Proteinase requirements of epidermal growth factor-induced ovarian cancer cell invasion

The Multifaceted Roles of Mast Cells in Immune Homeostasis, Infections and Cancers

Mast cells (MCs) play important roles in normal immune responses and pathological states. The location of MCs on the boundaries between tissues and the external environment, including gut mucosal surfaces, lungs, skin, and around blood vessels, suggests a multitude of immunological functions. Thus, MCs are pivotal for host defense against different antigens, including allergens and microbial pathogens. MCs can produce and respond to physiological mediators and chemokines to modulate inflammation. As long-lived, tissue-resident cells, MCs indeed mediate acute inflammatory responses such as those evident in allergic reactions. Furthermore, MCs participate in innate and adaptive immune responses to bacteria, viruses, fungi, and parasites. The control of MC activation or stabilization is a powerful tool in regulating tissue homeostasis and pathogen clearance. Moreover, MCs contribute to maintaining the homeostatic equilibrium between host and resident microbiota, and they engage in crosstalk between the resident and recruited hematopoietic cells. In this review, we provide a comprehensive overview of the functions of MCs in health and disease. Further, we discuss how mouse models of MC deficiency have become useful tools for establishing MCs as a potential cellular target for treating inflammatory disorders.

Characteristics of Selected Adipokines in Ascites and Blood of Ovarian Cancer Patients

Simple Summary

Ovarian cancer is at the forefront of all cancers worldwide. A specific microenvironment for the secretion of various proteins, including adipokines, is formed around the neoplastic tissue. Five of these proteins, namely adiponectin, interleukin 6 (IL-6), interleukin 8 (IL-8), monocyte chemotactic protein-1 (MCP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1), were found to have a particular effect on metastasis. The review collects data available in the literature on the function and occurrence of these cytokines in ovarian cancer. The collected information will allow for the observation of these proteins in the area of diagnostics and the planning of further scientific research, and will enable the use of the cytokine level determination as biomarkers of neoplastic disease, its progression and prognosis.

Abstract

Ovarian cancer is one of the most common malignancies among women worldwide. The course of the disease is often latent and asymptomatic in the early stages, but as it develops, metastasis occurs, accompanied by accumulation of ascites in the peritoneal cavity. The ascites fluid constitutes a specific microenvironment influencing the processes of carcinogenesis. In ascites, signaling is mediated by various cytokines that control tumor cell proliferation, progression, metastasis, and chemoresistance. Adipokines, secreted into ascites and also appearing in blood, may be markers of ongoing processes related to the development of neoplastic disease. Moreover, a significant influence of adipocyte lipids on the growth of tumors, for which they are one of energy sources, is observed. Adiponectin, interleukin 6 (IL-6), interleukin 8 (IL-8), monocyte chemotactic protein-1 (MCP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1), discussed in the present review, were found to mediate the effects of omentum metastasis through homing, migration and invasion of ovarian cancer cells. Further research on those adipokines seem to be a natural consequence, allowing for a better understanding of the mechanisms of neoplastic disease and determination of the treatment procedure.

Quantitative Analysis of Tumor-Associated Mast Cells in Recurrent and Non-recurrent Urothelial Bladder Cancer in Stage pTa and pT1

Background

Urothelial carcinoma of the urinary bladder (UCUB) is a common malignancy in both genders with a very high recurrence rate. There has been increasing evidence for a correlation between tumor-associated mast cells (TAMC) and tumor growth and recurrence rates. In the present study, we set out to establish a link between TAMC and the clinical morphological characteristics of UCUB in stages pTa and pT1.

Methodology

A retrospective non-clinical approach was used, with two groups of patients with UCUB. A total of 163 patients were included, 95 in the non-recurrent group and 68 in the recurrent UCUB group. Estimation of TAMC was performed on histological slides from the initial biopsy material using Giemsa and Toluidine blue staining. The collected data were statistically analyzed using the Kaplan-Meier curve, Mann-Whitney test, receiver operating characteristic curve, and chi-square analysis.

Results

Statistical analysis revealed that TAMC in the tumor stroma shows a positive correlation with local recurrence, with no statistical significance to the time of recurrence. No correlation showed statistical significance with pT stage, grade, gender, and age.

Conclusions

The amount of TAMC in UCUB correlates positively with the rate of local recurrence. The depicted correlations are similar to those established in mammary carcinoma, some lymphoproliferative disorders, and pancreatic and prostate malignancies.

The Many Facets of Metzincins and Their Endogenous Inhibitors: Perspectives on Ovarian Cancer Progression

Approximately sixty per cent of ovarian cancer patients die within the first five years of diagnosis due to recurrence associated with chemoresistance. The metzincin family of metalloproteinases is enzymes involved in matrix remodeling in response to normal physiological changes and diseased states. Recently, there has been a mounting awareness of these proteinases and their endogenous inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), as superb modulators of cellular communication and signaling regulating key biological processes in cancer progression. This review investigates the role of metzincins and their inhibitors in ovarian cancer. We propose that understanding the metzincins and TIMP biology in ovarian cancer may provide valuable insights in combating ovarian cancer progression and chemoresistance-mediated recurrence in patients.

RhoA/ROCK pathway mediates leptin-induced uPA expression to promote cell invasion in ovarian cancer cells

Previous studies have shown that leptin, an adipocyte-secreted hormone, stimulates ovarian cancer invasion. Here, we investigated the contribution of uPA in leptin-induced ovarian cancer cell invasion. The cell invasion and migration experiments were carried out using matrigel invasion and wound healing assays in ovarian cancer cell lines (OVCAR3, SKOV3and CaoV-3). The mechanism underlying the invasive effect of leptin was examined using cell transfection with Ob-Rb siRNA, pre-treatment with a specific inhibitor of RhoA and ROCK, RhoA activation assay, OB-Rb, Rock and upA protein expression. Our results show that leptin induced ovarian cancer cell invasion via up-regulating upA in a time and dose-dependent manner, which was attenuated using knockdown of OB-Rb by siRNA. Moreover, pre-incubation with C3 (inhibitor of RhoA) and Y-27632 (inhibitor of ROCK) effectively attenuated leptin-induced upA expression and inhibited invasive ability of ovarian cancer cells. We also found that pretreatment with inhibitors of PI3K/AKT (LY294002), JAK/STAT (AG490) and NF-kB (BAY 11-7082) significantly reduced leptin-induced upA expression. Collectively, our findings demonstrate that OB-Rb, RhoA/ROCK, PI3K/AKT, JAK/STAT pathways and NF-kB activation are involved in leptin-induced upA expression. These results may provide a new mechanism that facilitates leptin-induced ovarian cancer invasion.

COX2 and PGE2 mediate EGF-induced E-cadherin-independent human ovarian cancer cell invasion

Elevated expression of cyclooxygenase 2 (COX2 (PTGS2)) has been reported to occur in human ovarian cancer and to be associated with poor prognosis. We have previously demonstrated that COX2-derived prostaglandin E2 (PGE2) promotes human ovarian cancer cell invasion. We had also demonstrated that epidermal growth factor (EGF) induces human ovarian cancer cell invasion by downregulating the expression of E-cadherin through various signaling pathways. However, it remains unclear whether COX2 and PGE2 are involved in the EGF-induced downregulation of E-cadherin expression and cell invasion in human ovarian cancer cells. In this study, we showed that EGF treatment induces COX2 expression and PGE2 production in SKOV3 and OVCAR5 human ovarian cancer cell lines. Interestingly, COX2 is not required for the EGF-induced downregulation of E-cadherin expression. In addition, EGF treatment activates the phosphatidylinositol-3-kinase (PI3K)/Akt and cAMP response element-binding protein (CREB) signaling pathways, while only the PI3K/Akt pathway is involved in EGF-induced COX2 expression. Moreover, we also showed that EGF-induced cell invasion is attenuated by treatment with a selective COX2 inhibitor, NS-398, as well as PGE2 siRNA. This study demonstrates an important role for COX2 and its derivative, PGE2, in the mediation of the effects of EGF on human ovarian cancer cell invasion.

The complex function of hsp70 in metastatic cancer

Elevated expression of the inducible heat shock protein 70 (Hsp70) is known to correlate with poor prognosis in many cancers. Hsp70 confers survival advantage as well as resistance to chemotherapeutic agents, and promotes tumor cell invasion. At the same time, tumor-derived extracellular Hsp70 has been recognized as a "chaperokine", activating antitumor immunity. In this review we discuss localization dependent functions of Hsp70 in the context of invasive cancer. Understanding the molecular principles of metastasis formation steps, as well as interactions of the tumor cells with the microenvironment and the immune system is essential for fighting metastatic cancer. Although Hsp70 has been implicated in different steps of the metastatic process, the exact mechanisms of its action remain to be explored. Known and potential functions of Hsp70 in controlling or modulating of invasion and metastasis are discussed.

An in vitro and in vivo investigation of the antimetastatic effects of a Chinese medicinal decoction, erxian decoction, on human ovarian cancer models

OBJECTIVES

Erxian Decoction (EXD) is a well-documented Chinese medicinal formulation, which has been clinically applied for years for relieving menopausal syndromes by modulating hormonal levels indicating that EXD might also be effective in treating hormone-related tumors. This study aimed to differentially investigate the efficacy of EXD and its antimetastatic property on human ovarian cancer cells, OVCA429.

METHODS

The efficacy and cell cycle progression of EXD on OVCA429 cells was determined by MTT assay and flow cytometry, respectively. The modulated expression of metastatic markers by EXD in OVCA429 cells and xenografts was evaluated at transcriptional and translational levels by Western blotting and real-time polymerase chain reaction, respectively. The migrating and invasive ability of the cancer cells were determined by wound healing and invasive assays.

RESULTS

The IC50 value of EXD on OVCA429 cells was determined after 24 hours incubation with EXD at 1 mg/mL. EXD (1.5 mg/mL) mediated S-phase cell cycle arrest and apoptotic cell death at 24 hours posttreatment. EXD repressed the expression of several metastatic mediators, including EGFR, ErbB2, MMP2, MMP7, MMP9, and VEGF in OVCA429 cells and xenografts at transcriptional and/or translational levels. Furthermore, EXD functionally demonstrated significant inhibition of migrating and invasive ability of OVCA429 cells. EXD suppressed tumor size in xenografts without any adverse effects on body weight.

CONCLUSIONS

This is the first study that illustrates the antimetastatic property of EXD on human ovarian cancer models. This decoction merits serious consideration for further delineation of its multiple pharmacological effects, especially on hormone-related cancers, and these would be valuable for future clinical applications of EXD as an alternative regime for cancers.

ARID3B induces tumor necrosis factor alpha mediated apoptosis while a novel ARID3B splice form does not induce cell death

Alternative splicing is a common occurrence in many cancers. Alternative splicing is linked with decreased apoptosis and chemoresistance in cancer cells. We previously demonstrated that ARID3B, a member of the AT-rich interactive domain (ARID) family of DNA binding proteins, is overexpressed in ovarian cancer. Therefore we wanted to assess the effect of ARID3B splice forms on cell viability. We identified a novel splice form of the ARID3B gene (designated as ARID3B Sh), which lacks the C-terminal exons 5–9 present in the full-length isoform (ARID3B Fl). ARID3B Fl is expressed in a variety of cancer cell lines. Expression of ARID3B Sh varied by cell type, but was highly expressed in most ovarian cancer lines. ARID3B is modestly transcriptionally activated by epidermal growth factor receptor (EGFR) signaling through the PEA3 transcription factor. We further found that ARID3B Fl is predominantly nuclear but is also present at the plasma membrane and in the cytosol. Endogenous ARID3B Sh is present in nuclear fractions, yet, when overexpressed ARID3B Sh accumulates in the cytosol and membrane fractions. The differential localization of these isoforms suggests they have different functions. Importantly, ARID3B Fl overexpression results in upregulation of pro-apoptotic BIM and induces Tumor Necrosis Factor alpha (TNFα) and TNF-related apoptosis inducing ligand (TRAIL) induced cell death. The ARID3B Fl-induced genes include TNFα, TRAIL, TRADD, TNF-R2, Caspase 10 and Caspase 7. Interestingly, ARID3B Sh does not induce apoptosis or expression of these genes. ARID3B Fl induces death receptor mediated apoptosis while the novel splice form ARID3B Sh does not induce cell death. Therefore alternative splice forms of ARID3B may play different roles in ovarian cancer progression.

EGFR/HER-targeted therapeutics in ovarian cancer

Despite decades of research and evolving treatment modalities, survival among patients with epithelial ovarian cancer has improved only incrementally. During this same period, the development of biologically targeted therapeutics has improved survival for patients with diverse malignancies. Many of these new drugs target the human epidermal growth factor receptor (EGFR/HER/ErbB) family of tyrosine kinases, which play a major role in the etiology and progression of many carcinomas, including epithelial ovarian cancer. While several HER-targeted therapeutics are US FDA approved for the treatment of various malignancies, none have gained approval for the treatment of ovarian cancer. Here, we review the published literature on HER-targeted therapeutics for the treatment of ovarian cancer, including novel HER-targeted therapeutics in various stages of clinical development, as well as the challenges that have limited the use of these inhibitors in clinical settings.

3D/4D functional imaging of tumor-associated proteolysis: impact of microenvironment

Proteases play causal roles in many aspects of the aggressive phenotype of tumors, yet many of the implicated proteases originate from tumor-associated cells or from responses of tumor cells to interactions with other cells. Therefore, to obtain a comprehensive view of tumor proteases, we need to be able to assess proteolysis in tumors that are interacting with their microenvironment. As this is difficult to do in vivo, we have developed functional live-cell optical imaging assays and 3D and 4D (i.e., 3D over time) coculture models. We present here a description of the probes used to measure proteolysis and protease activities, the methods used for imaging and analysis of proteolysis and the 3D and 4D models used in our laboratory. Of course, all assays have limitations; however, we suggest that the techniques discussed here will, with attention to their limitations, be useful as a screen for drugs to target the invasive phenotype of tumors.

Diverse mechanisms for activation of Wnt signalling in the ovarian tumour microenvironment

Wnt signalling pathways have been shown to play key roles in both normal development and tumorigenesis. Progression of many human cancers is associated with defined mutations in Wnt pathway components that result in dysregulated β-catenin-mediated gene transcription. Although Wnt pathway mutations are rare in epithelial ovarian cancer (with the exception of the endometrioid histotype), accumulating evidence supports a role for Wnt signalling in ovarian tumorigenesis in the absence of genetic mutations. The present review summarizes evidence in support of activated Wnt signalling in ovarian tumours and discusses alternative mechanisms for Wnt pathway activation in the ovarian tumour microenvironment.

Role of DDR1 in the gelatinases secretion induced by native type IV collagen in MDA-MB-231 breast cancer cells

Discoidin domain receptors (DDRs) are receptor tyrosine kinases that get activated by collagens in its native triple-helical form. In mammalian cells, DDR family consists of two members, namely DDR1 and DDR2, which mediates migration and proliferation of several cell types. DDR1 is activated by native type IV collagen and overexpressed in human breast cancer. Type IV collagen is the main component of basement membrane (BM), and the ability to degrade and penetrate BM is related with an increased potential for invasion and metastasis. Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that collectively are capable of degrading all components of the extracellular matrix, including the BM. In breast cancer cells, denatured type IV collagen induces MMP-9 secretion and invasion. However, the role of DDR1 in the regulation of gelatinases (MMP-2 and -9) secretion and invasion in breast cancer cells remains to be studied. We demonstrate here that native type IV collagen induces MMP-2 and -9 secretions and invasion through a DDR1 and Src-dependent pathway, together with an increase of MMP-2 and -9-cell surface levels. MMP-2 and -9 secretions require PKC kinase activity, epidermal growth factor receptor (EGFR) activation, arachidonic acid (AA) production and AA metabolites in MDA-MB-231 breast cancer cells. In summary, our data demonstrate, for the first time, that DDR1 mediates MMP-2 and -9 secretions and invasion induced by native type IV collagen in MDA-MB-231 breast cancer cells.

Oleic acid promotes MMP-9 secretion and invasion in breast cancer cells

Epidemiological and animal studies suggest an association between dietary fatty acids and an increase risk of developing breast cancer. Obesity, which is characterized by hyperlipidemia and an elevation of circulating free fatty acids (FFAs), is also associated with enhanced cancer risk. In breast cancer cells, the FFA oleic acid (OA) induces migration, proliferation, prolong survival, invasion, an increase in cellular Ca(2+) concentration, MEK1/2, ERK1/2, FAK and Src activation. However, the role of OA on MMP-9 secretion and invasion has not been studied in detail. We demonstrate here that stimulation of MDA-MB-231 breast cancer cells with 200 μM OA induces an increase on MMP-9 secretion through a PKC, Src, and EGFR-dependent pathway, as revealed by gelatin zymography assays. Furthermore, microtubule network mediates MMP-9 secretion induced by OA. In contrast, OA does not induce an increase on MMP-9 secretion in MCF10A cells, whereas it does not induce MMP-9 secretion in MCF12A mammary non-tumorigenic epithelial cells. In addition, OA induces invasion through an EGFR, Gi/Go proteins, MMPs, PKC and Src-dependent pathway, but it is not able to promote invasion in non-invasive MCF-7 breast cancer cells. In summary, our findings demonstrate that OA promotes an increase on MMP-9 secretion and invasion through a PKC, Src, and EGFR-dependent pathway in breast cancer cells.

The epidermal growth factor receptor responsive miR-125a represses mesenchymal morphology in ovarian cancer cells

The epithelial-to-mesenchymal transition (EMT) that occurs during embryonic development is recapitulated during tumor metastasis. Important regulators of this process include growth factors, transcription factors, and adhesion molecules. New evidence suggests that microRNA (miRNA) activity contributes to metastatic progression and EMT; however, the mechanisms leading to altered miRNA expression during cancer progression remain poorly understood. Importantly, overexpression of the epidermal growth factor receptor (EGFR) in ovarian cancer correlates with poor disease outcome and induces EMT in ovarian cancer cells. We report that EGFR signaling leads to transcriptional repression of the miRNA miR-125a through the ETS family transcription factor PEA3. Overexpression of miR-125a induces conversion of highly invasive ovarian cancer cells from a mesenchymal to an epithelial morphology, suggesting miR-125a is a negative regulator of EMT. We identify AT-rich interactive domain 3B (ARID3B) as a target of miR-125a and demonstrate that ARID3B is overexpressed in human ovarian cancer. Repression of miR-125a through growth factor signaling represents a novel mechanism for regulating ovarian cancer invasive behavior.

EGF-receptor regulation of matrix metalloproteinases in epithelial ovarian carcinoma

Ovarian carcinoma is most frequently detected when disease has already disseminated intra-abdominally, resulting in a 5-year survival rate of less than 20% owing to complications of metastasis. Peritoneal ascites is often present, establishing a unique microenvironmental niche comprised of tumor and inflammatory cells, along with a wide range of bioactive soluble factors, several of which stimulate the EGF-receptor (EGFR). Elevated EGFR is associated with less favorable disease outcome in ovarian cancer, related in part to EGFR activation of signaling cascades that lead to enhanced matrix metalloproteinase expression and/or function. The available data suggest that modulating the expression or activity of the EGFR and/or matrix metalloproteinases offers opportunity for targeted intervention in patients with metastatic disease.

EGF-induced MMP-9 expression is mediated by the JAK3/ERK pathway, but not by the JAK3/STAT-3 pathway in a SKBR3 breast cancer cell line

The number of epidermal growth factor receptors (EGFRs) and their ligands are highly expressed in malignant tumor cells. The EGF signaling pathway is also activated in up to one-third of patients with breast cancer. In this study, we investigated the novel function of the JAK3 inhibitor, WHI-P131, on EGF-induced MMP-9 expression and the regulatory mechanism of EGF-induced MMP-9 expression in SKBR3 cells. We observed that EGF increased MMP-9 mRNA and protein expression in a dose-dependent manner. EGF also induced the phosphorylation of EGFR, ERK, and STAT-3, and these effects were inhibited by the EGFR inhibitor, AG1478.To investigate the involvement of the STAT-3 pathway on EGF-induced MMP-9 expression, we pretreatedSKBR3 cells with JAK1, JAK2, and JAK3 inhibitors prior to EGF treatment. The results showed that the JAK3 inhibitor, WHI-P131, as well as JAK3 siRNA transfection, but not the JAK1 and JAK2 inhibitors, significantly decreased EGF-induced MMP-9 expression. In addition, EGF-induced STAT-3 phosphorylation was only inhibited by WHI-P131. We then transfected cells with adenoviral STAT-3 (Ad-STAT-3), followed by treatment with EGF. Interestingly, EGF-induced MMP-9 expression was decreased by Ad-STAT-3 overexpression in a dose-dependent manner, while it was significantly increased by STAT-3 siRNA transfection. Our results also showed that basal levels of MMP-9 expression were significantly increased by constitutive active-MEK (CAMEK)overexpression. EGF-induced ERK phosphorylation was prevented by WHI-P131, but not by JAK1 andJAK2 inhibitors. On the other hand, EGF-induced MMP-9 expression was decreased by the MEK1/2 inhibitor,UO126. Therefore, for the first time, we suggest that the JAK3 inhibitor, WHI-P131, inhibits EGF-induced STAT-3 phosphorylation as well as ERK phosphorylation. The JAK3/ERK pathway may play an important role in EGFinduced MMP-9 expression in SKBR3 cells.

Epidermal growth factor receptor-mediated membrane type 1 matrix metalloproteinase endocytosis regulates the transition between invasive versus expansive growth of ovarian carcinoma cells in three-dimensional collagen

The epidermal growth factor receptor (EGFR) is overexpressed in ovarian carcinomas and promotes cellular responses that contribute to ovarian cancer pathobiology. In addition to modulation of mitogenic and motogenic behavior, emerging data identify EGFR activation as a novel mechanism for rapid modification of the cell surface proteome. The transmembrane collagenase membrane type 1 matrix metalloproteinase (MT1-MMP, MMP-14) is a major contributor to pericelluar proteolysis in the ovarian carcinoma microenvironment and is subjected to extensive posttranslational regulation. In the present study, the contribution of EGFR activation to control of MT1-MMP cell surface dynamics was investigated. Unstimulated ovarian cancer cells display caveolar colocalization of EGFR and MT1-MMP, whereas EGFR activation prompts internalization via distinct endocytic pathways. EGF treatment results in phosphorylation of the MT1-MMP cytoplasmic tail, and cells expressing a tyrosine mutated form of MT1-MMP (MT1-MMP-Y(573)F) exhibit defective MT1-MMP internalization. As a result of sustained cell surface MT1-MMP activity, a phenotypic epithelial-mesenchymal transition is observed, characterized by enhanced migration and collagen invasion, whereas growth within three-dimensional collagen gels is inhibited. These data support an EGFR-dependent mechanism for regulation of the transition between invasive and expansive growth of ovarian carcinoma cells via modulation of MT1-MMP cell surface dynamics.

Matrix metalloproteinase 9 is a mediator of epidermal growth factor-dependent e-cadherin loss in ovarian carcinoma cells

Epidermal growth factor (EGF) receptor (EGFR) is frequently elevated in epithelial ovarian cancer, and E-cadherin expression is often reduced in advanced disease. In this study, we investigated a mechanism by which EGFR activation promotes disruption of adherens junctions through induction of matrix metalloproteinase 9 (MMP-9). We show that EGFR activation down-modulates E-cadherin, and broad spectrum MMP inhibition ameliorates EGF-stimulated junctional disruption and loss of E-cadherin protein. MMP-9 involvement in EGF-dependent down-regulation of E-cadherin was determined by siRNA specifically directed against MMP-9. Furthermore, treatment with recombinant MMP-9 or transient expression of MMP-9 is sufficient to reduce E-cadherin levels in differentiated ovarian tumor cells. Stable overexpression of MMP-9 led to a loss of E-cadherin and junctional integrity, and promoted a migratory and invasive phenotype. Thus, elevated MMP-9 protein expression is sufficient for junctional disruption and loss of E-cadherin in these cells. The associations between EGFR activation, MMP-9 expression, and E-cadherin were investigated in human ovarian tumors and paired peritoneal metastases wherein immunohistochemical staining for activated (phospho) EGFR and MMP-9 colocalized with regions of reduced E-cadherin. These data suggest that regulation of MMP-9 by EGFR may represent a novel mechanism for down-modulation of E-cadherin in ovarian cancer.

Epidermal growth factor-induced enhancement of glioblastoma cell migration in 3D arises from an intrinsic increase in speed but an extrinsic matrix- and proteolysis-dependent increase in persistence

Epidermal growth factor (EGF) receptor-mediated cell migration plays a vital role in invasion of many tumor types. EGF receptor ligands increase invasiveness in vivo, but it remains unclear how consequent effects on intrinsic cell motility behavior versus effects on extrinsic matrix properties integrate to result in net increase of translational speed and/or directional persistence of migration in a 3D environment. Understanding this convolution is important for therapeutic targeting of tumor invasion, as key regulatory pathways for intrinsic versus extrinsic effects may not be coincident. Accordingly, we have undertaken a quantitative single-cell imaging study of glioblastoma cell movement in 3D matrices and on 2D substrata across a range of collagen densities with systematic variation of protease-mediated matrix degradation. In 3D, EGF induced a mild increase in cell speed and a strong increase in directional persistence, the latter depending heavily on matrix density and EGF-stimulated protease activity. In contrast, in 2D, EGF induced a similarly mild increase in speed but conversely a decrease in directional persistence (both independent of protease activity). Thus, the EGF-enhanced 3D tumor cell migration results only partially from cell-intrinsic effects, with override of cell-intrinsic persistence decrease by protease-mediated cell-extrinsic reduction of matrix steric hindrance.

Identification of pathways associated with invasive behavior by ovarian cancer cells using multidimensional protein identification technology (MudPIT)

Proteomic profiling has emerged as a useful tool for identifying tissue alterations in disease states including malignant transformation. The aim of this study was to reveal expression profiles associated with the highly motile/invasive ovarian cancer cell phenotype. Six ovarian cancer cell lines were subjected to proteomic characterization using multidimensional protein identification technology (MudPIT), and evaluated for their motile/invasive behavior, so that these parameters could be compared. Within whole cell extracts of the ovarian cancer cells, MudPIT identified proteins that mapped to 2245 unique genes. Western blot analysis for selected proteins confirmed the expression profiles revealed by MudPIT, demonstrating the fidelity of this high-throughput analysis. Unsupervised cluster analysis partitioned the cell lines in a manner that reflected their motile/invasive capacity. A comparison of protein expression profiles between cell lines of high (group 1) versus low (group 2) motile/invasive capacity revealed 300 proteins that were differentially expressed, of which 196 proteins were significantly upregulated in group 1. Protein network and KEGG pathway analysis indicated a functional interplay between proteins up-regulated in group 1 cells, with increased expression of several key members of the actin cytoskeleton, extracellular matrix (ECM) and focal adhesion pathways. These proteomic expression profiles can be utilized to distinguish highly motile, aggressive ovarian cancer cells from lesser invasive ones, and could prove to be essential in the development of more effective strategies that target pivotal cell signaling pathways used by cancer cells during local invasion and distant metastasis.

Phenotypic plasticity of neoplastic ovarian epithelium: unique cadherin profiles in tumor progression

The mesodermally derived normal ovarian surface epithelium (OSE) displays both epithelial and mesenchymal characteristics and exhibits remarkable phenotypic plasticity during post-ovulatory repair. The majority of epithelial ovarian carcinomas (EOC) are derived from the OSE and represent the most lethal of all gynecological malignancies, as most patients (approximately 70%) present at diagnosis with disseminated intra-abdominal metastasis. The predominant pattern of EOC metastasis involves pelvic dissemination rather than lymphatic or hematologic spread, distinguishing EOC from other solid tumors. Acquisition of the metastatic phenotype involves a complex series of interrelated cellular events leading to dissociation (shedding) and dispersal of malignant cells. A key event in this process is disruption of cell-cell contacts via modulation of intercellular junctional components. In contrast to most carcinomas that downregulate E-cadherin expression during tumor progression, a unique feature of primary well-differentiated ovarian cancers is a gain of epithelial features, characterized by an increase in expression of E-cadherin. Subsequent reacquisition of mesenchymal features is observed in more advanced tumors with concomitant loss of E-cadherin expression and/or function during progression to metastasis. The functional consequences of this remarkable phenotypic plasticity are not fully understood, but may play a role in modulation of cell survival in suspension (ascites), chemoresistance, and intraperitoneal anchoring of metastatic lesions.

Synthesis of water soluble bis-triazenoquinazolines: an unusual predicted mode of binding to the epidermal growth factor receptor tyrosine kinase

A novel type of 3,3-disubstituted bis-triazenes containing an ethylaminoethyl linker flanked by two identical anilinoquinazoline ring was synthesized. These model molecules contained an N-ethylaminomorpholine moiety designed to enhance water solubility. Despite their significant bulkiness, they blocked epidermal growth factor receptor (EGFR) tyrosine kinase in a dose-dependent manner with IC(50) values in low micromolar range. Molecular modeling to predict the interactions of the molecule with the ATP binding site of EGFR suggests that the N-ethylaminomorpholine side chain plays a binding role.

Curcumin attenuates EGF-induced AQP3 up-regulation and cell migration in human ovarian cancer cells

OBJECTIVE

Aquaporin (AQP) water channels are expressed in high-grade tumor cells of different tissue origins. Based on the involvement of AQPs in angiogenesis and cell migration as well as our previous studies which show that AQP3 is involved in human skin fibroblasts cell migration, in this study, we investigated whether AQP3 is expressed in cultured human ovarian cancer cell line CaOV3 cells, and whether AQP3 expression in these cells enhances cell migration and metastatic potential.

METHODS

Cultured CaOV3 cells were treated with EGF and/or various reagents and subjected to cell migration assay by phagokinetic track mobility assay or biochemical analysis for expression or activation of proteins by SDS-PAGE/Western blot analysis.

RESULTS

In this study, we demonstrate that AQP3 is expressed in CaOV3 cells. EGF induces CaOV3 migration and up-regulates AQP3 expression. EGF-induced cell migration is inhibited by specific AQP3 siRNA knockdown or AQP3 water transport inhibitor CuSO4 and NiCl2. We also find that curcumin, a well known anti-ovarian cancer drug, down-regulates AQP3 expression and reduces cell migration in CaOV3, and the effects of curcumin are mediated, at least in part, by its inhibitory effects on EGFR and downstream AKT/ERK activation.

CONCLUSIONS

Collectively, our results provide evidence for AQP3-facilitated ovarian cancer cell migration, suggesting a novel function for AQP3 expression in high-grade tumors. The results that curcumin inhibits EGF-induced up-regulation of AQP3 and cell migration, provide a new explanation for the anticancer potential of curcumin.

PEA3 is necessary for optimal epidermal growth factor receptor-stimulated matrix metalloproteinase expression and invasion of ovarian tumor cells

Elevated expression of the epidermal growth factor (EGF) receptor (EGFR) is detected in human ovarian tumors and is associated with decreased recurrence-free and overall survival. EGFR activation affects tumor progression in part by promoting tumor invasion through the induction of prometastatic matrix metalloproteinases (MMP). PEA3, an ETS family transcription factor, is elevated in advanced and metastatic ovarian cancer and regulates MMPs in various cell types, therefore, we investigated whether PEA3 is required for the EGFR-dependent induction of MMP mRNA. MMP-9 and MMP-14 mRNA levels were selectively increased in response to EGFR activity in ovarian tumor cells. EGFR activation resulted in nuclear accumulation of PEA3 and direct binding of PEA3, but not the related protein ETS-1, to the endogenous MMP-9 and MMP-14 promoters. Furthermore, PEA3 overexpression was sufficient to induce MMP-9 and MMP-14 mRNA, tumor cell migration, and invasion, suggesting that PEA3 is an important contributor to the metastatic phenotype. Additionally, inhibition of PEA3 expression via short interfering RNA reduced the EGF induction of MMP-9 and MMP-14 gene expression by 92% and 50%, respectively, and impaired EGF-stimulated tumor cell invasion. These results suggest that PEA3 is regulated by EGFR and that the elevated PEA3 expression detected in human ovarian cancer may divert cells to a more invasive phenotype by regulating MMP-9 and MMP-14.

Mesenchymal transformation in epithelial ovarian tumor cells expressing epidermal growth factor receptor variant III

Overexpression of the epidermal growth factor (EGF) receptor occurs frequently in ovarian cancer and is associated with poor patient prognosis. A constitutively active mutant EGF receptor termed variant III (EGFRvIII) has been detected at a high frequency in many human tumors, including those of the ovary. To identify the consequences of EGFRvIII expression in ovarian tumor cells, we introduced EGFRvIII into the epithelial ovarian cancer cell line (OVCA 433). The EGFRvIII-transfected cells displayed a dissociated, motile phenotype and fibroblastic morphology. The EGFRvIII-dependent phenotype was comparable to that observed in EGF-stimulated parental OVCA 433 cultures and required the catalytic activity of the mutant receptor. Disruption of adherens and desmosomal junctions in EGFRvIII expressing cells was evident by immunofluorescent detection of specific junctional components. In addition, Western blot analysis confirmed decreased levels of cellular plakoglobin and beta-catenin in EGFRvIII-expressing cells, and E-cadherin protein and mRNA were nearly absent. The loss of E-cadherin was accompanied by decreased expression of additional ovarian epithelial markers, including keratins 7, 8, and 18 and mucins 1 and 4. In contrast, the mesenchymal markers N-cadherin and vimentin were elevated in EGFRvIII expressing cells. Overall, the switch in cadherins from E-cadherin to N-cadherin, coupled with gain of vimentin expression and loss of the epithelial keratins and mucins typically expressed in well-differentiated epithelial ovarian carcinomas, are consistent with transition to a mesenchymal phenotype as an outcome of EGFRvIII expression. These findings suggest that EGFRvIII expression may regulate phenotypic plasticity in ovarian cancer and thereby contribute to more aggressive disease.

Inhibition of Matrilysin Expression by Antisense or RNA Interference Decreases Lysophosphatidic Acid–Induced Epithelial Ovarian Cancer Invasion

Our previous reports show that matrilysin [matrix metalloproteinase (MMP)-7] is overexpressed in epithelial ovarian cancer (EOC) and recombinant MMP-7 promotes EOC invasion in vitro. In the present study, we further evaluated the correlation of MMP-7 expression to EOC invasiveness and examined its role in lysophosphatidic acid (LPA)-induced invasion. By sense and antisense gene transfection in vitro, we show that overexpression of MMP-7 in all MMP-7 stably transfected DOV13 clones significantly enhanced their invasiveness, although MMP-7 antisense transfection caused a 91% decrease of MMP-7 expression (P < 0.01) and 87% decrease of invasion (P < 0.05) in geneticin (G418)-selected DOV13 clone P47-M7As-3 compared with vector-transfected control. As assessed by MMP-7 ELISA, LPA treatment at 10 to 80 micromol/L significantly stimulated the secretion of total MMP-7 in DOV13 conditioned medium (P < 0.01). In addition, LPA apparently induced the activation of MMP-7 in DOV13 cells as detected by gelatin zymography. In the antisense MMP-7-transfected DOV13 clone (P47-M7As-3), LPA-increased invasion was significantly decreased compared with vector control. Moreover, knocking down of MMP-7 by small interfering RNA also suppressed LPA-induced invasion in two EOC cell lines (DOV13 and R182). Altogether, our results show that MMP-7 expression is correlated with EOC invasiveness and LPA-induced MMP-7 secretion/activation may represent a new mechanism that facilitates ovarian cancer invasion besides the well-known induction of MT1-MMP-mediated proMMP-2 activation by LPA.

Inhibition of matrix degrading enzymes and invasion in human glioblastoma (U87MG) cells by isoflavones

Glioblastoma multiforme is a primary brain tumor associated with extensive invasion into surrounding brain tissue. Matrix metalloproteinases (MMPs) and urokinase plasminogen activation (uPA) system are shown to be involved in tumor invasion as they help in degradation of extracellular matrix (ECM) proteins and thus assist in the movement of cells. MMP-2 and 9 were shown to be upregulated in gliomas, suggesting their involvement in invasion. Genistein and biochanin A are isoflavones commonly known as phytoestrogens and have some anticancer properties. We hypothesize that these two isoflavones can induce a lowering of tumor invasion by decreasing the activity of matrix degrading enzymes. In this study we investigated the effects of genistein and biochanin A on invasive activity of U87MG cells using the Calbiochem in vitro invasion assay system. Our results suggest that genistein and biochanin A induced a decrease in invasive activity of U87MG cells in a dose-related manner. Genistein also induced a decrease in EGF-stimulated invasion thereby implicating an involvement of EGF-mediated signaling in invasion. Our results also show that treatment of U87MG cells with the two isoflavones induced decreases in the enzymatic activity of MMP-9 and the protein levels of MT1-MMP and uPAR.

Functional relevance of urinary-type plasminogen activator receptor-alpha3beta1 integrin association in proteinase regulatory pathways

Squamous cell carcinoma of the oral cavity is characterized by persistent, disorganized expression of integrin alpha3beta1 and enhanced production of urinary-type plasminogen activator (uPA) and its receptor (uPAR) relative to normal oral mucosa. Because multivalent aggregation of alpha3beta1 integrin up-regulates uPA and induces a dramatic co-clustering of uPAR, we explored the hypothesis that lateral ligation of alpha3beta1 integrin by uPAR contributes to uPA regulation in oral mucosal cells. To investigate mechanisms by which uPAR/alpha3beta1 binding enhances uPA expression, integrin-dependent signal activation was assessed. Both Src and ERK1/2 were phosphorylated in response to integrin aggregation, and blocking Src kinase activity completely abrogated ERK1/2 activation and uPA induction, whereas inhibition of epidermal growth factor receptor tyrosine kinase activity did not alter uPA expression. Proteinase up-regulation occurred at the transcriptional level and mutation of the AP1 (-1967) site in the uPA promoter blocked the uPAR/integrin-mediated transcriptional activation. Because uPAR is redistributed to clustered alpha3beta1 integrins, the requirement for uPAR/alpha3beta1 interaction in uPA regulation was assessed. Clustering of alpha3beta1 in the presence of a peptide (alpha325) that disrupts uPAR/alpha3beta1 integrin binding prevented uPA induction. Depletion of cell surface uPAR using small interfering RNA also blocked uPA induction following integrin alpha3beta1 clustering. These results were confirmed using a genetic strategy in which alpha3 null epithelial cells reconstituted with wild type alpha3 integrin, but not a mutant alpha3 unable to bind uPAR, induced uPA expression upon integrin clustering, confirming the critical role of uPAR in integrin-regulated proteinase expression. Disruption of uPAR/alpha3beta1 binding using peptide alpha325 or small interfering RNA blocked filopodia formation and matrix invasion, indicating that this interaction stimulates invasive behavior. Together these data support a model wherein matrix-induced clustering ofalpha3beta1 integrin promotes uPAR/alpha3beta1 interaction, thereby potentiating cellular signal transduction pathways culminating in activation of uPA expression and enhanced uPA-dependent invasive behavior.

Epidermal growth factor promotes invasiveness of pancreatic cancer cells through NF-kappaB-mediated proteinase productions

OBJECTIVES

Overexpression of epidermal growth factor (EGF) and EGF receptor has been associated with progression and invasive phenotype in pancreatic cancer. However, the underlying molecular mechanism by which EGF worked in pancreatic cancer cells has been poorly understood. In this study, we determined the effect of EGF on the invasiveness and the related regulatory mechanism in two pancreatic cancer cell lines NOR-P1 and KP4.

METHODS

Invasion assay was performed to examine the invasiveness of tumor cells induced by EGF, and the expression of matrix metalloproteinase (MMP)-9, MMP-2, and plasminogen activator (uPA) was determined by reverse transcription-polymerase chain reaction and Western blot. Gelatin zymography was used to detect the activities of MMP-9 and MMP-2, and the nuclear factor-kappaB (NF-kappaB) binding activity was determined by electrophoretic mobility shift assay (EMSA).

RESULTS

EGF significantly increased the invasiveness of both cell lines but did not affect cell proliferation or adhesion. Increased invasiveness was associated with the induction of MMP-9 and uPA at both mRNA and protein levels. Furthermore, EGF stimulated NF-kappaB binding activity. Moreover, pretreatment of cells with NF-kappaB inhibitors, pyrrolidine dithiocarbamate or ibuprofen, markedly attenuated EGF-induced NF-kappaB activation. Subsequently, the EGF-induced MMP-9 and uPA expression and MMP-9 activity, as well as cell invasiveness, were also inhibited by these NF-kappaB inhibitors.

CONCLUSIONS

Our findings indicated that NF-kappaB-mediated MMP-9 and uPA induction was responsible for EGF-induced invasiveness in these pancreatic cancer cell lines and implicate that such anti-NF-kappaB therapy as the use of NF-kappaB inhibitors may contribute to the reduction of invasiveness of pancreatic cancer.

Down-regulation of Integrin α2Surface Expression by Mutant Epidermal Growth Factor Receptor (EGFRvIII) Induces Aberrant Cell Spreading and Focal Adhesion Formation

Elevated expression or activity of the epidermal growth factor receptor (EGFR) is common in ovarian cancer and is associated with poor patient prognosis. A naturally occurring EGFR mutation termed variant III (EGFRvIII) has been detected in many human tumors, including those of the ovary. This mutant receptor does not bind EGF; however, it is constitutively active as detected by receptor dimerization, autophosphorylation, and stimulation of signal transduction cascades. To identify the consequences of EGFRvIII expression in ovarian tumor cells, we introduced EGFRvIII into the epithelial ovarian cancer cell line OVCA 433. The EGFRvIII-transfected cells displayed a motile phenotype, defects in cell spreading, and decreased integrin alpha2 protein expression as detected by Western blot analysis and flow cytometry. Inhibition of EGFRvIII catalytic activity using the EGFR-selective tyrphostin AG1478 restored integrin alpha2 expression within 4 to 8 hours after treatment. The modulation of integrin alpha2 expression corresponded to marked changes in the actin cytoskeleton as detected by redistribution of filamentous-actin. Furthermore, focal adhesions were evident only when EGFRvIII activity was inhibited. Together, these findings suggest that expression of the constitutively active mutant EGFRvIII promotes changes in cell shape and focal adhesion formation, mediated in part through specific modulation of integrin alpha2 expression and function. We conclude that EGFR-activating mutations, such as EGFRvIII, in ovarian cancer may contribute to a more aggressive disease.

Proteolytic-antiproteolytic balance and its regulation in carcinogenesis

Cancer development is essentially a tissue remodeling process in which normal tissue is substituted with cancer tissue. A crucial role in this process is attributed to proteolytic degradation of the extracellular matrix (ECM). Degradation of ECM is initiated by proteases, secreted by different cell types, participating in tumor cell invasion and increased expression or activity of every known class of proteases (metallo-, serine-, aspartyl-, and cysteine) has been linked to malignancy and invasion of tumor cells. Proteolytic enzymes can act directly by degrading ECM or indirectly by activating other proteases, which then degrade the ECM. They act in a determined order, resulting from the order of their activation. When proteases exert their action on other proteases, the end result is a cascade leading to proteolysis. Presumable order of events in this complicated cascade is that aspartyl protease (cathepsin D) activates cysteine proteases (e.g., cathepsin B) that can activate pro-uPA. Then active uPA can convert plasminogen into plasmin. Cathepsin B as well as plasmin are capable of degrading several components of tumor stroma and may activate zymogens of matrix metalloproteinases, the main family of ECM degrading proteases. The activities of these proteases are regulated by a complex array of activators, inhibitors and cellular receptors. In physiological conditions the balance exists between proteases and their inhibitors. Proteolytic-antiproteolytic balance may be of major significance in the cancer development. One of the reasons for such a situation is enhanced generation of free radicals observed in many pathological states. Free radicals react with main cellular components like proteins and lipids and in this way modify proteolytic-antiproteolytic balance and enable penetration damaging cellular membrane. All these lead to enhancement of proteolysis and destruction of ECM proteins and in consequence to invasion and metastasis.

Engineered growth factors and cutaneous wound healing: Success and possible questions in the past 10 years

In the past 10 years, many engineered growth factors, including recombinant human epidermal growth factor, basic fibroblast growth factor, and platelet-derived growth factor, have been produced and used in the clinic. After screening the results from different centers, some results are found to be encouraging, while others are discouraging. Although the interpretation of these results may depend on your perspective, it may also depend on different criteria, different wounds, and even different aims. In this article, successful experiences and failures concerning the use of growth factors and cutaneous wound healing are summarized. Based on this information and our clinical experience, we address people's concerns such as whether growth factors have altered clinical practice thus far and whether growth factor treatments have solved all problems involved in wound healing. Is there a need for exogenous application of growth factors in acute or chronic wounds, and if so, is it safe to use growth factors to promote wound healing? Last, can we achieve perfect wound healing in those wounds treated with growth factors?

Matrilysin (MMP-7) promotes invasion of ovarian cancer cells by activation of progelatinase

Although matrilysin (MMP-7) is overexpressed in various malignancies, few studies have evaluated its role in epithelial ovarian cancer (EOC) invasion and metastasis. We report that the secretion of MMP-7 in EOC is stimulated significantly by vascular endothelial growth factor (VEGF) and interlukin-8 (IL-8). We also examined the in vivo expression of MMP-7 in EOC and its effects on the in vitro invasion and progelatinase activation. We report that MMP-7 is overexpressed in ovarian cancer cell lines and EOC surgical specimens. DOV13 cells incubated with active rhMMP-7 significantly increased cellular invasion and proMMP-2 activation. RhMMP-7 also showed the ability to activate proMMP-2 and proMMP-9 in immortalized ovarian epithelial cell (IOSE-29) conditioned medium. In addition, rhMMP-7 was able to activate progelatinase in a concentration-dependent manner in vitro. TIMP-2 or the generic MMP inhibitor-GM6001 inhibited both the activation of proMMP-2 and the increased invasion of DOV13 cells promoted by rhMMP-7. By incubation of MMP2-TIMP-2 complex with equal molar rhMMP-7, MMP-2 was dissociated from the complex and activated in a time-dependent manner, suggesting that TIMP-2 helps to keep the latency of MMP-2. TIMP-2 also showed inhibitory effects on the MMP-7 induced increase of gelatinolytic activity in DOV13 and IOSE-29 conditioned media. A strong co-localization of MMP-7 and MMP-2 was observed in DOV13 cells and ovarian carcinoma permanent tissue sections. These results indicate MMP-7 is overexpressed in malignant ovarian epithelium and suggest MMP-7 may facilitate tumor cell invasion in vivo partly through the induction of progelatinase activation.

Id-I stimulates cell proliferation through activation of EGFR in ovarian cancer cells

Increased EGFR (epidermal growth factor receptor) expression has been reported in many types of human cancer and its levels are positively associated with advanced cancers. Recently, upregulation of Id-1 (inhibitor of differentiation or DNA binding) protein was found in over 70% of ovarian cancer samples and correlated with poor survival of ovarian cancer patients. However, the molecular mechanisms responsible for the role of Id-1 in ovarian cancer are not clear. The aim of this study was to investigate the effect of Id-1 on ovarian cancer proliferation and its association with the EGFR pathway. To achieve this, we transfected an Id-1 expression vector into three ovarian cancer cell lines and examined cell proliferation rate by flow cytometry and bromodeoxyuridine staining. We found that ectopic Id-1 expression led to increased cell proliferation demonstrated by increased BrdU incorporation rate and S-phase fraction. The Id-1-induced cell growth was associated with upregulation of EGFR at both transcriptional and protein levels. In contrast, inactivation of Id-1 through transfection of an Id-1 antisense vector resulted in downregulation of EGFR. Our results indicate that increased Id-1 in ovarian cancer cells may promote cancer cell proliferation through upregulation of EGFR. Our findings also implicate that Id-1 may be a potential target for the development of novel strategies in the treatment of ovarian cancer.

Proinvasive Properties of Ovarian Cancer Ascites-Derived Membrane Vesicles

Malignant ovarian ascites are rich in cellular components, membrane-bound vesicles, and soluble proteins. This study focused on the structure of membrane-bound vesicles and their ability to promote invasion in cultured malignant ovarian epithelium. Membrane vesicles were derived from women with stage I-IV malignant ovarian ascites and from nonmalignant gynecologic ascites. Isolated vesicles were characterized by immunofluorescence and Western blot analysis. Using gel zymography for matrix metalloproteinase (MMP) detection and a colorimetric assay for urokinase-type plasminogen activator (uPA) analysis, we analyzed the proteinase activities of MMP-2, MMP-9, and uPA from the prepared vesicles, whole cells isolated from ascites, and the cell-free ultracentrifuged supernatant. The invasiveness of established cultured malignant ovarian epithelium on addition of ascites-derived vesicles was tested using a Matrigel-based invasion assay. Fractionation of malignant ascites revealed that extracellular matrix-degrading proteinases including MMPs and uPA are localized preferentially in membrane vesicles. All malignant vesicles tested, regardless of cancer stage, stimulated invasion. Furthermore, the combination of ovarian cancer cells and membrane vesicles resulted in greater uPA activation than that of cells or vesicles alone. Membrane vesicles from malignant ascites were also found to contain activated MMP-2, MMP-9, and uPA. Our data suggest that vesicle-stimulated proteinase activation leads to increased extracellular matrix degradation, which may facilitate tumor cell invasion and metastasis.

Epidermal growth factor receptor inhibition promotes desmosome assembly and strengthens intercellular adhesion in squamous cell carcinoma cells

The epidermal growth factor receptor (EGFR) has been proposed as a key modulator of cadherin-containing intercellular junctions, particularly in tumors that overexpress this tyrosine kinase. Here the EGFR tyrosine kinase inhibitor PKI166 and EGFR blocking antibody C225, both of which are used clinically to treat head and neck cancers, were used to determine the effects of EGFR inhibition on intercellular junction assembly and adhesion in oral squamous cell carcinoma cells. EGFR inhibition resulted in a transition from a fibroblastic morphology to a more epithelial phenotype in cells grown in low calcium; under these conditions cadherin-mediated cell-cell adhesion is normally reduced, and desmosomes are absent. The accumulated levels of desmoglein 2 (Dsg2) and desmocollin 2 increased 1.7-2.0-fold, and both desmosomal cadherin and plaque components were recruited to cell-cell borders. This redistribution was paralleled by an increase in Dsg2 and desmoplakin in the Triton-insoluble cell fraction, suggesting that EGFR blockade promotes desmosome assembly. Importantly, E-cadherin expression and solubility were unchanged. Furthermore, PKI166 blocked tyrosine phosphorylation of Dsg2 and plakoglobin following epidermal growth factor stimulation, whereas no change in phosphorylation was detected for E-cadherin and beta-catenin. The increase in Dsg2 protein was in part due to the inhibition of matrix metalloproteinase-dependent proteolysis of this desmosomal cadherin. These morphological and biochemical changes were accompanied by an increase in intercellular adhesion based on functional assays at all calcium concentrations tested. Our results suggest that EGFR inhibition promotes desmosome assembly in oral squamous cell carcinoma cells, resulting in increased cell-cell adhesion.

Lessons from border cell migration in the Drosophila ovary: A role for myosin VI in dissemination of human ovarian cancer

Dissemination of ovarian cancer is a major clinical challenge and is poorly understood at the molecular level due to a lack of suitable experimental models. During normal development of the Drosophila ovary, a dynamic process called border cell migration occurs that resembles the migratory behavior of human ovarian cancer cells. In this study, we found that myosin VI, a motor protein that regulates border cell migration, is abundantly expressed in high-grade ovarian carcinomas but not in normal ovary and ovarian cancers that behave indolently. Inhibiting myosin VI expression in high-grade ovarian carcinoma cells impeded cell spreading and migration in vitro. Optical imaging and histopathologic studies revealed that inhibiting myosin VI expression reduces tumor dissemination in nude mice. Therefore, using genetic analysis of border cell migration in Drosophila is a powerful approach to identify novel molecules that promote ovarian cancer dissemination and represent potential therapeutic targets.

Identification of epidermal growth factor-responsive genes in normal rat ovarian surface epithelial cells

Alteration in epidermal growth factor receptor (EGFR) family signaling is among the most frequently implicated effectors of human oncogenesis. Overexpression of members of this family of receptors has often been detected in many epithelial tumors and is believed to be associated with an overall poor prognosis in patients with cancer. Therefore, we hypothesized that identification of potential EGF target genes in normal cells will provide a basis for unbiased genetic analysis of this signaling pathway in cancer. We utilized Atlas Rat 1.2 nylon cDNA arrays (Clontech) to determine gene expression changes in normal rat ovarian surface epithelial (ROSE) cells following EGF treatment. The results indicate activation of genes involved in a wide variety of cellular mechanisms, including regulation of cell cycle and proliferation, apoptosis, and protein turnover. In addition, using an in vitro model of ovarian cancer, we demonstrated that malignant transformation of ROSE cells resulted in alteration of downstream effectors of the EGFR pathway, as exemplified by aberrant expression of p66Shc, c-Jun, c-Myc, c-Fos, Lot1, p21Cip/Waf, and cdc25A. These data suggest that knowledge of the downstream genetic lesions, which may result in loss of growth factor requirement of the affected cells, will be crucial for the selection of the EGFR pathway as an effective target for cancer therapy.

Ganglioside GM3 inhibits matrix metalloproteinase-9 activation and disrupts its association with integrin

Gangliosides GM3 and GT1b both inhibit epithelial cell adhesion and migration on fibronectin. GT1b binds to integrin alpha5beta1 and blocks the integrin-fibronectin interaction; GM3 does not interact with integrin, and its effect is poorly understood. We evaluated the effects of endogenous modulation of GM3 expression on epithelial cell motility on several matrices and the mechanism of these effects. Endogenous accumulation of GM3 decreased cell migration on fibronectin, types I, IV, and VII collagen matrices; depletion of GM3 dramatically increased cell migration, regardless of matrix. GM3 overexpression and depletion in vitro correlated inversely with the expression and activity of matrix metalloproteinase-9; consistently, the cell migration stimulated by GM3 depletion is reversed by inhibition of matrix metalloproteinase-9 activity. Accumulation and depletion of GM3 in epithelial cells grown on fibronectin also correlated inversely with epidermal growth factor receptor and mitogen activated protein kinase phosphorylation and with Jun expression. Ganglioside depletion facilitated the co-immunoprecipitation of matrix metal-loproteinase-9 and integrin alpha5beta1, while endogenous accumulation of GM3, but not GT1b, blocked the co-immunoprecipitation. These data suggest modulation of epidermal growth factor receptor signaling and dissociation of integrin/matrix metalloproteinase-9 as mechanisms for the GM3-induced effects on matrix metalloproteinase-9 function.

Binding to EGF receptor of a laminin-5 EGF-like fragment liberated during MMP-dependent mammary gland involution

Extracellular matrix (ECM) fragments or cryptic sites unmasked by proteinases have been postulated to affect tissue remodeling and cancer progression. Therefore, the elucidation of their identities and functions is of great interest. Here, we show that matrix metalloproteinases (MMPs) generate a domain (DIII) from the ECM macromolecule laminin-5. Binding of a recombinant DIII fragment to epidermal growth factor receptor stimulates downstream signaling (mitogen-activated protein kinase), MMP-2 gene expression, and cell migration. Appearance of this cryptic ECM ligand in remodeling mammary gland coincides with MMP-mediated involution in wild-type mice, but not in tissue inhibitor of metalloproteinase 3 (TIMP-3)-deficient mice, supporting physiological regulation of DIII liberation. These findings indicate that ECM cues may operate via direct stimulation of receptor tyrosine kinases in tissue remodeling, and possibly cancer invasion.

Development of matrix metalloproteinase inhibitors in cancer therapy

The matrix metalloproteinases represent an attractive target for cancer treatment, and a number of matrix metalloproteinase inhibitors are undergoing clinical trials. The results of these studies will establish whether any of these compounds are therapeutically useful. Independent of the conclusions from the first generation of studies, the field of matrix metalloproteinase inhibitors remains attractive for creative and innovative research. In the future, the development of novel, less toxic, and more effective matrix metalloproteinase inhibitors, and the combination of conventional agents with these novel anticancer agents will constitute the main focus of research efforts.

Enzyme-activated targeting of liposomes

It has become increasingly evident that tissues utilize specific localization of enzymes to perform certain tasks, often associated with various types of tissue remodeling. The ubiquitous presence of such enzymes, along with their specific localizations, provides an ideal opportunity to elicit specific delivery via an enzyme-triggered mechanism. A survey of some of the recent progress in enzyme-activated targeting of delivery systems, with a focus on a few liposomal systems, is presented.

Epidermal growth factor receptor signaling and the invasive phenotype of ovarian carcinoma cells

BACKGROUND

Most (70%-100%) ovarian carcinomas express high levels of the epidermal growth factor receptor (EGFR). To examine the relationship between EGFR and the invasive phenotype, we assessed integrin expression, adhesion, matrix metalloproteinase (MMP) activity, and migration in ovarian cancer cells in which EGFR expression was modified.

METHODS

NIH:OVCAR-8 human ovarian carcinoma cells were transfected with an expression vector containing the human EGFR complementary DNA in an antisense orientation (EGFR-antisense cells) or the vector alone (vector control cells). We compared vector control and EGFR-antisense cells for cell morphology and adhesion by light microscopy, expression of alpha(6)- and alpha(3)-integrin subunits by flow cytometry, MMP and tissue inhibitor of MMP (TIMP) activity by zymography, and migration by a wound migration assay. In some experiments, EGFR kinase activity in parental cells was inhibited by treatment with PD153035. All statistical tests were two-sided.

RESULTS

EGFR-antisense cells were morphologically distinct from vector control cells and had a selective decrease in adhesion to laminin-1 that was not observed with vector control cells (P = .008) or on other extracellular matrix substrates. Compared with vector control cells, cell surface alpha(6)-integrin expression decreased by approximately 80% (difference = 78.7%; 95% confidence interval [CI] = 77.8% to 79.6), MMP-9 activity decreased by approximately 50%, and TIMP activity increased by approximately 50% in EGFR-antisense cells. Vector control cells were highly motile (5.51 arbitrary distance unit; 95% CI = 4.98 to 6.04), whereas the EGFR-antisense cells were not (0.99 arbitrary distance units; 95% CI = 0.38 to 1.60). The morphology and integrin profile of NIH:OVCAR-8 parental cells treated with PD153035 were similar to those of the EGFR-antisense cells.

CONCLUSIONS

Reduced EGFR expression in ovarian carcinoma cells decreased their adhesion to laminin-1, expression of the alpha(6)-integrin subunit (a well-characterized laminin-1 receptor), and MMP-9 activity. These data support the hypothesis that EGFR overexpression in ovarian cancer cells results in multiple phenotypic changes that enhance the invasive phenotype.