Epidermal growth factor-induced ovarian carcinoma cell migration is associated with JAK2/STAT3 signals and changes in the abundance and localization of alpha6beta1 integrin. Int J Biochem Cell Biol. 2009;41:1034-1045. [PMID: 18930836 DOI: 10.1016/j.biocel.2008.09.018]

Small Molecule Inhibitors for Hepatocellular Carcinoma: Advances and Challenges

According to data provided by World Health Organization, hepatocellular carcinoma (HCC) is the sixth most common cause of deaths due to cancer worldwide. Tremendous progress has been achieved over the last 10 years developing novel agents for HCC treatment, including small-molecule kinase inhibitors. Several small molecule inhibitors currently form the core of HCC treatment due to their versatility since they would be more easily absorbed and have higher oral bioavailability, thus easier to formulate and administer to patients. In addition, they can be altered structurally to have greater volumes of distribution, allowing them to block extravascular molecular targets and to accumulate in a high concentration in the tumor microenvironment. Moreover, they can be designed to have shortened half-lives to control for immune-related adverse events. Most importantly, they would spare patients, healthcare institutions, and society as a whole from the burden of high drug costs. The present review provides an overview of the pharmaceutical compounds that are licensed for HCC treatment and other emerging compounds that are still investigated in preclinical and clinical trials. These molecules are targeting different molecular targets and pathways that are proven to be involved in the pathogenesis of the disease.

STAT3-EMT axis in tumors: Modulation of cancer metastasis, stemness and therapy response

Epithelial-to-mesenchymal transition (EMT) mechanism is responsible for metastasis of tumor cells and their spread to various organs and tissues of body, providing undesirable prognosis. In addition to migration, EMT increases stemness and mediates therapy resistance. Hence, pathways involved in EMT regulation should be highlighted. STAT3 is an oncogenic pathway that can elevate growth rate and migratory ability of cancer cells and induce drug resistance. The inhibition of STAT3 signaling impairs cancer progression and promotes chemotherapy-mediated cell death. Present review focuses on STAT3 and EMT interaction in modulating cancer migration. First of all, STAT3 is an upstream mediator of EMT and is able to induce EMT-mediated metastasis in brain tumors, thoracic cancers and gastrointestinal cancers. Therefore, STAT3 inhibition significantly suppresses cancer metastasis and improves prognosis of patients. EMT regulators such as ZEB1/2 proteins, TGF-β, Twist, Snail and Slug are affected by STAT3 signaling to stimulate cancer migration and invasion. Different molecular pathways such as miRNAs, lncRNAs and circRNAs modulate STAT3/EMT axis. Furthermore, we discuss how STAT3 and EMT interaction affects therapy response of cancer cells. Finally, we demonstrate targeting STAT3/EMT axis by anti-tumor agents and clinical application of this axis for improving patient prognosis.

The SH2 domain and kinase activity of JAK2 target JAK2 to centrosome and regulate cell growth and centrosome amplification

JAK2 is cytokine-activated non-receptor tyrosine kinase. Although JAK2 is mainly localized at the plasma membrane, it is also present on the centrosome. In this study, we demonstrated that JAK2 localization to the centrosome depends on the SH2 domain and intact kinase activity. We created JAK2 mutants deficient in centrosomal localization ΔSH2, K882E and (ΔSH2, K882E). We showed that JAK2 WT clone strongly enhances cell proliferation as compared to control cells while JAK2 clones ΔSH2, K882E and (ΔSH2, K882E) proliferate slower than JAK2 WT cells. These mutant clones also progress much slower through the cell cycle as compared to JAK2 WT clone and the enhanced proliferation of JAK2 WT cells is accompanied by increased S -> G2 progression. Both the SH2 domain and the kinase activity of JAK2 play a role in prolactin-dependent activation of JAK2 substrate STAT5. We showed that JAK2 is an important regulator of centrosome function as the SH2 domain of JAK2 regulates centrosome amplification. The cells overexpressing ΔSH2 and (ΔSH2, K-E) JAK2 have almost three-fold the amplified centrosomes of WT cells. In contrast, the kinase activity of JAK2 is dispensable for centrosome amplification. Our observations provide novel insight into the role of SH2 domain and kinase activity of JAK2 in centrosome localization of JAK2 and in the regulation of cell growth and centrosome biogenesis.

A novel small molecule LLL12B inhibits STAT3 signaling and sensitizes ovarian cancer cell to paclitaxel and cisplatin

Ovarian cancer is the fifth most common cause of cancer deaths among American women. Platinum and taxane combination chemotherapy represents the first-line approach for ovarian cancer, but treatment success is often limited by chemoresistance. Therefore, it is necessary to find new drugs to sensitize ovarian cancer cells to chemotherapy. Persistent activation of Signal Transducer and Activator of Transcription 3 (STAT3) signaling plays an important role in oncogenesis. Using a novel approach called advanced multiple ligand simultaneous docking (AMLSD), we developed a novel nonpeptide small molecule, LLL12B, which targets the STAT3 pathway. In this study, LLL12B inhibited STAT3 phosphorylation (tyrosine 705) and the expression of its downstream targets, which are associated with cancer cell proliferation and survival. We showed that LLL12B also inhibits cell viability, migration, and proliferation in human ovarian cancer cells. LLL12B combined with either paclitaxel or with cisplatin demonstrated synergistic inhibitory effects relative to monotherapy in inhibiting cell viability and LLL12B-paclitaxel or LLL12B-cisplatin combination exhibited greater inhibitory effects than cisplatin-paclitaxel combination in ovarian cancer cells. Furthermore, LLL12B-paclitaxel or LLL12B-cisplatin combination showed more significant in inhibiting cell migration and growth than monotherapy in ovarian cancer cells. In summary, our results support the novel small molecule LLL12B as a potent STAT3 inhibitor in human ovarian cancer cells and suggest that LLL12B in combination with the current front-line chemotherapeutic drugs cisplatin and paclitaxel may represent a promising approach for ovarian cancer therapy.

The potential function of miR-135b-mediated JAK2/STAT3 signaling pathway during osteoblast differentiation

MC3T3-E1 cells were divided into Blank, miR-135b mimics, miR-135b inhibitors, AG490, and miR-135b inhibitors + AG490 groups. Cell viability was determined by MTT, alkaline phosphatase (ALP) activity by the corresponding kit, and mineralization by alizarin red staining. Furthermore, miR-135b, osteoblast-specific genes, and JAK2/STAT3 were detected through quantitative real-time polymerase chain reaction and Western blotting. MiR-135b downregulation was identified with increased JAK2 during osteoblast differentiation. JAK2 was confirmed as a target gene of miR-135b by dual-luciferase reporter assay. MC3T3-E1 cells in both miR-135b mimics and AG490 groups manifested decrease in cell viability, ALP activity, and mineralized nodes, as well as reductions in osteoblast-specific genes and proteins of JAK2, p-JAK2, and p-STAT3, but increase in cell apoptosis. However, opposite changes of the above factors were shown in cells from miR-135b inhibitors group. Notably, AG490 could reverse promotion effects of miR-135b inhibitors on osteoblast differentiation. Inhibiting miR-135b could activate the JAK2/STAT3 signaling pathway, thereby improving the cell viability and promoting the osteoblast differentiation.

Association of low expression of E-cadherin and β-catenin with the progression of early stage human squamous cervical cancer

The precise involvement and mechanisms of human papilloma virus type 16 (HPV16) in epithelial-mesenchymal transition (EMT) of cervical intraepithelial neoplasia (CIN) and squamous cervical cancer (SCC) remain unknown. The present study aimed to examine the expression of EMT indicators and their association with HPV16 in CIN and early stage SCC, and their prognostic value in early stage SCC. The expression levels of E-cadherin, N-cadherin, β-catenin, vimentin, and fibronectin were determined by immunohistochemistry in 40 patients with normal uterine cervix, 22 patients with CIN1, 60 patients with CIN2-3, and 86 patients with SCC, stage Ia-IIa, according to the International Federation of Gynecology and Obstetrics. The expression of the epithelial indicators E-cadherin and β-catenin gradually declined, and the mesenchymal indicators N-cadherin, vimentin, and fibronectin increased with progression of the cervical lesions (P<0.05). Patients with SCC with lymph node metastasis, parametrial invasion, negative E-cadherin, and negative β-catenin expression had shorter overall survival (P=0.001, P=0.015, P=0.014, and P=0.043, respectively) and disease-free survival (P=0.002, P=0.021, P=0.025, and P=0.045, respectively) time. Multivariate survival analysis indicated that lymph node metastasis [Hazard ratio (HR)=3.544; P=0.010], parametrial invasion (HR=2.014; P=0.007) and E-cadherin expression (HR=0.163; P<0.001) were independently associated with overall survival, but also with disease-free survival (HR=3.612, P=0.009; HR=1.935, P=0.011; HR=0.168, P<0.001, respectively). In patients with CINs, HPV16 infection was negatively correlated with the expression of E-cadherin, and positively correlated with the expression of N-cadherin, vimentin, and fibronectin. EMT occurs during the progression of CINs to early stage SCC, and is associated with HPV16 infection in CINs. Lymph node metastasis and parametrial invasion are poor prognostic factors for SCC, while positive E-cadherin expression may serve as a protective prognostic factor for SCC.

ALDH1A2 suppresses epithelial ovarian cancer cell proliferation and migration by downregulating STAT3

Epithelial ovarian cancer is the deadliest gynecological malignancy worldwide. A better understanding of epithelial ovarian cancer pathogenesis and the molecular mechanism underlying its metastasis may increase overall survival rates. Previous studies have indicated that aldehyde dehydrogenase 1 family member A2 (ALDH1A2) is a candidate tumor suppressor in epithelial ovarian cancer. However, the potential role of ALDH1A2 in the molecular mechanisms of epithelial ovarian cancer remains largely unclear. In the present study, we found lower expression of ALDH1A2 in high-grade epithelial ovarian cancer tissues than in low-grade epithelial ovarian cancer tissues. Overexpression of ALDH1A2 decreased the proliferation and migration of epithelial ovarian cancer cell lines, whereas ALDH1A2 knockdown significantly increased cell growth and migration. Moreover, upregulation of ALDH1A2 also reduced the activation of signal transducer and activator of transcription 3 (STAT3). In conclusion, these findings suggest that ALDH1A2 suppresses epithelial ovarian cancer cell proliferation and migration by downregulating STAT3.

Epithelial-to-Mesenchymal Transition in the Female Reproductive Tract: From Normal Functioning to Disease Pathology

Epithelial-to-mesenchymal transition (EMT) is a physiological process that is vital throughout the human lifespan. In addition to contributing to the development of various tissues within the growing embryo, EMT is also responsible for wound healing and tissue regeneration later in adulthood. In this review, we highlight the importance of EMT in the development and normal functioning of the female reproductive organs (the ovaries and the uterus) and describe how dysregulation of EMT can lead to pathological conditions, such as endometriosis, adenomyosis, and carcinogenesis. We also summarize the current literature relating to EMT in the context of ovarian and endometrial carcinomas, with a particular focus on how molecular mechanisms and the tumor microenvironment can govern cancer cell plasticity, therapy resistance, and metastasis.

Effect of siRNA-mediated inhibition of KLF17 expression on cell proliferation and migration in human colon cancer cell line SW480

AIM

To inhibit Krüppel like factor 17 (KLF17) gene expression in human colorectal carcinoma SW480 cells by small interfering RNA (siRNA) technique, and thereby observe the effect of KLF17 gene silencing on the proliferation and migration of SW480 cells, in order to provide the theoretical foundation for inhibiting the recurrence and metastasis of colorectal cancer.

METHODS

A KLF17 siRNA eukaryotic plasmid expression vector was constructed using genetic recombination, which was then transfected into SW480 cells by electroporation. Fluorescence quantitative PCR was used to detect the mRNA expression levels of KLF17, E-cadherin and Vimentin, while the protein expression of KLF17, E-cadherin and Vimentin was detected by Western blot. The proliferative activity of SW480 cells was assayed by MTT assay.

RESULTS

Compared with the control group, the proliferation ability of siRNA-transfected SW480 cells was significantly suppressed, and the cell morphology changed from round or polygonal to fusiform and cells developed many projections. After siRNA transfection, the mRNA and protein expression levels of KLF17 and E-cadherin were significantly decreased, and the levels of Vimentin mRNA and protein expression were significantly increased in the siRNA interference group.

CONCLUSION

Down-regulation of KLF17 expression in human colorectal carcinoma SW480 cells may promote cell proliferation and enhance cell migration by inducing epithelial-mesenchymal transition.

Amphiregulin enhances alpha6beta1 integrin expression and cell motility in human chondrosarcoma cells through Ras/Raf/MEK/ERK/AP-1 pathway

Chondrosarcoma is a malignant tumor that produces cartilage matrix. The most lethal aspect is its metastatic property. We demonstrated that amphiregulin (AR) is significantly upregulated in highly aggressive cells. AR silencing markedly suppressed cell migration. Exogenous AR markedly increased cell migration by transactivation of α6β1 integrin expression. A neutralizing α6β1 integrin antibody can abolish AR-induced cell motility. Knockdown of AR inhibits metastasis of cells to the lung in vivo. Furthermore, elevated AR expression is positively correlated with α6β1 integrin levels and higher grades in patients. These findings can potentially serve as biomarker and therapeutic approach for controlling chondrosarcoma metastasis.

Lysine-specific demethylase 1 mediates epidermal growth factor signaling to promote cell migration in ovarian cancer cells

Epigenetic abnormalities play a vital role in the progression of ovarian cancer. Lysine-specific demethylase 1 (LSD1/KDM1A) acts as an epigenetic regulator and is overexpressed in ovarian tumors. However, the upstream regulator of LSD1 expression in this cancer remains elusive. Here, we show that epidermal growth factor (EGF) signaling upregulates LSD1 protein levels in SKOV3 and HO8910 ovarian cancer cells overexpressing both LSD1 and the EGF receptor. This effect is correlated with a decrease in the dimethylation of H3K4, a major substrate of LSD1, in an LSD1-dependent manner. We also show that inhibition of PI3K/AKT, but not MEK, abolishes the EGF-induced upregulation of LSD1 and cell migration, indicating that the PI3K/PDK1/AKT pathway mediates the EGF-induced expression of LSD1 and cell migration. Significantly, LSD1 knockdown or inhibition of LSD1 activity impairs both intrinsic and EGF-induced cell migration in SKOV3 and HO8910 cells. These results highlight a novel mechanism regulating LSD1 expression and identify LSD1 as a promising therapeutic target for treating metastatic ovarian cancer driven by EGF signaling.

OCT4 mediates FSH-induced epithelial-mesenchymal transition and invasion through the ERK1/2 signaling pathway in epithelial ovarian cancer

Our previous study showed that Octamer-binding transcription factor 4 (OCT4) expression was upregulated and significantly associated with histological grade through the analysis of OCT4 expression in 159 ovarian cancer tissue samples, and OCT4 mediated follicle-stimulating hormone (FSH)-induced anti-apoptosis in epithelial ovarian cancer. Nevertheless, whether OCT4 participates in FSH-induced invasion in ovarian cancer is still unknown. Therefore, the present study aimed to define whether FSH-induced ovarian cancer invasion is mediated by OCT4. In present study, we showed that FSH induced not only the epithelial-mesenchymal transition (EMT) and invasive phenotype but also the upregulation of OCT4 expression in a dose- and time-dependent manner in epithelial ovarian cancer cells. In addition, the expression of FSH receptor (FSHR) was upregulated by FSH induction, and knockdown of FSHR inhibited FSH-stimulated OCT4 expression. ERK1/2 signaling pathway participated in the enhanced expression of OCT4 and Snail induced by FSH. We further showed that the activated expression of Snail and N-cadherin, the suppressed expression of E-cadherin and the morphological change of the cells stimulated by FSH were blocked by OCT4-specific small interfering RNA. Moreover, our results showed that OCT4 mediated the increase in invasive capacity induced by FSH in ovarian cancer cells. Taken together, our work reveals that OCT4 is an essential mediator in FSH-induced EMT and invasion in epithelial ovarian cancer and may act as a potential therapeutic target.

Adaptive Upregulation of EGFR Limits Attenuation of Tumor Growth by Neutralizing IL6 Antibodies, with Implications for Combined Therapy in Ovarian Cancer

Excess production of the proinflammatory IL6 has both local and systemic tumor-promoting activity in many cancers, including ovarian cancer. However, treatment of advanced ovarian cancer patients with a neutralizing IL6 antibody yielded little efficacy in a previous phase II clinical trial. Here, we report results that may explain this outcome, based on the finding that neutralizing antibodies to IL6 and STAT3 inhibition are sufficient to upregulate the EGFR pathway in high-grade serous and other ovarian cancer cells. Cell treatment with the EGFR inhibitor gefitinib abolished upregulation of the EGFR pathway. Combining neutralizing IL6 antibodies and gefitinib inhibited malignant cell growth in 2D and 3D culture. We found that ErbB-1 was localized predominantly in the nucleus of ovarian cancer cells examined, contrasting with plasma membrane localization in lung cancer cells. Treatment with anti-IL6, gefitinib, or their combination all led to partial restoration of ErbB-1 on the plasma membrane. In vivo experiments confirmed the effects of IL6 inhibition on the EGFR pathway and the enhanced activity of a combination of anti-IL6 antibodies and gefitinib on malignant cell growth. Taken together, our results offer a preclinical rationale to combine anti-IL6 and gefitinib to treat patients with advanced stage ovarian cancer.

Macrophage-secreted IL-8 induces epithelial-mesenchymal transition in hepatocellular carcinoma cells by activating the JAK2/STAT3/Snail pathway

Macrophages are a major component of the leukocyte infiltrate of tumors and play a pivotal role in the progression of hepatocellular carcinoma (HCC). However, the molecular mechanisms by which macrophages promote HCC invasion are poorly understood. The present study was undertaken to investigate the relationship between macrophages and epithelial-mesenchymal transition (EMT) of HCC. Double-staining immunohistochemistry was used to observe the association between macrophages and EMT markers in clinical HCC samples and it showed that EMT primarily occurred at the edge of the tumor nest, in which infiltrating macrophages were always observed. This indicated that CD68 which is a marker of macrophages, was correlated with EMT marker levels. In addition, after being cultured with macrophages for 24 h, the ability of HCC cells to migrate and invade increased, Snail and N-Cadherin expression was upregulated, and E-Cadherin was downregulated. An antibody array assay was applied to analyze the supernatant of these cultures and it demonstrated IL-8 increased significantly in the macrophage co-culture system. Finally, the role of macrophage-derived IL-8 in the invasion of HCC cells was assayed, and downstream signaling pathways were also investigated. We found that IL-8: i) may induce EMT and promote HCC cell migration and invasion and ii) is associated with the JAK2/STAT3/Snail signaling pathway. Taking together, these findings revealed that macrophages that have infiltrated tumors may induce epithelial-mesenchymal transition of HCC cells via the IL-8 activated JAK2/STAT3/Snail pathway. Thus, this may offer a potential target for developing new HCC therapies.

CCR7 regulates cell migration and invasion through JAK2/STAT3 in metastatic squamous cell carcinoma of the head and neck

Squamous cell carcinoma of the head and neck (SCCHN) frequently involves metastasis at diagnosis. Our previous research has demonstrated that CCR7 plays a key role in regulating SCCHN metastasis, and this process involves several molecules, such as PI3K/cdc42, pyk2, and Src. In this study, the goals are to identify whether JAK2/STAT3 also participates in CCR7's signal network, its relationship with other signal pathways, and its role in SCCHN cell invasion and migration. The results showed that stimulation of CCL19 could induce JAK2/STAT3 phosphorylation, which can be blocked by Src and pyk2 inhibitors. After activation, STAT3 was able to promote low expression of E-cadherin and had no effect on vimentin. This JAk2/STAT3 pathway not only mediated CCR7-induced cell migration but also mediated invasion speed. The immunohistochemistry results also showed that the phosphorylation of STAT3 was correlated with CCR7 expression in SCCHN, and CCR7 and STAT3 phosphorylation were all associated with lymph node metastasis. In conclusion, JAk2/STAT3 plays a key role in CCR7 regulating SCCHN metastasis.

Amphiregulin induces human ovarian cancer cell invasion by down-regulating E-cadherin expression

Aberrant epidermal growth factor receptor (EGFR) activation is associated with ovarian cancer progression. In this study, we report that the EGFR ligand amphiregulin (AREG) stimulates cell invasion and down-regulates E-cadherin expression in two human ovarian cancer cell lines, SKOV3 and OVCAR5. In addition, AREG increases the expression of transcriptional repressors of E-cadherin including SNAIL, SLUG and ZEB1. siRNA targeting SNAIL or SLUG abolishes AREG-induced cell invasion. Moreover, ERK1/2 and AKT pathways are involved in AREG-induced E-cadherin down-regulation and cell invasion. Finally, we show that three EGFR ligands, AREG, epidermal growth factor (EGF) and transforming growth factor-α (TGF-α), exhibit comparable effects in down-regulating E-cadherin and promoting cell invasion. This study demonstrates that AREG induces ovarian cancer cell invasion by down-regulating E-cadherin expression.

Tie2-dependent deletion of α6 integrin subunit in mice reduces tumor growth and angiogenesis

The α6 integrin subunit (α6) has been implicated in cancer cell migration and in the progression of several malignancies, but its role in tumor angiogenesis is unclear. In mice, anti-α6 blocking antibodies reduce tumor angiogenesis, whereas Tie1-dependent α6 gene deletion enhances neovessel formation in melanoma and lung carcinoma. To clarify the discrepancy in these results we used the cre-lox system to generate a mouse line, α6fl/fl‑Tie2Cre(+), with α6 gene deletion specifically in Tie2-lineage cells: endothelial cells, pericytes, subsets of hematopoietic stem cells, and Tie2-expressing monocytes/macrophages (TEMs), known for their proangiogenic properties. Loss of α6 expression in α6fl/fl‑Tie2Cre(+) mice reduced tumor growth in a murine B16F10 melanoma model. Immunohistological analysis of the tumors showed that Tie2-dependent α6 gene deletion was associated with reduced tumor vascularization and with reduced infiltration of proangiogenic Tie2-expressing macrophages. These findings demonstrate that α6 integrin subunit plays a major role in tumor angiogenesis and TEM infiltration. Targeting α6 could be used as a strategy to reduce tumor growth.

SC-2001 overcomes STAT3-mediated sorafenib resistance through RFX-1/SHP-1 activation in hepatocellular carcinoma

Hepatocellular carcinoma is the fifth most common solid cancer worldwide. Sorafenib, a small multikinase inhibitor, is the only approved therapy for advanced HCC. The clinical benefit of sorafenib is offset by the acquisition of sorafenib resistance. Understanding of the molecular mechanism of STAT3 overexpression in sorafenib resistance is critical if the clinical benefits of this drug are to be improved. In this study, we explored our hypothesis that loss of RFX-1/SHP-1 and further increase of p-STAT3 as a result of sorafenib treatment induces sorafenib resistance as a cytoprotective response effect, thereby, limiting sorafenib sensitivity and efficiency. We found that knockdown of RFX-1 protected HCC cells against sorafenib-induced cell apoptosis and SHP-1 activity was required for the process. SC-2001, a molecule with similar structure to obatoclax, synergistically suppressed tumor growth when used in combination with sorafenib in vitro and overcame sorafenib resistance through up-regulating RFX-1 and SHP-1 resulting in tumor suppression and mediation of dephosphorylation of STAT3. In addition, sustained sorafenib treatment in HCC led to increased p-STAT3 which was a key mediator of sorafenib sensitivity. The combination of SC-2001 and sorafenib strongly inhibited tumor growth in both wild-type and sorafenib-resistant HCC cell bearing xenograft models. These results demonstrate that inactivation of RFX/SHP-1 induced by sustained sorafenib treatment confers sorafenib resistance to HCC through p-STAT3 up-regulation. These effects can be overcome by SC-2001 through RFX-1/SHP-1 dependent p-STAT3 suppression. In conclusion, the use of SC-2001 in combination with sorafenib may constitute a new strategy for HCC therapy.

Honokiol inhibits epithelial-mesenchymal transition in breast cancer cells by targeting signal transducer and activator of transcription 3/Zeb1/E-cadherin axis

Epithelial-mesenchymal transition (EMT), a critical step in the acquisition of metastatic state, is an attractive target for therapeutic interventions directed against tumor metastasis. Honokiol (HNK) is a natural phenolic compound isolated from an extract of seed cones from Magnolia grandiflora. Recent studies from our lab show that HNK impedes breast carcinogenesis. Here, we provide molecular evidence that HNK inhibits EMT in breast cancer cells resulting in significant downregulation of mesenchymal marker proteins and concurrent upregulation of epithelial markers. Experimental EMT induced by exposure to TGFβ and TNFα in spontaneously immortalized nontumorigenic human mammary epithelial cells is also completely reversed by HNK as evidenced by morphological as well as molecular changes. Investigating the downstream mediator(s) that may direct EMT inhibition by HNK, we found functional interactions between HNK, Stat3, and EMT-signaling components. In vitro and in vivo analyses show that HNK inhibits Stat3 activation in breast cancer cells and tumors. Constitutive activation of Stat3 abrogates HNK-mediated activation of epithelial markers whereas inhibition of Stat3 using small molecule inhibitor, Stattic, potentiates HNK-mediated inhibition of EMT markers, invasion and migration of breast cancer cells. Mechanistically, HNK inhibits recruitment of Stat3 on mesenchymal transcription factor Zeb1 promoter resulting in decreased Zeb1 expression and nuclear translocation. We also discover that HNK increases E-cadherin expression via Stat3-mediated release of Zeb1 from E-cadherin promoter. Collectively, this study reports that HNK effectively inhibits EMT in breast cancer cells and provide evidence for a previously unrecognized cross-talk between HNK and Stat3/Zeb1/E-cadherin axis.

SH2B1β interacts with STAT3 and enhances fibroblast growth factor 1-induced gene expression during neuronal differentiation

Neurite outgrowth is an essential process during neuronal differentiation as well as neuroregeneration. Thus, understanding the molecular and cellular control of neurite outgrowth will benefit patients with neurological diseases. We have previously shown that overexpression of the signaling adaptor protein SH2B1β promotes fibroblast growth factor 1 (FGF1)-induced neurite outgrowth (W. F. Lin, C. J. Chen, Y. J. Chang, S. L. Chen, I. M. Chiu, and L. Chen, Cell. Signal. 21:1060-1072, 2009). SH2B1β also undergoes nucleocytoplasmic shuttling and regulates a subset of neurotrophin-induced genes. Although these findings suggest that SH2B1β regulates gene expression, the nuclear role of SH2B1β was not known. In this study, we show that SH2B1β interacts with the transcription factor, signal transducer, and activator of transcription 3 (STAT3) in neuronal PC12 cells, cortical neurons, and COS7 fibroblasts. By affecting the subcellular distribution of STAT3, SH2B1β increased serine phosphorylation and the concomitant transcriptional activity of STAT3. As a result, overexpressing SH2B1β enhanced FGF1-induced expression of STAT3 target genes Egr1 and Cdh2. Chromatin immunoprecipitation assays further reveal that, in response to FGF1, overexpression of SH2B1β promotes the in vivo occupancy of STAT3-Sp1 heterodimers at the promoter of Egr1 and Cdh2. These findings establish a central role of SH2B1β in orchestrating signaling events to transcriptional activation through interacting and regulating STAT3-containing complexes during neuronal differentiation.

Type I interferon-mediated pathway interacts with peroxisome proliferator activated receptor-γ (PPAR-γ): at the cross-road of pancreatic cancer cell proliferation

Pancreatic adenocarcinoma remains an unresolved therapeutic challenge because of its intrinsically refractoriness to both chemo- and radiotherapy due to the complexity of signaling and the activation of survival pathways in cancer cells. Recent studies have demonstrated that the combination of some drugs, targeting most of aberrant pathways crucial for the survival of pancreatic cancer cells may be a valid antitumor strategy for this cancer. Type I interferons (IFNs) may have a role in the pathogenesis and progression of pancreatic adenocarcinoma, but the limit of their clinical use is due to the activation of tumor resistance mechanisms, including JAK-2/STAT-3 pathway. Moreover, aberrant constitutive activation of STAT-3 proteins has been frequently detected in pancreatic adenocarcinoma. The selective targeting of these cell survival cascades could be a promising strategy in order to enhance the antitumor effects of type I IFNs. The activation of peroxisome proliferator-activated receptor γ (PPAR-γ), on the other hand, has a suppressive activity on STAT-3. In fact, PPAR-γ agonists negatively modulate STAT-3 through direct and/or indirect mechanisms in several normal and cancer models. This review provides an overview on the current knowledge about the molecular mechanisms and antitumor activity of these two promising classes of drugs for pancreatic cancer therapy. Finally, the synergistic antiproliferative activity of combined IFN-β and troglitazone treatment on pancreatic cancer cell lines, evaluated in vitro, and the consequent potential clinical applications will be discussed.

A mechanism for epithelial-mesenchymal transition and anoikis resistance in breast cancer triggered by zinc channel ZIP6 and STAT3 (signal transducer and activator of transcription 3)

Genes involved in normal developmental processes attract attention as mediators of tumour progression as they facilitate migration of tumour cells. EMT (epithelial–mesenchymal transition), an essential part of embryonic development, tissue remodelling and wound repair, is crucial for tumour metastasis. Previously, zinc transporter ZIP6 [SLC39A6; solute carrier family 39 (zinc transporter), member 6; also known as LIV-1) was linked to EMT in zebrafish gastrulation through a STAT3 (signal transducer and activator of transcription 3) mechanism, resulting in nuclear localization of transcription factor Snail. In the present study, we show that zinc transporter ZIP6 is transcriptionally induced by STAT3 and unprecedented among zinc transporters, and is activated by N-terminal cleavage which triggers ZIP6 plasma membrane location and zinc influx. This zinc influx inactivates GSK-3β (glycogen synthase kinase 3β), either indirectly or directly via Akt or GSK-3β respectively, resulting in activation of Snail, which remains in the nucleus and acts as a transcriptional repressor of E-cadherin (epithelial cadherin), CDH1, causing cell rounding and detachment. This was mirrored by ZIP6-transfected cells which underwent EMT, detached from monolayers and exhibited resistance to anoikis by their ability to continue proliferating even after detachment. Our results indicate a causative role for ZIP6 in cell motility and migration, providing ZIP6 as a new target for prediction of clinical cancer spread and also suggesting a ZIP6-dependent mechanism of tumour metastasis.

We demonstrate a novel mechanism for the ability of cellular zinc to drive cell detachment and migration with implications for breast cancer spread. This mechanism involves a zinc uptake channel ZIP6 (also known as SLC39A6) and a transcription factor, STAT3.

Differential mitochondrial proteome analysis of human lung adenocarcinoma and normal bronchial epithelium cell lines using quantitative mass spectrometry

BACKGROUND

Lung cancer is one of the higher incidences of malignant tumors around the world. At present, tumor markers CEA, CA19-9, and CA-125 in serum are used for the diagnosis of lung cancer, however, fewer studies have shown tumor markers for early diagnosis. Therefore, using quantitative mass spectrometry, differential mitochondrial proteome analysis was performed, comparing human lung adenocarcinoma and normal bronchial epithelium cells.

METHODS

A human lung adenocarcinoma cell line A549 and a normal human bronchial epithelial cell line 16HBE were cultured in vitro. The cell mitochondria of the two cell lines were extracted and purified by differential centrifugation and percoll density gradient centrifugation. The integrity and purity of mitochondria were validated by electron microscopy and Western-blot. The proteins/peptides from lung cancer cells and normal cells were marked by the same amount of relative and absolute quantification of ectopic tags (iTRAQ). The mixed samples were analyzed and identified by two-dimensional liquid chromatography - tandem mass spectrometry (2D-LC-MS/MS). The proteome was analyzed with different bioinformatic tools.

RESULTS

One hundred and sixty-one mitochondrial proteins were identified. One hundred and fifty-three mitochondrial proteins, which were expressed differently between 16HBE cells and A549 cells, were identified. Sixty-seven proteins were high expression, while 86 proteins were lower expression. Expression of three proteins: ornithine aminotransferase (OAT), heat shock protein beta90 (HSP90), and vimentin (VIM), was increased more than twice. Our results, in combination with the literature review, suggest that HSP90 and Vimentin may be the new tumor markers of lung cancer.

Early responses of the STAT3 pathway to platinum drugs are associated with cisplatin resistance in epithelial ovarian cancer

Cisplatin resistance remains one of the major obstacles when treating epithelial ovarian cancer. Because oxaliplatin and nedaplatin are effective against cisplatin-resistant ovarian cancer in clinical trials and signal transducer and activator of transcription 3 (STAT3) is associated with cisplatin resistance, we investigated whether overcoming cisplatin resistance by oxaliplatin and nedaplatin was associated with the STAT3 pathway in ovarian cancer. Alamar blue, clonogenic, and wound healing assays, and Western blot analysis were used to compare the effects of platinum drugs in SKOV-3 cells. At an equitoxic dose, oxaliplatin and nedaplatin exhibited similar inhibitory effects on colony-forming ability and greater inhibition on cell motility than cisplatin in ovarian cancer. Early in the time course of drug administration, cisplatin increased the expression of pSTAT3 (Tyr705), STAT3α, VEGF, survivin, and Bcl-X_L, while oxaliplatin and nedaplatin exhibited the opposite effects, and upregulated pSTAT3 (Ser727) and STAT3β. The STAT3 pathway responded early to platinum drugs associated with cisplatin resistance in epithelial ovarian cancer and provided a rationale for new therapeutic strategies to reverse cisplatin resistance.

Inhibitory effects of STAT3 decoy oligodeoxynucleotides on human epithelial ovarian cancer cell growth in vivo

The signal transducer and activator of transcription 3 (STAT3) regulates target gene expression by binding to a consensus DNA sequence within the promoter of the target genes. The constitutive activation of STAT3 has been shown to contribute to tumorigenesis in ovarian cancer and it has been reported to be a key factor for drug resistance in ovarian cancer. STAT3-specific decoy oligodeoxynucleotides (ODNs) (STAT3 decoy ODNs) that contain a consensus DNA sequence inhibit the transcriptional activity of STAT3, leading to cancer cell death. However, their mechanisms of action are unclear and little information is available as to the effects and the toxicity of STAT3 decoy ODNs in vivo. In this study, we established subcutaneous xenografts of SKOV3 human ovarian cancer cells in nude mice, evaluated the antitumor effects of STAT3 decoy ODNs on xenografted nude mice, and investigated the mechanisms behind the antitumor effects of STAT3 decoy ODNs targeting the STAT3 signaling pathway in vivo. The results revealed that the STAT3 decoy ODN inhibited ovarian cancer cell growth and promoted ovarian cancer cell apoptosis in vivo. Western blot analysis indicated that the STAT3 decoy ODN downregulated the protein expression levels of matrix metalloproteinase (MMP)-2, MMP-9 and Bcl-2, and upregulated the protein expression levels of caspase-3 in vivo. H&E staining was used to detect the side-effects of the STAT3 decoy ODN in the vital organs of the nude mice. We found that there were no significant abnormalities in the vital organs of the nude mice apart from slight inflammation and necrosis in parts of the hepatic lobule. The data from the present study suggest that decoy ODNs targeting STAT3 may be an effective therapeutic approach for the treatment of ovarian cancer in vivo.

Ovarian cancer molecular pathology

Ovarian cancer (OVC) is the fourth leading cause of cancer mortality among women in Europe and the United States. Its early detection is difficult due to the lack of specificity of clinical symptoms. Unfortunately, late diagnosis is a major contributor to the poor survival rates for OVC, which can be attributed to the lack of specific sets of markers. Aside from patients sharing a strong family history of ovarian and breast cancer, including the BRCA1 and BRCA2 tumor suppressor genes mutations, the most used biomarker is the Cancer-antigen 125 (CA-125). CA-125 has a sensitivity of 80 % and a specificity of 97 % in epithelial cancer (stage III or IV). However, its sensitivity is 30 % in stage I cancer, as its increase is linked to several physiological phenomena and benign situations. CA-125 is particularly useful for at-risk population diagnosis and to assess response to treatment. It is clear that alone, CA-125 is inadequate as a biomarker for OVC diagnosis. There is an unmet need to identify additional biomarkers. Novel and more sensitive proteomic strategies such as MALDI mass spectrometry imaging studies are well suited to identify better markers for both diagnosis and prognosis. In the present review, we will focus on such proteomic strategies in regards to OVC signaling pathways, OVC development and escape from the immune response.

Epidermal growth factor upregulates endometrial CYR61 expression via activation of the JAK2/STAT3 pathway

Endometrial cysteine-rich protein 61 (CYR61, CCN1) is a growth factor-inducible gene whose expression is elevated during the proliferative phase of the menstrual cycle and which has been implicated in the pathogenesis of endometriosis. This study aimed to define the mediators of epidermal growth factor (EGF) signalling on CYR61 expression in spontaneously immortalised human endometrial epithelial cells (HES) as a model system. After 30 min of EGF treatment, the receptor was phosphorylated and internalised as well as mRNA CYR61 increased in HES cells. However, neither inhibition of C-terminal EGF receptor (EGFR)-phosphorylation nor blockage of the mitogen-activated proteinkinase/extracellular signal-regulated kinase (MAPK/ERK) pathway was able to reduce CYR61 levels. Surprisingly, the HES cells showed upregulation of CYR61 mRNA expression after inhibition of the MAPK/ERK pathway when treated with EGF. Specific inhibitor studies identified the contribution of Janus kinase 2 (JAK2) and the signal transducer and activator of transcription protein STAT3 to the regulation of CYR61 expression. The JAK2/STAT3 interaction contributed to the basal expression of CYR61 and mediated EGF-driven regulation of CYR61 after 30 and 120 min of treatment. In summary, EGF-mediated CYR61 upregulation in HES cells involves STAT3 and is counter-regulated by the EGFR/MAPK/ERK pathway.

Integrin β1 mediates epithelial growth factor-induced invasion in human ovarian cancer cells

Integrins function as cell-extracellular matrix adhesion proteins and have been implicated in tumor progression. In ovarian tumors, elevated integrin β1 expression correlates with high clinical stage and poor patient survival. In this study, we report that EGF treatment up-regulated integrin β1 mRNA and protein levels in ovarian cancer cells. Moreover, pharmacological inhibition of MEK totally abolished EGF-induced integrin β1 up-regulation and cell invasion suggesting that MAPK/ERK signaling is required for EGF-induced integrin β1 up-regulation and cell invasion. Furthermore, we found that knockdown of integrin β1 expression reduced the intrinsic invasiveness of ovarian cancer cells and the EGF-induced cell invasion. Finally, we found that overexpression of integrin β1 was sufficient to promote ovarian cancer cell invasion. This study demonstrates that integrin β1 mediates EGF-induced cell invasion in ovarian cancer.

Optimizing molecular-targeted therapies in ovarian cancer: the renewed surge of interest in ovarian cancer biomarkers and cell signaling pathways

The hallmarks of ovarian cancer encompass the development of resistance, disease recurrence and poor prognosis. Ovarian cancer cells express gene signatures which pose significant challenges for cancer drug development, therapeutics, prevention and management. Despite enhancements in contemporary tumor debulking surgery, tentative combination regimens and abdominal radiation which can achieve beneficial response rates, the majority of ovarian cancer patients not only experience adverse effects, but also eventually relapse. Therefore, additional therapeutic possibilities need to be explored to minimize adverse events and prolong progression-free and overall response rates in ovarian cancer patients. Currently, a revival in cancer drug discovery is devoted to identifying diagnostic and prognostic ovarian cancer biomarkers. However, the sensitivity and reliability of such biomarkers may be complicated by mutations in the BRCA1 or BRCA2 genes, diverse genetic risk factors, unidentified initiation and progression elements, molecular tumor heterogeneity and disease staging. There is thus a dire need to expand existing ovarian cancer therapies with broad-spectrum and individualized molecular targeted approaches. The aim of this review is to profile recent developments in our understanding of the interrelationships among selected ovarian tumor biomarkers, heterogeneous expression signatures and related molecular signal transduction pathways, and their translation into more efficacious targeted treatment rationales.

Cell death induced by the Jak2 inhibitor, G6, correlates with cleavage of vimentin filaments

Hyperkinetic Jak2 tyrosine kinase signaling has been implicated in several human diseases including leukemia, lymphoma, myeloma, and the myeloproliferative neoplasms. Using structure-based virtual screening, we previously identified a novel Jak2 inhibitor named G6. We showed that G6 specifically inhibits Jak2 kinase activity and suppresses Jak2-mediated cellular proliferation. To elucidate the molecular and biochemical mechanisms by which G6 inhibits Jak2-mediated cellular proliferation, we treated Jak2-V617F expressing human erythroleukemia (HEL) cells for 12 h with either vehicle control or 25 μM of the drug and compared protein expression profiles using two-dimensional gel electrophoresis. One differentially expressed protein identified by electrospray mass spectroscopy was the intermediate filament protein, vimentin. It was present in DMSO treated cells but absent in G6 treated cells. HEL cells treated with G6 showed both time- and dose-dependent cleavage of vimentin as well as a marked reorganization of vimentin intermediate filaments within intact cells. In a mouse model of Jak2-V617F mediated human erythroleukemia, G6 also decreased the levels of vimentin protein, in vivo. The G6-induced cleavage of vimentin was found to be Jak2-dependent and calpain-mediated. Furthermore, we found that intracellular calcium mobilization is essential and sufficient for the cleavage of vimentin. Finally, we show that the cleavage of vimentin intermediate filaments, per se, is sufficient to reduce HEL cell viability. Collectively, these results suggest that G6-induced inhibition of Jak2-mediated pathogenic cell growth is concomitant with the disruption of intracellular vimentin filaments. As such, this work describes a novel pathway for the targeting of Jak2-mediated pathological cell growth.

An outlook on ovarian cancer and borderline ovarian tumors: focus on genomic and proteomic findings

Among the gynaecological malignancies, ovarian cancer is one of the neoplastic forms with the poorest prognosis and with the bad overall and disease-free survival rates than other gynaecological cancers. Ovarian tumors can be classified on the basis of the cells of origin in epithelial, stromal and germ cell tumors. Epithelial ovarian tumors display great histological heterogeneity and can be further subdivided into benign, intermediate or borderline, and invasive tumors. Several studies on ovarian tumors, have focused on the identification of both diagnostic and prognostic markers for applications in clinical practice. High-throughput technologies have accelerated the process of biomolecular study and genomic discovery; unfortunately, validity of these should be still demonstrated by extensive researches on sensibility and sensitivity of ovarian cancer novel biomarkers, determining whether gene profiling and proteomics could help differentiate between patients with metastatic ovarian cancer and primary ovarian carcinomas, and their potential impact on management. Therefore, considerable interest lies in identifying molecular and protein biomarkers and indicators to guide treatment decisions and clinical follow up. In this review, the current state of knowledge about the genoproteomic and potential clinical value of gene expression profiling in ovarian cancer and ovarian borderline tumors is discussed, focusing on three main areas: distinguishing normal ovarian tissue from ovarian cancers and borderline tumors, identifying different genotypes of ovarian tissue and identifying proteins linked to cancer or tumor development. By these targets, authors focus on the use of novel molecules, developed on the proteomics and genomics researches, as potential protein biomarkers in the management of ovarian cancer or borderline tumor, overlooking on current state of the art and on future perspectives of researches.

Resveratrol inhibits the epidermal growth factor-induced epithelial mesenchymal transition in MCF-7 cells

Carcinoma progression is associated with the loss of epithelial features, and the acquisition of a mesenchymal phenotype by tumour cells. Herein we show that exposure of MCF-7 cells to epidermal growth factor (EGF) resulted in morphological alterations characteristic of epithelial-to-mesenchymal transition (EMT). EGF treatment resulted in increased motility along with an up-regulation of transcription factors Slug, Zeb1, Zeb2, and mesenchymal markers Vimentin and N-cadherin. Treatment of MCF-7 cells with a combined stimulation of EGF and resveratrol, a naturally occurring stilbene with antitumor properties, failed to alter cell morphology, motility and overexpression of EMT markers induced by EGF. Using specific chemical inhibitors, we demonstrated that EGF-induced EMT is mediated by extracellular signal-regulated kinase 1/2 (ERK 1/2) signalling pathway and that resveratrol is able to repress EGF-induced ERK activation. In summary, these data provide new evidence of the inhibitory effect of resveratrol on EGF-induced EMT cell transformation.

The tumor-suppressor gene ARHI (DIRAS3) suppresses ovarian cancer cell migration through inhibition of the Stat3 and FAK/Rho signaling pathways

Ovarian cancers migrate and metastasize over the surface of the peritoneal cavity. Consequently, dysregulation of mechanisms that limit cell migration may be particularly important in the pathogenesis of the disease. ARHI is an imprinted tumor-suppressor gene that is downregulated in >60% of ovarian cancers, and its loss is associated with decreased progression-free survival. ARHI encodes a 26-kDa GTPase with homology to Ras. In contrast to Ras, ARHI inhibits cell growth, but whether it also regulates cell motility has not been studied previously. Here we report that re-expression of ARHI decreases the motility of IL-6- and epidermal growth factor (EGF)-stimulated SKOv3 and Hey ovarian cancer cells, inhibiting both chemotaxis and haptotaxis. ARHI binds to and sequesters Stat3 in the cytoplasm, preventing its translocation to the nucleus and localization in focal adhesion complexes. Stat3 siRNA or the JAK2 inhibitor AG490 produced similar inhibition of motility. However, the combination of ARHI expression with Stat3 knockdown or inhibition produced greatest inhibition in ovarian cancer cell migration, consistent with Stat3-dependent and Stat3-independent mechanisms. Consistent with two distinct signaling pathways, knockdown of Stat3 selectively inhibited IL-6-stimulated migration, whereas knockdown of focal adhesion kinase (FAK) preferentially inhibited EGF-stimulated migration. In EGF-stimulated ovarian cancer cells, re-expression of ARHI inhibited FAK(Y397) and Src(Y416) phosphorylation, disrupted focal adhesions, and blocked FAK-mediated RhoA signaling, resulting in decreased levels of GTP-RhoA. Re-expression of ARHI also disrupted the formation of actin stress fibers in a FAK- and RhoA-dependent manner. Thus, ARHI has a critical and previously uncharacterized role in the regulation of ovarian cancer cell migration, exerting inhibitory effects on two distinct signaling pathways.

High- and low-affinity epidermal growth factor receptor-ligand interactions activate distinct signaling pathways

Signaling mediated by the Epidermal Growth Factor Receptor (EGFR) is crucial in normal development, and aberrant EGFR signaling has been implicated in a wide variety of cancers. Here we find that the high- and low-affinity interactions between EGFR and its ligands activate different signaling pathways. While high-affinity ligand binding is sufficient for activation of most canonical signaling pathways, low-affinity binding is required for the activation of the Signal transducers and activators of transcription (Stats) and Phospholipase C-gamma 1 (PLCγ1). As the Stat proteins are involved in many cellular responses including proliferation, migration and apoptosis, these results assign a function to low-affinity interactions that has been omitted from computational models of EGFR signaling. The existence of receptors with distinct signaling properties provides a way for EGFR to respond to different concentrations of the same ligand in qualitatively different ways.

TGFβ and EGF synergistically induce a more invasive phenotype of epithelial ovarian cancer cells

The epithelial-mesenchymal transition (EMT) is associated with progression and metastasis of epithelial ovarian cancer (EOC). Snail and Slug (two members of the Snail family of transcription factors) down-regulate the expression of the adhesion molecule E-cadherin and thus function as positive regulators of EMT. Their expression is associated with a more invasive phenotype of EOC. However, how their expression in EOC cells is regulated needs to be further defined. Here, we show that transforming growth factor β (TGFβ) and epidermal growth factor (EGF) synergistically induce the expression of Slug and Snail at both mRNA and protein levels in an EOC cell line OVCA429 cells. Using specific chemical inhibitors, we demonstrate that Slug and Snail expression induced by TGFβ is mediated by TGFβ/ALK5 pathway, and EGF-induced expression of Slug and Snail is MEK1/2-dependent. Interestingly, TGFβ-induced Slug expression is also MEK1/2-dependent. Further, we demonstrate that combined TGFβ and EGF stimulation is more potent than either alone in repressing the expression of E-cadherin. Functionally, combined stimulation of TGFβ and EGF enhances the mobility of OVCA429 cells and induces the production of MMP2 by OVCA429 cells more potently than either alone. Taken together, our data demonstrate that TGFβ and EGF signaling pathways synergistically induce EMT and render EOC cells a more invasive phenotype.

Hydrogen peroxide mediates EGF-induced down-regulation of E-cadherin expression via p38 MAPK and snail in human ovarian cancer cells

In ovarian cancer, it has been shown that E-cadherin is down-regulated by epidermal growth factor (EGF) receptor (EGFR) activation, and that cells with low E-cadherin expression are particularly invasive. Although it is generally believed that reactive oxygen species play important roles in intracellular signal transduction, the role of reactive oxygen species in EGF-mediated reductions in E-cadherin remains to be elucidated. In this study, we show that EGF treatment down-regulated E-cadherin by up-regulating its transcriptional repressors, Snail and Slug, in human ovarian cancer cells. Using 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate acetyl ester staining, we found that intracellular hydrogen peroxide (H(2)O(2)) production was increased in EGF-treated cells and could be inhibited by treatment with an EGFR inhibitor, AG1478, or an H(2)O(2) scavenger, polyethylene glycol (PEG)-catalase. In addition, PEG-catalase diminished EGF-induced p38 MAPK, but not ERK1/2 or c-Jun N-terminal kinase, phosphorylation. PEG-catalase and the p38 MAPK inhibitor SB203580 abolished EGF-induced Snail, but not Slug, expression and E-cadherin down-regulation. Furthermore, the involvement of p38 MAPK in the down-regulation of E-cadherin was confirmed using specific p38alpha MAPK small interfering RNA. Finally, we also show that EGF-induced cell invasion was abolished by treatment with PEG-catalase and SB203580, as well as p38alpha MAPK small interfering RNA, and that forced expression of E-cadherin diminished intrinsic invasiveness as well as EGF-induced cell invasion. This study demonstrates a novel mechanism in which EGF down-regulates E-cadherin expression through production of H(2)O(2), activation of p38 MAPK, and up-regulation of Snail in human ovarian cancer cells.

Proteomics profiling of Madin-Darby canine kidney plasma membranes reveals Wnt-5a involvement during oncogenic H-Ras/TGF-beta-mediated epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) describes a process whereby polarized epithelial cells with restricted migration transform into elongated spindle-shaped mesenchymal cells with enhanced motility and invasiveness. Although there are some molecular markers for this process, including the down-regulation of E-cadherin, our understanding of plasma membrane (PM) and associated proteins involved in EMT is limited. To specifically explore molecular alterations occurring at the PM, we used the cationic colloidal silica isolation technique to purify PM fractions from epithelial Madin-Darby canine kidney cells during Ras/TGF-β-mediated EMT. Proteins in the isolated membrane fractions were separated by one-dimensional SDS-PAGE and subjected to nano-LC-MS/MS-based protein identification. In this study, the first membrane protein analysis of an EMT model, we identified 805 proteins and determined their differential expression using label-free spectral counting. These data reveal that Madin-Darby canine kidney cells switch from cadherin-mediated to integrin-mediated adhesion following Ras/TGF-β-mediated EMT. Thus, during the EMT process, E-cadherin, claudin 4, desmoplakin, desmoglein-2, and junctional adhesion molecule A were down-regulated, whereas integrins α6β1, α3β1, α2β1, α5β1, αVβ1, and αVβ3 along with their extracellular ligands collagens I and V and fibronectin had increased expression levels. Conspicuously, Wnt-5a expression was elevated in cells undergoing EMT, and transient Wnt-5a siRNA silencing attenuated both cell migration and invasion in these cells. Furthermore, Wnt-5a expression suppressed canonical Wnt signaling induced by Wnt-3a. Wnt-5a may act through the planar cell polarity pathway of the non-canonical Wnt signaling pathway as several of the components and modulators (Wnt-5a, -5b, frizzled 6, collagen triple helix repeat-containing protein 1, tyrosine-protein kinase 7, RhoA, Rac, and JNK) were found to be up-regulated during Ras/TGF-β-mediated EMT.

Role of STAT3 decoy oligodeoxynucleotides on cell invasion and chemosensitivity in human epithelial ovarian cancer cells

Recent studies have reported that STAT3 activation is associated with poor prognosis in human epithelial ovarian cancer. STAT3 has been proposed to play an important role in ovarian cancer metastasis and chemoresistance. This mechanism, however, is still not thoroughly understood. In this study, to investigate the role of STAT3 on ovarian cancer cells, we used decoy oligodeoxynucleotide (ODN) technology to regulate STAT3 in SKOV3 and OVCAR3 cells in vitro. Cell invasive power and chemo-sensitivity were assessed in the cells transfected with STAT3 decoy ODN and control ODN. Western blot analysis was used to examine the expression of EMMPRIN, P-gp, and Akt. Results showed that STAT3 decoy ODN inhibited cancer cell invasive power and enhanced sensitivity to paclitaxel for SKOV3 and OVCAR3 cells. The mechanism involved the inhibition of EMMPRIN, P-gp, and pAkt by STAT3 decoy ODN. These three proteins were probably the target proteins of STAT3. These findings suggest that STAT3 is a key factor for ovarian cancer metastasis and chemoresistance. STAT3 decoy ODN may prove to be a beneficial therapeutic agent, especially for invasive or chemoresistant ovarian cancer.

Epithelial-mesenchymal transition in ovarian cancer

Ovarian cancer is a highly metastatic disease and the leading cause of death from gynecologic malignancy. Hence, and understanding of the molecular changes associated with ovarian cancer metastasis could lead to the identification of targets for novel therapeutic interventions. The conversion of an epithelial cell to a mesenchymal cell plays a key role both in the embryonic development and cancer invasion and metastasis. Cells undergoing epithelial-mesenchymal transition (EMT) lose their epithelial morphology, reorganize their cytoskeleton and acquire a motile phenotype through the up- and down-regulation of several molecules including tight and adherent junctions proteins and mesenchymal markers. EMT is believed to be governed by signals from the neoplastic microenvironment including a variety of cytokines and growth factors. In ovarian cancer EMT is induced by transforming growth factor-beta (TGF-beta), epidermal growth factor (EGF), hepatocyte growth factor (HGF) and endothelin-1 (ET-1). Alterations in these cellular pathways candidate them as useful target for ovarian cancer treatment.

Cross talk of signals between EGFR and IL-6R through JAK2/STAT3 mediate epithelial-mesenchymal transition in ovarian carcinomas

Epidermal growth factor receptor (EGFR) is overexpressed in ovarian carcinomas, with direct or indirect activation of EGFR able to trigger tumour growth. We demonstrate significant activation of both signal transducer and activator of transcription (STAT)3 and its upstream activator Janus kinase (JAK)2, in high-grade ovarian carcinomas compared with normal ovaries and benign tumours. The association between STAT3 activation and migratory phenotype of ovarian cancer cells was investigated by EGF-induced epithelial–mesenchymal transition (EMT) in OVCA 433 and SKOV3 ovarian cancer cell lines. Ligand activation of EGFR induced a fibroblast-like morphology and migratory phenotype, consistent with the upregulation of mesenchyme-associated N-cadherin, vimentin and nuclear translocation of β-catenin. This occurred concomitantly with activation of the downstream JAK2/STAT3 pathway. Both cell lines expressed interleukin-6 receptor (IL-6R), and treatment with EGF within 1 h resulted in a several-fold enhancement of mRNA expression of IL-6. Consistent with that, EGF treatment of both OVCA 433 and SKOV3 cell lines resulted in enhanced IL-6 production in the serum-free medium. Exogenous addition of IL-6 to OVCA 433 cells stimulated STAT3 activation and enhanced migration. Blocking antibodies against IL-6R inhibited IL-6 production and EGF- and IL-6-induced migration. Specific inhibition of STAT3 activation by JAK2-specific inhibitor AG490 blocked STAT3 phosphorylation, cell motility, induction of N-cadherin and vimentin expression and IL6 production. These data suggest that the activated status of STAT3 in high-grade ovarian carcinomas may occur directly through activation of EGFR or IL-6R or indirectly through induction of IL-6R signalling. Such activation of STAT3 suggests a rationale for a combination of anti-STAT3 and EGFR/IL-6R therapy to suppress the peritoneal spread of ovarian cancer.