Lentivirus-mediated shRNA interference targeting STAT3 inhibits human pancreatic cancer cell invasion

Effect of RNA interference with HIF-1α on the growth of pulmonary artery endothelial cells in broiler chickens

Pulmonary artery remodeling is a characteristic feature of broiler ascites syndrome (BAS). Pulmonary artery endothelial cells (PAECs) regulated by HIF-1α play a critical role in pulmonary artery remodeling, but the underlying mechanisms of HIF-1α in BAS remain unclear. In this experiment, primary PAECs were cultured in vitro and were identified by coagulation factor VIII. After hypoxia and RNA interference, the mRNA and protein expression levels of HIF-1α and VEGF were determined by qPCR and Western blotting. The transcriptome profiles of PAECs were obtained by RNA sequencing. Our results showed that the positive rate of PAECs was more than 90%, hypoxia-induced promoted the proliferation and apoptosis of PAECs, and RNA interference significantly downregulated the expression of HIF-1α, inhibited the proliferation of PAECs, and promoted the apoptosis of PAECs. In addition, transcriptome sequencing analysis indicated that HIF-1α may regulate broiler ascites syndrome by mediating COL4A, vitronectin, vWF, ITGα8, and MKP-5 in the ECM, CAMs and MAPK pathways in PAECs. These studies lay the foundation for further exploration of the mechanisms of pulmonary artery remodeling, and HIF-1α may be a potentially effective gene for the prevention and treatment of BAS.

Janus Kinase Inhibition Ameliorates Ischemic Stroke Injury and Neuroinflammation Through Reducing NLRP3 Inflammasome Activation via JAK2/STAT3 Pathway Inhibition

Background

Inflammatory responses play a multiphase role in the pathogenesis of cerebral ischemic stroke (IS). Ruxolitinib (Rux), a selective oral JAK 1/2 inhibitor, reduces inflammatory responses via the JAK2/STAT3 pathway. Based on its anti-inflammatory and immunosuppressive effects, we hypothesized that it may have a protective effect against stroke. The aim of this study was to investigate whether inhibition of JAK2 has a neuroprotective effect on ischemic stroke and to explore the potential molecular mechanisms.

Methods

Rux, MCC950 or vehicle was applied to middle cerebral artery occlusion (MCAO) mice in vivo and an oxygen-glucose deprivation/reoxygenation (OGD/R) model in vitro. After 3 days of reperfusion, neurological deficit scores, infarct volume and brain water content were assessed. Immunofluorescence staining and western blots were used to measure the expression of NLRP3 inflammasome components. The infiltrating cells were investigated by flow cytometry. Proinflammatory cytokines were assessed by RT-qPCR. The expression of the JAK2/STAT3 pathway was measured by western blots. Local STAT3 deficiency in brain tissue was established with a lentiviral vector carrying STAT3 shRNA, and chromatin immunoprecipitation (ChIP) assays were used to investigate the interplay between NLRP3 and STAT3 signaling.

Results

Rux treatment improved neurological scores, decreased the infarct size and ameliorated cerebral edema 3 days after stroke. In addition, immunofluorescence staining and western blots showed that Rux application inhibited the expression of proteins related to the NLRP3 inflammasome and phosphorylated STAT3 (P-STAT3) in neurons and microglia/macrophages. Furthermore, Rux administration inhibited the expression of proinflammatory cytokines, including TNF-α, IFN-γ, HMGB1, IL-1β, IL-2, and IL-6, suggesting that Rux may alleviate IS injury by inhibiting proinflammatory reactions via JAK2/STAT3 signaling pathway regulation. Infiltrating macrophages, B, T, cells were also reduced by Rux. Local STAT3 deficiency in brain tissue decreased histone H3 and H4 acetylation on the NLRP3 promoter and NLRP3 inflammasome component expression, indicating that the NLRP3 inflammasome may be directly regulated by STAT3 signaling. Rux application suppressed lipopolysaccharide (LPS)-induced NLRP3 inflammasome secretion and JAK2/STAT3 pathway activation in the OGD/R model in vitro.

Conclusion

JAK2 inhibition by Rux in MCAO mice decreased STAT3 phosphorylation, thus inhibiting the expression of downstream proinflammatory cytokines and the acetylation of histones H3 and H4 on the NLRP3 promoter, resulting in the downregulation of NLRP3 inflammasome expression.

Signal Transducer and Activator of Transcription (STATs) Proteins in Cancer and Inflammation: Functions and Therapeutic Implication

Signal Transducer and Activator of Transcription (STAT) pathway is connected upstream with Janus kinases (JAK) family protein and capable of integrating inputs from different signaling pathways. Each family member plays unique functions in signal transduction and crucial in mediating cellular responses to different kind of cytokines. STAT family members notably STAT3 and STAT5 have been involved in cancer progression whereas STAT1 plays opposite role by suppressing tumor growth. Persistent STAT3/5 activation is known to promote chronic inflammation, which increases susceptibility of healthy cells to carcinogenesis. Here, we review the role of STATs in cancers and inflammation while discussing current therapeutic implications in different cancers and test models, especially the delivery of STAT3/5 targeting siRNA using nanoparticulate delivery system.

OSU-A9 inhibits pancreatic cancer cell lines by modulating p38-JAK-STAT3 signaling

Pancreatic cancer is an aggressive malignancy that is the fourth leading cause of death worldwide. Since there is a dire need for novel and effective therapies to improve the poor survival rates of advanced pancreatic cancer patients, we analyzed the antitumor effects of OSU-A9, an indole-3-carbinol derivative, on pancreatic cancer cell lines in vitro and in vivo. OSU-A9 exhibited a stronger antitumor effect than gemcitabine on two pancreatic cancer cell lines, including gemcitabine-resistant PANC-1 cells. OSU-A9 treatment induced apoptosis, the down-regulation of Akt phosphorylation, up-regulation of p38 phosphorylation and decreased phosphorylation of JAK and STAT3. Cell migration and invasiveness assays showed that OSU-A9 reduced cancer cell aggressiveness and inhibited BxPC-3 xenograft growth in nude mice. These results suggest that OSU-A9 modulates the p38-JAK-STAT3 signaling module, thereby inducing cytotoxicity in pancreatic cancer cells. Continued evaluation of OSU-A9 as a potential therapeutic agent for pancreatic cancer thus appears warrented.

Downregulation of signal transduction and STAT3 expression exacerbates oxidative stress mediated by NLRP3 inflammasome

Activated nucleotide binding to the oligonucleotide receptor protein 3 (NLRP3) inflammasome is possibly involved in the pathogenesis of Alzheimer's disease through oxidative stress and neurogenic inflammation. Low expression of the signal transducer and activator of transcription 3 (STAT3) gene may promote the occurrence of neurodegenerative diseases to some extent. To clarify the roles of the NLRP3 inflammasome and STAT3 expression in oxidative stress, (1) SHSY5Y cells were incubated with 1 mM H₂O₂ to induce oxidative stress injury, and the expression of human-cell-specific signal transduction, STAT3-shRNA silencing signal transduction and STAT3 were detected. Cells were pretreated with Ca²⁺ chelator BAPATA-AM (0.1 mM) for 30 minutes as a control. (2) Western blot assay was used to analyze the expression of caspase-1, NLRP3, signal transduction and STAT3. Enzyme-linked immunosorbent assay was used to analyze interleukin-1β levels. Flow cytometry was carried out to calculate the number of apoptotic cells. We found that H₂O₂ treatment activated NLRP3 inflammasomes and decreased phosphorylation of signal transduction and STAT3 serine 727. BAPTA-AM pretreatment abolished the H₂O₂-induced activation of NLRP3 inflammasomes, caspase-1 expression, interleukin-1β expression and apoptosis in SHSY5Y cells, and had no effect in cells with downregulated STAT3 expression by RNAi. The findings suggest that downregulation of signal transduction and STAT3 expression may enhance the oxidative stress mediated by NLRP3, which may not depend on the Ca²⁺ signaling pathway.

Clinicopathological significance of SMAD4 loss in pancreatic ductal adenocarcinomas: a systematic review and meta-analysis

Pancreatic ductal adenocarcinoma (PDAC) is one of the leading causes of cancer mortality. Although advances have been made in understanding the pathogenesis of PDAC, the outcome still remains poor. The aim of this study is to conduct a meta-analysis to evaluate the precise association between SMAD4 loss and clinicopathological significance in PDAC. A literature search was made in PubMed, Web of Science, Google scholar, and EMBASE for related publications. The data were extracted and assessed by two reviewers independently. Analysis of pooled data was performed, Odds Ratio or Hazard Ratio with corresponding confidence intervals was calculated and summarized. 12 relevant articles were included for full review in detail and meta-analysis. The frequency of SMAD4 protein loss was significantly increased in PDAC than in nonmalignant pancreatic tissue, Odd Ratio was 0.05 with 95% confidence interval 0.01-0.23, p<0.0001. SMAD4 loss was significantly associated with poor overall survival in patients with PDAC, Hazard Ratio was 0.61 with 95% confidence interval 0.38-0.99, p=0.05. SMAD4 loss was not correlated with the size, grades, and lymph node metastasis of PDAC. In conclusion, SMAD4 is a biomarker for the diagnosis of PDAC. SMAD4 loss is significantly related to poor prognosis in patients with PDAC.

Regulation of EMT by STAT3 in gastrointestinal cancer (Review)

Gastrointestinal (GI) cancer is characterized by its aggressiveness and tendency to metastasize at early stage. Epithelial-mesenchymal transition (EMT), commonly known as the preparing step of metastasis, may account for the aggressive phenotype of GI cancer cells. The process of EMT is finely orchestrated by multiple layers of regulators. Signal transducer and activator of transcription 3 (STAT3) is a transcription factor constitutively activated in diverse malignancies. Recent studies have suggested an involvement of STAT3 in GI cancer EMT. In this review, we first take an insight into the oncogenic functions of STAT3 in GI cancer, and then summarize the possible mechanisms by which STAT3 regulates the EMT process. Through the extensive interactions with EMT-inducing transcription factors and non-coding RNAs, and crosstalk with other signaling pathways, STAT3 has been demonstrated to promote the mesenchymal and invasive phenotype of GI cancer, which provides rationales for specifically targeting STAT3 to prevent and reverse the progression of GI cancer.

STAT3 regulates hypoxia-induced epithelial mesenchymal transition in oesophageal squamous cell cancer

Hypoxia plays a key role in tumour initiation and metastasis; one of the mechanisms is to induce epithelial-mesenchymal transition (EMT). Signal transducer and activator of transcription 3 (STAT3) is involved in EMT by regulating the transcriptional regulators of E-cadherin, the biomarker of EMT. Until now, however, few studies have focused on the effects of STAT3 in hypoxia-induced EMT in tumour cells. The goal of this study was to investigate the roles of STAT3 in hypoxia-induced EMT in oesophageal squamous cell carcinoma (ESCC). The ESCC cells, TE-1 and EC-1, were incubated in normoxia, or in CoCl₂, which was used to mimic hypoxia. With CoCl₂, the ESCC cells showed increased migration and invasion abilities, accompanied with upregulation of HIF-1α, STAT3, and vimentin, and downregulation of E-cadherin. Knockdown of STAT3 inhibited EMT of ESCC cells and downregulated HIF-1α in vitro and in vivo. In ChIP assays, STAT3 bound to the promoter of HIF-1α, suggesting that STAT3 regulates transcription of HIF-1α. In conclusion, hypoxia induces EMT of ESCC, and STAT3 regulates this process by promoting HIF-1α expression.

SMAD4 and its role in pancreatic cancer

Transforming growth factor-β (TGF-β) regulates cell functions and has key roles in pancreatic cancer development. SMAD4, as one of the Smads family of signal transducer from TGF-β, mediates pancreatic cell proliferation and apoptosis and is specifically inactivated in half of advanced pancreatic cancers. In recent years, many advances concerning SMAD4 had tried to unravel the complex signaling mechanisms of TGF-β and its dual role of tumor-suppressive and tumor-promoting efforts in pancreatic cancer initiation and progression through SMAD4-dependent TGF-β signaling and SMAD4-independent TGF-β signaling pathways. Meanwhile, its potential prognostic value based on immunohistochemical expression in surgical sample was variably reported by several studies and short of a systematic analysis. This review aimed to discuss the structure, functions, and regulation of this principal protein and its effects in determining the progression and prognosis of pancreatic cancer.

The tumor suppressor miR-124 inhibits cell proliferation by targeting STAT3 and functions as a prognostic marker for postoperative NSCLC patients

The aim of the present study was to investigate the role of miR-124 in lung cancer and identify the potential predictive value of miR-124 in postoperative non-small cell lung cancer (NSCLC) patients. We detected miR-124 expression in A549, NCL-H460 and normal lung epithelial BEAS-2E cells and showed a significantly lower expression level of miR-124 in NSCLC cells than in BEAS-2E cells. Upregulation of miR-124 expression levels in both A549 and NCL-H460 cells by transfection with miR-124 mimics suppressed cell proliferation and induced apoptosis. Further investigation revealed that miR-124 bound directly to the 3' UTR region of STAT3, thereby inhibiting STAT3 expression. In addition, miR-124 levels detected in NSCLC tissues were lower than those in adjacent normal lung tissues, while the opposite was observed for STAT3. In NSCLC, the expression levels of miR-124 and STAT3 correlated significantly with the tumor node metastases (TNM) stage, differentiation grade and lymph node metastasis, while the levels of these molecules did not differ significantly by gender, age, location, smoking index, pleural invasion or pathological type. The expression level of miR-124 was significantly associated with disease-free survival (DFS) in both positive and negative lymph node groups. Furthermore, patients with low miR-124 or high STAT3 expression generally received a worse prognosis in terms of both overall survival (OS) and DFS. In conclusion, our findings suggest that miR-124 functions as a tumor suppressor by targeting STAT3, and that miR-124 may potentially serve as a useful biomarker for the prognosis of NSCLC patients.

Nucleic acid-based approaches to STAT inhibition

Silencing of abnormally activated genes can be accomplished in a highly specific manner using nucleic acid based approaches. The focus of this review includes the different nucleic acid based inhibition strategies such as antisense oligodeoxynucleotides, small interfering RNA (siRNA), dominant-negative constructs, G-quartet oligonucleotides and decoy oligonucleotides, their mechanism of action and the effectiveness of these approaches to targeting the STAT (signal transducer and activator of transcription) proteins in cancer. Among the STAT proteins, especially STAT3, followed by STAT5, are the most frequently activated oncogenic STATs, which have emerged as plausible therapeutic cancer targets. Both STAT3 and STAT5 have been shown to regulate numerous oncogenic signaling pathways including proliferation, survival, angiogenesis and migration/invasion.

A meta-analysis of STAT3 and phospho-STAT3 expression and survival of patients with non-small-cell lung cancer

BACKGROUND

The prognostic role of signal transducer and activator of transcription 3 (STAT3) and phospho-STAT3 in non-small-cell lung cancer (NSCLC) remains controversial. To clarify its impact on survival, we performed a meta-analysis to quantitatively assess STAT3 and phospho-STAT3 expression on the prognosis of NSCLC.

METHODS

Published studies were identified using a systematic and thorough literature search. To be eligible, a study had to investigate STAT3 or phospho-STAT3 expression rates of NSCLC patients in different characteristics and provide patient survival data.

RESULTS

A total of 17 retrospective trials were chosen for meta-analysis, including 1793 patients. The estimated pooled log HR (0.67, 95% CI: 0.57-0.77) of 9 trials (STAT3: log HR 0.71, 95% CI 0.38-1.04; phospho-STAT3: log HR 0.67, 95% CI 0.56-0.77) for NSCLC was statistically significant (P < 0.0001), suggesting that high STAT3 or phospho-STAT3 expression is a strong predictor of poor prognosis among patients with NSCLC. For the risk factors, pooled analysis of patients with STAT3 positivity, demonstrated a statistically significant OR (3.82, 95% CI: 2.37-6.16) between poorly differentiated carcinoma and well-moderately, OR (5.68, 95% CI: 3.16-10.21) between stage III-IV patients and stage I-II patients, and OR (3.41, 95% CI: 2.12-5.49) between patients with lymph node metastasis and patients without lymph node metastasis. However, pooled analysis of patients with phospho-STAT3 positivity only demonstrated a statistically significant OR (4.51, 95% CI: 1.57-12.96) between poorly differentiated carcinoma and well-moderately (P < 0.05).

CONCLUSIONS

High STAT3 or phospho-STAT3 expression is a strong predictor of poor prognosis among patients with NSCLC. The conclusion should be confirmed by large prospective studies with long-term follow-up.

MiR-130b is a prognostic marker and inhibits cell proliferation and invasion in pancreatic cancer through targeting STAT3

Accumulating evidence indicates that microRNAs (miRNAs) are aberrantly expressed in human cancer and contribute to the tumorigenesis, but their roles in pancreatic cancer are still largely unknown. In this study, our data showed that miR-130b was significantly downregulated in 52 pairs of pancreatic cancer tissues and five cell lines. Furthermore, the deregulated miR-130b was correlated with worse prognosis, increased tumor size, late TNM stage, lymphatic invasion and distant metastasis. Multivariate analysis showed that miR-130b expression was a significant and independent prognostic predictor for pancreatic cancer patients. Functional studies indicated that the overexpression of miR-130b dramatically suppressed the proliferation of pancreatic cancer cells both in vitro and in vivo, which could be attributed to the induction of apoptosis and cell cycle arrest at S phase. Meanwhile, an overexpressed miR-130b remarkably inhibited the invasive ability of pancreatic cancer cells. Moreover, the dual luciferase assay revealed that STAT3 was directly targeted by miR-130b, which was further confirmed by the inverse expression of miR-130b and STAT3 in pancreatic cancer samples. Our findings suggested that miR-130b might have a considerable potential in prognosis identification and application of therapy for pancreatic cancer.

Downregulation of Stat3 in melanoma: reprogramming the immune microenvironment as an anticancer therapeutic strategy

Persistent activation of the transcription factor, signal transducer and activator of transcription 3 (Stat3) has been shown to mediate several oncogenic features in many types of cancers, including melanoma. In this study, we investigated whether lentiviral (LV) delivery of Stat3-targeting short hairpin RNA (shRNA; LV-shStat3) to K1735-C4 melanoma cells modulates antitumor immunity. Three shStat3 sequences, starting at the position 446, 830 and 1412, were cloned into a mir30 cassette. A shRNA with scrambled sequence served as a control. Transduction with LV-shStat3 resulted in downregulation of Stat3 in vitro. The latter coincided with low cell viability, a reduced expression of survivin and matrix metalloproteinase (MMP)-2. A single injection of LV-shStat3 in K1735-C4 tumors efficiently downregulated Stat3 in vivo and resulted in reduction of both vascular endothelial growth factor secretion and in myeloid-derived suppressor cell (MDSC) numbers. In contrast, we observed an increase in interleukin-6 and interferon-γ secretion, mature dendritic cells (DCs) and CD8(+) T cells. Both DCs and CD8(+) T cells displayed enhanced activity, whereas granulocytic MDSCs lost their suppressive capacity upon Stat3 downregulation. Importantly, a single injection of LV-shStat3 was sufficient to reduce tumor growth, hence prolong survival of tumor-bearing mice. These data demonstrate that Stat3 downregulation in melanoma reinvigorates existing antitumor immunity.

APE1/Ref-1 regulates STAT3 transcriptional activity and APE1/Ref-1-STAT3 dual-targeting effectively inhibits pancreatic cancer cell survival

Pancreatic cancer is a largely incurable disease, and increasing evidence supports strategies targeting multiple molecular mediators of critical functions of pancreatic ductal adenocarcinoma cells. Intracellular redox state modulates the activity of various signal transduction pathways and biological processes, including cell survival, drug resistance and responsiveness to microenvironmental factors. Recently, it has been shown that the transcription factor STAT3 is under redox control, but the mechanisms involved in its regulation are unknown. Here, we demonstrate for the first time that STAT3 DNA binding and transcriptional activity is directly regulated by the redox function of the APE1/Ref-1 endonuclease, using overexpression and redox-specific mutational strategies, and gene knockdown. Also, pharmacological blockade of APE1/Ref-1 by the redox-selective inhibitor E3330 abrogates STAT3 DNA binding. Since APE1/Ref-1 also exerts redox control on other cancer-associated transcription factors, we assessed the impact of dual-targeting of STAT3 signaling and APE1/Ref-1 redox on pancreatic cancer cell functions. We observed that disruption of APE1/Ref-1 redox activity synergizes with STAT3 blockade to potently inhibit the proliferation and viability of human PDAC cells. Mechanistically, we show that STAT3–APE1/Ref-1 dual targeting promotes marked tumor cell apoptosis, with engagement of caspase-3 signaling, which are significantly increased in comparison to the effects triggered by single target blockade. Also, we show that STAT3–APE1/Ref-1 dual blockade results in significant inhibition of tumor cell migration. Overall, this work demonstrates that the transcriptional activity of STAT3 is directly regulated by the redox function of APE1/Ref-1, and that concurrent blockade of STAT3 and APE1/Ref-1 redox synergize effectively inhibit critical PDAC cell functions.

Crosstalk of Sp1 and Stat3 signaling in pancreatic cancer pathogenesis

Pancreatic cancer progression is attributed to genetic and epigenetic alterations and a chaotic tumor microenvironment. Those diverse "upstream signal" factors appear to converge on specific sets of central nuclear regulators, namely, transcription factors. Specificity Protein 1 (Sp1) and signal transducer and activator of transcription 3 (Stat3) are central transcription factors that regulate a number of pathways important to tumorigenesis, including tumor cell-cycle progression, apoptosis, angiogenesis, metastasis, and evasion of the immune system. Recently, researchers demonstrated many types of crosstalk of Sp1 and Stat3 in tumor signal transduction and that these factors function cooperatively to activate targeted genes and promote tumorigenesis in pancreatic cancer. Therefore, targeting both Sp1 and Stat3 is a potential preventive and therapeutic strategy for pancreatic cancer.

Prognostic significance of STAT3 expression and its correlation with chemoresistance of non-small cell lung cancer cells

Activation of signal transducer and activator of transcription 3 (STAT3) plays important roles in tumorigenesis and tumor development. Previously, we have reported that overexpression of STAT3 potentiates growth, survival and radioresistance of non-small cell lung cancer (NSCLC) cells. The aim of this study was to investigate the prognostic significance of STAT3 expression and its correlation with chemoresistance of NSCLC cells. Semi-quantitative RT-PCR was performed to detect the expression of STAT3 mRNA in 12 NSCLC and corresponding adjacent lung tissues. Immunohistochemistry was performed to detect the expression of STAT3 protein in 76 NSCLC tissue samples. Additionally, the correlation between STAT3 expression and prognosis of NSCLC patients was statistically analyzed. The role of STAT3 in chemoresistance of NSCLC cells was also assessed by the vector-based small interfering RNA. The expression level of STAT3 mRNA in NSCLC tissues was significantly higher than that in corresponding adjacent lung tissues (P<0.05). Positive immunostaining of STAT3 protein was mainly located in the cytoplasm of tumor cells. The expression of STAT3 protein was significantly correlated with tumor differentiation, clinical stage and lymph node metastasis of NSCLC patients. Moreover, the 5-year overall survival rate of patients with high STAT3 expression (42.3%) was significantly lower than that of patients with low STAT3 expression (58.8%; P<0.001). Multivariate analysis using the Cox proportional hazard model showed that high STAT3 protein expression was an independent prognostic factor for NSCLC patients (P=0.021). Furthermore, two stably transfected cell lines (A549/shSTAT3 and SPC-A1/shSTAT3) were successfully established, and RNAi-mediated STAT3 inhibition could significantly increase the sensitivity of NSCLC cells to cisplatin by enhancing caspase-3-dependent apoptosis. Together, the expression of STAT3 might be an independent prognostic marker for NSCLC patients and RNAi-mediated STAT3 inhibition would be a potential strategy for chemosensitization of NSCLC cells.

STAT3 knockdown reduces pancreatic cancer cell invasiveness and matrix metalloproteinase-7 expression in nude mice

Aims

Transducer and activator of transcription-3 (STAT3) plays an important role in tumor cell invasion and metastasis. The aim of the present study was to investigate the effects of STAT3 knockdown in nude mouse xenografts of pancreatic cancer cells and underlying gene expression.

Methods

A STAT3 shRNA lentiviral vector was constructed and infected into SW1990 cells. qRT-PCR and western immunoblot were performed to detect gene expression. Nude mouse xenograft assays were used to assess changes in phenotypes of these stable cells in vivo. HE staining was utilized to evaluate tumor cell invasion and immunohistochemistry was performed to analyze gene expression.

Results

STAT3 shRNA successfully silenced expression of STAT3 mRNA and protein in SW1990 cells compared to control cells. Growth rate of the STAT3-silenced tumor cells in nude mice was significantly reduced compared to in the control vector tumors and parental cells-generated tumors. Tumor invasion into the vessel and muscle were also suppressed in the STAT3-silenced tumors compared to controls. Collagen IV expression was complete and continuous surrounding the tumors of STAT3-silenced SW1990 cells, whereas collagen IV expression was incomplete and discontinuous surrounding the control tumors. Moreover, microvessel density was significantly lower in STAT3-silenced tumors than parental or control tumors of SW1990 cells. In addition, MMP-7 expression was reduced in STAT3-silenced tumors compared to parental SW1990 xenografts and controls. In contrast, expression of IL-1β and IgT7α was not altered.

Conclusion

These data clearly demonstrate that STAT3 plays an important role in regulation of tumor growth, invasion, and angiogenesis, which could be act by reducing MMP-7 expression in pancreatic cancer cells.

RNAi-mediated knockdown of cyclooxygenase2 inhibits the growth, invasion and migration of SaOS2 human osteosarcoma cells: a case control study

Background

Cyclooxygenase2 (COX-2), one isoform of cyclooxygenase proinflammatory enzymes, is responsible for tumor development, invasion and metastasis. Due to its role and frequent overexpression in a variety of human malignancies, including osteosarcoma, COX-2 has received considerable attention. However, the function of COX-2 in the pathogenesis of cancer is not well understood. We examined the role of COX-2 in osteosarcoma.

Methods

We employed lentivirus mediated-RNA interference technology to knockdown endogenous gene COX-2 expression in human osteosarcoma cells (SaOS2) and analyzed the phenotypical changes. The effect of COX-2 treatment on the proliferation, cell cycle, invasion and migration of the SaOS2 cells were assessed using the MTT, flow cytometry, invasion and migration assays, respectively. COX-2, vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), basic fibroblast growth factor (bFGF) mRNA and protein expression were detected by RT-PCR and western blotting.

Results

Our results indicate that a decrease of COX-2 expression in human osteosarcoma cells significantly inhibited the growth, decreased the invasion and migration ability of SaOS2 cells. In addition, it also reduced VEGF, EGF and bFGF mRNA and protein expression.

Conclusions

The COX-2 signaling pathway may provide a novel therapeutic target for the treatment of human osteosarcoma.