Selective chemical probe inhibitor of Stat3, identified through structure-based virtual screening, induces antitumor activity

Multi-Level High-Throughput Screening for Discovery of Ligands That Inhibit Insulin Aggregation

We have developed a multi-level virtual screening protocol to identify lead molecules from the FDA inactives database that can inhibit insulin aggregation. The method is based on the presence of structural and interaction specificity in non-native aggregation pathway protein-protein interactions. Some key challenges specific to the present problem, when compared with native protein association, include structural heterogeneity of the protein species involved, multiple association pathways, and relatively higher probability of conformational rearrangement of the association complex. In this multi-step method, the inactives database was first screened using the dominant pharmacophore features of previously identified molecules shown to significantly inhibit insulin aggregation nucleation by binding to its aggregation-prone conformers. We then performed ensemble docking of several low-energy ligand conformations on these aggregation-prone conformers followed by molecular dynamics simulations and binding affinity calculations on a subset of docked complexes to identify a final set of five potential lead molecules to inhibit insulin aggregation nucleation. Their effect on aggregation inhibition was extensively investigated by incubating insulin under aggregation-prone aqueous buffer conditions (low pH, high temperature). Aggregation kinetics were characterized using size exclusion chromatography and Thioflavin T fluorescence assay, and the secondary structure was determined using circular dichroism spectroscopy. Riboflavin provided the best aggregation inhibition, with 85% native monomer retention after 48 h incubation under aggregation-prone conditions, whereas the no-ligand formulation showed complete monomer loss after 36 h. Further, insulin incubated with two of the screened inactives (aspartame, riboflavin) had the characteristic α-helical dip in CD spectra, while the no-ligand formulation showed a change to β-sheet rich conformations.

Induction of Apoptosis and Effect on the FAK/AKT/mTOR Signal Pathway by Evodiamine in Gastric Cancer Cells

Evodiamine isolated from Evodia rutaecarpa has been known to have anti-tumor activity against various cancer cell types. Although there have been reports showing the inhibitory effect of evodiamine on cell survival of gastric cancer cell, it is not clearly explained how evodiamine affects the expression and modification of proteins associated with apoptosis and upstream signal pathways. We confirmed the cytotoxic activity of evodiamine against AGS and MKN45 cells by a WST assay, cell morphological change, and clonogenic assay. The apoptotic cells were evaluated by Annexin V/PI analysis and Western blot and the expressions of apoptosis-related molecules were confirmed by Western blot. Evodiamine promoted apoptosis of AGS gastric cancer cells through both intrinsic and extrinsic signal pathways in a time- and dose-dependent manner. Evodiamine attenuated the expression of anti-apoptotic proteins, including Bcl-2, XIAP, and survivin, and elevated that of the pro-apoptotic protein Bax. Evodiamine also suppressed the FAK/AKT/mTOR signal pathway. Based on these results, we expect that the results from this study will further elucidate our understanding of evodiamine as an anti-cancer drug.

Ang II (Angiotensin II)-Induced FGFR1 (Fibroblast Growth Factor Receptor 1) Activation in Tubular Epithelial Cells Promotes Hypertensive Kidney Fibrosis and Injury

BACKGROUND

Elevated Ang II (angiotensin II) level leads to a range of conditions, including hypertensive kidney disease. Recent evidences indicate that FGFR1 (fibroblast growth factor receptor 1) signaling may be involved in kidney injuries. In this study, we determined whether Ang II alters FGFR1 signaling to mediate renal dysfunction.

METHODS

Human archival kidney samples from patients with or without hypertension were examined. Multiple genetic and pharmacological approaches were used to investigate FGFR1-mediated signaling in tubular epithelial NRK-52E cells in response to Ang II stimulation. C57BL/6 mice were infused with Ang II for 28 days to develop hypertensive kidney disease. Mice were treated with either adeno-associated virus expressing FGFR1 shRNA or FGFR1 inhibitor AZD4547.

RESULTS

Kidney specimens from subjects with hypertension and mice challenged with Ang II have increased FGFR1 activity in renal epithelial cells. Renal epithelial cells in culture initiate extracellular matrix programming in response to Ang II, through the activation of FGFR1, which is independent of both AT1R (angiotensin II receptor type 1) and AT2R (angiotensin II receptor type 2). The RNA sequencing analysis indicated that disrupting FGFR1 suppresses Ang II-induced fibrogenic responses in epithelial cells. Mechanistically, Ang II-activated FGFR1 leads to STAT3 (signal transducer and activator of transcription 3) activation, which is responsible for fibrogenic factor expression in kidneys. In the mouse model of hypertensive kidney disease, genetic knockdown of FGFR1 or pharmacological inhibition of its activity protected kidneys from dysfunction and fibrosis upon Ang II challenge.

CONCLUSIONS

Our studies uncover a novel mechanism causing renal fibrosis in hypertension and indicate FGFR1 as a potential target to preserve renal function and integrity.

SHF Acts as a Novel Tumor Suppressor in Glioblastoma Multiforme by Disrupting STAT3 Dimerization

Sustained activation of signal transducer and activator of transcription 3 (STAT3) is a critical contributor in tumorigenesis and chemoresistance, thus making it an attractive cancer therapeutic target. Here, SH2 domain-containing adapter protein F (SHF) is identified as a tumor suppressor in glioblastoma Multiforme (GBM) and its negative regulation of STAT3 activity is characterized. Mechanically, SHF selectively binds and inhibits acetylated STAT3 dimerization without affecting STAT3 phosphorylation or acetylation. Additionally, by blocking STAT3-DNMT1 (DNA Methyltransferase 1) interaction, SHF relieves methylation of tumor suppressor genes. The SH2 domain is documented to be essential for SHF's actions on STAT3, and almost entirely replaces the functions of SHF on STAT3 independently. Moreover, the peptide C16 a peptide derived from the STAT3-binding sites of SHF inhibits STAT3 dimerization and STAT3/DNMT1 interaction, and achieves remarkable growth inhibition in GBM cells in vitro and in vivo. These findings strongly identify targeting of the SHF/STAT3 interaction as a promising strategy for developing an optimal STAT3 inhibitor and provide early evidence of the potential clinical efficacy of STAT3 inhibitors such as C16 in GBM.

Effects of STAT3 Inhibitor BP-1-102 on The Proliferation, Invasiveness, Apoptosis and Neurosphere Formation of Glioma Cells in Vitro

Malignant glioma, especially glioblastoma (GBM), has historically been associated with a low survival rate. The hyperactivation of STAT3 played a key role in GBM initiation and resistance to therapy; thus, there is an urgent requirement for novel STAT3 inhibitors. BP-1-102 was recently reported as a biochemical inhibitor of STAT3, but its roles and mechanism in biological behavior of glioma cells were still unclear. In this study, the effects of BP-1-102 on proliferation, apoptosis, invasion and neurosphere formation of glioma cell were investigated. Our results indicated that BP-1-102 inhibited the proliferation of U251 and A172 cells, and their IC50 values were 10.51 and 8.534 μM, respectively. Furthermore, BP-1-102 inhibited the invasion and migration abilities of U251 and A172 cells by decreasing the expression of matrix metallopeptidase 9, and induced glioma cell apoptosis by decreasing the expression of B-cell lymphoma-2. BP-1-102 also inhibited the formation of neurosphere. Mechanically, BP-1-102 reduced the phosphorylation of STAT3 and the p-STAT3's nuclear translocation in glioma cells. Thus, this study herein provided a potential drug for glioma therapy.

Central Roles of STAT3-Mediated Signals in Onset and Development of Cancers: Tumorigenesis and Immunosurveillance

Since the time of Rudolf Virchow in the 19th century, it has been well-known that cancer-associated inflammation contributes to tumor initiation and progression. However, it remains unclear whether a collapse of the balance between the antitumor immune response via the immunological surveillance system and protumor immunity due to cancer-related inflammation is responsible for cancer malignancy. The majority of inflammatory signals affect tumorigenesis by activating signal transducer and activation of transcription 3 (STAT3) and nuclear factor-κB. Persistent STAT3 activation in malignant cancer cells mediates extremely widespread functions, including cell growth, survival, angiogenesis, and invasion and contributes to an increase in inflammation-associated tumorigenesis. In addition, intracellular STAT3 activation in immune cells causes suppressive effects on antitumor immunity and leads to the differentiation and mobilization of immature myeloid-derived cells and tumor-associated macrophages. In many cancer types, STAT3 does not directly rely on its activation by oncogenic mutations but has important oncogenic and malignant transformation-associated functions in both cancer and stromal cells in the tumor microenvironment (TME). We have reported a series of studies aiming towards understanding the molecular mechanisms underlying the proliferation of various types of tumors involving signal-transducing adaptor protein-2 as an adaptor molecule that modulates STAT3 activity, and we recently found that AT-rich interactive domain-containing protein 5a functions as an mRNA stabilizer that orchestrates an immunosuppressive TME in malignant mesenchymal tumors. In this review, we summarize recent advances in our understanding of the functional role of STAT3 in tumor progression and introduce novel molecular mechanisms of cancer development and malignant transformation involving STAT3 activation that we have identified to date. Finally, we discuss potential therapeutic strategies for cancer that target the signaling pathway to augment STAT3 activity.

LLL12B, a Novel Small-Molecule STAT3 Inhibitor, Induces Apoptosis and Suppresses Cell Migration and Tumor Growth in Triple-Negative Breast Cancer Cells

Persistent STAT3 signaling plays a pivotal role in human tumor malignancy, including triple-negative breast cancer (TNBC). There are few treatment options currently available for TNBC; thus, given its importance to cancer, STAT3 is a potential cancer therapeutic target and is the focus of drug discovery efforts. In this study, we tested a novel orally bioavailable small-molecule STAT3 inhibitor, LLL12B, in human MDA-MB-231, SUM159, and murine 4T1 TNBC cell lines. TNBC cells frequently expressed persistent STAT3 phosphorylation and their cell viability was sensitive to STAT3 knockdown by siRNA. LLL12B selectively inhibited the IL-6-mediated induction of STAT3 phosphorylation, but had little effect on the IFN-γ-mediated induction of STAT1 phosphorylation nor the EGF-mediated induction of ERK phosphorylation. In addition, targeting STAT3 with LLL12B induced apoptosis, reduced colony formation ability, and inhibited cell migration in TNBC cells. Furthermore, LLL12B suppressed the tumor growth of the MDA-MB-231 TNBC cells in a mammary fat pad mouse tumor model in vivo. Together, our findings support the concept that targeting persistent STAT3 signaling using the novel small-molecule LLL12B is a potential approach for TNBC therapy.

Design, synthesis, and biological characterization of a potent STAT3 degrader for the treatment of gastric cancer

Gastric cancer is a common malignant tumor that threatens human health, and its occurrence and development mechanism is a complex process involving multiple genes and multiple signals. Signal transducer and activator of transcription 3 (STAT3) has been elucidated as a promising target for developing anticancer drugs in gastric cancer. However, there is no FDA-approved STAT3 inhibitor yet. Herein, we report the design and synthesis of a class of STAT3 degraders based on proteolysis-targeting chimeras (PROTACs). We first synthesized an analog of the STAT3 inhibitor S3I-201 as a ligand, using the cereblon (CRBN)/cullin 4A E3 ligase ligand pomalidomide to synthesize a series of PROTACs. Among them, the SDL-1 achieves the degradation of STAT3 protein in vitro, and exhibits good anti-gastric cancer cell proliferation activity, inhibits invasion and metastasis of MKN1 cell, and induces MKN1 cell apoptosis and arrests cell cycle at the same time. Our study shows that SDL-1 is a potent STAT3 degrader and may serve as a potential anti-gastric cancer drug, providing ideas for further development of drugs for clinical use.

Inhibiting STAT3 signaling pathway by natural products for cancer prevention and therapy: In vitro and in vivo activity and mechanisms of action

Signal transducer and activator of transcription 3 (STAT3) plays a critical role in signal transmission from the plasma membrane to the nucleus, regulating the expression of genes involved in essential cell functions and controlling the processes of cell cycle progression and apoptosis. Thus, STAT3 has been elucidated as a promising target for developing anticancer drugs. Many natural products have been reported to inhibit the STAT3 signaling pathway during the past two decades and have exhibited significant anticancer activities in vitro and in vivo. However, there is no FDA-approved STAT3 inhibitor yet. The major mechanisms of these natural product inhibitors of the STAT3 signaling pathway include targeting the upstream regulators of STAT3, directly binding to the STAT3 SH2 domain and inhibiting its activation, inhibiting STAT3 phosphorylation and/or dimerization, and others. In the present review, we have systematically discussed the development of these natural product inhibitors of STAT3 signaling pathway as well as their in vitro and in vivo anticancer activity and mechanisms of action. Outlooks and perspectives on the associated challenges are provided as well.

Screening of potent STAT3-SH2 domain inhibitors from JAK/STAT compound library through molecular dynamics simulation

The Signal Transducer and Activator of Transcription 3 (STAT3) protein is activated consistently in the tumor cells and thus studied as a potent target for cancer prevention. The TYR705-phosphorylated (pTyr) STAT3 forms a homo-dimer by binding to its recognition site in the Src Homology 2 (SH2) domain of another STAT3 monomer, causing cellular survival, proliferation, inflammation, and tumor invasion. Many inhibitors of STAT3-SH2 have recently been identified using both computational and experimental approaches. In this study, we used molecular docking, Absorption, Distribution, Metabolism, and Excretion/Toxicological (ADME/tox) and molecular dynamics modeling to examine binding affinities and specificities of 191 inhibitor drugs from the SELLECKCHEM database. The binding free energies of the inhibitors were calculated by Induced Fit Docking (IFD) prime energy. The binding hotspots of STAT3-SH2 were evaluated via binding energy decomposition and hydrogen bond distribution analysis, and the inhibitor compound's stability was assessed through MD simulation. (-)-Epigallocatechin gallate, Kaempferol-3-O-rutinoside, Picroside I, Saikosaponin D, and Ginsenoside Rk1 were found to be the top hit inhibitor compounds. They exhibited an exceptional docking score, a low binding free energy, interacted with the key amino acid residue, and showed significant ADME/tox moderation. These compounds were further proved to be favorable by their stability in an MD simulation run for 100 ns using GROMACS software. The inhibitors (-)-Epigallocatechin gallate, Kaempferol-3-O-rutinoside, and Saikosaponin D show improved stability in molecular dynamic modeling and are expected to have a significant STAT3-SH2 inhibitory effect against cancer.

Pancreatic cancer growth promoted by bone marrow mesenchymal stromal cell-derived IL-6 is reversed predominantly by IL-6 blockade

Pancreatic cancer is a highly lethal cancer characterized by local invasiveness, early metastasis, recurrence and high resistance to current therapies. Extensive stroma or desmoplasia is a key histological feature of the disease, and interactions between cancer and stromal cells are critical for pancreatic cancer development and progression. Mesenchymal stromal cells [MSCs] exhibit preferential tropism to primary and metastatic tumor sites and may either suppress or support tumor growth. Although MSCs represent a potential source of pancreatic cancer stroma, their contribution to pancreatic tumor growth remains poorly known. Here, we show that bone marrow MSCs significantly contribute to pancreatic cancer growth in vitro and in vivo. Furthermore, MSCs create a pro-carcinogenic microenvironment through the release of key factors mediating growth and angiogenesis, including interleukin (IL)-6, IL-8, vascular endothelial growth factor and activation of STAT3 signaling in tumor cells. IL-6 released by MSCs was largely responsible for the pro-tumorigenic effects of MSCs. Knockdown of IL-6 expression in MSCs by small interfering RNA (siRNA) abolished the MSC growth-promoting effect in vitro, reducing tumor cell proliferation and clonogenic potential. In addition, in a heterotopic nude mouse model of human pancreatic tumor xenografts, blockade of IL-6 with the anti-IL-6 receptor antibody, tocilizumab, or of its downstream effector STAT3 with the small molecule STAT3 inhibitor S3I-201, abrogated MSC-mediated tumor promotion and delayed tumor formation significantly. Our data demonstrate that MSCs promote pancreatic cancer growth, with IL-6 produced by MSCs playing a pivotal role.

Benzobis(imidazole) derivatives as STAT3 signal inhibitors with antitumor activity

Polycyclic aromatic systems have been considered good biological probes, but some may also be good scaffolds for drug development. In this study, a series of benzobis(imidazole) derivatives were identified as STAT3 signal inhibitors, among which compound 24 showed significant inhibition of IL-6 induced JAK/STAT3 signalling pathway activation. Moreover, 24 inhibited cancer cell growth and migration, and induced cell apoptosis as well as cycle arrest in human hepatocellular carcinoma cells (HepG2) and oesophageal carcinoma cells (EC109). Compound 24 also displayed obvious antitumor activity in a mouse HepG2 cell xenograft tumor model without affecting the body weight. These results confirmed that 24 was a potential STAT3 signal inhibitor with certain antitumor activity.

STAT3 in medulloblastoma: a key transcriptional regulator and potential therapeutic target

Medulloblastoma is the most common malignant brain tumor of childhood accounting for about 60% of all pediatric embryonal tumors. Despite improvements in the overall survival rate, this tumor still lacks an efficient, reliable, and less toxic therapeutic approach. Characterization of the molecular mechanisms involved in medulloblastoma initiation and progression is a crucial step for the development of effective therapies. Signal transducer and activator of transcription 3 is a convergence point for several signaling cascades that are implicated in medulloblastoma tumorigenesis. Accumulated evidence has revealed the pivotal role of signal transducer and activator of transcription 3 in medulloblastoma pathogenesis such as proliferation, survival, angiogenesis, and immunosuppression as well as maintenance, drug resistance, and recurrence. In this review, we focus on the role of signal transducer and activator of transcription 3 in medulloblastoma tumorigenesis and discuss the recent advances of signal transducer and activator of transcription 3 inhibition as a promising developed strategy for medulloblastoma therapy.

STAT Protein Thermal Shift Assays to Monitor Protein-Inhibitor Interactions

STAT3 protein is a sought-after drug target as it plays a key role in the progression of cancer. Many STAT3 inhibitors (STAT3i) have been reported, but accumulating evidence suggests many of these act as off-target/indirect inhibitors of STAT signaling. Herein, we describe the STAT protein thermal shift assay (PTSA) as a novel target engagement tool, which we used to test the binding of known STAT3i to STAT3 and STAT1. This revealed STATTIC, BP-1-102, and Cpd188 destabilized both STATs and produced unique migratory patterns on SDS-PAGE gels, suggesting covalent protein modifications. Mass spectrometry experiments confirmed these compounds are nonspecifically alkylating STATs, as well as an unrelated protein, NUDT5. These experiments have highlighted the benefits of PTSA to investigate interactions with STAT proteins and helped reveal novel reactivity of Cpd188. The described PTSA represents a promising chemical biology tool that could be applied to an array of other protein targets.

Novel potent azetidine-based compounds irreversibly inhibit Stat3 activation and induce antitumor response against human breast tumor growth in vivo

Signal transducer and activator of transcription (Stat)3 is a valid anticancer therapeutic target. We have discovered a highly potent chemotype that amplifies the Stat3-inhibitory activity of lead compounds to levels previously unseen. The azetidine-based compounds, including H172 (9f) and H182, irreversibly bind to Stat3 and selectively inhibit Stat3 activity (IC₅₀ 0.38-0.98 μM) over Stat1 or Stat5 (IC₅₀ > 15.8 μM) in vitro. Mass spectrometry detected the Stat3 cysteine peptides covalently bound to the azetidine compounds, and the key residues, Cys426 and Cys468, essential for the high potency inhibition, were confirmed by site-directed mutagenesis. In triple-negative breast cancer (TNBC) models, treatment with the azetidine compounds inhibited constitutive and ligand-induced Stat3 signaling, and induced loss of viable cells and tumor cell death, compared to no effect on the induction of Janus kinase (JAK)2, Src, epidermal growth factor receptor (EGFR), and other proteins, or weak effects on cells that do not harbor aberrantly-active Stat3. H120 (8e) and H182 as a single agent inhibited growth of TNBC xenografts, and H278 (hydrochloric acid salt of H182) in combination with radiation completely blocked mouse TNBC growth and improved survival in syngeneic models. We identify potent azetidine-based, selective, irreversible Stat3 inhibitors that inhibit TNBC growth in vivo.

Novel STAT3 Inhibitors Targeting STAT3 Dimerization by Binding to the STAT3 SH2 Domain

Our drug discovery model has identified two novel STAT3 SH2 domain inhibitors 323–1 and 323–2 (delavatine A stereoisomers) in a series of experiments. In silico computational modeling, drug affinity responsive target stability (DARTS), and fluorescence polarization (FP) assays altogether determined that 323–1 and 323–2 directly target the STAT3 SH2 domain and inhibited both phosphorylated and non-phosphorylated STAT3 dimerization. Computational docking predicted that compound 323s bind to three subpockets of the STAT3 SH2 domain. The 323s inhibition of STAT3 dimerization was more potent than the commercial STAT3 SH2 domain inhibitor S3I-201 in the co-immunoprecipitation assay, correlating with computational docking data. The fluorescence polarization assay further confirmed that the compound 323s target the STAT3 SH2 domain by competitively abrogating the interaction between STAT3 and the SH2-binding peptide GpYLPQTV. Compared with S3I-201, the 323 compounds exhibited stronger inhibition of STAT3 and reduced the level of IL-6-stimulated phosphorylation of STAT3 (Tyr705) in LNCaP cells over the phosphorylation of STAT1 (Tyr701) induced by IFN-ɣ in PC3 cells or the phosphorylation of STAT1 (Ser727) in DU145 cells. Both compounds downregulated STAT3 target genes MCL1 and cyclin D1. Thus, the two compounds are promising lead compounds for the treatment of cancers with hyper-activated STAT3.

Advances in Immunosuppressive Agents Based on Signal Pathway

Immune abnormality involves in various diseases, such as infection, allergic diseases, autoimmune diseases, as well as transplantation. Several signal pathways have been demonstrated to play a central role in the immune response, including JAK/STAT, NF-κB, PI3K/AKT-mTOR, MAPK, and Keap1/Nrf2/ARE pathway, in which multiple targets have been used to develop immunosuppressive agents. In recent years, varieties of immunosuppressive agents have been approved for clinical use, such as the JAK inhibitor tofacitinib and the mTOR inhibitor everolimus, which have shown good therapeutic effects. Additionally, many immunosuppressive agents are still in clinical trials or preclinical studies. In this review, we classified the immunosuppressive agents according to the immunopharmacological mechanisms, and summarized the phase of immunosuppressive agents.

A Soft Zwitterionic Hydrogel as Potential Coating on a Polyimide Surface to Reduce Foreign Body Reaction to Intraneural Electrodes

Invasive intraneural electrodes can control advanced neural-interfaced prostheses in human amputees. Nevertheless, in chronic implants, the progressive formation of a fibrotic capsule can gradually isolate the electrode surface from the surrounding tissue leading to loss of functionality. This is due to a nonspecific inflammatory response called foreign-body reaction (FBR). The commonly used poly(ethylene glycol) (PEG)-based low-fouling coatings of implantable devices can be easily encapsulated and are susceptible to oxidative damage in long-term in vivo applications. Recently, sulfobetaine-based zwitterionic hydrogels have emerged as an important class of robust ultra-low fouling biomaterials, holding great potential to mitigate FBR. The aim of this proof-of-principle in vitro work was to assess whether the organic zwitterionic—poly(sulfobetaine methacrylate) [poly(SBMA)]—hydrogel could be a suitable coating for Polyimide (PI)-based intraneural electrodes to reduce FBR. We first synthesized and analyzed the hydrogel through a mechanical characterization (i.e., Young’s modulus). Then, we demonstrated reduced adhesion and activation of fibrogenic and pro-inflammatory cells (i.e., human myofibroblasts and macrophages) on the hydrogel compared with PEG-coated and polystyrene surfaces using cell viability assays, confocal fluorescence microscopy and high-content analysis of oxidative stress production. Interestingly, we successfully coated PI surfaces with a thin film of the hydrogel through covalent bond and demonstrated its high hydrophilicity via water contact angle measurement. Importantly, we showed the long-term release of an anti-fibrotic drug (i.e., Everolimus) from the hydrogel. Because of the low stiffness, biocompatibility, high hydration and ultra-low fouling characteristics, our zwitterionic hydrogel could be envisioned as long-term diffusion-based delivery system for slow and controlled anti-inflammatory and anti-fibrotic drug release in vivo.

Role of collagen regulators in cancer treatment: A comprehensive review

Abstract:

Collagen is the most important structural protein and also a main component of extra-cellular matrix (ECM). It plays a role in tumor progression. Collagen can be regulated by altering it’s biosynthesis pathway through various signaling pathways, receptors and genes. Activity of cancer cells can also be regulated by other ECM components like metalloproteinases, hyaluronic acid, fibronectin and so on. Hypoxia is also one of the condition which leads to cancer progression by stimulating the expression of procollagen lysine as a collagen crosslinker, which increases the size of collagen fibres promoting cancer spread. The collagen content in cancerous cells leads to resistance in chemotherapy. So, to reduce this resistance, some of the collagen regulating therapies are introduced, which include inhibiting its biosynthesis, disturbing cancer cell signaling pathway, mediating ECM components and directly utilizing collagenase. This study is an effort to compile the strategies reported to control the collagen level and different collagen inhibitors reported so far. More research is needed in this area, growing understandings of collagen’s structural features and its role in cancer progression will aid in the advancement of newer chemotherapies.

IL-6/JAK/STAT3 Signaling in Breast Cancer Metastasis: Biology and Treatment

Breast cancer is the most commonly diagnosed cancer in women. Metastasis is the primary cause of mortality for breast cancer patients. Multiple mechanisms underlie breast cancer metastatic dissemination, including the interleukin-6 (IL-6)-mediated signaling pathway. IL-6 is a pleiotropic cytokine that plays an important role in multiple physiological processes including cell proliferation, immune surveillance, acute inflammation, metabolism, and bone remodeling. IL-6 binds to the IL-6 receptor (IL-6Rα) which subsequently binds to the glycoprotein 130 (gp130) receptor creating a signal transducing hexameric receptor complex. Janus kinases (JAKs) are recruited and activated; activated JAKs, in turn, phosphorylate signal transducer and activator of transcription 3 (STAT3) for activation, leading to gene regulation. Constitutively active IL-6/JAK/STAT3 signaling drives cancer cell proliferation and invasiveness while suppressing apoptosis, and STAT3 enhances IL-6 signaling to promote a vicious inflammatory loop. Aberrant expression of IL-6 occurs in multiple cancer types and is associated with poor clinical prognosis and metastasis. In breast cancer, the IL-6 pathway is frequently activated, which can promote breast cancer metastasis while simultaneously suppressing the anti-tumor immune response. Given these important roles in human cancers, multiple components of the IL-6 pathway are promising targets for cancer therapeutics and are currently being evaluated preclinically and clinically for breast cancer. This review covers the current biological understanding of the IL-6 signaling pathway and its impact on breast cancer metastasis, as well as, therapeutic interventions that target components of the IL-6 pathway including: IL-6, IL-6Rα, gp130 receptor, JAKs, and STAT3.

Inhibition of STAT3-ferroptosis negative regulatory axis suppresses tumor growth and alleviates chemoresistance in gastric cancer

Chemotherapy is still one of the principal treatments for gastric cancer, but the clinical application of 5-FU is limited by drug resistance. Here, we demonstrate that ferroptosis triggered by STAT3 inhibition may provide a novel opportunity to explore a new effective therapeutic strategy for gastric cancer and chemotherapy resistance. We find that ferroptosis negative regulation (FNR) signatures are closely correlated with the progression and chemoresistance of gastric cancer. FNR associated genes (GPX4, SLC7A11, and FTH1) and STAT3 are upregulated in 5-FU resistant cells and xenografts. Further evidence demonstrates that STAT3 binds to consensus DNA response elements in the promoters of the FNR associated genes (GPX4, SLC7A11, and FTH1) and regulates their expression, thereby establishing a negative STAT3-ferroptosis regulatory axis in gastric cancer. Genetic inhibition of STAT3 activity triggers ferroptosis through lipid peroxidation and Fe²⁺ accumulation in gastric cancer cells. We further develop a potent and selective STAT3 inhibitor, W1131, which demonstrates significant anti-tumor effects in gastric cancer cell xenograft model, organoids model, and patient-derived xenografts (PDX) model partly by inducing ferroptosis, thus providing a new candidate compound for advanced gastric cancer. Moreover, targeting the STAT3-ferroptosis circuit promotes ferroptosis and restores sensitivity to chemotherapy. Our finding reveals that STAT3 acts as a key negative regulator of ferroptosis in gastric cancer through a multi-pronged mechanism and provides a new therapeutic strategy for advanced gastric cancer and chemotherapy resistance.

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Genetic and pharmacological inhibition of STAT3 triggers ferroptosis by transcriptionlly regulation of GPX4, SLC7A11, and FTH1 in gastric cancer.

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A potent and selective STAT3 inhibitor W1131, with strong anti-tumor effects, is developed.

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Ferroptosis plays a key role in the progression and chemoresistance of gastric cancer.

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Targeting the STAT3-ferroptosis circuit provides a new therapeutic strategy for advanced gastric cancer and chemotherapy resistance.

Histone H1.2 promotes hepatocarcinogenesis by regulating STAT3 signaling

Linker histone H1.2 (H1.2), encoded by HIST1H1C (H1C), is a major H1 variant in somatic cells. Among five histone H1 somatic variants, upregulated H1.2 was found in human hepatocellular carcinoma (HCC) samples and in a diethylnitrosamine (DEN)‐induced HCC mouse model. In vitro, H1.2 overexpression accelerated proliferation of HCC cell lines, whereas H1.2 knockdown (KD) had the opposite effect. In vivo, H1.2 insufficiency or deficiency (H1c KD or H1c KO) alleviated inflammatory response and HCC development in DEN‐treated mice. Mechanistically, H1.2 regulated the activation of signal transducer and activator of transcription 3 (STAT3), which in turn positively regulated H1.2 expression by binding to its promoter. Moreover, upregulation of the H1.2/STAT3 axis was observed in human HCC samples, and was confirmed in mouse models of methionine‐choline‐deficient diet induced nonalcoholic steatohepatitis or lipopolysaccharide induced acute inflammatory liver injury. Disrupting this feed‐forward loop by KD of STAT3 or treatment with STAT3 inhibitors rescued H1.2 overexpression‐induced proliferation. Moreover, STAT3 inhibitor treatment‐ameliorated H1.2 overexpression promoted xenograft tumor growth. Therefore, H1.2 plays a novel role in inflammatory response by regulating STAT3 activation in HCC, thus, blockade of the H1.2/STAT3 loop is a potential strategy against HCC.

Phosphatidylserine released from apoptotic cells in tumor induces M2-like macrophage polarization through the PSR-STAT3-JMJD3 axis

Background

Understanding how the tumor microenvironment is shaped by various factors is important for the development of new therapeutic strategies. Tumor cells often undergo spontaneous apoptotic cell death in tumor microenvironment, these apoptotic cells are histologically co‐localized with immunosuppressive macrophages. However, the mechanism by which tumor cell apoptosis modulates macrophage polarization is not fully understood. In this study, we aimed to explore the tumor promoting effects of apoptotic tumor cells and the signal pathways involved.

Methods

Apoptotic cells and macrophages in tumors were detected by immunohistochemical staining. Morphological analysis was performed with Giemsa staining. Lipids generated from apoptotic cells were detected by liquid chromatography‐mass spectrometry. Phosphatidylserine‐containing liposomes were prepared to mimic apoptotic cells. The expression of protein was determined by real‐time PCR, immunohistochemistry enzyme‐linked immunosorbent assay and Western blotting. Mouse malignant ascites and subcutaneous tumor models were designed for in vivo analysis. Transgenic mice with specific genes knocked out and inhibitors specific to certain proteins were used for the mechanistic studies.

Results

The location and the number of apoptotic cells were correlated with that of macrophages in several types of carcinomas. Phosphatidylserine, a lipid molecule generated in apoptotic cells, induced polarization and accumulation of M2‐like macrophages in vivo and in vitro. Moreover, sustained administration of phosphoserine promoted tumor growth in the malignant ascites and subcutaneous tumor models. Further analyses suggested that phosphoserine induced a M2‐like phenotype in macrophages, which was related to the activation of phosphoserine receptors including T‐cell immunoglobin mucin 4 (TIM4) and the FAK‐SRC‐STAT3 signaling pathway as well as elevated the expression of the histone demethylase Jumonji domain‐containing protein 3 (JMJD3). Administration of specific inhibitors of these pathways could reduce tumor progression.

Conclusions

This study suggest that apoptotic cell‐generated phosphoserine might be a notable signal for immunosuppressive macrophages in tumors, and the related pathways might be potential therapeutic targets for cancer therapy.

Lin28B-high breast cancer cells promote immune suppression in the lung pre-metastatic niche via exosomes and support cancer progression

The formation of pre-metastatic niche is a key step in the metastatic burden. The pluripotent factor Lin28B is frequently expressed in breast tumors and is particularly upregulated in the triple negative breast cancer subtype. Here, we demonstrate that Lin28B promotes lung metastasis of breast cancer by building an immune-suppressive pre-metastatic niche. Lin28B enables neutrophil recruitment and N2 conversion. The N2 neutrophils are then essential for immune suppression in pre-metastatic lung by PD-L2 up-regulation and a dysregulated cytokine milieu. We also identify that breast cancer-released exosomes with low let-7s are a prerequisite for Lin28B-induced immune suppression. Moreover, Lin28B-induced breast cancer stem cells are the main sources of low-let-7s exosomes. Clinical data further verify that high Lin28B and low let-7s in tumors are both indicators for poor prognosis and lung metastasis in breast cancer patients. Together, these data reveal a mechanism by which Lin28B directs the formation of an immune-suppressive pre-metastatic niche.

The establishment of a pre-metastatic niche is a key step preceding metastasis formation. Here the authors show that tumor-intrinsic Lin28B, a RNA-binding protein, has an essential role in the formation of an immune-suppressive pre-metastatic niche, promoting lung metastasis of breast cancer.

Small molecules to regulate the GH/IGF1 axis by inhibiting the growth hormone receptor synthesis

Growth hormone (GH) and insulin-like growth factor-1 (IGF1) play an important role in mammalian development, cell proliferation and lifespan. Especially in cases of tumor growth there is an urgent need to control the GH/IGF1 axis. In this study we screened a 38,480-compound library, and in two consecutive rounds of analogues selection, we identified active lead compounds based on the following criteria: inhibition the GH receptor (GHR) activity and its downstream effectors Jak2 and STAT5, and inhibition of growth of breast and colon cancer cells. The most active small molecule (BM001) inhibited both the GH/IGF1 axis and cell proliferation with an IC50 of 10-30 nM of human cancer cells. BM001 depleted GHR in human lymphoblasts. In preclinical xenografted experiments, BM001 showed a strong decrease in tumor volume in mice transplanted with MDA-MB-231 breast cancer cells. Mechanistically, the drug acts on the synthesis of the GHR. Our findings open the possibility to inhibit the GH/IGF1 axis with a small molecule.

Targeting STAT3 prevents bile reflux-induced oncogenic molecular events linked to hypopharyngeal carcinogenesis

The signal transducer and activator of transcription 3 (STAT3) oncogene is a transcription factor with a central role in head and neck cancer. Hypopharyngeal cells (HCs) exposed to acidic bile present aberrant activation of STAT3, possibly contributing to its oncogenic effect. We hypothesized that STAT3 contributes substantially to the bile reflux‐induced molecular oncogenic profile, which can be suppressed by STAT3 silencing or pharmacological inhibition. To explore our hypothesis, we targeted the STAT3 pathway, by knocking down STAT3 (STAT3 siRNA), and inhibiting STAT3 phosphorylation (Nifuroxazide) or dimerization (SI3‐201; STA‐21), in acidic bile (pH 4.0)‐exposed human HCs. Immunofluorescence, luciferase assay, Western blot, enzyme‐linked immunosorbent assay and qPCR analyses revealed that STAT3 knockdown or pharmacologic inhibition significantly suppressed acidic bile‐induced STAT3 activation and its transcriptional activity, Bcl‐2 overexpression, transcriptional activation of IL6, TNF‐α, BCL2, EGFR, STAT3, RELA(p65), REL and WNT5A, and cell survival. Our novel findings document the important role of STAT3 in bile reflux‐related molecular oncogenic events, which can be dramatically prevented by STAT3 silencing. STA‐21, SI3‐201 or Nifuroxazide effectively inhibited STAT3 and cancer‐related inflammatory phenotype, encouraging their single or combined application in preventive or therapeutic strategies of bile reflux‐related hypopharyngeal carcinogenesis.

Pharmacologic inhibiting STAT3 delays the progression of kidney fibrosis in hyperuricemia-induced chronic kidney disease

AIMS

Kidney fibrosis is a histological hallmark of chronic kidney disease (CKD), where hyperuricemia is a key independent risk factor. Considerable evidence indicated that STAT3 is one of the crucial signaling pathways in the progression of kidney fibrosis. Here, we investigated that pharmacological blockade of STAT3 delayed the progression of renal fibrosis in hyperuricemia-induced CKD.

MAIN METHODS

In the study, we used the mixture of adenine and potassium oxonate to perform kidney injury and fibrosis in hyperuricemic mice, accompanied by STAT3 activation in tubular and interstitial cells.

KEY FINDINGS

Treatment with STAT3 inhibitor S3I-201 improved renal dysfunction, reduced serum uric acid level, and delayed the progression of kidney fibrosis. Furthermore, S3I-201 could suppress fibrotic signaling pathway of TGF-β/Smads, JAK/STAT and NF-κB, as well as inhibit the expression of multiple profibrogenic cytokines/chemokines in the kidneys of hyperuricemic mice.

SIGNIFICANCE

These data suggested that STAT3 inhibition was a potent anti-fibrotic strategy in hyperuricemia-related CKD.

Resveratrol Targets a Variety of Oncogenic and Oncosuppressive Signaling for Ovarian Cancer Prevention and Treatment

Ovarian cancer is a heterogeneous disease and is also the major cause of death among women from gynecologic malignancies. A combination of surgery and chemotherapy is the major therapy for ovarian cancer. Unfortunately, despite good response rates to initial surgery and chemotherapy, most patients relapse and have a generally poor survival rate. The present research sheds light on the therapeutic effects of multiple natural products in patients with ovarian cancer. Notably, these natural ingredients do not have adverse effects on healthy cells and tissues, indicating that natural products can serve as a safe alternative therapy for ovarian cancer. Trans-3,4,5′-Trihydroxystibene (resveratrol) is a natural product that is commonly found in the human diet and that has been shown to have anticancer effects on various human cancer cells. This review summarizes current knowledge regarding the progress of resveratrol against tumor cell proliferation, metastasis, apoptosis induction, autophagy, sensitization, and antioxidation as well as anti-inflammation. It also provides information regarding the role of resveratrol analogues in ovarian cancer. A better understanding of the role of resveratrol in ovarian cancer may provide a new array for the prevention and therapy of ovarian cancer.

Emerging role of signal transducer and activator of transcription 3 (STAT3) in pituitary adenomas

Pituitary adenomas are benign tumours that can cause an individual various clinical manifestations including tumour mass effects and/or the diverse effects of abnormal pituitary hormone secretion. Given the morbidity and limited treatment options for pituitary adenomas, there is a need for better biomarkers and treatment options. One molecule that is of specific interest is the signal transducer and activator of transcription 3 (STAT3), a transcription factor that plays a critical role in mediating cytokine-induced changes in gene expression. In addition, STAT3 controls cell proliferation by regulating mitochondrial activity. Not only does activation of STAT3 play a crucial role in tumorigenesis, including pituitary tumorigenesis, but a number of studies also demonstrate pharmacological STAT3 inhibition as a promising treatment approach for many types of tumours, including pituitary tumours. This review will focus on the role of STAT3 in different pituitary adenomas, in particular, growth hormone-producing adenomas and null cell adenomas. Furthermore, how STAT3 is involved in the cell proliferation and hormone regulation in pituitary adenomas and its potential role as a molecular therapeutic target in pituitary adenomas will be summarized.

Physalin B reduces Aβ secretion through down-regulation of BACE1 expression by activating FoxO1 and inhibiting STAT3 phosphorylation

Physalin B (PB), one of the major active steroidal constituents of Solanaceae Physalis plants, has a wide variety of biological activities. We found that PB significantly down-regulated β-amyloid (Aβ) secretion in N2a/APPsw cells. However, the underlying mechanisms are not well understood. In the current study, we investigated the changes in key enzymes involved in β-amyloid precursor protein (APP) metabolism and other APP metabolites by treating N2a/APPsw cells with PB at different concentrations. The results indicated that PB reduced Aβ secretion, which was caused by down-regulation of β-secretase (BACE1) expression, as indicated at both the protein and mRNA levels. Further research revealed that PB regulated BACE1 expression by inducing the activation of forkhead box O1 (FoxO1) and inhibiting the phosphorylation of signal transducer and activator of transcription 3 (STAT3). In addition, the effect of PB on BACE1 expression and Aβ secretion was reversed by treatment with FoxO1 siRNA and STAT3 antagonist S3I-201. In conclusion, these data demonstrated that PB can effectively down-regulate the expression of BACE1 to reduce Aβsecretion by activating the expression of FoxO1 and inhibiting the phosphorylation of STAT3.

The IL6-like Cytokine Family: Role and Biomarker Potential in Breast Cancer

IL6-like cytokines are a family of regulators with a complex, pleiotropic role in both the healthy organism, where they regulate immunity and homeostasis, and in different diseases, including cancer. Here we summarise how these cytokines exert their effect through the shared signal transducer IL6ST (gp130) and we review the extensive evidence on the role that different members of this family play in breast cancer. Additionally, we discuss how the different cytokines, their related receptors and downstream effectors, as well as specific polymorphisms in these molecules, can serve as predictive or prognostic biomarkers with the potential for clinical application in breast cancer. Lastly, we also discuss how our increasing understanding of this complex signalling axis presents promising opportunities for the development or repurposing of therapeutic strategies against cancer and, specifically, breast neoplasms.

Ozone protects cardiomyocytes against ischemia/reperfusion injury: Regulating the heat shock protein 70 (HPS70) expression through activating the JAK2/STAT3 Pathway

Ischemia/reperfusion (I/R) injury causes complications in early coronary artery reperfusion for acute myocardial infarction (AMI). Ozone (O₃) has been reported to be applied for protecting I/R injury, but its detailed mechanism remains unclear. Our study focused on the protective effect of O₃ pretreatment on myocardial I/R injury and JAK2/STAT3 signaling and HSP70 regulation involving in the mediation. The rat hearts which were perfused and isolated as well as the cultured cardiomyocytes of neonatal rat were exposed to hypoxia/reoxygenation (H/R) and different concentrations of O₃ followed by heat shock protein 70 (HSP70) siRNA treatment. The results showed O₃ attenuated the suppression of cell viability induced by H/R and decreased the release of activity of creatine kinase (CK), lactate dehydrogenase (LDH) and apoptosis of cardiomyocytes in vitro. Moreover, O₃ also activated the JAK2/STAT3 signaling, upregulated the expression of HSP70 both in vitro and vivo, and decreased the index of apoptosis of cardiomyocytes caused by I/R as well as myocardial infarct area in vivo. In addition, HSP70 siRNA and JAK2 inhibitor AG490 inhibited the cardioprotective effect of O₃. And the expression of HSP70 increased by ozone was reduced by AG-490. In conclusion, our results demonstrated that ozone protects cardiomyocytes in I/R injury through regulation of the expression of HSP70 by activating the JAK2/STAT3 pathway.

Tilianin inhibits the human ovarian cancer (PA-1) cell proliferation via blocking cell cycle, inducing apoptosis and inhibiting JAK2/STAT3 signaling pathway

Ovarian cancer is one of the deadliest gynecologic malignancies and is the seventh leading cause of mortalities and morbidities globally. Although there are various therapeutic strategies, a major challenge for scientific community is to come up with effective strategy to treat ovarian cancer. Tilianin, a polyphenol flavonoid is well known for its extensive biological actions like cardioprotective, neuroprotective, anti-oxidant, anti-inflammatory, anti-diabetic and anti-tumor properties. The current study is designed to investigate the anti-cancer action of Tilianin in ovarian cancer (PA-1) cells. The findings of this study revealed that Tilianin treatment results in significant and concentration dependent decrease in cell viability. The growth inhibiting action of Tilianin is associated with apoptosis which was confirmed by DAPI and AO/EtBr staining. The Tilianin-triggered apoptosis in PA-1 cells was correlated with elevated generation of ROS, loss of mitochondrial membrane potential, alterations in pro-apoptotic (upregulated mRNA expression of Bax) and anti-apoptotic (downregulated mRNA expression of Bcl2) factors and activation of caspase-8, −9 and −3. Cell cycle analysis revealed that Tilianin treatment prevented G1/S transition through reduced mRNA expression of cyclin D1. Additionally, the findings of this study also showed Tilianin inhibited JAK2/STAT3 signaling (downregulated expression of pJAK2, JAK2, pSTAT3, and STAT3) with no change in mRNA expression level of ERK indicating its non-involvement in the apoptotic and/or growth inhibition of ovarian cancer cells. In conclusion, the findings of this exploration provided clear evidence of anti-cancer effects of Tilianin in PA-1 cells through its anti-proliferative action, ability to induce apoptosis both through extrinsic and intrinsic pathways, cell cycle (G1/S) arrest and JAK2/STAT3 signaling inhibition.

Targeting cancer stem cells in medulloblastoma by inhibiting AMBRA1 dual function in autophagy and STAT3 signalling

Medulloblastoma (MB) is a childhood malignant brain tumour comprising four main subgroups characterized by different genetic alterations and rate of mortality. Among MB subgroups, patients with enhanced levels of the c-MYC oncogene (MB_Group3) have the poorest prognosis. Here we identify a previously unrecognized role of the pro-autophagy factor AMBRA1 in regulating MB. We demonstrate that AMBRA1 expression depends on c-MYC levels and correlates with Group 3 patient poor prognosis; also, knockdown of AMBRA1 reduces MB stem potential, growth and migration of MB_Group3 stem cells. At a molecular level, AMBRA1 mediates these effects by suppressing SOCS3, an inhibitor of STAT3 activation. Importantly, pharmacological inhibition of autophagy profoundly affects both stem and invasion potential of MB_Group3 stem cells, and a combined anti-autophagy and anti-STAT3 approach impacts the MB_Group3 outcome. Taken together, our data support the c-MYC/AMBRA1/STAT3 axis as a strong oncogenic signalling pathway with significance for both patient stratification strategies and targeted treatments of MB_Group3.

Natural STAT3 inhibitors: A mini perspective

Signal transducer and activator of transcription 3 (STAT3) plays pivotal role in several cellular processes such as cell proliferation and survival and has been found to be aberrantly activated in many cancers. STAT3 is largely believed to be one of the key oncogenes and crucial therapeutic targets. Much research has suggested the leading mechanisms for regulating the STAT3 pathway and its role in promoting tumorigenesis. Therefore, intensive efforts have been devoted to develop potent STAT3 inhibitors and several of them are currently undergoing clinical trials. Nevertheless, many natural products were identified as STAT3 inhibitors but attract less attention compared to the small molecule counterpart. In this review, the development of natural STAT3 inhibitors with an emphasis on their biological profile and chemical synthesis are detailed. The current state of STAT3 inhibitors and the future directions and opportunities for STAT3 inhibitor are discussed.

Uncoupling of IL-6 signaling and LC3-associated phagocytosis drives immunoparalysis during sepsis

Immune deactivation of phagocytes is a central event in the pathogenesis of sepsis. Herein, we identify a master regulatory role of IL-6 signaling on LC3-associated phagocytosis (LAP) and reveal that uncoupling of these two processes during sepsis induces immunoparalysis in monocytes/macrophages. In particular, we demonstrate that activation of LAP by the human fungal pathogen Aspergillus fumigatus depends on ERK1/2-mediated phosphorylation of p47phox subunit of NADPH oxidase. Physiologically, autocrine IL-6/JAK2/Ninein axis orchestrates microtubule organization and dynamics regulating ERK recruitment to the phagosome and LC3⁺ phagosome (LAPosome) formation. In sepsis, loss of IL-6 signaling specifically abrogates microtubule-mediated trafficking of ERK, leading to defective activation of LAP and impaired killing of bacterial and fungal pathogens by monocytes/macrophages, which can be selectively restored by IL-6 supplementation. Our work uncovers a molecular pathway linking IL-6 signaling with LAP and provides insight into the mechanisms underlying immunoparalysis in sepsis.

Feed-forward activation of STAT3 signaling limits the efficacy of c-Met inhibitors in esophageal squamous cell carcinoma (ESCC) treatment

c-Hepatocyte growth factor receptor (Met) inhibitors have demonstrated clinical benefits in some types of solid tumors. However, the efficacy of c-Met inhibitors in esophageal squamous cell carcinoma (ESCC) remains unclear. In this study, we discovered that c-Met inhibitors induced "Signal Transducer and Activator of Transcription (STAT3)-addiction" in ESCC cells, and the feedback activation of STAT3 in ESCC cells limits the tumor response to c-Met inhibition. Mechanistically, c-Met inhibition increased the autocrine of several cytokines, including CCL2, interleukin 8, or leukemia inhibitory factor, and facilitated the interactions between the receptors of these cytokines and Janus Kinase1/2 (JAK1/2) to resultantly activate JAKs/STAT3 signaling. Pharmacological inhibition of c-Met together with cytokines/JAKs/STAT3 axis enhanced cancer cells regression in vitro. Importantly, combined c-Met and STAT3 inhibitors synergistically suppressed tumor growth and promoted the apoptosis of tumor cells without producing systematic toxicity. These findings suggest that inhibition of the STAT3 feedback loop may augment the response to c-Met inhibitors via the STAT3-mediated oncogene addiction in ESCC cells.

Recent Update on Development of Small-Molecule STAT3 Inhibitors for Cancer Therapy: From Phosphorylation Inhibition to Protein Degradation

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that regulates various biological processes, including proliferation, metastasis, angiogenesis, immune response, and chemoresistance. In normal cells, STAT3 is tightly regulated to maintain a transiently active state, while persistent STAT3 activation occurs frequently in cancers, associating with a poor prognosis and tumor progression. Targeting the STAT3 protein is a potentially promising therapeutic strategy for tumors. Although none of the STAT3 inhibitors has been marketed yet, a few of them have succeeded in entering clinical trials. This Review aims to systematically summarize the progress of the last 5 years in the discovery of directive STAT3 small-molecule inhibitors and degraders, focusing primarily on their structural features, design strategies, and bioactivities. We hope this Review will shed light on future drug design and inhibitor optimization to accelerate the discovery process of STAT3 inhibitors or degraders.

Design, synthesis, and in vitro evaluation of BP-1-102 analogs with modified hydrophobic fragments for STAT3 inhibition

Twelve novel analogs of STAT3 inhibitor BP-1-102 were designed and synthesised with the aim to modify hydrophobic fragments of the molecules that are important for interaction with the STAT3 SH2 domain. The cytotoxic activity of the reference and novel compounds was evaluated using several human and two mouse cancer cell lines. BP-1-102 and its two analogs emerged as effective cytotoxic agents and were further tested in additional six human and two murine cancer cell lines, in all of which they manifested the cytotoxic effect in a micromolar range. Reference compound S3I-201.1066 was found ineffective in all tested cell lines, in contrast to formerly published data. The ability of selected BP-1-102 analogs to induce apoptosis and inhibition of STAT3 receptor-mediated phosphorylation was confirmed. The structure–activity relationship confirmed a demand for two hydrophobic substituents, i.e. the pentafluorophenyl moiety and another spatially bulky moiety, for effective cytotoxic activity and STAT3 inhibition.

Correlation of IL-6 and JAK2/STAT3 signaling pathway with prognosis of nasopharyngeal carcinoma patients

IL-6 is reported to be the main upstream activator, instead of the downstream target of JAK2/STAT3. This study is intended to explore the correlation of IL-6 and JAK2/STAT3 signaling pathway with clinicopathological features and prognosis in nasopharyngeal carcinoma (NPC). First, NPC tissues and normal nasopharyngeal epithelial tissues were obtained from 117 NPC patients. Next, we detected expression levels of IL-6 in serum and those of STAT3, p-STAT3, JAK2, p-JAK2 and CyclinD1 in tissues. A follow-up was conducted in all the patients and the survival was analyzed. To verify the correlation of IL-6 and JAK2/STAT3 pathway, CNE-1 and SUNE1 NPC cells were interpreted with IL-6 and JAK2/STAT3 signaling pathway inhibitor AG490 to detect cell viability, migration and invasion. We observed thatIL-6 increased in serum of NPC patients. The expressions of IL-6, STAT3, p-STAT3, JAK2, p-JAK2 and CyclinD1 in NPC tissues were higher and correlated with TNM stage and lymph node metastasis (LNM). Survival rates were reduced in patients with positive expressions of IL-6, STAT3, p-STAT3, JAK2, p-JAK2 and CyclinD1. LNM and positive expressions of IL-6 and p-STAT3 were risk factors for poor prognosis of NPC. Besides, recombinant human IL-6 promoted cell proliferation, invasion and migration while AG490 inhibited cell proliferation, invasion and migration in CNE-1 and SUNE1 NPC cells. The results demonstrated that increased IL-6 expression and the activated JAK2/STAT3 signaling pathway had effects on prognosis and reduced the survival time in NPC patients, which provide a potential target for the treatment of NPC.

Architecture of Cancer-Associated Fibroblasts in Tumor Microenvironment: Mapping Their Origins, Heterogeneity, and Role in Cancer Therapy Resistance

The tumor stroma, a key component of the tumor microenvironment (TME), is a key determinant of response and resistance to cancer treatment. The stromal cells, extracellular matrix (ECM), and blood vessels influence cancer cell response to therapy and play key roles in tumor relapse and therapeutic outcomes. Of the stromal cells present in the TME, much attention has been given to cancer-associated fibroblasts (CAFs) as they are the most abundant and important in cancer initiation, progression, and therapy resistance. Besides releasing several factors, CAFs also synthesize the ECM, a key component of the tumor stroma. In this expert review, we examine the role of CAFs in the regulation of tumor cell behavior and reveal how CAF-derived factors and signaling influence tumor cell heterogeneity and development of novel strategies to combat cancer. Importantly, CAFs display both phenotypic and functional heterogeneity, with significant ramifications on CAF-directed therapies. Principal anti-cancer therapies targeting CAFs take the form of: (1) CAFs' ablation through use of immunotherapies, (2) re-education of CAFs to normalize the cells, (3) cellular therapies involving CAFs delivering drugs such as oncolytic adenoviruses, and (4) stromal depletion via targeting the ECM and its related signaling. The CAFs' heterogeneity could be a result of different cellular origins and the cancer-specific tumor microenvironmental effects, underscoring the need for further multiomics and biochemical studies on CAFs and the subsets. Lastly, we present recent advances in therapeutic targeting of CAFs and the success of such endeavors or their lack thereof. We recommend that to advance global public health and personalized medicine, treatments in the oncology clinic should be combinatorial in nature, strategically targeting both cancer cells and stromal cells, and their interactions.

HYAL4-V1/Chondroitinase (Chase) Drives Gemcitabine Resistance and Predicts Chemotherapy Failure in Patients with Bladder Cancer

PURPOSE

Gemcitabine-based chemotherapy regimens are first-line for several advanced cancers. Because of better tolerability, gemcitabine + cisplatin is a preferred neoadjuvant, adjuvant, and/or palliative chemotherapy regimen for advanced bladder cancer. Nevertheless, predicting treatment failure and overcoming resistance remain unmet clinical needs. We discovered that splice variant (V1) of HYAL-4 is a first-in-class eukaryotic chondroitinase (Chase), and CD44 is its major substrate. V1 is upregulated in bladder cancer and drives a malignant phenotype. In this study, we investigated whether V1 drives chemotherapy resistance.

EXPERIMENTAL DESIGN

V1 expression was measured in muscle-invasive bladder cancer (MIBC) specimens by qRT-PCR and IHC. HYAL-4 wild-type (Wt) and V1 were stably expressed or silenced in normal urothelial and three bladder cancer cell lines. Transfectants were analyzed for chemoresistance and associated mechanism in preclinical models.

RESULTS

V1 levels in MIBC specimens of patients who developed metastasis, predicted response to gemcitabine + cisplatin adjuvant/salvage treatment and disease-specific mortality. V1-expressing bladder cells were resistant to gemcitabine but not to cisplatin. V1 expression neither affected gemcitabine influx nor the drug-efflux transporters. Instead, V1 increased gemcitabine metabolism and subsequent efflux of difluorodeoxyuridine, by upregulating cytidine deaminase (CDA) expression through increased CD44-JAK2/STAT3 signaling. CDA inhibitor tetrahydrouridine resensitized V1-expressing cells to gemcitabine. While gemcitabine (25-50 mg/kg) inhibited bladder cancer xenograft growth, V1-expressing tumors were resistant. Low-dose combination of gemcitabine and tetrahydrouridine abrogated the growth of V1 tumors with minimal toxicity.

CONCLUSIONS

V1/Chase drives gemcitabine resistance and potentially predicts gemcitabine + cisplatin failure. CDA inhibition resensitizes V1-expressing tumors to gemcitabine. Because several chemotherapy regimens include gemcitabine, our study could have broad significance.

Mechanistic insights into ceramidase inhibitor LCL521-enhanced tumor cell killing by photodynamic and thermal ablation therapies

Our recent investigation uncovered that the acid ceramidase inhibitor LCL521 enhances the direct tumor cell killing effect of photodynamic therapy (PDT) treatment. The present study aimed at elucidating the mechanisms underlying this effect. Exposing mouse squamous cell carcinoma SCCVII cells treated with temoporfin-based PDT to LCL521 (rising ceramide concentration) produced a much greater decrease in cell survival than comparable exposure to the sphingosine kinase-1 inhibitor PF543 (that reduces sphingosine-1-phosphate concentration). This is consistent with recognizing the rising levels of pro-apoptotic sphingolipid ceramide as being more critical in promoting the death of PDT-treated cells than the reduction in the availability of pro-survival acting sphingosine-1 phosphate. This pro-apoptotic impact of LCL521, which was suppressed by the apoptosis inhibitor bongkrekic acid, involves the interaction with the cellular stress signaling network. Hence, inhibiting the key elements of these pathways markedly influenced the adjuvant effect of LCL521 on the PDT response. Particularly effective was the inositol-requiring element-1 (IRE1) kinase inhibitor STF-083010 that dramatically enhanced the killing of cells treated with PDT plus LCL521. An important role in the survival of these cells was exhibited by master transcription factors STAT3 and HIF-1α. The STAT3 inhibitor NSC 74859 was especially effective in further reducing the cell survival rates, suggesting its possible exploitation for therapeutic gain. An additional finding in this study is that LCL521-promoted PDT-mediated cell killing through ceramide-mediated lethal effects is extended to the interaction with other cancer treatment modalities with a rapid cellular stress impact such as photothermal therapy (PTT) and cryoablation therapy (CAT).

Novel STAT3 small-molecule inhibitors identified by structure-based virtual ligand screening incorporating SH2 domain flexibility

Efforts to develop STAT3 inhibitors have focused on its SH2 domain starting with short phosphotyrosylated peptides based on STAT3 binding motifs, e.g. pY₉₀₅LPQTV within gp130. Despite binding to STAT3 with high affinity, issues regarding stability, bioavailability, and membrane permeability of these peptides, as well as peptidomimetics such as CJ-887, have limited their further clinical development and led to interest in small-molecule inhibitors. Some small molecule STAT3 inhibitors, identified using structure-based virtual ligand screening (SB-VLS); while having favorable drug-like properties, suffer from weak binding affinities, possibly due to the high flexibility of the target domain. We conducted molecular dynamic (MD) simulations of the SH2 domain in complex with CJ-887, and used an averaged structure from this MD trajectory as an "induced-active site" receptor model for SB-VLS of 110,000 compounds within the SPEC database. Screening was followed by re-docking and re-scoring of the top 30% of hits, selection for hit compounds that directly interact with pY + 0 binding pocket residues R609 and S613, and testing for STAT3 targeting in vitro, which identified two lead hits with good activity and favorable drug-like properties. Unlike most small-molecule STAT3 inhibitors previously identified, which contain negatively-charged moieties that mediate binding to the pY + 0 binding pocket, these compounds are uncharged and likely will serve as better candidates for anti-STAT3 drug development. IMPLICATIONS: SB-VLS, using an averaged structure from molecular dynamics (MD) simulations of STAT3 SH2 domain in a complex with CJ-887, a known peptidomimetic binder, identify two highly potent, neutral, low-molecular weight STAT3-inhibitors with favorable drug-like properties.

A novel small molecule LLL12B inhibits STAT3 signaling and sensitizes ovarian cancer cell to paclitaxel and cisplatin

Ovarian cancer is the fifth most common cause of cancer deaths among American women. Platinum and taxane combination chemotherapy represents the first-line approach for ovarian cancer, but treatment success is often limited by chemoresistance. Therefore, it is necessary to find new drugs to sensitize ovarian cancer cells to chemotherapy. Persistent activation of Signal Transducer and Activator of Transcription 3 (STAT3) signaling plays an important role in oncogenesis. Using a novel approach called advanced multiple ligand simultaneous docking (AMLSD), we developed a novel nonpeptide small molecule, LLL12B, which targets the STAT3 pathway. In this study, LLL12B inhibited STAT3 phosphorylation (tyrosine 705) and the expression of its downstream targets, which are associated with cancer cell proliferation and survival. We showed that LLL12B also inhibits cell viability, migration, and proliferation in human ovarian cancer cells. LLL12B combined with either paclitaxel or with cisplatin demonstrated synergistic inhibitory effects relative to monotherapy in inhibiting cell viability and LLL12B-paclitaxel or LLL12B-cisplatin combination exhibited greater inhibitory effects than cisplatin-paclitaxel combination in ovarian cancer cells. Furthermore, LLL12B-paclitaxel or LLL12B-cisplatin combination showed more significant in inhibiting cell migration and growth than monotherapy in ovarian cancer cells. In summary, our results support the novel small molecule LLL12B as a potent STAT3 inhibitor in human ovarian cancer cells and suggest that LLL12B in combination with the current front-line chemotherapeutic drugs cisplatin and paclitaxel may represent a promising approach for ovarian cancer therapy.

Reprogramming Intestinal Epithelial Cell Polarity by Interleukin-22

Background: Interleukin-22 (IL-22) impacts the integrity of intestinal epithelia and has been associated with the development of colitis-associated cancer and inflammatory bowel diseases (IBD). Previous data suggest that IL-22 protects the mucosal barrier and promotes wound healing and barrier defect. We hypothesized, that IL-22 modulates cell polarity of intestinal epithelial cells (IECs) acting on tight junction assembly. The aim of the study was to investigate IL-22-dependent mechanisms in the reprogramming of intestinal epithelia.

Methods: IECs were exposed to IL-22 at various concentrations. IECs in Matrigel® were grown to 3-dimensional cysts in the presence or absence of IL-22 and morphology and expression of polarity proteins were analyzed by confocal microscopy. Epithelial cell barrier (TER and sandwich assay) and TJ assembly analysis (calcium-switch assay) were performed. TJ and cell polarity protein expression were assessed by western blotting and confocal microscopy. Cell migration and invasion assays were performed. Induction of epithelial-mesenchymal transition (EMT) was assessed by RT-qPCR analysis and western blotting. Signaling pathway analyses were performed by phosphoblotting and functional assays after blocking STAT3 and ERK signaling pathways. Using the toxoplasma-model of terminal ileitis, IL-22-knock-out mice were compared to wild-type littermates, analyzed for barrier function using one-path-impedance-analysis and macromolecular flux (H3-mannitol, Ussing-chambers).

Results: IECs exhibited a barrier defect after IL-22 exposure. TJ protein distribution and expression were severely impaired. Delayed recovery in the calcium-switch assay was observed suggesting a defect in TJ assembly. Analyzing the 3D-cyst model, IL-22 induced multi-lumen and aberrant cysts, and altered the localization of cell polarity proteins. Cell migration and invasion was caused by IL-22 as well as induction of EMT. Interestingly, only inhibition of the MAPK pathway, rescued the TJal barrier defect, while blocking STAT3 was relevant for cell survival. In addition, ileal mucosa of IL-22 deficient mice was protected from the barrier defect seen in Toxoplasma gondii-induced ileitis in wild type mice shown by significantly higher Re values and correspondingly lower macromolecule fluxes.

Conclusion: IL-22 impairs intestinal epithelial cell barrier by inducing EMT, causing defects in epithelial cell polarity and increasing cell motility and cell invasion. IL-22 modulates TJ protein expression and mediates tight junctional (TJal) barrier defects via ERK pathway.

STAT3 governs the HIF-1α response in IL-15 primed human NK cells

Natural killer (NK) cells mediate innate host defense against microbial infection and cancer. Hypoxia and low glucose are characteristic for these tissue lesions but do not affect early interferon (IFN) γ and CC chemokine release by interleukin 15 (IL-15) primed human NK cells in vitro. Hypoxia inducible factor 1α (HIF-1α) mediates cellular adaption to hypoxia. Its production is supported by mechanistic target of rapamycin complex 1 (mTORC1) and signal transducer and activator of transcription 3 (STAT3). We used chemical inhibition to probe the importance of mTORC1 and STAT3 for the hypoxia response and of STAT3 for the cytokine response in isolated and IL-15 primed human NK cells. Cellular responses were assayed by magnetic bead array, RT-PCR, western blotting, flow cytometry, and metabolic flux analysis. STAT3 but not mTORC1 activation was essential for HIF-1α accumulation, glycolysis, and oxygen consumption. In both primed normoxic and hypoxic NK cells, STAT3 inhibition reduced the secretion of CCL3, CCL4 and CCL5, and it interfered with IL-12/IL-18 stimulated IFNγ production, but it did not affect cytotoxic granule degranulation up on target cell contact. We conclude that IL-15 priming promotes the HIF-1α dependent hypoxia response and the early cytokine response in NK cells predominantly through STAT3 signaling.