Identification of a fibroblast-derived epithelial morphogen as hepatocyte growth factor

A phase Ib study of AMG 102 in combination with bevacizumab or motesanib in patients with advanced solid tumors

PURPOSE

This phase Ib study evaluated the safety, pharmacokinetics, pharmacodynamics, and antitumor activity of AMG 102, a fully human monoclonal antibody against hepatocyte growth factor/scatter factor (HGF/SF), in combination with bevacizumab or motesanib in patients with advanced solid tumors.

EXPERIMENTAL DESIGN

Patients with treatment-refractory advanced solid tumors were sequentially enrolled into four cohorts (3, 10, or 20 mg/kg AMG 102 plus 10 mg/kg bevacizumab i.v. every 2 weeks, or 3 mg/kg AMG 102 i.v. every 2 weeks plus 75 mg motesanib orally once daily).

RESULTS

Fourteen patients were enrolled and received AMG 102. The combination of AMG 102 with bevacizumab (n = 12) seemed to have acceptable toxicity. The number of patients (n = 2) who received AMG 102 plus motesanib was insufficient to adequately assess safety. No dose-limiting toxicities were reported. Enrollment in the motesanib cohort was suspended because of reports of cholecystitis in other motesanib studies. Treatment-emergent adverse events among patients receiving AMG 102 plus bevacizumab were generally mild and included fatigue (75%), nausea (58%), constipation (42%), and peripheral edema (42%). No anti-AMG 102 antibodies were detected. Bevacizumab did not seem to affect AMG 102 pharmacokinetics. Circulating total HGF/SF increased from baseline throughout the study. Eight of 10 evaluable patients had reductions in tumor dimensions, and stable disease at > or =8, > or =16, and > or =24 weeks occurred in 9, 7, and 4 patients, respectively. Progression-free survival ranged from 7.9 to 121.9 weeks.

CONCLUSIONS

AMG 102 in combination with bevacizumab was well tolerated. Further evaluation of AMG 102 in combination with antiangiogenic agents is warranted.

Hepatocyte growth factor receptor, c-Met, in human embryo salivary glands. An immunohistochemical study

Salivary gland morphogenesis involves complex, coordinated events that include epithelial-mesenchymal interactions. Mesenchymal-epithelial transition factor (c-Met) is the hepatocyte growth factor (HGF) receptor. The latter is a hepatotropic factor originally identified in rat serum and platelets. It is essential in fetal tissue development, where it regulates complex morphogenetic processes including extracellular matrix invasion, cell migration, cell polarization and tubulogenesis. The c-Met/HGF system is believed to participate in epithelial-mesenchymal interactions during development. Twelve human embryonic minor salivary glands were studied by immunohistochemistry to investigate the role of c-Met in human salivary gland development. Strong c-Met immunopositivity in the glands demonstrated that the molecule is involved in their development and suggested a role for the c-Met/HGF system in this process.

Epithelial-stromal interaction 1 (EPSTI1) substitutes for peritumoral fibroblasts in the tumor microenvironment

Tumor cells can activate stroma, yet the implication of this activation in terms of reciprocal induction of gene expression in tumor cells is poorly understood. Epithelial Stromal Interaction 1 (EPSTI1) is an interferon response gene originally isolated from heterotypic recombinant cultures of human breast cancer cells and activated breast myofibroblasts. Here we describe the first immunolocalization of EPSTI1 in normal and cancerous breast tissue, and we provide evidence for a role of this molecule in the regulation of tumor cell properties and epithelial-mesenchymal transition. In general, no EPSTI1 staining was observed in normal breast epithelial cells from reduction mammoplasties (n=25). However, in carcinomas, staining was positive in 22 of 40 biopsies and inversely correlated with the level of differentiation. To address the function of EPSTI1, we expressed EPSTI1 ectopically in one cell line and silenced endogenous EPSTI1 by RNA interference in another. Irrespective of the experimental approach, EPSTI1 expression led to an increase in tumorsphere formation-a property associated with breast stem/progenitor cells. Most remarkably, we show that EPSTI1, by conveying spread of tumor cells, can replace peritumoral activated fibroblasts in a tumor environment assay. These observations implicate EPSTI1 as a hitherto unappreciated regulator of tumor cell properties.

Selection criteria for c-Met-targeted therapies: emerging evidence for biomarkers

Extensive development of targeted therapies emphasize the critical need for biomarkers and major efforts have been engaged to identify screening, prognostic, stratification and therapy-monitoring markers. One of the challenges in translating preclinical studies into effective clinical therapies remains the accurate identification of a responsive subsets of patients. Studies on trastuzumab demonstrated that patient response could be specifically correlated with the amplification of the Her2 gene. However, for the EGF receptor, it has been more difficult to find the right stratification biomarker and recent data demonstrate that genetic alterations for the EGF receptor have to be considered. Taken together, these data underline the need for a deeper understanding of both targeted receptor and human disease to determine pathways that might be investigated during early clinical trials in order to define relevant biomarkers for patient selection. This article, dealing with the c-Met tyrosine kinase receptor, provides an overview of c-Met alterations observed in cancer and proposes approaches for stratification biomarker selection.

Safety, pharmacokinetics, and pharmacodynamics of AMG 102, a fully human hepatocyte growth factor-neutralizing monoclonal antibody, in a first-in-human study of patients with advanced solid tumors

PURPOSE

The aims were to assess the safety, pharmacokinetics, maximum tolerated dose, and antitumor activity of AMG 102, a fully human hepatocyte growth factor/scatter factor (HGF/SF)-neutralizing monoclonal antibody, in patients with solid tumors.

EXPERIMENTAL DESIGN

Patients (N = 40) with refractory advanced solid tumors were enrolled into six sequential dose-escalation cohorts (0.5, 1, 3, 5, 10, or 20 mg/kg AMG 102 i.v. every 2 weeks) and a dose-expansion cohort (20 mg/kg AMG 102 every 2 weeks). Safety, anti-AMG 102 antibody formation, pharmacokinetics, tumor response, and exploratory biomarkers were assessed.

RESULTS

AMG 102 was well tolerated up to the planned maximum dose of 20 mg/kg, and the maximum tolerated dose was not reached. Treatment-related adverse events were generally mild and included fatigue (13%), constipation (8%), nausea (8%), vomiting (5%), anorexia (5%), myalgia (5%), and hypertension (5%). Two patients experienced dose-limiting toxicities: one patient (0.5 mg/kg cohort) experienced grade 3 hypoxia and grade 3 dyspnea and one patient (1 mg/kg cohort) experienced grade 3 upper gastrointestinal hemorrhage. No anti-AMG 102 antibodies were detected, and AMG 102 had linear pharmacokinetics within the dose range investigated. Sixteen of 23 (70%) evaluable patients had a best response of stable disease with progression-free survival ranging from 7.9 to 40 weeks. Circulating levels of the biomarker HGF/SF (bound and unbound) increased in a dose-dependent manner, whereas soluble c-Met concentrations were generally similar across doses.

CONCLUSIONS

AMG 102 is safe and well tolerated, has a favorable pharmacokinetic profile, and will be further investigated as a monotherapy and in combination with other agents.

The discovery of hepatocyte growth factor (HGF) and its significance for cell biology, life sciences and clinical medicine

It has been more than 25 years since HGF was discovered as a mitogen of hepatocytes. HGF is produced by stromal cells, and stimulates epithelial cell proliferation, motility, morphogenesis and angiogenesis in various organs via tyrosine phosphorylation of its receptor, c-Met. In fetal stages, HGF-neutralization, or c-Met gene destruction, leads to hypoplasia of many organs, indicating that HGF signals are essential for organ development. Endogenous HGF is required for self-repair of injured livers, kidneys, lungs and so on. In addition, HGF exerts protective effects on epithelial and non-epithelial organs (including the heart and brain) via anti-apoptotic and anti-inflammatory signals. During organ diseases, plasma HGF levels significantly increased, while anti-HGF antibody infusion accelerated tissue destruction in rodents. Thus, endogenous HGF is required for minimization of diseases, while insufficient production of HGF leads to organ failure. This is the reason why HGF supplementation produces therapeutic outcomes under pathological conditions. Moreover, emerging studies delineated key roles of HGF during tumor metastasis, while HGF-antagonism leads to anti-tumor outcomes. Taken together, HGF-based molecules, including HGF-variants, HGF-fragments and c-Met-binders are available as regenerative or anti-tumor drugs. Molecular analysis of the HGF-c-Met system could provide bridges between basic biology and clinical medicine.

The growth-promoting effect of KGF on limbal epithelial cells is mediated by upregulation of ΔNp63α through the p38 pathway

Corneal epithelial stem cells are thought to reside in the limbus, the transition zoon between cornea and conjunctiva. Keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF) are two paracrine factors that regulate the proliferation, migration and differentiation of the limbal epithelial cells; however, the underlying mechanisms are still poorly understood. In an ex vivo limbal explant culture, we found that KGF is a more potent growth stimulator for the epithelial outgrowth than HGF. Immunofluorescence studies of the epithelial outgrowth from cells treated with HGF or KGF showed similar expression patterns of keratin-3 and keratin-14. Interestingly, p63 was highly expressed in KGF-treated limbal epithelial sheets but not in those treated with HGF. Kinase inhibitor studies showed that induction of ΔNp63α expression by KGF is mediated via the p38 pathway. The effect of KGF on limbal epithelial outgrowth was significantly reduced when endogenous ΔNp63α was suppressed, suggesting that KGF-induced limbal epithelial outgrowth is dependent on the expression of ΔNp63α. Our findings strongly suggest that limbal keratocytes regulate limbal epithelial cell growth and differentiation through a KGF paracrine loop, with ΔNp63α expression as one of the downstream targets.

A novel small molecule Met inhibitor, PF2362376, exhibits biological activity against osteosarcoma

The receptor tyrosine kinase Met is dysregulated in several human cancers including osteosarcoma (OSA) in which overexpression is a negative prognostic indicator and enforced Met expression in normal osteoblasts leads to genomic instability and malignant transformation. Met is also known to be inappropriately expressed in canine OSA tumour samples and cell lines. The purpose of this study was to evaluate the potential utility of an orally bioavailable small molecule Met inhibitor, PF2362376, against canine OSA cell lines as a prelude to future clinical work. PF2362376 inhibited phosphorylation of Met, Gab-1, Erk and Akt, but not of Src or STAT3. Furthermore, PF2362376 inhibited proliferation of canine OSA cell lines and induced cell death at biologically achievable concentrations. Last, activities associated with Met signalling including migration, invasion, branching morphogenesis and colony formation in soft agar were blocked by PF2362376. These studies support the notion that Met is a relevant target for therapeutic intervention in OSA.

Characterization, expression and function of c-Met in canine spontaneous cancers

Aberrant expression of the proto-oncogene c-Met has been noted in a variety of human cancers. To better define the potential role of Met dysregulation in canine cancer, the canine Met, hepatocyte growth factor (HGF) and HGF activator were cloned. Inappropriate expression of Met was present in canine tumour cell lines derived from a wide variety of cancers. Furthermore, both HGF and HGF activator were also expressed in several of these cell lines, providing evidence of a possible autocrine loop of Met activation. Stimulation of tumour cell lines with recombinant human HGF induced Met autophosphorylation, as well as activation of the downstream signalling elements Gab-1, Akt and Erk1/2. Scattering of tumour cells and migration across a defect occurred in response to HGF stimulation. The Met inhibitor PHA665752 blocked both HGF-induced phosphorylation of canine Met and HGF-mediated cell cycling, scattering and migration. These studies provide evidence that Met dysregulation may play a role in the biology of canine cancer and lay the groundwork for future studies employing Met inhibitors.

Identification of a bone marrow-derived mesenchymal progenitor cell subset that can contribute to the gastric epithelium

Recent studies with Helicobacter-infected mice have shown that bone marrow-derived cells can repopulate the gastric epithelium and progress to cancer. However, it has not been established which cellular subset can potentially contribute to the epithelium. The aim of this study was to investigate the ability of bone marrow-derived mesenchymal stem cells (MSCs) that express cytokeratin 19 (K19) to contribute to the gastric epithelium. MSCs cultures were established from whole bone marrow and expression of K19 was detected in a minority (1 of 13) of clones by real-time PCR and immunostaining. Transfection of a K19-green fluorescent protein (GFP) vector and isolation of GFP-expressing colonies generated high K19-expressing MSC clones (K19GFPMSC). Incubation of MSCs with gastric tissue extract markedly induced mRNA expression of gastric phenotypic markers and was observed to a greater extent in K19GFPMSCs compared with parental MSCs and mock transfectants. Both K19GFPMSCs and GFP-labeled control MSCs gave rise to gastric epithelial cells after injection into the murine stomach. In addition, after blastocyst injections, K19GFPMSCs gave rise to GFP-positive gastric epithelial cells in all 13 pups, whereas only 3 of 10 offspring showed GFP-positive gastric epithelial cells after injection of GFP-labeled control MSCs. Although K19 expression could not be detected in murine whole bone marrow, H. felis infection increased K19-expressing MSCs in the circulation. Taken together, our results show that bone marrow-derived MSCs can contribute to the gastric epithelium. The K19-positive MSC fraction that is induced by chronic H. felis infection appears to be the important subset in this process.

Repeated hepatocyte growth factor neutralizing antibody treatment leads to HGF/SF unresponsiveness in human glioblastoma multiforme cells

The purpose of this work is to seek putative markers for multi-targeted therapeutic treatment of human glioblastoma. We previously developed an anti-HGF neutralizing antibody cocktail Amix that inhibits human glioblastoma growth in mouse xenograft models. When these treated tumors were re-injected into nude mice and treatment with the neutralizing antibody cocktail plus heparin was repeated, the growth of the twice-treated tumors became HGF-independent, suggesting a possible switch in dominant signaling pathways. Microarray of the tumor cells revealed a number of genes elevated in the twice-treated tumor cells relative to untreated control tumors, including BAI1, CASP8, IL8, IGF1, TGFB1 and TNF. Our analyses provide a series of putative markers for additional evaluation in treating glioblastoma. Multi-targeted therapeutic approach might be a better solution for treating this disease.

Human chorionic gonadotropin (hCG) prevents the transformed phenotypes induced by 17 beta-estradiol in human breast epithelial cells

Human chorionic gonadotropin (hCG), a hormone produced during pregnancy, can elicit life-long refractoriness to carcinogenesis by differentiation of the breast epithelium. Human breast epithelial cells MCF-10F form tubules in collagen, mimicking the normal ductules. We have shown that 17 beta-estradiol (E2) alter the ductulogenic pattern of these cells. The effect of the recombinant hCG (rhCG) in vitro was evaluated on the transformation of MCF-10F induced by E2. MCF-10F cells were treated with 70 nM E2 alone or in combination with 50 IU/ml rhCG during 2 weeks, while the controls were treated with DMSO (the solvent in which E2 was dissolved) or rhCG alone. At the end of treatment, the cells were plated in type I collagen matrix (3D-cultures) for detecting 2 main phenotypes of cell transformation, namely the loss of ductulogenic capacity and the formation of solid masses. Although E2 significantly increased solid mass formation, this effect was prevented when MCF-10F cells were treated with E2 in combination with rhCG. Furthermore, E2 increased the main duct width (p < 0.001), and caused a disruption of the luminal architecture, whereas rhCG increased the length of the tubules (p < 0.001) and produced tertiary branching. In conclusion, rhCG was able to abrogate the transforming abilities of estradiol, and had the differentiating property by increasing the branching of the tubules formed by breast epithelial cells in collagen. These results further support our hypothesis, known as the terminal differentiation hypothesis of breast cancer prevention, that predicts that hCG treatment results in protection from tumorigenic changes by the loss of susceptible stem cells 1 through a differentiation to refractory stem cells 2 and increase differentiation of the mammary gland.

Bone marrow stromal cells attenuate lung injury in a murine model of neonatal chronic lung disease

RATIONALE

Neonatal chronic lung disease, known as bronchopulmonary dysplasia (BPD), remains a serious complication of prematurity despite advances in the treatment of extremely low birth weight infants.

OBJECTIVES

Given the reported protective actions of bone marrow stromal cells (BMSCs; mesenchymal stem cells) in models of lung and cardiovascular injury, we tested their therapeutic potential in a murine model of BPD.

METHODS

Neonatal mice exposed to hyperoxia (75% O(2)) were injected intravenously on Day 4 with either BMSCs or BMSC-conditioned media (CM) and assessed on Day 14 for lung morphometry, vascular changes associated with pulmonary hypertension, and lung cytokine profile.

MEASUREMENTS AND MAIN RESULTS

Injection of BMSCs but not pulmonary artery smooth muscle cells (PASMCs) reduced alveolar loss and lung inflammation, and prevented pulmonary hypertension. Although more donor BMSCs engrafted in hyperoxic lungs compared with normoxic controls, the overall low numbers suggest protective mechanisms other than direct tissue repair. Injection of BMSC-CM had a more pronounced effect than BMSCs, preventing both vessel remodeling and alveolar injury. Treated animals had normal alveolar numbers at Day 14 of hyperoxia and a drastically reduced lung neutrophil and macrophage accumulation compared with PASMC-CM-treated controls. Macrophage stimulating factor 1 and osteopontin, both present at high levels in BMSC-CM, may be involved in this immunomodulation.

CONCLUSIONS

BMSCs act in a paracrine manner via the release of immunomodulatory factors to ameliorate the parenchymal and vascular injury of BPD in vivo. Our study suggests that BMSCs and factor(s) they secrete offer new therapeutic approaches for lung diseases currently lacking effective treatment.

Translational research to identify clinical applications of hepatocyte growth factor

Hepatocyte growth factor (HGF), originally purified from the plasma of patients with fulminant hepatic failure, has been shown to carry out various physiological functions. HGF not only stimulates liver regeneration, but also acts as an antiapoptotic factor in in vivo experimental models. Therefore, HGF is a promising therapeutic agent for the treatment of fatal liver diseases, including fulminant hepatic failure. After performing a number of preclinical tests, our group began an investigator-initiated registered phase I/II clinical trial of patients with fulminant hepatic failure to examine the safety and clinical efficacy of recombinant human HGF. In this article, we will discuss the basic research results as well as the translational research that underpins current attempts to use HGF in various clinical settings.

Stability of faecal hepatocyte growth factor determination

In order to evaluate the accuracy and reproducibility of determination of hepatocyte growth factor (HGF) levels in faeces, the stability of HGF in samples processed in different ways was investigated. An ELISA method was used for determination of HGF concentrations. Faeces samples from healthy controls and patients with infectious diarrhoea were studied. It was found that faeces HGF concentration remained stable irrespective of whether samples were freeze-thawed several times, kept for 6, 12 or 24 h at room temperature or refrigerated for 6, 12, 24 or 36 h; the levels of HGF did not change significantly when samples were freeze-dried. Adding protease inhibitor to the faeces samples did not affect the HGF levels. There were no significant differences between HGF levels using phosphate buffered saline (PBS) (pH 7.4) or NaCL as buffer, but it was observed that levels of HGF were significantly lower in the samples that were diluted in distilled water. Although both HGF and albumin through various mechanisms may increase in faeces during infectious diarrhoea, there was no significant correlation between faeces HGF levels and albumin levels, which might indicate local production of HGF in the bowel in response to infection. It is concluded that determination of faeces HGF levels is feasible with a high degree of stability. Increased HGF levels in faeces might represent a local production of HGF during bowel injury and might be of use as a diagnostic and monitoring assay.

Hepatocyte growth factor (HGF) in patients with acute brucellosis

In this prospective study, we investigated the serum levels of hepatocyte growth factor (HGF) and C-reactive protein (CRP) before and after the treatment of patients with acute brucellosis. The study comprised 58 patients with acute brucellosis and 30 healthy volunteers. Pre-treatment serum HGF levels of 58 patients with acute brucellosis (1548.6 +/- 220.1) were significantly higher than levels of the control group (401.4 +/- 69.7) (p < 0.001). Serum levels of HGF and CRP significantly decreased at the end of the treatment period (p < 0.001). Post treatment, levels did not differ from those of the control group (p > 0.05). Serum HGF levels of patients with acute brucellosis correlated to CRP and ALT levels (r: 0.922, 0.752; p < 0.001, respectively). Our findings suggest that serum HGF levels may be used as a supplementary marker to evaluate the effectiveness of the treatment in patients with acute brucellosis.

The lectin KM+ induces corneal epithelial wound healing in rabbits

Neutrophil influx is essential for corneal regeneration (Gan et al. 1999). KM+, a lectin from Artocarpus integrifolia, induces neutrophil migration (Santos-de-Oliveira et al. 1994). This study aims at investigating a possible effect of KM+ on corneal regeneration in rabbits. A 6.0-mm diameter area of debridement was created on the cornea of both eyes by mechanical scraping. The experimental eyes received drops of KM+ (2.5 microg/ml) every 2 h. The control eyes received buffer. The epithelial wounded areas of the lectin-treated and untreated eyes were stained with fluorescein, photographed and measured. The animals were killed 12 h (group 1, n = 5), 24 h (group 2, n = 10) and 48 h (group 3, n = 5) after the scraping. The corneas were analysed histologically (haematoxylin and eosin and immunostaining for proliferation cell nuclear antigen, p63, vascular endothelial growth factor, c-Met and laminin). No significant differences were found at the epithelial gap between treated and control eyes in the group 1. However, the number of neutrophils in the wounded area was significantly higher in treated eyes in this group. Three control and seven treated eyes were healed completely and only rare neutrophils persisted in the corneal stroma in group 2. No morphological distinction was observed between treated and control eyes in group 3. In treated corneas of group 2, there was an increase in immunostaining of factors involved in corneal healing compared to controls. Thus, topical application of KM+ may facilitate corneal epithelial wound healing in rabbits by means of a mechanism that involves increased influx of neutrophils into the wounded area induced by the lectin.

Recent perspectives on the genetic background of neural tube defects with special regard to iniencephaly

Iniencephaly is a rare and mostly lethal type of neural tube defect. The pattern of inheritance of this group of malformations is multifactorial, rendering the identification of the underlying causes. Numerous studies have been conducted to elucidate the genetic basis of human neurulation. Essential signaling pathways of the development of the CNS include the planar cell polarity pathway, which is important for the initiation of neural tube closure, as well as the sonic hedgehog pathway, which regulates the neural plate bending. Genes influencing the different stages of neurulation have been investigated for their eventual role in the development of these malformations. Among the environmental factors, folic acid seems to be the most important modifier of the risk of human neural tube defects. Genes of the folate metabolism pathways have also been investigated to identify mutations resulting in increased risk of neural tube defects. In this review we have attempted to summarize the knowledge on iniencephaly and neural tube defects, with special regard to genetic factors of the etiology.

Met and the epidermal growth factor receptor act cooperatively to regulate final nephron number and maintain collecting duct morphology

Ureteric bud (UB) branching during kidney development determines the final number of nephrons. Although hepatocyte growth factor and its receptor Met have been shown to stimulate branching morphogenesis in explanted embryonic kidneys, loss of Met expression is lethal during early embryogenesis without obvious kidney abnormalities. Met(fl/fl);HoxB7-Cre mice, which lack Met expression selectively in the UB, were generated and found to have a reduction in final nephron number. These mice have increased Egf receptor expression in both the embryonic and adult kidney, and exogenous Egf can partially rescue the branching defect seen in kidney explants. Met(fl/fl);HoxB7-Cre;wa-2/wa-2 mice, which lack normal Egfr and Met signaling, exhibit small kidneys with a marked decrease in UB branching at E14.5 as well as a reduction in final glomerular number. These mice developed progressive interstitial fibrosis surrounding collecting ducts with kidney failure and death by 3-4 weeks of age. Thus, in support of previous in vitro findings, Met and the Egf receptor can act cooperatively to regulate UB branching and mediate maintenance of the normal adult collecting duct.

Coordinate integrin and c-Met signaling regulate Wnt gene expression during epithelial morphogenesis

Integrin receptors for the extracellular matrix and receptor tyrosine kinase growth factor receptors represent two of the major families of receptors that transduce into cells information about the surrounding environment. Wnt proteins are a major family of signaling molecules that regulate morphogenetic events. There is presently little understanding of how the expression of Wnt genes themselves is regulated. In this study, we demonstrate that alpha3beta1 integrin, a major laminin receptor involved in the development of the kidney, and c-Met, the receptor for hepatocyte growth factor, signal coordinately to regulate the expression of Wnt7b in the mouse. Wnt signals in turn appear to regulate epithelial cell survival in the papilla of the developing kidney, allowing for the elongation of epithelial tubules to form a mature papilla. Together, these results demonstrate how signals from integrins and growth factor receptors can be integrated to regulate the expression of an important family of signaling molecules so as to regulate morphogenetic events.

Hgf/c-met expression and functional analysis during zebrafish embryogenesis

Hepatocyte growth factor (HGF) and its receptor tyrosine kinase Met are linked to several processes underlying vertebrate development and cancer progression. Here, we characterized the expression of zebrafish c-met, hgf1, and hgf2 from cleavage stages through organogenesis and initiated an analysis of Met signaling. We identified c-met as a marker of endoderm and demonstrated that its expression can be activated downstream of Nodal. Injection of c-met mRNA drives expression of the endodermal gene sox17. During gastrulation, hgf1 transcripts are visible in mesendodermal cells along the midline. Later, c-met is expressed in kidney, islet2-positive neurons, and liver. We show that hgf1 is transcribed during gastrulation while hgf1 and hgf2 are detectable in pharyngeal arches and swim bladder. Similar to mouse, knockdown of zebrafish Met reduces liver size. Our results suggest a role for Met during endoderm specification and indicate that mechanisms of liver development are conserved between mammals and bony fish.

Hepatocyte growth factor induces gefitinib resistance of lung adenocarcinoma with epidermal growth factor receptor-activating mutations

Lung cancer with epidermal growth factor receptor (EGFR)-activating mutations responds favorably to the EGFR tyrosine kinase inhibitors gefitinib and erlotinib. However, 25% to 30% of patients with EGFR-activating mutations show intrinsic resistance, and the responders invariably acquire resistance to gefitinib. Here, we showed that hepatocyte growth factor (HGF), a ligand of MET oncoprotein, induces gefitinib resistance of lung adenocarcinoma cells with EGFR-activating mutations by restoring the phosphatidylinositol 3-kinase/Akt signaling pathway via phosphorylation of MET, but not EGFR or ErbB3. Strong immunoreactivity for HGF in cancer cells was detected in lung adenocarcinoma patients harboring EGFR-activating mutations, but no T790M mutation or MET amplification, who showed intrinsic or acquired resistance to gefitinib. The findings indicate that HGF-mediated MET activation is a novel mechanism of gefitinib resistance in lung adenocarcinoma with EGFR-activating mutations. Therefore, inhibition of HGF-MET signaling may be a considerable strategy for more successful treatment with gefitinib.

cAMP-dependent chloride secretion mediates tubule enlargement and cyst formation by cultured mammalian collecting duct cells

Polycystic kidney diseases result from disruption of the genetically defined program that controls the size and geometry of renal tubules. Cysts which frequently arise from the collecting duct (CD) result from cell proliferation and fluid secretion. From mCCD(cl1) cells, a differentiated mouse CD cell line, we isolated a clonal subpopulation (mCCD-N21) that retains morphogenetic capacity. When grown in three-dimensional gels, mCCD-N21 cells formed highly organized tubular structures consisting of a palisade of polarized epithelial cells surrounding a cylindrical lumen. Subsequent addition of cAMP-elevating agents (forskolin or cholera toxin) or of membrane-permeable cAMP analogs (CPT-cAMP) resulted in rapid and progressive dilatation of existing tubules, leading to the formation of cystlike structures. When grown on filters, mCCD-N21 cells exhibited a high transepithelial resistance as well as aldosterone- and/or vasopressin-induced amiloride-sensitive and -insensitive current. The latter was in part inhibited by Na(+)-K(+)-2Cl(-) cotransporter (bumetanide) and chloride channel (NPPB) inhibitors. Real-time PCR analysis confirmed the expression of NKCC1, the ubiquitous Na(+)-K(+)-2Cl(-) cotransporter and cystic fibrosis transmembrane regulator (CFTR) in mCCD-N21 cells. Tubule enlargement and cyst formation were prevented by inhibitors of Na(+)-K(+)-2Cl(-) cotransporters (bumetanide or ethacrynic acid) or CFTR (NPPB or CFTR inhibitor-172). These results further support the notion that cAMP signaling plays a key role in renal cyst formation, at least in part by promoting chloride-driven fluid secretion. This new in vitro model of tubule-to-cyst conversion affords a unique opportunity for investigating the molecular mechanisms that govern the architecture of epithelial tubes, as well as for dissecting the pathophysiological processes underlying cystic kidney diseases.

Transfection efficiency of TDL compound in HUVEC enhanced by ultrasound-targeted microbubble destruction

The aim of the present study was to explore the gene transfection efficiency of Tat peptide/plasmid DNA/ liposome (TDL) compound combined with ultrasound-targeted microbubble destruction (UTMD) in human umbilical vein endothelial cell (HUVEC). Tat peptide, plasmid DNA (pIRES2-EGFP-HGF) and Lipofectamine 2000 were used to prepare the TDL compound. Microbubbles were prepared using mechanic vibration. The expression of the report gene enhanced green fluorescent protein (EGFP) was observed using fluorescent microscopy and flow cytometry. The viability of HUVEC was measured by MTT assay. mRNA and protein of HGF was analyzed by reverse transcription-polymerase chain reaction and Western Blot. The intensity of green fluorescence and the gene transfection efficiency of TDL compound + microbubbles + ultrasound group were higher than those of other groups, and no significantly different viability was found between TDL compound + microbubbles + ultrasound group and the other groups. The HGF mRNA and HGF protein of TDL compound + microbubbles + ultrasound group were higher than those of other groups. Our finding demonstrated that UTMD could enhance the transfection efficiency of TDL compound without obvious effects on the cell viability of HUVEC, suggesting that the combination of UTMD and TDL compound might be a useful tool for the gene therapy of ischemic heart disease.

Differences in the temporal expression of regulatory growth factors during choroidal neovascular development

Although the roles of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and hepatocyte growth factor (HGF) in pathologic neovascularization have been well characterized in certain tissues, their particular functions and expression patterns in choroidal neovascularization (CNV) have not been clearly established. After localized laser trauma to Bruch's membrane to induce CNV development, the temporal changes in mRNA and protein expression of these 3 cytokines were documented and compared histologically to areas of immunofluorescence, the proliferation of endothelial cells, neovascular development, and temporal changes in vascular permeability. Changes in mRNA and protein levels of bFGF and HGF occurred quickly and reached peak expression within hours. This activity corresponded in time to intense and localized immunofluorescence for these cytokines within the choriocapillaris within laser lesion sites. During this same initial time period, mRNA upregulation of VEGF occurred, primarily within the neural retina and this expression corresponded to intense immunolabeling of Müller cells immediately adjacent to the lesion sites. By 3 days after lasering, increased VEGF(164) protein expression was measurable, whereas early neovascular development histologically corresponded to HGF and bFGF mRNA expansion into the developing choroidal neovascular membrane (CNVM). At 7 days, CNV expansion, maturation, and increased vascular permeability corresponded to peak VEGF mRNA and protein expression and to immunofluorescence of the CNVM. Differences also occurred in the expression of precursor and activated isoforms of these cytokines in the retinal pigment epithelium/choroid as compared to those in the retina. These molecular and immunocytochemical results suggest that bFGF and HGF may be important as initial regulators neovascularization in this CNV model; whereas VEGF may be important during later phases of angiogenesis and neovascular hyperpermeability.

HGF and MET mutations in primary and secondary lymphedema

BACKGROUND

Lymphedema is the abnormal accumulation of protein-rich fluid in the interstitial space. Primary lymphedema is a rare genetic condition with both autosomal dominant and autosomal recessive modes of inheritance. Three genes, FLT4 (VEGFR3), FOXC2, and SOX18 cause varying forms of primary lymphedema. In industrialized countries, secondary lymphedema is usually associated with cancer therapy and/or trauma. Recent observations suggested that hepatocyte growth factor/high affinity hepatocyte growth factor receptor (HGF/MET) were new candidate lymphedema genes.

METHODS AND RESULTS

The coding exons and flanking regions of HGF and MET were directly sequenced in 145 lymphedema probands, 59 unrelated women with secondary lymphedema following treatment for breast cancer, 21 individual patients with lymphedema and intestinal lymphangiectasia, and at least 159 unrelated ethnic matched control individuals. Mutations leading to truncation or missense changes in evolutionarily conserved residues of HGF and MET were identified. These mutations were not polymorphic in control individuals.

CONCLUSIONS

The identification of HGF/MET mutations in primary lymphedema, lymphedema/lymphangiectasia, and breast cancer-associated secondary lymphedema suggests that the HGF/MET pathway is causal or alters susceptibility for a broad range of lymphedema phenotypes. The HGF/MET pathway provides a new target for the prevention and/or treatment of lymphedema.

The PI 3-kinase and mTOR signaling pathways are important modulators of epithelial tubule formation

Using MDCK cells as a model system, evidence is presented demonstrating that the signaling pathways mammalian target of rapamycin (mTOR) and phosphoinositide 3-kinase (PI 3-kinase) play important roles in the regulation of epithelial tubule formation. Incubation of cells with collagen gel overlays induced early (4-8 h) reorganization of cells (epithelial remodeling) into three-dimensional multicellular tubular structures over 24 h. An MDCK cell line stably expressing the PH domain of Akt, a PI 3-kinase downstream effector, coupled to green fluorescent protein (GFP-Akt-PH) was used to determine the distribution of phosphatidyl inositol-3,4,5-P(3) (PIP(3)), a product of PI 3-kinase. GFP-Akt-PH was associated with lateral membranes in control cells. After incubation with collagen gel overlays, GFP-Akt-PH redistributed into the lamellipodia of migrating cells suggesting that PIP(3) plays a role in epithelial remodeling. Using the small molecule inhibitor LY-294002 that inhibits both mTOR and PI 3-kinase, we demonstrated that kinase activity was required for epithelial remodeling, disruption of cell junctions and subsequent modulation of tubule formation. Since the mTOR signaling pathway is downstream of PI 3-kinase, the effects of rapamycin, a specific mTOR inhibitor, on tubule formation were assessed. Rapamycin did not affect epithelial remodeling or GFP-Akt-PH redistribution but inhibited elongated tubule formation that occurred later (24 h) in morphogenesis. These results were further supported by using RNA interference to down-regulate mTOR and inhibit tubule formation. Our studies demonstrate that PI 3-kinase regulates early epithelial remodeling stages while mTOR modulates latter stages of tubule development.

Induction of hepatocyte growth factor activator gene expression under hypoxia activates the hepatocyte growth factor/c-Met system via hypoxia inducible factor-1 in pancreatic cancer

Hepatocyte growth facor activator (HGFA) is a serine protease that converts hepatocyte growth factor (HGF) into its active form. Our previous study demonstrated that tumor-stromal interaction under hypoxia augments the aggressive invasive features of pancreatic cancer line PK8 through activated HGF/c-Met signaling. The present study investigated whether or not hypoxia increases HGFA expression in PK8 cells and promotes the processing of HGF, and leads to c-Met activation. Moreover, HGFA promoter assays were performed to define whether hypoxia inducible factor-1 alpha (HIF-1alpha) directly activates the HGFA promoter in a hypoxia-dependent fashion. As a result, hypoxia induced the HGFA mRNA and protein expression in PK8 and the elevation under hypoxia was inhibited by the transfection of HIF-1alpha siRNA, thus indicating HIF-1alpha-dependent induction of HGFA. The transfection of siRNA against HGFA to PK8 cells suppressed the conversion to the active HGF, which is secreted from fibroblast MRC5. Furthermore, the phosphorylation of c-Met and cancer invasion of PK8 cells were decreased by the transfection of HGFA siRNA under hypoxia. Using the luciferase reporter system, HIF-1alpha was shown to transactivate the HGFA promoter under hypoxia. These experiments demonstrated for the first time that HGFA is a novel HIF-1 target gene. Under hypoxia, HGFA might be overexpressed and secreted from pancreatic cancer cells, which contributes to accelerate processing of HGF from fibroblast, resulting in the activation of the c-Met pathway. HGF/HGFA/c-Met recruited between cancer-stromal fibroblasts is activated under hypoxic conditions and therefore might play a central role in the aggressive invasion of pancreatic cancer.

Requirement of kinesin-mediated membrane transport of WAVE2 along microtubules for lamellipodia formation promoted by hepatocyte growth factor

Lamellipodia formation necessary for epithelial cell migration and invasion is accomplished by rearrangement of the actin cytoskeleton at the leading edge through membrane transport of WAVE2. However, how WAVE2 is transported to the cell periphery where lamellipodia are formed remains to be established. We report here that hepatocyte growth factor (HGF) promoted lamellipodia formation and intracellular transport of WAVE2 to the cell periphery, depending on Rac1 activity, in MDA-MB-231 human breast cancer cells. Immunoblot analyses indicating the coimmunoprecipitation of WAVE2 with kinesin heavy chain KIF5B, one of the motor proteins, and IQGAP1 suggest that KIF5B and IQGAP1 formed a complex with WAVE2 in serum-starved cells and increased in their amount after HGF stimulation. Both downregulation of KIF5B by the small interfering RNA and depolymerization of microtubules with nocodazole abrogated the HGF-induced lamellipodia formation and WAVE2 transport. Therefore, we propose here that the promotion of lamellipodia formation by HGF in MDA-MB-231 cells is Rac1-dependent and requires KIF5B-mediated transport of WAVE2 and IQGAP1 to the cell periphery along microtubules.

The Met tyrosine kinase receptor in development and cancer

Met is a tyrosine kinase receptor, encoded by an oncogene, whose crucial role has been elucidated during the last two decades. The complex biological program triggered by Met has been dissected and its biological relevance in both physiology and pathology has been proven. Met supports a morphogenetic program, known as invasive growth, taking place both during embryogenesis and adulthood. In tumors Met is often aberrantly activated, giving rise to the pathological counterpart of the invasive growth program: cancer progression towards metastasis. Several approaches have been recently developed to interfere with the tumorigenic and metastatic processes triggered by Met.

The microenvironmental determinants for kidney epithelial cyst morphogenesis

Although epithelial morphogenesis is tightly controlled by intrinsic genetic programs, the microenvironment in which epithelial cells proliferate and differentiate also contributes to the morphogenetic process. The roles of the physical microenvironment in epithelial morphogenesis, however, have not been well dissected. In this study, we assessed the impact of the microenvironment on epithelial cyst formation, which often marks the beginning or end step of morphogenesis of epithelial tissues and the pathological characteristic of some diseases. Previous studies have demonstrated that Madin-Darby canine kidney (MDCK) epithelial cells form cysts when grown in a three-dimensional (3D) extracellullar matrix (ECM) environment. We have now further demonstrated that the presence of ECM in the 3D scaffold is required for the formation of properly polarized cysts. Also, we have found that the full interface of epithelial cells with the ECM environment (in-3D) is not essential for cyst formation, since partial contact (on-3D) is sufficient to induce cystogenesis. In addition, we have defined the minimal ECM environment or the physical threshold for cystogenesis under the on-3D condition. Only above the threshold can the morphological cues from the ECM environment induce cyst formation. Moreover, cyst formation under the on-3D condition described in this study defines a novel and more feasible model to analyze in vitro morphogenesis. Finally, we have found that, during cystogenesis, MDCK cells generate basal microprotrusions and produce vesicle-like structures to the basal extracellular space, which are specific to and correlated with cyst formation. For the first time, we have systematically and quantitatively elucidated the microenvironmental determinants for epithelial cystogenesis.

Depletion of apical transport proteins perturbs epithelial cyst formation and ciliogenesis

Epithelial cells are vital for maintaining the complex architecture and functions of organs in the body. Directed by cues from the extracellular matrix, cells polarize their surface into apical and basolateral domains, and connect by extensive cell-cell junctions to form tightly vowen epithelial layers. In fully polarized cells, primary cilia project from the apical surface. Madin-Darby canine kidney (MDCK) cells provide a model to study organization of cells as monolayers and also in 3D in cysts. In this study retrovirus-mediated RNA interference (RNAi) was used to generate a series of knockdowns (KDs) for proteins implicated in apical transport: annexin-13, caveolin-1, galectin-3, syntaxin-3, syntaxin-2 and VIP17 and/or MAL. Cyst cultures were then employed to study the effects of these KDs on epithelial morphogenesis. Depletion of these proteins by RNAi stalled the development of the apical lumen in cysts and resulted in impaired ciliogenesis. The most severe ciliary defects were observed in annexin-13 and syntaxin-3 KD cysts. Although the phenotypes demonstrate the robustness of the formation of the polarized membrane domains, they indicate the important role of apical membrane biogenesis in epithelial organization.

Activin A: autocrine regulator of kidney development and repair

The research described in this review suggests a novel and important role for activin A in the developmental and repair processes of the kidney (Table 1). The results obtained in these studies indicate that activin A is a negative regulator of kidney development and plays an essential part in kidney diseases, such as acute renal failure or renal fibrosis. It is also possible that activin A is a key player in the pathophysiological processes of other kidney diseases, such as congenital urogenital abnormalities, renal cystic disease and renal cell carcinoma. Activin A is thus a potential target for therapeutic interventions in kidney diseases. To address this issue, more detailed analysis on the regulation of activin production, modulation of activin activity and activin target genes is required.

Bypassing cellular EGF receptor dependence through epithelial-to-mesenchymal-like transitions

Over 90% of all cancers are carcinomas, malignancies derived from cells of epithelial origin. As carcinomas progress, these tumors may lose epithelial morphology and acquire mesenchymal characteristics which contribute to metastatic potential. An epithelial-to-mesenchymal transition (EMT) similar to the process critical for embryonic development is thought to be an important mechanism for promoting cancer invasion and metastasis. Epithelial-to-mesenchymal transitions have been induced in vitro by transient or unregulated activation of receptor tyrosine kinase signaling pathways, oncogene signaling and disruption of homotypic cell adhesion. These cellular models attempt to mimic the complexity of human carcinomas which respond to autocrine and paracrine signals from both the tumor and its microenvironment. Activation of the epidermal growth factor receptor (EGFR) has been implicated in the neoplastic transformation of solid tumors and overexpression of EGFR has been shown to correlate with poor survival. Notably, epithelial tumor cells have been shown to be significantly more sensitive to EGFR inhibitors than tumor cells which have undergone an EMT-like transition and acquired mesenchymal characteristics, including non-small cell lung (NSCLC), head and neck (HN), bladder, colorectal, pancreas and breast carcinomas. EGFR blockade has also been shown to inhibit cellular migration, suggesting a role for EGFR inhibitors in the control of metastasis. The interaction between EGFR and the multiple signaling nodes which regulate EMT suggest that the combination of an EGFR inhibitor and other molecular targeted agents may offer a novel approach to controlling metastasis.

Regulation of lamellipodia formation and cell invasion by CLIP-170 in invasive human breast cancer cells

Lamellipodia formation necessary for cell invasion is regulated by Rac1. We report here that lamellipodia formation and three-dimensional invasion were significantly promoted by HGF and serum, respectively, in invasive human breast cancer cells. Rac1 formed a complex with CLIP-170, IQGAP1, and kinesin in serum-starved cells, and stimulation of the cells with HGF and serum caused the partial release of IQGAP1 and kinesin from Rac1-CLIP-170 complex. The HGF-induced release of the proteins and promotion of lamellipodia formation were inhibited by an inhibitor of PI3K. Moreover, downregulation of CLIP-170 by siRNA released IQGAP1 and kinesin from Rac1 and promoted lamellipodia formation and invasion, independent of HGF and serum. The results suggest that promotion of lamellipodia formation and invasion by HGF or serum requires PI3K-dependent release of IQGAP1 and kinesin from Rac1-CLIP-170 complex and that CLIP-170 prevents cells from the extracellular stimulus-independent lamellipodia formation and invasion by tethering IQGAP1 and kinesin to Rac1.

Differential expression of E-cadherin and cytokeratin 19 and net proliferative rate of gingival keratinocytes in oral epithelium in periodontal health and disease

BACKGROUND

The effects of periodontal disease on the oral gingival epithelium (OGE) have not been documented fully because they may not be as dramatic as those seen on the junctional epithelium. The aim of this study was to estimate the changes occurring in the OGE with respect to its proliferation and E-cadherin and cytokeratin 19 (K19) expression during pocket formation.

METHODS

Gingival samples were collected from 17 periodontally healthy subjects and 18 subjects with chronic periodontitis. K19 and E-cadherin levels were analyzed immunohistochemically. The net proliferative rate was calculated as the difference between the proliferative rate and the apoptotic rate as determined by immunohistochemical analysis of Ki-67 and p53, respectively.

RESULTS

There was a significant increase in the net proliferative rate of the OGE during pocket formation (periodontitis group, 220.90+/-46.85; healthy group, 107.60+/-25.86; P<0.001). There was a significant reduction in E-cadherin expression (periodontitis group, 0.837+/-0.428; healthy group, 1.846+/-0.555) and a significant increase in K19 expression during pocket formation (periodontitis group, 1.45+/-0.686; healthy group, 0.533+/-0.410).

CONCLUSION

OGE appears to undergo significant changes in proliferation and differentiation during pocket formation that do not seem to be restricted to proteolytic destruction by the invading microorganisms.

Hepatocyte growth factor suppresses proinflammatory NFkappaB activation through GSK3beta inactivation in renal tubular epithelial cells

Activation of NFkappaB is a fundamental cellular event central to all inflammatory diseases. Hepatocyte growth factor (HGF) ameliorates both acute and chronic inflammation in a multitude of organ systems through modulating NFkappaB activity; nevertheless, the exact molecular mechanism remains uncertain. Here we report that HGF through inactivation of GSK3beta suppresses NFkappaB p65 phosphorylation specifically at position Ser-468. The Ser-468 of RelA/p65 situates in a GSK3beta consensus motif and could be directly phosphorylated by GSK3beta both in vivo and in vitro, signifying Ser-468 of RelA/p65 as a putative substrate for GSK3beta. In addition, the C terminus of RelA/p65 harbors a highly conserved domain homologue of the consensus docking sequence for GSK3beta. Moreover, this domain was required for efficient phosphorylation of Ser-468 and was indispensable for the physical interaction between RelA/p65 and GSK3beta. HGF substantially intercepted this interaction by inactivating GSK3beta. Functionally, phosphorylation of Ser-468 of RelA/p65 was required for the induced expression of a particular subset of proinflammatory NFkappaB-dependent genes. Diminished phosphorylation at Ser-468 by HGF resulted in a gene-specific inhibition of these genes' expression. The action of HGF on proinflammatory NFkappaB activation was consistently mimicked by a selective GSK3beta inhibitor or GSK3beta knockdown by RNA interference but largely abrogated in cells expressing the mutant uninhibitable GSK3beta. Collectively, our findings suggest that HGF has a potent suppressive effect on NFkappaB activation, which is mediated by GSK3beta, an important signaling transducer controlling RelA/p65 phosphorylation specificity and directing the transcription of selective proinflammatory cytokines implicated in inflammatory kidney disease.

Serum hepatocyte growth factor as a marker of tumor activity in head and neck squamous cell carcinoma

Hepatocyte growth factor (HGF) has previously been reported to be elevated in the serum of patients with malignancy, including breast, colorectal and gastric cancers. Here, we evaluated the correlation between serum HGF and the progression of head and neck squamous cell carcinoma (HNSCC). The mean serum HGF levels in 71 healthy control subjects, 78 patients with primary HNSCC, and eight patients with recurrent HNSCC were 0.538+/-0.163, 0.701+/-0.252, and 0.925+/-0.349ng/ml, respectively. The increase in the HGF level was significantly correlated with tumor stage progression. The HGF level had decreased to normal at 1 month after curative resection of the tumors. During follow-up for several months, the HGF level significantly increased in recurrent HNSCC patients, whereas there was no increase in nonrecurrent patients. Our data suggest that serum HGF is significantly corrected with tumor progression and may be a strong predictor of recurrence in HNSCC.

Hepatocyte Growth Factor Establishes Autocrine and Paracrine Feedback Loops for the Protection of Skin Cells after UV Irradiation

Hepatocyte growth factor (HGF) is a multifunctional cytokine, which, among various other activities, acts as a growth factor for melanocytes and has recently been implicated in the pathogenesis of malignant melanoma. In the skin, the main source for HGF is dermal fibroblasts (FB). Here, we have investigated the regulation of HGF production and secretion by cytokines derived from UV-irradiated keratinocytes (KC) and by direct UV irradiation. We demonstrate that supernatants of ultraviolet (UV)B-irradiated KC strongly induce HGF production in FB, and that this effect was mediated primarily by IL-1alpha. Direct irradiation of FB with UVB had no effect on HGF expression. In contrast, irradiation with UVA1 strongly upregulated HGF mRNA production and secretion of the functional protein. Addition of neutralizing anti-HGF antibodies after UVA1 irradiation, as well as transfection of FB with HGF small-interfering RNA (siRNA); which completely abrogated HGF secretion led to a dramatic rise of FB apoptosis demonstrating that autocrine HGF efficiently protected FB from UVA1-induced apoptosis. Our data suggest that upregulation of HGF plays a role in skin homeostasis after UV irradiation. However, a negative side effect of UV-induced HGF secretion by dermal FB might represent a decisive factor for induction and/or progression of melanoma.

The third dimension bridges the gap between cell culture and live tissue

Moving from cell monolayers to three-dimensional (3D) cultures is motivated by the need to work with cellular models that mimic the functions of living tissues. Essential cellular functions that are present in tissues are missed by 'petri dish'-based cell cultures. This limits their potential to predict the cellular responses of real organisms. However, establishing 3D cultures as a mainstream approach requires the development of standard protocols, new cell lines and quantitative analysis methods, which include well-suited three-dimensional imaging techniques. We believe that 3D cultures will have a strong impact on drug screening and will also decrease the use of laboratory animals, for example, in the context of toxicity assays.

Differential expression of c-Met, its ligand HGF/SF and HER2/neu in DCIS and adjacent normal breast tissue

AIMS

Tyrosine kinase receptors Her2/neu and c-Met play an important role in breast cancer development and progression. Our aim was to determine the expression of c-Met, its ligand hepatocyte growth factor/scatter factor (HGF/SF) and Her2/neu in ductal carcinoma in situ (DCIS) lesions of the breast (n = 39) by two different immunocytochemical techniques, classical immunohistochemistry and immunofluorescence, and to correlate their expression levels with histopathological and clinical characteristics.

METHODS AND RESULTS

Both methods revealed similar c-Met staining patterns in both the in situ component and the adjacent normal tissue (P < 0.001). However, an imbalance in c-Met expression between tumour and surrounding normal tissue was correlated with high-grade DCIS (Van Nuys Grade 3). No correlation existed between Her2/neu and c-Met expression. High HGF/SF immunoreactivity was observed in 43.6% of the cases, yet the adjacent cellular stroma revealed only low levels of HGF/SF. No correlation existed between c-Met, Her2/neu or HGF/SF expression and clinicopathological factors.

CONCLUSION

An imbalance in c-Met expression between tumour and surrounding normal tissue is associated with an aggressive DCIS phenotype. Moreover, c-Met and HGF/SF may contribute to tumour development by different means than those controlled by Her2/neu.

Hepatocyte Growth Factor Exerts Multiple Biological Functions on Bovine Mammary Epithelial Cells

The met proto-oncogene product Met is a member of the family of tyrosine kinase growth factor receptors, and hepatocyte growth factor/scatter factor (HGF/SF) has been identified as its only ligand. Bovine Met and HGF/SF have been recently cloned and their expression has been characterized in the mammary gland, but no data regarding the biological effects of this ligand/receptor couple in bovine mammary cells are yet available. We examined the role of HGF/SF and its receptor in a bovine mammary epithelial cell line (BME-UV). Expression of Met at the mRNA level in BME-UV mammary epithelial cells evaluated by real-time PCR was similar to the expression in MDCK cells, a widely used model for Met biology. Met expression in BME-UV at the protein level was confirmed by western blot. The analysis of some signal transductional pathways downstream from the Met receptor revealed that HGF/SF addition to BME-UV cells induced activation of the extracellular signal-regulated kinase 1/2 proliferative pathway and the Akt antiapoptotic pathway. The BME-UV cells treated with HGF responded with increased proliferation, cell scatter, and motility. Met activation by HGF induced degradation of the extracellular matrix and migration through matrigel coated transwells. Moreover, BME-UV cells included in a 3-dimensional matrix of collagen and treated with HGF developed tubular structures, reminiscent of the mammary gland ducts. These data indicate that HGF and Met might be important regulators of mammary gland growth, morphogenesis, and development in the bovine.

p21 is decreased in polycystic kidney disease and leads to increased epithelial cell cycle progression: roscovitine augments p21 levels

Background

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disease with few treatment options other than renal replacement therapy. p21, a cyclin kinase inhibitor which has pleiotropic effects on the cell cycle, in many cases acts to suppress cell cycle progression and to prevent apoptosis. Because defects in cell cycle arrest and apoptosis of renal tubular epithelial cells occur in PKD, and in light of earlier reports that polycystin-1 upregulates p21 and that the cyclin-dependent kinase inhibitor roscovitine arrests progression in a mouse model, we asked whether (1) p21 deficiency might underlie ADPKD and (2) the mechanism of the salutary roscovitine effect on PKD involves p21.

Methods

p21 levels in human and animal tissue samples as well as cell lines were examined by immunoblotting and/or immunohistochemisty. Apoptosis was assessed by PARP cleavage. p21 expression was attenuated in a renal tubular epithelial cell line by antisense methods, and proliferation in response to p21 attenuation and to roscovitine was assessed by the MTT assay.

Results

We show that p21 is decreased in human as well as a non-transgenic rat model of ADPKD. In addition, hepatocyte growth factor, which induces transition from a cystic to a tubular phenotype, increases p21 levels. Furthermore, attenuation of p21 results in augmentation of cell cycle transit in vitro. Thus, levels of p21 are inversely correlated with renal tubular epithelial cell proliferation. Roscovitine, which has been shown to arrest progression in a murine model of PKD, increases p21 levels and decreases renal tubular epithelial cell proliferation, with no affect on apoptosis.

Conclusion

The novelty of our study is the demonstration in vivo in humans and rat models of a decrement of p21 in cystic kidneys as compared to non-cystic kidneys. Validation of a potential pathogenetic model of increased cyst formation due to enhanced epithelial proliferation and apoptosis mediated by p21 suggests a mechanism for the salutary effect of roscovitine in ADPKD and supports further investigation of p21 as a target for future therapy.

Targeted delivery of NK4 to multiple lung tumors by bone marrow-derived mesenchymal stem cells

Most advanced solid tumors metastasize to different organs. However, no gene therapy effective for multiple tumors has yet been developed. Since a unique characteristic of bone marrow-derived mesenchymal stem cells (MSCs) is that they migrate to tumor tissues, we wanted to determine whether MSCs could serve as a vehicle of gene therapy for targeting multiple tumors. First, we confirmed that mouse MSCs preferentially migrate to multiple tumors of the lung in the Colon-26 (C-26) lung metastasis model. Next, MSCs were efficiently transduced with NK4, an antagonist of hepatocyte growth factor (HGF), by an adenoviral vector with an RGD motif. MSCs expressing NK4 (NK4-MSCs) strongly inhibited development of lung metastases in the C-26 lung metastasis model after systemic administration via a tail vein. Treatment with NK4-MSCs significantly prolonged survival of the C-26-tumor-bearing mice by inhibiting tumor-associated angiogenesis and lymphangiogenesis and inducing apoptosis of the tumor cells. MSC-based gene therapy did not induce the severe adverse effects induced by conventional adenoviral vectors. These results indicate that MSCs can serve as a vehicle of gene therapy for targeting multiple lung metastatic tumors.