The role of hepatocyte growth factor (scatter factor) in epithelial-mesenchymal transition and breast cancer

ERK Signaling Pathway Is Constitutively Active in NT2D1 Non-Seminoma Cells and Its Inhibition Impairs Basal and HGF-Activated Cell Proliferation

c-MET/hepatocyte growth factor (HGF) system deregulation is a well-known feature of malignancy in several solid tumors, and for this reason this system and its pathway have been considered as potential targets for therapeutic purposes. In previous manuscripts we reported c-MET/HGF expression and the role in testicular germ cell tumors (TGCTs) derived cell lines. We demonstrated the key role of c-Src and phosphatidylinositol 3-kinase (PI3K)/AKT adaptors in the HGF-dependent malignant behavior of the embryonal carcinoma cell line NT2D1, finding that the inhibition of these onco-adaptor proteins abrogates HGF triggered responses such as proliferation, migration, and invasion. Expanding on these previous studies, herein we investigated the role of mitogen-activated protein kinase (MAPK)/extracellular signal regulated kinase (ERK) pathways in the HGF-dependent and HGF-independent NT2D1 cells biological responses. To inhibit MAPK/ERK pathways we chose a pharmacological approach, by using U0126 inhibitor, and we analyzed cell proliferation, collective migration, and chemotaxis. The administration of U0126 together with HGF reverts the HGF-dependent activation of cell proliferation but, surprisingly, does not exert the same effect on NT2D1 cell migration. In addition, we found that the use of U0126 alone significantly promotes the acquisition of NT2D1 «migrating phenotype», while collective migration of NT2D1 cells was stimulated. Notably, the inhibition of ERK activation in the absence of HGF stimulation resulted in the activation of the AKT-mediated pathway, and this let us speculate that the paradoxical effects obtained by using U0126, which are the increase of collective migration and the acquisition of partial epithelium-mesenchyme transition (pEMT), are the result of compensatory pathways activation. These data highlight how the specific response to pathway inhibitors, should be investigated in depth before setting up therapy.

The role of MET in chemotherapy resistance

Chemotherapy remains the mainstay of treatment in the majority of solid and haematological malignancies. Resistance to cytotoxic chemotherapy is a major clinical problem and substantial research is ongoing into potential methods of overcoming this resistance. One major target, the receptor tyrosine kinase MET, has generated increasing interest with multiple clinical trials in progress. Overexpression of MET is frequently observed in a range of different cancers and is associated with poor prognosis. Studies have shown that MET promotes resistance to targeted therapies, including those targeting EGFR, BRAF and MEK. More recently, several reports suggest that MET also contributes to cytotoxic chemotherapy resistance. Here we review the preclinical evidence of MET's role in chemotherapy resistance, the mechanisms by which this resistance is mediated and the translational relevance of MET inhibitor therapy for patients with chemotherapy resistant disease.

Hydrogen peroxide-producing NADPH oxidases and the promotion of migratory phenotypes in cancer

The cellular microenvironment plays a critical role in cancer initiation and progression. Exposure to oxidative stress, specifically hydrogen peroxide (H₂O₂), has been linked to aberrant cellular signaling through which the development of cancer may be promoted. Three members of the NADPH oxidase family (NOX4, DUOX1 and DUOX2) explicitly generate this non-radical oxidant in a wide range of tissues, often in support of the inflammatory response. This review summarizes the contributions of each H₂O₂-producing NOX to the invasive behaviors of tumors and/or the epithelial-mesenchymal transition (EMT) in cancer that plays an essential role in metastasis. Tissue localization in tumorigenesis is also highlighted, with patient-derived TCGA microarray data profiled across 31 cancer cohorts to provide a comprehensive guide to the relevance of NOX4/DUOX1/DUOX2 in cancer studies.

CXCL1 Derived from Mammary Fibroblasts Promotes Progression of Mammary Lesions to Invasive Carcinoma through CXCR2 Dependent Mechanisms

With improved screening methods, the numbers of abnormal breast lesions diagnosed in women have been increasing over time. However, it remains unclear whether these breast lesions will develop into invasive cancers. To more effectively predict the outcome of breast lesions and determine a more appropriate course of treatment, it is important to understand the underlying mechanisms that regulate progression of non-invasive lesions to invasive breast cancers. A hallmark of invasive breast cancers is the accumulation of fibroblasts. Fibroblast proliferation and activation in the mammary gland is in part regulated by the Transforming Growth Factor beta1 pathway (TGF-β). In animal models, TGF-β suppression of CCL2 and CXCL1 chemokine expression is associated with metastatic progression of mammary carcinomas. Here, we show that transgenic overexpression of the Polyoma middle T viral antigen in the mouse mammary gland of C57BL/6 mice results in slow growing non-invasive lesions that progress to invasive carcinomas in a stage dependent manner. Invasive carcinomas are associated with accumulation of fibroblasts that show decreased TGF-β expression and high levels of CXCL1, but not CCL2. Using co-transplant models, we show that decreased TGF-β signaling in fibroblasts contribute to mammary carcinoma progression through enhancement of CXCL1/CXCR2 dependent mechanisms. Using cell culture models, we show that CXCL1 mediated mammary carcinoma cell invasion through NF-κB, AKT, Stat3 and p42/44MAPK dependent mechanisms. These studies provide novel mechanistic insight into the progression of pre-invasive lesions and identify new stromal biomarkers, with important prognostic implications.

Knockdown on aPKC-ι inhibits epithelial-mesenchymal transition, migration and invasion of colorectal cancer cells through Rac1-JNK pathway

BACKGROUND

Atypical protein kinase C-ι (aPKC-ι) is an oncogenic factor, and required for the epithelial-mesenchymal transition (EMT) of different types of cancer. Our study aimed to investigate the role of aPKC-ι in the EMT, migration and invasion of colorectal cancer (CRC) cells.

METHODS

Expression of aPKC-ι was evaluated in CRC cell lines treated with TGF-β1 using qPCR and western blot. After aPKC-ι was knocked down using shRNA, migration and invasion abilities of CRC cell lines were evaluated by wound healing assay and transwell assay, respectively. Activation status of downstream signaling factors of aPKC-ι, including Rac1, JNK, STAT3 and β-catenin, was measured using western blot. Furthermore, auranofin, an aPKC-ι inhibitor, was used to treat CRC cell lines to investigate its possible inhibition on the EMT of CRC cell lines, as well as on the expression of aPKC-ι and its downstream signaling factors.

RESULTS

TGF-β1 induced the expression of aPKC-ι in CRC cells, and knockdown on aPKC-ι inhibited the TGF-β1-induced EMT, migration and invasion of CRC cells. Interestingly, Rac1 GTPase level was decreased when aPKC-ι was knocked down, and overexpression of Rac1G12V rescued the cell EMT, migration and invasion in CRC cells as inhibited by sh-aPKC-ι. Moreover, knockdown on aPKC-ι suppressed the phosphorylation of JNK and STAT3, and nuclear translocation of β-catenin. The aPKC- ι inhibitor, Auranofin, showed similar inhibitory effects as aPKC-ι knockdown.

CONCLUSION

Knockdown on aPKC-ι inhibited the EMT, migration and invasion of CRC cells through suppressing of Rac1-JNK pathway. Those findings indicate that aPKC-ι may serve as a novel therapeutic target for CRC.

LncRNA HOTAIR/miR-613/c-met axis modulated epithelial-mesenchymal transition of retinoblastoma cells

Since lncRNAs could modulate neoplastic development by modulating downstream miRNAs and genes, this study was carried out to figure out the synthetic contribution of HOTAIR, miR-613 and c-met to viability, apoptosis and proliferation of retinoblastoma cells. Totally 276 retinoblastoma tissues and tumour-adjacent tissues were collected, and human retinoblastoma cell lines (ie, Y79, HXO-Rb44, SO-Rb50 and WERI-RB1) were also gathered. Moreover, transfections of pcDNA3.1-HOTAIR, si-HOTAIR, miR-613 mimic, miR-613 inhibitor, pcDNA3.1/c-met were performed to evaluate the influence of HOTAIR, miR-613 and c-met on viability, apoptosis and epithelial-mesenchymal transition (EMT) of retinoblastoma cells. Dual-luciferase reporter gene assay was also arranged to confirm the targeted relationship between HOTAIR and miR-613, as well as between miR-613 and c-met. Consequently, up-regulated HOTAIR and down-regulated miR-613 expressions displayed associations with poor survival status of retinoblastoma patients (P < 0.05). Besides, inhibited HOTAIR and promoted miR-613 elevated E-cadherin expression, yet decreased Snail and Vimentin expressions (P < 0.05). Simultaneously, cell proliferation and cell viability were also less-motivated (P < 0.05). Nonetheless, c-met prohibited the functioning of miR-613, resulting in promoted cell proliferation and viability, along with inhibited cell apoptosis (P < 0.05). Finally, HOTAIR was verified to directly target miR-613, and c-met was the direct target gene of miR-613 (P < 0.05). In conclusion, the role of lncRNA HOTAIR/miR-613/c-met signalling axis in modulating retinoblastoma cells' viability, apoptosis and expressions of EMT-specific proteins might provide evidences for developing appropriate diagnostic and treatment strategies for retinoblastoma.

MET expression during prostate cancer progression

Tyrosine-kinase inhibitors of the hepatocyte growth factor receptor MET are under investigation for the treatment of hormone-refractory prostate cancer (HRPC) metastasis. Analysis of MET protein expression and genetic alterations might contribute to therapeutic stratification of prostate cancer patients. Our objective was to investigate MET on protein, DNA and RNA level in clinical prostate cancer at various stages of progression.

Expression of MET was analyzed in hormone-naive primary prostate cancers (N=481), lymph node (N=40) and bone (N=8) metastases, as well as HRPC (N=54) and bone metastases (N=15). MET protein expression was analyzed by immunohistochemistry (D1C2 C-terminal antibody). MET mRNA levels and MET DNA copy numbers were determined by in situ hybridization.

None of the hormone-naive primary prostate cancer or lymph node metastases demonstrated MET protein or mRNA expression. In contrast, MET protein was expressed in 12/52 (23%) evaluable HRPC resections. RNA in situ demonstrated cytoplasmic signals in 14/54 (26%) of the HRPC patients, and was associated with MET protein expression (p=0.025, χ²), in absence of MET amplification or polysomy. MET protein expression was present in 7/8 (88%) hormone-naive and 10/15 (67%) HRPC bone metastases, without association of HRPC (p=0.37; χ²), with MET polysomy in 8/13 (61%) evaluable cases.

In conclusion, MET was almost exclusively expressed in HRPC and prostate cancer bone metastasis, but was not related to MET amplification or polysomy. Evaluation of MET status could be relevant for therapeutic stratification of late stage prostate cancer.

IL-6 secreted by cancer-associated fibroblasts promotes epithelial-mesenchymal transition and metastasis of gastric cancer via JAK2/STAT3 signaling pathway

Cancer-associated fibroblasts (CAFs), as the activated fibroblasts in tumor stroma, are important modifiers of tumor progression. However, the molecular mechanisms underlying the tumor-promoting properties of CAFs in gastric cancer remain unclear. Here, we show that CAFs isolated from gastric cancer produce significant amounts of interleukin-6 (IL-6). CAFs enhances the migration and EMT of gastric cancer cells through the secretion of IL-6 that activates Janus kinase 2/signal transducers and activators of transcription (JAK2/STAT3) pathway in gastric cancer cells, while deprivation of IL-6 using a neutralizing antibody or inhibition of JAK/STAT3 pathway with specific inhibitor AG490 markedly attenuates these phenotypes in gastric cancer cells induced by CAFs. Moreover, silencing IL-6 expression in CAFs or inhibiting JAK2/STAT3 pathway in gastric cancer cells impairs tumor peritoneal metastasis induced by CAFs in vivo. Taken together, these results suggest that CAFs in the tumor microenvironment promote the progression of gastric cancer through IL-6/JAK2/STAT3 signaling, and IL-6 targeted therapy could be a complementary approach against gastric cancer by exerting their action on stromal fibroblasts.

Hepatocyte Growth Factor/C-Met Axis in Thyroid Cancer: From Diagnostic Biomarker to Therapeutic Target

The hepatocyte growth factor (HGF)/c-met axis plays a crucial role in cancer development by promoting cellular proliferation, motility, and morphogenesis, as well as angiogenesis. Different cellular distributions of both the ligand and the receptor in benign vs malignant lesions indicate this biological system as a candidate for a diagnostic biomarker of malignancy occurring in endocrine glands, such as the thyroid and pituitary. Furthermore, the HGF/c-met expression may help to identify a subset of patients eligible for potential targeted therapies with HGF/c-met inhibitors or antagonists in thyroid tumour, as well as in other malignancies. This may be relevant for iodine-refractory cancers, the treatment of which is still a major challenge. With this in mind, HGF/c-met expression in thyroid cancer tissue may be useful for prognostic and therapeutic stratification of patients.

Curcumin inhibited HGF-induced EMT and angiogenesis through regulating c-Met dependent PI3K/Akt/mTOR signaling pathways in lung cancer

The epithelial-mesenchymal transition (EMT) and angiogenesis have emerged as two pivotal events in cancer progression. Curcumin has been extensively studied in preclinical models and clinical trials of cancer prevention due to its favorable toxicity profile. However, the possible involvement of curcumin in the EMT and angiogenesis in lung cancer remains unclear. This study found that curcumin inhibited hepatocyte growth factor (HGF)-induced migration and EMT-related morphological changes in A549 and PC-9 cells. Moreover, pretreatment with curcumin blocked HGF-induced c-Met phosphorylation and downstream activation of Akt, mTOR, and S6. These effects mimicked that of c-Met inhibitor SU11274 or PI3 kinase inhibitor LY294002 or mTOR inhibitor rapamycin treatment. c-Met gene overexpression analysis further demonstrated that curcumin suppressed lung cancer cell EMT by inhibiting c-Met/Akt/mTOR signaling pathways. In human umbilical vein endothelial cells (HUVECs), we found that curcumin also significantly inhibited PI3K/Akt/mTOR signaling and induced apoptosis and reduced migration and tube formation of HGF-treated HUVEC. Finally, in the experimental mouse model, we showed that curcumin inhibited HGF-stimulated tumor growth and induced an increase in E-cadherin expression and a decrease in vimentin, CD34, and vascular endothelial growth factor (VEGF) expression. Collectively, these findings indicated that curcumin could inhibit HGF-promoted EMT and angiogenesis by targeting c-Met and blocking PI3K/Akt/mTOR pathways.

Phenotypic Transition as a Survival Strategy of Glioma

Malignant glioma is characterized by rapid proliferation, invasion into surrounding central nervous system tissues, and aberrant vascularization. There is increasing evidence that shows gliomas are more complex than previously thought, as each tumor comprises considerable intratumoral heterogeneity with mixtures of genetically and phenotypically distinct subclones. Heterogeneity within and across tumors is recognized as a critical factor that limits therapeutic progress for malignant glioma. Recent genotyping and expression profiling of gliomas has allowed for the creation of classification schemes that assign tumors to subtypes based on similarity to defined expression signatures. Also, malignant gliomas frequently shift their biological features upon recurrence and progression. The ability of glioma cells to resist adverse conditions such as hypoxia and metabolic stress is necessary for sustained tumor growth and strongly influences tumor behaviors. In general, glioma cells are in one of two phenotypic categories: higher proliferative activity with angiogenesis, or higher migratory activity with attenuated proliferative ability. Further, they switch phenotypic categories depending on the situation. To date, a multidimensional approach has been employed to clarify the mechanisms of phenotypic shift of glioma. Various molecular and signaling pathways are involved in phenotypic shifts of glioma, possibly with crosstalk between them. In this review, we discuss molecular and phenotypic heterogeneity of glioma cells and mechanisms of phenotypic shifts in regard to the glioma proliferation, angiogenesis, and invasion. A better understanding of the molecular mechanisms that underlie phenotypic shifts of glioma may provide new insights into targeted therapeutic strategies.

cMET inhibitor crizotinib impairs angiogenesis and reduces tumor burden in the C3(1)-Tag model of basal-like breast cancer

Epidemiologic studies have associated obesity with increased risk of the aggressive basal-like breast cancer (BBC) subtype. Hepatocyte growth factor (HGF) signaling through its receptor, cMET, is elevated in obesity and is a pro-tumorigenic pathway strongly associated with BBC. We previously reported that high fat diet (HFD) elevated HGF, cMET, and phospho-cMET in normal mammary gland, with accelerated tumor development, compared to low fat diet (LFD)-fed lean controls in a murine model of BBC. We also showed that weight loss resulted in a significant reversal of HFD-induced effects on latency and elevation of HGF/cMET signaling in normal mammary and cMET in normal mammary and tumors. Here, we sought to inhibit BBC tumor progression in LFD- and HFD-fed C3(1)-Tag BBC mice using a small molecule cMET inhibitor, and began crizotinib treatment (50 mg/kg body weight by oral gavage) upon identification of the first palpable tumor. We next investigated if administering crizotinib in a window prior to tumor development would inhibit or delay BBC tumorigenesis. Treatment: Crizotinib significantly reduced mean tumor burden by 27.96 and 37.29 %, and mean tumor vascularity by 35.04 and 33.52 %, in our LFD- and HFD-fed C3(1)-Tag BBC mice, respectively. Prevention: Crizotinib significantly accelerated primary tumor progression in both diet groups but had no effect on total tumor progression or total tumor burden. In sum, cMET inhibition by crizotinib limited tumor development and microvascular density in basal-like tumor-bearing mice but did not appear to be an effective preventive agent for BBC.

Curcumin mediates reversion of HGF-induced epithelial-mesenchymal transition via inhibition of c-Met expression in DU145 cells

The hepatocyte growth factor (HGF)/c-Met signaling pathway results in cancer cell scattering and invasion, and has been reported to participate in several types of cancer, including prostate and colorectal cancer. The downstream phosphorylation cascade of HGF, particularly the mitogen-activated protein kinase and phosphoinositide 3-kinase/AKT signaling pathway, regulates epithelial-mesenchymal transition (EMT). However, the mechanism by which these signaling pathways govern EMT, and whether certain kinases are able to respond to specific EMT effectors, remains to be elucidated. In the present study, an increase in the levels of vimentin, rather than co-regulation of certain EMT marker proteins, was observed in response to HGF-induced EMT in DU145 prostate cancer cells. In addition, it was observed that curcumin abrogated HGF-induced DU145 cell scattering and invasion. Furthermore, curcumin was able to effectively inhibit the HGF-induced increase in the levels of vimentin by downregulating the expression of phosphorylated c-Met, extracellular signal-regulated kinase and Snail. In conclusion, the results of the present study demonstrated that curcumin was able to reverse HGF-induced EMT, possibly by inhibiting c-Met expression in DU145 prostate cancer cells.

Cytoskeletal signaling in TGFβ-induced epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is a physiological process that plays an important role in embryonic development and wound healing and is appropriated during pathological conditions including fibrosis and cancer metastasis. EMT can be initiated by a variety of factors, including transforming growth factor (TGF)-β, and is characterized by loss of epithelial features including cell-cell contacts and apicobasal polarity and acquisition of a motile, mesenchymal phenotype. A key feature of EMT is reorganization of the cytoskeleton and recent studies have elucidated regulation mechanisms governing this process. This review describes changes in gene expression patterns of cytoskeletal associated proteins during TGFβ-induced EMT. It further reports TGFβ-induced intracellular signaling cascades that regulate cytoskeletal reorganization during EMT. Finally, it highlights how changes in cytoskeletal architecture during EMT can regulate gene expression, thus further promoting EMT progression.

HGF/c-MET Axis in Tumor Microenvironment and Metastasis Formation

Tumor metastases are responsible for approximately 90% of all cancer-related deaths. Metastasis formation is a multistep process that requires acquisition by tumor cells of a malignant phenotype that allows them to escape from the primary tumor site and invade other organs. Each step of this mechanism involves a deep crosstalk between tumor cells and their microenvironment where the host cells play a key role in influencing metastatic behavior through the release of many secreted factors. Among these signaling molecules, Hepatocyte Growth Factor (HGF) is released by many cell types of the tumor microenvironment to target its receptor c-MET within the cells of the primary tumor. Many studies reveal that HGF/c-MET axis is implicated in various human cancers, and genetic and epigenetic gain of functions of this signaling contributes to cancer development through a variety of mechanisms. In this review, we describe the specific types of cells in the tumor microenvironment that release HGF in order to promote the metastatic outgrowth through the activation of extracellular matrix remodeling, inflammation, migration, angiogenesis, and invasion. We dissect the potential use of new molecules that interfere with the HGF/c-MET axis as therapeutic targets for future clinical trials in cancer disease.

Targeting met mediated epithelial-mesenchymal transition in the treatment of breast cancer

Mesenchymal epithelial transition factor receptor (Met) is a receptor tyrosine kinase that plays a critical role in promoting cancer cell malignant progression. Met is activated by its ligand hepatocyte growth factor (HGF). HGF-dependent Met activation plays an important role in stimulating epithelial-mesenchymal transition (EMT) in tumor cells, resulting in increased tumor cell proliferation, survival, motility, angiogenesis, invasion, and metastasis. The HGF/Met axis has thus attracted great interest as a potential target in the development of novel cancer therapies. In an effort to suppress tumor cell malignant progression, efforts have been made to develop agents capable of inhibiting inhibit Met-induced EMT, including specific Met tyrosine kinase inhibitors, HGF antagonists that interfere with HGF binding to Met, and antibodies that prevent Met activation and/or dimerization. Tocotrienols, a subgroup within the vitamin E family of compounds, display potent anticancer activity that results, at least in part, from inhibition of HGF-dependent Met activation and signaling. The present review will provide a brief summary of the increasing importance of the HGF/Met axis as an attractive target for cancer chemotherapy and the role of tocotrienols in suppressing Met activation, signaling and HGF-induced EMT in breast cancer cells. Evidence provided suggests that γ-tocotrienol therapy may afford significant benefit in the treatment of breast cancers characterized by Met dysregulation.

Biomechanics of TGFβ-induced epithelial-mesenchymal transition: implications for fibrosis and cancer

Fibrosis, a disease that results in loss of organ function, contributes to a significant number of deaths worldwide and sustained fibrotic activation has been suggested to increase the risk of developing cancer in a variety of tissues. Fibrogenesis and tumor progression are regulated in part through the activation and activity of myofibroblasts. Increasing evidence links myofibroblasts found within fibrotic lesions and the tumor microenvironment to a process termed epithelial-mesenchymal transition (EMT), a phenotypic change in which epithelial cells acquire mesenchymal characteristics. EMT can be stimulated by soluble signals, including transforming growth factor (TGF)-β, and recent studies have identified a role for mechanical cues in directing EMT. In this review, we describe the role that EMT plays in fibrogenesis and in the progression of cancer, with particular emphasis placed on biophysical signaling mechanisms that control the EMT program. We further describe specific TGFβ-induced intracellular signaling cascades that are affected by cell- and tissue-level mechanics. Finally, we highlight the implications of mechanical induction of EMT on the development of treatments and targeted intervention strategies for fibrosis and cancer.

Olive phenolics as c-Met inhibitors: (-)-Oleocanthal attenuates cell proliferation, invasiveness, and tumor growth in breast cancer models

Dysregulation of the Hepatocyte growth factor (HGF)/c-Met signaling axis upregulates diverse tumor cell functions, including cell proliferation, survival, scattering and motility, epithelial-to-mesenchymal transition (EMT), angiogenesis, invasion, and metastasis. (-)-Oleocanthal is a naturally occurring secoiridoid from extra-virgin olive oil, which showed antiproliferative and antimigratory activity against different cancer cell lines. The aim of this study was to characterize the intracellular mechanisms involved in mediating the anticancer effects of (-)-oleocanthal treatment and the potential involvement of c-Met receptor signaling components in breast cancer. Results showed that (-)-oleocanthal inhibits the growth of human breast cancer cell lines MDA-MB-231, MCF-7 and BT-474 while similar treatment doses were found to have no effect on normal human MCF10A cell growth. In addition, (-)-oleocanthal treatment caused a dose-dependent inhibition of HGF-induced cell migration, invasion and G1/S cell cycle progression in breast cancer cell lines. Moreover, (-)-oleocanthal treatment effects were found to be mediated via inhibition of HGF-induced c-Met activation and its downstream mitogenic signaling pathways. This growth inhibitory effect is associated with blockade of EMT and reduction in cellular motility. Further results from in vivo studies showed that (-)-oleocanthal treatment suppressed tumor cell growth in an orthotopic model of breast cancer in athymic nude mice. Collectively, the findings of this study suggest that (-)-oleocanthal is a promising dietary supplement lead with potential for therapeutic use to control malignancies with aberrant c-Met activity.

Sustained elevation of Snail promotes glial-mesenchymal transition after irradiation in malignant glioma

BACKGROUND

Ionizing irradiation is an effective treatment for malignant glioma (MG); however, a higher rate of recurrence with more aggressive phenotypes is a vital issue. Although epithelial-mesenchymal transition (EMT) is involved in irradiation-induced cancer progression, the role for such phenotypic transition in MG remains unknown.

METHODS

To investigate the mechanism of irradiation-dependent tumor progression in MG, we performed immunohistochemistry (IHC) and qRT-PCR using primary and recurrent MG specimens, MG cell lines, and primary culture cells of MG. siRNA technique was used for MG cell lines.

RESULTS

In 22 cases of clinically recurrent MG, the expression of the mesenchymal markers vimentin and CD44 was found to be increased by IHC. In paired identical MG of 7 patients, the expression of collagen, MMPs, and YKL-40 were also elevated in the recurrent MGs, suggesting the The Cancer Genome Atlas-based mesenchymal subtype. Among EMT regulators, sustained elevation of Snail was observed in MG cells at 21 days after irradiation. Cells exhibited an upregulation of migration, invasion, numbers of focal adhesion, and MMP-2 production, and all of these mesenchymal features were abrogated by Snail knockdown. Intriguingly, phosphorylation of ERK1/2 and GSK-3β were increased after irradiation in a Snail-dependent manner, and TGF-β was elevated in both fibroblasts and macrophages but not in MG cells after irradiation. It was noteworthy that irradiated cells also expressed stemness features such as SOX2 expression and tumor-forming potential in vivo.

CONCLUSIONS

We here propose a novel concept of glial-mesenchymal transition after irradiation in which the sustained Snail expression plays an essential role.

Understanding the impact of 2D and 3D fibroblast cultures on in vitro breast cancer models

The utilization of 3D, physiologically relevant in vitro cancer models to investigate complex interactions between tumor and stroma has been increasing. Prior work has generally focused on the cancer cells and, the role of fibroblast culture conditions on tumor-stromal cell interactions is still largely unknown. Here, we focus on the stroma by comparing functional behaviors of human mammary fibroblasts (HMFs) cultured in 2D and 3D and their effects on the invasive progression of breast cancer cells (MCF10DCIS.com). We identified increased levels of several paracrine factors from HMFs cultured in 3D conditions that drive the invasive transition. Using a microscale co-culture model with improved compartmentalization and sensitivity, we demonstrated that HMFs cultured in 3D intensify the promotion of the invasive progression through the HGF/c-Met interaction. This study highlights the importance of the 3D stromal microenvironment in the development of multiple cell type in vitro cancer models.

Combined γ-tocotrienol and Met inhibitor treatment suppresses mammary cancer cell proliferation, epithelial-to-mesenchymal transition and migration

OBJECTIVES

Dysregulation of Met signalling is associated with malignant transformation. Combined treatment has been shown to reduce Met activation and mammary tumour cell proliferation. Experiments here, were conducted to determine mechanisms involved in mediating anti-cancer effects of combined γ-tocotrienol and SU11274 (Met inhibitor) treatment in various mammary cancer cell lines.

MATERIALS AND METHODS

Treatment effects on mouse (+SA) and human (MCF-7, and MDA-MB-231) mammary cancer cell lines, and normal mouse (CL-S1) and human (MCF10A) mammary epithelial cell lines were compared. Cell proliferation and survival were determined by MTT assay and Ki-67 staining; protein expression was determined by western blot analysis. Immunofluorescence staining was also used to characterize expression and localization of multiple epithelial and mesenchymal markers. Cell migration was determined using a wound-healing assay.

RESULTS

Combined treatment with γ-tocotrienol and SU11274 resulted in synergistic inhibition of +SA, MCF-7, and MDA-MB-231, but not CL-S1 or MCF10A cell growth that was associated with reduction in Akt STAT1/5 and NFκB activation and corresponding blockade in epithelial-to-mesenchymal transition, as indicated by increased expression of E-cadherin, β-catenin, and cytokeratins 8/18 (epithelial markers) and corresponding reduction in vimentin (mesenchymal marker) and reduction in cancer cell motility.

CONCLUSIONS

Suggest that combined γ-tocotrienol and Met inhibitor treatment may provide benefit in treatment of breast cancers characterized by aberrant Met activity.

Angiotensin II enhances epithelial-to-mesenchymal transition through the interaction between activated hepatic stellate cells and the stromal cell-derived factor-1/CXCR4 axis in intrahepatic cholangiocarcinoma

We previously reported that hepatic stellate cells (HSCs) activated by angiotensin II (AngII) facilitate stromal fibrosis and tumor progression in intrahepatic cholangiocarcinoma (ICC). AngII has been known as a growth factor which can promote epithelial-to-mesenchymal transition (EMT) in renal epithelial cells, alveolar epithelial cells and peritoneal mesothelial cells. However, in the past, the relationship between AngII and stromal cell-derived factor-1 (SDF-1) in the microenvironment around cancer and the role of AngII on EMT of cancer cells has not been reported in detail. SDF-1 and its specific receptor, CXCR4, are now receiving attention as a mechanism of cell progression and metastasis. In this study, we examined whether activated HSCs promote tumor fibrogenesis, tumor progression and distant metastasis by mediating EMT via the AngII/AngII type 1 receptor (AT-1) and the SDF-1/CXCR4 axis. Two human ICC cell lines and a human HSC line, LI-90, express CXCR4. Significantly higher concentration of SDF-1α was released into the supernatant of LI-90 cells to which AngII had been added. SDF-1α increased the proliferative activity of HSCs and enhanced the activation of HSCs as a growth factor. Furthermore, addition of SDF-1α and AngII enhanced the increase of the migratory capability and vimentin expression, reduced E-cadherin expression, and translocated the expression of β-catenin into the nucleus and cytoplasm in ICC cells. Co-culture with HSCs also enhanced the migratory capability of ICC cells. These findings suggest that SDF-1α, released from activated HSCs and AngII, play important roles in cancer progression, tumor fibrogenesis, and migration in autocrine and paracrine fashion by mediating EMT. Our mechanistic findings may provide pivotal insights into the molecular mechanism of the AngII and SDF-1α-initiated signaling pathway that regulates fibrogenesis in cancerous stroma, tumor progression and meta-stasis of tumor cells expressing AT-1 and CXCR4.

Characterization of breast cancer interstitial fluids by TmT labeling, LTQ-Orbitrap Velos mass spectrometry, and pathway analysis

Cancer is currently considered as the end point of numerous genomic and epigenomic mutations and as the result of the interaction of transformed cells within the stromal microenvironment. The present work focuses on breast cancer, one of the most common malignancies affecting the female population in industrialized countries. In this study, we perform a proteomic analysis of bioptic samples from human breast cancer, namely, interstitial fluids and primary cells, normal vs disease tissues, using tandem mass tags (TmT) quantitative mass spectrometry combined with the MudPIT technique. To the best of our knowledge, this work, with over 1700 proteins identified, represents the most comprehensive characterization of the breast cancer interstitial fluid proteome to date. Network analysis was used to identify functionally active networks in the breast cancer associated samples. From the list of differentially expressed genes, we have retrieved the associated functional interaction networks. Many different signaling pathways were found activated, strongly linked to invasion, metastasis development, proliferation, and with a significant cross-talking rate. This pilot study presents evidence that the proposed quantitative proteomic approach can be applied to discriminate between normal and tumoral samples and for the discovery of yet unknown carcinogenesis mechanisms and therapeutic strategies.

Stromal micropapillary component as a novel unfavorable prognostic factor of lung adenocarcinoma

BACKGROUND

Pulmonary adenocarcinomas with a micropapillary component having small papillary tufts and lacking a central fibrovascular core are thought to result in poor prognosis. However, the component consists of tumor cells often floating within alveolar spaces (aerogenous micropapillary component [AMPC]) rather than invading fibrotic stroma observed in other organs like breast (stromal invasive micropapillary component [SMPC]). We previously observed cases of lung adenocarcinoma with predominant SMPC that was associated with micropapillary growth of tumors in fibrotic stroma observed in other organs. We evaluated the incidence and clinicopathological characteristics of SMPC in lung adenocarcinoma cases.

PATIENTS AND METHODS

We investigated the clinicopathological characteristics and prognostic significance of SMPC in lung adenocarcinoma cases by reviewing 559 patients who had undergone surgical resection. We examined the SMPC by performing immunohistochemical analysis with 17 antibodies and by genetic analysis with epidermal growth factor receptor (EGFR) and KRAS mutations.

RESULTS

SMPC-positive (SMPC(+)) tumors were observed in 19 cases (3.4%). The presence of SMPC was significantly associated with tumor size, advanced-stage disease, lymph node metastasis, pleural invasion, lymphatic invasion, and vascular invasion. Patients with SMPC(+) tumors had significantly poorer outcomes than those with SMPC-negative tumors. Multivariate analysis revealed that SMPC was a significant independent prognostic factor of lung adenocarcinoma, especially for disease-free survival of pathological stage I patients (p = 0.035). SMPC showed significantly higher expression of E-cadherin and lower expression of CD44 than the corresponding expression levels shown by AMPC and showed lower surfactant apoprotein A and phospho-c-Met expression level than corresponding expression levels shown by tumor cell components without a micropapillary component. Fourteen cases with SMPC(+) tumors (74%) showed EGFR mutations, and none of them showed KRAS mutations.

CONCLUSIONS

SMPC(+) tumors are rare, but they may be associated with a poor prognosis and have different phenotypic and genotypic characteristics from those of AMPC(+) tumors.

Establishment and characterization of two 5-fluorouracil-resistant hepatocellular carcinoma cell lines

5-Fluorouracil (5-FU) chemotherapy is the first choice treatment for advanced hepatocellular carcinoma (HCC), and resistance is the major obstacle to successful treatment. Recent studies have reported that epithelial-to-mesenchymal transition (EMT) is associated with chemoresistance in cancers. We speculated that EMT and 5-FU metabolism are related to the mechanism of 5-FU resistance. First, two 5-FU-resistant cell lines, HLF-R4 and HLF-R10, were established from the HLF undifferentiated human HCC cell line. Whereas cell growth was similar in the HLF and HLF-R cell lines, HLF-Rs are about 4- and 10-fold more resistant compared with the HLF cells; thus, we named these cell lines HLF-R4 and HLF-R10, respectively. The terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling assay also showed a dramatically decreased number of apoptotic cells in the HLF-Rs after treatment with 5-FU. We next assessed the characteristics of the HLF, HLF-R4 and HLF-R10 cells. Consistent with our hypothesis, the HLF-Rs had typical morphologic phenotypes of EMT, loss of cell-cell adhesion, spindle-shaped morphology and increased formation of pseudopodia. Real-time quantitative reverse transcriptase polymerase chain reaction data showed downregulated E-cadherin and upregulated Twist-1 and also indicated that EMT changes occurred in the HLF-Rs. We also found decreased ribonucleotide reductase and increased multidrug resistance protein 5 genes in the HLF-R cells. Our results suggested that the metabolism of EMT and 5-FU has important roles in 5-FU chemoresistance in the HLF-R cells, and that the HLF-R cells would be useful in vitro models for understanding the 5-FU-resistant mechanisms in HCC.

γ-Tocotrienol inhibits HGF-dependent mitogenesis and Met activation in highly malignant mammary tumour cells

OBJECTIVES

  Aberrant Met signalling is associated with aggressive cancer cell phenotypes. γ-tocotrienol displays potent anti-cancer activity that is associated with suppression of HER/ErbB receptor signalling. Experiments were conducted to investigate the effects of γ-tocotrienol treatment on HGF-dependent +SA mammary tumour cell proliferation, upon Met activation.

MATERIALS AND METHODS

  The +SA cells were maintained in serum-free defined media containing 10 ng/ml HGF as the mitogen. Cell viability was determined using the MTT assay, western blot analysis was used to measure protein expression, and Met expression and activation were determined using immunofluorescent staining.

RESULTS AND CONCLUSIONS

  Treatment with γ-tocotrienol or Met inhibitor, SU11274, significantly inhibited HGF-dependent +SA cell replication in a dose-responsive manner. Treatment with 4 μmγ-tocotrienol reduced both total Met levels and HGF-induced Met autophosphorylation. In contrast, similar treatment with 5.5 μm SU11274 inhibited HGF-induced Met autophosphorylation, but had no effect on total Met levels. Combined treatment with subeffective doses of γ-tocotrienol (2 μm) and SU11274 (3 μm) resulted in significant inhibition of +SA cell expansion compared to treatment with individual agents alone. These findings show, for the first time, the inhibitory effects of γ-tocotrienol on Met expression and activation, and strongly suggest that γ-tocotrienol treatment may provide significant health benefits in prevention and/or treatment of breast cancer, in women with deregulated HGF/Met signalling.

Co-expression of hepatocyte growth factor and c-Met predicts peritoneal dissemination established by autocrine hepatocyte growth factor/c-Met signaling in gastric cancer

Epithelial-mesenchymal transition (EMT) promotes and facilitates migration and invasion of epithelial tumor cells. EMT is induced by factors such as hepatocyte growth factor (HGF). This study aimed to establish whether the HGF/c-Met pathway is associated with gastric cancer metastasis; especially peritoneal dissemination. HGF and c-Met expression and EMT-related molecules were evaluated using real-time PCR and immunohistochemistry. The role of the HGF/c-Met pathway in EMT and anoikis was determined, and kinase inhibitor SU11274 was tested for its ability to block HGF-induced biological effects. In HGF(-) /c-Met(+) gastric cancer cells, recombinant HGF promoted an EMT phenotype that was characterized by morphology, impaired E-cadherin and induction of vimentin. HGF promoted cell growth, invasiveness and migration and inhibition of anoikis. SU11274 blocked HGF-induced EMT and biological effects in vitro. In HGF(+) /c-Met(+) gastric cancer cells, HGF did not affect the biological outcome of EMT and anoikis, but SU11274 exerted the same inhibitory effects as in HGF(-) /c-Met(+) cells. In vivo, HGF(+) /c-Met(+) gastric cancer cells only established peritoneal dissemination and SU11274 inhibited tumor growth. Clinically, HGF expression was significantly correlated with c-Met expression in gastric cancer. Increased HGF and c-Met had a significant association with poor prognosis and predicted peritoneal dissemination. We demonstrated that the HGF/c-Met pathway induces EMT and inhibition of anoikis in gastric cancer cells. Co-expression of HGF and c-Met has the potential to promote peritoneal dissemination in gastric cancer. Blockade of the autocrine HGF/c-Met pathway could be clinically useful for the treatment of peritoneal dissemination in gastric cancer.

Vascular endothelial growth factor receptor-1 activation mediates epithelial to mesenchymal transition in hepatocellular carcinoma cells

PURPOSE

To explore the molecular mechanism of Vascular endothelial growth factor receptor-1 (VEGFR-1) in invasion and metastasis of hepatocellular carcinoma.

METHODS

Reverse transcription polymerase chain reaction was performed to test expression of VEGFR-1 and its ligand VEGF-B19 in four hepatoma carcinoma cell. Fluorescent immunohistochemistry and western blotting were used to test the change of expression of E-cadherin or α-catenin.

RESULTS

VEGF-B-treated cells exhibited a change in E-cadherin from an organized, membrane-bound structure to a disorganized state that was dispersed throughout the cytoplasm. The maximal changes in E-cadherin were observed 24 hr after treatment of cells with VEGF-B. α-catenin was observed to translocate to the nucleus from its usual membrane-bound location 24 hr after treatment with either VEGF-B. Expression of the epithelial adhesion molecules E-cadherin was observed to decrease 48 hours after VEGF-B treatment. The nuclear expression of α-catenin was observed to increase 24 hr after treatment with VEGF-B.

CONCLUSIONS

VEGFR-1 on tumor cells may contribute to the aggressive behavior of hepatocellular carcinoma cells by inducing epithelial to mesenchymal transition (EMT). Targeting VEGFR-1 and downstream mediators of EMT may provide the foundation for the development of novel therapeutic approaches for this morbid and lethal disease.

FMNL2 enhances invasion of colorectal carcinoma by inducing epithelial-mesenchymal transition

FMNL2 is a member of diaphanous-related formins that control actin-dependent processes such as cell motility and invasion. Its overexpression in metastatic cell lines and tissues of colorectal carcinoma has been associated with aggressive tumor development in our previous study. But its specific role in cancer is largely unknown. Here we report that FMNL2 is involved in epithelial-mesenchymal transition (EMT) maintenance in human colorectal carcinoma cells. A positive correlation between FMNL2 and vimentin expression and an inverse correlation between FMNL2 and E-cadherin expression were found in colorectal carcinoma cell lines and cancer tissues. Specific knockdown of FMNL2 led to an epithelial-state transition, confirmed by the cobblestone-like phenotype, upregulation of E-cadherin, α-catenin, and γ-catenin, and downregulation of vimentin, snail, slug. Loss of FMNL2 expression lowered the ability of TGF-β to induce cell invasion and EMT, as shown by morphology and the expression levels. Upregulation of vimentin, slug, snail, downregulation of E-cadherin and activation of receptor-Smad3 phosphorylation were observed in M5 and MDCK cells induced by TGF-β, whereas altered expression of these markers was not obvious in FMNL2-depleting M5 cells. High levels of activation of p-MAPK and p-MEK, but not p-PI3K and p-AKT, were observed in SW480/FMNL2+ cells compared with control cells. Treatment with U0126 could abrogate the activation of p-MAPK and p-MEK, whereas LY294002 treatment had no effect on the PI3K/AKT pathway. In conclusion, these findings identify a novel EMT and tumor promoting function for FMNL2, which is involved in TGF-β-induced EMT and colorectal carcinoma cell invasion via Smad3 effectors, or in collaboration with MAPK/MEK pathway.

Epithelial-mesenchymal transition in mouse mammary tumorigenesis

Epithelial-mesenchymal transition tumorigenesis in the mouse has been described for over 100 years using various terms and with little comprehension of the underlying mechanisms. Recently, epithelial-mesenchymal transition tumors have been recognized in mammary glands of genetically engineered mice. This review provides a historical perspective and the current observations in the context of some of the key molecular biology. The biology of mouse mammary epithelial-mesenchymal transition tumorigenesis is discussed with comparisons to human breast cancer.

Fibroblast hepatocyte growth factor promotes invasion of human mammary ductal carcinoma in situ

Stromal-derived hepatocyte growth factor (HGF) acting through its specific proto-oncogene receptor c-Met has been suggested to play a paracrine role in the regulation of tumor cell migration and invasion. The transition from preinvasive ductal carcinoma in situ (DCIS) to invasive breast carcinoma is marked by infiltration of stromal fibroblasts and the loss of basement membrane. We hypothesized that HGF produced by the infiltrating fibroblasts may alter proteolytic pathways in DCIS cells, and, to study this hypothesis, established three-dimensional reconstituted basement membrane overlay cocultures with two human DCIS cell lines, MCF10.DCIS and SUM102. Both cell lines formed large dysplastic structures in three-dimensional cultures that resembled DCIS in vivo and occasionally developed invasive outgrowths. In coculture with HGF-secreting mammary fibroblasts, the percentage of DCIS structures with invasive outgrowths was increased. Activation of c-Met with conditioned medium from HGF-secreting fibroblasts or with recombinant HGF increased the percentage of DCIS structures with invasive outgrowths, their degradation of collagen IV, and their secretion of urokinase-type plasminogen activator and its receptor. In agreement with the in vitro findings, coinjection with HGF-secreting fibroblasts increased invasiveness of MCF10.DCIS xenografts in severe combined immunodeficient mice. Our study shows that paracrine HGF/c-Met signaling between fibroblasts and preinvasive DCIS cells enhances the transition to invasive carcinomas and suggests that three-dimensional cocultures are appropriate models for testing therapeutics that target tumor microenvironment-enhanced invasiveness.

Decreased Serum Hepatocyte Growth Factor (HGF) in Autistic Children with Severe Gastrointestinal Disease

Aim:

To assess serum Hepatocyte Growth Factor (HGF) levels in autistic children with severe gastrointestinal (GI) disease and to test the hypothesis that there is a relationship between GI pathology and HGF concentration.

Subjects and Methods:

Serum from 29 autistic children with chronic digestive disease (symptoms for a minimum of 6–12 months), most with ileo-colonic lymphoid nodular hyperplasia (LNH—markedly enlarged lymphoid nodules) and inflammation of the colorectum, small bowel and/or stomach), and 31 controls (11 age matched autistic children with no GI disease, 11 age matched non autistic children without GI disease and 9 age matched non autistic children with GI disease) were tested for HGF using ELISAs. HGF concentration of autistic children with GI disease was compared to GI disease severity.

Results:

Autistic children with GI disease had significantly lower serum levels of HGF compared to controls (autistic without GI disease; p = 0.0005, non autistic with no GI disease; p = 0.0001, and non autistic with GI disease; p = 0.001). Collectively, all autistic children had significantly lower HGF levels when compared to non autistic children (p < 0.0001). We did not find any relationship between severity of GI disease and HGF concentration in autistic children with GI disease.

Discussion:

These results suggest an association between HGF serum levels and the presence of GI disease in autistic children and explain a potential functional connection between the Met gene and autism. The concentration of serum HGF may be a useful biomarker for autistic children, especially those with severe GI disease.

Increased production and secretion of HGF alpha-chain and an antagonistic HGF fragment in a human breast cancer progression model

Invasive human breast carcinomas frequently coexpress increased hepatocyte growth factor (HGF) and its receptor Met, suggesting that establishment of an autocrine HGF loop is important in malignant disease. This study examines the expression patterns of HGF and Met activation during tumorigenesis and metastasis using a MCF10A-based model of Ha-Ras-induced human breast cancer progression. Deregulation of cadherin-based cell-cell adhesions, decreased expression of cytokeratins 8/18 and increased activity of matrix metalloproteinases such as MMP-2 occurs in premalignant and malignant (metastatic) cell lines compared to the parental nonmalignant cell line. Compared to the benign parent cell line, premalignant and malignant cell lines exhibit increased secretion of full length HGF alpha-chain and elevated Met tyrosine phosphorylation in complete medium. Interestingly, the premalignant and malignant cells also secrete a approximately 55 kDa HGF fragment. Epitope mapping of the approximately 55 kDa HGF fragment supports the presence of the N-terminal domain of the HGF alpha-chain with a truncation in the C-terminal domain. The approximately 55 kDa HGF fragment shows mobility in SDS-PAGE faster than HGF alpha-chain, but slightly slower than NK4, a previously established full antagonist of HGF. The separated approximately 55 kDa HGF fragment binds to animmobilized Met-IgG fusion protein, and inhibits both HGF/Met-IgG binding and HGF-induced Met-tyrosine phosphorylation. These results are the first demonstration of an antagonistic approximately 55 kDa HGF fragment secreted during breast carcinoma progression, which may have a negative regulatory effect on HGF signaling in premalignant breast epithelial cells.

Somatic mutation and functional polymorphism of a novel regulatory element in the HGF gene promoter causes its aberrant expression in human breast cancer

The HGF gene is transcriptionally silenced in normal differentiated breast epithelial cells, but its repression fails to occur in mammary carcinoma tissues and cell lines. The molecular mechanisms underpinning aberrant HGF expression in breast cancer cells are unknown. Here we report the discovery of a DNA element located 750 bp upstream from the transcription start site in the human HGF promoter that acts as a transcriptional repressor and is a target of deletion mutagenesis in human breast cancer cells and tissues. This HGF promoter element consists of a mononucleotide repeat of 30 deoxyadenosines (30As), which we have termed "deoxyadenosine tract element" (DATE). Functional studies revealed that truncation mutations within DATE have profound local and global effects on the HGF promoter region by modulating chromatin structure and DNA-protein interactions, leading to constitutive activation of the HGF promoter in human breast carcinoma cell lines. We found that 51% of African Americans and 15% of individuals of mixed European descent with breast cancer harbor a truncated DATE variant (25As or fewer) in their breast tumors and that the truncated allele is associated with cancer incidence and aberrant HGF expression. Notably, breast cancer patients with the truncated DATE variant are substantially younger than those with a wild-type genotype. We also suggest that DATE may be used as a potential genetic marker to identify individuals with a higher risk of developing breast cancer.

Delphinidin inhibits cell proliferation and invasion via modulation of Met receptor phosphorylation

The HGF/Met signaling pathway is deregulated in majority of cancers and is associated with poor prognosis in breast cancer. Delphinidin, present in pigmented fruits and vegetables possesses potent anti-oxidant, anti-inflammatory and anti-angiogenic properties. Here, we assessed the anti-proliferative and anti-invasive effects of delphinidin on HGF-mediated responses in the immortalized MCF-10A breast cell line. Treatment of cells with delphinidin prior to exposure to exogenous HGF resulted in the inhibition of HGF-mediated (i) tyrosyl-phosphorylation and increased expression of Met receptor, (ii) phosphorylation of downstream regulators such as FAK and Src and (iii) induction of adaptor proteins including paxillin, Gab-1 and GRB-2. In addition, delphinidin treatment resulted in significant inhibition of HGF-activated (i) Ras-ERK MAPKs and (ii) PI3K/AKT/mTOR/p70S6K pathways. Delphinidin was found to repress HGF-activated NFkappaB transcription with a decrease in (i) phosphorylation of IKKalpha/beta and IkappaBalpha, and (ii) activation and nuclear translocation of NFkappaB/p65. Inhibition of HGF-mediated membrane translocation of PKCalpha as well as decreased phosphorylation of STAT3 was further observed in delphinidin treated cells. Finally, decreased cell viability of Met receptor expressing breast cancer cells treated with delphinidin argues for a potential role of the agent in the prevention of HGF-mediated activation of various signaling pathways implicated in breast cancer.

A novel activating role of SRC and STAT3 on HGF transcription in human breast cancer cells

We have previously determined that the HGF promoter can be transactivated by a combination of activated Src and wild-type Stat3 in the mouse breast cell lines HC11 and SP1. To determine if this pathway is of relevance for the human disease, a series of human breast and other human cells lines were examined, and the status of key proteins in these cells determined. All of the human breast cell lines exhibited strong transactivation by a combination of activated Src and Stat3. This activation was dependent on a Stat3 recognition element present at nt-95. The exception was the ErbB2 over-expressing cell line SK-BR-3 where Stat3 alone could transactivate HGF though Src augmented this effect. Increased phosphorylation of Stat3 tyrosine 705 was also observed in this line. Analysis of three ovarian cell lines revealed that Src/Stat3 expression was not able to activate the HGF promoter in two of these lines (SKOV3 and IOSE-80PC). Src/Stat3 expression did activate HGF transcription in OVCAR3 cells, but this effect was not mediated by the Stat3 site at nt-95. Stat3 phosphorylation at tyrosine 705 was observed in IOSE-80PC cells, but was insufficient to allow for activation of the HGF promoter. Human kidney (HEK293) and cervical carcinoma (HeLa) cells were also not Src/Stat3 permissive, despite high levels of Stat3 phospho-Y705. These results suggest that human breast cells are a uniquely permissive environment for HGF transactivation by Src/Stat3 which may allow for the inappropriate activation of HGF transcription during the early stages of breast transformation. This could lead to paracrine or autocrine activation of the Met receptor in breast carcinoma cells.

c-Src/Histone Deacetylase 3 Interaction Is Crucial for Hepatocyte Growth Factor–Dependent Decrease of CXCR4 Expression in Highly Invasive Breast Tumor Cells

Hepatocyte growth factor (HGF), a cytokine of tumor microenvironment, exerts opposite effects on CXCR4 expression in MCF-7 (low invasive) and MDA-MB231 (highly invasive) breast carcinoma cells, and here, we show that completely different molecular mechanisms downstream of c-Src activation were involved. As experimental models, we used cells transfected with two CXCR4 promoter constructs and treated with HGF or cotransfected with c-Src wild-type (Srcwt) expression vector; phospho-c-Src formation was enhanced in both cell lines. In MCF-7 cells, consistent with activations of CXCR4Luc constructs after HGF treatment and Srcwt expression, Ets1 and nuclear factor-kappaB (NF-kappaB) transcription factors were activated. In contrast, in MDA-MB231 cells, CXCR4Luc construct, Ets1 and NF-kappaB activities decreased. The divergence point seemed to be downstream of HGF/c-Src and consisted in the interaction between c-Src and the substrate histone deacetylase 3 (HDAC3). Only in MDA-MB231 cells, HDAC3 level was enhanced in membranes and nuclei 30 min after HGF and colocalized/coimmunoprecipitated with phospho-c-Src and phosphotyrosine. Thus, the CXCR4 induction by HGF in MCF-7 cells required NF-kappaB and Ets1 activations, downstream of phosphoinositide-3-kinase/Akt, whereas in HGF-treated MDA-MB231 cells, HDAC3 activation via c-Src probably caused a reduction of transcription factor activities, such as that of NF-kappaB. These results indicate possible roles of HGF in invasive growth of breast carcinomas. By enhancing CXCR4 in low invasive tumor cells, HGF probably favors their homing to secondary sites, whereas by suppressing CXCR4 in highly invasive cells, HGF might participate to retain them in the metastatic sites.

Tyrosine kinase receptor RON in human pancreatic cancer: expression, function, and validation as a target

BACKGROUND

Specific tyrosine kinase receptors such as c-MET mediate epithelial-mesenchymal (EMT) transition, leading to phenotypic alterations associated with increased cell motility. It was hypothesized that RON, a tyrosine kinase receptor related to c-MET, would be expressed in human pancreatic cancer cells, induce EMT, and would thus serve as a target for therapy in a preclinical model.

METHODS

RON expression in human pancreatic cancer specimens was assessed by immunohistochemistry. In pancreatic cancer cell lines, RON expression was assessed by reverse-transcriptase polymerase chain reaction (PCR) and Western blot analysis. The human pancreatic cancer cell line L3.6pl, with high RON expression, was exposed to macrophage stimulating protein (MSP), the RON ligand, and assessed for cell migration, invasion, and changes associated with EMT. Western blot analysis and immunofluorescent staining were used to assess alterations in protein expression and cellular location, respectively. A RON monoclonal antibody (MoAb) was used to block ligand-induced activation of RON.

RESULTS

Immunohistochemical staining revealed RON overexpression in 93% of human pancreatic cancer specimens relative to nonmalignant ductal tissue. RON mRNA and protein was expressed in 9 of 9 human pancreatic cancer cell lines. Treatment of L3.6pl cells with MSP increased Erk phosphorylation, cell migration, and invasion (P < .001). RON activation led to a decrease in membrane-bound E-cadherin in association with nuclear translocation of beta-catenin. RON MoAb inhibited downstream signaling as well as cell migration and invasion. In nude mice, RON MoAb inhibited subcutaneous and orthotopic tumor growth by about 60%.

CONCLUSIONS

RON activation induced molecular and cellular alterations consistent with EMT. Inhibition of RON activation inhibited tumor growth in vivo. Novel antineoplastic therapies designed to inhibit RON activity may hinder mechanisms critical for pancreatic tumor progression.

Chronic oxaliplatin resistance induces epithelial-to-mesenchymal transition in colorectal cancer cell lines

PURPOSE

Epithelial-to-mesenchymal transition (EMT) is a process whereby cells acquire molecular alterations that facilitate cell motility and invasion. In preliminary studies, we observed that oxaliplatin-resistant (OxR) colorectal cancer (CRC) cells underwent morphologic changes suggestive of a migratory phenotype, leading us to hypothesize that OxR CRC cells undergo EMT.

EXPERIMENTAL DESIGN

The human CRC cell lines KM12L4 and HT29 were exposed to increasing doses of oxaliplatin to establish stable cell lines resistant to oxaliplatin. Migration and invasion were assessed by modified Boyden chamber assays. Morphologic and molecular changes characteristic of EMT were determined by immunofluorescence staining and Western blot analyses.

RESULTS

The OxR cells showed phenotypic changes consistent with EMT: spindle-cell shape, loss of polarity, intercellular separation, and pseudopodia formation. KM12L4 and HT29 OxR cells exhibited an approximately 8- to 15-fold increase in migrating and invading cells, respectively (P < 0.005 for both). Immunofluorescence staining of OxR cells revealed translocation of E-cadherin and beta-catenin from their usual membrane-bound complex to the cytoplasm and nucleus, respectively. The OxR cells also had decreased expression of the epithelial adhesion molecules E-cadherin and plakoglobin and an increase in the mesenchymal marker vimentin. The KM12L4 OxR cells exhibited increased nuclear expression of Snail, an EMT-regulatory transcription factor, whereas the HT29 OxR cells exhibited an increase in nuclear expression of the EMT-associated transcription factor nuclear factor kappaB.

CONCLUSION

We hypothesize that induction of EMT may contribute to the decreased efficacy of therapy in chemoresistant CRC, as the tumor cells switch from a proliferative to invasive phenotype. Further understanding of the mechanisms of chemoresistance in CRC will enable improvements in chemotherapy for metastatic disease.

Osteopontin overexpression in breast cancer: Knowledge gained and possible implications for clinical management

Osteopontin (OPN) is a secreted protein that is overexpressed in a number of human cancers, and has been associated with increased metastatic burden and poor prognosis in breast cancer patients. The OPN protein contains several conserved structural elements including heparin- and calcium-binding domains, a thrombin-cleavage site, a CD44 binding site, and two integrin-binding sites. Experimental studies have shown that the ability of OPN to interact with a diverse range of factors, including cell surface receptors (integrins, CD44), secreted proteases (matrix metalloproteinases, urokinase plasminogen activator), and growth factor/receptor pathways (TGFalpha/EGFR, HGF/Met) is central to its role in malignancy. These complex signaling interactions can result in changes in gene expression, which ultimately lead to alterations in cell properties involved in malignancy such as adhesion, migration, invasion, enhanced tumor cell survival, tumor angiogenesis, and metastasis. Therefore, OPN is not merely associated with cancer, but rather it plays a multi-faceted functional role via complex molecular cross-talk with other factors. This review will focus on the role of OPN in breast cancer, in particular on the malignancy-promoting aspects of OPN that may reveal opportunities for new approaches to the clinical management of breast cancer.

Serum levels of hepatocyte growth factor/scatter factor in patients with liver metastases from breast cancer

OBJECTIVE

Recent studies have shown that the pleiotropic cytokine hepatocyte growth factor/scatter factor (HGF/SF) and its receptor c-Met play major roles in the malignant progression of numerous tumors. For patients with breast cancer liver metastases, increased serum levels of HGF/SF have been reported. We studied the relationship between the clinical course of the disease and the serum levels of HGF/SF in such patients.

METHODS

We examined 51 patients treated for breast cancer liver metastases. Serum concentrations of HGF/SF were measured before each therapy cycle and compared to the corresponding tumor marker levels.

RESULTS

Mean serum levels of HGF/SF in patients with liver metastases were increased above the reported reference levels of primary breast cancer patients. Serum levels of HGF/SF were correlated with tumor marker levels in a logarithmic relation (r = 0.47, p < 0.001). In some cases serum concentrations of HGF/SF changed similarly to the course of the corresponding tumor markers.

CONCLUSIONS

Serum levels of HGF/SF are associated with the clinical course of metastatic breast cancer patients with liver metastases. Further studies are required to clarify the potential value of the HGF/SF serum concentration as a tumor marker. HGF/SF and its receptor c-Met should be further evaluated as therapeutic targets.

Membrane Mucin Muc4 Induces Density-dependent Changes in ERK Activation in Mammary Epithelial and Tumor Cells

The membrane mucin Muc4 has been shown to alter cellular behavior through both anti-adhesive effects on cell-cell and cell-extracellular matrix interactions and its ability to act as an intramembrane ligand for the receptor tyrosine kinase ErbB2. The ERK pathway is regulated by both cell-matrix and cell-cell adhesion. An analysis of the effects of Muc4 expression on ERK phosphorylation in mammary tumor and epithelial cells, which exhibit both adhesion-dependent growth and contact inhibition of growth, showed that the effects are density dependent, with opposing effects on proliferating cells and contact-inhibited cells. In these cells, cell-matrix interactions through integrins are required for activation of the ERK mitogenesis pathway. However, cell-cell interactions via cadherins inhibit the ERK pathway. Expression of Muc4 reverses both of these effects. In contact-inhibited cells, Muc4 appears to activate the ERK pathway at the level of Raf-1; this activation does not depend on Ras activation. The increase in ERK activity correlates with an increase in cyclin D(1) expression in these cells. This abrogation of contact inhibition is dependent on the number of mucin repeats in the mucin subunit of Muc4, indicative of an anti-adhesive effect. The mechanism by which Muc4 disrupts contact inhibition involves a Muc4-induced relocalization of E-cadherin from adherens junctions at the lateral membrane of the cells to the apical membrane. Muc4-induced abrogation of contact inhibition may be an important mechanism by which tumors progress from an early, more benign state to invasiveness.

Hepatocyte growth factor activation inhibitors (HAI-1 and HAI-2) regulate HGF-induced invasion of human breast cancer cells

Hepatocyte growth factor (HGF) plays a plethora of roles in cancer metastasis and tumour growth. The interaction between tumour cells and their surrounding stromal environment is a crucial factor regulating tumour invasion and metastasis. Stromal fibroblasts are the main source of HGF in the body, and release HGF as an inactive precursor (pro-HGF). HGF activator (HGFA), matriptase, urokinase-type plasminogen activator and hepsin are the main factors responsible for converting pro-HGF into active HGF. HAI-1 and HAI-2 are 2 novel Kunitz-type serine protease inhibitors that regulate HGF activity through inhibition of HGFA, matriptase and hepsin action. Recent studies demonstrate that HAI-1 and HAI-2 may also potently inhibit a number of other pro-metastatic serine proteases and therefore have direct bearing on the spread of tumours. Our study examined the potential of these HAI's to suppress the influence of HGF and regulate cancer metastasis. We generated a retroviral expression system that induced HAI expression in a human fibroblast cell line. Forced expression of either HAI-1 or HAI-2 in these fibroblasts resulted in a dramatic decrease in the production of bioactive hepatocyte growth factor (HGF). This reduction in HGF activity subsequently suppressed HGF's metastatic influence on breast cancer cells. To further assess the anti-cancer properties of HAI-1 and HAI-2 we generated recombinant HAI proteins. These recombinant HAI proteins possessed the ability to potently quench HGF activity. We also demonstrate that these recombinant HAI's suppressed fibroblast-mediated breast cancer invasion. An additional ribozyme transgenes study revealed that elimination of HAI-1 and HAI-2 expression, in an MDA-MB-231 breast cancer cell line, significantly enhanced the migratory, proliferative and invasive nature of these breast cancer cells. Overall, our data demonstrates the important roles of HAI-1 and HAI-2 in cancer metastasis, and reveals that these serine protease inhibitors display strong therapeutic potential.

Prostaglandin E2 is a potent inhibitor of epithelial-to-mesenchymal transition: interaction with hepatocyte growth factor

Epithelial-to-mesenchymal transition (EMT) has emerged as a critical event in the pathogenesis of tubulointerstitial fibrosis. EMT is typically induced by transforming growth factor-beta1 (TGF-beta1) and inhibited by hepatocyte growth factor (HGF). The present study was undertaken to evaluate the potential role of cyclooxygenase (COX)-2-derived PGE2 in regulation of EMT in cultured Madin-Darby canine kidney (MDCK) cells, in the setting of HGF treatment. Exposure to 50 ng/ml HGF significantly induced COX-2 protein expression and PGE2 release, whereas other growth factors, including epidermal growth factor, the insulin-like growth factor I protein, platelet-derived growth factor-BB, and TGF-beta1, had no effects on COX-2 expression or PGE2 release. COX-2 induction by HGF was preceded by activation of ERK1/2, and an ERK1/2-specific inhibitor, U-0126 (10 microM), completely abolished HGF-induced COX-2 expression. Exposure of MDCK cells to 10 ng/ml TGF-beta1 for 72 h induced EMT as evidenced by conversion to the spindle-like morphology, loss of E-cadherin, and activation of alpha-smooth muscle actin. In contrast, treatment with 1 microM PGE2 completely blocked EMT, associated with a significant elevation of intracellular cAMP and complete blockade of TGF-beta1-induced oxidant production. cAMP-elevating agents, including 8-Br-cAMP, forskolin, and IBMX, inhibited EMT and associated oxidative stress induced by TGF-beta1, but inhibition of cAMP pathway with Rp-cAMP, the cAMP analog, and H89, the protein kinase A (PKA) inhibitor, did not block the effect of PGE2. The effect of HGF on EMT was inhibited by approximately 50% in the presence of a COX-2 inhibitor SC-58635 (10 microM). Therefore, our data suggest that PGE2 inhibits EMT via inhibition of oxidant production and COX-2-derived PGE2 partially accounts for the antifibrotic effect of HGF.

A novel activating function of c-Src and Stat3 on HGF transcription in mammary carcinoma cells

In the normal breast, hepatocyte growth factor (HGF) is primarily expressed by stromal cells, and stimulates in a paracrine manner epithelial cells expressing the HGF receptor (Met). In invasive human breast carcinomas, HGF and Met are frequently overexpressed, possibly establishing an autocrine HGF/Met loop that promotes tumour cell invasion. However, the mechanisms leading to autocrine HGF expression in carcinoma cells are not known. We previously demonstrated a cooperative effect between c-Src and Stat3 in the activation of HGF transcription in mammary carcinoma cells. The present report defines a novel Stat3 consensus site at nt -95 in the HGF promoter that is highly conserved in human and mouse, and is required for c-Src and Stat3 to activate HGF transcription in breast epithelial cells. DNA-protein binding studies demonstrated high affinity binding of a Stat3-containing complex to the nt -95 site. Endogenous Stat3 binding to this region of the HGF promoter in carcinoma cells expressing HGF was demonstrated using a chromatin immunoprecipitation assay. In addition, coexpression of Stat3 and activated c-Src caused increased expression of endogenous HGF mRNA and protein and marked cell scattering in breast epithelial cells. Our results delineate a novel c-Src/Stat3-dependent mechanism that regulates HGF promoter activity, and is linked to transformation of mammary epithelial cells.