3 signaling correlates with reduced astrocytic neurotoxicity and ICAM-1 expression, but not that of I-TAC secretion, we consider that STAT3 activation mediates, at least in part, the IFN-γ-induced neurotoxicity and ICAM-1 expression by human astrocytes.

Molecular disruption of oncogenic signal transducer and activator of transcription 3 (STAT3) protein

Signal transducer and activator of transcription protein 3 (STAT3) is a latent cytosolic transcription factor that is widely recognized as being a master regulator of the cellular functions that lead to the cancer phenotype. Constitutively activated STAT3 protein activity is routinely observed in human cancers, promoting uncontrolled cell proliferation and suppressing apoptosis. Until relatively recently, inhibition of STAT3 transcriptional activity was achieved indirectly via suppression of upstream kinase activators and extracellular cytokine and (or) growth factor stimuli. However, activated STAT3 forms transcriptionally functional STAT3-STAT3 dimers, providing a valid juncture for targeted downstream molecular inhibition. STAT3's prominent role in cancer has seen a decade of innovative and novel approaches to targeting constitutively active STAT3 protein-protein complexes. This mini-review outlines the progress made towards identifying molecular agents capable of silencing aberrant STAT3 signalling through the disruption of STAT3 complexation events.

The neurosurvival factor Humanin inhibits beta-cell apoptosis via signal transducer and activator of transcription 3 activation and delays and ameliorates diabetes in nonobese diabetic mice

Pancreatic beta-cell apoptosis is important in the pathogenesis and potential treatment of type 1 diabetes mellitus. We investigated whether Humanin, a recently described survival factor for neurons, could improve the survival of beta-cells and delay or treat diabetes in the nonobese diabetic (NOD) model. Humanin reduced apoptosis induced by serum starvation in NIT-1 cells and decreased apoptosis induced by cytokine treatment. Humanin induced signal transducer and activator of transcription 3 and extracellular signal-regulated kinase phosphorylation over a 24-hour time course. Specific inhibition of signal transducer and activator of transcription 3 resulted in nullifying the protective effect of Humanin. Humanin normalized glucose tolerance in NOD mice treated for 6 weeks, and their pancreata revealed decreased lymphocyte infiltration and severity. In addition, Humanin delayed/prevented the onset of diabetes in NOD mice treated for 20 weeks. In summary, Humanin treatment decreases cytokine-induced apoptosis in beta-cells in vitro and improved glucose tolerance and onset of diabetes in NOD mice in vivo. This indicates that Humanin may be useful for islet protection and survival in a spectrum of diabetes-related therapeutics.