Essential Role of STAT3 Signaling in Hair Follicle Homeostasis

Dominant-negative mutations associated with signal transducer and activator of transcription 3 (STAT3) signaling, which controls epithelial proliferation in various tissues, lead to atopic dermatitis in hyper IgE syndrome. This dermatitis is thought to be attributed to defects in STAT3 signaling in type 17 helper T cell　specification. However, the role of STAT3 signaling in skin epithelial cells remains unclear. We found that STAT3 signaling in keratinocytes is required to maintain skin homeostasis by negatively controlling the expression of hair follicle-specific keratin genes. These expression patterns correlated with the onset of dermatitis, which was observed in specific pathogen-free conditions but not in germ-free conditions, suggesting the involvement of Toll-like receptor-mediated inflammatory responses. Thus, our study suggests that STAT3-dependent gene expression in keratinocytes plays a critical role in maintaining the homeostasis of skin, which is constantly exposed to microorganisms.

A Targetable, Noncanonical Signal Transducer and Activator of Transcription 3 Activation Induced by the Y-Less Region of IL-22 Receptor Orchestrates Imiquimod-Induced Psoriasis-Like Dermatitis in Mice

Exacerbated IL-22 activity induces tissue inflammation and immune disorders such as psoriasis. However, because IL-22 is also essential for tissue repair and defense at barrier interfaces, targeting IL-22 activity to treat psoriasis bears the risk of deleterious effects at mucosal sites such as the gut. We previously showed in vitro that IL-22 signaling relies on IL-22 receptor alpha (IL-22Rα) Y-dependent and -independent pathways. The second depends on the C-terminal Y-less region of IL-22Rα and leads to a massive signal transducer and activator of transcription 3 (STAT3) activation. Because STAT3 activation is associated with the development of psoriasis, we hypothesized that the specific inhibition of the noncanonical STAT3 activation by the Y-less region of IL-22Rα could reduce psoriasis-like disease while leaving intact its tissue defense functions in the gut. We show that mice expressing a C-terminally truncated version of IL-22Rα (ΔCtermut/mut mice) are protected from the development of psoriasis-like dermatitis lesions induced by imiquimod to a lesser extent than Il22ra-/- mice. In contrast, only Il22ra-/- mice lose weight after Citrobacter rodentium infection. Altogether, our data suggest that specific targeting of the noncanonical STAT3 activation by IL-22 could serve to treat psoriasis-like skin inflammation without affecting IL-22‒dependent tissue repair or barrier defense at other sites.

STAT3 but Not ERK2 Is a Crucial Mediator Against Diet-Induced Obesity via VMH Neurons

Leptin plays an important role in the protection against diet-induced obesity (DIO) by its actions in ventromedial hypothalamic (VMH) neurons. However, little is known about the intracellular mechanisms involved in these effects. To assess the role of the STAT3 and ERK2 signaling in neurons that express the steroidogenic factor 1 (SF1) in the VMH in energy homeostasis, we used cre-lox technology to generate male and female mice with specific disruption of STAT3 or ERK2 in SF1 neurons of the VMH. We demonstrated that the conditional knockout of STAT3 in SF1 neurons of the VMH did not affect body weight, food intake, energy expenditure, or glucose homeostasis in animals on regular chow. However, with high-fat diet (HFD) challenge, loss of STAT3 in SF1 neurons caused a significant increase in body weight, food intake, and energy efficiency that was more remarkable in females, which also showed a decrease in energy expenditure. In contrast, deletion of ERK2 in SF1 neurons of VMH did not have any impact on energy homeostasis in both regular diet and HFD conditions. In conclusion, STAT3 but not ERK2 signaling in SF1 neurons of VMH plays a crucial role in protection against DIO in a sex-specific pattern.

Curcumin inhibits proliferation and invasion of papillary thyroid carcinoma cells by inhibiting the JAK2 / STAT3 pathway

PURPOSE

The purpose of this study was to analyze the function of curcumin to suppress the proliferative and invasive abilities of papillary thyroid carcinoma (PTC) through inhibiting the JAK2/STAT3 pathway.

METHODS

After treatment of different doses of curcumin in TPC-1 and SW1736 cells, changes in viability, clonality, cell cycle, apoptosis, wound healing and invasion were determined. Western blot analyses were performed to detect protein levels of apoptosis-associated genes, JAK2 and STAT3 in TPC-1 and SW1736 cells treated with different doses of curcumin.

RESULTS

Curcumin treatment dose-dependently reduced viability, clonality and metastatic ability in TPC-1 and SW1736 cells. After treatment of 10 μM or 20 μM curcumin, PTC cells were blocked in G2/M phase, and their apoptotic rate increased. Curcumin treatment downregulated Bcl-2 and upregulated Bax in PTC cells. In addition, curcumin treatment downregulated p-JAK2 and p-STAT3 in TPC-1 and SW1736 cells.

CONCLUSIONS

Curcumin treatment blocks PTC cells to proliferate and invade via inhibiting the JAK2/STAT3 pathway.

The miR-19b-3p-MAP2K3-STAT3 feedback loop regulates cell proliferation and invasion in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most refractory malignancies worldwide. Mitogen-activated protein kinase 3 (MAP2K3) has a contradictory role in tumor progression, and the function and expression patterns of MAP2K3 in ESCC remain to be determined. We found that MAP2K3 expression to be downregulated in ESCC, and MAP2K3 downregulation correlated with clinically poor survival. MAP2K3 inhibited ESCC cell proliferation and invasion in vitro and in vivo. MAP2K3 suppressed STAT3 expression and activation. Mechanistically, MAPSK3 interacted with MDM2 to promote STAT3 degradation via the ubiquitin-proteasome pathway. Furthermore, exosomal miR-19b-3p derived from the plasma of patients with ESCC could suppress MAP2K3 expression to promote ESCC tumorigenesis. STAT3 was found to bind to the MIR19B promoter and increased the expression of miR-19b-3p in ESCC cells. In summary, our results demonstrated that the miR-19b-3p-MAP2K3-STAT3 feedback loop regulates ESCC tumorigenesis and elucidates the potential of therapeutically targeting this pathway in ESCC.

The JAK Inhibitor Tofacitinib Rescues Intestinal Barrier Defects Caused by Disrupted Epithelial-macrophage Interactions

BACKGROUND AND AIMS

Loss-of-function variants in protein tyrosine phosphatase non-receptor type-2 [PTPN2] promote susceptibility to inflammatory bowel diseases [IBD]. PTPN2 regulates Janus-kinase [JAK] and signal transducer and activator of transcription [STAT] signalling, while protecting the intestinal epithelium from inflammation-induced barrier disruption. The pan-JAK inhibitor tofacitinib is approved to treat ulcerative colitis, but its effects on intestinal epithelial cell-macrophage interactions and on barrier properties are unknown. We aimed to determine if tofacitinib can rescue disrupted epithelial-macrophage interaction and barrier function upon loss of PTPN2.

METHODS

Human Caco-2BBe intestinal epithelial cells [IECs] and THP-1 macrophages expressing control or PTPN2-specific shRNA were co-cultured with tofacitinib or vehicle. Transepithelial electrical resistance and 4 kDa fluorescein-dextran flux were measured to assess barrier function. Ptpn2fl/fl and Ptpn2-LysMCre mice, which lack Ptpn2 in myeloid cells, were treated orally with tofacitinib citrate twice daily to assess the in vivo effect on the intestinal epithelial barrier. Colitis was induced via administration of 1.5% dextran sulphate sodium [DSS] in drinking water.

RESULTS

Tofacitinib corrected compromised barrier function upon PTPN2 loss in macrophages and/or IECs via normalisation of: [i] tight junction protein expression; [ii] excessive STAT3 signalling; and [iii] IL-6 and IL-22 secretion. In Ptpn2-LysMCre mice, tofacitinib reduced colonic pro-inflammatory macrophages, corrected underlying permeability defects, and prevented the increased susceptibility to DSS colitis.

CONCLUSIONS

PTPN2 loss in IECs or macrophages compromises IEC-macrophage interactions and reduces epithelial barrier integrity. Both of these events were corrected by tofacitinib in vitro and in vivo. Tofacitinib may have greater therapeutic efficacy in IBD patients harbouring PTPN2 loss-of-function mutations.

IL-6 promotes MYC-induced B cell lymphomagenesis independent of STAT3

The inflammatory cytokine IL-6 is known to play a causal role in the promotion of cancer, although the underlying mechanisms remain to be completely understood. Interplay between endogenous and environmental cues determines the fate of cancer development. The Eμ-myc transgenic mouse expresses elevated levels of c-Myc in the B cell lineage and develops B cell lymphomas with associated mutations in p53 or other genes linked to apoptosis. We generated Eμ-myc mice that either lacked the IL-6 gene, or lacked the STAT3 gene specifically in B cells to determine the role of the IL-6/JAK/STAT3 pathway in tumor development. Using the Eμ-myc lymphoma mouse model, we demonstrate that IL-6 is a critical tumor promoter during early stages of B cell lymphomagenesis. IL-6 is shown to inhibit the expression of tumor suppressors, notably BIM and PTEN, and this may contribute to advancing MYC-driven B cell tumorigenesis. Several miRNAs known to target BIM and PTEN are upregulated by IL-6 and likely lead to the stable suppression of pro-apoptotic pathways early during the tumorigenic process. STAT3, a classical downstream effector of IL-6, appears dispensable for Eμ-myc driven lymphomagenesis. We conclude that the growth-promoting and anti-apoptotic mechanisms activated by IL-6 are critically involved in Eμ-myc driven tumor initiation and progression, but the B cell intrinsic expression of STAT3 is not required.

Control of adipogenic commitment by a STAT3-VSTM2A axis

White adipose tissue (WAT) is a dynamic organ that plays crucial roles in controlling metabolic homeostasis. During development and periods of energy excess, adipose progenitors are recruited and differentiate into adipocytes to promote lipid storage capability. The identity of adipose progenitors and the signals that promote their recruitment are still incompletely characterized. We have recently identified V-set and transmembrane domain-containing protein 2A (VSTM2A) as a novel protein enriched in preadipocytes that amplifies adipogenic commitment. Despite the emerging role of VSTM2A in promoting adipogenesis, the molecular mechanisms regulating Vstm2a expression in preadipocytes are still unknown. To define the molecular mechanisms controlling Vstm2a expression, we have treated preadipocytes with an array of compounds capable of modulating established regulators of adipogenesis. Here, we report that Vstm2a expression is positively regulated by PI3K/mTOR and cAMP-dependent signaling pathways and repressed by the MAPK pathway and the glucocorticoid receptor. By integrating the impact of all the molecules tested, we identified signal transducer and activator of transcription 3 (STAT3) as a novel downstream transcription factor affecting Vstm2a expression. We show that activation of STAT3 increased Vstm2a expression, whereas its inhibition repressed this process. In mice, we found that STAT3 phosphorylation is elevated in the early phases of WAT development, an effect that strongly associates with Vstm2a expression. Our findings identify STAT3 as a key transcription factor regulating Vstm2a expression in preadipocytes.NEW & NOTEWORTHY cAMP-dependent and PI3K-mTOR signaling pathways promote the expression of Vstm2a. STAT3 is a key transcription factor that controls Vstm2a expression in preadipocytes. STAT3 is activated in the early phases of WAT development, an effect that strongly associates with Vstm2a expression.

Impact of Selected Signaling Proteins on SNAIL 1 and SNAIL 2 Expression in Ovarian Cancer Cell Lines in Relation to Cells' Cisplatin Resistance and EMT Markers Level

It has been increasingly recognized that SNAIL1 and SNAIL2, as major EMT-inducers, might also be involved in drug resistance of cancer cells. We sought to determine a relation between SNAIL1/2, E-cadherin and N-cadherin expression, as well as ovarian cancer cells’ resistance to cisplatin and EMT markers’ level. Thus, four ovarian cancer cell lines, were used: A2780, A2780cis, SK-OV-3 and OVCAR-3. We assessed the impact of ERK1/2, AKT and STAT3 proteins (chosen by the profiling activity of over 40 signaling proteins) on SNAIL1/2 expression, along with E-cadherin and N-cadherin levels. We showed that expression of SNAIL1 and N-cadherin are the highest in cisplatin-resistant A2780cis and SK-OV-3 cells, while high SNAIL2 and E-cadherin levels were observed in cisplatin-sensitive A2780 cells. The highest E-cadherin level was noticed in OVCAR-3 cells. SNAIL1/2 expression was dependent on ERK1/2 activity in cisplatin-resistant and potentially invasive SK-OV-3 and OVCAR-3 cells. STAT-3 regulates expression of SNAIL1/2 and leads to the so-called “cadherin switch” in cancer cells, independently of their chemoresistance. In conclusion, SNAIL1, but not SNAIL2, seems to be involved in ovarian cancer cells’ cisplatin resistance. STAT3 is a universal factor determining the expression of SNAIL1/2 in ovarian cancer cells regardless of their chemoresitance or invasive capabilities.

Stat3 oxidation-dependent regulation of gene expression impacts on developmental processes and involves cooperation with Hif-1α

Reactive oxygen species are bona fide intracellular second messengers that influence cell metabolism and aging by mechanisms that are incompletely resolved. Mitochondria generate superoxide that is dis-mutated to hydrogen peroxide, which in turn oxidises cysteine-based enzymes such as phosphatases, peroxiredoxins and redox-sensitive transcription factors to modulate their activity. Signal Transducer and Activator of Transcription 3 (Stat3) has been shown to participate in an oxidative relay with peroxiredoxin II but the impact of Stat3 oxidation on target gene expression and its biological consequences remain to be established. Thus, we created murine embryonic fibroblasts (MEFs) that express either WT-Stat3 or a redox-insensitive mutant of Stat3 (Stat3-C3S). The Stat3-C3S cells differed from WT-Stat3 cells in morphology, proliferation and resistance to oxidative stress; in response to cytokine stimulation, they displayed elevated Stat3 tyrosine phosphorylation and Socs3 expression, implying that Stat3-C3S is insensitive to oxidative inhibition. Comparative analysis of global gene expression in WT-Stat3 and Stat3-C3S cells revealed differential expression (DE) of genes both under basal conditions and during oxidative stress. Using differential gene regulation pattern analysis, we identified 199 genes clustered into 10 distinct patterns that were selectively responsive to Stat3 oxidation. GO term analysis identified down-regulated genes to be enriched for tissue/organ development and morphogenesis and up-regulated genes to be enriched for cell-cell adhesion, immune responses and transport related processes. Although most DE gene promoters contain consensus Stat3 inducible elements (SIEs), our chromatin immunoprecipitation (ChIP) and ChIP-seq analyses did not detect Stat3 binding at these sites in control or oxidant-stimulated cells, suggesting that oxidised Stat3 regulates these genes indirectly. Our further computational analysis revealed enrichment of hypoxia response elements (HREs) within DE gene promoters, implying a role for Hif-1. Experimental validation revealed that efficient stabilisation of Hif-1α in response to oxidative stress or hypoxia required an oxidation-competent Stat3 and that depletion of Hif-1α suppressed the inducible expression of Kcnb1, a representative DE gene. Our data suggest that Stat3 and Hif-1α cooperate to regulate genes involved in immune functions and developmental processes in response to oxidative stress.

Redox Regulation of STAT1 and STAT3 Signaling

STAT1 and STAT3 are nuclear transcription factors that regulate genes involved in cell cycle, cell survival and immune response. The cross-talk between these signaling pathways determines how cells integrate the environmental signals received ultimately translating them in transcriptional regulation of specific sets of genes. Despite being activated downstream of common cytokine and growth factors, STAT1 and STAT3 play essentially antagonistic roles and the disruption of their balance directs cells from survival to apoptotic cell death or from inflammatory to anti-inflammatory responses. Different mechanisms are proposed to explain this yin-yang relationship. Considering the redox aspect of STATs proteins, this review attempts to summarize the current knowledge of redox regulation of STAT1 and STAT3 signaling focusing the attention on the post-translational modifications that affect their activity.

The loss of STAT3 in mature osteoclasts has detrimental effects on bone structure

Signal Transducer and Activator of Transcription 3 (STAT3) has recently been shown to be involved in bone development and has been implicated in bone diseases, such as Job’s Syndrome. Bone growth and changes have been known for many years to differ between sexes with male bones tending to have higher bone mass than female bones and older females tending to lose bone mass at faster rates than older males. Previous studies using conditional knock mice with Stat3 specifically deleted from the osteoblasts showed both sexes exhibited decreased bone mineral density (BMD) and strength. Using the Cre-Lox system with Cathepsin K promotor driving Cre to target the deletion of the Stat3 gene in mature osteoclasts (STAT3-cKO mice), we observed that 8-week old STAT3-cKO female femurs exhibited significantly lower BMD and bone mineral content (BMC) compared to littermate control (CN) females. There were no differences in BMD and BMC observed between male knock-out and male CN femurs. However, micro-computed tomography (μCT) analysis showed that both male and female STAT3-cKO mice had significant decreases in bone volume/tissue volume (BV/TV). Bone histomorphometry analysis of the distal femur, further revealed a decrease in bone formation rate and mineralizing surface/bone surface (MS/BS) with a significant decrease in osteoclast surface in female, but not male, STAT3-cKO mice. Profiling gene expression in an osteoclastic cell line with a knockdown of STAT3 showed an upregulation of a number of genes that are directly regulated by estrogen receptors. These data collectively suggest that regulation of STAT3 differs in male and female osteoclasts and that inactivation of STAT3 in osteoclasts affects bone turnover more in females than males, demonstrating the complicated nature of STAT3 signaling pathways in osteoclastogenesis. Drugs targeting the STAT3 pathway may be used for treatment of diseases such as Job’s Syndrome and osteoporosis.

Role of STAT3 signaling pathway in breast cancer

Breast cancer has grown to be the second leading cause of cancer-related deaths in women. Only a few treatment options are available for breast cancer due to the widespread occurrence of chemoresistance, which emphasizes the need to discover and develop new methods to treat this disease. Signal transducer and activator of transcription 3 (STAT3) is an early tumor diagnostic marker and is known to promote breast cancer malignancy. Recent clinical and preclinical data indicate the involvement of overexpressed and constitutively activated STAT3 in the progression, proliferation, metastasis and chemoresistance of breast cancer. Moreover, new pathways comprised of upstream regulators and downstream targets of STAT3 have been discovered. In addition, small molecule inhibitors targeting STAT3 activation have been found to be efficient for therapeutic treatment of breast cancer. This systematic review discusses the advances in the discovery of the STAT3 pathways and drugs targeting STAT3 in breast cancer. Video abstract.

HCT116 colorectal liver metastases exacerbate muscle wasting in a mouse model for the study of colorectal cancer cachexia

Colorectal cancer (CRC) is often accompanied by formation of liver metastases (LM) and skeletal muscle wasting, i.e. cachexia. Despite affecting the majority of CRC patients, cachexia remains underserved, understudied and uncured. Animal models for the study of CRC-induced cachexia, in particular models containing LM, are sparse; therefore, we aimed to characterize two new models of CRC cachexia. Male NSG mice were injected subcutaneously (HCT116) or intrasplenically (mHCT116) with human HCT116 CRC tumor cells to disseminate LM, whereas experimental controls received saline (n=5-8/group). Tumor growth was accompanied by loss of skeletal muscle mass (HCT116: -20%; mHCT116: -31%; quadriceps muscle) and strength (HCT116: -20%; mHCT116: -27%), with worsened loss of skeletal muscle mass in mHCT116 compared with HCT116 (gastrocnemius: -19%; tibialis anterior: -22%; quadriceps: -21%). Molecular analyses revealed elevated protein ubiquitination in HCT116, whereas mHCT116 also displayed elevated Murf1 and atrogin-1 expression, along with reduced mitochondrial proteins PGC1α, OPA1, mitofusin 2 and cytochrome C. Further, elevated IL6 levels were found in the blood of mHCT116 hosts, which was associated with higher phosphorylation of STAT3 in skeletal muscle. To clarify whether STAT3 was a main player in muscle wasting in this model, HCT116 cells were co-cultured with C2C12 myotubes. Marked myotube atrophy (-53%) was observed, along with elevated phospho-STAT3 levels (+149%). Conversely, inhibition of STAT3 signaling by means of a JAK/STAT3 inhibitor was sufficient to rescue myotube atrophy induced by HCT116 cells (+55%). Overall, our results indicate that the formation of LM exacerbates cachectic phenotype and associated skeletal muscle molecular alterations in HCT116 tumor hosts.

Type I interferon limits mast cell-mediated anaphylaxis by controlling secretory granule homeostasis

Type I interferon (IFN-I) is a family of multifunctional cytokines that modulate the innate and adaptive immunity and are used to treat mastocytosis. Although IFN-I is known to suppress mast cell function, including histamine release, the mechanisms behind its effects on mast cells have been poorly understood. We here investigated IFN-I’s action on mast cells using interferon-α/β receptor subunit 1 (Ifnar1)-deficient mice, which lack a functional IFN-I receptor complex, and revealed that IFN-I in the steady state is critical for mast cell homeostasis, the disruption of which is centrally involved in systemic anaphylaxis. Ifnar1-deficient mice showed exacerbated systemic anaphylaxis after sensitization, which was associated with increased histamine in the circulation, even though the mast cell numbers and high affinity immunoglobulin E receptor (FcεRI) expression levels were similar between Ifnar1-deficient and wild-type (WT) mice. Ifnar1-deficient mast cells showed increased secretory granule synthesis and exocytosis, which probably involved the increased transcription of Tfeb. Signal transducer and activator of transcription 1(Stat1) and Stat2 were unexpectedly insufficient to mediate these IFN-I functions, and instead, Stat3 played a critical role in a redundant manner with Stat1. Our findings revealed a novel regulation mechanism of mast cell homeostasis, in which IFN-I controls lysosome-related organelle biogenesis.

This study reveals a novel role for type I interferon in mast cell homeostasis; spontaneous type I interferon signaling regulates the biogenesis of secretory granules and maturation of mast cells via STAT1 and STAT3, and limits the onset of systemic anaphylaxis.

Hispolon induces apoptosis against prostate DU145 cancer cells via modulation of mitochondrial and STAT3 pathways

Hispolon, a bioactive polyphenolic entity extracted from Phellinus linteus, possesses anticancer, antiinflammatory and anti-oxidant properties. Despite the reported therapeutic effects of this natural chemical entity, inhibitory potential of hispolon towards prostate carcinoma DU145 cells and mechanism of its action are yet to be explicated. Deregulated STAT3 pathway performs multifaceted functions in facilitating the development of cancer. Here, we have investigated the mechanism of hispolon by which it exerts its anticancer effects in DU145 cells and whether its anticancer activity is mediated by modulation of STAT3. Our outcomes show that hispolon significantly halted the multiplication of DU145 cells as well as arrested cell cycle at S phase. S phase arrest induced by hispolon was associated with downregulation of cyclin B1, cyclin D1 and CDK4 while up-regulation of p21. Moreover, hispolon treatment leads towards induction of apoptosis in a dose-dependent mode in DU145 cells. Hispolon induced modulation of Bcl-2 family proteins lead towards loss of MMP allowing the discharge of cytochrome c from mitochondrial porin channels which triggered the cascade of caspases ultimately causing cellular death. We further investigated the role of hispolon in mediating deregulated STAT3 pathways in DU145 cells. Hispolon has potential to downregulate the p-STAT3 expression with no effect on total STAT3. Contemporaneously, these results represent that hispolon's anticancer mechanism of action proceeds via downregulating the phosphorylation of STAT3 and induction of apoptosis via mitochondrial pathway.

Stem cell persistence in CML is mediated by extrinsically activated JAK1-STAT3 signaling

Tyrosine kinase inhibitor (TKI) therapy effectively blocks oncogenic Bcr-Abl signaling and induces molecular remission in the majority of CML patients. However, the disease-driving stem cell population is not fully targeted by TKI therapy in the majority of patients, and leukemic stem cells (LSCs) capable of re-inducing the disease can persist. In TKI-resistant CML, STAT3 inhibition was previously shown to reduce malignant cell survival. Here, we show therapy-resistant cell-extrinsic STAT3 activation in TKI-sensitive CML cells, using cell lines, HoxB8-immortalized murine BM cells, and primary human stem cells. Moreover, we identified JAK1 but not JAK2 as the STAT3-activating kinase by applying JAK1/2 selective inhibitors and genetic inactivation. Employing an IL-6-blocking peptide, we identified IL-6 as a mediator of STAT3 activation. Combined inhibition of Bcr-Abl and JAK1 further reduced CFUs from murine CML BM, human CML MNCs, as well as CD34⁺ CML cells, and similarly decreased LT-HSCs in a transgenic CML mouse model. In line with these observations, proliferation of human CML CD34⁺ cells was strongly reduced upon combined Bcr-Abl and JAK1 inhibition. Remarkably, the combinatory therapy significantly induced apoptosis even in quiescent LSCs. Our findings suggest JAK1 as a potential therapeutic target for curative CML therapies.

NF-κB RelA Is Required for Hepatoprotection during Pneumonia and Sepsis

Pneumonia and sepsis are distinct but integrally linked public health concerns. The hepatic acute-phase response (APR), which is largely dependent on transcription factors NF-κB RelA and STAT3, is a hallmark of these pathologies and other injurious conditions. Inactivation of the APR can promote liver injury, a frequently observed organ dysfunction during sepsis. However, whether or how the acute-phase changes promote liver tissue resilience during infections is unclear. To determine the hepatoprotective role of the hepatic APR, we utilized mice bearing hepatocyte-specific deletions of either RelA or STAT3. Mice were challenged intratracheally (i.t.), intravenously (i.v.), or intraperitoneally (i.p.) with Escherichia coli, Klebsiella pneumoniae, Streptococcus pneumoniae, lipopolysaccharide (LPS), or alpha-galactosylceramide (αGalCer) to induce pneumonia, sepsis, or NKT cell activation. Liver injury was observed in RelA-null (hepRelAΔ/Δ) mice but not STAT3-null (hepSTAT3Δ/Δ) mice during pneumonia. The absence of RelA resulted in hepatotoxicity across several models of pneumonia, sepsis, and NKT cell activation. Injury was associated with increased levels of activated caspase-3 and -8 and substantial alteration of the hepatic transcriptome. Hepatotoxicity in the absence of RelA could be reversed by neutralization of tumor necrosis factor alpha (TNF-α). These results indicate the requirement of RelA-dependent inducible hepatoprotection during pneumonia and sepsis. Further, the results demonstrate that RelA-dependent gene programs are critical for maintaining liver homeostasis against TNF-α-driven immunotoxicity.

Expression of STAT3-regulated genes in circulating CD4+ T cells discriminates rheumatoid arthritis independently of clinical parameters in early arthritis

OBJECTIVES

Dysregulated signal transduction and activator of transcription-3 (STAT3) signalling in CD4+ T cells has been proposed as an early pathophysiological event in RA. We sought further evidence for this observation, and to determine its clinical relevance.

METHODS

Microarray technology was used to measure gene expression in purified peripheral blood CD4+ T cells from treatment-naïve RA patients and disease controls newly recruited from an early arthritis clinic. Analysis focused on 12 previously proposed transcripts, and concurrent STAT3 pathway activation was determined in the same cells by flow cytometry. A pooled analysis of previous and current gene expression findings incorporated detailed clinical parameters and employed multivariate analysis.

RESULTS

In an independent cohort of 161 patients, expression of 11 of 12 proposed signature genes differed significantly between RA patients and controls, robustly validating the earlier findings. Differential regulation was most pronounced for the STAT3 target genes PIM1, BCL3 and SOCS3 (>1.3-fold difference; P < 0.005), each of whose expression correlated strongly with paired intracellular phospho-STAT3. In a meta-analysis of 279 patients the same three genes accounted for the majority of the signature's ability to discriminate RA patients, which was found to be independent of age, joint involvement or acute phase response.

CONCLUSION

The STAT3-mediated dysregulation of BCL3, SOCS3 and PIM1 in circulating CD4+ T cells is a discriminatory feature of early RA that occurs independently of acute phase response. The mechanistic and functional implications of this observation at a cellular level warrant clarification.

JAK/STAT3 and NF-κB Signaling Pathways Regulate Cancer Stem-Cell Properties in Anaplastic Thyroid Cancer Cells

Background: Anaplastic thyroid carcinoma (ATC) is one of the most aggressive and refractory cancers, and a therapy with a new concept needs to be developed. Recently, research on cancer stem cells (CSCs) has progressed, and CSCs have been suggested to be responsible for metastasis, recurrence, and therapy resistance. In ATC-CSCs, aldehyde dehydrogenase (ALDH) activity is the most reliable marker to enrich CSCs. However, it is just a marker and is not involved in CSC properties. The present study therefore aimed to identify key signaling pathways specific for ATC-CSCs. Methods: A small interfering RNA library targeting 719 kinases was used in a sphere formation assay and cell survival assay using ATC cell lines to select target molecules specific for CSC properties. The functions of the selected candidates were confirmed by sphere formation, cell survival, soft agar, and nude mice xenograft assays using small compound inhibitors. Results: The study focused on PDGFR, JAK, and PIM, whose small interfering RNAs had a higher inhibitory effect on sphere formation, as well as a lower or no effect on regular cell growth in both FRO and KTC3 cells. Next, inhibitors of PDGFR, JAK, STAT3, PIM and NF-κB were used, and all of them successfully suppressed sphere formation in a dose-dependent manner but not regular cell growth, confirming the screening results. Inhibition of the JAK/STAT3 and NF-κB pathways also reduced anchorage-independent growth in soft agar and tumor growth in nude mice. Conclusions: These results suggest that JAK/STAT3 and NF-κB signals play important roles in ATC-CSCs. Targeting these signaling pathways may be a promising approach to treat ATC.

Sphk1/S1P/S1PR1 Signaling is Involved in the Development of Autoimmune Thyroiditis in Patients and NOD.H-2h4 Mice

Background: There is growing evidence that sphingosine-1-phosphate (S1P), a pleiotropic bioactive sphingolipid metabolite synthesized intracellularly by two closely related sphingosine kinases (SphKs), SphK1 and SphK2, is involved in inflammation. However, the role of SphKs/S1P/S1P receptors (S1PRs) in autoimmune thyroiditis (AIT) has not been studied to date. Methods: This study examined whether SphK1/S1P/S1PR1 signaling is aberrantly altered in thyroid tissues and serum of both AIT patients and a spontaneously autoimmune thyroiditis (SAT) mouse model. Murine CD4+T cells were employed to further investigate the downstream signaling of SphK1/S1P/S1PR1. Furthermore, a total of 102 NOD.H-2^h4 mice, randomly divided into different groups, were used to investigate the therapeutic effect of S1PR1 blockade and its potential mechanism. Results: We found that components of the SphK1/S1P/S1PR1 pathway were abnormally expressed in patients with Hashimoto thyroiditis and in a SAT mouse model. In addition, S1P could activate signal transducer and activator of transcription 3 (STAT3) through S1PR1 and its downstream signaling pathways in CD4+T cells of NOD.H-2^h4 mice. Furthermore, an in vivo study demonstrated that blocking S1PR1 by FTY720 administration could reduce the incidence and severity of thyroiditis and goiter in SAT mice in a time-dependent manner. The proportions of STAT3-related and inflammation-related cell subtypes, such as T helper 1, T helper 17, and follicular T helper cells, were elevated in the SAT group when compared to the control group, and these cell subtypes decreased after FTY720 administration. Furthermore, the downstream inflammatory cytokines of STAT3 were also downregulated after FTY720 administration. Conclusion: The present study shows that blocking Sphk1/S1P/S1PR1 signaling can ameliorate the severity of AIT, providing evidence of a promising therapeutic target for AIT.

The Stat3-Fam3a axis promotes muscle stem cell myogenic lineage progression by inducing mitochondrial respiration

Metabolic reprogramming is an active regulator of stem cell fate choices, and successful stem cell differentiation in different compartments requires the induction of oxidative phosphorylation. However, the mechanisms that promote mitochondrial respiration during stem cell differentiation are poorly understood. Here we demonstrate that Stat3 promotes muscle stem cell myogenic lineage progression by stimulating mitochondrial respiration in mice. We identify Fam3a, a cytokine-like protein, as a major Stat3 downstream effector in muscle stem cells. We demonstrate that Fam3a is required for muscle stem cell commitment and skeletal muscle development. We show that myogenic cells secrete Fam3a, and exposure of Stat3-ablated muscle stem cells to recombinant Fam3a in vitro and in vivo rescues their defects in mitochondrial respiration and myogenic commitment. Together, these findings indicate that Fam3a is a Stat3-regulated secreted factor that promotes muscle stem cell oxidative metabolism and differentiation, and suggests that Fam3a is a potential tool to modulate cell fate choices.

The role of STAT3 protein as a prognostic factor in the clear cell renal carcinoma. Systematic review

CONTEXT AND OBJECTIVE

There have been significant advances in the knowledge of renal carcinogenesis n the last years. Nowadays, renal tumors are classified according to their genetic profile and specific treatments based on the identification of therapeutic targets have also been developed. However, no prognostic markers have yet been identified. The aim of this review is to analyse literature that has evaluated the expression of the STAT3 protein as a molecular marker in clear cell renal carcinoma (ccRCC).

EVIDENCE ACQUISITION

In January 2018 a systematic review was conducted in Pubmed, Cochrane library and Sciencedirect databases, from papers published from 1990. Search terms were"renal cell carcinoma"and"STAT3"or"STAT-3"and"prognostic factor. Following the principles of the PRISMA declaration and the PICO selection strategy, original articles with series of patients diagnosed with localized or metastatic ccRCC, and where the activity of STAT3 is analysed as a prognostic marker, were selected. A total of 132 publications were identified, of which 10 were finally revised, for they met the inclusion criteria.

EVIDENCE SYNTHESIS

STAT3 activation (phosphorylation) through Ser727 is important during ccRCC development and progression. PSTAT3 expression seems to be a prognostic marker and an antiangiogenic-resistance marker in metastatic patients. There is little evidence as prognostic marker in patients with localized disease.

CONCLUSIONS

STAT3 (Ser 727) expression in the nucleus of the ccRCC cells can be a prognostic marker and an antiangiogenic-resistance marker. Current scientific evidence is limited and more studies are needed to demonstrate its usefulness.

Role of STAT3 in skin fibrosis and transforming growth factor beta signalling

Objective

SSc is an autoimmune disease characterized by progressive fibrosis of the skin and internal organs. IL-6 and related cytokines that signal through STAT3 have been implicated in the pathogenesis of SSc and mouse models of fibrosis. The aim of this study was to investigate the efficacy of inhibiting STAT3 in the development of fibrosis in two mouse models of skin fibrosis.

Methods

Biopsy samples of skin from SSc patients and healthy control subjects were used to determine the expression pattern of phosphotyrosyl (pY705)-STAT3. C188-9, a small molecule inhibitor of STAT3, was used to treat fibrosis in the bleomycin-induced fibrosis model and Tsk-1 mice. In vitro studies were performed to determine the extent to which STAT3 regulates the fibrotic phenotype of dermal fibroblasts.

Results

Increased STAT3 and pY705-STAT3 was observed in SSc skin biopsies and in both mouse models of SSc. STAT3 inhibition with C188-9 resulted in attenuated skin fibrosis, myofibroblast accumulation, pro-fibrotic gene expression and collagen deposition in both mouse models of skin fibrosis. C188-9 decreased in vitro dermal fibroblast production of fibrotic genes induced by IL-6 trans-signalling and TGF-β. Finally, TGF-β induced phosphotyrosylation of STAT3 in a SMAD3-dependent manner.

Conclusion

STAT3 inhibition decreases dermal fibrosis in two models of SSc. STAT3 regulates dermal fibroblasts function in vitro and can be activated by TGF-β. These data suggest that STAT3 is a potential therapeutic target for dermal fibrosis in diseases such as SSc.

Therapeutic Ablation of Gain-of-Function Mutant p53 in Colorectal Cancer Inhibits Stat3-Mediated Tumor Growth and Invasion

Over half of colorectal cancers (CRCs) harbor TP53 missense mutations (mutp53). We show that the most common mutp53 allele R248Q (p53^Q) exerts gain of function (GOF) and creates tumor dependence in mouse CRC models. mutp53 protein binds Stat3 and enhances activating Stat3 phosphorylation by displacing the phosphatase SHP2. Ablation of the p53^Q allele suppressed Jak2/Stat3 signaling, growth, and invasiveness of established, mutp53-driven tumors. Treating tumor-bearing mice with an HSP90 inhibitor suppressed mutp53 levels and tumor growth. Importantly, human CRCs with stabilized mutp53 exhibit enhanced Jak2/Stat3 signaling and are associated with poorer patient survival. Cancers with TP53^R248Q/W are associated with a higher patient death risk than are those having nonR248 mutp53. These findings identify GOF mutp53 as a therapeutic target in CRC.

A New Perspective: Mitochondrial Stat3 as a Regulator for Lymphocyte Function

Stat3 as a transcription factor regulating gene expression in lymphocytes during the immune response is well known. However, since the pioneering studies discovering the presence of Stat3 in mitochondria and its role in regulating mitochondrial metabolism, only a few studies have investigated this non-conventional function of Stat3 in lymphocytes. From this perspective, we review what is known about Stat3 as a transcription factor and what is known and unknown about mitochondrial Stat3 (mitoStat3) in lymphocytes. We also provide a framework to consider how some of the functions previously assigned to Stat3 as regulator of gene transcription could be mediated by mitoStat3 in lymphocytes. The goal of this review is to stimulate interest for future studies investigating mitoStat3 in the immune response that could lead to the generation of alternative pharmacological inhibitors of mitoStat3 for the treatment of chronic inflammatory diseases.

Tea Polysaccharides Inhibit Colitis-Associated Colorectal Cancer via Interleukin-6/STAT3 Pathway

The interleukin-6 (IL-6)/signal transducer and activator of transcription (STAT)-3 signaling pathway regulates proliferation and survival of intestinal epithelial cells and has profound impact on the tumorigenesis of colitis-associated cancer (CAC). Tea polysaccharides (TPS) are the major nutraceutical component isolated from tea-leaves and are known to possess antioxidant, anti-inflammatory, and antitumor bioactivities. Here, we investigated the antitumor activities of TPS on CAC using the azoxymethane/dextran sulfate sodium (AOM/DSS) mouse model and IL-6-induced colorectal cancer cell line (CT26) and determined whether TPS exerted its antitumor effects through the IL-6/STAT3 pathway. Results demonstrated that TPS significantly decreased the tumor incidence, tumor size, and markedly inhibited the infiltration of pro-inflammatory cells and the secretion of pro-inflammatory cytokines via balancing cellular microenvironment. Furthermore, we found that TPS suppressed the activation of STAT3 and transcriptionally regulated the expressions of downstream genes including MMP2, cyclin Dl, survivin, and VEGF both in vivo and in vitro. Thus, it was concluded that TPS attenuated the progress of CAC via suppressing IL-6/STAT3 pathway and downstream genes' expressions, which indicated that TPS may be a hopeful antitumor agent for the prevention and treatment of colon cancer.

Role of Dysregulated Cytokine Signaling and Bacterial Triggers in the Pathogenesis of Cutaneous T-Cell Lymphoma

Cutaneous T-cell lymphoma is a heterogeneous group of lymphomas characterized by the accumulation of malignant T cells in the skin. The molecular and cellular etiology of this malignancy remains enigmatic, and what role antigenic stimulation plays in the initiation and/or progression of the disease remains to be elucidated. Deep sequencing of the tumor genome showed a highly heterogeneous landscape of genetic perturbations, and transcriptome analysis of transformed T cells further highlighted the heterogeneity of this disease. Nonetheless, using data harvested from high-throughput transcriptional profiling allowed us to develop a reliable signature of this malignancy. Focusing on a key cytokine signaling pathway previously implicated in cutaneous T-cell lymphoma pathogenesis, JAK/STAT signaling, we used conditional gene targeting to develop a fully penetrant small animal model of this disease that recapitulates many key features of mycosis fungoides, a common variant of cutaneous T-cell lymphoma. Using this mouse model, we show that T-cell receptor engagement is critical for malignant transformation of the T lymphocytes and that progression of the disease is dependent on microbiota.

MiR-221 inhibits proliferation of pancreatic cancer cells via down regulation of SOCS3

OBJECTIVE

The over-activation of Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway induced by cytokines are closely correlated with tumorigenesis. Suppressor of cytokine signaling 3 (SOCS3) serves as a negative regulator for JAK-STAT, and its down-regulation is involved in the oncogenesis of pancreatic cancer. We aimed at investigating the effect of miR-221 on the expression and proliferation, cycle and apoptosis of pancreatic cancer cells and determine the related mechanism.

PATIENTS AND METHODS

Dual luciferase reporter gene assay was used to analyze the regulation between miR-221 and SOCS3. The expressions of miR-221, SOCS3, p-JAK and p-STAT3 in normal human pancreatic epithelial cell HPDE6-C7 and pancreatic cancer cell PANC-1 were quantified by qPCR and Western blot. Flow cytometry was used to identify cell cycle and proliferation. In vitro cultured PANC-1 cells were transfected with miR-221 inhibitor or pIRES2-SOCS3. The expressions of miR-221, SOCS3, p-JAK and p-STAT3, along with the cell proliferation or apoptosis, were compared.

RESULTS

Bioinformatics analysis showed the existence of binding site between miR-221 and 3'-UTR of SOCS3 mRNA. Dual luciferase gene reporter assay confirmed the targeted regulation between miR-221 and SOCS3. Compared to HPDE6-C7 cells, higher levels of miR-221, p-JAK and p-STAT3 expression, and lower expression of SOCS3, were found in PANC-1 cells, along with the increase of cell proliferation. Transfection of miR-221 inhibitor or pIRES2-SOCS3 remarkably enhanced SOCS3 expression, inhibited the levels of p-JAK and p-STAT3 expression, and impeded the proliferation of PANC-1 cells.

CONCLUSIONS

MiR-221 decreases proliferation potency of PANC-1 cells and affects JAK-STAT3 signaling pathway via inhibiting SOCS3.

Inhibition of two gastric cancer cell lines induced by fucoxanthin involves downregulation of Mcl-1 and STAT3

Fucoxanthin is a natural carotenoid that had never been previously demonstrated to have anti-tumor effect on human gastric adenocarcinoma SGC-7901 or BGC-823 cells. Here it was found to inhibit proliferation and induce apoptosis through JAK/STAT signal pathway in these cells; the mechanism by which this occurred was investigated. We find that fucoxanthin significantly increased the number of apoptotic cells by propidium iodide (PI) dye staining and flow cytometry. Fucoxanthin (50 or 75 μM) induced SGC-7901 cells cycle arrest at S phase, while BGC-823 cells arrest at G2/M phase. RT-PCR and western blot analysis revealed that the expressions of Mcl-1, STAT3 and p-STAT3 were obviously decreased by fucoxanthin in a dose-dependent manner. Synthetic siRNA targeting Mcl-1 was transfected into cells which had no effect on expressions of STAT3. After pretreatment with AG490 (50 μM) which led to blocking of the JAK/STAT signal pathway, the reductive expressions of Mcl-1, STAT3 and p-STAT3 caused by fucoxanthin were inhibited. This is the first analysis of effects on SGC-7901 and BGC-823 cells by fucoxanthin. Fucoxanthin can induce cell-cycle arrest and apoptosis in these cells. These effects involved downregulation of Mcl-1, STAT3 and p-STAT3. This work is significant for better understanding of mechanisms leading to human gastric adenocarcinoma formation and informing exploitation of anti-tumor marine drug, and for providing Mcl-1 and STAT3 as potential therapeutic targets for gastric adenocarcinoma.

Silibinin sensitizes chemo-resistant breast cancer cells to chemotherapy

CONTEXT

Multiple drug resistance is the major obstacle to conventional chemotherapy. Silibinin, a nontoxic naturally occurring compound, has anticancer activity and can increase the cytotoxic effects of chemotherapy in various cancer models.

OBJECTIVE

To evaluate the effects of silibinin on enhancing the sensitivity of chemo-resistant human breast cell lines to doxorubicin (DOX) and paclitaxel (PAC).

MATERIALS AND METHODS

The cells were treated with silibinin (at 50 to 600 μM concentrations) and/or chemo drugs for 24 and 48 h, then cell viability and changes in oncogenic proteins were determined by MTT assay and Western blotting/RT-PCR, respectively. Flow cytometry was used to study apoptosis in the cells receiving different treatments. The antitumorigenic effects of silibinin (at 200 to 400 μM concentration) were evaluated by mammosphere assay.

RESULTS

Silibinin exerted significant growth inhibitory effects with IC₅₀ ranging from 200 to 570 μM in different cell lines. Treatment of DOX-resistant MDA-MB-435 cells with silibinin at 200 μM reduced DOX IC₅₀ from 71 to 10 μg/mL and significantly suppressed the key oncogenic pathways including STAT3, AKT, and ERK in these cells. Interestingly treatment of DOX-resistant MDA-MB-435 cells with silibinin at 400 μM concentration for 48 h induced a 50% decrease in the numbers of colonies as compared with DMSO-treated cells. Treatment of PAC-resistant MCF-7 cells with silibinin at 400 μM concentration generated synergistic effects when it was used in combination with PAC at 250 nM concentration (CI = 0.81).

CONCLUSION

Silibinin sensitizes chemo-resistant cells to chemotherapeutic agents and can be useful in treating breast cancers.

(E)-2-Methoxy-4-(3-(4-methoxyphenyl) prop-1-en-1-yl) Phenol Ameliorates LPS-Mediated Memory Impairment by Inhibition of STAT3 Pathway

Alzheimer’s disease (AD) is pathologically characterized by an excessive accumulation of amyloid-beta (Aβ) fibrils within the brain. We tested the anti-inflammatory and anti-amyloidogenic effects of (E)-2-methoxy-4-(3-(4-methoxyphenyl) prop-1-en-1-yl) phenol (MMPP), a selective signal transducer and activator of transcription 3 (STAT3) inhibitor. We examined whether MMPP (5 mg/kg in drinking water for 1 month) prevents amyloidogenesis and cognitive impairment on AD model mice induced by intraperitoneal LPS (250 μg/kg daily 7 times) injections. Additionally, we investigated the anti-neuroinflammatory and anti-amyloidogenic effect of MMPP (1, 5, and 10 μg/mL) in LPS (1 μg/mL)-treated cultured astrocytes and microglial BV-2 cells. MMPP treatment reduced LPS-induced memory loss. This memory recovery effect was associated with the reduction of LPS-induced inflammatory proteins; cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) as well as activation of microglial cells and astrocytes in the brain. Furthermore, MMPP reduced LPS-induced β-secretase and Aβ generation. In in vitro study, LPS-induced expression of inflammatory proteins and amyloidogenic proteins was decreased in microglial BV-2 cells and cultured astrocytes by MMPP treatment. Moreover, MMPP treatment suppressed DNA binding activities of the activation of STAT3 in in vivo and in vitro. These results indicated that MMPP inhibits LPS-induced amyloidogenesis and neuroinflammation via inhibition of STAT3.

[Interleukin-9 promotes pancreatic cancer cell proliferation and migration via activation of STAT3 pathway]

Objective To investigate the impact of interleukin-9 (IL-9) on proliferation, invasion and migration of pancreatic cancer cells and its mechanism. Methods PANC-1 cells were cultured in vitro and treated with IL-9 at different concentrations (5, 10, 20 ng/mL) for 24 hours. The level of IL-9R mRNA was analyzed by quantitative real-time PCR. CCK-8 assay was used to test the proliferation of the cells and flow cytometry to detect the cell apoptosis. Transwell^TM assay was employed to determine the invasion and migration of PANC-1 cells. Western blotting was used to detect the STAT3 and p-STAT3 protein expression levels. After PANC-1 cells were treated with different concentrations of STAT3 pathway inhibitor AG490, followed by IL-9 treatment, the STAT3 and p-STAT3 protein expressions, as well as the proliferation of the cells were detected again. Results The level of IL-9R mRNA and the proliferation rate of PANC-1 cells were enhanced with the increase of IL-9 concentration, and the capacities of cell invasion and migration were promoted significantly. The relative protein expression of p-STAT3 increased greatly in PANC-1 cells after the treatment of IL-9, but STAT3 were not changed significantly compared with the ones without IL-9 treatment. The proliferation-promoting effect of IL-9 on AG490-pretreated PANC-1 cells was induced, and the p-STAT3 protein expression level was notably inhibited. Conclusion The activation of STAT3 pathway is strongly associated with the process that IL-9 mediates the promotion of proliferation, invasion and migration in pancreatic cancer cells.

[Effect of microRNA-155 on inflammatory response and lipid uptake of macrophages and its mechanism]

Objective To investigate the effect of microRNA-155 on inflammatory response and lipid uptake of macrophages after the cells are stimulated by ox-LDL and its potential mechanism. Methods Macrophage RAW264.7 cells were treated with 0, 25, 50 and 100 μg/mL ox-LDL for 24 hours or with 50 μg/mL ox-LDL for 0, 6, 12, 24 hours. The level of miR-155 was evaluated in all above samples through real-time quantitative PCR. In our research, RAW264.7 cells were divided into six groups: control group, ox-LDL group, ox-LDL/negative control group, ox-LDL/anti-miR-155 group, ox-LDL/shRNA negative control group and ox-LDL/PPARγ-shRNA group. Oil red O staining was used to observe lipid uptake in the cells. Filipin staining was used to evaluate the cellular uptake of ox-LDL. Cholesterol testing was performed to examine the levels of total cholesterol (TC) and free cholesterol (FC). Real-time quantitative PCR was done to detect the expressions of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6 mRNAs. According to study purpose, we explored the potential mechanisms of miR-155 inhibitor (including control group, ox-LDL group, ox-LDL/negative control group and ox-LDL/miR-155 inhibitor group), miR-155 mimic (including negative control group and miR-155 mimic group), and PPARγ shRNA (including control group, ox-LDL group, ox-LDL/shRNA negative control group and ox-LDL/PPARγ shRNA group) in ox-LDL-treated RAW264.7 cells through evaluating the expressions of p-STAT3, PPARγ, CD36 and NF-κBp65 using Western blotting. Results Ox-LDL stimulation increased the relative expression of miR-155 in a dose- and time-dependent manner. Through oil red O staining, Filipin staining, cholesterol testing and real-time PCR experiment, we found the relative absorbance, levels of TC and FC, filipin fluorescence intensity, and levels of TNF-α, IL-1β and IL-6 mRNAs were significantly lower in ox-LDL/anti-miR-155 group than in ox-LDL and ox-LDL/negative control group. Similarly, the relative absorbance, levels of TC and FC, filipin fluorescence intensity and levels of TNF-α, IL-1β and IL-6 mRNAs were significantly lower in ox-LDL/ PPARγ shRNA group than in ox-LDL group and ox-LDL/shRNA negative control group. The expressions of p-STAT3, PPARγ, CD36 and NF-κBp65 proteins were suppressed in ox-LDL/anti-miR-155 group as compared with ox-LDL group and ox-LDL/negative control group. Similarly, p-STAT3, PPARγ, CD36 and NF-κBp65 protein levels decreased in ox-LDL/PPARγ shRNA as compared with ox-LDL/vector group. Moreover, p-STAT3, PPARγ, CD36 and NF-κBp65 protein levels were higher in miR-155 mimic group than in negative control group. Conclusion Mediated by PPARγ, miR-155 induced inflammation response and lipid uptake of macrophages via STAT3/NF-κB signal pathway and CD36.

Interdependence of JAK-STAT and MAPK signaling pathways during EGF-mediated HTR-8/SVneo cell invasion

Invasion of trophoblast cells is spatio-temporally regulated by various cytokines and growth factors. In pregnancy, complications like preeclampsia, shallow invasion of trophoblast cells and low amounts of epidermal growth factor (EGF) have been reported. In the present study, regulatory mechanisms associated with EGF-mediated invasion in HTR-8/SVneo trophoblastic cells have been delineated. Treatment of HTR-8/SVneo cells with EGF (10 ng/ml) led to eight fold increase (p < 0.05) in invasion. Increased invasion of HTR-8/SVneo cells by EGF was associated with an increase in phosphorylation of ERK½. In addition, significant phosphorylation of STAT1 (ser 727) and STAT3 (both tyr 705 and ser 727 residues) was also observed, accompanied by a decrease in total STAT1. Inhibition of ERK½ phosphorylation by U0126 (10 μM) led to a significant decrease in EGF-mediated invasion with simultaneous decrease in the phosphorylated forms of STAT3 and STAT1. Decrease in total STAT1 was also reversed on inhibition of ERK½. Interestingly, inhibition of STAT3 by siRNA led to a significant decrease in EGF-mediated invasion of HTR-8/SVneo cells and phosphorylation of STAT1, but it did not have any effect on the activation of ERK½. On the other hand, inhibition of STAT1 by siRNA, also led to a significant decrease in the EGF-mediated invasion of HTR-8/SVneo cells, showed concomitant decrease in ERK½ phosphorylation and STAT3 phosphorylation at ser 727 residue. These results suggest cross-communication between ERK½ and JAK-STAT pathways during EGF-mediated increase in invasion of trophoblast cells; phosphorylation at ser 727 residue of both STAT3 and STAT1 appears to be critical.

Tonic suppression of PCAT29 by the IL-6 signaling pathway in prostate cancer: Reversal by resveratrol

Prostate cancer (PCa) is the second leading cause of cancer deaths in men. A better understanding of the molecular basis of prostate cancer proliferation and metastasis should enable development of more effective treatments. In this study we focused on the lncRNA, prostate cancer associated transcript 29 (PCAT29), a putative tumor suppressive gene. Our data show that the expression of PCAT29 was reduced in prostate cancer tumors compared to paired perinormal prostate tissues. We also observed substantially lower levels of PCAT29 in DU145 and LNCaP cells compared to normal prostate (RWPE-1) cells. IL-6, a cytokine which is elevated in prostate tumors, reduced the expression of PCAT29 in both DU145 and LNCaP cells by activating signal transducer and activator of transcription 3 (STAT3). One downstream target of STAT3 is microRNA (miR)-21, inhibition of which enhanced basal PCAT29 expression. In addition, we show that resveratrol is a potent stimulator of PCAT29 expression under basal condition and reversed the down regulation of this lncRNA by IL-6. Furthermore, we show that knock down of PCAT29 expression by siRNA in DU145 and LNCaP cells increased cell viability while increasing PCAT29 expression with resveratrol decreased cell viability. Immunohistochemistry studies showed increased levels of STAT3 and IL-6, but low levels of programmed cell death protein 4 (PDCD4), in prostate tumor epithelial cells compared to adjacent perinormal prostate epithelial cells. These data show that the IL-6/STAT3/miR-21 pathway mediates tonic suppression of PCAT29 expression and function. Inhibition of this signaling pathway by resveratrol induces PCAT29 expression and tumor suppressor function.

Regulation of the JMJD3 (KDM6B) histone demethylase in glioblastoma stem cells by STAT3

The growth factor and cytokine regulated transcription factor STAT3 is required for the self-renewal of several stem cell types including tumor stem cells from glioblastoma. Here we show that STAT3 inhibition leads to the upregulation of the histone H3K27me2/3 demethylase Jmjd3 (KDM6B), which can reverse polycomb complex-mediated repression of tissue specific genes. STAT3 binds to the Jmjd3 promoter, suggesting that Jmjd3 is a direct target of STAT3. Overexpression of Jmjd3 slows glioblastoma stem cell growth and neurosphere formation, whereas knockdown of Jmjd3 rescues the STAT3 inhibitor-induced neurosphere formation defect. Consistent with this observation, STAT3 inhibition leads to histone H3K27 demethylation of neural differentiation genes, such as Myt1, FGF21, and GDF15. These results demonstrate that the regulation of Jmjd3 by STAT3 maintains repression of differentiation specific genes and is therefore important for the maintenance of self-renewal of normal neural and glioblastoma stem cells.

Repression of Smad3 by Stat3 and c-Ski/SnoN induces gefitinib resistance in lung adenocarcinoma

Cancer-associated inflammation develops resistance to the epidermal growth-factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in non-small cell lung cancers (NSCLCs) harboring oncogenic EGFR mutations. Stat3-mediated interleukin (IL)-6 signaling and Smad-mediated transforming growth factor-β (TGF-β) signaling pathways play crucial regulatory roles in cancer-associated inflammation. However, mechanisms how these pathways regulate sensitivity and resistance to EGFR-TKI in NSCLCs remain largely undetermined. Here we show that signal transducer and activator of transcription (Stat)3 represses Smad3 in synergy with the potent negative regulators of TGF-β signaling, c-Ski and SnoN, whereby renders gefitinib-sensitive HCC827 cells resistant. We found that IL-6 signaling via phosphorylated Stat3 induced gefitinib resistance as repressing transcription of Smad3, whereas TGF-β enhanced gefitinib sensitivity as activating transcription of Smad3 in HCC827 cells with gefitinib-sensitizing EGFR mutation. Promoter analyses showed that Stat3 synergized with c-Ski/SnoN to repress Smad2/3/4-induced transcription of the Smad3 gene. Smad3 was found to be an apoptosis inducer, which upregulated pro-apoptotic genes such as caspase-3 and downregulated anti-apoptotic genes such as Bcl-2. Our results suggest that derepression of Smad3 can be a therapeutic strategy to prevent gefitinib-resistance in NSCLCs with gefitinib-sensitizing EGFR mutation.

Upregulation of MEK5 by Stat3 promotes breast cancer cell invasion and metastasis

Mitogen extracellular-signal-regulated kinase kinase 5 (MEK5) plays an important role in promoting cell proliferation and tumorigenesis. The aberrant expression of MEK5 has been reported in various malignant diseases including cancers of breast, prostate, lung, colorectal and brain. However, the function and regulation of MEK5 signaling pathway are ambiguous and remain elusive with respect to its oncogenic roles in various cancers, especially in the regulation of the initiation and progression of cancer invasion and metastasis. Ectopic expression of MEK5 or knockdown of MEK5 by shRNA with in vitro cell based models demonstrated the role of MEK5 in regulation of epithelial mesenchymal transition (EMT) and breast cancer invasion and metastasis. Here, we show that MEK5 upregulated by Stat3 promotes breast cancer cell invasion through EMT. Further study demonstrated that Stat3 could bind to promoter region of MEK5 and enhanced MEK5 transcription and expression. In addition, the phosphorylation of MEK5 significantly increased in breast cancer cells corresponding to metastatic capability of breast cancer cells. The depletion of MEK5 by shRNA significantly decreased breast cancer invasion. Ectopic expression of MEK5 could confer non-invasive breast cancer cells to become invasion capable cells. Moreover, the phosphorylation of Erk5, a MEK5-regulated downstream kinase, was also upregulated consistent with the increased level of active MEK5. Our studies provide insights into a molecular mechanism by which MEK5 transcriptionally upregulated by Stat3 augments breast cancer cell EMT, which subsequently enhances cancer cell invasion and metastasis. This finding may suggest that Stat3 and MEK5/Erk5 pathways could be an effective therapeutic target for inhibition of breast cancer invasion and metastasis.

IL-22 mediates the oral mucosal wound healing via STAT3 in keratinocytes

OBJECTIVE

Wounds are common in the oral cavity. During wound healing, several cytokines are released, which are probably helpful in providing wound debridement, removal of damaged tissues and microbes. Most of the target cells of IL-22 are epithelial cells, which play an important role in mucosa immunity.

DESIGN

The function of IL-22 in oral diseases is not well understood. We investigated the expression level of IL-22, collagen I and p-stat3 (Tyr705) via a mice tongue wound model in vivo and detected the effect of IL-22 on the expression of MMP-1, type I collagen and p-stat3 in keratinocytes.

RESULTS

IL-22 and p-stat3 were associated with wound healing, and STAT3 was activated when the keratinocytes or the tongue tissue were stimulated by IL-22. In addition, IL-22 could mediate gene expression involved in wounds involving keratinocytes, such as type I collagen and MMP-1, which may contribute to scarless healing.

CONCLUSION

Our study suggests that IL-22 mediates wound healing via STAT3 in keratinocytes. This study reveals a new role for IL-22 in mediating wound healing.

Ovarian Cancer Chemoresistance Relies on the Stem Cell Reprogramming Factor PBX1

The evolution of chemoresistance is a fundamental characteristic of cancer that ultimately hampers its clinical management. However, it may be possible to improve patient outcomes significantly by a better understanding of resistance mechanisms, which cancers rely upon during the evolution to an untreatable state. Here we report an essential role of the stem cell reprogramming factor, PBX1, in mediating chemoresistance in ovarian carcinomas. In the clinical setting, high levels of PBX1 expression correlated with shorter survival in post-chemotherapy ovarian cancer patients. In tumor cells with low endogenous levels of PBX1, its enforced expression promoted cancer stem cell-like phenotypes, including most notably an increase in resistance to platinum-based therapy used most commonly for treating this disease. Conversely, silencing PBX1 in platinum-resistant cells that overexpressed PBX1 sensitized them to platinum treatment and reduced their stem-like properties. An analysis of published genome-wide chromatin immunoprecipitation data indicated that PBX1 binds directly to promoters of genes involved in stem cell maintenance and the response to tissue injury. We confirmed direct regulation of one of these genes, STAT3, demonstrating that the PBX1 binding motif at its promoter acted to positively regulate STAT3 transcription. We further demonstrated that a STAT3/JAK2 inhibitor could potently sensitize platinum-resistant cells to carboplatin and suppress their growth in vivo Our findings offer a mechanistic rationale to target the PBX1/STAT3 axis to antagonize a key mechanism of chemoresistance in ovarian cancers and possibly other human cancers. Cancer Res; 76(21); 6351-61. ©2016 AACR.

Aphanin, a triterpenoid from Amoora rohituka inhibits K-Ras mutant activity and STAT3 in pancreatic carcinoma cells

Mutations of the K-Ras gene occur in over 90 % of pancreatic carcinomas, and to date, no targeted therapies exist for this genetically defined subset of cancers. STAT3 plays a critical role in KRAS-driven pancreatic tumorigenesis, suggesting its potential as a therapeutic target in this cancer. Therefore, finding novel and potential drugs to inhibit oncogenic K-Ras is a major challenge in cancer therapy. In an attempt to develop novel anti-KRAS mutant chemotherapeutics, we isolated three novel triterpenoids from Amoora rohituka stem and their chemical structures were characterized by extensive 1H-NMR, 13C-NMR, Mass, IR spectroscopic studies and chemical transformations. Aphanin (3 alpha-angeloyloxyolean-12-en-28-oic acid) is one of the isolated novel triterpenoid compounds. We found aphanin exhibited antiproliferative effects, caused G0-G1 cell cycle arrest, inhibits K-Ras G12D mutant activity by decreased STAT3, p-STAT3, Akt, p-Akt, cyclin D1 and c-Myc expressions, and induced apoptosis in pancreatic cancer HPAF-II (ΔKRAS G12D ) cells. The apoptosis proceeded through depletion of GSH with a concomitant increase in the reactive oxygen species production. The results of our study have important implications for the development of aphanin as potential novel agent for the treatment of K-Ras mutant pancreatic cancer, and STAT3-cMyc-cyclinD1 axis may serve as an important predictive biomarker for the therapeutic efficacy.

miR-182-5p Induced by STAT3 Activation Promotes Glioma Tumorigenesis

Malignant glioma is an often fatal type of cancer. Aberrant activation of STAT3 leads to glioma tumorigenesis. STAT3-induced transcription of protein-coding genes has been extensively studied; however, little is known about STAT3-regulated miRNA gene transcription in glioma tumorigenesis. In this study, we found that abnormal activation or decreased expression of STAT3 promotes or inhibits the expression of miR-182-5p, respectively. Bioinformatics analyses determined that tumor suppressor protocadherin-8 (PCDH8) is a candidate target gene of miR-182-5p. miR-182-5p negatively regulated PCDH8 expression by directly targeting its 3'-untranslated region. PCDH8 knockdown induced the proliferative and invasive capacities of glioma cells. Silencing of PCDH8 or miR-182-5p mimics could reverse the inhibitory effect of WP1066, a STAT3 inhibitor, or STAT3 knockdown in vitro and in vivo on glioma progression. Clinically, expression levels of PCDH8 were inversely correlated with those of p-STAT3 or miR-182-5p in glioblastoma tissues. These findings reveal that the STAT3/miR-182-5p/PCDH8 axis has a critical role in glioma tumorigenesis and that targeting the axis may provide a new therapeutic approach for human glioma. Cancer Res; 76(14); 4293-304. ©2016 AACR.

The PI3K/Akt, p38MAPK, and JAK2/STAT3 signaling pathways mediate the protection of SO2 against acute lung injury induced by limb ischemia/reperfusion in rats

Sulfur dioxide (SO2) is naturally synthesized by glutamate-oxaloacetate transaminase (GOT) from L-cysteine in mammalian cells. We found that SO2 may have a protective effect on acute lung injury (ALI) induced by limb ischemia/reperfusion (I/R) in rats. The PI3K/Akt, p38MAPK, and JAK2/STAT3 pathways are crucial in cell signaling transduction. The present study aims to verify the role of SO2 on limb I/R-induced ALI, and investigate whether PI3K/Akt, p38MAPK, and JAK2/STAT3 pathways were involved, as well as the relationship among the three pathways; we used specific inhibitors (LY294002, SB03580, and Stattic) to block them, respectively. The experimental methods of Western, ELISA, TUNEL, etc., were used to test the results. In the I/R group, the parameters of lung injury (MDA, MPO, TUNEL, cytokines) increased significantly, but the administration of Na2SO3/NaHSO3 attenuated the damage in the lung. The Western results showed that the rat's lung exist expression of P-STAT3, P-AKT, and P-p38 proteins. After I/R, P-STAT3, P-Akt, and P-p38 proteins expression all increased. After using Na2SO3/NaHSO3, P-Akt, and P-p38 proteins expression increased, but P-STAT3 protein expression decreased. We also found a strange phenomenon; compared to the I/R + SO2 group, the administration of stattic, P-p38 protein expression showed no change, but P-Akt protein expression increased (p < 0.05). In conclusion, SO2 has a protective effect on rats with limb I/R-induced ALI. The JAK2/STAT3, PI3K/Akt, and p38MAPK pathways are likely all involved in the process, and the JAK2/STAT3 pathway may have an impact on the P13K/Akt pathway.

Tumoral Immune Cell Exploitation in Colorectal Cancer Metastases Can Be Targeted Effectively by Anti-CCR5 Therapy in Cancer Patients

The immune response influences the clinical course of colorectal cancer (CRC). Analyzing the invasive margin of human CRC liver metastases, we identified a mechanism of immune cell exploitation by tumor cells. While two distinct subsets of myeloid cells induce an influx of T cells into the invasive margin via CXCL9/CXCL10, CCL5 is produced by these T cells and stimulates pro-tumoral effects via CCR5. CCR5 blockade in patient-derived functional in vitro organotypic culture models showed a macrophage repolarization with anti-tumoral effects. These anti-tumoral effects were then confirmed in a phase I trial with a CCR5 antagonist in patients with liver metastases of advanced refractory CRC. Mitigation of tumor-promoting inflammation within the tumor tissue and objective tumor responses in CRC were observed.

Original Research: Stable expression of miR-34a mediates fetal hemoglobin induction in K562 cells

Sickle cell anemia is a common genetic disorder caused by a point mutation in the sixth codon of the β-globin gene affecting people of African descent worldwide. A wide variety of clinical phenotypes ranging from mild to severe symptoms and complications occur due to hemoglobin S polymerization, red blood cell sickling, and vaso-occlusion. Research efforts are ongoing to develop strategies of fetal hemoglobin (HbF; α2γ2) induction to inhibit sickle hemoglobin polymerization and improve clinical outcomes. Insights have been gained from investigating mutations in the β-globin locus or transcription factors involved in the mechanisms of hemoglobin switching. Recent efforts to expand molecular targets that modulate γ-globin expression involve microRNAs that work through posttranscriptional gene regulation. Therefore, the goal of our study was to identify novel microRNA genes involved in fetal hemoglobin expression. Using in silico analysis, we identified a miR-34a binding site in the γ-globin mRNA which was tested for functional relevance. Stable expression of the shMIMIC miR-34a lentivirus vector increased fetal hemoglobin levels in single cell K562 clones consistent with silencing of a γ-globin gene repressor. Furthermore, miR-34a promoted cell differentiation supported by increased expression of KLF1, glycophorin A, and the erythropoietin receptor. Western blot analysis of known negative regulators of γ-globin including YY1, histone deacetylase 1, and STAT3, which are regulated by miR-34a showed no change in YY1 and histone deacetylase 1 levels; however, total- and phosphorylated-STAT3 levels were decreased in single cell miR-34a K562 clones. These data support a mechanism of fetal hemoglobin activation by miR-34a involving STAT3 gene silencing.

Morphine-Induced Preconditioning: Involvement of Protein Kinase A and Mitochondrial Permeability Transition Pore

Background

Morphine induces myocardial preconditioning (M-PC) via activation of mitochondrial large conductance Ca²⁺-sensitive potassium (mK_Ca) channels. An upstream regulator of mK_Ca channels is protein kinase A (PKA). Furthermore, mK_Ca channel activation regulates mitochondrial bioenergetics and thereby prevents opening of the mitochondrial permeability transition pore (mPTP). Here, we investigated in the rat heart in vivo whether 1) M-PC is mediated by activation of PKA, and 2) pharmacological opening of the mPTP abolishes the cardioprotective effect of M-PC and 3) M-PC is critically dependent on STAT3 activation, which is located upstream of mPTP within the signalling pathway.

Methods

Male Wistar rats were randomised to six groups (each n = 6). All animals underwent 25 minutes of regional myocardial ischemia and 120 minutes of reperfusion. Control animals (Con) were not further treated. Morphine preconditioning was initiated by intravenous administration of 0.3 mg/kg morphine (M-PC). The PKA blocker H-89 (10 μg/kg) was investigated with and without morphine (H-89+M-PC, H-89). We determined the effect of mPTP opening with atractyloside (5 mg/kg) with and without morphine (Atr+M-PC, Atr). Furthermore, the effect of morphine on PKA activity was tested in isolated adult rat cardiomyocytes. In further experiments in isolated hearts we tested the protective properties of morphine in the presence of STAT3 inhibition, and whether pharmacological prevention of the mPTP-opening by cyclosporine A (CsA) is cardioprotective in the presence of STAT3 inhibition.

Results

Morphine reduced infarct size from 64±5% to 39±9% (P<0.05 vs. Con). H-89 completely blocked preconditioning by morphine (64±9%; P<0.05 vs. M-PC), but H-89 itself had not effect on infarct size (61±10%; P>0.05 vs. Con). Also, atractyloside abolished infarct size reduction of morphine completely (65±9%; P<0.05 vs. M-PC) but had no influence on infarct size itself (64±5%; P>0.05 vs. Con). In isolated hearts STAT3 inhibitor Stattic completely abolished morphine-induced preconditioning. Administration of Stattic and mPTP inhibitor cyclosporine A reduced infarct size to 31±6% (Stat+CsA, P<0.05 vs. Con). Cyclosporine A alone reduced infarct size to 26±7% (CsA P<0.05 vs. Con). In cardiomyocytes, PKA activity was increased by morphine.

Conclusion

Our data suggest that morphine-induced cardioprotection is mediated by STAT3-activation and inhibition of mPTP, with STA3 located upstream of mPTP. There is some evidence that protein kinase A is involved within the signalling pathway.

Acquired resistance of pancreatic cancer cells to treatment with gemcitabine and HER-inhibitors is accompanied by increased sensitivity to STAT3 inhibition

Drug-resistance is a major contributing factor for the poor prognosis in patients with pancreatic cancer. We have shown previously that the irreversible ErbB family blocker afatinib, is more effective than the reversible EGFR tyrosine kinase inhibitor erlotinib in inhibiting the growth of human pancreatic cancer cells. The aim of this study was to develop human pancreatic cancer cell (BxPc3) variants with acquired resistance to treatment with gemcitabine, afatinib, or erlotinib, and to investigate the molecular changes that accompany the acquisition of a drug-resistant phenotype. We also investigated the therapeutic potential of various agents in the treatment of such drug-resistant variants. Three variant forms of BxPc3 cells with acquired resistance to gemcitabine (BxPc3GEM), afatinib (BxPc3AFR) or erlotinib (BxPc3OSIR) were developed following treatment with increasing doses of such drugs. The expression level, mutational and phosphorylation status of various growth factor receptors and downstream cell signaling molecules were determined by FACS, human phopsho-RTK array, and western blot analysis while the sulforhodamine B assay was used for determining the effect of various agents on the growth of such tumours. We found that all three BxPc3 variants with acquired resistance to gemcitabine (BxPc3GEM), afatinib (BxPc3AFR) or erlotinib (BxPc3OSIR) also become less sensitive to treatment with the two other agents. Acquisition of resistance to these agents was accompanied by upregulation of p-c-MET, p-STAT3, CD44, increased autocrine production of EGFR ligand amphiregulin and differential activation status of EGFR tyrosine residues as well as downregulation of total and p-SRC. Of all therapeutic interventions examined, including the addition of an anti-EGFR antibody ICR62, an anti-CD44 monoclonal antibody, and of STAT3 or c-MET inhibitors, only treatment with the STAT3 inhibitor Stattic produced a higher growth inhibitory effect in all three drug-resistant variants. In addition, treatment with a combination of afatinib with either c-MET inhibitor Crizotinib or Stattic resulted in an additive or synergistic growth inhibition in all three variants. Our results suggest that activation of STAT3 may play an important role in the acquisition of resistance to gemcitabine and HER inhibitors in pancreatic cancer and warrant further studies on the therapeutic potential of STAT3 inhibitors in such a setting.

[Role of STAT3 signaling pathway in hypoxic-ischemic brain damage of neonatal rats]

OBJECTIVE

To study the role and mechanisms of STAT3 signaling pathway in hypoxic-ischemic brain damage (HIBD) of neonatal rats.

METHODS

Eighty 7-day-old Sprague-Dawley rats were randomly divided into two groups: HI and sham-operated (n=40 each). The rats in the HI group were subjected to right carotid artery ligation and subsequent hypoxia exposure (8% O2) for 2.5 hours, and the rats in the sham-operated group underwent the right carotid artery dissection without subsequent ligation or hypoxia treatment. Brain tissue samples were collected at 4, 6, 8, 12 and 24 hours after operation and hypoxic exposure. Immunohistochemistry and Western blot were used to detect the expression of STAT3, phosphorylated STAT3 (p-STAT3) and vascular endothelial growth factor (VEGF) proteins. TUNEL staining was used to detect apoptotic cells.

RESULTS

No significant difference in STAT3 expression was observed at all time points between the HI and sham-operated groups (P>0.05). Compared with the sham-operated group, the expression of p-STAT3 protein in the HI group was significantly upregulated at 4, 6, 8, 12 hours after operation and hypoxic exposure, and peaked at 6 hours (P<0.01). The VEGF expression in the HI group was higher than that in the sham-operated group at all time points, which peaked at 8 hours (P<0.05). TUNEL staining showed that the apoptotic cells increased significantly in a time-dependent manner compared with the sham-operated group (P<0.01).

CONCLUSIONS

HI may lead to phosphorylation of STAT3 which probably induces the VEGF expression in the brain of neonatal rats. The activated STAT3 signaling pathway may be involved in the apoptosis regulation of nerve cells, and related to apoptosis inhibition of nerve cells.

STAT3-regulated exosomal miR-21 promotes angiogenesis and is involved in neoplastic processes of transformed human bronchial epithelial cells

Although microRNA (miRNA) enclosed in exosomes can mediate intercellular communication, the roles of exosomal miRNA and angiogenesis in lung cancer remain unclear. We investigated functions of STAT3-regulated exosomal miR-21 derived from cigarette smoke extract (CSE)-transformed human bronchial epithelial (HBE) cells in the angiogenesis of CSE-induced carcinogenesis. miR-21 levels in serum were higher in smokers than those in non-smokers. The medium from transformed HBE cells promoted miR-21 levels in normal HBE cells and angiogenesis of human umbilical vein endothelial cells (HUVEC). Transformed cells transferred miR-21 into normal HBE cells via exosomes. Knockdown of STAT3 reduced miR-21 levels in exosomes derived from transformed HBE cells, which blocked the angiogenesis. Exosomes derived from transformed HBE cells elevated levels of vascular endothelial growth factor (VEGF) in HBE cells and thereby promoted angiogenesis in HUVEC cells. Inhibition of exosomal miR-21, however, decreased VEGF levels in recipient cells, which blocked exosome-induced angiogenesis. Thus, miR-21 in exosomes leads to STAT3 activation, which increases VEGF levels in recipient cells, a process involved in angiogenesis and malignant transformation of HBE cells. These results, demonstrating the function of exosomal miR-21 from transformed HBE cells, provide a new perspective for intervention strategies to prevent carcinogenesis of lung cancer.