Scatter factor: molecular characteristics and effect on the invasiveness of epithelial cells

Architecture and migration of an epithelium on a cylindrical wire

In a wide range of epithelial tissues such as kidney tubules or breast acini, cells organize into bidimensional monolayers experiencing an out-of-plane curvature. Cancer cells can also migrate collectively from epithelial tumors by wrapping around vessels or muscle fibers. However, in vitro experiments dealing with epithelia are mostly performed on flat substrates, neglecting this out-of-plane component. In this paper, we study the development and migration of epithelial tissues on glass wires of well-defined radii varying from less than 1 µm up to 85 µm. To uncouple the effect of out-of-plane curvature from the lateral confinement experienced by the cells in these geometries, we compare our results to experiments performed on narrow adhesive tracks. Because of lateral confinement, the velocity of collective migration increases for radii smaller than typically 20 µm. The monolayer dynamics is then controlled by front-edge protrusions. Conversely, high curvature is identified as the inducer of frequent cell detachments at the front edge, a phenotype reminiscent of the Epithelial-Mesenchymal Transition. High curvature also induces a circumferential alignment of the actin cytoskeleton, stabilized by multiple focal adhesions. This organization of the cytoskeleton is reminiscent of in vivo situations such as the development of the trachea of the Drosophila embryo. Finally, submicron radii halt the monolayer, which then reconfigures into hollow cysts.

Role of HGF/MET axis in resistance of lung cancer to contemporary management

Lung cancer is the number one cause of cancer related mortality with over 1 million cancer deaths worldwide. Numerous therapies have been developed for the treatment of lung cancer including radiation, cytotoxic chemotherapy and targeted therapies. Histology, stage of presentation and molecular aberrations are main determinants of prognosis and treatment strategy. Despite the advances that have been made, overall prognosis for lung cancer patients remains dismal. Chemotherapy and/or targeted therapy yield objective response rates of about 35% to 60% in advanced stage non-small cell lung cancer (NSCLC). Even with good initial responses, median overall survival of is limited to about 12 months. This reflects that current therapies are not universally effective and resistance develops quickly. Multiple mechanisms of resistance have been proposed and the MET/HGF axis is a potential key contributor. The proto-oncogene MET (mesenchymal-epithelial transition factor gene) and its ligand hepatocyte growth factor (HGF) interact and activate downstream signaling via the mitogen-activated protein kinase (ERK/MAPK) pathway and the phosphatidylinositol 3-kinase (PI3K/AKT) pathways that regulate gene expression that promotes carcinogenesis. Aberrant MET/HGF signaling promotes emergence of an oncogenic phenotype by promoting cellular proliferation, survival, migration, invasion and angiogenesis. The MET/HGF axis has been implicated in various tumor types including lung cancers and is associated with adverse clinicopathological profile and poor outcomes. The MET/HGF axis plays a major role in development of radioresistance and chemoresistance to platinums, taxanes, camtothecins and anthracyclines by inhibiting apoptosis via activation of PI3K-AKT pathway. DNA damage from these agents induces MET and/or HGF expression. Another resistance mechanism is inhibition of chemoradiation induced translocation of apoptosis-inducing factor (AIF) thereby preventing apoptosis. Furthermore, this MET/HGF axis interacts with other oncogenic signaling pathways such as the epidermal growth factor receptor (EGFR) pathway and the vascular endothelial growth factor receptor (VEGFR) pathway. This functional cross-talk forms the basis for the role of MET/HGF axis in resistance against anti-EGFR and anti-VEGF targeted therapies. MET and/or HGF overexpression from gene amplification and activation are mechanisms of resistance to cetuximab and EGFR-TKIs. VEGF inhibition promotes hypoxia induced transcriptional activation of MET proto-oncogene that promotes angiogenesis and confers resistance to anti-angiogenic therapy. An extensive understanding of these resistance mechanisms is essential to design combinations with enhanced cytotoxic effects. Lung cancer treatment is challenging. Current therapies have limited efficacy due to primary and acquired resistance. The MET/HGF axis plays a key role in development of this resistance. Combining MET/HGF inhibitors with chemotherapy, radiotherapy and targeted therapy holds promise for improving outcomes.

Hepatocyte growth factor and Met in drug discovery

Activation of the hepatocyte growth factor (HGF)-Met pathway evokes dynamic biological responses that support the morphogenesis, regeneration and survival of cells and tissues. A characterization of conditional Met knockout mice indicates that the HGF-Met pathway plays important roles in the regeneration, protection and homeostasis of cells such as hepatocytes, renal tubular cells and neurons. Preclinical studies in disease models have indicated that recombinant HGF protein and expression plasmid for HGF are biological drug candidates for the treatment of patients with diseases or injuries that involve impaired tissue function. The phase-I and phase-I/II clinical trials of the intrathecal administration of HGF protein for the treatment of patients with amyotrophic lateral sclerosis and spinal cord injury, respectively, are ongoing. Biological actions of HGF that promote the dynamic movement, morphogenesis and survival of cells also closely participate in invasion-metastasis and resistance to the molecular-targeted drugs in tumour cells. Different types of HGF-Met pathway inhibitors are now in clinical trials for treatment of malignant tumours. Basic research on HGF and Met has lead to drug discoveries in regenerative medicine and tumour biology.

Epithelial-mesenchymal transitions: from cell plasticity to concept elasticity

Epithelial-mesenchymal transition (EMT) is a developmental cellular process occurring during early embryo development, including gastrulation and neural crest cell migration. It can be broken down in distinct functional steps: (1) loss of baso-apical polarization characterized by cytoskeleton, tight junctions, and hemidesmosomes remodeling; (2) individualization of cells, including a decrease in cell-cell adhesion forces, (3) emergence of motility, and (4) invasive properties, including passing through the subepithelial basement membrane. These phases occur in an uninterrupted process, without requiring mitosis, in an order and with a degree of completion dictated by the microenvironment. The whole process reflects the activation of specific transcription factor families, called EMT transcription factors. Several mechanisms can combine to induce EMT. Some are reversible, involving growth factors and cytokines and/or environmental signals including extracellular matrix and local physical conditions. Others are irreversible, such as genomic alterations during carcinoma progression, along a selective and irreversible clonal drift. In carcinomas, these signals can converge to initiate a metastable phenotype. In this state, similarly to activated keratinocytes during re-epithelialization, cells can initiate a cohort migration and engage into a transient and reversible EMT controlled by the local environment prior to efficient intravasation and metastasis. EMT transcription factors also participate in cancer progression by inducing apoptosis resistance and maintaining stem-like properties exposed in tumor recurrences. These properties, very important on a clinical point of view, are not intrinsically linked to EMT, but can share common pathways.

Targeting the hsp70 gene delays mammary tumor initiation and inhibits tumor cell metastasis

Elevated levels of the inducible heat-shock protein 70 (Hsp72) have been implicated in mammary tumorigenesis in histological investigations of human breast cancer. We therefore examined the role of Hsp72 in mice, using animals in which the hsp70 gene was inactivated. We used a spontaneous tumor system with mice expressing the polyomavirus middle T (PyMT) oncogene under control of the mouse mammary tumor virus (MMTV) long-terminal repeat (MMT mice). These mice developed spontaneous, metastatic mammary cancer. We then showed Hsp72 to be upregulated in a fraction of mammary cancer initiating cells (CIC) within the MMT tumor cell population. These cells were characterized by elevated surface levels of stem cell markers CD44 and Sca1 and by rapid metastasis. Inactivation of the hsp70 gene delayed the initiation of mammary tumors. This delay in tumor initiation imposed by loss of hsp70 was correlated with a decreased pool of CIC. Interestingly, hsp70 knockout significantly reduced invasion and metastasis by mammary tumor cells and implicated its product Hsp72 in cell migration and formation of secondary neoplasms. Impaired tumorigenesis and metastasis in hsp70-knockout MMT mice was associated with downregulation of the met gene and reduced activition of the oncogenic c-Met protein. These experiments therefore showed Hsp72 to be involved in the growth and progression of mammary carcinoma and highlighted this protein as a potential target for anticancer drug development.

Physiological Signaling and Structure of the HGF Receptor MET

The "hepatocyte growth factor" also known as "scatter factor", is a multifunctional cytokine with the peculiar ability of simultaneously triggering epithelial cell proliferation, movement and survival. The combination of those proprieties results in the induction of an epithelial to mesenchymal transition in target cells, fundamental for embryogenesis but also exploited by tumor cells during metastatization. The hepatocyte growth factor receptor, MET, is a proto-oncogene and a prototypical transmembrane tyrosine kinase receptor. Inhere we discuss the MET molecular structure and the hepatocyte growth factor driven physiological signaling which coordinates epithelial proliferation, motility and morphogenesis.

Analysis of 1,115 patients tested for MET amplification and therapy response in the MD Anderson Phase I Clinic

PURPOSE

This study aimed to assess MET amplification among different cancers, association with clinical factors and genetic aberrations and targeted therapy response modifications.

EXPERIMENTAL DESIGN

From May 2010 to November 2012, samples from patients with advanced tumors referred to the MD Anderson Phase I Clinic were analyzed for MET gene amplification by FISH. Patient demographic, histologic characteristics, molecular characteristics, and outcomes in phase I protocols were compared per MET amplification status.

RESULTS

Of 1,115 patients, 29 (2.6%) had MET amplification. The highest prevalence was in adrenal (2 of 13; 15%) and renal (4 of 28; 14%) tumors, followed by gastroesophageal (6%), breast (5%), and ovarian cancers (4%). MET amplification was associated with adenocarcinomas (P = 0.007), high-grade tumors (P = 0.003), more sites of metastasis, higher BRAF mutation, and PTEN loss (all P < 0.05). Median overall survival was 7.23 and 8.62 months for patients with and without a MET amplification, respectively (HR = 1.12; 95% confidence intervals, 0.83-1.85; P = 0.29). Among the 20 patients with MET amplification treated on a phase I protocol, 4 (20%) achieved a partial response with greatest response rate on agents targeting angiogenesis (3 of 6, 50%). No patient treated with a c-MET inhibitor (0 of 7) achieved an objective response.

CONCLUSION

MET amplification was detected in 2.6% of patients with solid tumors and was associated with adenocarcinomas, high-grade histology, and higher metastatic burden. Concomitant alterations in additional pathways (BRAF mutation and PTEN loss) and variable responses on targeted therapies, including c-MET inhibitors, suggest that further studies are needed to target this population.

Hepatocyte growth factor: A regulator of inflammation and autoimmunity

Hepatocyte growth factor (HGF) is a pleiotropic cytokine that has been extensively studied over several decades, but was only recently recognized as a key player in mediating protection of many types of inflammatory and autoimmune diseases. HGF was reported to prevent and attenuate disease progression by influencing multiple pathophysiological processes involved in inflammatory and immune response, including cell migration, maturation, cytokine production, antigen presentation, and T cell effector function. In this review, we discuss the actions and mechanisms of HGF in inflammation and immunity and the therapeutic potential of this factor for the treatment of inflammatory and autoimmune diseases.

The development of small molecule angiotensin IV analogs to treat Alzheimer's and Parkinson's diseases

Alzheimer's (AD) and Parkinson's (PD) diseases are neurodegenerative diseases presently without effective drug treatments. AD is characterized by general cognitive impairment, difficulties with memory consolidation and retrieval, and with advanced stages episodes of agitation and anger. AD is increasing in frequency as life expectancy increases. Present FDA approved medications do little to slow disease progression and none address the underlying progressive loss of synaptic connections and neurons. New drug design approaches are needed beyond cholinesterase inhibitors and N-methyl-d-aspartate receptor antagonists. Patients with PD experience the symptomatic triad of bradykinesis, tremor-at-rest, and rigidity with the possibility of additional non-motor symptoms including sleep disturbances, depression, dementia, and autonomic nervous system failure. This review summarizes available information regarding the role of the brain renin-angiotensin system (RAS) in learning and memory and motor functions, with particular emphasis on research results suggesting a link between angiotensin IV (AngIV) interacting with the AT4 receptor subtype. Currently there is controversy over the identity of this AT4 receptor protein. Albiston and colleagues have offered convincing evidence that it is the insulin-regulated aminopeptidase (IRAP). Recently members of our laboratory have presented evidence that the brain AngIV/AT4 receptor system coincides with the brain hepatocyte growth factor/c-Met receptor system. In an effort to resolve this issue we have synthesized a number of small molecule AngIV-based compounds that are metabolically stable, penetrate the blood-brain barrier, and facilitate compromised memory and motor systems. These research efforts are described along with details concerning a recently synthesized molecule, Dihexa that shows promise in overcoming memory and motor dysfunctions by augmenting synaptic connectivity via the formation of new functional synapses.

HGF-Met Pathway in Regeneration and Drug Discovery

Hepatocyte growth factor (HGF) is composed of an α-chain and a β-chain, and these chains contain four kringle domains and a serine protease-like structure, respectively. Activation of the HGF–Met pathway evokes dynamic biological responses that support morphogenesis (e.g., epithelial tubulogenesis), regeneration, and the survival of cells and tissues. Characterizations of conditional Met knockout mice have indicated that the HGF–Met pathway plays important roles in regeneration, protection, and homeostasis in various cells and tissues, which includes hepatocytes, renal tubular cells, and neurons. Preclinical studies designed to address the therapeutic significance of HGF have been performed on injury/disease models, including acute tissue injury, chronic fibrosis, and cardiovascular and neurodegenerative diseases. The promotion of cell growth, survival, migration, and morphogenesis that is associated with extracellular matrix proteolysis are the biological activities that underlie the therapeutic actions of HGF. Recombinant HGF protein and the expression vectors for HGF are biological drug candidates for the treatment of patients with diseases and injuries that are associated with impaired tissue function. The intravenous/systemic administration of recombinant HGF protein has been well tolerated in phase I/II clinical trials. The phase-I and phase-I/II clinical trials of the intrathecal administration of HGF protein for the treatment of patients with amyotrophic lateral sclerosis and spinal cord injury, respectively, are ongoing.

A phase II evaluation of AMG 102 (rilotumumab) in the treatment of persistent or recurrent epithelial ovarian, fallopian tube or primary peritoneal carcinoma: a Gynecologic Oncology Group study

OBJECTIVE

This open-label, multi-institutional phase II trial evaluated activity and safety of rilotumumab (AMG 102), a monoclonal antibody that targets HGF (hepatocyte growth factor), the ligand for the MET receptor, in women with recurrent or persistent epithelial ovarian, fallopian tube or primary peritoneal cancer.

PATIENTS AND METHODS

Women were eligible for treatment with rilotumumab if they had measurable disease, a performance status of 0, 1 or 2, previously received platinum-based therapy with a progression-free interval of <12 months or a second recurrence, and adequate bone marrow and organ function. Patients received rilotumumab 20mg/kg IV every 14 days until evidence of unacceptable toxicity or disease progression. The study utilized co-dual primary endpoints of tumor response and six-month PFS to assess the efficacy of rilotumumab. Secondary endpoints included the frequency and severity of adverse events and the duration of progression-free and overall survival.

RESULTS

Thirty-one women enrolled and received rilotumumab. All were eligible for analysis. One patient achieved a complete response (3.2%; 90% CI 0.2-14%), and two women had 6-month PFS (6.5%; 90% CI 1.1-19%). Most adverse events were grade 1 or 2, with no grade 4 adverse events. Grade 3 adverse events were gastrointestinal (4), metabolic (3) anemia (3), a thromboembolic event (1), ventricular tachycardia (1), hypotension during infusion (1) and fatigue (1). The study was stopped after the first stage of accrual.

CONCLUSION

Rilotumumab was well-tolerated, but had limited activity. The level of activity does not warrant further evaluation of rilotumumab as a single agent in patients with ovarian cancer.

Resistance to targeted cancer drugs through hepatocyte growth factor signaling

Cancer therapeutics that target a signaling pathway to which the cancer cells are addicted can deliver dramatic initial responses, but resistance is nearly always inevitable. A variety of mechanisms that cancer cells employ to escape from targeted cancer drugs have been described. We review here the role of Hepatocyte Growth Factor (HGF) and its receptor MET in drug resistance. We present data demonstrating that HGF can confer resistance to a number of kinase inhibitors in a variety of cancer cell lines and discuss our results in relation to the findings of others. Together, these data point at a major role for HGF/MET signaling in resistance to a variety of targeted cancer drugs.

Novel roles of liver sinusoidal endothelial cell lectin in colon carcinoma cell adhesion, migration and in-vivo metastasis to the liver

OBJECTIVE

Adhesion molecules play an important role in tumour metastasis. The liver is a frequent target for the metastasis of several tumour types. However, virtually no liver-specific adhesion molecules have been described in terms of organ-specific metastasis. This study aimed to determine the role of liver sinusoidal endothelial cell lectin (LSECtin) in colon carcinoma metastasis to the liver.

DESIGN

The role of LSECtin in colon carcinoma metastasis to the liver was determined by LSECtin knockout nude mice and anti-LSECtin antibody. LSECtin promoting the migration of LS174T and LoVo cells was determined by transwell experiment. The serum levels of soluble LSECtin in patients were elevated by ELISA.

RESULTS

LSECtin was found to adhere to LS174T and LoVo colon cancer cells in vitro and in vivo. Deficiency or blocking of LSECtin significantly decreased hepatic metastases of LS174T and LoVo cells. Primary colon cancer cells from patients also exhibited remarkably low rates of hepatic metastasis in LSECtin knockout mice. LSECtin promoted the migration of LS174T and LoVo cells and increased the expression of c-Met in these cells. Serum soluble LSECtin was detected at significantly higher levels in colon cancer patients with or without hepatic metastases compared with healthy controls and was also increased in colon cancer patients with metastases compared with those without metastases.

CONCLUSION

The results indicate that LSECtin plays an important role in colorectal carcinoma liver metastasis and may be a promising new target for intervention in metastasis formation.

Biological influence of Hakai in cancer: a 10-year review

In order to metastasize, cancer cells must first detach from the primary tumor, migrate, invade through tissues, and attach to a second site. Hakai was discovered as an E3 ubiquitin-ligase that mediates the posttranslational downregulation of E-cadherin, a major component of adherens junctions in epithelial cells that is characterized as a potent tumor suppressor and is modulated during various processes including epithelial–mesenchymal transition. Recent data have provided evidences for novel biological functional role of Hakai during tumor progression and other diseases. Here, we will review the knowledge that has been accumulated since Hakai discovery 10 years ago and its implication in human cancer disease. We will highlight the different signaling pathways leading to the influence on Hakai and suggest its potential usefulness as therapeutic target for cancer.

Hepatocyte growth factor stimulates neutrophil degranulation but not respiratory burst

Neutrophil function is regulated in part by cytokines with growth factor activities for different cell types. Hepatocyte growth factor (HGF) is a cytokine produced during injury to the liver and other organs. Neutrophils are numerous in such tissue injury sites and may be influenced by HGF. In the present study the effect of HGF on neutrophils was investigated. The data show that HGF at 1-10 ng/ml increased lysosomal enzyme release from both specific and azurophilic granules of cytochalasin-B treated neutrophils. The release of specific granule contents in response to N-formyl-methionyl-leucylphenylalanine was also increased by HGF. In contrast there were no significant effects of HGF on neutrophil respiratory burst, adherence or locomotion. It is concluded that HGF modulates neutrophil granule exocytosis.

Role of the MET–HGF axis in colorectal cancer: precepts and prospects

SUMMARY Colorectal cancer (CRC) accounts for 10% of all cancer-related mortality globally. Despite significant therapeutic advances, overall survival is limited. The restricted repertoire of therapies necessitates investigation into novel pathways of colorectal carcinogenesis. The proto-oncogene MET encodes a receptor tyrosine kinase that acts as a receptor for the HGF. Dysregulation of this MET–HGF axis has been implicated in proliferation, survival and metastasis in various tumor types including CRC. Increased MET–HGF expression correlates with tumor progression and adverse survival outcome. The prognostic impact argues in favor of employing inhibition of the MET–HGF axis as a promising new therapeutic strategy. Future investigations should endeavor to assess the potential application of targeted MET–HGF therapy in CRC and towards patient selection.

Plasma membrane ion fluxes and NFAT-dependent gene transcription contribute to c-met-induced epithelial scattering

Hepatocyte growth factor (HGF) signaling drives epithelial cells to scatter by breaking cell-cell adhesions and causing them to migrate as solitary cells, a process that parallels epithelial-mesenchymal transition. HGF binds and activates the c-met receptor tyrosine kinase, but downstream signaling required for scattering remains poorly defined. We have applied a chemical biology approach to identify components of HGF signaling that are required for scattering in an in vitro model system. This approach yields a number of small molecules that block HGF-induced scattering, including a calcium channel blocker. We show that HGF stimulation results in sudden and transient increases in ion channel influxes at the plasma membrane. Although multiple channels occur in the membranes of our model system, we find that TrpC6 is specifically required for HGF-induced scattering. We further demonstrate that HGF-induced ion influxes through TrpC6 channels coincide with a transient increase in nuclear factor of activated T-cells (NFAT)-dependent gene transcription and that NFAT-dependent gene transcription is required for HGF-induced cell scattering.

Chemopreventive effects of tolfenamic acid against esophageal tumorigenesis in rats

The primary objective of this study is to identify small molecules that target critical transcription factors for potential application in the chemoprevention of esophageal cancer. Specificity proteins (Sp) play a critical role in the growth and metastasis of several malignancies including esophageal cancer. Researchers at the M. D. Anderson Cancer Center Orlando Cancer Research Institute have reported previously that tolfenamic acid (TA) inhibits cancer cell proliferation and tumor growth through the degradation of Sp1, Sp3, and Sp4. We evaluated the chemopreventive properties of TA against esophageal tumorigenesis in N-nitrosomethylbenzylamine (NMBA)-induced murine tumor model. Fischer-344 rats were treated with NMBA (0.5 mg/kg s.c. 3 times a week) for 5 weeks to initiate the tumor formation, and then treated with 50 mg/kg TA from week 6 through week 25. Tumor incidence, tumor multiplicity (number of papilloma per rat), and tumor volume were evaluated after 25 weeks. All rats in the control group that received only NMBA developed lesions (100% incidence), while the TA-treated group showed significantly lower (33%) tumor incidence and tumor multiplicity. Furthermore, the tumor volume was significantly diminished in the TA-treated group when compared with the control group. Using small molecules such as TA to target key transcription factors associated with tumorigenesis for the prevention of esophageal malignancies is a new and promising strategy. Results of the current study provide evidence that TA, when given orally after tumor initiation, can significantly suppress tumorigenesis induced by carcinogenic nitrosamines in rats. These appealing results demonstrate that TA may potentially serve as an effective chemopreventive agent in patient populations vulnerable to esophageal cancer.

cMET and phospho-cMET protein levels in breast cancers and survival outcomes

PURPOSE

To evaluate cMET (mesenchymal-epithelial transition factor gene) and phospho-cMET (p-cMET) levels in breast cancer subtypes and its impact on survival outcomes.

EXPERIMENTAL DESIGN

We measured protein levels of cMET and p-cMET in 257 breast cancers using reverse phase protein array. Regression tree method and Martingale residual plots were applied to find best cutoff point for high and low levels. Kaplan-Meier survival curves were used to estimate relapse-free (RFS) and overall (OS) survival. Cox proportional hazards models were fit to determine associations of cMET/p-cMET with outcomes after adjustment for other characteristics.

RESULTS

Median age was 51 years. There were 140 (54.5%) hormone receptor (HR) positive, 53 (20.6%) HER2 positive, and 64 (24.9%) triple-negative tumors. Using selected cutoffs, 181 (70.4%) and 123 (47.9%) cancers had high levels of cMET and p-cMET, respectively. There were no significant differences in mean expression of cMET (P < 0.128) and p-cMET (P < 0.088) by breast cancer subtype. Dichotomized cMET and p-cMET level was a significant prognostic factor for RFS [HR: 2.44, 95% confidence interval (CI): 1.34-4.44, P = 0.003 and HR: 1.64, 95% CI: 1.04-2.60, P = 0.033] and OS (HR: 3.18, 95% CI: 1.43-7.11, P = 0.003 and HR: 1.92, 95% CI: 1.08-3.44, P = 0.025). Within breast cancer subtypes, high cMET levels were associated with worse RFS (P = 0.014) and OS (P = 0.006) in HR-positive tumors, and high p-cMET levels were associated with worse RFS (P = 0.019) and OS (P = 0.014) in HER2-positive breast cancers. In multivariable analysis, patients with high cMET had a significantly higher risk of recurrence (HR: 2.06, 95% CI: 1.08-3.94, P = 0.028) and death (HR: 2.81, 95% CI: 1.19-6.64, P = 0.019). High p-cMET level was associated with higher risk of recurrence (HR: 1.79, 95% CI: 1.08-2.95.77, P = 0.020).

CONCLUSIONS

High levels of cMET and p-cMET were seen in all breast cancer subtypes and correlated with poor prognosis.

Targeting MET in cancer: rationale and progress

Uncontrolled cell survival, growth, angiogenesis and metastasis are essential hallmarks of cancer. Genetic and biochemical data have demonstrated that the growth and motility factor hepatocyte growth factor/scatter factor (HGF/SF) and its receptor, the tyrosine kinase MET, have a causal role in all of these processes, thus providing a strong rationale for targeting these molecules in cancer. Parallel progress in understanding the structure and function of HGF/SF, MET and associated signalling components has led to the successful development of blocking antibodies and a large number of small-molecule MET kinase inhibitors. In this Review, we discuss these advances, as well as results from recent clinical studies that demonstrate that inhibiting MET signalling in several types of solid human tumours has major therapeutic value.

The role of HGF/c-Met signaling in prostate cancer progression and c-Met inhibitors in clinical trials

INTRODUCTION

An increasing number of basic, translational and clinical studies demonstrate the importance of the protein tyrosine kinase receptor, c-Met, in the progression of prostate cancer. c-Met is overexpressed in primary prostate cancers, further increased in expression in bone metastases and is associated with the development of castrate-resistant disease. Because of its importance as a target, c-Met inhibitors have reached clinical trial for advanced, castrate-resistant prostate cancer.

AREAS COVERED

In this review, altered expression of c-Met and hepatocyte growth factor in prostate tumors and the microenvironment and how they contribute to growth and invasion of prostate cancer cells is described. Next, preclinical studies providing the support for use of c-Met inhibitors are discussed. Finally, early promising results from c-Met inhibitors in clinical trial, and future prospects for c-Met inhibitors in the treatment of advanced stage prostate cancer, are discussed.

EXPERT OPINION

An emerging theme in treating metastatic prostate cancer is the requirement to target both the epithelial and stromal compartments. Results from clinical trials suggest that inhibitors of c-Met that block stromal-mediated c-Met activation in prostate tumors may be important therapeutic agents in at least a subset of patients with metastatic prostate cancer. However, as many of the inhibitors have multiple targets, the efficacy of targeting c-Met alone remains to be determined.

Hair follicle regeneration in skin grafts: current concepts and future perspectives

The repair and management of full-thickness skin defects resulting from burns and chronic wounds remain a significant unmet clinical challenge. For those skin defects exceeding 50%-60% of total body surface area, it is impractical to treat with autologous skin transplants because of the shortage of donor sites. The possibility of using tissue-engineered skin grafts for full-thickness wound repair is a promising approach. The primary goal of tissue-engineered skin grafts is to restore lost barrier function, but regeneration of appendages, such as hair follicles, has to be yet achieved. The successful regeneration of hair follicles in immunodeficient mice suggests that creating human hair follicles in tissue-engineered skin grafts is feasible. However, many limitations still need to be explored, particularly enriching isolated cells with trichogenic capacity, maintaining this ability during processing, and providing the cells with proper environmental cues. Current advances in hair follicle regeneration, in vitro and in vivo, are concisely summarized in this report, and key requirements to bioengineer a hair follicle are proposed, with emphasis on a three-dimensional approach.

Growth factor signaling pathways as targets for prevention of epithelial carcinogenesis

Growth factor receptor (GFR) signaling controls epithelial cell growth by responding to various endogenous or exogenous stimuli and subsequently activating downstream signaling pathways including Stat3, PI3K/Akt/mTOR, MAPK, and c-Src. Environmental chemical toxicants and UVB irradiation cause enhanced and prolonged activation of GFR signaling and downstream pathways that contributes to epithelial cancer development including skin cancer. Recent studies, especially those with tissue-specific transgenic mouse models, have demonstrated that GFRs and their downstream signaling pathways contribute to all three stages of epithelial carcinogenesis by regulating a wide variety of biological functions including proliferation, apoptosis, angiogenesis, cell adhesion, and migration. Inhibiting these signaling pathways early in the carcinogenic process results in reduced cell proliferation and survival, leading to decreased tumor formation. Collectively, these studies suggest that GFR signaling and subsequent downstream signaling pathways are potential targets for the prevention of epithelial cancers including skin cancer.

Hepatocyte growth factor twenty years on: Much more than a growth factor

Liver regeneration depends on the proliferation of mature hepatocytes. In the 1980s, the method for the cultivation of mature hepatocytes provided an opportunity for the discovery of hepatocyte growth factor (HGF) as a protein that is structurally and functionally different from other growth factors. In 1991, the scatter factor, tumor cytotoxic factor, and 3-D epithelial morphogen were identified as HGF, and Met tyrosine kinase was identified as the receptor for HGF. Thus, the connection of apparently unrelated research projects rapidly enriched the research on HGF in different fields. The HGF-Met pathway plays important roles in the embryonic development of the liver and the placenta, in the migration of myogenic precursor cells, and in epithelial morphogenesis. The use of tissue-specific knockout mice demonstrated that in mature tissues the HGF-Met pathway plays a critical role in tissue protection and regeneration, and in providing less susceptibility to chronic inflammation and fibrosis. In various injury and disease models, HGF promotes cell survival, regeneration of tissues, and suppresses and improves chronic inflammation and fibrosis. Drug development using HGF has been challenging, but extensive preclinical studies to address its therapeutic effects have provided significant results sufficient for the development of HGF as a biological drug in the regeneration-based therapy of diseases. Clinical trials using recombinant human HGF protein, or HGF genes, are in progress for the treatment of diseases.

Interplay of cadherin-mediated cell adhesion and canonical Wnt signaling

The epithelial-mesenchymal transition is essential in both embryonic development and the progression of carcinomas. Wnt signaling and cadherin-mediated adhesion have been implicated in both processes; clarifying their role will depend on linking them to rearrangements of cellular structure and behavior. beta-Catenin is an essential molecule both in cadherin-mediated cell adhesion and in canonical Wnt signaling. Numerous experiments have shown that the loss of cadherin-mediated cell adhesion can promote beta-catenin release and signaling; this is accomplished by proteases, protein kinases and other molecules. Cadherin loss can also signal to several other regulatory pathways. Additionally, many target genes of Wnt signaling influence cadherin adhesion. The most conspicuous of these Wnt target genes encode the transcription factors Twist and Slug, which directly inhibit the E-cadherin gene promoter. Other Wnt/beta-catenin target genes encode metalloproteases or the cell adhesion molecule L1, which favor the degradation of E-cadherin. These factors provide a mechanism whereby cadherin loss and increased Wnt signaling induce epithelial-mesenchymal transition in both carcinomas and development.

Hepatocyte growth factor/Met gene transfer in cardiac stem cells--potential for cardiac repair

The adult heart has been recently recognized as a self-renewing organ that contains a pool of committed resident cardiac stem cells (CSCs) and cardiac progenitor cells (CPCs). These adult CSCs and CPCs can be induced by cytokines and growth factors to migrate, differentiate, and proliferate in situ and potentially replace lost cardiomyocytes. Ligand-receptor systems, such as the tyrosine kinase receptor mesenchymal-epithelial transition factor (Met) and its ligand hepatocyte growth factor (HGF), are potential candidates for boosting migration, engraftment and commitment of CSCs. Here, we discuss the possible application of HGF/Met gene therapy to enhance the ability of CSCs to promote myocardial regeneration.

The molecular mediators of type 2 epithelial to mesenchymal transition (EMT) and their role in renal pathophysiology

Common to all forms of chronic kidney disease is the progressive scarring of the tubulo-interstitial space, associated with the acquisition and accumulation of activated myofibroblasts. Many of these myofibroblasts are generated when tubular epithelial cells progressively lose their epithelial characteristics (cell-cell contact, microvilli, tight-junction proteins, apical-basal polarity) and acquire features of a mesenchymal lineage, including stress fibres, filopodia and augmented matrix synthesis. This process, known as epithelial to mesenchymal transition (EMT), plays an important role in progressive kidney disease. For EMT to occur in tubular cells, the transcriptional activation (and derepression) of genes required to sustain mesenchymal-type structures and functions (e.g. vimentin, alpha-smooth muscle actin) must occur alongside repression (or deactivation) of genes that act to maintain the epithelial phenotype (e.g. E-cadherin, bone morphogenic protein 7). Several factors have been suggested as potential initiators of EMT. With a few key exceptions, these triggers require the induction of transforming growth factor beta (TGF-beta) and downstream mediators, including SMADs, CTGF, ILK and SNAI1. Activation of TGF-beta receptors is also able to stimulate a range of additional pathways (so-called non-SMAD activation), including RhoA, mitogen-activated protein kinase and phosphoinositide 3-kinase signalling cascades, that also contribute to EMT and renal fibrogenesis. This review examines in detail the molecular mediators of EMT in tubular cells and its potential role as a long-lasting mediator of metabolic stress.

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.

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.

EGF-induced ERK activation promotes CK2-mediated disassociation of alpha-Catenin from beta-Catenin and transactivation of beta-Catenin

Increased transcriptional activity of beta-catenin resulting from Wnt/Wingless-dependent or -independent signaling has been detected in many types of human cancer, but the underlying mechanism of Wnt-independent regulation remains unclear. We demonstrate here that EGFR activation results in disruption of the complex of beta-catenin and alpha-catenin, thereby abrogating the inhibitory effect of alpha-catenin on beta-catenin transactivation via CK2alpha-dependent phosphorylation of alpha-catenin at S641. ERK2, which is activated by EGFR signaling, directly binds to CK2alpha via the ERK2 docking groove and phosphorylates CK2alpha primarily at T360/S362, subsequently enhancing CK2alpha activity toward alpha-catenin phosphorylation. In addition, levels of alpha-catenin S641 phosphorylation correlate with levels of ERK1/2 activity in human glioblastoma specimens and with grades of glioma malignancy. This EGFR-ERK-CK2-mediated phosphorylation of alpha-catenin promotes beta-catenin transactivation and tumor cell invasion. These findings highlight the importance of the crosstalk between EGFR and Wnt pathways in tumor development.

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.

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.

Contribution of human hematopoietic stem cells to liver repair

Immune-deficient mouse models of liver damage allow examination of human stem cell migration to sites of damage and subsequent contribution to repair and survival. In our studies, in the absence of a selective advantage, transplanted human stem cells from adult sources did not robustly become hepatocytes, although some level of fusion or hepatic differentiation was documented. However, injected stem cells did home to the injured liver tissue and release paracrine factors that hastened endogenous repair and enhanced survival. There were significantly higher levels of survival in mice with a toxic liver insult that had been transplanted with human stem cells but not in those transplanted with committed progenitors. Transplantation of autologous adult stem cells without conditioning is a relatively safe therapy. Adult stem cells are known to secrete bioactive factors that suppress the local immune system, inhibit fibrosis (scar formation) and apoptosis, enhance angiogenesis, and stimulate recruitment, retention, mitosis, and differentiation of tissue-residing stem cells. These paracrine effects are distinct from the direct differentiation of stem cells to repair tissue. In patients at high risk while waiting for a liver transplant, autologous stem cell therapy could be considered, as it could delay the decline in liver function.

Hepatocyte growth factor induces hypoxia-related interleukin-8 expression in lung adenocarcinoma cells

Rapid growth of cancer cells often creates insufficient supply of oxygen and nutrients in the tumour nest. The frequent detection of hypoxia-inducible factor (HIF) and interleukin-8 (IL-8) in afflicted tissues suggests that IL-8 expression could be associated with elevated levels of HIF. Recently, we found that hypoxia also upregulated the expression of hepatocyte growth factor (HGF) in lung adenocarcinoma (LAD) cells. However, the relationship between HGF and IL-8 has not been investigated in LAD cells. In this study, we found that HGF induced IL-8 expression in LAD. Interestingly, hypoxia also increased the level of prostaglandin F(2alpha) (PGF(2alpha)), a product of dihydrodiol dehydrogenase (DDH). When expression of DDH was suppressed by siRNA, the levels of PGF(2alpha), HGF and IL-8 were reduced; however, their levels returned to normal after DDH was reintroduced. These data suggest that hypoxia induces biosynthesis of PGF(2alpha), which then activates HGF and IL-8 expression. The results provide a reasonable explanation of how PGF(2alpha), HGF and IL-8 exert their effects on cancer cell metastasis.

Alternative proteolytic processing of hepatocyte growth factor during wound repair

Wound healing is a crucial regenerative process in all organisms. We examined expression, integrity, and function of the proteins in the hepatocyte growth factor (HGF)/c-Met signaling pathway in normally healing and non-healing human skin wounds. Whereas in normally healing wounds phosphorylation of c-Met was most prominent in keratinocytes and dermal cells, in non-healing wounds phosphorylation of c-Met was barely detectable, suggesting reduced c-Met activation. In wound exudates obtained from non-healing, but not from healing wounds, HGF protein was a target of substantial proteolytic processing that was different from the classical activation by known serine proteases. Western blot analysis and protease inhibitor studies revealed that HGF is a target of neutrophil elastase and plasma kallikrein during skin repair. Proteolytic processing of HGF by each of these proteases significantly attenuated keratinocyte proliferation, wound closure capacity in vitro, and c-Met signal transduction. Our findings reveal a novel pathway of HGF processing during skin repair. Conditions in which proteases are imbalanced and tend toward increased proteolytic activity, as in chronic non-healing wounds, might therefore compromise HGF activity due to the inactivation of the HGF protein and/or the generation of HGF fragments that ultimately mediate a dominant negative effect and limit c-Met activation.

Pak4, a novel Gab1 binding partner, modulates cell migration and invasion by the Met receptor

Hepatocyte growth factor (HGF), the ligand for the Met receptor tyrosine kinase, induces epithelial cell dispersal, invasion, and morphogenesis, events that require remodeling of the actin cytoskeleton. The scaffold protein Gab1 is essential for these biological responses downstream from Met. We have identified p21-activated kinase 4 (Pak4) as a novel Gab1-interacting protein. We show that in response to HGF, Gab1 and Pak4 associate and colocalize at the cell periphery within lamellipodia. The association between Pak4 and Gab1 is dependent on Gab1 phosphorylation but independent of Pak4 kinase activity. The interaction is mediated through a region in Gab1, which displays no homology to known Gab1 interaction motifs and through the guanine exchange factor-interacting domain of Pak4. In response to HGF, Gab1 and Pak4 synergize to enhance epithelial cell dispersal, migration, and invasion, whereas knockdown of Pak4 attenuates these responses. A Gab1 mutant unable to recruit Pak4 fails to promote epithelial cell dispersal and an invasive morphogenic program in response to HGF, demonstrating a physiological requirement for Gab1-Pak4 association. These data demonstrate a novel association between Gab1 and Pak4 and identify Pak4 as a key integrator of cell migration and invasive growth downstream from the Met receptor.

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.

Exosomes from bronchoalveolar fluid of tolerized mice prevent allergic reaction

Exosomes are nanovesicles originating from multivesicular bodies that are secreted by a variety of cell types. The dual capability of exosomes to promote immunity or to induce tolerance has prompted their clinical use as vehicles for vaccination against different human diseases. In the present study, the effect of allergen-specific exosomes from tolerized mice on the development of allergen-induced allergic response was determined using a mouse model. Mice were tolerized by respiratory exposure to the olive pollen allergen Ole e 1. Exosome-like vesicles were isolated from bronchoalveolar lavage fluid of the animals by the well-established filtration and ultracentrifugation procedure, characterized by electron microscopy, Western blot, and FACS analyses, and assessed in a prophylactic protocol. To this end, BALB/c mice were intranasally treated with tolerogenic exosomes or naive exosomes as control, 1 wk before sensitization/challenge to Ole e 1. Blood, lungs, and spleen were collected and analyzed for immune responses. Intranasal administration of tolerogenic exosomes inhibited the development of IgE response, Th2 cytokine production, and airway inflammation--cardinal features of allergy--and maintained specific long-term protection in vivo. This protective effect was associated with a concomitant increase in the expression of the regulatory cytokine TGF-beta. These observations demonstrate that exosomes can induce tolerance and protection against allergic sensitization in mice. Thus, exosome-based vaccines could represent an alternative to conventional therapy for allergic diseases in humans.

Raf kinase inhibitor protein positively regulates cell-substratum adhesion while negatively regulating cell-cell adhesion

Raf kinase inhibitor protein (RKIP) regulates a number of cellular processes, including cell migration. Exploring the role of RKIP in cell adhesion, we found that overexpression of RKIP in Madin-Darby canine kidney (MDCK) epithelial cells increases adhesion to the substratum, while decreasing adhesion of the cells to one another. The level of the adherens junction protein E-cadherin declines profoundly, and there is loss of normal localization of the tight junction protein ZO-1, while expression of the cell-substratum adhesion protein beta1 integrin dramatically increases. The cells also display increased adhesion and spreading on multiple substrata, including collagen, gelatin, fibronectin and laminin. In three-dimensional culture, RKIP overexpression leads to marked cell elongation and extension of long membrane protrusions into the surrounding matrix, and the cells do not form hollow cysts. RKIP-overexpressing cells generate considerably more contractile traction force than do control cells. In contrast, RNA interference-based silencing of RKIP expression results in decreased cell-substratum adhesion in both MDCK and MCF7 human breast adenocarcinoma cells. Treatment of MDCK and MCF7 cells with locostatin, a direct inhibitor of RKIP and cell migration, also reduces cell-substratum adhesion. Silencing of RKIP expression in MCF7 cells leads to a reduction in the rate of wound closure in a scratch-wound assay, although not as pronounced as that previously reported for RKIP-knockdown MDCK cells. These results suggest that RKIP has important roles in the regulation of cell adhesion, positively controlling cell-substratum adhesion while negatively controlling cell-cell adhesion, and underscore the complex functions of RKIP in cell physiology.

Specific inhibitors of the protein tyrosine phosphatase Shp2 identified by high-throughput docking

The protein tyrosine phosphatase Shp2 is a positive regulator of growth factor signaling. Gain-of-function mutations in several types of leukemia define Shp2 as a bona fide oncogene. We performed a high-throughput in silico screen for small-molecular-weight compounds that bind the catalytic site of Shp2. We have identified the phenylhydrazonopyrazolone sulfonate PHPS1 as a potent and cell-permeable inhibitor, which is specific for Shp2 over the closely related tyrosine phosphatases Shp1 and PTP1B. PHPS1 inhibits Shp2-dependent cellular events such as hepatocyte growth factor/scatter factor (HGF/SF)-induced epithelial cell scattering and branching morphogenesis. PHPS1 also blocks Shp2-dependent downstream signaling, namely HGF/SF-induced sustained phosphorylation of the Erk1/2 MAP kinases and dephosphorylation of paxillin. Furthermore, PHPS1 efficiently inhibits activation of Erk1/2 by the leukemia-associated Shp2 mutant, Shp2-E76K, and blocks the anchorage-independent growth of a variety of human tumor cell lines. The PHPS compound class is therefore suitable for further development of therapeutics for the treatment of Shp2-dependent diseases.

beta-Catenin and actin reorganization in HGF/SF response of ST14A cells

Hepatocyte growth factor/scatter factor (HGF/SF) is a pleiotropic factor that activates proliferation, differentiation, and migration of various cell types. Its action is mediated by c-Met, a receptor endowed with tyrosine kinase activity that activates complex signaling cascades and mediates diverse cell responses. Although HGF action was first demonstrated in epithelial cells, expression of HGF and c-Met receptor has also been described in developing and adult mammalian brain. In the developing central nervous system, areas of HGF and c-Met expression are coincident with the migratory pathway of precursor cells. In the present article we report that the interaction between c-Met and HGF/SF in striatal progenitor ST14A cells triggers a signaling cascade that induces modification of cell morphology, with decreased cell-cell interactions and increased cell motility; in particular, we analyzed the reorganization of the actin cytoskeleton and the delocalization of beta-catenin and N-cadherin. The testing of other neurotrophic factors (NGF, BDNF, NT3, and CNTF) showed that the observed modifications were peculiar to HGF. We show that phosphoinositide 3-kinase inhibitor treatment, which blocks cell scattering induced by HGF/SF, does not abolish actin and beta-catenin redistribution. The effects of HGF/SF on primary spinal cord cell cultures were also investigated, and HGF/SF was found to have a possible motogenic effect on these cells. The data reported suggest that HGF could play a role in the early steps of neurogenesis as a motogenic factor.

Hepatocyte growth factor gene therapy for hypertension

Hepatocyte growth factor (HGF) has mitogenic, motogenic, and morphogenic biological activities as well as helps in regenerating various tissues. In cardiovascular organs, HGF was reported to have anti-apoptotic, anti-fibrotic, and vasodilating effects. HGF has close relationships with hypertension, arteriosclerosis, and heart failure. HGF enhances renal regeneration and suppresses the progression of hypertension. Intramuscular electroporation of the therapeutic gene is a simple, economic, and low toxic method compared with systemic administration of the purified proteins or peptides. We outline the technique of intramuscular electroporation of HGF gene as a remedy for hypertension.

Two stage cadherin kinetics require multiple extracellular domains but not the cytoplasmic region

Micropipette manipulation measurements quantified the pre-steady state binding kinetics between cell pairs mediated by Xenopus cleavage stage cadherin. The time-dependence of the intercellular binding probability exhibits a fast forming, low probability binding state, which transitions to a slower forming, high probability state. The biphasic kinetics are independent of the cytoplasmic region, but the transition to the high probability state requires the third extracellular domain EC3. Deleting either EC3 or EC3-5, or substituting Trp(2) for Ala reduces the binding curves to a simple, monophasic rise in binding probability to a limiting plateau, as predicted for a single site binding mechanism. The two stage cadherin binding process reported here directly parallels previous biophysical studies, and confirms that the cadherin ectodomain governs the initial intercellular adhesion dynamics.