Signal Transducer And Activator Of Transcription 3 Gene Expression Research Articles

Response to treatment of murine schistosomiasis with recombinant IL-22 under different circadian timing

ABSTRACT Response to treatment usually depends on the time of drug administration. Interleukin-22 (IL-22) is known for its protective effect against liver injury. Therefore, the aim was to study the effectiveness of the IL-22 treatment at different circadian timing on S. mansoni-infected mice. Mice grouping included; control group, mice infected with cercariae, and IL-22-treated groups. Treatment with IL-22 (0.36 µg/kg) was performed on infected mice either at 7 am, or 7 pm. Hepatic granuloma index (GI), levels of tumor necrosis factor-α (TNF-α), interleukin-17 (IL-17), IL-22, and immunoglobulin E (IgE) were measured. In addition, hepatic expressions of signal transducer and activator of transcription 3 (STAT3) and β-catenin genes were estimated. Infection with S. mansoni increased pro-inflammatory parameters, STAT3, and β-catenin mRNA significantly (P < 0.05) compared to the control group. IL-22 groups showed a significant reduction (P < 0.05) in liver GI, TNF-α, and β-catenin mRNA compared to infected mice. Moreover, it enhanced STAT3 gene expression (P < 0.05). IL-22 administration at 7 am reduced GI, IL-17, and IgE levels significantly (P < 0.05) compared to 7 pm values. The conclusion, IL-22 might have an immunotherapeutic effect. Its administration at 7 am was more effective in reducing hepatic granuloma and IgE, but further studies are needed to support these findings.

Poly(rC) Binding Protein 1 Represses the Translation of STAT3 through 5' UTR.

Signal transducer and activator of transcription 3 (STAT3) is an oncogene and frequently overexpressed in cancers. However, the regulatory mechanisms of STAT3 expression are not fully understood. Poly(rC)-binding protein1 (PCBP1) is an RNA-binding protein that regulates mRNA stability, splicing, and translation. PCBP1 is a tumor suppressor and can inhibit the translation of several oncogenic genes. We aimed to understand the regulatory mechanisms of STAT3 expression. The 5' UTR or 3' UTR regions of the human STAT3 gene were inserted upstream or downstream of the green fluorescent gene (GFP), respectively, which were used as reporter systems to analyze the inhibitory effects of PCBP1 on the STAT3 gene expression. The deletion and point mutation in 5' UTR were used to search the essential regulatory sequences of the translation inhibition. The mutations of PCBP1 protein were analyzed in the cBioPortal online service. The effects of mutated PCBP1 proteins on STAT3 expression, cancer cell proliferation, and colony formation were analyzed in oral squamous cell carcinoma (OSCC) cell lines. PCBP1 inhibits mRNA translation through a motif in the 5' UTR of STAT3. Moreover, we found two leucine residues (Leu100 and Leu102) of PCBP1 protein frequently mutated in cancers. These mutations abolished the inhibition function of PCBP1 on STAT3 translation. Surprisingly, in contrast to wild-type PCBP1 protein, these mutations can promote the growth and colony formation of cancer cells. Overall, we demonstrate that PCBP1 can inhibit the expression of STAT3 through its 5' UTR, and two leucine residues of PCBP1 protein are essential for its functions.

Prognostic significance of STAT3 gene expression in patients with glioblastoma tumors: a study from Western India

ObjectiveGlioblastoma Multiforme (GBM), a devastating the most common primary malignant intracranial brain tumors. In India, the incidence of this malignancy is escalating, however, there are very few studies on this tumor entity from Indian population. The present study sought to investigate the prevalence and prognostic significance of Signal Transducer and Activator of Transcription 3 (STAT3) gene expression in GBM patients from Western India.MethodSTAT3 gene expression using real-time PCR was detected in total 55 GBM patients. The impact of STAT3 aberrant expression on progression-free survival (PFS) and overall (OS) was analysed using univariate and multivariate survival analysis. The data were analysed using SPSS statistical software and p value ≤0.05 was considered as significant.ResultsThe aberrant STAT3 expression was found in 85% (47/55) of patients with -1.12 fold change down-regulation in 49% (23/47) and 3.36 fold change up-regulation was noted in 51% (24/47) of patients. In wild type IDH tumors (n=30), down regulation and up regulation of STAT3 was noted in 63% and 27% of patients, respectively, whereas, for IDH mutant GBM tumors (n=25), the incidence of low expression and high expression of STAT3 was noted in 16% and 68% of patients, respectively. Thus, we found that incidence of STAT3 down regulation was significantly high in patients with IDH wild type tumors, whereas, in IDH mutant GBM tumors, the incidence of up-regulated STAT3 was significantly high (P=0.021, χ2=12.81, r=+0.310). In Kaplan-Meier univariate survival analysis, a part from age (P=0.006), tumor location (P=0.025), and KPS score (P=0.002), co-detection of STAT3 up regulation and presence of IDH mutation (P=0.030) remained significant prognostic factors for PFS and OS. In multivariate survival analysis also, co-detection of STAT3 high expression and presence of IDH mutation remained independent prognosticators for PFS (HR=6.45, 95% CI=1.32-31.40, P=0.021) and OS (HR=8.69, 95% CI=1.66-45.51, P=0.010).ConclusionFor GBM tumors, STAT3 up-regulation and presence of IDH mutations together predicts better survival. This reflects unique molecular etiology for GBM patients. Therefore, they would be useful in the future for targeted therapy and for clinicians they would be useful for better patient management. However, study on a larger sample size is required for validation.

MiR-125b Inhibits Cell Proliferation and Induces Apoptosis in Human Colon Cancer SW480 Cells via Targeting STAT3.

Colon cancer is one of the most common types of cancer worldwide. Multiple studies have unveiled the key role of microRNAs (miRNAs) in the development of various types of cancer. However, the mechanism of action of miR-125b in the development and progression of colon cancer remains unknown. In this study, we explored the association of miR-125b and signal transducer and activator of transcription 3 (STAT3) and its role in the proliferation and apoptosis of SW480 colon cancer cells. The miR-125b expression in NCM460, SW480, HT29, and HCT8 cells was detected using quantitative real-time polymerase chain reaction (qRT-PCR). SW480 cells were transfected with lentiviruses of GFP-miR-125b and GFP-NC to establish a stable miR-125b overexpression colon cancer cell model and a control model. The targeting relationship between miR-125b and STAT3 was analyzed using bioinformatics and verified by the dual-luciferase reporter gene assay. Cell proliferation and apoptosis were assessed using the Cell Counting Kit-8 assay and TUNEL staining. The expression levels of STAT3, Bcl-2, and Bax were analyzed using Western blot analysis. It was found that the relative mRNA expression of miR-125b was decreased in SW480, HT29, and HCT8 cells compared with that in NCM460 cells (P<0.05). The luciferase reporter gene assay confirmed that miR-125b downregulated the STAT3 gene expression (P<0.05). Overexpression of miR-125b inhibited proliferation and promoted apoptosis in SW480 colon cancer cells and was accompanied by upregulated Bax expression and downregulated Bcl-2 expression (P<0.05). Re-expression of STAT3 promoted cell proliferation and inhibited cell apoptosis, whereas Bcl-2 expression increased, and Bax expression decreased (P<0.05). The miR-125b regulates the expression of Bax and Bcl-2 by downregulating the expression of STAT3, thereby inhibiting proliferation and inducing apoptosis of SW480 colon cancer cells.

Dietary therapeutic treatment of renal carcinoma cell lines by down-regulating cFlip, Mcl-1, Bcl-XL and STAT3 gene expression under the influence of up-regulated Bax and intrinsic apoptotic pathway

Renal cell carcinoma (RCC) is a lethal genitourinary cancer and accounts 3% of total cancers worldwide. Various pleiotropic cytokines, i.e activator of signal transducer and activator of transcription 3 (STAT3), Cellular FLICE (FADD-like IL-1β-converting enzyme)-inhibitory protein (c-FLIP) and interleukin-6 (IL-6) could act to block the process of apoptosis in renal cancinoma cells, trigering its growth and proliferation. Their over-expression could activate several anti-apoptotic factors, hence it is important to block or down-regulate such factors in order to activate apoptosis in cancer cells. Up till now, several chemo and radiotherapies are being considered to combat renal carcinoma cells; however, there is a strong need to get some dietary therapeutic treatment. Hence, this study has used gastrointestinal digests of preserved eggs (GID-PE) for the apoptosis of Caki-1, ACHN and 786-O cells lines, in order to get insights about apoptosis in their mitochondrial pathway before and after treatment with (GID-PE). Moreover, changes in morphology accompanied by apoptosis analysis with different treatments have been carried out. Furthermore, ELISA analysis and mRNA expression of certain pro-inflammatory and anti-inflammatory cytokines were determined before and after treatment with GID-PE. Furthermore, the specific anti-apoptotic genes, i.e cFlip, Mcl-1, Bcl-XL and STAT3 were examined for their down-regulated expression after different treatments with GID-PE. Moreover, Bax expression acting as a pro-apoptotic gene was up-regulated up to some extent after treatments with GID-PE. Hence, GID-PE was confirmed to give anti-inflammatory effects in renal carcinoma cells could be used as health beneficial food product with anti-cancer properties.

Alteration of &lt;i&gt;STAT3&lt;/i&gt; gene expression in psoriasis treatment

Introduction. Psoriasis is a typical complex multigenic and multifactorial disease with heterogeneous genetic heredity, which requires the interaction of genes both with each other and with environmental factors. STAT3 (Signal Transducer and Activator of Transcription 3) has only recently been considered a key player in the development and pathogenesis of psoriasis and psoriatic inflammatory conditions.Aim of the study. To study the expression of the STAT3 gene in the affected part of the skin of psoriasis patients in relation to the visually unaffected part. To study the change in the STAT3 gene expression level in psoriasis-affected skin as compared to nonaffected skin in patients before and after treatment with low-level laser radiation at a wavelength of 1.27 pm.Materials and methods. The study involved 12 psoriasis patients. Biopsies from the unaffected skin were taken at a distance of about 3 cm from the affected skin. Real-time PCR analysis was performed.Results and discussion. The expression of the STAT3 gene was quantitatively measured using RT-PCR in the affected part of the skin of psoriasis patients compared to the visually unaffected part of the skin of the same patients before and after treatment with low-level laser radiation with a wavelength of 1.27 gm (short-wave infrared). As a result of the study, an increase in the expression of the STAT3 gene in the affected part of the skin of psoriasis patients of an average of 3.96 ± 2 times was experimentally shown. A decrease in gene expression was observed in psoriasis affected skin compared to samples of non-affected areas. After treatment of patients with low-level laser radiation, a significant reduction in the expression of the overexpressed STAT3 gene to 1.75 ± 0.5 times was observed.Conclusions. The transcription activity of the STAT3 gene can be an indicator of the efficacy of psoriasis treatment at the molecular level and can also be a new therapeutic target.

STAT3 gene polymorphism in chronic obstructive pulmonary disease.

The aim of this study was to explore the correlation between rs8069115, rs41289087, and rs11079042 polymorphisms of the signal transducer and activator of transcription 3 (STAT3) gene and chronic obstructive pulmonary disease (COPD). A total of 200 patients diagnosed with COPD were enrolled in the disease group. Meanwhile, 200 normal subjects were selected as the control group. Peripheral blood was collected from subjects in the disease group and control group. Subsequently, nucleated cells were isolated for determination of STAT3 gene polymorphisms. Quantitative Polymerase Chain Reaction (qPCR) was utilized to detect the expression level of STAT3. Samples from 12 patients with differences in STAT3 haplotypes and 12 cases with no difference were collected and treated with transcriptome sequencing to analyze pathways enriched with differentially expressed genes. There were statistically significant differences in allele distributions at rs8069115 between the disease group and control group (p=0.000), and the allele frequency of G was higher in disease group. Genotype distributions of rs8069115 (p=0.000) and rs41289087 (p=0.000) of the STAT3 gene in disease group were significantly different in comparison with the control group. The frequency of rs8069115 GG genotype was remarkably higher, while the frequency of rs41289087 TG genotype was lower in the disease group (p<0.05). In addition, compared with the control group, the distributions of the dominant model (p=0.002) and recessive model (p=0.004) of rs8069115 of the STAT3 gene were markedly different in the disease group. A significantly higher frequency of dominant model GG+GA and lower frequency of recessive model GA+AA were observed at rs8069115 in the disease group (p<0.05). Moreover, the haplotype distributions of AGC (p=0.002), ATC (p=0.001), GTA (p=0.010), and GTC (p=0.035) at rs8069115, rs41289087, and rs11079042 were different between the disease group and control group. Besides, rs8069115 locus and rs11079042 locus were linked to each other (D'=0.523). There was a remarkable association between rs11079042 polymorphism of the STAT3 gene and gene expression (p<0.05). STAT3 was highly expressed in patients with genotype CC (p<0.05). Furthermore, changes in transcriptome levels among different haplotype populations (haplotype with different distributions vs. haplotype with no difference in distribution) were analyzed. The results demonstrated that multiple pathways, such as ECM-receptor interactions, cell cycle checkpoints, and protein processing were notably enriched (p<0.05). According to our results, we confirmed that the polymorphisms (rs8069115, rs41289087, and rs11079042) of STAT3 gene are noticeably correlated with the occurrence and progression of COPD.

MiR-21-5p protects hippocampal neurons of epileptic rats via inhibiting STAT3 expression.

Epilepsy is a common chronic neurological disorder worldwide. To investigate the effects of miR-21-5p and signal transducer and activator of transcription-3 (STAT3) expressions on the apoptosis of hippocampal neurons in epileptic rats. We created a rat model of epilepsy and examined the relationship between miR-21-5p and STAT3 using a bioinformatics website and dual the luciferase reporter (DLR) assay. Real-time quantitative polymerase chain reaction (RT-qPCR) and western blot were used to detect the expression levels of miR-21-5p and STAT3 in hippocampal neurons as well as the protein expression levels of cleaved caspase-3, Bax and Bcl-2, which were related to apoptosis of hippocampal neuron. The apoptosis and survival of hippocampal neurons were detected using TUNEL and Nissl staining. Expressions of inflammatory factors interleukin (IL)-6 and tumor necrosis factor α (TNF-α) in serum were examined with enzyme-linked immunosorbent assay (ELISA). miR-21-5p can bind to STAT3. Compared with the miR-21-5p inhibitor negative control (NC) group, the expression levels of caspase-3 and Bax were higher and the expression level of Bcl-2 was lower in the miR-21-5p inhibitor group, whereas the caspase-3 and Bax levels were lower and Bcl-2 level was higher in the si-STAT3 (interfering STAT3 gene expression by transfecting small interfering RNA) group (all p < 0.05). Treatment with miR-21-5p inhibitor can lead to significant loss and apoptosis of hippocampal neurons, while interfering with STAT3 expression can reduce the loss and apoptosis of the neurons (all p < 0.05). Compared with the miR-21-5p inhibitor NC group, the level of IL-6 was lower in the si-STAT3 group and higher in the miR-21-5p inhibitor group (both p < 0.05). miR-21-5p can inhibit STAT3 expression and reduce apoptosis and loss of hippocampal neurons and IL-6 level, thereby achieving protective effects on hippocampal neurons of epileptic rats.

Abstract 844: β IV -spectrin Regulates Cardiac Fibroblast Phenotype, Fibrosis, and Cardiac Function

Increased fibrosis is associated with cardiac dysfunction and arrhythmias. Activation of quiescent cardiac fibroblasts (CFs) occurs in response to injury although the underlying mechanistic pathways remain unclear. The cytoskeletal protein β IV -spectrin has been shown to control targeting and activity of the multifunctional transcription factor Signal Transducer and Activator of Transcription 3 (STAT3) for maladaptive remodeling. The mechanism linking spectrin dysfunction to altered STAT3 signaling, fibrosis, and function remains unknown. The objective of this study was to investigate the role of stress-induced disruption of β IV -spectrin/STAT3 complex in modulating CF phenotype, fibrosis, and cardiac function. Cardiac function (echocardiography) and fibrosis (Masson’s trichrome) were evaluated in adult wildtype (WT) and qv 4J mice expressing truncated β IV -spectrin lacking STAT3 interaction. A subset of WT mice were subjected to 6 wks of transaortic constriction (TAC) to induce heart failure. From these groups, CFs were isolated from ventricles and analyzed for STAT3 localization, gene expression, and activity. CFs were treated with selective STAT3 inhibitor S3I-201 (100μM) or transfected for 72 hrs with β IV -spectrin fragment from repeat 10 to C-terminus (β IV,10-C , contains STAT3 binding motif). Ejection fraction was decreased in qv 4J and WT TAC relative to WT baseline (49.5±0.85% vs 34.9±2.2% vs 63.2±0.60% respectively, p&lt;0.05, N=5. Ventricular fibrosis was augmented in qv 4J and WT TAC compared to WT baseline (2.4±0.09% vs 3.2±0.25% vs 0.48±0.01% respectively, p&lt;0.05, N=5). qv 4J CFs showed STAT3 mislocalization (49.7±10.7% nuclear accumulation vs 5.3±.1.8% in WT, p&lt;0.05, N=5) with higher STAT3 transcriptional activity (2.6±0.17-fold increase over WT, p&lt;0.05, N=9). In parallel, qv 4J CFs displayed elevated expression of fibrotic genes associated with CF activation. At the functional level, qv 4J CFs showed increased proliferation (1.9±0.19-fold increase over WT at 24 hrs, p&lt;0.05, N=4). STAT3 inhibition with S31-201 or transfection with β IV,10-C normalized gene expression and proliferation in qv 4J CFs compared to WT. These studies identify a requirement of β IV -spectrin for normal STAT3 signaling and quiescent phenotype in CFs.

Abstract 2521: STAT3 is a central regulator of proliferation, invasion and metabolism in GBM tumor initiating cells

Abstract Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor. Currently, treatment for GBM involves surgical resection, chemotherapy, and radiation, resulting in a median survival of 15 months. This poor outcome highlights the need for improved therapeutic approaches to treat GBM patients. The signal transducer and activator of transcription 3 (STAT3) pathway is abnormally active in GBM, primarily in the mesenchymal subtype of GBM. STAT3 regulates various cellular processes including: proliferation, invasion and resistance to therapy. The Weiss lab has established a large collection of brain tumor initiating cell (BTIC) lines derived from GBM patients. These GBM BTIC lines are used to model the subpopulation of cells that are predicted to be the source of resistance and recurrence following treatment. Here, we are focused on the role of STAT3 as a central regulator of proliferation, invasion and metabolism in GBM BTIC lines. We show that activation of the STAT3 pathway using the ligand oncostatin M (OSM) or by stably expressing a constitutively active STAT3 mutant (STAT3C) in GBM BTIC lines leads to an increase in proliferation. STAT3 is known to regulate the expression of multiple matrix metalloproteinases (MMPs) that promote invasion. Using time-lapse imaging of 3D sphere invasion into matrigel, we observed that JAK2 (an activator of STAT3) and direct STAT3 inhibitors decrease invasion of GBM BTICs. Our analysis of gene expression data available from The Cancer Genome Atlas (TCGA) demonstrates that a glutamine metabolism gene expression signature correlates inversely with a STAT3 gene expression signature in GBM patient samples. Conversely, similar analysis reveals that a high glycolysis gene expression signature correlates with a high STAT3 gene expression signature. We hypothesize that targeting the STAT3 pathway will decrease proliferation and invasion while simultaneously sensitizing GBM BTIC lines to inhibition of glutamine metabolism. Glutaminase (GLS) is the first enzyme to act on glutamine, converting glutamine to glutamate, which is then further processed to α-ketoglutarate (αKG). αKG is important for the production of biosynthetic macromolecules that are essential for cell growth. Chemical inhibition of GLS decreases cell growth in culture with varying levels of sensitivity across multiple GBM BTIC lines. Interestingly, activation of the STAT3 pathway using OSM de-sensitizes GBM BTIC lines to GLS inhibition. Furthermore, chemical inhibition of JAK2 sensitizes a subset of GBM BTIC lines to GLS inhibition resulting in a further decrease in cell growth. Overall, we show that STAT3 is a central hub in GBM BTIC lines that modulates proliferation, invasion, and sensitivity to GLS inhibition. Currently, we are continuing these studies in vivo using GBM BTIC orthotopic xenografts in mice. Citation Format: Ian Restall, H. Artee Luchman, Samuel Weiss. STAT3 is a central regulator of proliferation, invasion and metabolism in GBM tumor initiating cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2521.

Abstract P5-07-01: Granulin, a novel STAT3-interacting protein, promotes breast cancer tumorigenicity

Abstract Since the neoplastic phenotype of a cell is largely driven by its gene expression patterns, increasing attention is focused on transcription factors that regulate critical mediators of tumor formation and metastatic progression like the oncogenic transcription factor, signal transducer and activator of transcription 3 (STAT3). Whereas normal cells have transient activation of STAT3 due to tight control by negative regulators, cancer cells frequently have inappropriate constitutive activation of STAT3 which drives increased expression of genes involved in tumorigenesis. However, little is known about proteins that interact with STAT3 to modulate its function. To identify novel STAT3-interacting proteins, we performed liquid chromatography tandem mass spectrometry-based profiling of STAT3-containing complexes immunoprecipitated from the triple-negative breast cancer cell lines MDA-MB-468 and SUM159PT, which have constitutively active STAT3. We identified granulin (GRN) as a novel STAT3-interacting protein and validated the STAT3-GRN interaction in breast cancer cells by co-immunoprecipitation. To investigate the functional effect of GRN on STAT3 activity, we silenced GRN using small interfering RNA. We found that GRN was necessary for constitutive and maximal cytokine-induced STAT3 transcriptional activity in breast cancer cells. GRN modulated cytokine-induced STAT3 function by enhancing STAT3 DNA binding and increasing the time-integrated amount of STAT3 activation and nuclear translocation. Silencing GRN mirrored the effect of silencing STAT3 on reducing the viability, clonogenesis, and migratory capacity of triple-negative breast cancer cells. Furthermore, GRN mRNA levels were significantly and positively correlated with STAT3 gene expression signatures indicative of STAT3 activation as well as with reduced overall survival in breast cancer patients. These studies used a proteomics approach to identify GRN as a novel STAT3 interacting protein that may serve as an important prognostic biomarker and potential therapeutic target in breast cancer. Citation Format: Jennifer E Yeh, Simion Kreimer, Sarah R Walker, Andrea Richardson, Alexander R Ivanov, David A Frank. Granulin, a novel STAT3-interacting protein, promotes breast cancer tumorigenicity [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-07-01.

Granulin, a novel STAT3-interacting protein, enhances STAT3 transcriptional function and correlates with poorer prognosis in breast cancer.

Since the neoplastic phenotype of a cell is largely driven by aberrant gene expression patterns, increasing attention has been focused on transcription factors that regulate critical mediators of tumorigenesis such as signal transducer and activator of transcription 3 (STAT3). As proteins that interact with STAT3 may be key in addressing how STAT3 contributes to cancer pathogenesis, we took a proteomics approach to identify novel STAT3-interacting proteins. We performed mass spectrometry-based profiling of STAT3-containing complexes from breast cancer cells that have constitutively active STAT3 and are dependent on STAT3 function for survival. We identified granulin (GRN) as a novel STAT3-interacting protein that was necessary for both constitutive and maximal leukemia inhibitory factor (LIF)induced STAT3 transcriptional activity. GRN enhanced STAT3 DNA binding and also increased the time-integrated amount of LIF-induced STAT3 activation in breast cancer cells. Furthermore, silencing GRN neutralized STAT3-mediated tumorigenic phenotypes including viability, clonogenesis, and migratory capacity. In primary breast cancer samples, GRN mRNA levels were positively correlated with STAT3 gene expression signatures and with reduced patient survival. These studies identify GRN as a functionally important STAT3-interacting protein that may serve as an important prognostic biomarker and potential therapeutic target in breast cancer.

JAK2, STAT3 and SOCS3 gene expression in women with and without breast cancer.

Breast cancer is a disease that arises from the accumulation of alterations in the genome of cells that make up the mammary gland. The Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway has been reported to participate in the development of breast cancer and is activated by adipocytokines such as leptin, which are elevated in obesity. In contrast, alterations in suppressor of cytokine signaling 3 (SOCS3) gene expression have been found in patients with decreased breast cancer metastasis. The current study sought to identify whether JAK2, STAT3 and SOCS3 gene expression is associated with body mass index (BMI) and breast cancer. This was a cross-sectional prospective study. JAK2, STAT3 and SOCS3 gene expression levels were determined using RT-qPCR from the biopsies of 26 patients with breast cancer and 43 patients with benign breast lesions. We compared the expression of these genes, relative to the housekeeping genes, ACTB and GAPDH, against BMI, clinical stage and immunohistochemistry. STAT3 gene expression was increased in breast cancer patients (p≤0.001; AUC=0.65; AUC 95% CI: 0.5-0.8), and SOCS3 expression was decreased in obese patients with benign breast lesions (p≤0.001; AUC=0.51; AUC 95% CI: 0.36-0.65). With regard to the clinical stage, there were significant differences in STAT3 gene expression between stage II and III (p≤0.011) and stage II and IV (p≤0.033) breast cancers. Among all women, there was a positive correlation between JAK2 and STAT3 expression (R=0.493, p=0.000). In addition, breast cancers that were negative for HER2 were associated with JAK2 and SOCS3 (R=0.645, p=0.003). High levels of STAT3 expression were associated with early stages of breast cancer development and patients in the control group with obesity showed higher expression of SOCS3 regarding overweight.

STAT3 inhibition sensitizes colorectal cancer to chemoradiotherapy in vitro and in vivo

Increased activity of signal transducer and activator of transcription 3 (STAT3) is common in human malignancies, including colorectal cancers (CRCs). We have recently reported that STAT3 gene expression correlates with resistance of CRC cell lines to 5-fluorouracil (5-FU)-based chemoradiotherapy (CT/RT). This is of considerable clinical importance, because a large proportion of rectal cancers are resistant to preoperative multimodal treatment. To test whether STAT3 contributes to CT/RT-resistance, we first confirmed that STAT3 protein expression correlated positively with increasing resistance. While STAT3 was not constitutively active, stimulation with interleukin-6 (IL-6) resulted in remarkably higher expression levels of phosphorylated STAT3 in CT/RT-resistant cell lines. A similar result was observed when we determined IL-6-induced expression levels of phosphorylated STAT3 following irradiation. Next, STAT3 was inhibited in SW480 and SW837 using siRNA, shRNA and the small-molecule inhibitor STATTIC. Successful silencing and inhibition of phosphorylation was confirmed using Western blot analysis and a luciferase reporter assay. RNAi-mediated silencing as well as STATTIC treatment resulted in significantly decreased clonogenic survival following exposure to 3 µM of 5-FU and irradiation in a dose-dependent manner, with dose-modifying factors of 1.3-2.5 at a surviving fraction of 0.37. Finally, STAT3 inhibition led to a profound CT/RT-sensitization in a subcutaneous xenograft model, with a significantly delayed tumor regrowth in STATTIC-treated mice compared with control animals. These results highlight a potential role of STAT3 in mediating treatment resistance and provide first proof of concept that STAT3 represents a promising novel molecular target for sensitizing resistant rectal cancers to CT/RT.