STAT3 regulation of and by microRNAs in development and disease

Cucurbitacin I exerts its anticancer effects by inducing cell cycle arrest via the KAT2a-ube2C/E2F1 pathway and inhibiting HepG2-induced macrophage M2 polarization

Hepatocellular carcinoma (HCC) is one of the most common malignancies globally, particularly prevalent in China, where it accounts for nearly half of the world's new cases and deaths each year, but has limited therapeutic options. This study systematically investigated the impact of cucurbitacin I on HCC cell lines including SK-Hep-1, Huh-7, and HepG2. The results revealed that cucurbitacin I not only inhibited cell proliferation, cell migration and colony formation, but also induced apoptosis in HCC cells. The apoptotic induction was accompanied by a decrease in the expression of the anti-apoptotic factor B-cell lymphoma 2 (Bcl2), and an elevation in the expression levels of pro-apoptotic factors, including tumor protein p53 (P53), bcl2 associated X-apoptosis regulator (Bax), and caspase3 (Cas3). Additionally, cucurbitacin I caused cell cycle arrest by modulating the lysine acetyltransferase 2A (KAT2A)-E2F transcription factor 1 (E2F1)/Ubiquitin-conjugating enzyme E2 C (UBE2C) signaling axis. In terms of regulation on tumor microenvironment, cucurbitacin I was demonstrated the ability to inhibit HCC cell-induced M2 polarization of macrophages. This comprehensive study unveils the multifaceted anti-cancer mechanisms of cucurbitacin I, providing robust support for its potential application in the treatment of HCC, offering new avenues for the future development of HCC treatment strategies.

Ascorbic acid induces ferroptosis via STAT3/GPX4 signaling in oropharyngeal cancer

Ferroptosis is recognized as a new type of regulated cell death initiated by iron-dependent accumulation of lipid peroxidation. Recent studies have shown that the administration of ascorbic acid (AA) preferentially kills tumor cells by impairing iron metabolism and exerting pro-oxidant effects. Despite mounting evidence indicating the anticancer potential of AA, the underlying molecular mechanisms remain unknown. In this study, we demonstrated that AA decreased cell viability and Ki67 expression, along with its accumulation in the G0/G1 phase in FaDu and SCC-154 cell lines. Furthermore, AA exposure induced morphological changes in mitochondria associated with ferroptosis. AA-induced ferroptosis is accompanied by depletion of glutathione (GSH) and increased levels of ferrous ions (Fe2+), reactive oxygen species (ROS), and malondialdehyde (MDA). However, these ferroptotic effects were ameliorated by deferoxamine and N-acetylcysteine. Network pharmacology results showed that signal transducer and activator of transcription 3 (STAT3) is a key target of AA against oropharyngeal cancer. AA markedly downregulates the relative mRNA expression of STAT3 and glutathione peroxidase 4 (GPX4). Immunoblotting indicated that the protein levels of p-STAT3, STAT3, and GPX4 in FaDu and SCC-154 cells decreased significantly in response to AA treatment. Mechanistically, a chromatin immunoprecipitation assay confirmed that AA exposure reduced STAT3 expression in the GPX4 promoter region. Additionally, AA-induced inhibition of cell growth and ferroptosis was suppressed by STAT3 and GPX4 overexpression, respectively. In summary, AA inhibited oropharyngeal cancer cell growth in vitro by regulating STAT3/GPX4-mediated ferroptosis, which may provide a novel theoretical basis for the clinical treatment of oropharyngeal cancer with AA.

Onco-miR-21 Promotes Stat3-Dependent Gastric Cancer Progression

MicroRNA-21 (miR-21) is a small, non-coding RNA overexpressed in gastric cancer and many other solid malignancies, where it exhibits both pro-and anti-tumourigenic properties. However, the pathways regulating miR-21 and the consequences of its inhibition in gastric cancer remain incompletely understood. By exploiting the spontaneous Stat3-dependent formation of inflammation-associated gastric tumors in Gp130^F/F mice, we functionally established miR-21 as a Stat3-controlled driver of tumor growth and progression. We reconciled our discoveries by identifying several conserved Stat3 binding motifs upstream of the miR-21 gene promoter, and showed that the systemic administration of a miR-21-specific antisense oligonucleotide antagomir reduced the established gastric tumor burden in Gp130^F/F mice. We molecularly delineated the therapeutic benefits of miR-21 inhibition with the functional restoration of PTEN in vitro and in vivo, alongside an attenuated epithelial-to-mesenchymal transition and the extracellular matrix remodeling phenotype of tumors. We corroborated our preclinical findings by correlating high STAT3 and miR-21 expression with the reduced survival probability of gastric cancer patients. Collectively, our results provide a molecular framework by which miR-21 mediates inflammation-associated gastric cancer progression, and establish miR-21 as a robust therapeutic target for solid malignancies characterized by excessive Stat3 activity.

rAAV9-mediated supplementation of miR-29b improve angiotensin-II induced renal fibrosis in mice

Background

Renin–angiotensin–aldosterone system activation is the critical factor in renal remodeling and dysfunction. Our previous study suggested that miR-29b may attenuate AngII-induced renal intestinal fibrosis in vitro. In the present study, we aimed to determine whether recombinant rAAV9-mediated miR-29b delivery protects against AngII-induced renal fibrosis and dysfunction.

Method

Mice were treated with AngII via osmotic mini-pumps, or phosphate-buffered saline. rAAV9 vectors were produced using the rBac-based system in SF9 cells. rAAV9-miR-29b or rAAV9-control-miR was injected into the kidneys of mice subjected to the model of AngII infusion. The role of miR-29b in renal fibrosis was assessed using quantitative polymerase chain reaction, western blot, and histology.

Results

In AngII-induced fibrotic kidney tissue, miR-29b expression was downregulated. rAAV9-miR-29b delivery significantly reversed renal injury as indicated by decreased serum creatinine and injury related gene expression in AngII-infused mice. Regarding organ remodeling, tubulointerstitial fibrosis and deposition of extracellular matrix components such as collagen type I and type III were significantly decreased in renal tissue from mice delivered rAAV9-miR-29b.

Conclusion

Our results demonstrate great potential for use of rAAV9 as an applicable vector for delivery of miR-29b as an antifibrogenic factor for treatment of tubulointerstitial fibrosis-induced renal injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-021-00349-5.

MiRNAs directly targeting the key intermediates of biological pathways in pancreatic cancer

Pancreatic Cancer (PC) is a severe form of malignancy all over the world. Delayed diagnosis and chemoresistance are the major factors contributing to its poor prognosis and high mortality rate. The genetic and epigenetic regulations of biological pathways further complicate the progression and chemotherapy response to this cancer. MicroRNAs (MiRNAs) involvement has been observed in all types of cancers including PC. The understanding and categorization of miRNAs according to their specific targets are very important to develop early diagnostic and therapeutic interventions. The current review, emphasizing recent research findings, has categorized miRNAs that directly target the potential onco-factors that act as central converging signal-nodes in five major cancer-related pathways i.e., MAPK/ERK, JAK/STAT, Wnt/β-catenin, AKT/mTOR, and TGFβ in PC. The therapeutic perspectives of miRNAs in PC have also been discussed. This will help to understand the interplay of various miRNAs within foremost signaling pathways and develop a multifactorial approach to treat difficult-to-treat PC.

STAT3 Mediated miR-30a-5p Inhibition Enhances Proliferation and Inhibits Apoptosis in Colorectal Cancer Cells

Signal transducer and activator of transcription 3 (STAT3), a transcriptional factor involved in tumorigenesis and cancer stemness formation, contributes to drug resistance in cancer therapies. STAT3 not only mediates gene transcription but also participates in microRNA suppression. This study identified a STAT3-downstream micro RNA (miRNA) involved in drug resistance against regorafenib in colorectal cancer stem-like tumorspheres. Small RNAseq was used to investigate differential microRNAs in colorectal cancer cell-derived tumorspheres and in a STAT3-knockdown strain. The miRNA-mediated genes were identified by comparing RNAseq data with gene targets predicted using TargetScan. Assays for detecting cell viability and apoptosis were used to validate findings. The formation of colorectal cancer stem-like tumorspheres was inhibited by BBI608, a STAT3 inhibitor, but not by regorafenib. Additional investigations for microRNA expression demonstrated an increase in 10 miRNAs and a decrease in 13 miRNAs in HT29-derived tumorspheres. A comparison of small RNAseq results between tumorspheres and HT29shSTAT3 cells revealed the presence of four STAT3-mediated miRNAs in HT29-derived tumorspheres: hsa-miR-215-5p, hsa-miR-4521, and hsa-miR-215-3p were upregulated, whereas miR-30a-5p was downregulated. Furthermore, hsa-miR-4521 was associated with poor overall survival probability, and miR-30a-5p was associated with better overall survival probability in patients with rectum cancer. Comparisons of RNAseq findings between HCT116- and HT29-derived tumorspheres revealed that HSPA5 were mediated by the STAT3-miR-30a-5p axis, which is overexpressed in colorectal tumorspheres associating to anti-apoptosis. In addition, the transfection of miR-30a-5p and inhibition of HSPA5 by HA15 significantly reduced cell viability and increased apoptosis in HT29 cells. In conclusion, a STAT3-miR-30a-5p-HSPA5 axis was observed against regorafenib-mediated apoptosis in colorectal cancer tumorspheres. The expression of miR-30a-5p was repressed by STAT3; in addition, HSPA5 was identified as the target gene of miR-30a-5p and contributed to both tumorsphere formation and anti-apoptosis.

MicroRNA‑4500 suppresses tumor progression in non‑small cell lung cancer by regulating STAT3

Research has revealed that microRNA (miR)-4500 is downregulated in non-small cell lung cancer (NSCLC), and miR-4500 suppresses tumor growth by targeting lin-28 homolog B and NRAS proto-oncogene, GTPase. In the present study, it was reported that signal transducer and activator of transcription 3 (STAT3) may function as a novel target gene for miR-4500 in NSCLC. The experiments conducted in the present study confirmed that the miR-4500 expression was decreased in NSCLC tissues and cells compared with adjacent normal tissues and a normal lung cell line. miR-4500 suppressed the cell proliferation, migration, invasion and promoted apoptosis of the human NSCLC cell lines A549 and H1975. Expression of STAT3 was negatively correlated with miR-4500 expression in vivo. A luciferase reporter assay suggested that miR-4500 directly targeted the 3′ untranslated region of STAT3. The tumor inhibition effect of small interfering RNA STAT3 in A549 and H1975 lines may be partially impaired by a miR-4500 inhibitor. The results of the present study suggests that miR-4500 may be a tumor suppressor and a potential therapeutic target in NSCLC.

Immunosuppression by monocytic myeloid-derived suppressor cells in patients with pancreatic ductal carcinoma is orchestrated by STAT3

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a highly devastating disease with an overall 5-year survival rate of less than 8%. New evidence indicates that PDAC cells release pro-inflammatory metabolites that induce a marked alteration of normal hematopoiesis, favoring the expansion and accumulation of myeloid-derived suppressor cells (MDSCs). We report here that PDAC patients show increased levels of both circulating and tumor-infiltrating MDSC-like cells.

METHODS

The frequency of MDSC subsets in the peripheral blood was determined by flow cytometry in three independent cohorts of PDAC patients (total analyzed patients, n = 117). Frequency of circulating MDSCs was correlated with overall survival of PDAC patients. We also analyzed the frequency of tumor-infiltrating MDSC and the immune landscape in fresh biopsies. Purified myeloid cell subsets were tested in vitro for their T-cell suppressive capacity.

RESULTS

Correlation with clinical data revealed that MDSC frequency was significantly associated with a shorter patients' overall survival and metastatic disease. However, the immunosuppressive activity of purified MDSCs was detectable only in some patients and mainly limited to the monocytic subset. A transcriptome analysis of the immunosuppressive M-MDSCs highlighted a distinct gene signature in which STAT3 was crucial for monocyte re-programming. Suppressive M-MDSCs can be characterized as circulating STAT3/arginase1-expressing CD14+ cells.

CONCLUSION

MDSC analysis aids in defining the immune landscape of PDAC patients for a more appropriate diagnosis, stratification and treatment.

Reciprocal regulation of miR-206 and IL-6/STAT3 pathway mediates IL6-induced gefitinib resistance in EGFR-mutant lung cancer cells

Persistently activated IL‐6/STAT3 pathway promotes acquired resistance to targeted therapy with epidermal growth factor receptor‐tyrosine kinase inhibitors (EGFR‐TKIs) in non–small‐cell lung cancer (NSCLC) treatment. miR‐206 has been verified to be dysregulated and plays as a negative regulator in lung cancer. However, whether miR‐206 may overcome IL6‐induced gefitinib resistance in EGFR‐mutant lung cancer remains elusive. In this study, we investigated the role of miR‐206 in IL6‐induced gefitinib‐resistant EGFR‐mutated lung cancer cell lines. We showed that forced miR‐206 expression restored gefitinib sensitivity in IL6‐induced gefitinib‐resistant EGFR‐mutant lung cancer cells by inhibiting IL6/JAK1/STAT3 pathway. Specifically, mechanistic investigations revealed that miR‐206 blocked IL‐6/STAT3 signalling via directly targeting the 3'‐UTR of intracellular IL‐6 messenger RNA. Moreover, IL‐6 induced miR‐206 down‐regulation by reducing the cropping process of primary miR‐206 (pri‐miR‐206) into the Drosha/DGCR8 complex. Taken together, our findings reveal a direct role of miR‐206 in regulating IL‐6/STAT3 pathway and contrarily activated IL‐6/STAT3 signalling mediates the miR‐206 maturation process in gefitinib‐resistant EGFR‐mutant lung cancer cells.

HuR counteracts miR-330 to promote STAT3 translation during inflammation-induced muscle wasting

Debilitating cancer-induced muscle wasting, a syndrome known as cachexia, is lethal. Here we report a posttranscriptional pathway involving the RNA-binding protein HuR as a key player in the onset of this syndrome. Under these conditions, HuR switches its function from a promoter of muscle fiber formation to become an inducer of muscle loss. HuR binds to the STAT3 (signal transducer and activator of transcription 3) mRNA, which encodes one of the main effectors of this condition, promoting its expression both in vitro and in vivo. While HuR does not affect the stability and the cellular movement of this transcript, HuR promotes the translation of the STAT3 mRNA by preventing miR-330 (microRNA 330)-mediated translation inhibition. To achieve this effect, HuR directly binds to a U-rich element in the STAT3 mRNA-3'untranslated region (UTR) located within the vicinity of the miR-330 seed element. Even though the binding sites of HuR and miR-330 do not overlap, the recruitment of either one of them to the STAT3-3'UTR negatively impacts the binding and the function of the other factor. Therefore, together, our data establish the competitive interplay between HuR and miR-330 as a mechanism via which muscle fibers modulate, in part, STAT3 expression to determine their fate in response to promoters of muscle wasting.

Targeted inhibition of STAT3 as a potential treatment strategy for atherosclerosis

Atherosclerosis is the main pathological basis of ischemic cardiovascular and cerebrovascular diseases and has attracted more attention in recent years. Multiple studies have demonstrated that the signal transducer and activator of transcription 3 (STAT3) plays essential roles in the process of atherosclerosis. Moreover, aberrant STAT3 activation has been shown to contribute to the occurrence and development of atherosclerosis. Therefore, the study of STAT3 inhibitors has gradually become a focal research topic. In this review, we describe the crucial roles of STAT3 in endothelial cell dysfunction, macrophage polarization, inflammation, and immunity during atherosclerosis. STAT3 in mitochondria is mentioned as well. Then, we present a summary and classification of STAT3 inhibitors, which could offer potential treatment strategies for atherosclerosis. Furthermore, we enumerate some of the problems that have interfered with the development of mature therapies utilizing STAT3 inhibitors to treat atherosclerosis. Finally, we propose ideas that may help to solve these problems to some extent. Collectively, this review may be useful for developing future STAT3 inhibitor therapies for atherosclerosis.

The full recovery of mice (Mus Musculus C57BL/6 strain) from virus-induced sarcoma after treatment with a complex of DDMC delivery system and sncRNAs

BACKGROUND

Virus-induced cellular genetic modifications result in the development of many human cancers.

METHODS

In our experiments, we used the RVP3 cell line, which produce primary mouse virus-induced sarcoma in 100% of cases. Inbreed 4-week-old female C57BL/6 mice were injected subcutaneously in the interscapular region with RVP3 cells. Three groups of mice were used. For treatment, one and/or two intravenous injections of a complex of small non-coding RNAs (sncRNAs) a-miR-155, piR-30074, and miR-125b with a 2-diethylaminoethyl-dextran methyl methacrylate copolymer (DDMC) delivery system were used. The first group consisted of untreated animals (control). The second group was treated with one injection of complex DDMC/sncRNAs (1st group). The third group was treated with two injections of complex DDMC/sncRNAs (2nd group). The tumors were removed aseptically, freed of necrotic material, and used with spleen and lungs for subsequent RT-PCR and immunofluorescence experiments, or stained with Leishman-Romanowski dye.

RESULTS

As a result, the mice fully recovered from virus-induced sarcoma after two treatments with a complex including the DDMC vector and a-miR-155, piR-30074, and miR-125b. In vitro studies showed genetic and morphological transformations of murine cancer cells after the injections.

CONCLUSIONS

Treatment of virus-induced sarcoma of mice with a-miR-155, piR-30074, and miR-125b as active component of anti-cancer complex and DDMC vector as delivery system due to epigenetic-regulated transformation of cancer cells into cells with non-cancerous physiology and morphology and full recovery of disease.

MicroRNA-messenger RNA interactions involving JAK-STAT signaling genes in colorectal cancer

JAK-STAT signaling influences many downstream processes that, unchecked, contribute to carcinogenesis and metastasis. MicroRNAs (miRNAs) are hypothesized as a mechanism to prevent uncontrolled growth from continuous JAK-STAT activation. We investigated differential expression between paired carcinoma and normal colorectal mucosa of messenger RNAs (mRNAs) and miRNAs using RNA-Seq and Agilent Human miRNA Microarray V19.0 data, respectively, using a negative binomial mixed effects model to test 122 JAK-STAT-signaling genes in 217 colorectal cancer (CRC) cases. Overall, 42 mRNAs were differentially expressed with a fold change of >1.50 or <0.67, remaining significant with a false discovery rate of < 0.05; four were dysregulated in microsatellite stable (MSS) tumors, eight were for microsatellite unstable (MSI)-specific tumors. Of these 54 mRNAs, 17 were associated with differential expression of 46 miRNAs, comprising 116 interactions: 16 were significant overall, one for MSS tumors only. Twenty of the 29 interactions with negative beta coefficients involved miRNA seed sequence matches with mRNAs, supporting miRNA-mediated mRNA repression; 17 of these mRNAs encode for receptor molecules. Receptor molecule degradation is an established JAK-STAT signaling control mechanism; our results suggest that miRNAs facilitate this process. Interactions involving positive beta coefficients may illustrate downstream effects of disrupted STAT activity, and subsequent miRNA upregulation.

Preliminary Report on the Association Between STAT3 Polymorphisms and Susceptibility to Acute Kidney Injury After Cardiopulmonary Bypass

Cardiopulmonary bypass-associated acute kidney injury (CPB-AKI) is a well-recognized complication which is clearly linked to increased morbidity and mortality. Due to important role of inflammation in CPB-AKI pathogenesis, we explored the association between polymorphisms in STAT3, an inflammation-associated transcription factor, and the risk of CPB-AKI. In this study, STAT3 rs1053004 and rs744166 polymorphisms were analyzed in 129 patients undergoing coronary artery bypass grafting in Jorjani heart center, Bandar Abbas, Iran. The genotypes were determined using sequence-specific primers (PCR-SSP). Sixty-three patients met the criteria for AKI after cardiac surgery (AKI group). The remaining 66 patients did not develop AKI (non-AKI group). Rs1053004 GG genotype was significantly associated with a decreased risk (OR 0.4, 95% CI 0.17-0.9, P = 0.03) of CPB-AKI. Subgroup analyses revealed that GG genotype has also a protective effect in older patients (Age ≥ 60) (OR 0.19, 95% CI 0.04-0.8, P = 0.01). However, rs744166 did not show any difference between AKI and non-AKI groups. The result of our study for the first time provides evidence that rs1053004 polymorphism is significantly associated with a decreased risk of CPB-AKI in Iranian population, especially in older subjects.

MiRNA-543 promotes osteosarcoma cell proliferation and glycolysis by partially suppressing PRMT9 and stabilizing HIF-1α protein

Osteosarcoma (OS) is the most common primary bone tumor, occurring frequently in adolescents and possessing a high malignant severity. MicroRNAs play critical roles during OS development. Thus, elucidation of the involvement of specific microRNAs in the development of OS may provide novel therapeutic targets for OS treatment. Here, we showed that in the OS specimens from patients, the levels of miR-543 were significantly increased whereas the levels of PRMT9 were significantly decreased, compared to the paired normal bone tissue. Moreover, miR-543 and PRMT9 inversely correlated in the OS cell lines. Bioinformatics analyses predicted that miR-543 may target the 3'-UTR of PRMT9 mRNA to inhibit its translation, which was confirmed by luciferase-reporter assay. MiR-543 promoted OS cell proliferation in vitro and in vivo. Mechanistically, miR-543 inhibited PRMT9-enhanced cell oxidative phosphorylation, while miR-543 depletion promoted PRMT9-increased HIF-1α instability and inhibited glycolysis in OS cells. Clinically, miR-543 expression was negatively correlated with PRMT9 expression in OS tissues. Together, our data provide important evidence for glycolysis in OS development, and suggest that targeting glycolytic pathway through miR-543/PRMT9/HIF-1α axis may represent a potential therapeutic strategy to eradicate OS cells.

Baicalin attenuates lipopolysaccharide-induced pro-inflammatory cytokine expression in murine macrophage cell line RAW264.7 through miR-124-STAT3 axis

Baicalin, a flavonoid isolated from Scutellaria baicalensis Georgi, has shown a wide range of anti-inflammatory, antioxidative, antiviral, and antitumor properties. However, the molecular mechanism of how baicalin exerts its effects, especially on inflammation regulation, has not been fully investigated. In this article, we report the effects of baicalin on the mouse macrophage cell line RAW264.7. Our results demonstrate that baicalin inhibits the production of inflammatory factors interleukin-6 and tumor necrosis factor-alpha upon lipopolysaccharide stimulation of macrophages. We observed that baicalin inhibits STAT3 activation through retarding its expression and phosphorylation. Interestingly, baicalin treatment promotes the elevation of miR-124 in lipopolysaccharide-treated macrophages. Overexpression of the miR-124 mimic in RAW264.7 reduced STAT3 expression and phosphorylation. Furthermore, inhibition of miR-124 attenuated the dysregulation of STAT3 and reduction of inflammatory factors upon baicalin treatment. Our results revealed the molecular mechanism that baicalin attenuates pro-inflammatory cytokine production through miR-124-STAT3 signaling pathway, suggesting that miR-124 is an important modulator in regulating anti-inflammation by baicalin in macrophages.

Bromocriptine for the Treatment of Peripartum Cardiomyopathy

Peripartum cardiomyopathy (PPCM) is a life-threatening, pregnancy-associated heart disease that develops towards the end of pregnancy or in the first months following delivery in previously healthy women. Understanding of the pathophysiology has progressed in recent years, highlighting an oxidative-stress mediated cleavage of the nursing hormone prolactin into a toxic 16-kDa prolactin fragment as a major factor driving the disease. The 16-kDa prolactin fragment induces detrimental but potentially reversible effects on heart function. Bromocriptine, a clinically-approved drug to block prolactin release, was initially tested in a PPCM mouse model where it efficiently prevented the onset of PPCM. Consequently, this treatment concept was transferred to and successfully used in humans as a bench-tobedside approach. Encouraging proof-of-concept studies led to a randomised trial that further strengthens the role of bromocriptine in addition to standard heart failure therapy in clinical practice. The aim of this article is to summarise this novel and disease-specific medical treatment, along with current knowledge on the epidemiology and pathophysiology of PPCM.

IL-6/STAT3 signaling in mice with dysfunctional type-2 ryanodine receptor

Mice with genetically modified cardiac ryanodine receptor (Ryr2^ADA/ADA mice) are impaired in regulation by calmodulin, develop severe cardiac hypertrophy and die about 2 weeks after birth. We hypothesized that the interleukin 6 (IL-6)/signal transducer and activator of transcription-3 (STAT3) signaling pathway has a role in the development of the Ryr2^ADA/ADA cardiac hypertrophy phenotype, and determined cardiac function and protein levels of IL-6, phosphorylation levels of STAT3, and downstream targets c-Fos and c-Myc in wild-type and RyR2^ADA/ADA mice, mice with a disrupted IL-6 gene, and mice treated with STAT3 inhibitor NSC74859. IL-6 protein levels were increased at postnatal day 1 but not day 10, whereas pSTAT3-Tyr705/STAT3 ratio and c-Fos and c-Myc protein levels increased in hearts of 10-day but not 1-day old Ryr2^ADA/ADA mice compared with wild type. Both STAT3 and pSTAT3-Tyr705 accumulated in the nuclear fraction of 10-day old Ryr2^ADA/ADA mice compared with wild type. Ryr2^{ADA /ADA} /IL-6^−/− mice lived 1.5 times longer, had decreased heart to body weight ratio, and reduced c-Fos and c-Myc protein levels. The STAT3 inhibitor NSC74859 prolonged life span by 1.3-fold, decreased heart to body weight ratio, increased cardiac performance, and decreased pSTAT-Tyr705/STAT3 ratio and IL-6, c-Fos and c-Myc protein levels of Ryr2^{ADA /ADA} mice. The results suggest that upregulation of IL-6 and STAT3 signaling contributes to cardiac hypertrophy and early death of mice with a dysfunctional ryanodine receptor. They further suggest that STAT3 inhibitors may be clinically useful agents in patients with altered Ca²⁺ handling in the heart.

STAT3 is Overactivated in Gastric Cancer Stem-Like Cells

Objective

Gastric cancer (GC) is widely associated with chronic inflammation. The pro inflammatory microenvironment provides conditions that disrupt stem/progenitor cell proliferation and differentiation. The signal transducer and activator of transcrip- tion-3 (STAT3) signaling pathway is involved in inflammation and also contributes to the maintenance of embryonic stem cell (ESCs) pluripotency. Here, we have investi- gated the activation status of STAT3 in GC stem-like cells (GCSLCs).

Materials and Methods

In this experimental research, CSLCs derived from the human GC cell line MKN-45 and patient specimens, through spheroid body formation, character- ized and then assayed for the STAT3 transcription factor expression in mRNA and protein level further to its activation.

Results

Spheroid cells showed higher potential for spheroid formation than the pa- rental cells. Furthemore, stemness genes NANOG, c-MYC and SOX-2 were over expressed in spheroids of MKN-45 and in patient samples. In MKN-45 spheroid cells, epithelial mesenchymal transition (EMT) related markers CDH2, SNAIL2, TWIST and VIMENTIN were upregulated (P<0.05), but we observed no change in expression of the E-cadherin epithelial marker. These cells exhibited more resistance to docetaxel (DTX) when compared with parental cells (P<0.05) according to the MTS assay. Al- though immunostaining and Western blotting showed expression of the STAT3 pro- tein in both spheroids and parents, the mRNA level of STAT3 in spheroids was higher than the parents. Nuclear translocation of STAT3 was accompanied by more intensive phospho-STAT3 (p-STAT3) in spheroid structures relative to the parent cells accord- ing to flow cytometry analysis (P<0.05).

Conclusion

The present findings point to STAT3 over activation in GCSLCs. Com- plementary experiments are required to extend the role of STAT3 in stemness fea- tures and invasion properties of GCSCs and to consider the STAT3 pathway for CSC targeted therapy.

Characterization of STAT3 expression, signaling and inhibition in feline oral squamous cell carcinoma

Background

Signal transducer and activator of transcription 3 (STAT3) plays a critical role in tumor development by regulating signaling pathways involved in cell proliferation, survival, metastasis and angiogenesis. STAT3 is activated in many cancers, including head and neck squamous cell carcinoma (HNSCC) in people. Feline oral squamous cell carcinoma (OSCC) is similar to advanced or recurrent HNSCC as it is poorly responsive to traditional therapies and carries a poor long-term prognosis. The purpose of this study was to characterize expression and activation of STAT3 in feline OSCC cell lines and tumor samples and to investigate the biologic activity of a novel, allosteric STAT3 inhibitor, LLL12, in feline OSCC cell lines.

Results

We evaluated 3 feline OSCC cell lines and one of these (SCCF2) exhibited high levels of constitutive STAT3 phosphorylation and high sensitivity to LLL12 treatment. Exposure of SCCF2 cells to LLL12 resulted in decreased expression of pSTAT3 and total STAT3, apoptosis as assessed by caspase 3/7 activation, inhibition of colony formation and reduced expression of the STAT3 transcriptional target survivin. In contrast, the STAT3 transcriptional targets VEGF and MCL-1 increased after LLL12 treatment. This was, in part, likely due to LLL12 mediated upregulation of HIF-1α, which is known to drive VEGF and MCL-1 expression. The OSCC cell lines with low basal STAT3 phosphorylation did not exhibit these effects, suggesting that STAT3 inhibition was responsible for the observed results. Lastly, immunohistochemistry for pSTAT3 was performed using a feline OSCC tissue microarray, demonstrating expression in 48 % of samples tested.

Conclusions

These data demonstrate that LLL12 has biologic activity against a feline OSCC cell line expressing pSTAT3 and that STAT3 represents a target for therapeutic intervention in this disease. However, given the up-regulation of several STAT3 transcriptional targets following treatment, further investigation of STAT3 and its related signaling pathways in OSCC is warranted.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0505-7) contains supplementary material, which is available to authorized users.

miR-519d-mediated downregulation of STAT3 suppresses breast cancer progression

MicroRNAs (miRNAs) play important roles in the the gene regulation of carcinogenesis including breast cancer. miR‑519d has been studied in various types of cancer, but its role in breast cancer remains unclear. In the present study, we investigated the expression and biological function of miR-519d in breast cancer. Using quantitative RT-PCR (RT-qPCR) analysis, we analyzed the expression of miR-519d in breast cancer tissues and cell lines. It was shown that miR-519d expression was decreased in cancer tissues and cell lines compared with their controls. Overexpression of miR-519d inhibited cell proliferation and invasion, and induced apoptosis of breast cancer cells. Signal transducer and activator of transcription 3 (STAT3) was predicted as a target gene of miR-519d and it was verified by the luciferase reporter assay. Additionally, STAT3 mRNA and protein expression levels were downregulated in the cells with miR-519d overexpression as determined by RT-qPCR and western blotting. Taken together, the results indicated that miR-519d functions as a tumor suppressor in breast cancer by suppressing STAT3 expression.

MicroRNA as Type I Interferon-Regulated Transcripts and Modulators of the Innate Immune Response

Type I interferons (IFNs) are an important family of cytokines that regulate innate and adaptive immune responses to pathogens, in cancer and inflammatory diseases. While the regulation and role of protein-coding genes involved in these responses are well characterized, the role of non-coding microRNAs in the IFN responses is less developed. We review the emerging picture of microRNA regulation of the IFN response at the transcriptional and post-transcriptional level. This response forms an important regulatory loop; several microRNAs target transcripts encoding components at many steps of the type I IFN response, both production and action, at the receptor, signaling, transcription factor, and regulated gene level. Not only do IFNs regulate positive signaling molecules but also negative regulators such as SOCS1. In total, 36 microRNA are reported as IFN regulated. Given this apparent multipronged targeting of the IFN response by microRNAs and their well-characterized capacity to “buffer” responses in other situations, the prospects of improved sequencing and microRNA targeting technologies will facilitate the elucidation of the broader regulatory networks of microRNA in this important biological context, and their therapeutic and diagnostic potential.

Emerging translational approaches to target STAT3 signalling and its impact on vascular disease

Acute and chronic inflammation responses characterize the vascular remodelling processes in atherosclerosis, restenosis, pulmonary arterial hypertension, and angiogenesis. The functional and phenotypic changes in diverse vascular cell types are mediated by complex signalling cascades that initiate and control genetic reprogramming. The signalling molecule's signal transducer and activator of transcription 3 (STAT3) plays a key role in the initiation and continuation of these pathophysiological changes. This review highlights the pivotal involvement of STAT3 in pathological vascular remodelling processes and discusses potential translational therapies, which target STAT3 signalling, to prevent and treat cardiovascular diseases. Moreover, current clinical trials using highly effective and selective inhibitors of STAT3 signalling for distinct diseases, such as myelofibrosis and rheumatoid arthritis, are discussed with regard to their vascular (side-) effects and their potential to pave the way for a direct use of these molecules for the prevention or treatment of vascular diseases.

STAT3 regulates steady-state expression of synaptopodin in cultured mouse podocytes

The transcription factor signal transducer and activator of transcription-3 (STAT3) is activated by proinflammatory cytokines and circulating factors in many cell types. Synaptopodin (Synpo) is a cytoskeleton regulatory protein expressed in podocyte foot processes that regulates the dynamics of actin filaments and the stability of small GTPases. Here we show that inhibition of STAT3 signaling using the small-molecule inhibitor benzo[b]thiophene,6-nitro-,1,1-dioxide (Stattic), or by STAT3 knockdown by small interfering RNA, caused a decrease in Synpo mRNA and protein in an immortalized mouse podocyte cell line. This loss of Synpo, which occurred in 30-80 minutes, was also seen after treatment with the translational inhibitor cycloheximide. The loss of Synpo protein after Stattic or cycloheximide treatment did not occur when podocytes were simultaneously exposed to 1-[N-[(l-3-trans-carboxyoxirane-2-carbonyl)-l-leucyl]amino]-4-guanidinobutane (E-64), an inhibitor of thiol proteases such as cathepsin L. Treatment with interleukin-6 (IL-6) increased tyrosine phosphorylation of STAT3 and evoked a parallel increase in Synpo levels in podocytes. The stimulatory effect of IL-6 on Synpo was completely inhibited by pretreatment with Stattic. By contrast, 30-60-minute exposure to angiotensin II (Ang II) inhibited STAT3 signaling and concurrently reduced Synpo protein levels. The Ang II-evoked loss of Synpo was prevented by E-64 but not by inhibition of calcineurin or blockade of transient receptor potential cation channels. Inhibition of STAT3 by Stattic caused marked changes in the distribution of podocyte actin filaments, and caused a nearly complete suppression of the migration of these cells in wound assays, consistent with the loss of Synpo. Stattic treatment also caused loss of RhoA protein.

Emerging role of microRNA in hepatocellular carcinoma (Review)

Hepatocellular carcinoma is a type of cancer characterized by significant morbidity and high mortality rates worldwide. Previous studies have revealed that alterations in microRNA (miRNA) expression are a common feature of cancer. Furthermore, as evolutionarily conserved, non-encoding RNAs, miRNAs have demonstrated fundamental roles in the various biological processes involved in cancer. Genome-wide miRNA expression profile studies and bioinformatic methods have provided comprehensive insight into the role of cancer-related miRNAs. In addition, investigation of the function and mechanisms of miRNAs has provided an understanding of the association with the pathogenesis of cancer. In the present review, the tumor-promoting or tumor-suppressive roles and underlying mechanisms of certain significant miRNAs at a single and integral level are summarized. Furthermore, the recognition of miRNA-gene networks and current advances in the potential use of miRNA-based diagnosis and therapy are discussed.

HIV-1 gp120 activates the STAT3/interleukin-6 axis in primary human monocyte-derived dendritic cells

Dendritic cells (DCs) are fundamental for the initiation of immune responses and are important players in AIDS immunopathogenesis. The modulation of DC functional activities represents a strategic mechanism for HIV-1 to evade immune surveillance. Impairment of DC function may result from bystander effects of HIV-1 envelope proteins independently of direct HIV-1 infection. In this study, we report that exposure of immature monocyte-derived DCs (MDDCs) to HIV-1 R5 gp120 resulted in the CCR5-dependent production of interleukin-6 (IL-6) via mitogen-activated protein kinase (MAPK)/NF-κB pathways. IL-6 in turn activated STAT3 by an autocrine loop. Concomitantly, gp120 promoted an early activation of STAT3 that further contributed to IL-6 induction. This activation paralleled a concomitant upregulation of the STAT3 inhibitor PIAS3. Notably, STAT3/IL-6 pathway activation was not affected by the CCR5-specific ligand CCL4. These results identify STAT3 as a key signaling intermediate activated by gp120 in MDDCs and highlight the existence of a virus-induced dysregulation of the IL-6/STAT3 axis. HIV-1 gp120 signaling through STAT3 may provide an explanation for the impairment of DC function observed upon HIV exposure.

IMPORTANCE

This study provides new evidence for the molecular mechanisms and signaling pathways triggered by HIV-1 gp120 in human DCs in the absence of productive infection, emphasizing a role of aberrant signaling in early virus-host interaction, contributing to viral pathogenesis. We identified STAT3 as a key component in the gp120-mediated signaling cascade involving MAPK and NF-κB components and ultimately leading to IL-6 secretion. STAT3 now is recognized as a key regulator of DC functions. Thus, the identification of this transcription factor as a signaling molecule mediating some of gp120's biological effects unveils a new mechanism by which HIV-1 may deregulate DC functions and contribute to AIDS pathogenesis.

Silencing of Dicer1 temporally separates pro- and anti-apoptotic signaling and confers susceptibility to chemotherapy in p53 mutated cells

miRNAs are critically implicated in the initiation process of and progression through cancerogenesis. The mechanisms, however, by which miRNAs interfere with the signalosomes of human cancer cells, are still obscure. We utilized the p53-mutated human keratinocyte cell line HACAT to investigate the biological significance and extent to which miRNAs regulate proliferation, cell growth, and apoptosis in transformed phenotypes. Silencing of the miRNA-processing enzyme Dicer1 resulted in cell cycle arrest at the G1/S border, along with restoration of CDK inhibitor p21(CIP)expression. Employing a cell cycle-wide phospho-proteomic approach, we detected neglectable changes in abundance and schedule of overall and cell cycle periodic protein expression despite cell cycle arrest of Dicer1-depleted cells. Instead, we found substantially delayed post-translational modifications of some, but not all, signaling nodes. Phospho-site-specific analyses revealed that pro-apoptotic information elicited by Myc, β-catenin, and other mitotic pathways early in G1 are absorbed and balanced by anti-apoptotic signaling from AKT and NFκB in Dicer1-competent cells. The absence of regulatory miRNAs, however, led to a substantial delay of anti-apoptotic signaling, leaving pro-apoptotic stress unbalanced in Dicer1-deprived cells. We here show that this temporal separation of pro- and anti-apoptotic signaling induced by inhibition of Dicer1 is synergistic and synthetic lethal to low-dose 5-FU chemotherapy in p53-mutated HACAT cells. The findings reported here contribute to the understanding of the complex interactions of miRNAs with the signalosom of transformed phenotypes and may help to design novel strategies to fight cancer.

The Role of STAT3 in Non-Small Cell Lung Cancer

Persistent phosphorylation of signal transducer and activator of transcription 3 (STAT3) has been demonstrated in 22%~65% of non-small cell lung cancers (NSCLC). STAT3 activation is mediated by receptor tyrosine kinases, such as epidermal growth factor receptor (EGFR) and MET, cytokine receptors, such as IL-6, and non-receptor kinases, such as Src. Overexpression of total or phosphorylated STAT3 in resected NSCLC leads to poor prognosis. In a preclinical study, overexpression of STAT3 was correlated with chemoresistance and radioresistance in NSCLC cells. Here, we review the role of STAT3 and the mechanisms of treatment resistance in malignant diseases, especially NSCLC. As STAT3 is a critical mediator of the oncogenic effects of EGFR mutations, we discuss STAT3 pathways in EGFR-mutated NSCLC, referring to mechanisms of EGFR tyrosine kinase inhibitor resistance.

Constructing higher-order miRNA-mRNA interaction networks in prostate cancer via hypergraph-based learning

BACKGROUND

Dysregulation of genetic factors such as microRNAs (miRNAs) and mRNAs has been widely shown to be associated with cancer progression and development. In particular, miRNAs and mRNAs cooperate to affect biological processes, including tumorigenesis. The complexity of miRNA-mRNA interactions presents a major barrier to identifying their co-regulatory roles and functional effects. Thus, by computationally modeling these complex relationships, it may be possible to infer the gene interaction networks underlying complicated biological processes.

RESULTS

We propose a data-driven, hypergraph structural method for constructing higher-order miRNA-mRNA interaction networks from cancer genomic profiles. The proposed model explicitly characterizes higher-order relationships among genetic factors, from which cooperative gene activities in biological processes may be identified. The proposed model is learned by iteration of structure and parameter learning. The structure learning efficiently constructs a hypergraph structure by generating putative hyperedges representing complex miRNA-mRNA modules. It adopts an evolutionary method based on information-theoretic criteria. In the parameter learning phase, the constructed hypergraph is refined by updating the hyperedge weights using the gradient descent method. From the model, we produce biologically relevant higher-order interaction networks showing the properties of primary and metastatic prostate cancer, as candidates of potential miRNA-mRNA regulatory circuits.

CONCLUSIONS

Our approach focuses on potential cancer-specific interactions reflecting higher-order relationships between miRNAs and mRNAs from expression profiles. The constructed miRNA-mRNA interaction networks show oncogenic or tumor suppression characteristics, which are known to be directly associated with prostate cancer progression. Therefore, the hypergraph-based model can assist hypothesis formulation for the molecular pathogenesis of cancer.