Stat6 cooperates with Sp1 in controlling breast cancer cell proliferation by modulating the expression of p21(Cip1/WAF1) and p27 (Kip1)

STAT family of transcription factors in breast cancer: Pathogenesis and therapeutic opportunities and challenges

Breast cancer is the most commonly diagnosed cancer and second-leading cause of cancer deaths in women. Breast cancer stem cells (BCSCs) promote metastasis and therapeutic resistance contributing to tumor relapse. Through activating genes important for BCSCs, transcription factors contribute to breast cancer metastasis and therapeutic resistance, including the signal transducer and activator of transcription (STAT) family of transcription factors. The STAT family consists of six major isoforms, STAT1, STAT2, STAT3, STAT4, STAT5, and STAT6. Canonical STAT signaling is activated by the binding of an extracellular ligand to a cell-surface receptor followed by STAT phosphorylation, leading to STAT nuclear translocation and transactivation of target genes. It is important to note that STAT transcription factors exhibit diverse effects in breast cancer; some are either pro- or anti-tumorigenic while others maintain dual, context-dependent roles. Among the STAT transcription factors, STAT3 is the most widely studied STAT protein in breast cancer for its critical roles in promoting BCSCs, breast cancer cell proliferation, invasion, angiogenesis, metastasis, and immune evasion. Consequently, there have been substantial efforts in developing cancer therapeutics to target breast cancer with dysregulated STAT3 signaling. In this comprehensive review, we will summarize the diverse roles that each STAT family member plays in breast cancer pathobiology, as well as, the opportunities and challenges in pharmacologically targeting STAT proteins and their upstream activators in the context of breast cancer treatment.

Ethanolic Leaf Extract of C. angustifolia Instigates ROS Mediated Apoptosis within Glioblastoma C6 Cells

Glioblastoma multiforme or GBM is a destructive malignancy of the central nervous system and is accountable for leading cause of cancer related mortality. Inadequate success rate of surgical interventions and development of resistance towards the current therapeutical regime provides impetus for exploring novel therapeutical interventions against the disease. Recently, several epidemiological studies have explored the plausible utility of natural, dietary compounds in influencing the development, progression, and cancer metastasis. Recently, different phytoconstituents of Cassia angustifolia were found to be associated with anti-microbial, anti-cancer and anti-inflammatory effects. Therefore, the aim of the present study was to evaluate the anti-proliferative efficacy of ethanolic leaf extract of C. angustifolia (LCaEt-OH) against rat derived glioblastoma C6 cells. Briefly, the anti-proliferative potential of LCaEt-OH was assessed using MTT assay, quantitative estimation of ROS, and evaluation of mitochondrial membrane potential (ΔΨ_m). Moreover, the activity of caspases involved in intrinsic apoptotic pathways was also investigated using colorimetric kit followed by quantitative RT-PCR evaluation of modulation in gene expressions triggered due to LCaEt-OH treatment. Treatment of LCaEt-OH on C6 cells elucidated substantial dose-dependent decline in cellular viability. Furthermore, LCaEt-OH showed its efficacy in substantially enhancing intracellular ROS. LCaEt-OH also incited apoptosis in C6 cells by instigating nuclear condensation and dissipation of ΔΨ_m. In addition, LCaEt-OH mediated instigation of apoptosis was directly influenced by increased activity of caspases indispensable for intrinsic apoptotic pathway. These conclusive evidences indicate towards anticancer efficacy of LCaEt-OH against C6 cells.

Farnesiferol C Exerts Antiproliferative Effects on Hepatocellular Carcinoma HepG2 Cells by Instigating ROS-Dependent Apoptotic Pathway

Farnesiferol C (Far-C) is a coumarin commonly extracted from Ferula asafetida and is popularly used as a traditional source of natural remedy. Liver cancer or hepatocellular carcinoma (HCC) has emerged as a major cause behind cancer burden, and limited therapeutic interventions have further aggravated the clinical management of HCC. In the present study, the authors tested the hypothesis that Far-C-instigated oxidative stress resulted in anti-proliferation and apoptosis instigation within human liver cancer HepG2 cells. The observations reported herewith indicated that Far-C exerted considerable cytotoxic effects on HepG2 cells by reducing the cell viability (p < 0.001) in a dose-dependent manner. Far-C exposure also resulted in enhanced ROS production (p < 0.01) which subsequently led to loss of mitochondrial membrane potential. Far-C-instigated oxidative stress also led to enhanced nuclear fragmentation and condensation as revealed through Hoechst-33342. These molecular changes post-Far-C exposure also incited apoptotic cell death which concomitantly led to significant activation of caspase-3 (p < 0.001). Furthermore, Far-C exhibited its competence in altering the expression of genes involved in apoptosis regulation (Bax, Bad, and Bcl2) along with genes exerting regulatory effects on cell cycle (cyclinD1) and its progression (p21Cip1 and CDK4). The evidence thus clearly shows the preclinical efficacy of Far-C against HepG2 cells. However, further mechanistic investigations deciphering the alteration of different pathways post-Far-C exposure will be highly beneficial.

STAT6 Upregulates NRP1 Expression in Endothelial Cells and Promotes Angiogenesis

The role of signal transducer and activator of transcription 6 (STAT6) in tumor growth has been widely recognized. However, its effects on the regulation of angiogenesis remain unclear. In this study, we found that STAT6 promoted angiogenesis, possibly by increasing the expression of neuropilin-1 (NRP1) in endothelial cells (ECs). Both STAT6 inhibitor (AS1517499) and STAT6 siRNA reduced EC proliferation, migration, and tube-formation, accompanied by downregulation of NRP1, an angiogenesis regulator. Furthermore, IL-13 induced activation of STAT6 and then increased NRP1 expression in ECs. IL-13-induced EC migration and tube formation were inhibited by NRP1 siRNA. Luciferase assay and chromatin immunoprecipitation assay demonstrated that STAT6 could directly bind to human NRP1 promoter and increase the promoter activity. In tumor xenograft models, inhibition of STAT6 reduced xenograft growth, tumor angiogenesis, and NRP1 expression in vivo. Overall, these results clarified the novel mechanism by which STAT6 regulates angiogenesis, and suggested that STAT6 may be a potential target for anti-angiogenesis therapy.

IL-4 and IL-13 Promote Proliferation of Mammary Epithelial Cells through STAT6 and IRS-1

T helper (Th)2 cytokines such as interleukin (IL)-4 and IL-13 control immune function by acting on leukocytes. They also regulate multiple responses in non-hematopoietic cells. During pregnancy, IL-4 and IL-13 facilitate alveologenesis of mammary glands. This particular morphogenesis generates alveoli from existing ducts and requires substantial cell proliferation. Using 3D cultures of primary mouse mammary epithelial cells, we demonstrate that IL-4 and IL-13 promote cell proliferation, leading to enlargement of mammary acini with partially filled lumens. The mitogenic effects of IL-4 and IL-13 are mediated by STAT6 as inhibition of STAT6 suppresses cell proliferation and improves lumen formation. In addition, IL-4 and IL-13 stimulate tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1). Prolonged treatment with these cytokines leads to increased IRS-1 abundance, which, in turn, amplifies IL-4- and IL-13-stimulated IRS-1 tyrosine phosphorylation. Through signaling crosstalk between IL-4/IL-13 and insulin, a hormone routinely included in mammary cultures, IRS-1 tyrosine phosphorylation is further enhanced. Lowering IRS-1 expression reduces cell proliferation, suggesting that IRS-1 is involved in IL-4- and IL-13-stimulated cell proliferation. Thus, a Th2-dominant cytokine milieu during pregnancy confers mammary gland development by promoting cell proliferation.

Umbelliferone Ameliorates Benign Prostatic Hyperplasia by Inhibiting Cell Proliferation and G1/S Phase Cell Cycle Progression through Regulation of STAT3/E2F1 Axis

Umbelliferone (UMB), also known as 7-hydroxycoumarin, is a derivative of coumarin, which is widely found in many plants such as carrots, coriander, and garden angelica. Although many studies have already revealed the various pharmacological properties of UMB, its effect on benign prostatic hyperplasia (BPH) remains unclear. Therefore, the present study aimed to elucidate the underlying mechanism of the anti-proliferative effect of UMB in a human benign prostatic hyperplasia cell line (BPH-1), as well as its ameliorative effect on BPH in testosterone propionate (TP)-induced rats. The results showed that UMB exerts an anti-proliferative effect in BPH-1 cells by modulating the signal transducer and activator of transcription 3 (STAT3)/E2F transcription factor 1 (E2F1) axis. UMB treatment not only inhibited androgen/androgen receptor (AR) signaling-related markers, but also downregulated the overexpression of G1/S phase cell cycle-related markers. In TP-induced rats, UMB administration demonstrated an anti-BPH effect by significantly reducing prostate size, weight, and epithelial thickness. In addition, UMB suppressed cell proliferation by reducing the expression of proliferating cell nuclear antigen (PCNA) and p-STAT3 (Tyr 705) in prostate tissue following TP injection. These findings suggest that UMB has pharmacological effects against BPH.

EML4-ALK-mediated activation of the JAK2-STAT pathway is critical for non-small cell lung cancer transformation

BACKGROUND

The echinoderm microtubule-associated protein-like-4 anaplastic lymphoma kinase (EML4-ALK) fusion gene was identified in a subset of non-small cell lung cancer (NSCLC) patients. They responded positively to ALK inhibitors. This study aimed to characterize the mechanisms triggered by EML4-ALK to induce NSCLC transformation.

METHODS

HEK293 and NIH3T3 cells were transfected with EML4-ALK variant 3 or pcDNA3.1-NC. H2228 cells were transfected with siRNA-EML4-ALK or siRNA-NC. Cell viability and proliferation were measured by the CCK-8 and EdU methods, respectively. Flow cytometry revealed apoptosis. Gene expression profiles were generated from a signaling pathway screen in EML4-ALK-regulated lung cancer cells and verified by qPCR and Western blotting. The co-immunoprecipitation and immunohistochemistry/ immunofluorescence determined the interaction and colocalization of JAK2-STAT pathway components with EML4-ALK.

RESULTS

Microarray identified several genes involved in the JAK2-STAT pathway. JAK2 and STAT6 were constitutively phosphorylated in H2228 cells. EML4-ALK silencing downregulated phosphorylation of STAT6. Expression of EML4-ALK in HEK293 and NIH3T3 cells activated JAK2, STAT1, STAT3, STAT5, and STAT6. In EML4-ALK-transfected HEK293 cells and EML4-ALK-positive H2228 cells, activated STAT6 and JAK2 colocalized with ALK. STAT3 and STAT6 were phosphorylated and translocated to the nucleus of H2228 cells following IL4 or IL6 treatment. Apoptosis increased, while cell proliferation and DNA replication decreased in H2228 cells following EML4-ALK knockdown. In contrast, HEK293 cell viability increased following EML4-ALK overexpression, while H2228 cell viability significantly decreased after treatment with ALK or JAK-STAT pathway inhibitors.

CONCLUSIONS

Our data suggest that the aberrant expression of EML4-ALK leads to JAK2-STAT signaling pathway activation, which is essential for the development of non-small cell lung cancer.

Glycyrrhizin Mediates Downregulation of Notch Pathway Resulting in Initiation of Apoptosis and Disruption in the Cell Cycle Progression in Cervical Cancer Cells

Growing emphasis on exploring the antiproliferative potential of natural compounds has gathered momentum for the formulation of anticancer drugs. In the present study, the anticancer and apoptotic potential of glycyrrhizin (GLY) was studied on HPV^- C33A cervical cancer (CCa) cells. Our results indicated that GLY exerted antiproliferative effects in the C33A cells by inducing significant cytotoxicity. Treatment with GLY substantially increases the apoptosis in a dose-dependent manner via disrupting the mitochondrial membrane potential. GLY induced apoptosis in C33A cells via activation of capsase-9 (intrinsic pathway) and caspase-8 (extrinsic pathway) along with the modulation of pro- and antiapoptotic protein expression. Moreover, GLY also exerted cell cycle arrest in C33A cells at G₀/G₁ phase which was associated with the decreased expression of cyclin D1 and cyclin-dependent kinase 4 (CDK4) along with the increased expression of CDK inhibitor p21^Cip1. Furthermore, GLY treated CCa cells exhibited significant downregulation of Notch signaling pathway which may be associated with increased apoptosis as well as cell cycle arrest in C33A CCa cells. Thus, GLY could be an appendage in the prevention and management of CCa.

HMGB1 orchestrates STING-mediated senescence via TRIM30α modulation in cancer cells

Although cellular senescence has emerged as a novel therapeutic concept in cancer, its underlying mechanisms remain unclear. High mobility group box 1 (HMGB1) and stimulator of interferon genes (STING) are involved in senescence. However, their interactions in senescence have not been reported. Therefore, in this study, we investigated the relationships between HMGB1 and STING in senescence in cancer and other cells. In mouse melanoma cells and several other cell lines, doxorubicin treatment induced senescence in an HMGB1-dependent manner. These responses were mediated by STING, and this function of STING was negatively regulated by the E3 ligase tripartite motif protein 30α (TRIM30α). We also found that HMGB1 bound to the TRIM30α promoter and then suppressed its expression by inhibiting its transcription, which enhanced STING-induced senescence. This mechanism was further mediated by signal transducer and activator of transcription 6 (STAT6) and p21. Overall, our findings demonstrated that HMGB1 orchestrated STING-STAT6-p21-mediated senescence by regulating TRIM30α as an alternative anticancer mechanism.

ARHGAP24 inhibits cell proliferation and cell cycle progression and induces apoptosis of lung cancer via a STAT6-WWP2-p27 axis

Rho GTPase-activating proteins (RhoGAPs) have been reported to be of great importance in the initiation and development of many different cancers. However, their biological roles and regulatory mechanisms in lung cancer development and progression are poorly defined. Real-time PCR or western blotting analysis was used to detect Rho GTPase-activating protein 24 (ARHGAP24), WWP2, p27, p-STAT6 and STAT6 expression levels as well as the activity of RhoA and Rac1 in lung cancer. Cell proliferation, apoptosis and cell cycle were measured by CCK-8 and flow cytometry analysis. Tumor growth of lung cancer cells was measured using a nude mouse xenograft experiment model in vivo. The correlation between WWP2 and p27 was measured by co-immunoprecipitation and ubiquitination analysis. We found that ARHGAP24 expression was lower in lung cancer tissues collected from the The Cancer Genome Atlas and independent hospital database. Overexpression of ARHGAP24 significantly suppressed cell proliferation and the activity of RhoA and Rac1, induced cell apoptosis and arrested cell cycle at the G₀–G₁ phase. ARHGAP24 overexpression also inhibited tumor growth in nude mice, whereas knockdown of ARHGAP24 significantly promoted cell proliferation and WWP2 expression and inhibited cell cycle arrest at G₁ phase through activating STAT6 signaling. ARHGAP24 overexpression inhibited WWP2 overexpression-induced cell proliferation, cell cycle progression and the decreased p27 expression. Moreover, WWP2 was found interacted with p27, and WWP2 overexpression promoted the ubiquitination of p27. In conclusion, our findings suggest that ARHGAP24 inhibits cell proliferation and cell cycle progression and induces cell apoptosis of lung cancer via a STAT6-WWP2-p27 axis.

Cytokines and the immune response in obesity-related disorders

The increasing prevalence of obesity and the associated morbidity and mortality are important public health problems globally. There is an important relationship between an unhealthy lifestyle and increased serum inflammatory cytokines. Adipocytes secrete several pro-inflammatory cytokines involved in the recruitment and activation of macrophages resulting in chronic low-grade inflammation. Increased cytokines in obese individual are related to the progression of several disorders including cardiovascular disease, hypertension, and insulin resistance. In present review we have summarized the crucial roles of cytokines and their inflammatory functions in obesity-related immune disorders.

Prognostic value of key genes of the JAK-STAT signaling pathway in patients with cutaneous melanoma

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway is involved in cell immunity, division and death, as well as in tumor formation. The expression of key genes in the JAK-STAT signaling pathway in different types of cancer serves different roles. However, few reports are available on the prognostic value of the genes of the JAK-STAT signaling pathway in skin cutaneous melanoma (SKCM). The potential prognostic value of gene expression in the JAK-STAT signaling pathway in patients with SKCM was analyzed in the present study using data obtained from The Cancer Genome Atlas. To predict the potential functions and mechanisms of these genes in SKCM, gene set enrichment analysis (GSEA) and bioinformatics analysis were performed. A nomogram model including gene expression level and high risk factors was used to predict the risk level of prognostic. High expression levels of STAT1, STAT3, STAT4 and STAT5B, and low expression levels of STAT6 were associated with favorable prognosis [adjusted P<0.001; hazard ratio (HR), 0.595; 95% confidence interval (CI), 0.455–0.778; adjusted P=0.018; HR, 0.725; 95% CI, 0.555–0.947; adjusted P<0.001; HR, 0.590; 95% CI, 0.450–0.773; adjusted P=0.007; HR, 0.690; 95% CI, 0.526–0.940; and adjusted P=0.026; HR, 0.737, 95% CI, 0.563–0.964, respectively]. GSEA results demonstrated that these genes were involved in cell differentiation, invasion, adhesion, migration, cycle, colony formation and mitogen-activated protein kinase signaling. The combination of genes with favorable prognosis had a better effect on the overall survival (univariate survival analysis, P<0.05). The results of the present study suggest that STAT1, STAT3, STAT4, STAT5B and STAT6 gene expression may be used as a potential prognostic biomarker of SKCM, and the combined outcomes may exhibit a stronger interaction and higher survival time for SKCM.

Metformin and Breast Cancer: Molecular Targets

Metformin has been the first-line drug for the treatment of type II diabetes mellitus for decades, being presently the most widely prescribed antihyperglycemic drug. Retrospective studies associate the use of metformin with a reduction in cancer incidence and cancer-related death. However, despite extensive research about the molecular effects of metformin in cancer cells, its mode of action remains controversial. The major molecular targets of metformin include complex I of the mitochondrial electron transport chain, adenosine monophosphate (AMP)-activated protein kinase (AMPK), and mechanistic target of rapamycin complex 1 (mTORC1), but AMPK-independent effects of metformin have also been described. Breast cancer is one of the leading causes of cancer-related morbidity and mortality among women worldwide. Several studies have reinforced a link between breast cancer risk and diabetes. Moreover, metformin significantly reduces breast cancer risk, compared to patients who are not using metformin and is independent of diabetes status. In this review, we summarize the current molecular evidence to elucidate metformin's mode of action against breast cancer cells.

New compound ChlA-F induces autophagy-dependent anti-cancer effect via upregulating Sestrin-2 in human bladder cancer

ChlA-F is a novel conformation-derivative of Cheliensisin A, styryl-lactone isolates that show potent anti-tumor potential in vivo and vitro. However, the anti-cancer activity and its potential mechanisms underlying ChlA-F action have never been explored. In the present study, we evaluated the potency of ChlA-F on autophagy-mediated anchorage-independent growth inhibition in human high-grade invasive bladder cancer (BC) cells. We found that ChlA-F treatment significantly inhibited anchorage-independent growth of human BC cells by inducing autophagy in a Sestrin-2 (SESN2)-dependent fashion. Our results revealed that ChlA-F treatment specifically induced SESN2 expression via increasing its transcription and mRNA stability. On one hand, ChlA-F treatment markedly attenuated Dicer protein abundance, in turn abolishing miR-27a maturation and further relieving miR-27a binding directly to SESN2 mRNA 3'UTR, thereby promoting SESN2 mRNA stabilization. On the other hand, ChlA-F treatment promoted Sp1 abundance and consequently mediated SESN2 transcription. These results demonstrate that its activation of the autophagic pathway through specifically promoting SESN2 expression mediates the anti-cancer effect of ChlA-F, which offers insights into the novel anti-cancer effect of ChlA-F on BC, as well as providing therapeutic alternatives against human BC.

Effects of SOX15 on the colorectal cancer cells via downregulation of the Wnt/β-catenin signaling pathway

Aim: To detect the function and mechanism of SOX15 in colorectal cancer. Materials & methods: The expression of SOX15 in colorectal cancer (CRC) cells and tissues was detected by real-time PCR, quantitative real-time PCR and immunohistochemistry. The overexpression of SOX15 in cells was tested by western blot, CCK-8, FACS analysis, transwell and clone assay. Moreover, SOX15 regulated Wnt pathway investigated by western blot.Results: We found that SOX15 has a low-expression in CRC cells and tissues. Overexpression of SOX15 can inhibit the proliferation, migration and invasion of cells and induce cells apoptosis. Furthermore, SOX15 could be the inhibitor of Wnt/β-catenin pathway in CRC. Conclusion: SOX15 can be a tumor suppressor in CRC by suppressing the Wnt/β-catenin signaling pathway.

Tumor growth suppressive effect of IL-4 through p21-mediated activation of STAT6 in IL-4Rα overexpressed melanoma models

To evaluate the significance of interleukin 4 (IL-4) in tumor development, we compared B16F10 melanoma growth in IL-4-overespressing transgenic mice (IL-4 mice) and non-transgenic mice. In IL-4 mice, reduced tumor volume and weight were observed when compared with those of non-transgenic mice. Significant activation of DNA binding activity of STAT6, phosphorylation of STAT6 as well as IL-4, IL-4Rα and p21 expression were found in the tumor tissues of IL-4 mice compared to non-transgenic mice. Higher expression of IL-4, STAT6 and p21 in human melanoma tissue compared to normal human skin tissue was also found. Higher expression of apoptotic protein such as cleaved caspase-3, cleaved caspase-8, cleaved caspase-9, Bax, p53 and p21, but lower expression levels of survival protein such as Bcl-2 were found in the tumor of IL-4 mice. In vitro study, we found that overexpression of IL-4 significantly inhibited SK-MEL-28 human melanoma cell and B16F10 murine melanoma cell growth via p21-mediated activation of STAT6 pathway as well as increased expression of apoptotic cell death proteins. Moreover, p21 knockdown with siRNA abolished IL-4 induced activation of STAT6 and expression of p53 and p21 accompanied with reduced IL-4 expression as well as melanoma cell growth inhibition. Therefore, these results showed that IL-4 overexpression suppressed tumor development through p21-mediated activation of STAT6 pathways in melanoma models.

PVT1-derived miR-1207-5p promotes breast cancer cell growth by targeting STAT6

Accumulating evidence indicates that ectopic expression of non‐coding RNAs are responsible for breast cancer progression. Increased non‐coding RNA PVT1, the host gene of microRNA‐1207‐5p (miR‐1207‐5p), has been associated with breast cancer proliferation. However, how PVT1 functions in breast cancer is still not clear. In this study, we show a PVT1‐derived microRNA, miR‐1207‐5p, that promotes the proliferation of breast cancer cells by directly regulating STAT6. We first confirm the positive correlated expression pattern between PVT1 and miR‐1207‐5p by observing consistent induced expression by estrogen, and overexpression in breast cancer cell lines and breast cancer patient specimens. Moreover, silence of PVT1 also decreased miR‐1207‐5p expression. Furthermore, increased miR‐1207‐5p expression promoted, while decreased miR‐1207‐5p expression suppressed, cell proliferation, colony formation, and cell cycle progression in breast cancer cell lines. Mechanistically, a novel target of miR‐1207‐5p,STAT6, was identified by a luciferase reporter assay. Overexpression of miR‐1207‐5p decreased the levels of STAT6, which activated CDKN1A and CDKN1B to regulate the cell cycle. We also confirmed the reverse correlation of miR‐1207‐5p and STAT6 expression levels in breast cancer samples. Therefore, our findings reveal that PVT1‐derived miR‐1207‐5p promotes the proliferation of breast cancer cells by targeting STAT6, which in turn controls CDKN1A and CDKN1B expression. These findings suggest miR‐1207‐5p might be a potential target for breast cancer therapy.

Lack of STAT6 Attenuates Inflammation and Drives Protection against Early Steps of Colitis-Associated Colon Cancer

Colitis-associated colon cancer (CAC) is one of the most common malignant neoplasms and a leading cause of death. The immunologic factors associated with CAC development are not completely understood. Signal transducer and activator of transcription 6 (STAT6) is part of an important signaling pathway for modulating intestinal immune function and homeostasis. However, the role of STAT6 in colon cancer progression is unclear. Following CAC induction in wild-type (WT) and STAT6-deficient mice (STAT6^-/-), we found that 70% of STAT6^-/- mice were tumor-free after 8 weeks, whereas 100% of WT mice developed tumors. STAT6^-/- mice displayed fewer and smaller colorectal tumors than WT mice; this reduced tumorigenicity was associated with decreased proliferation and increased apoptosis in the colonic mucosa in the early steps of tumor progression. STAT6^-/- mice also exhibited reduced inflammation, diminished concentrations COX2 and nuclear β-catenin protein in the colon, and decreased mRNA expression of IL17A and TNFα, but increased IL10 expression when compared with WT mice. Impaired mucosal expression of CCL9, CCL25, and CXCR2 was also observed. In addition, the number of circulating CD11b⁺Ly6C^hiCCR2⁺ monocytes and CD11b⁺Ly6C^lowLy6G⁺ granulocytes was both decreased in a STAT6-dependent manner. Finally, WT mice receiving a STAT6 inhibitor in vivo confirmed a significant reduction in tumor load as well as less intense signs of CAC. Our results demonstrate that STAT6 is critical in the early steps of CAC development for modulating inflammatory responses and controlling cell recruitment and proliferation. Thus, STAT6 may represent a promising target for CAC treatment. Cancer Immunol Res; 5(5); 385-96. ©2017 AACR.

STAT6 deficiency ameliorates Graves' disease severity by suppressing thyroid epithelial cell hyperplasia

Signal transducer and activator of transcription 6 (STAT6) is involved in epithelial cell growth. However, little is known regarding the STAT6 phosphorylation status in Graves' disease (GD) and its role in thyroid epithelial cells (TECs). In this study, we found that STAT6 phosphorylation (p-STAT6) was significantly increased in TECs from both GD patients and experimental autoimmune Graves' disease mice and that STAT6 deficiency ameliorated GD symptoms. Autocrine IL-4 signalling in TECs activated the phosphorylation of STAT6 via IL-4 R engagement, and the downstream targets of STAT6 were Bcl-xL and cyclin D1. Thus, the IL-4-STAT6-Bcl-xL/cyclin D1 pathway is crucial for TEC hyperplasia, which aggravates GD. More importantly, in vitro and in vivo experiments demonstrated that STAT6 phosphorylation inhibited by AS1517499 decreased TEC hyperplasia, thereby reducing serum T3 and T4 and ameliorating GD. Thus, our study reveals that in addition to the traditional pathogenesis of GD, in which autoantibody TRAb stimulates thyroid-stimulating hormone receptors and consequently produces T3, T4, TRAb could also trigger TECs producing IL-4, and IL-4 then acts in an autocrine manner to activate p-STAT6 signalling and stimulate unrestricted cell growth, thus aggravating GD. These findings suggest that STAT6 inhibitors could be potent therapeutics for treating GD.

Downregulation of RNF128 Predicts Progression and Poor Prognosis in Patients with Urothelial Carcinoma of the Upper Tract and Urinary Bladder

Background: The TP53 tumor suppressor gene plays a crucial role in the carcinogenesis of many malignancies, including urothelial carcinoma (UC). Overexpression of p53 is associated with poor prognosis in UC. Recently, RING finger protein 128 (RNF128) was shown to be involved in p53-induced apoptosis, forming a negative feedback loop. However, the significance of RNF128 in patients with UC remains unknown. In this study, our aim was to evaluate the expression of RNF128 in UC and to assess its predictive and prognostic value in a well-established cohort. Methods: Through data mining from a published transcriptome (GSE31684), RNF128 was identified as the most differentially expressed gene in UC among those associated with negative regulation of the cytokine biosynthetic process (GO:0042036). Its immunoexpression was further evaluated using the H-scores of 340 patients with upper urinary tract UC (UTUC) and 295 with urinary bladder UC (UBUC). The scores were correlated with clinicopathological features, disease-specific survival (DSS) and metastasis-free survival (MeFS). We also used Western blot analysis to evaluate RNF128 protein expression in human urothelial cell (HUC) lines. Results: Downregulation of RNF128 expression was significantly associated with advanced pT stage (p<0.001), high histological grade (UTUC, p<0.001; UBUC, p=0.035), nodal metastasis (UTUC, p<0.001; UBUC, p=0.001), vascular invasion (UTUC, p<0.001; UBUC, p=0.008) and high mitotic rate (UTUC, p=0.003; UBUC, p=0.023). Low expression of RNF128 was an adverse prognosticator for DSS (UTUC, p<0.0001; UBUC, p<0.0001) and MeFS (UTUC, p<0.0001; UBUC, p=0.0002). Moreover, low expression was predictive of poor DSS (UTUC, p=0.006; UBUC, p=0.003) and MeFS (UTUC, p=0.009; UBUC, p=0.036) in multivariate comparisons. Western blot analysis showed that the RNF128 protein was downregulated in invasive urothelial cancer cell lines. Conclusion: Our findings showed that downregulation of RNF128 was correlated with cancer invasiveness and metastasis as well as reduced survival in patients with UTUC and UBUC, identifying RNF128 as a prognostic factor in UC.

miR-375 inhibits the invasion and metastasis of colorectal cancer via targeting SP1 and regulating EMT-associated genes

Accumulating evidence has shown that aberrantly expressed microRNAs (miRNAs) are associated with tumor development and progression. Our previous study found that microRNA-375 (miR-375) was downregulated in colorectal cancer (CRC), but little is known concerning the role of miR-375 and the related mechanism in CRC development. The proliferation, invasion and migration effects were investigated by Cell Counting Kit-8 (CCK-8), colony formation and Transwell assays with or without Matrigel. In addition, candidate target genes were screened and validated by luciferase reporter and western blot assays. In addition, western blot analysis was performed to explore the molecular mechanisms associated with epithelial‑mesenchymal transition (EMT). It was found that miR-375 inhibited proliferation, invasion and migration in DLD1 and HCT8 cells. In addition, miR-375 negatively regulated Sp1 transcription factor (SP1) protein by directly binding to the 3'-untranslated region (3'-UTR). Furthermore, it was found that miR-375 regulated matrix metalloproteinase 2 (MMP2) and EMT-associated genes, E-cadherin, vimentin, snail, N-cadherin and β-catenin. In conclusion, miR-375 inhibited the proliferation, invasion and migration by directly targeting SP1 and regulating MMP2 and EMT-associated genes.

The anti-proliferative effects of type I IFN involve STAT6-mediated regulation of SP1 and BCL6

Type I IFN-induced STAT6 has been shown to have anti-proliferative effects in Daudi and B cells. IFN-sensitive (DS) and IFN-resistant (DR) subclones of Daudi cells were used to study the role of STAT6 in the anti-proliferative activities. Type I IFN significantly increased STAT6 mRNA and protein expression in DS but not DR cells. STAT6 knockdown significantly reduced the sensitivity to IFN in both cell lines. The molecular targets and functional importance of IFN-activated STAT6 were performed by chromatin immunoprecipitation-on-chip (ChIP-on-chip) experiments in type I IFN-treated Daudi cells. Two target genes (Sp1 and BCL6) were selected from the ChIP-on-chip data. IFN-induced STAT6 activation led to Sp1 upregulation and BCL6 downregulation in DS cells, with only minimal effects in DR cells. siRNA inhibition of STAT6 expression resulted in decreased Sp1 and BCL6 mRNA and protein levels in both DS and DR cells. IFN treatment did not increase Sp1 and BCL6 expression in a STAT2-deficient RST2 cell line, and this effect was mitigated by plasmid overexpression of STAT2, indicating that STAT2 is important for STAT6 activation. These results suggest that STAT6 plays an important role in regulating Sp1 and BCL6 through STAT2 to exert the anti-proliferative effects of type I IFN.

The Role of Sulforaphane in Epigenetic Mechanisms, Including Interdependence between Histone Modification and DNA Methylation

Carcinogenesis as well as cancer progression result from genetic and epigenetic changes of the genome that leads to dysregulation of transcriptional activity of genes. Epigenetic mechanisms in cancer cells comprise (i) post-translation histone modification (i.e., deacetylation and methylation); (ii) DNA global hypomethylation; (iii) promoter hypermethylation of tumour suppressor genes and genes important for cell cycle regulation, cell differentiation and apoptosis; and (iv) posttranscriptional regulation of gene expression by noncoding microRNA. These epigenetic aberrations can be readily reversible and responsive to both synthetic agents and natural components of diet. A source of one of such diet components are cruciferous vegetables, which contain high levels of a number of glucosinolates and deliver, after enzymatic hydrolysis, sulforaphane and other bioactive isothiocyanates, that are involved in effective up-regulation of transcriptional activity of certain genes and also in restoration of active chromatin structure. Thus a consumption of cruciferous vegetables, treated as a source of isothiocyanates, seems to be potentially useful as an effective cancer preventive factor or as a source of nutrients improving efficacy of standard chemotherapies. In this review an attempt is made to elucidate the role of sulforaphane in regulation of gene promoter activity through a direct down-regulation of histone deacetylase activity and alteration of gene promoter methylation in indirect ways, but the sulforaphane influence on non-coding micro-RNA will not be a subject of this review.

PC-TraFF: identification of potentially collaborating transcription factors using pointwise mutual information

Background

Transcription factors (TFs) are important regulatory proteins that govern transcriptional regulation. Today, it is known that in higher organisms different TFs have to cooperate rather than acting individually in order to control complex genetic programs. The identification of these interactions is an important challenge for understanding the molecular mechanisms of regulating biological processes. In this study, we present a new method based on pointwise mutual information, PC-TraFF, which considers the genome as a document, the sequences as sentences, and TF binding sites (TFBSs) as words to identify interacting TFs in a set of sequences.

Results

To demonstrate the effectiveness of PC-TraFF, we performed a genome-wide analysis and a breast cancer-associated sequence set analysis for protein coding and miRNA genes. Our results show that in any of these sequence sets, PC-TraFF is able to identify important interacting TF pairs, for most of which we found support by previously published experimental results. Further, we made a pairwise comparison between PC-TraFF and three conventional methods. The outcome of this comparison study strongly suggests that all these methods focus on different important aspects of interaction between TFs and thus the pairwise overlap between any of them is only marginal.

Conclusions

In this study, adopting the idea from the field of linguistics in the field of bioinformatics, we develop a new information theoretic method, PC-TraFF, for the identification of potentially collaborating transcription factors based on the idiosyncrasy of their binding site distributions on the genome. The results of our study show that PC-TraFF can succesfully identify known interacting TF pairs and thus its currently biologically uncorfirmed predictions could provide new hypotheses for further experimental validation. Additionally, the comparison of the results of PC-TraFF with the results of previous methods demonstrates that different methods with their specific scopes can perfectly supplement each other. Overall, our analyses indicate that PC-TraFF is a time-efficient method where its algorithm has a tractable computational time and memory consumption.

The PC-TraFF server is freely accessible at http://pctraff.bioinf.med.uni-goettingen.de/

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-015-0827-2) contains supplementary material, which is available to authorized users.

Fine-scale mapping of the 4q24 locus identifies two independent loci associated with breast cancer risk

BACKGROUND

A recent association study identified a common variant (rs9790517) at 4q24 to be associated with breast cancer risk. Independent association signals and potential functional variants in this locus have not been explored.

METHODS

We conducted a fine-mapping analysis in 55,540 breast cancer cases and 51,168 controls from the Breast Cancer Association Consortium.

RESULTS

Conditional analyses identified two independent association signals among women of European ancestry, represented by rs9790517 [conditional P = 2.51 × 10(-4); OR, 1.04; 95% confidence interval (CI), 1.02-1.07] and rs77928427 (P = 1.86 × 10(-4); OR, 1.04; 95% CI, 1.02-1.07). Functional annotation using data from the Encyclopedia of DNA Elements (ENCODE) project revealed two putative functional variants, rs62331150 and rs73838678 in linkage disequilibrium (LD) with rs9790517 (r(2) ≥ 0.90) residing in the active promoter or enhancer, respectively, of the nearest gene, TET2. Both variants are located in DNase I hypersensitivity and transcription factor-binding sites. Using data from both The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC), we showed that rs62331150 was associated with level of expression of TET2 in breast normal and tumor tissue.

CONCLUSION

Our study identified two independent association signals at 4q24 in relation to breast cancer risk and suggested that observed association in this locus may be mediated through the regulation of TET2.

IMPACT

Fine-mapping study with large sample size warranted for identification of independent loci for breast cancer risk.

Sp1 and the 'hallmarks of cancer'

For many years, transcription factor Sp1 was viewed as a basal transcription factor and relegated to a role in the regulation of so-called housekeeping genes. Identification of Sp1's role in recruiting the general transcription machinery in the absence of a TATA box increased its importance in gene regulation, particularly in light of recent estimates that the majority of mammalian genes lack a TATA box. In this review, we briefly consider the history of Sp1, the founding member of the Sp family of transcription factors. We review the evidence suggesting that Sp1 is highly regulated by post-translational modifications that positively and negatively affect the activity of Sp1 on a wide array of genes. Sp1 is over-expressed in many cancers and is associated with poor prognosis. Targeting Sp1 in cancer treatment has been suggested; however, our review of the literature on the role of Sp1 in the regulation of genes that contribute to the 'hallmarks of cancer' illustrates the extreme complexity of Sp1 functions. Sp1 both activates and suppresses the expression of a number of essential oncogenes and tumor suppressors, as well as genes involved in essential cellular functions, including proliferation, differentiation, the DNA damage response, apoptosis, senescence and angiogenesis. Sp1 is also implicated in inflammation and genomic instability, as well as epigenetic silencing. Given the apparently opposing effects of Sp1, a more complete understanding of the function of Sp1 in cancer is required to validate its potential as a therapeutic target.

Histone deacetylase inhibitor suberoyl bis-hydroxamic acid suppresses cell proliferation and induces apoptosis in breast cancer cells

Suberoyl bis‑hydroxamic acid (SBHA) is a histone deacetylase inhibitor that has shown anticancer activity against numerous types of human cancer. The aim of the current study was to explore the effects of SBHA on the proliferation and apoptosis of breast cancer cells. MCF‑7 breast cancer cells were treated with different concentrations of SBHA and tested for cell viability, apoptosis and gene expression changes. The results showed that SBHA significantly inhibited the proliferation of MCF‑7 cells in a concentration‑dependent manner, as determined using a Cell Counting kit‑8 assay. SBHA‑treated MCF‑7 cells showed G0/G1 cell‑cycle arrest, coupled with elevated expression levels of p21 and p27 proteins. Hoechst 33258 staining revealed cell shrinkage, chromosomal condensation and nuclear fragmentation in MCF‑7 cells treated with SBHA. Flow cytometric analysis of Annexin V‑stained cells showed that SBHA treatment induced apoptotic cell death in a concentration‑dependent manner. Western blot analysis confirmed the upregulation of Bax and the downregulation of Bcl‑2 by SBHA. In conclusion, these results indicate that SBHA exerts cytotoxic effects against human breast cancer cells, which involves the modulation of p21, p27 and Bcl‑2 family proteins, consequently leading to cell‑cycle arrest and apoptosis.

Integrity of the LXXLL motif in Stat6 is required for the inhibition of breast cancer cell growth and enhancement of differentiation in the context of progesterone

Background

Progesterone is essential for the proliferation and differentiation of mammary gland epithelium. Studies of breast cancer cells have demonstrated a biphasic progesterone response consisting of an initial proliferative burst followed by sustained growth arrest. However, the transcriptional factors acting with the progesterone receptor (PR) to mediate the effects of progesterone on mammary cell growth and differentiation remain to be determined. Recently, it was demonstrated that signal transducer and activator of transcription 6 (Stat6) is a cell growth suppressor. Similar to progesterone-bound PR, Stat6 acts by inducing the expression of the G1 cyclin-dependent kinase inhibitors p21 and p27. The possible interaction between Stat6 and progesterone pathways in mammary cells was therefore investigated in the present study.

Methods

ChIP and luciferase were assayed to determine whether Stat6 induces p21 and p27 expression by recruitment at the proximal Sp1-binding sites of the gene promoters. Immunoprecipitation and Western blotting were performed to investigate the interaction between Stat6 and PR-B. The cellular DNA content and cell cycle distribution in breast cancer cells were analyzed by FACS.

Results

We found that Stat6 interacts with progesterone-activated PR in T47D cells. Stat6 synergizes with progesterone-bound PR to transactivate the p21 and p27 gene promoters at the proximal Sp1-binding sites. Moreover, Stat6 overexpression and knockdown, respectively, increased or prevented the induction of p21 and p27 gene expression by progesterone. Stat6 knockdown also abolished the inhibitory effects of progesterone on pRB phosphorylation, G1/S cell cycle progression, and cell proliferation. In addition, knockdown of Stat6 expression prevented the induction of breast cell differentiation markers, previously identified as progesterone target genes. Finally, Stat6 gene expression levels increased following progesterone treatment, indicating a positive auto-regulatory loop between PR and Stat6.

Conclusions

Taken together, these data identify Stat6 as a coactivator of PR mediating the growth-inhibitory and differentiation effects of progesterone on breast cancer cells.

Interleukin-4 regulates lipid metabolism by inhibiting adipogenesis and promoting lipolysis

Long-term cytokine-mediated inflammation is a risk factor for obesity and type 2 diabetes mellitus (T2DM). Our previous studies reveal significant associations between promoter single nucleotide polymorphisms (SNPs) of interleukin (IL)-4 and T2DM, as well as between SNPs in genes encoding IL-4/IL-4 receptor and high density lipoproteins. Our animal study reveals that IL-4 regulates glucose/lipid metabolism by promoting glucose tolerance and inhibiting lipid deposits. The above results strongly suggest the involvement of IL-4 in energy homeostasis. In the present study, we focus on examining the regulatory mechanism of IL-4 to lipid metabolism. Our results show that IL-4 inhibits adipogenesis by downregulating the expression of peroxisome proliferator-activated receptor-γ and CCAAT/enhancer-binding protein-α. Additionally, IL-4 promotes lipolysis by enhancing the activity and translocation of hormone sensitive lipase (HSL) in mature adipocytes, which suggests that IL-4 plays a pro-lipolytic role in lipid metabolism by boosting HSL activity. Our results demonstrate that IL-4 harbors pro-lipolysis capacity by inhibiting adipocyte differentiation and lipid accumulation as well as by promoting lipolysis in mature adipocytes to decrease lipid deposits. The above findings uncover the novel roles of IL-4 in lipid metabolism and provide new insights into the interactions among cytokine/immune responses, insulin sensitivity, and metabolism.

CIZ1 regulates the proliferation, cycle distribution and colony formation of RKO human colorectal cancer cells

Cip1-interacting zinc finger protein 1 (CIZ1) is a nuclear protein that was observed to bind to p21Cip1/Waf1. p21Cip1/Waf1 regulates the cell cycle and is associated with colorectal cancer (CRC) progression. However, the effect of CIZ1 on CRC cells remains unclear. In the present study, CIZ1 was observed to be highly expressed in RKO human CRC cells. Silencing of CIZ1 using small interfering RNA (siRNA) suppressed RKO cell proliferation. Flow cytometric analysis demonstrated that knockdown of CIZ1 decreased the percentage of cells in the S phase and increased the ratio of cells in the G0/G1 phase in parallel with upregulated cell apoptosis. Moreover, the number and size of RKO cell colonies was repressed by knockdown of the CIZ1 gene. These results suggested that CIZ1 may be involved in colon cancer progression by regulating cell proliferation, cell cycle, apoptosis and colony formation. Furthermore, CIZ1‑siRNA may provide a novel tool for CRC investigation and therapy.