6774

STAT3

signal transducer and activator of transcription 3 (acute-phase response factor);STAT3;signal transducer and activator of transcription 3 (acute-phase response factor)

DNA-binding protein APRF|acute-phase response factor|signal transducer and activator of transcription 3

17q21.31

protein-coding

Human urinary bladder cancer is the fifth most common cancer, with a worldwide estimate of about two million patients. Recurrence after complete transurethral prostatic resection is the most important problem in therapy. Combination therapy is a new approach in the treatment of cancers that do not respond to current therapies. These therapies have many advantages over conventional therapies, such as fewer side-effects and greater efficiency. Research efforts using natural compounds for the elimination or growth suppression of the cancer arise from studies on methylsulfonylmethane (MSM). MSM is a natural sulfur compound with no side-effects. AG490 is a tyrosine kinase inhibitor that has been extensively used for inhibiting Jak2 in vitro and in vivo. In our study, the combinatorial effect of these two agents on human bladder cancer cell lines and xenografts was analyzed. We observed that the combination of AG490 and MSM inhibited cancer cell viability and cell migration in vitro. This combination inhibited VEGF mRNA expression in bladder cancer cell lines. In vivo experiments showed that oral administration of AG490 and MSM combination significantly inhibited the growth of tumor xenografts in mice. Our study clearly demonstrates that the predominant effect of this combination is the reduction of signaling molecules including STAT3, STAT5b, IGF-1R, VEGF and VEGF-R2 which are involved in the growth, progression and metastasis of human bladder cancer. The anti-metastatic ability of this drug combination is confirmed using metastatic animal models. Therefore, this combination could have the effect of genesistasis and powerful anticancer effects against bladder cancer.

OBJECTIVE: To investigate the effect of Janus kinase (JAK) inhibitor AG490 on invasion and metastasis of the human breast cancer cell MDA-MB-231, and to explore the regulating role of JAK-STAT3 signaling pathway when the breast cancer occurs to the invasiveness and metastasis. METHODS: The human breast cancer cell MDA-MB-231 was used as the research object, and AG490 was as Janus kinase inhibitor. The adhesion of MDA-MB-231 cell attaching to matrigel was measured with MTT assay. The invasion and metastasis potential were evaluated with transwell chamber. The P-STAT3 protein in cell was detected by Western-blot. RESULTS: Janus kinase inhibitor AG490 could make that the expression of P-STAT3 in human breast cancer cell MDA-MB-231 became weak, and that the abilities of adhesion, invasion and metastasis were also dropping down as compared with the control group (P < 0.01). CONCLUSION: JAK-STAT3 signaling pathway participates in regulating the invasion and metastasis of human breast cancer. Inhibiting the activation of JAK-STAT3 signaling pathway can suppress the invasion and metastasis of human breast cancer.

We previously established that overexpression of the EGF receptor (EGFR) is sufficient to induce tumor formation by otherwise nontransformed mammary epithelial cells, and that the initiation of epithelial-mesenchymal transition (EMT) is capable of increasing the invasion and metastasis of these cells. Using this breast cancer (BC) model, we find that in addition to EGF, adhesion to fibronectin (FN) activates signal transducer and activator of transcription 3 (STAT3) through EGFR-dependent and -independent mechanisms. Importantly, EMT facilitated a signaling switch from SRC-dependent EGFR:STAT3 signaling in pre-EMT cells to EGFR-independent FN:JAK2:STAT3 signaling in their post-EMT counterparts, thereby sensitizing these cells to JAK2 inhibition. Accordingly, human metastatic BC cells that failed to activate STAT3 downstream of EGFR did display robust STAT3 activity upon adhesion to FN. Furthermore, FN enhanced outgrowth in three-dimensional organotypic cultures via a mechanism that is dependent upon beta1 integrin, Janus kinase 2 (JAK2), and STAT3 but not EGFR. Collectively, our data demonstrate that matrix-initiated signaling is sufficient to drive STAT3 activation, a reaction that is facilitated by EMT during BC metastatic progression.

Although gankyrin is involved in the tumorigenicity and metastasis of some malignancies, the role of gankyrin in cholangiocarcinoma (CCA) is unclear. In this study we investigated the expression of gankyrin in human CCA tissues and cell lines. The effects of gankyrin on CCA tumor growth and metastasis were determined both in vivo and in vitro. The results showed that gankyrin was overexpressed in CCA tissues and cell lines. Gankyrin expression was associated with CCA histological differentiation, TNM stage, and metastasis. The multivariate Cox analysis revealed that gankyrin was an independent prognostic indicator for overall survival. Gankyrin overexpression promoted CCA cell proliferation, migration, and invasion, while gankyrin knockdown inhibited CCA tumor growth, metastasis, and induced Rb-dependent senescence and G1 phase cell cycle arrest. Gankyrin increased the phosphorylation of signal transducer and activator of transcription 3 (STAT3) and promoted the nuclear translocation of p-STAT3. Suppression of STAT3 signaling by small interfering RNA (siRNA) or STAT3 inhibitor interfered with gankyrin-mediated carcinogenesis and metastasis, while interleukin (IL)-6, a known upstream activator of STAT3, could restore the proliferation and migration of gankyrin-silenced CCA cells. The IL-6 level was decreased by gankyrin knockdown, while increased by gankyrin overexpression. Gankyrin regulated IL-6 expression by way of facilitating the phosphorylation of Rb; meanwhile, rIL-6 treatment increased the expression of gankyrin, suggesting that IL-6 was regulated by a positive feedback loop involving gankyrin in CCA. In the xenograft experiments, gankyrin overexpression accelerated tumor formation and increased tumor weight, whereas gankyrin knockdown showed the opposite effects. The in vivo spontaneous metastasis assay revealed that gankyrin promoted CCA metastasis through IL-6/STAT3 signaling pathway. CONCLUSION: Gankyrin is crucial for CCA carcinogenesis and metastasis by activating IL-6/STAT3 signaling pathway through down-regulating Rb protein.

The plant sterol guggulsterone has been shown to exert anti-tumor effects, making it a candidate chemotherapeutic agent. We investigated the anti-tumor effects of guggulsterone on colon cancer cells and elucidated the underlying molecular mechanisms related to angiogenesis. The apoptotic effects of guggulsterone were examined by cell survival assay. Western blot analysis was used to determine the levels of various down-stream intracellular proteins involved in angiogenesis, including signal transducer and activator of transcription 3 (STAT3), vascular endothelial growth factor (VEGF), hypoxia-inducible factor-1alpha (HIF-1alpha) and aryl hydrocarbon receptor nuclear translocator (ARNT). Using chromatin immunoprecipitation assay, we tested whether guggulsterone affects the recruitment of STAT3, ARNT and HIF-1alpha to the human VEGF promoter. To investigate the effect of guggulsterone on vascular endothelial cell migration and invasion, tube formation and migration assays were conducted using human umbilical vein endothelial cells (HUVECs). Matrix metalloproteinase (MMP)-2 and -9 activities were measured by gelatin zymography. Guggulsterone significantly reduced cell viability in colon cancer cells in a dose-dependent manner and blocked VEGF, ARNT and STAT3 expression prominently in hypoxic conditions. The recruitment of STAT3 and ARNT, but not HIF-1alpha, to the VEGF promoter was inhibited by guggulsterone treatment. HUVECs produced much foreshortened and severely broken tubes and showed decreased migration activity under guggulsterone effects. In addition, zymography revealed that MMP-2 and -9 enzyme activities were markedly lower in the presence of guggulsterone. The results of this study suggest that guggulsterone not only induces apoptosis, but also inhibits angiogenesis and metastasis in colon cancer cells by blocking STAT3 and VEGF expression, suggesting its therapeutic potential in the treatment of colorectal cancer.

Half of patients with KRAS wild-type colorectal cancer do not benefit from adding anti-epithelial growth factor receptor (EGFR) to standard chemotherapy regimens. This retrospective study was performed in 94 patients with metastatic colorectal cancer (mCRC) treated in the second line with cetuximab and chemotherapy. Signal transducer and activator of transcription 3 (STAT3) phosphorylation in tumor cells was correlated with decreased median progression-free survival and overall survival (OS). These results highlight the potential role of STAT3 as a molecular target to optimize anti-EGFR therapies. BACKGROUND: Signal transducer and activator of transcription 3 (STAT3) is involved in epithelial growth factor receptor (EGFR) signaling in a KRAS-independent manner. Phosphorylated STAT3 (pSTAT3) expression in patients with metastatic colorectal cancer (mCRC) treated with anti-EGFR-containing salvage chemotherapy has never been investigated. PATIENTS AND METHODS: : The first endpoint of this retrospective study was to evaluate the impact of pSTAT3 on the time to progression (TTP) in 94 patients with mCRC treated with anti-EGFR-based therapies in the second- or third-line setting between July 2004 and November 2009. The influence of pSTAT3 on objective response rate and overall survival (OS) was also reported. Nuclear expression of pSTAT3 status was evaluated by immunohistochemical tests on formalin-fixed and paraffin-embedded tumor samples obtained before therapy. RESULTS: Positive expression of pSTAT3 was observed in 24.5% of the tumor samples. The probability of achieving an objective response was 13% among patients with positive nuclear expression of pSTAT3 compared with 41% for patients displaying pSTAT3-negative tumors (P = .02). In a multivariate logistic regression model, high-grade skin rash, wild-type KRAS status, and negative pSTAT3 status significantly improved TTP and OS. CONCLUSION: These results underscore an impact of pSTAT3 on the clinical efficacy of anti-EGFR-containing chemotherapy regimens and support the prospective assessment of this biomarker.

Pituitary tumor-transforming gene (PTTG), the index mammalian securin, is abundantly expressed in several tumors and regulates tumor growth and progression. Molecular mechanisms elucidating PTTG regulation and actions remain elusive. Here, we provide evidence that PTTG acts as a signal transducer and activator of transcription factor 3 (STAT3) target gene. Total STAT3 and Tyr705 phosphorylated STAT3 were concordantly expressed with PTTG in human colorectal tumors (n=97 and n=95, respectively, P<0.001). STAT3 specifically bound the human PTTG promoter and induced PTTG transcriptional activity (twofold) as assessed by chromatin immunoprecipitation and luciferase reporter assays. STAT3 transfection increased PTTG mRNA and protein abundance twofold in HCT116 human colon cancer cells, and induction was further enhanced (threefold) by constitutively active STAT3 (STAT3-C), whereas strongly abrogated by dominant-negative STAT3 (STAT3-DN). Attenuating PTTG expression by siRNA in STAT3 HCT116 stable transfectants suppressed cell growth and colony formation in vitro, and PTTG cell knockout also constrained activated STAT3-induced explanted murine tumor growth in vivo. STAT3 increased HCT116 cell migration and invasion up to fivefold, whereas cell mobility was abolished by STAT3-DN (>85%). Impairing PTTG expression by siRNA also strongly suppressed STAT3-faciliated cell migration and invasion by up to 90%. Knocking out PTTG in STAT3-C HCT116 stable transfectants strongly decreased tumor metastases in nude mice, indicating the requirement of PTTG for STAT3-promoted metastasis. These results elucidate a mechanism for tumor cell PTTG regulation, whereby STAT3 induces PTTG expression to facilitate tumor growth and metastasis, and further support the rationale for targeting PTTG to abrogate colorectal cancer growth.

AIM: To explore the relationship between Cripto-1 (CR-1) and tyrosine phosphorylation STAT3 (p-STAT3) expressions in gastric cancer (GC) and gastric carcinogensis and metastasis. METHODS: The PV9000 immunohistochemical method was used to detect the expression of CR-1 and p-STAT3 in 178 cases of GC, 95 matched normal gastric mucosa, 40 chronic atrophic gastritis (CAG), 48 intestinal metaplasia (IM) and 25 dysplasia (DYS). RESULTS: The positive rates of CR-1 and p-STAT3 expression were significantly higher in CAG (65.0% and 60.0%), in IM (83.3% and 77.1%), DYS (80.0% and 68%) and GC (71.3% and 60.1%) than in normal gastric mucosa (43.2% and 41.1%, P < 0.05), respectively. The expressions of CR-1 and p-STAT3 (78.3% and 66.7%) were significantly higher in GC with lymph node metastasis than in those without metastasis (53.1% and 42.9%, P < 0.05). CR-1 expression was also related to histological and Lauren's types of GC (P < 0.001). Furthermore, there was positive relationship between CR-1 and p-STAT3 expressions in GC (r(k) = 0.189, P = 0.002). CONCLUSION: The up-regulation of CR-1 and p-STAT3 may play important roles in gastric carcinogenesis and lymph node metastasis. CR-1 and p-STAT3 expression in GC was positively correlated, and the relevant molecular mechanism requires further investigations.

BACKGROUND: The transcription factor nuclear factor-kappaB (NF-kappaB) has been implicated in gastric cancer metastasis, but the underlying molecular mechanisms remain unclear. We investigated the role of the interaction between NF-kappaB and signal transducers and activators of transcription 3 (STAT3) in controlling metastatic potential of gastric cancer cells. METHODS: Immunohistochemistry for NF-kappaB p65 (RelA), phospho-Tyr705-STAT3 (pSTAT3), or matrix metalloproteinase 9 (MMP9) was performed on tissue array slides containing 255 gastric carcinoma specimens. NF-kappaB inhibition in SNU-638 and MKN1 gastric cancer cell lines were performed by transduction with a retroviral vector containing NF-kappaB repressor mutant of IkappaBalpha, and STAT3 was silenced by RNA interference. We also did luciferase reporter assay, double immunofluorescence staining and immunoblotting. Cell migration and invasion were determined by wound-healing assay and invasion assay, respectively. RESULTS: NF-kappaB and STAT3 were constitutively activated and were positively correlated (P=0.038) in gastric cancer tissue specimens. In cell culture experiments, NF-kappaB inhibition reduced STAT3 expression and activation, whereas STAT3 silencing did not affect NF-kappaB activation. Moreover, both NF-kappaB inhibition and STAT3 silencing decreased gastric cancer cell migration and invasion in a synergistic manner. In addition, both NF-kappaB activation and STAT3 activation were positively correlated with MMP9 in gastric cancer tissues (P=0.001 and P=0.022, respectively), decreased E-cadherin expression and increased Snail and MMP9 expressions in cultured cells. CONCLUSION: NF-kappaB and STAT3 are positively associated and synergistically contribute to the metastatic potential of gastric cancer cells. Thus, dual use of NF-kappaB and STAT3 inhibitors may enhance the efficacy of the anti-metastatic treatment of gastric cancer.

This study aims to explore the detailed signal transduction mechanism of epidermal growth factor receptor (EGFR)/signal transducers and activators of transcription 3 (STAT3) that contributes to the progression of gastric cancer (GC). The STAT3 expression, phosphorylated STAT3 (pSTAT3) expression, and EGFR expression were evaluated by using molecular detection methods of GC tissues, adjacent non-tumor tissues, GC cell lines, and normal gastric cell line. Cetuximab was administered in each cell line to demonstrate the correlations among the above biomarkers. Survival and relationship analyses were adopted to demonstrate the important mechanism of EGFR/STAT3 signaling pathway contributing to the progression of GC. STAT3 expression, pSTAT3 expression, and EGFR expression in GC tissues were significantly higher than those in adjacent non-tumor tissues, respectively. Similarly, we found that STAT3 expression, pSTAT3 expression, and EGFR expression were much higher in GC cell lines than those in GES-1 cell line. With cetuximab administration, both STAT3 expression and pSTAT3 expression in all GC cell lines decreased simultaneously. With Cox proportional hazards model analysis, pSTAT3 expression was identified as the independent predictors of the overall survival of GC patients, as was EGFR expression. Furthermore, we found that there were significant associations between STAT3 expression, pSTAT3 expression, EGFR expression, and lymph node metastasis in GC tissues. The activation of EGFR/STAT3 signaling pathway may contribute to lymph node metastasis, which can promote the progression of GC.

Suppressor of cytokine signaling-3 (SOCS-3), a multifunctional cytokine, is able to inhibit cell growth and migration by blocking the Janus kinase signal transducers and activators of transcription signaling (JAK/STAT) activation in oncogenesis. Although the STAT-3 expression was associated with lymph node metastasis from gastric cancer (GC), the implication of SOCS-3 expression in GC is not clearly elucidated. In this study, SOCS-3, STAT-3, and pSTAT-3 were evaluated in GC tissues and adjacent non-tumor tissues of 107 patients who underwent curative surgery by immunohistochemistry. Further, SOCS-3 and STAT-3 mRNA levels were also detected simultaneously. In addition, survival analysis was performed between clinicopathologic variables and prognosis of GC patients. Finally, correlative analysis was adopted for demonstration the best predicator of the survival independent factor. From the results, we demonstrated that only the lymph node metastasis was the independent predictor of the overall survival (OS) of GC patients, although SOCS-3, STAT-3, and other variables were significantly relative to OS. With multivariate logistical regression analysis, SOCS-3, STAT-3, and the status of extragastric nodal metastasis were identified to be the independent factors of the lymph node metastasis from GC. Ultimately, the SOCS-3 was the best predicator of lymph node metastasis from GC identified with the nominal regression analysis. Therefore, SOCS-3 should be considered as a potential indicator for prediction the lymph node metastasis from GC.

OBJECTIVE: To investigate the expression of STAT3 and P-STAT3 and the relationship between P-STAT3 and various clinical pathological characteristics in human laryngeal carcinoma. METHOD: The expression of STAT3 and its activated form P-STAT3 in tumor tissues from 50 radically resected specimens of laryngeal carcinoma and 10 normal laryngeal tissues was detected by immunohistochemical staining. RESULT: The rate of protein expression of STAT3 and P-STAT3 in laryngeal carcinoma were 36/50 (72.0%) and 29/50 (58.0%) respectively, which were significantly higher than that in normal group (P < 0.01). The positive rate of P-STAT3 was closely related to the clinical stage and lymph node metastasis (P < 0.05). The expression STAT3 in laryngeal carcinoma was located in the cytoplasm of carcinoma cells, while P-STAT3 was located in the cell nucleus. CONCLUSION: STAT3 and PSTAT3 were overexpressed in human laryngeal carcinoma. Activation of STAT3 was significantly related to the clinical stage and lymph node metastasis. The expression of STAT3 can be used as a significant parameter in predicting the biological behaviour of laryngeal carcinoma.

OBJECTIVE: To explore the relationship between the expression of EGFR and STAT3 in human laryngeal papilloma and its biological behavior. METHOD: Reverse transcription polymerase chain reaction(RT-PCR), immunohistochemical staining and Western blot were used to evaluate the mRNA and protein expression of EGFR and STAT3 (p-STAT3) in 42 laryngeal papilloma tissues and 15 samples of normal laryngeal tissue, and the relationship between the protein expression of them and clinic pathological parameters was also analyzed. RESULT: The mRNA expression levels of EGFR and STAT3 in laryngeal papilloma tissue were significantly higher than that in normal laryngeal tissue (P < 0.05, P < 0.01). Protein positive expression of EGFR and p-STAT3 were also detected in a significantly greater proportion of laryngeal papilloma than normal laryngeal tissue by immunohistochemistry and western blot (P < 0.01, P < 0.05). There was relationship between EGFR and p-STAT3 overexpression in laryngeal papilloma (P < 0.05). The expression p-STAT3 was correlated with the recurrence and canceration of laryngeal papilloma (P < 0.05). CONCLUSION: The EGFR-STAT3 signal transduction pathway may be involved in the pathogenesis of laryngeal papilloma,, and the persistent activation of STAT3 gene plays an important role in the recurrence and canceration of laryngeal papilloma.

Recent studies underscore the importance of myeloid cells in rendering distant organs hospitable for disseminating tumor cells to colonize. However, what enables myeloid cells to have an apparently superior capacity to colonize distant organs is unclear. Here, we show that S1PR1-STAT3 upregulation in tumor cells induces factors that activate S1PR1-STAT3 in various cells in premetastatic sites, leading to premetastatic niche formation. Targeting either S1PR1 or STAT3 in myeloid cells disrupts existing premetastatic niches. S1PR1-STAT3 pathway enables myeloid cells to intravasate, prime the distant organ microenvironment and mediate sustained proliferation and survival of their own and other stromal cells at future metastatic sites. Analyzing tumor-free lymph nodes from cancer patients shows elevated myeloid infiltrates, STAT3 activity, and increased survival signal.

BACKGROUND: To examine the expression of signal transducer and activator of transcription 3 (STAT3) and its activated form (p-STAT3), Twist, and E-cadherin in hepatocellular carcinoma (HCC), and explore their correlations with HCC progression and prognosis. MATERIALS AND METHODS: The expression profiles of STAT3, p-STAT3, Twist, and E-cadherin were assessed on 100 clinical HCC samples and 10 normal liver tissues by using an immunohistochemical staining method, and their correlations with clinicopathologic parameters and survival of HCC patients were statistically analyzed. RESULTS: The results demonstrated that the positive rate of STAT3, p-STAT3, and Twist in HCC was significantly higher than that in normal liver tissues; furthermore, 52% of HCC lesions showed reduced E-cadherin expression. Correlation analysis indicated that p-STAT3 was positively correlated with Twist expression, whereas Twist was negatively correlated with E-cadherin expression; p-STAT3, Twist, or E-cadherin expression was significantly associated with HCC invasion and metastasis. Survival analysis showed that HCC patients with p-STAT3, Twist positive expression, or reduced E-cadherin expression had a significantly shorter survival duration than those with p-STAT3, Twist negative expression, or those with normal E-cadherin expression. Multivariate analysis identified p-STAT3, Twist, or E-cadherin expression as an independent prognostic factor for overall survival of HCC patients after surgery. CONCLUSIONS: By this study, we suggest that activated STAT3 signal may associate with Twist and E-cadherin expression and mediate HCC invasiveness and metastasis; abnormal p-STAT3/Twist/E-cadherin signal axis may predict poor prognosis of HCC patients.

Interleukin-22 (IL-22), one of the cytokines secreted by T helper 17 (Th17) cells, was recently reported to be a novel inflammation driver through STAT3 signaling activation. We aimed to investigate the role of IL-22 expression in hepatocellular carcinoma (HCC). We demonstrated significant up-regulation of IL-22 in human HCC tumor infiltrated leukocytes (TILs) compared to peripheral lymphocytes. Moreover, IL-22 expression was significantly higher in Edmondson Grade III-IV HCC patients versus Grade I-II, confirmed by both real-time polymerase chain reaction and immunohistochemistry. Both IL-22 receptor alpha and IL-23 were highly expressed in HCC and adjacent cirrhotic tissues compared to normal controls. Enhanced tumor growth and metastasis was found in mice that underwent subrenal transplantation of MHCC-97H cells cotransplanted with IL-22+ TILs cells. STAT3 phosphorylation and up-regulation of downstream genes Bcl-2, Bcl-XL, CyclinD1, and vascular endothelial growth factor (VEGF) promoted tumor growth and metastasis. In vitro studies confirmed the tumor-promoting and antiapoptotic effect of IL-22, as well as IL-6. In the mouse chronic hepatitis and HCC model, sustained and increased IL-22 expression and STAT3 activation were found in liver tissues. A linear correlation was demonstrated between IL-22 expression and hepatic complementary proliferation. An in vivo diethyl-nitrosamine-induced mouse HCC model verified that tumor formation was significantly decreased in IL-22 knockout mice. CONCLUSION: Excessive IL-22 can be found in the HCC microenvironment, leading to tumor growth, inhibition of apoptosis, and promotion of metastasis due to STAT3 activation.

Signal transducer and activator of transcription 3 (STAT3) is aberrantly activated in human cancer including lung cancer and has been implicated in transformation, tumorigenicity, and metastasis. One putative downstream gene regulated by Stat3 is MUC1 which also has important roles in tumorigenesis. We determined if Stat3 regulates MUC1 in lung cancer cell lines and what function MUC1 plays in lung cancer cell biology. We examined MUC1 expression in non-small cell lung cancer (NSCLC) cell lines and found high levels of MUC1 protein expression associated with higher levels of tyrosine phosphorylated STAT3. STAT3 knockdown downregulated MUC1 expression whereas constitutive STAT3 expression increased MUC1 expression at mRNA and protein levels. MUC1 knockdown induced cellular apoptosis concomitant with reduced Bcl-XL and sensitized cells to cisplatin treatment. MUC1 knockdown inhibited tumor growth and metastasis in an orthotopic mouse model of lung cancer by activating apoptosis and inhibiting cell proliferation in vivo. These results demonstrate that constitutively activated STAT3 regulates expression of MUC1, which mediates lung cancer cell survival and metastasis in vitro and in vivo. MUC1 appears to be a cooperating oncoprotein with multiple oncogenic tyrosine kinase pathways and could be an effective target for the treatment of lung cancer.

BACKGROUND AND OBJECTIVE: Signal transducer and activator of transcription (STAT) 3, a member of the STAT family of transcription factors in the Janus kinase (JAK)/STAT signaling pathway, is involved in cell proliferation and apoptosis. STAT3 is activated through phosphorylation (p-STAT3) and is highly expressed in many malignancies. The aims of the present study were to evaluate STAT3 activation (p-STAT3 protein levels) in lung adenocarcinoma and squamous cell carcinoma, and to investigate its correlation with clinicopathologic features of these malignancies. METHODS: expression of p-STAT3 was detected by immunohistochemistry in tissue from 127 lung carcinomas (100 adenocarcinomas and 27 squamous cell carcinomas) and 56 normal lungs. Genomic DNA was extracted from frozen patient tissue samples, and key epidermal growth factor receptor (EGFR) mutation sites in exons 18 through 21 of the EGFR gene were amplified and sequenced. RESULTS: On the basis of the intensity and percentage of p-STAT3 immunoreactivity, samples were divided into negative and positive p-STAT3 expression groups. 103 of these 183 samples (56.3%) showed immunoreactivity for p-STAT3, and this frequency was significantly increased in carcinoma tissue compared with normal tissue (p = 0.001). Positive p-STAT3 expression was detected in 82 of the 127 carcinomas (64.6%) but in only 21 of the 56 normal tissue samples (37.5%). Among the 127 cases of non-small cell lung cancer, p-STAT3 immunoreactivity was significantly correlated with sex (p = 0.004), smoking history (p = 0.006), EGFR mutation status (p = 0.003), clinical stage (p = 0.034), and lymph node metastasis (p = 0.009). CONCLUSION: Our results suggest that p-STAT3 is an important factor during carcinogenesis and metastasis of lung carcinoma, and its relationship to EGFR mutation status may provide potential targeting opportunities in future therapies.

PURPOSE: The signal transducer and activator of transcription 3 (STAT3) is a key molecular hub of tumorigenesis and immune suppression. The expression of phosphorylated STAT3 (p-STAT3) has been shown to be higher in melanoma metastasis to the central nervous system (CNS) relative to distant metastasis in the rest of the body (systemic). We sought to determine whether the increased expression of p-STAT3 in non-CNS systemic melanoma metastasis is associated with an increased risk of developing CNS metastasis and is a negative prognostic factor for overall survival time. METHODS: We retrospectively identified 299 patients with stage IV melanoma. In a tissue microarray of systemic non-CNS metastasis specimens from these patients, we used immunohistochemical analysis to measure the percentage of cells with p-STAT3 expression and Kaplan-Meier survival estimates to analyze the association of p-STAT3 expression with median survival time, time to first CNS metastasis, and development of CNS metastasis. RESULTS: Lung metastases exhibited the highest level of p-STAT3 expression while spleen lesions had the lowest. The p-STAT3 expression was not associated with an increased risk of developing CNS metastasis or time to CNS metastasis. However, p-STAT3 expression was a negative prognostic factor for overall survival time in patients that did not develop CNS metastasis. CONCLUSIONS: Stage IV melanoma patients without CNS metastasis treated with p-STAT3 inhibitors in efficacy studies should be stratified based on tumor expression of p-STAT3; however since p-STAT3 expression is not associated with the risk of CNS disease, increased MRI surveillance of the brain is not likely necessary.

CONTEXT: Signal transducer and activator of transcription 3 (STAT3) is constitutively activated in diverse human cancers and plays a critical role in tumor cell survival, proliferation, migration, invasion, angiogenesis, and inhibition of apoptosis. The phosphorylated active form of STAT3 (pSTAT3) mediates its effects via nuclear transcriptional activity. However, it was recently observed that the nonphosphorylated, cytoplasmic, inactive form of STAT3 is involved in cell motility and consequently tumor invasion. It appears that, although STAT3 is not absolutely required for tumor formation, tumors that develop in the presence of STAT3 become dependent on its expression for their survival, making it a potential therapeutic target. OBJECTIVE: To investigate the possible utility of STAT3 as a future therapeutic target in non-small cell lung carcinoma (NSCLC) and malignant mesothelioma (MM). DESIGN: Immunohistochemical expression of MIB-1, STAT3, and pSTAT3 was assessed in 303 NSCLC and 44 MM archival cases. RESULTS: A more conspicuous expression of inactive STAT3 (91.44% in NSCLC and 79.5% in MM cases) was present compared with the nuclear activated form pSTAT3 (60.53% in NSCLC and 61.4% in MM cases). MIB-1 did not correlate with the expression of STAT3 or pSTAT3. CONCLUSIONS: The strong expression of cytoplasmic inactive STAT3 in NSCLC and MM cases implies a major role for STAT3 in tumor motility, invasion, and metastasis via a nontranscriptional pathway. We conclude that STAT3 and pSTAT3 are up-regulated in a high percentage of NSCLCs and MMs, regardless of tumor type, age, sex, smoking status, stage and grade of tumor, or survival, providing a basis for therapeutic intervention.

Signal transducers and activators of transcription 3 (STAT3) is a central cytoplasmic transcription factor and regulates a number of pathways important in tumorigenesis including cell cycle progression, apoptosis, tumor angiogenesis, invasion and metastasis.This study aims to investigate the expression of pSTAT3, VEGF and VEGF-C in pancreatic adenocarcinoma and their relations to the clinicopathological features, tumor angiogenesis and prognosis. In the present study, the expression of pSTAT3, VEGF and VEGF-C and microvascular density (MVD) were examined via immunohistochemistry. The clinicopathological information was collected and patients were regularly followed up. The relationship between the parameters and the clinicopathological features were analyzed, and the univariate and multivariate prognostic factors were also analyzed. The expression of pSTAT3 in tumor tissues was significantly higher in contrast to that in normal tissues, and pSTAT3 was related to VEGF and VEGF-C expression, MVD, tumor size, lymphogenous status and TNM staging (P<0.05). Survival analysis suggested that tumor size, TNM staging, pSTAT3 and VEGF expression were risk factors of prognosis, but no independent factors were found. We concluded that pSTAT3, which was a risk factor of prognosis, was abnormally expressed in pancreatic adenocarcinoma and related to tumor size, TNM staging and lymphatic metastasis. pSTAT3 may promote tumor angiogenesis via up-regulating VEGF on protein and even gene levels, and enhance the early lymphatic metastasis through VEGF-C. Better understanding of STAT3 signaling pathways in angiogenesis may contribute to the development of novel therapeutic strategies in angiogenesis and metastasis of pancreatic cancer.

Signal transducer and activator of transcription 3 (STAT3) is a latent cytoplasmic transcription factor, originally discovered as a transducer of signal from cell surface receptors to the nucleus. It is activated by tyrosine phosphorylation at position 705 leading to its dimerization, nuclear translocation, DNA binding, and activation of gene transcription. Under normal physiological conditions, STAT3 activation is tightly regulated. However, compelling evidence suggests that STAT3 is constitutively activated in many cancers and plays a pivotal role in tumor growth and metastasis. It regulates cellular proliferation, invasion, migration, and angiogenesis that are critical for cancer metastasis. In this paper, we first describe the mechanism of STAT3 regulation followed by how STAT3 is involved in cancer metastasis, then we summarize the various small molecule inhibitors that inhibit STAT3 signaling.

Recent studies underscore the importance of myeloid cells in rendering distant organs hospitable for disseminating tumor cells to colonize. However, what enables myeloid cells to have an apparently superior capacity to colonize distant organs is unclear. Here, we show that S1PR1-STAT3 upregulation in tumor cells induces factors that activate S1PR1-STAT3 in various cells in premetastatic sites, leading to premetastatic niche formation. Targeting either S1PR1 or STAT3 in myeloid cells disrupts existing premetastatic niches. S1PR1-STAT3 pathway enables myeloid cells to intravasate, prime the distant organ microenvironment and mediate sustained proliferation and survival of their own and other stromal cells at future metastatic sites. Analyzing tumor-free lymph nodes from cancer patients shows elevated myeloid infiltrates, STAT3 activity, and increased survival signal.

Ovarian cancer is the most lethal gynecologic malignancy in women. Despite the fact that the metastatic spread is associated with the majority of deaths from ovarian cancer, the molecular mechanisms regulating the invasive and metastatic phenotypes of ovarian cancer are poorly understood. In this study, we demonstrated that BLT2, a low affinity leukotriene B(4) receptor, is highly expressed in OVCAR-3 and SKOV-3 human ovarian cancer cells, and that this receptor plays a key role in the invasiveness and metastasis of these cells through activation of STAT3 and consequent up-regulation of matrix metalloproteinase 2 (MMP2). In addition, our results suggest that activation of NAD(P)H oxidase-4 (NOX4) and subsequent reactive oxygen species (ROS) generation lie downstream of BLT2, mediating the stimulation of STAT3-MMP2 cascade in this process. For example, knockdown of BLT2 or NOX4 using each specific siRNA suppressed STAT3 stimulation and MMP2 expression. Similarly, inhibition of STAT3 suppressed the expression of MMP2, thus leading to attenuated invasiveness of these ovarian cancer cells. Finally, the metastasis of SKOV-3 cells in nude mice was markedly suppressed by pharmacological inhibition of BLT2. Together, our results implicate a BLT2-NOX4-ROS-STAT3-MMP2 cascade in the invasiveness and metastasis of ovarian cancer cells.

expression of vascular endothelial growth factor (VEGF), a key angiogenic protein, has been linked with pancreatic cancer progression. However, the molecular basis for VEGF overexpression remains unclear. Immunohistochemical studies have indicated that VEGF overexpression coincides with elevated Stat3 activation in human pancreatic cancer specimens. In our study, more than 80% of the human pancreatic cancer cell lines used exhibited constitutively activated Stat3, with Stat3 activation correlated with the VEGF expression level. Blockade of activated Stat3 via ectopic expression of dominant-negative Stat3 significantly suppressed VEGF expression, angiogenesis, tumor growth, and metastasis in vivo. Furthermore, constitutively activated Stat3 directly activated the VEGF promoter, whereas dominant-negative Stat3 inhibited the VEGF promoter. A putative Stat3-responsive element on the VEGF promoter was identified using a protein-DNA binding assay and confirmed using a promoter mutagenesis assay. These results indicate that Stat3 directly regulates VEGF expression and hence angiogenesis, growth, and metastasis of human pancreatic cancer, suggesting that Stat3 signaling may be targeted for treatment of pancreatic cancer.

Chronic pancreatitis is a well-known risk factor for pancreatic ductal adenocarcinoma (PDA) development in humans, and inflammation promotes PDA initiation and progression in mouse models of the disease. However, the mechanistic link between inflammatory damage and PDA initiation is unclear. Using a Kras-driven mouse model of PDA, we establish that the inflammatory mediator Stat3 is a critical component of spontaneous and pancreatitis-accelerated PDA precursor formation and supports cell proliferation, metaplasia-associated inflammation, and MMP7 expression during neoplastic development. Furthermore, we show that Stat3 signaling enforces MMP7 expression in PDA cells and that MMP7 deletion limits tumor size and metastasis in mice. Finally, we demonstrate that serum MMP7 level in human patients with PDA correlated with metastatic disease and survival.

Signal transducers and activators of transcription 3 (STAT3) is a central cytoplasmic transcription factor and regulates a number of pathways important in tumorigenesis including cell cycle progression, apoptosis, tumor angiogenesis, invasion and metastasis.This study aims to investigate the expression of pSTAT3, VEGF and VEGF-C in pancreatic adenocarcinoma and their relations to the clinicopathological features, tumor angiogenesis and prognosis. In the present study, the expression of pSTAT3, VEGF and VEGF-C and microvascular density (MVD) were examined via immunohistochemistry. The clinicopathological information was collected and patients were regularly followed up. The relationship between the parameters and the clinicopathological features were analyzed, and the univariate and multivariate prognostic factors were also analyzed. The expression of pSTAT3 in tumor tissues was significantly higher in contrast to that in normal tissues, and pSTAT3 was related to VEGF and VEGF-C expression, MVD, tumor size, lymphogenous status and TNM staging (P<0.05). Survival analysis suggested that tumor size, TNM staging, pSTAT3 and VEGF expression were risk factors of prognosis, but no independent factors were found. We concluded that pSTAT3, which was a risk factor of prognosis, was abnormally expressed in pancreatic adenocarcinoma and related to tumor size, TNM staging and lymphatic metastasis. pSTAT3 may promote tumor angiogenesis via up-regulating VEGF on protein and even gene levels, and enhance the early lymphatic metastasis through VEGF-C. Better understanding of STAT3 signaling pathways in angiogenesis may contribute to the development of novel therapeutic strategies in angiogenesis and metastasis of pancreatic cancer.

There are currently no effective therapies for metastatic prostate cancer because the molecular mechanisms that underlie the metastatic spread of primary prostate cancer are unclear. Transcription factor Stat3 is constitutively active in malignant prostate epithelium, and its activation is associated with high histological grade and advanced cancer stage. In this work, we hypothesized that Stat3 stimulates metastatic progression of prostate cancer. We show that Stat3 is active in 77% of lymph node and 67% of bone metastases of clinical human prostate cancers. Importantly, adenoviral gene delivery of wild-type Stat3 (AdWTStat3) to DU145 human prostate cancer cells increased the number of lung metastases by 33-fold in an experimental metastasis assay compared with controls. Using various methods to inhibit Stat3, we demonstrated that Stat3 promotes human prostate cancer cell migration. Stat3 induced the formation of lamellipodia in both DU145 and PC-3 cells, further supporting the concept that Stat3 promotes a migratory phenotype of human prostate cancer cells. Moreover, Stat3 caused the rearrangement of cytoplasmic actin stress fibers and microtubules in both DU145 and PC-3 cells. Finally, inhibition of the Jak2 tyrosine kinase decreased both activation of Stat3 and prostate cancer cell motility. Collectively, these data indicate that transcription factor Stat3 is involved in metastatic behavior of human prostate cancer cells and may provide a therapeutic target to prevent metastatic spread of primary prostate cancer.

Identification of the molecular changes that promote viability and metastatic behavior of prostate cancer is critical for the development of improved therapeutic interventions. Stat5a/b and Stat3 are both constitutively active in locally-confined and advanced prostate cancer, and both transcription factors have been reported to be critical for the viability of prostate cancer cells. We recently showed that Stat3 promotes metastatic behavior of human prostate cancer cells not only in vitro but also in an in vivo experimental metastases model. In this work, we compare side-by-side Stat5a/b versus Stat3 in the promotion of prostate cancer cell viability, tumor growth, and induction of metastatic colonization in vivo. Inhibition of Stat5a/b induced massive death of prostate cancer cells in culture and reduced both subcutaneous and orthotopic prostate tumor growth, whereas Stat3 had a predominant role over Stat5a/b in promoting metastases formation of prostate cancer cells in vivo in nude mice. The molecular mechanisms underlying the differential biological effects induced by these two transcription factors involve largely different sets of genes regulated by Stat5a/b versus Stat3 in human prostate cancer model systems. Of the two Stat5 homologs, Stat5b was more important for supporting growth of prostate cancer cells than Stat5a. This work provides the first mechanistic comparison of the biological effects induced by transcription factors Stat5a/b versus Stat3 in prostate cancer.

PURPOSE: To clarify the effect of genetic polymorphisms on the response to interferon alfa (IFN-alpha) for metastatic renal cell carcinoma (MRCC), and to find a reliable molecular marker to select those patients with MRCC who would benefit from IFN-alpha immunotherapy. PATIENTS AND METHODS: We carried out an association study in which 463 single nucleotide polymorphisms (SNPs) in 33 candidate genes were genotyped in 75 Japanese patients who had received IFN-alpha for MRCC. RESULTS: After adjusting for lung metastasis, stepwise logistic regression analysis revealed that the SNPs in signal transducer and activator 3 (STAT3) were most significantly associated with better response to IFN-alpha. Linkage disequilibrium mapping revealed that the SNP in the 5' region of STAT3, rs4796793, was the most significant predictor of IFN-alpha response (odds ratio [OR] = 2.73; 95% CI, 1.38 to 5.78). The highest OR was shown in the CC genotype at rs4796793 compared to the GG + GC genotypes (OR = 8.38, 95% CI, 1.63 to 42.96). Genotype-dependent expressions of STAT3 in B lymphocyte cell lines and the enhanced growth inhibitory effects of IFN- by STAT3 suppression in an RCC cell line supported the results of the present association study. CONCLUSION: The present study suggested that the STAT3 polymorphism is a useful diagnostic marker to predict the response to IFN-alpha therapy in patients with MRCC. An efficient response marker for IFN-alpha needs to be utilized to establish individual optimal treatment strategies, even when newer drug therapies are used as first line treatments for MRCC.

BACKGROUND: In our 2007 retrospective study, we reported that single nucleotide polymorphisms (SNPs) in the signal transducer and activator of transcription 3 (acute-phase response factor) (STAT3) gene were significantly associated with better response to interferon (IFN)-alpha in patients with metastatic renal cell carcinoma (mRCC). OBJECTIVE: To prospectively confirm those results, the Japan Immunotherapy SNPs-Study Group for Kidney cancer conducted this trial. DESIGN, SETTING, AND PARTICIPANTS: In this multicenter, prospective study, 203 eligible patients were enrolled. We evaluated the correlation between the antitumor effects of IFN-alpha and 11 SNPs (STAT3-2, STAT3-0, SOCS3-1, IL4R-34, PTGS1-3, PTGS1-4, PTGS1-5, PTGS2-12, IRF2-67, ICSBP-38, and TAP2-5) in eight genes in 180 patients who received IFN-alpha for >12 wk. INTERVENTIONS: Patients were treated with three doses per week of IFN-alpha 5 million IU. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: We analyzed the association of response to IFN-alpha and overall survival (OS) with genetic polymorphisms using a chi-square test and a logistic regression model. RESULTS AND LIMITATIONS: The response rate of IFN-alpha was 13.8% (28 of 203 patients; 9 complete responses [CRs], 19 partial responses [PRs]). The CR rate of 4.4% was higher than we expected. Response to IFN-alpha was not associated with any of the 11 SNPs examined. However, when we assessed patients with CR, PR, and stable disease >24 wk as a group representing those with clinical response, a significant association was observed between STAT3-2 (rs1905341) and the clinical response of IFN-alpha (p=0.039). Namely, C/C genotype of STAT3-2 was significantly associated with the clinical response of IFN-alpha and OS. These results were generated in Japanese patients and should be studied in other ethnic groups. CONCLUSIONS: This is the first prospective study demonstrating that a STAT3 polymorphism can be a predictive marker for treatment with IFN-alpha for patients with mRCC.

PURPOSE: To investigate the expression profiles of IL-6 and STAT3 in Wilms' tumor (WT) and their relationship with disease progression. METHODS: Immunohistochemistry was used to examine IL-6 and STAT3 expression in 58 primary tumors and 18 invasive/metastatic ones. RESULTS: Positive expression rate of IL-6/STAT3 was 39.7% (23/58)/29.3% (17/58) in primary WT tissues, while 61.1% (11/18)/33.3% (6/18) in associated invasive/metastatic tissues. The expression rate of IL-6 and STAT3 was higher in primary WT tumors of invasive/metastatic group than that of non-invasive/metastatic group (P=0.033; P=0.012). There was a positive correlation between IL-6 and STAT3 expression in 76 WT tissues (P<0.001, r=0.444). The expression of IL-6 /STAT3 between primary WT and matched invasive/metastatic tissues was concordance (P=0.727; P=0.99). IL-6 expression status and histopathological type were associated with disease-free survival (DFS) and overall survival (OS) (P<0.05), while STAT3 was only correlated with DFS (P<0.05). CONCLUSIONS: IL-6 and STAT3 expression in WT might be correlated with progression and predict unfavorable prognosis, highlighting a new therapy target for invasive or metastatic WTs.