STAT3 Knockdown Research Articles

ANGI-08. AN ANNEXIN A2-REGULATED PHENOTYPIC SHIFT IN GLIOMA

Abstract BACKGROUND Malignant glioma has a poor prognosis and is characterized by excessive proliferation, invasion, and angiogenesis. Previously, we established subclones of glioma cell lines with different invasive phenotypes to investigate the mechanisms of invasion in this malignancy. That study revealed annexin A2 (ANXA2) as an activator of angiogenesis and perivascular invasion. Here, we investigated the molecular mechanism of the phenotypic shift in glioma that is induced by ANXA2. METHODS We identified ANXA2 target genes using microarray analyses of our four established cell lines and RNA-seq data from the IVY Glioblastoma Atlas Project. Co-expression was then confirmed in human glioma cells. Additionally, qRT-PCR, immunoblotting, invasion assays, proliferation assays, and tube formation assays were performed to uncover the specific roles of these angiogenic invasion-related genes. Furthermore, we examined survival times and phenotypic shifts in vivo. RESULTS We identified oncostatin M receptor (OSMR) as an ANXA2-target gene using microarray and RNA-seq, and confirmed its expression correlated with ANXA2 in glioma cells. ANXA2-overexpressing glioma cells showed enhanced OSMR expression and STAT3 phosphorylation, while STAT3 knockdown reduced OSMR expression. When ANXA2 was overexpressed in glioma cells, invasion, angiogenesis, proliferation, and epithelial-mesenchymal transition were promoted; however, silencing OSMR attenuated the ANXA2-induced phenotypic shift. In vivo, ANXA2-overexpressing glioma cells shortened the survival time of tumor-bearing mice, whereas OSMR knockdown increased survival times. CONCLUSIONS We analyzed genes whose expression was regulated by ANXA2 in glioma using invasive glioma models. Through this analysis, we identified that ANXA2 and OSMR regulate a phenotypic shift, suggesting that OSMR could be a promising target to treat and prevent glioma invasion.

Antitumor Activity of a Novel Tyrosine Kinase Inhibitor AIU2001 Due to Abrogation of the DNA Damage Repair in Non-Small Cell Lung Cancer Cells.

Class III receptor tyrosine kinase (RTK) inhibitors targeting mainly FLT3 or c-KIT have not been well studied in lung cancer. To identify a small molecule potentially targeting class III RTK, we synthesized novel small molecule compounds and identified 5-(4-bromophenyl)-N-(naphthalen-1-yl) oxazol-2-amine (AIU2001) as a novel class III RKT inhibitor. In an in vitro kinase profiling assay, AIU2001 inhibited the activities of FLT3, mutated FLT3, FLT4, and c-KIT of class III RTK, and the proliferation of NSCLC cells in vitro and in vivo. AIU2001 induced DNA damage, reactive oxygen species (ROS) generation, and cell cycle arrest in the G2/M phase. Furthermore, AIU2001 suppressed the DNA damage repair genes, resulting in the ‘BRCAness’/‘DNA-PKness’ phenotype. The mRNA expression level of STAT5 was downregulated by AIU2001 treatment and knockdown of STAT5 inhibited the DNA repair genes. Our results show that compared to either drug alone, the combination of AIU2001 with a poly (ADP-ribose) polymerase (PARP) inhibitor olaparib or irradiation showed synergistic efficacy in H1299 and A549 cells. Hence, our findings demonstrate that AIU2001 is a candidate therapeutic agent for NSCLC and combination therapies with AIU2001 and a PARP inhibitor or radiotherapy may be used to increase the therapeutic efficacy of AIU2001 due to inhibition of DNA damage repair.

Differential escape mechanisms in cetuximab-resistant head and neck cancer cells

Acquired cetuximab resistance is a challenge for oncologists treating advanced head and neck carcinoma (HNC). While intrinsic cetuximab resistance mechanism in colorectal cancer is known, resistance in HNC is unclear. We established two different cetuximab resistant HNC cell lines by culturing epidermal growth factor (EGFR) expressing UM–SCC–1 and UM–SCC–6 cell lines in the presence of 5 μg/ml cetuximab. We then explored potential mechanisms of resistance. We found that the 2 cell lines developed resistance by different mechanisms. Specifically, we found that UM–SCC–1 resistant cells (UM–SCC–1R) showed enhanced EGF-induced downstream signals while UM–SCC–6 resistant cells (UM–SCC–6R) demonstrated EGF-independent signaling. Global kinase activity (kinomic) profiling revealed unique signaling differences in the two resistant cell lines. However, both of the resistant lines demonstrated increased phospho-serine 727 and total STAT3 expression compared to the parental lines. STAT3 knockdown promoted increased cytotoxicity both in the presence and absence of cetuximab in the resistant lines suggesting that STAT3 may be a common target in cetuximab resistance.

Oncostatin M induces C2C12 myotube atrophy by modulating muscle differentiation and degradation

Oncostatin M (OSM) is a cytokine of the interleukin-6 family and plays a role in various disorders such as cancer and inflammatory diseases, which are often accompanied by skeletal muscle atrophy, or sarcopenia. However, the role of OSM in the regulation of skeletal muscle mass remains to be identified. In this study, we investigated the effect of OSM on C2C12 myotube formation in vitro. C2C12 myoblasts were induced to differentiate into myotubes for 3 days and then treated with OSM for 24 or 48 h. The diameter of differentiated C2C12 myotubes were reduced by 18.7% and 23.3% compared to control cells after treatment with OSM for 24 and 48 h, respectively. The expression levels of MyoD and myogenin were decreased, while those of atrogin-1, CCAAT/enhancer binding protein δ, and OSM receptor were increased in C2C12 myotubes treated with OSM for 24 h compared to control cells. Furthermore, the inhibitory effect of OSM on myotube formation was significantly attenuated by pretreatment with an inhibitor of signal transducer and activator of transcription (STAT) 3 or by knockdown of Stat3. Finally, the OSM-induced changes in the expression levels of MyoD, myogenin, and atrogin-1 were reversed by pretreatment with an inhibitor of STAT3 or by Stat3 knockdown in C2C12 myotubes. In conclusion, OSM induces C2C12 myotube atrophy by inhibiting myogenic differentiation and activating muscle degradation in a STAT3-dependent manner.

Abstract 472: Transcriptome profiling-based identification of prognostic subtypes in glioblastoma: Novel therapeutic strategy targeting invasiveness

Abstract Glioblastoma (GBM) is a lethal tumor, but few biomarkers and molecular subtypes predicting prognosis are available. This study was aimed to identify prognostic subtypes and multi-omics signatures for GBM. We identified 80 genes most associated with GBM prognosis using correlations between gene expression levels and overall survival of patients. The prognostic score of each sample was calculated using these genes, followed by assigning three prognostic subtypes according to prognostic scores. This novel classification was validated in several independent datasets including our patient dataset. Functional annotation revealed that invasion- and cell cycle-related gene sets were enriched in the poor and favorable group, respectively. Therefore, the three subtypes were named as invasive (poor), mitotic (favorable), and intermediate. Interestingly, invasive subtype showed increased invasiveness, and MGMT methylation was enriched in mitotic subtype, indicating the need for different therapeutic strategies according to prognostic subtypes. For clinical convenience, we also identified the genes that best distinguished the invasive and mitotic subtypes. Immunohistochemical staining showed that markedly higher expression of PDPN in the invasive subtype and of TMEM100 in the mitotic subtype. We expect that this comprehensive transcriptome-based classification, with several multi-omics signatures and biomarkers, can improve molecular understanding of GBM. Because invasive subtype showed worse prognosis, we next evaluated invasion-modulating transcriptional regulatory networks for novel therapeutic interventions. After classification of 23 GBM patient-derived tumorspheres into low and high invasion groups, we applied single sample gene set enrichment analysis using transcription factor (TF) target gene sets. According to scores, TFs responsible for low (PCBP1) and high (STAT3 and SRF) invasiveness were identified. Consistently with computational prediction, knockdown of PCBP1 significantly increased invasion area, whereas knockdown of STAT3 or SRF significantly suppressed invasive properties in all tested TSs and mice. Notably, MR images showed coherent patterns with invasion of originated TS, and high invasiveness was associated with poor prognosis in both mice and GBM patients, interrelating these transcriptional regulatory networks, invasive phenotype, and prognosis. We suggest that these transcription factors are deterministic molecules for invasion, which can be utilized as novel drug targets for GBM. Citation Format: Junseong Park, Jin-Kyoung Shim, Seon-Jin Yoon, Se Hoon Kim, Jong Hee Chang, Seok-Gu Kang. Transcriptome profiling-based identification of prognostic subtypes in glioblastoma: Novel therapeutic strategy targeting invasiveness [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 472.

Abstract LB-030: Interferon signaling contributes to prostate cancer drug resistance

Abstract Contrary to the anti-proliferative interferon (IFN) signaling, IFN related DNA damage resistance signature (IRDS) has pro-survival function and is responsible for cancer cell intrinsic therapy resistance. This signature encompasses a subset of STAT1-driven genes that have been associated with breast cancer therapy resistance. Interestingly, our RNAseq analysis of organoids from FACS-sorted Pten/Tp53-null PCa luminal progenitors have revealed a robust IRDS expression. Based on our previous findings that the luminal progenitors display intrinsic resistance to androgen deprivation therapy (ADT), we hypothesized that the IRDS expression might in part account for survival of PCa cells following ADT or genotoxic therapies. Our analysis of human PCa datasets revealed IRDS as a prognostic marker for progression in the TCGA primary PCa cohort (p<0.05). Further, high IRDS-expressing castrate resistance PCa (CRPC) patients in SU2C dataset were enriched for low AR signaling (r= -0.33, p< 0.05). Patients in IRDS-hi cohort showed enrichment for stem cell phenotype and for gene-sets associated with therapy resistance. In line with our analysis of clinical samples, real time PCR, immunofluorescence and western blot analysis of organoid cultures initiated from castration-resistant Pten/Tp53-nulltumor progenitors showed high levels of unphoshorylated STAT1 (U-STAT1) in tumor luminal organoids than WT organoids whereas pSTAT1 (Y701) was not detectable. Similarly, U-STAT1 was overexpressed in Pten/Tp53-null tumor relative to the WT tissue. Knockdown of STAT1 in tumor organoids decreased number of progeny organoids in subsequent generations suggesting either a direct or indirect effect upon self-renewal of luminal tumor stem cells. Altogether, U-STAT1 regulated signaling has pro-survival function in Pten/Tp53-null advanced PCa. Several PDXs originating from metastatic PCa express high levels of U-STAT1 dependent IFN signaling. STAT1 depletion in 5 tested PDXs significantly reduced self-renewing ability of PDX derived organoids, consistent with mouse luminal tumor organoids. Interestingly, STAT1 depletion synergized with sensitivity to chemotherapy ex vivo. These findings indicate that U-STAT1 dependent IFN signaling may contribute to treatment resistance. Overall, our findings suggest U-STAT1 dependent IRDS is correlated with poorly differentiated PCa and IRDS expression in part accounts for intrinsic therapy resistance in prostate cancer. Citation Format: Supreet Agarwal, Kerry McGowen, Fathi Elloumi, Maggie Cam, Mike Beshiri, Eva Corey, Kathleen Kelly. Interferon signaling contributes to prostate cancer drug resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-030.

Abstract 2642: Antisense oligonucleotide-based induction of dominant-negative variants of STAT3 and EGFR in breast and lung cancer cells

Abstract The signal transducer and activator of transcription 3 (STAT3) is linked to multiple cancers, including breast and lung adenocarcinomas, where it is known to activate multiple oncogenic pathways and serve as a bypass mechanism in drug resistance. For example, STAT3 is known to be a driver in some basal-like Triple-negative breast cancers (TNBC) and a resistance mechanism to EGFR inhibitors in non-small cell lung cancer (NSCLC). Thus STAT3 has become an attractive target in cancer therapeutics. A naturally occurring alternative splicing variant, STAT3-beta, is truncated and lacks the C-terminal trans-activation domain. Stat3-beta can act in a dominant negative fashion. We recently demonstrated that splice-switching oligonucleotides (SSOs) can be used to induce a shift in endogenous expression from the abundant, oncogenic STAT3-alpha to the truncated dominant-negative STAT3-beta isoform. This leads to decreased cell viability in triple-negative breast cancer cells and to tumor regression in mice, as compared to full STAT3 knock-down or controls. Our aim was to test a panel of next-generation SSOs in order to evaluate their efficacy in basal-like breast cancer cells, which are typically refractory to tyrosine kinase inhibitors. Based on our previous studies, we generated a panel of optimized SSOs targeting STAT3, and assayed the extent of the STAT3 alpha-to-beta switch, at the RNA and protein level, and at their efficacy at eliciting cell apoptosis in MDA-MB-468 TNBC cells, and identified one which show a 5-10 fold improvement of activity in vitro, compared to our previous leading published compound. The optimized STAT3 SSO sequence was also tested in RTK inhibitor-resistant H1975 non-small cell lung cancer cells and was found to be effective in killing the cancer cells as compared to Stat3 knockdown. We also used a similar antisense approach to induce the expression of a dominant-negative variant of the EGFR and tested in combination with our STAT3 SSO. While both the SSO-induced dominant negative variants of EGFR or STAT3 were able to effectively kill lung cancer cells individually, we observed a marked synergistic increase in inhibition when the two compounds where used in combination. Citation Format: Prasad Subramaniam, Luca Cartegni. Antisense oligonucleotide-based induction of dominant-negative variants of STAT3 and EGFR in breast and lung cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2642.

New STAT3-FOXL2 pathway and its function in cancer cells

BackgroundThe forkhead transcription factor (FOXL2) plays a crucial role in blepharophimosis-ptosis-epicanthus inversus syndrome (BPES), sex determination, ovary growth and development, and cell cycle regulation. Emerging investigations have focused on the downstream targets of FOXL2, while little is known about its upstream regulation.ResultsIn this study, we show that FOXL2 could be regulated by STAT3 in cancer cells and that STAT3 binds to FOXL2 at the 5′- GCCTGATGTTTGTCTTCCCAGTCTGTGGCAA-3′ site using EMSA and ChIP. We further found that knockdown of STAT3 or FOXL2 could significantly induce cancer cell apoptosis, indicating the importance of these two genes in cancer cell growth and apoptosis. Our data also indicated that the increased apoptotic cell rate may be caused by changes in apoptosis-related genes, such as TNF, TRAIL and GnRHR.ConclusionThis study presents a new upstream regulator of FOXL2 and demonstrats that this new STAT3-FOXL2 pathway has an important function in HeLaHeLa cell apoptosis, providing new insights regarding the targeting of FOXL2 for cancer prevention and treatment.

A distinct transcriptional profile in response to endothelial monocyte activating polypeptide II is partially mediated by JAK-STAT3 in murine macrophages.

Macrophages are important responders to environmental changes such as secreted factors. Among the secreted factors in injured tissues, the highly conserved endothelial monocyte activating polypeptide II (EMAP II) has been characterized to limit vessel formation, to be locally expressed near sites of injury labeling it a "find-me" signal, and to recruit macrophages and neutrophils. The molecular mechanisms mediated by EMAP II within macrophages once they are recruited are unknown. In this study, using a model of partially activated, recruited thioglycollate-elicited peritoneal macrophages, a transient, transcription profile of key functional genes in macrophages exposed to EMAP II was characterized. We found that EMAP II-mediated changes were elicited mainly through signal transducer and activator of transcription 3 (STAT3) as evidenced by increased Y705 phosphorylation and changes in activity and upstream of it, Janus associated kinase (JAK)1/2 upstream. Both inhibition of JAK1/2 and knockdown of Stat3 abrogated a subset of genes that are upregulated by EMAP II. Our results identify a rapid EMAP II-mediated STAT3 activation that coincides with altered pro- and anti-inflammatory gene expression in macrophages.

2481-PUB: Oncostatin M Is Involved in Skeletal Muscle Atrophy via the STAT3 Pathway

Recent clinical evidences indicate that sarcopenia is closely related to obesity, type 2 diabetes and atherosclerosis, and mortality risk as well. It has been demonstrated that oncostatin M (OSM), a member of the interleukin-6 family of cytokines, is produced in the adipose tissue and that it promotes adipose tissue inflammation and insulin resistance in obesity. However, the role of OSM in the regulation of skeletal muscle mass remains unknown. In this study, we investigated the effect of OSM on myotube formation of differentiated C2C12 cells in vitro. After C2C12 myoblasts were differentiated into myotubes by a differentiation medium for 72 hours, C2C12 myotubes were treated with OSM for 12 to 48 hours. The diameters of differentiated C2C12 myotubes were reduced by 18.7% and 23.3% compared to the control cells by the treatment with OSM for 24 and 48 hours, respectively. The mRNA expression levels of OSM receptor, atrogin-1, myostatin, and C/EBPδ were significantly increased by 24 hour-treatment with OSM compared to the control cells; while those of myogenin and MyoD were decreased. Moreover, the protein expression of atrogin-1 was increased, myogenin protein level was decreased. Furthermore, OSM phosphorylated STAT3 in differentiated myotubes at 12 and 24 hours. Finally, the inhibitory effect of OSM on the diameter of myotubes was significantly attenuated by the pretreatment with STAT3 inhibitor (C188-9) or by STAT3 knockdown. These in vitro data indicate that OSM contributes to the atrophy of C2C12 myotubes not only by promoting muscle degradation, but also by inhibiting myogenesis via the STAT3 pathway. This study suggests that OSM may regulate skeletal muscle mass in metabolic disorders such as type 2 diabetes. Disclosure Y. Miki: None. T. Morioka: Research Support; Self; Eli Lilly and Company, Merck & Co., Inc., Mitsubishi Tanabe Pharma Corporation, Novartis Pharmaceuticals Corporation, Sanofi K.K., Takeda Pharmaceutical Company Limited. Speaker's Bureau; Self; Astellas Pharma Inc., AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, Merck & Co., Inc., Novo Nordisk Inc., Roche Diagnostics K.K., Sanofi K.K., Sumitomo Dainippon Pharma Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited. Other Relationship; Self; Ono Pharmaceutical Co., Ltd. A. Shioi: None. T. Sakura: None. Y. Kakutani: None. K. Fujimoto: None. H. Uedono: None. K. Mori: Speaker's Bureau; Self; Boehringer Ingelheim International GmbH, Eli Lilly and Company, Mitsubishi Tanabe Pharma Corporation, Ono Pharmaceutical Co., Ltd. T. Shoji: Research Support; Self; Bayer Yakuhin, Ltd., Chugai Pharmaceutical Co., Ltd., Ono Pharmaceutical Co., Ltd. Speaker's Bureau; Self; Kissei Pharmaceutical Co., Ltd., Kowa, Kyowa Hakko Kirin Co., Ltd. M. Emoto: Research Support; Self; Ono Pharmaceutical Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd. Speaker's Bureau; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Eli Lilly and Company, Kowa Pharmaceutical Co., Ltd., Kyowa Hakko Kirin Co., Ltd., Novartis Pharmaceuticals Corporation, Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Sanofi, Sumitomo Dainippon Pharma Co., Ltd., Taisho Toyama Pharmaceutical CO., Ltd., Takeda Pharmaceutical Company Limited. M. Inaba: None.

1990-P: STAT1 Knockdown in CD11c+ Cells Prevents Adipose Tissue Inflammation and Metabolic Dysfunction in Mice on High-Fat Diet

Background: Classically activated M1-like CD11c+ macrophages/dendritic cells (MDCs) are increased in obese adipose tissue (AT) and may contribute to AT inflammation and the development of insulin resistance in obesity. STAT1 is a key transcription factor for MDC polarization into M1-like phenotypes. Here, we examined the role of STAT1 in obesity-induced AT MDC polarization and inflammation and insulin resistance in mice. Methods: Mice with specific knockout (KO) of STAT1 in CD11c+ MDCs were generated by crossbreeding STAT1fl/fl and CD11c-Cre mice. CD11c/STAT1 KO and littermate controls were fed high-fat diet (HFD, 16 weeks) to induce obesity and evaluated for immune cells and browning/beige adipogenesis in perigonadal (pAT) and inguinal (iAT) AT and metabolic functions. Results: Compared to control mice, KO mice on HFD had similar body weight. Analyses of AT immune cells revealed that compared to controls, KO mice had a decrease in M1-like proinflammatory polarization but an increase in M2-like polarization of macrophages and reduced CD8+ T cell number in pAT, and significant increases in the proportion of IL-5+ Th2 cells and eosinophils (CD170+) in pAT and iAT (p<0.05). Furthermore, compared to control mice, KO mice showed significantly increased iAT expression of browning markers (Ucp-1, Cidea, and prdm16) and had increased oxygen consumption rate but lower respiratory exchange ratio, indicating higher energy expenditure and increased fat utilization as energy source. Moreover, KO mice, as compared to controls, had significant reductions in triglyceride content in the liver and skeletal muscle and exhibited improved insulin sensitivity and glucose tolerance examined by insulin and glucose tolerance test (p<0.05). Conclusion: STAT1 plays an important role in obesity-induced MDC M1-like polarization and AT inflammation and contributes to insulin resistance and metabolic dysfunctions in obese mice. Disclosure A. Kalathookunnel Antony: None. X. Perrard: None. Z. Lian: None. J. Perrard: None. C.M. Ballantyne: Consultant; Self; Abbott, Akcea Therapeutics, Amarin Corporation, Amgen Inc., AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, Esperion, Gilead Sciences, Inc., Matinas BioPharma, Merck & Co., Inc., Novartis Pharmaceuticals Corporation, Novo Nordisk Inc., Regeneron Pharmaceuticals, Roche Diagnostic USA, Sanofi. Research Support; Self; Abbott, Akcea Therapeutics, Amarin Corporation, Amgen Inc., Esperion, Novartis Pharmaceuticals Corporation, Regeneron Pharmaceuticals, Roche Diagnostic USA, Sanofi. Other Relationship; Self; Roche Diagnostic USA. H. Wu: None. Funding American Diabetes Association (1-17-IBS-082 to H.W.)

STAT6 knockdown using multiple siRNA sequences inhibits proliferation and induces apoptosis of human colorectal and breast cancer cell lines.

The transcription factor STAT6 is strongly expressed in various tumours and is most highly expressed in human malignant lymphomas and pancreatic, colorectal, prostate and breast cancers. STAT6 is associated with cancer cell proliferation, an increased malignancy and poor prognosis. Thus, techniques aimed at reducing or blocking STAT6 expression may be useful in treating STAT6high cancers. Among these cancers, colorectal and breast cancers represent two of the most common worldwide and their incidence is increasing every year. In 2018, colorectal and breast cancers represented 10.2% and 11.6% of all new cases of cancer diagnosed, respectively. In this study, four proprietary STAT6 specific small interfering RNA (siRNA) sequences were tested in vitro using the human colon adenocarcinoma cell line, HT-29, and the breast/duct carcinoma cell line, ZR-75-1. Decreases in STAT6 mRNA and protein levels were analysed to confirm the transfection was successful and STAT6 knockdown effects were measured by analysing cell proliferation and apoptosis. Results showed that 100nM siRNA concentration was the most effective and, although all individual sequences were capable of significantly inhibiting cell proliferation, STAT6 siRNA sequences 1 and 4 had the largest effects. STAT6 silencing also significantly induced apoptotic events. In conclusion, these results demonstrate that STAT6 siRNA sequences are capable of inhibiting proliferation of and inducing apoptosis of HT-29 colorectal cancer cells and ZR-75-1 breast cancer cells, halving the number of cancer cells in a short period of time. These experiments will be repeated in other STAT6high cancers in vitro, and animal studies in immunocompromised mice have been planned using xenografts of STAT6-expressing human colorectal and breast cancer cells. The STAT6 siRNA sequences therefore represent a potential treatment for STAT6high colorectal and breast cancers and a wide variety of other STAT6-expressing cancers.

Organic dust induces inflammatory gene expression in lung epithelial cells via ROS-dependent STAT-3 activation.

Exposure to dust in agricultural and animal environments, known as organic dust, is associated with the development of respiratory symptoms and respiratory diseases. Inflammation is a key feature of lung pathologies associated with organic dust exposure, and exposure to organic dust induces the expression of several immune and inflammatory mediators. However, information on transcription factors and cellular and molecular mechanisms controlling the production of immune and inflammatory mediators induced by organic dust is limited. In this study, we have identified STAT-3 as an important transcription factor controlling the induction of expression of immune and inflammatory mediators by poultry dust extracts in airway epithelial cells and in mouse lungs and delineated the cellular pathway for STAT-3 activation. Poultry dust extract activated STAT-3 phosphorylation in Beas2B and normal human bronchial epithelial cells and in mouse lungs. Chemical inhibition and siRNA knockdown of STAT-3 suppressed induction of immune and inflammatory mediator expression. Antioxidants suppressed the increase of STAT-3 phosphorylation induced by poultry dust extract indicating that oxidative stress [elevated reactive oxygen species (ROS) levels] is important for the activation. Chemical inhibition and siRNA knockdown experiments demonstrated that STAT-3 activation is dependent on the activation of nonreceptor tyrosine-protein kinase 2 (TYK2) and epidermal growth factor receptor (EGFR) tyrosine kinases. Our studies show that poultry dust extract controls the induction of immune and inflammatory mediator expression via a cellular pathway involving oxidative stress-mediated STAT-3 activation by TYK2 and EGFR tyrosine kinases.

Enhancement of cortisol-induced SAA1 transcription by SAA1 in the human amnion.

Our previous studies have demonstrated that human fetal membranes are capable of de novo synthesis of serum amyloid A1 (SAA1), an acute phase protein of inflammation, wherein SAA1 may participate in parturition by inducing a number of inflammation mediators including interleukine-1β, interleukine-6 and prostaglandin E2. However, the regulation of SAA1 expression in the fetal membranes remains largely unknown. In the current study, we examined the regulation of SAA1 expression by cortisol, a crucial steroid produced locally in the fetal membranes at parturition, and the interaction between cortisol and SAA1 in the feed-forward induction of SAA1 expression in human amnion fibroblasts. Results showed that cortisol-induced SAA1 expression in a concentration-dependent manner, which was greatly enhanced by SAA1 despite modest induction of SAA1 expression by itself. Mechanism studies revealed that the induction of SAA1 expression by cortisol and SAA1 was blocked by either the transcription factor STAT3 antagonist AZD0530 or siRNA-mediated knockdown of STAT3. Furthermore, cortisol- and SAA1-induced STAT3 phosphorylation in a sequential order with the induction by SAA1 preceding the induction by cortisol. However, combination of cortisol and SAA1 failed to further intensify the phosphorylation of STAT3. Consistently, cortisol and SAA1 increased the enrichment of STAT3 at the SAA1 promoter. Taking together, this study has demonstrated that cortisol and SAA1 can reinforce each other in the induction of SAA1 expression through sequential phosphorylation of STAT3. The enhancement of cortisol-induced SAA1 expression by SAA1 may lead to excessive SAA1 accumulation resulting in parturition-associated inflammation in the fetal membranes.

Activation of STAT1 by the FRK tyrosine kinase is associated with human glioma growth.

Glioma is a highly aggressive and lethal brain tumor. Signal transducers and activators of transcription (STAT) pathway are widely implicated in glioma carcinogenesis. Our previous study found that the Fynrelated kinase (FRK) gene, plays as a tumor suppressor in the development and progression of glioma. This study aimed to investigate the role of FRK in the activation pathway of STATs and its effect on the growth of glioma. The U251 and U87 cells with stable FRK overexpression were generated by lentivirus technique. The effects of FRK on the related proteins of STAT signaling pathway were detected by western blotting. Coimmunoprecipitation was used to detect the association of FRK and STAT1. The effects of STAT1 on the proliferation of glioma cells were detected by CCK8 or Edu cell proliferation assays. The expressions and correlation of FRK and p-STAT1 in glioma tissues were detectd by western blotting or immunohistochemistry. The effect of FRK on the growth of glioma was investigated in vivo mouse model. The level of p-JAK2 and p-STAT1 increased after FRK overexpression, while they decreased after FRK downregulation both in U251 and U87 cells. However, FRK had no effect on STAT3 phosphorylation. FRK-induced STAT1 activation was not dependent on JAK2. FRK associated with STAT1, induced STAT1 nuclear translocation and regulated the expressions of STAT1-related target genes. STAT1 overexpression suppressed the proliferation of glioma cells. In contrast, STAT1 knockdown by siRNA promoted glioma cell growth. Importantly, down-regulation of STAT1 partially attenuated FRK-induced growth suppression. The clinical sample-based study indicated that the expression of FRK was significantly correlated with the expression of p-STAT1. FRK significantly inhibited glioma tumor growth in vivo. Our findings highlighted a critical role of FRK in tumor suppression ability through promoting STAT1 activation, and provided a potential therapeutic target for glioma.

A role for polycystin-1 and polycystin-2 in neural progenitor cell differentiation.

Polycystin-1 (PC1) and polycystin-2 (PC2) are transmembrane proteins encoded by the Pkd1 and Pkd2 genes, respectively. Mutations in these genes are causative for the development of autosomal-dominant polycystic kidney disease. A prominent feature of this disease is an unbalanced cell proliferation. PC1 and PC2 physically interact to form a complex, which localizes to the primary cilia of renal epithelial cells. Recently, PC1 and PC2 have also been described to be present in primary cilia of radial glial cells (RGCs) and to contribute to the planar cell polarity of late RGCs and E1 ependymal cells. As neural progenitor cells (NPCs), early RGCs have to balance proliferation for expansion, or for self-renewal and differentiation to generate neurons. It is not known whether the polycystins play a role in this process. Here, we show that PC1 and PC2 are expressed in RGCs of the developing mouse cerebral cortex during neurogenesis. Loss-of-function analysis and cell-based assays reveal that a reduction of PC1 or PC2 expression leads to increased NPC proliferation, while the differentiation to neurons becomes impaired. The increased NPC proliferation is preceded by enhanced Notch signaling and accompanied by a rise in the number of symmetric cell divisions. The transcription factor STAT3 seems to be mechanistically important for polycystin signaling in NPCs as either STAT3 knockdown or inhibition of STAT3 function abrogates the increased proliferation driven by reduced polycystin expression. Our findings indicate that PC1 and PC2 are critical for maintaining a balance between proliferation and differentiation of NPCs.

Therapeutic Targeting of Stat3 Using Lipopolyplex Nanoparticle-Formulated siRNA in a Syngeneic Orthotopic Mouse Glioma Model.

Glioblastoma (GBM), WHO grade IV, is the most aggressive primary brain tumor in adults. The median survival time using standard therapy is only 12–15 months with a 5-year survival rate of around 5%. Thus, new and effective treatment modalities are of significant importance. Signal transducer and activator of transcription 3 (Stat3) is a key signaling protein driving major hallmarks of cancer and represents a promising target for the development of targeted glioblastoma therapies. Here we present data showing that the therapeutic application of siRNAs, formulated in nanoscale lipopolyplexes (LPP) based on polyethylenimine (PEI) and the phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), represents a promising new approach to target Stat3 in glioma. We demonstrate that the LPP-mediated delivery of siRNA mediates efficient knockdown of Stat3, suppresses Stat3 activity and limits cell growth in murine (Tu2449) and human (U87, Mz18) glioma cells in vitro. In a therapeutic setting, intracranial application of the siRNA-containing LPP leads to knockdown of STAT3 target gene expression, decreased tumor growth and significantly prolonged survival in Tu2449 glioma-bearing mice compared to negative control-treated animals. This is a proof-of-concept study introducing PEI-based lipopolyplexes as an efficient strategy for therapeutically targeting oncoproteins with otherwise limited druggability.

The FGFR1 V561M Gatekeeper Mutation Drives AZD4547 Resistance through STAT3 Activation and EMT

FGFR1 has been implicated in numerous cancer types including squamous cell lung cancer, a subset of non-small cell lung cancer with a dismal 5-year survival rate. Small-molecule inhibitors targeting FGFR1 are currently in clinical trials, with AZD4547 being one of the furthest along; however, the development of drug resistance is a major challenge for targeted therapies. A prevalent mechanism of drug resistance in kinases occurs through mutation of the gatekeeper residue, V561M in FGFR1; however, mechanisms underlying V561M resistance to AZD4547 are not fully understood. Here, the cellular consequences of the V561M gatekeeper mutation were characterized, and it was found that although AZD4547 maintains nanomolar affinity for V561M FGFR1, based on in vitro binding assays, cells expressing V561M demonstrate dramatic resistance to AZD4547 driven by increased STAT3 activation downstream of V561M FGFR1. The data reveal that the V561M mutation biases cells toward a more mesenchymal phenotype, including increased levels of proliferation, migration, invasion, and anchorage-independent growth, which was confirmed using CyTOF, a novel single-cell analysis tool. Using shRNA knockdown, loss of STAT3 restored sensitivity of cancer cells expressing V561M FGFR1 to AZD4547. Thus, the data demonstrate that combination therapies including FGFR and STAT3 may overcome V561M FGFR1-driven drug resistance in the clinic. IMPLICATIONS: The V561M FGFR1 gatekeeper mutation leads to devastating drug resistance through activation of STAT3 and the epithelial-mesenchymal transition; this study demonstrates that FGFR1 inhibitor sensitivity can be restored upon STAT3 knockdown.

RETRACTED ARTICLE: Genistein inhibits stemness of SKOV3 cells induced by macrophages co-cultured with ovarian cancer stem-like cells through IL-8/STAT3 axis

BackgroundRecent studies showed that macrophages co-cultured with ovarian cancer stem-like cells (OCSLCs) induced SKOV3 cell stemness via IL-8/STAT3 signaling. Genistein (GEN) demonstrates chemopreventive activity in inflammation-associated cancers. The present study aimed to examine whether and if GEN inhibits the stemness of SKOV3 and OVCA-3R cells induced by co-culture of THP-1 macrophages and SKOV3-derived OCSLCs.MethodsThe co-culture was treated with or without different concentrations (10, 20, and 40 μmol/L) of GEN for 24 h. Depletion or addition of IL-8 in Co-CM and knockdown or overexpression of STAT3 in THP-1 macrophages was performed to demonstrate the possible associated mechanisms. The combined effects of GEN and STAT3 knockdown were examined with the nude mouse modle by co-injection of SKOV3-derived OCSLCs with THP-1 macrophages.ResultsOur results showed that GEN down-regulated CD163 and p-STAT3 expression of THP-1 macrophage, decreased the levels of IL-10, increased the levels of IL-12 and nitric oxide (NO) in the conditioned medium, and reduced the clonogenic and sphere-forming capacities and the expression of CD133 and CD44 in SKOV3 cells induced by co-culture of THP-1 macrophages and OCSLCs in a dose-dependent manner. Moreover, depletion or addition of IL-8 enhanced or attenuated the effect of GEN. Additionally, knockdown or overepression of STAT3 in THP-1 macrophages potentiated or attenuated the inhibitory effects of GEN. Importantly, STAT3 overexpression retrieved the effects of IL-8 combined with GEN depletion on M2 polarization of THP-1 macrophages and stemness of SKOV3 cells induced by co-culture. The combination of GEN and STAT3 knockdown cooperatively inhibited the growth of tumors co-inoculated with OCSLCs/THP-1 macrophages in nude mice in vivo through blocking IL-8/STAT3 signaling.ConclusionsIn summary, our findings suggested that GEN can inhibit the increased M2 polarization of macrophages and stemness of ovarian cancer cells by co-culture of macrophages with OCSLCs through disrupting IL-8/STAT3 signaling axis. This assisted GEN to be as a potential chemotherapeutic agent in human ovarian cancer.

STAT3 enhances the constitutive activity of AGC kinases in melanoma by transactivating PDK1

BackgroundThe PI3K/Akt and the STAT3 pathways are functionally associated in many tumor types. Both in vitro and in vivo studies have revealed that either biochemical or genetic manipulation of the STAT3 pathway activity induce changes in the same direction in Akt activity. However, the implicated mechanism has been poorly characterized. Our goal was to characterize the precise mechanism linking STAT3 with the activity of Akt and other AGC kinases in cancer using melanoma cells as a model.ResultsWe show that active STAT3 is constitutively bound to the PDK1 promoter and positively regulate PDK1 transcription through two STAT3 responsive elements. Transduction of WM9 and UACC903 melanoma cells with STAT3-small hairpin RNA decreased both PDK1 mRNA and protein levels. STAT3 knockdown also induced a decrease of the phosphorylation of AGC kinases Akt, PKC, and SGK. The inhibitory effect of STAT3 silencing on Akt phosphorylation was restored by HA-PDK1. Along this line, HA-PDK1 expression significantly blocked the cell death induced by dacarbazine plus STAT3 knockdown. This effect might be mediated by Bcl2 proteins since HA-PDK1 rescued Bcl2, Bcl-XL, and Mcl1 levels that were down-regulated upon STAT3 silencing.ConclusionsWe show that PDK1 is a transcriptional target of STAT3, linking STAT3 pathway with AGC kinases activity in melanoma. These data provide further rationale for the ongoing effort to therapeutically target STAT3 and PDK1 in melanoma and, possibly, other malignancies.