Evidence of antiangiogenic and antimetastatic activities of the recombinant disintegrin domain of metargidin

The metalloproteinase ADAM15 is upregulated by shear stress and promotes survival of endothelial cells

Reduced shear stress resulting from disturbed blood flow can impair endothelial integrity and drive the development of vascular inflammatory lesions. Metalloproteinases of the ADAM family have been implicated in the regulation of cell survival and inflammatory responses. Here we investigate the mechanism and function of ADAM15 upregulation in primary flow cultured endothelial cells. Transcriptomic analysis indicated that within the ADAM family ADAM15 mRNA is most prominently upregulated (4-fold) when endothelial cells are exposed to physiologic shear stress. This induction was confirmed in venous, arterial and microvascular endothelial cells and is associated with increased presence of ADAM15 protein in the cell lysates (5.6-fold) and on the surface (3.1-fold). The ADAM15 promoter contains several consensus sites for the transcription factor KLF2 which is also upregulated by shear stress. Induction of endothelial KLF2 by simvastatin treatment is associated with ADAM15 upregulation (1.8-fold) which is suppressed by counteracting simvastatin with geranylgeranyl pyrophosphate. KLF2 overexpression promotes ADAM15 expression (2.1-fold) under static conditions whereas KLF2 siRNA knockdown prevents ADAM15 induction by shear stress. Functionally, ADAM15 promotes survival of endothelial cells challenged by growth factor depletion or TNF stimulation as shown by ADAM15 shRNA knockdown (1.6-fold). Exposure to shear stress increases endothelial survival while additional knockdown of ADAM15 reduces survival (6.7-fold) under flow conditions. Thus, physiologic shear stress resulting from laminar flow promotes KLF2 induced ADAM15 expression which contributes to endothelial survival. The absence of ADAM15 at low shear stress or static conditions may therefore lead to increased endothelial damage and promote vascular inflammation.

Leucurogin and melanoma therapy

Leucurogin is an ECD disintegrin-like protein, cloned from Bothrops leucurus venom gland. This new protein, encompassing the disintegrin region of a PIII metalloproteinase, is produced by recombinant technology and its biological and functional activity was partially characterized in this study. Biological activity was characterized in vitro using human fibroblasts. Functional activity of leucurogin was analysed in vitro and in vivo with murine B16F10 Nex-2 and human melanoma BLM cells. The results show that leucurogin inhibits cellular processes dependent on collagen type I. In a competition assay with collagen, leucurogin inhibits, in a dose-dependent manner, the adhesion of fibroblast to collagen. At 10 μM leucurogin reduces adhesion (40%) and migration (70%) of hFb and inhibits migration (32%) and proliferation (65%) of BLM cells. At 2.5 μM leucurogin inhibits 80% cell proliferation of B16F10 Nex-2 melanoma cells. At 4.8 μM leucurogin inhibits, in vitro, the vascular structures formation by endothelial cells by 66%. Leucurogin, injected intraperitoneally, i.p. (5 μg/animal, two-month old C57/Bl6 male mice) on alternate days for 15 days, inhibits lung metastasis of B16F10 Nex-2 cells by 70-75%. In the treatment of human melanoma, grafted intradermally in the nude mice flank, leucurogin (7.5 μg/kg in alternate days during 17 days) inhibits tumor growth by more than 40%. Leucurogin can be considered a promising agent for melanoma treatment.

Tumor angiogenesis and anti-angiogenic gene therapy for cancer

When Folkman first suggested a theory about the association between angiogenesis and tumor growth in 1971, the hypothesis of targeting angiogenesis to treat cancer was formed. Since then, various studies conducted across the world have additionally confirmed the theory of Folkman, and numerous efforts have been made to explore the possibilities of curing cancer by targeting angiogenesis. Among them, anti-angiogenic gene therapy has received attention due to its apparent advantages. Although specific problems remain prior to cancer being fully curable using anti-angiogenic gene therapy, several methods have been explored, and progress has been made in pre-clinical and clinical settings over previous decades. The present review aimed to provide up-to-date information concerning tumor angiogenesis and gene delivery systems in anti-angiogenic gene therapy, with a focus on recent developments in the study and application of the most commonly studied and newly identified anti-angiogenic candidates for anti-angiogenesis gene therapy, including interleukin-12, angiostatin, endostatin, tumstatin, anti-angiogenic metargidin peptide and endoglin silencing.

Gene therapy for patients with advanced solid tumors: a phase I study using gene electrotransfer to muscle with the integrin inhibitor plasmid AMEP

BACKGROUND

Gene electrotrotransfer describes the use of electric pulses to transfer DNA to cells. Particularly skeletal muscle has potential for systemic secretion of therapeutic proteins. Gene electrotransfer to muscle using the integrin inhibitor plasmid AMEP (Antiangiogenic MEtargidin Peptide) was investigated in a phase I dose escalation study. Primary objective was safety.

MATERIAL AND METHODS

Patients with metastatic or locally advanced solid tumors, without further standard treatments available, were treated with once-only gene electrotransfer of plasmid AMEP to the femoral muscle. Safety was monitored by adverse events registration, visual analog scale (VAS) after procedure and magnetic resonance imaging (MRI) of treated muscles. Pharmacokinetics of plasmid AMEP in plasma and urine was determined by quantitative polymerase chain reaction. Response was evaluated by positron emission tomography-computed tomography (PET-CT) scans.

RESULTS

Seven patients were enrolled and treated at dose levels from 50 to 250 μg of plasmid AMEP, the study was terminated early due to cessation of plasmid production. Minimal systemic toxicity was observed and only transient mild pain was associated with the delivery of the electric pulses. MRI of the treated muscles revealed discrete intramuscular edema 24 h after treatment. The changes in the muscle tissue resolved within 2 weeks after treatment. Peak concentrations of plasmid AMEP was detected only in plasma within the first 24 hours after injection. Protein AMEP could not be detected, which could be due to the limit of detection. No objective responses were seen.

CONCLUSIONS

Gene electrotransfer of plasmid AMEP was found to be safe and tolerable. No objective responses were observed but other DNA drugs may be tested in the future using this procedure.

Fine Tuning Cell Migration by a Disintegrin and Metalloproteinases

Cell migration is an instrumental process involved in organ development, tissue homeostasis, and various physiological processes and also in numerous pathologies. Both basic cell migration and migration towards chemotactic stimulus consist of changes in cell polarity and cytoskeletal rearrangement, cell detachment from, invasion through, and reattachment to their neighboring cells, and numerous interactions with the extracellular matrix. The different steps of immune cell, tissue cell, or cancer cell migration are tightly coordinated in time and place by growth factors, cytokines/chemokines, adhesion molecules, and receptors for these ligands. This review describes how a disintegrin and metalloproteinases interfere with several steps of cell migration, either by proteolytic cleavage of such molecules or by functions independent of proteolytic activity.

Pancreatic Cancer Metastases Harbor Evidence of Polyclonality

Studies of the cancer genome have demonstrated that tumors are composed of multiple subclones with varied genetic and phenotypic properties. However, little is known about how metastases arise and evolve from these subclones. To understand the cellular dynamics that drive metastasis, we used multicolor lineage-tracing technology in an autochthonous mouse model of pancreatic cancer. Here, we report that precursor lesions exhibit significant clonal heterogeneity but that this diversity decreases during premalignant progression. Furthermore, we present evidence that a significant fraction of metastases are polyclonally seeded by distinct tumor subclones. Finally, we show that clonality during metastatic growth-leading to either monoclonal or polyclonal expansion-differs based on the site of metastatic invasion. These results provide an unprecedented window into the cellular dynamics of tumor evolution and suggest that heterotypic interactions between tumor subpopulations contribute to metastatic progression in native tumors.

SIGNIFICANCE

Studies of tumor heterogeneity indicate that distinct tumor subclones interact during cancer progression. Here, we demonstrate by lineage tracing that metastases often involve seeding by more than one clone and that subsequent cellular outgrowth depends on the metastatic site. These findings provide insight into clonal diversity and evolution in metastatic disease.

rAdinbitor, a disintegrin from Agkistrodon halys brevicaudus stejneger, inhibits tumorigenicity of hepatocarcinoma via enhanced anti-angiogenesis and immunocompetence

Adinbitor is a disintegrin previously obtained from Agkistrodon halys brevicaudus stejneger by our group. Here, we investigated the in vitro and in vivo anti-tumor activities of recombinant Adinbitor (rAdinbitor). rAdinbitor stimulation can inhibit the in vitro proliferation, migration and invasion capacities of murine hepatocarcinoma H22 and Hca-F cells. The administrations of rAdinbitor either by gavage or intraperitoneal injection suppress the tumor malignancy and prolong the survival rate and time of H22-transplanted mice. The number and size of formed blood vessels decreased dramatically in tumorous tissues in that the expression levels of vascular endothelial growth factor (VEGF) and cluster of differentiation 34 (CD34) were significantly decreased in responding to rAdinbitor treatment. The protein levels of IL-18 and IgG increased significantly in the serum of H22-transplanted tumor mice with rAdinbitor treatment. rAdinbitor shows in vitro and in vivo anti-tumor effects as an angiogenesis inhibitor and immunocompetence enhancer.

Antitumor and anti-angiogenic activity of the recombinant human disintegrin domain of A disintegrin and metalloproteinase 15

A disintegrin and metalloproteinases (ADAMs), a family of transmembrane glycoproteins, are expressed in numerous tissues and organs, and have been implicated in a variety of physiological and pathological processes. ADAM15 is unique among the ADAMs in having an Arg-Gly-Asp motif in its disintegrin domain. In the present study, the antitumor and anti-angiogenic effects of the recombinant human disintegrin domain (rhdd) ADAM15, expressed by Escherichia coli, were evaluated. rhddADAM15 inhibited the proliferation and migration of several tumor cells, with a half maximal inhibitory concentration of 1.0-6.0 µM. In addition, rhddADAM15 inhibited the proliferation of Bel-7402 cells via the mitogen-activated protein kinase pathway and reduced the activation of Src. rhddADAM15 (1-10 µM) inhibited the proliferation, migration and tube formation of vascular endothelial EA.hy926 cells. G0/G1 arrest (10.96 ± 1.40%) and apoptotic cells (55.85 ± 1.06%) were observed in the EA.hy926 cells treated with 4 µM and 6 µM rhddADAM15, respectively. In vivo, rhddADAM15 significantly inhibited angiogenesis in zebrafish. rhddADAM15 at concentrations of 20 nmol/fish or 5 nmol/fish inhibited the angiogenesis of subintestinal and intersegmental vessels in the zebrafish by 72 ± 1.26 and 48 ± 2.92%, respectively. In conclusion, the results of the present study identified rhddADAM15 as a potent inhibitor of tumor formation and angiogenesis, rendering it a promising tool for use in anticancer treatment.

Gene electrotransfer of plasmid AMEP, an integrin-targeted therapy, has antitumor and antiangiogenic action in murine B16 melanoma

Gene therapy with Plasmid AMEP (antiangiogenic metargidin peptide) has recently been studied as a potential targeted therapy for melanoma. This plasmid is designed to downregulate α5β1 and αvβ3 integrins. In our study, electroporation was used as a nonviral delivery system. We investigated the antiangiogenic and direct antitumor effectiveness of this gene therapy on low and highly metastatic B16 melanoma variants. In vitro, the antiangiogenic effectiveness as determined by tube formation assay on endothelial cells was predominantly dependent on AMEP expression levels. In vivo, antitumor effectiveness was mediated by the inhibition of proliferation, migration and invasion of melanoma cells and correlated with the expression of integrins on tumor cells after intratumor delivery. In addition, reduced metastatic potential was shown. Intramuscular gene electrotransfer of Plasmid AMEP, for AMEP systemic distribution, had no antitumor effect with this specific preventive treatment protocol, confirming that direct tumor delivery was more effective. This study confirms our previous in vitro data that the expression levels of integrins on melanoma cells could be used as a biomarker for antitumor effectiveness in integrin-targeted therapies, whereas the expression levels of AMEP peptide could be a predictive factor for antiangiogenic effectiveness of Plasmid AMEP in the treatment of melanoma.

Antiangiogenic Metargidin Peptide (AMEP) Gene Therapy in Disseminated Melanoma

Gene delivery by electroporation is an efficient method for transfecting genes into various tissues including tumors. Here we present the treatment protocol used in a phase 1 study on gene electrotransfer of plasmid DNA encoding an antiangiogenic peptide into cutaneous melanoma.

Cross-drug resistance to sunitinib induced by doxorubicin in endothelial cells

Multiple drug resistance remains an unsolved problem in cancer therapy. A previous study has demonstrated that the chemotherapeutic drug doxorubicin (Dox) induced upregulation of P-glycoprotein in endothelial cells, resulting in a 20-fold increase in drug resistance and reduced efficiency of doxorubicin treatment in a mouse tumor model. In the present study, the cross-resistance and sensitivity of HMECd1 and HMECd2 established cell lines to anti-angiogenic drugs, particularly sunitinib, was explored. The results revealed that Dox treatment induced a significant increase in the breast cancer resistance protein (ABCG2) gene transcription and protein expression. This increase gave rise to a 4- to 5-fold increase in the half maximal inhibitory concentration of the HMECd1 and HMECd2 cells in response to sunitinib treatment in vitro. Functionally, the role of ABCG2 in the resistance to sunitinib was confirmed by the use of the ABCG2 inhibitors fumitremorgin C and diethylstilbestrol, which blocked cell resistance. The present study indicates that endothelial cells exhibit cross-resistance between cytotoxic drugs and anti-angiogenic drugs. This suggests that multiple drug resistance induced by chemotherapy in endothelial cells may affect the efficiency of anti-angiogenic drugs.

Induction of multiple drug resistance in HMEC-1 endothelial cells after long-term exposure to sunitinib

Multiple drug resistance is still an unsolved problem in cancer therapy. Our previous study demonstrated that the chemotherapeutic drug doxorubicin (Dox) induced upregulation of P-glycoprotein (P-gp) in endothelial cells, resulting in a 20-fold increase in drug resistance and reduced efficiency of Dox treatment in a mice tumor model. In this study, we exposed human microvascular endothelial cells (HMEC-1) to sunitinib, a tyrosine kinase receptor inhibitor, to induce drug resistance. The results show that sunitinib treatment induced multiple drug resistance in these cells. They became resistant not only to sunitinib but also to Dox, paclitaxel, and vinblastine. Significant increases in P-gp (9.3-fold), ABCG2 (breast cancer resistance protein, 1.9-fold), and multidrug resistance-associated protein 1 (2.7-fold) gene transcription were found by quantitative polymerase chain reaction quantification, and their protein expression was confirmed by Western blot. These increases gave rise to an approximately five-fold increase in half maximal inhibitory concentration in these cells in response to sunitinib treatment in vitro. The inhibitors of adenosine triphosphate-binding cassette transporters did not reverse the drug resistance in sunitinib-resistant HMEC-1 cells, assumedly because of a blockage of the pump function caused by sunitinib. Our study indicates that the antiangiogenic drug sunitinib induces multiple drug resistance in endothelial cells. The induction of adenosine triphosphate-binding cassette transporters seems not to be responsible for observed multiple drug resistance, and the underlying mechanisms remain unknown.

Gene electrotransfer of plasmid antiangiogenic metargidin peptide (AMEP) in disseminated melanoma: safety and efficacy results of a phase I first-in-man study

Antiangiogenic metargidin peptide (AMEP) is a novel anticancer agent exerting antiproliferative and antiangiogenic effects by binding to αvβ3 and α5β1 integrins. Electrotransfer designates the use of electric pulses (electroporation) to transfer plasmid DNA into tissues. This first-in-man phase I study investigated safety and tolerability of intratumoral plasmid AMEP electrotransfer into cutaneous metastatic melanoma. Secondary objectives were efficacy and pharmacokinetics. Five patients with disseminated melanoma without further treatment options were treated at two dose levels (1 and 2 mg DNA). In each patient, two cutaneous lesions were identified (one treated and one control). At day 1 and day 8, plasmid AMEP was injected intratumorally followed by electrotransfer. Patients were monitored weekly until day 29, and at day 64. Local efficacy was assessed at day 29 by direct measurement, and posttreatment biopsies for AMEP mRNA levels were evaluated by reverse transcriptase quantitative polymerase chain reaction. Plasmid copy number in blood and urine was determined by quantitative polymerase chain reaction. Minimal systemic toxicity was observed, including transient fever and transitory increase in C-reactive protein. No related serious adverse events occurred. Plasmid AMEP was detected in plasma but not in urine. AMEP mRNA was found in three of five treated lesions and none of the control lesions. At day 29, all five treated lesions were stable in diameter, whereas four of five control lesions increased more than 20%. No response occurred in distant lesions. This first-in-man study on electrotransfer of plasmid AMEP into cutaneous melanoma shows that the procedure and drug are safe and that local transfection was obtained.

Metalloproteinases in melanoma

Tumour cell adhesion, motility, proteolytic activities and cell receptors have important roles in cancer invasion. These processes are involved from early development of melanoma within the epidermis, to tumour cell invasion of the underlying tissue until intravasation of lymphatic or blood vessels, and thereafter, dissemination into distant organs occur. The activity of several proteolytic enzymes was shown to be pivotal in promoting melanoma cell invasion. These enzymes not only remodel the extracellular matrix, but also release active factors and shed cell surface receptors thereby mediating melanoma cross-communication with their microenvironment. This leads to the generation of a favourable environment for melanoma growth. Several proteases are involved in melanoma invasion and include serine, cysteine proteases, matrix metalloproteases (MMPs) and the disintegrin and metalloproteases (ADAMs). This study summarises the current knowledge on the role of metalloproteinases, MMPs and ADAMs, in melanoma.

Helping Eve overcome ADAM: G-quadruplexes in the ADAM-15 promoter as new molecular targets for breast cancer therapeutics

ADAM-15, with known zymogen, secretase, and disintegrin activities, is a catalytically active member of the ADAM family normally expressed in early embryonic development and aberrantly expressed in various cancers, including breast, prostate and lung. ADAM-15 promotes extracellular shedding of E-cadherin, a soluble ligand for the HER2/neu receptor, leading to activation, increased motility, and proliferation. Targeted downregulation of both ADAM-15 and HER2/neu function synergistically kills breast cancer cells, but to date there are no therapeutic options for decreasing ADAM-15 function or expression. In this vein, we have examined a unique string of guanine-rich DNA within the critical core promoter of ADAM-15. This region of DNA consists of seven contiguous runs of three or more consecutive guanines, which, under superhelical stress, can relax from duplex DNA to form an intrastrand secondary G-quadruplex (G4) structure. Using biophysical and biological techniques, we have examined the G4 formation within the entire and various truncated regions of the ADAM-15 promoter, and demonstrate strong intrastrand G4 formation serving to function as a biological silencer element. Characterization of the predominant G4 species formed within the ADAM-15 promoter will allow for specific drug targeting and stabilization, and the further development of novel, targeted therapeutics.

Induction of acquired drug resistance in endothelial cells and its involvement in anticancer therapy

BACKGROUND

Multidrug resistance (MDR) is one of the major problems in the treatment of cancer. Overcoming it is therefore expected to improve clinical outcomes for cancer patients. MDR is usually characterized by overexpression of ABC (ATP-binding cassette) protein transporters such as P-gp, MRP1, and ABCG2. Though the importance of ABC transporters for cancer cells is recognized, few studies have looked at its implications for the endothelial cells that are essential to tumor angiogenesis. This study investigated the expression and functions of these ABC transporters in endothelial cells in vitro and their potential contribution to cancer growth in mice.

METHODS

Human micro vessel endothelial cells (HMEC-1) and human umbilical vein endothelial cells (HUVEC) were exposed to increasing doses of Doxorubicin (Dox) to induce ABC gene expression. Cell viability was then quantified by (3)H-thymidine and MTS assay. Flow cytometry, qPCR, and western blot were used to detect mRNA and the protein expression of P-gp, MRP1, and ABCG2. The intracellular accumulation of Rhodamine 123 (Rho) was used to evaluate drug efflux function and the inhibitors for P-gp, ABCG2, and MRP1 were used to verify their respective roles in vitro. In an attempt to evaluate drug resistance in endothelial cells in vivo, athymic mice were treated with Dox for 15 days before a MDA-MB-435 tumor graft to observe subsequent changes in the inhibition curves of tumor growth in response to Dox treatment. Furthermore, endothelial cells from multiple sites in these mice were also isolated to estimate their P-gp expression by flow cytometry.

RESULTS

Drug resistance in HMEC-1 and HUVEC was successfully induced by the addition of Dox to the culture media. Two stabilized subcell lines of HMEC1 (HMECd1 and HMECd2) showed 15- and 24-fold increases in resistance. Tests also showed that these induced endothelial cells were cross-resistant to the structurally unrelated drugs Daunorubicin, Vinblastine, and Etoposide. P-gp protein levels increased four and six fold in HMECd1 and HMECd2 as revealed by western blot. The qPCR demonstrated 3.4- and 7.2-fold increases in P-gp, and a slight increase in ABCG2, gene expression. The Rho accumulation within these cells was inversely correlated with the expression levels of P-gp. The inhibitors of P-gp, but not of ABCG2 or MRP1, were able to block the induced endothelial cell resistance to Dox. Furthermore, we also showed that injecting Dox into healthy mice induced an increase in P-gp expression in endothelial cells. Using these pretreated mice in a tumor growth experiment, we observed a dramatic diminution in the therapeutic efficiency of Dox treatment, suggesting implications for drug resistance in mice endothelial cells supporting tumor growth.

CONCLUSIONS

ABC transporter expression can be induced in endothelial cells in vitro. This study also indicates that P-gp plays an important role in the acquisition of resistance to Dox in endothelial cells and that this reduces the efficiency of chemotherapy.

Recombinant disintegrin domain of ADAM15 inhibits the proliferation and migration of Bel-7402 cells

ADAM15 (A Disintegrin And Metalloproteinase 15), a transmembrane protein containing seven domains, interacts with some integrins via its disintegrin domain and overexpresses in many solid tumors. In this study, the effect of the recombinant human disintegrin domain (rhddADAM15) on the proliferation and migration of Bel-7402 cells was evaluated in vitro and in vivo in zebrafish xenografts. rhddADAM15 (4 μM) severely inhibited the proliferation and migration of Bel-7402 cells, inducing a partial G2/S arrest and morphological nucleus changes of apoptosis. Moreover, the activity of caspases 8, 9 and 3 in Bel-7402 cells was increased. In addition, the zebrafish was used as a model for apoptosis-induction and tumor-xenograft. rhddADAM15 (1 pM) inhibited the growth and metastasis of Bel-7402 cell xenografts in zebrafish and a lower concentration (0.1 pM) induced severe apoptosis in the somatic cells of zebrafish. In conclusion, our data identified rhddADAM15 as a potent inhibitor of tumor growth and metastasis, making it a promising tool for use in anticancer treatment.

Biological properties of melanoma and endothelial cells after plasmid AMEP gene electrotransfer depend on integrin quantity on cells

The data on the biological responsiveness of melanoma and endothelial cells that are targeted by Antiangiogenic MEtargidin Peptide (AMEP) are limited; therefore, the antiproliferative, antimetastatic and antiangiogenic effects of AMEP were investigated in murine melanoma and human endothelial cells after plasmid AMEP gene electrotransfer into the cells in vitro. Plasmid AMEP, a plasmid coding for the disintegrin domain of metargidin targeting specific integrins, had cytotoxic and antiproliferative effects on murine melanoma and human endothelial cells. Among the metastatic properties of cells, migration, invasion and adhesion were investigated. Plasmid AMEP strongly affected the migration of murine melanoma and human endothelial cell lines and also affected the invasion of highly metastatic murine melanoma B16F10 and human endothelial cell lines. There was no effect on cell adhesion on Matrigel(TM) or fibronectin in all cell lines. The antiangiogenic effect was shown with tube formation assay, where human microvascular endothelial cell line (HMEC-1) proved to be more sensitive to plasmid AMEP gene electrotransfer than the human umbilical vein endothelial cell line (HUVEC). The study indicates that antiproliferative and antimetastatic biological responses to gene electrotransfer of plasmid AMEP in murine melanoma cells were dependent on the integrin quantity on melanoma cells and not on the expression level of AMEP. The strong antiangiogenic effect expressed in human endothelial cell lines was only partly dependent on the quantity of integrins and seemed to be plasmid AMEP dose dependent.

Insights into the Transforming Growth Factor-β Signaling Pathway in Cutaneous Melanoma

Transforming growth factor-β (TGF-β) is a pleiotropic growth factor with broad tissue distribution that plays critical roles during embryonic development, normal tissue homeostasis, and cancer. While its cytostatic activity on normal epithelial cells initially defined TGF-β signaling as a tumor suppressor pathway, there is ample evidence indicating that TGF-β is a potent pro-tumorigenic agent, acting via autocrine and paracrine mechanisms to promote peri-tumoral angiogenesis, together with tumor cell migration, immune escape, and dissemination to metastatic sites. This review summarizes the current knowledge on the implication of TGF-β signaling in melanoma.

A new anti-tumor strategy based on in vivo tumstatin overexpression after plasmid electrotransfer in muscle

The NC1 domains from the different α(IV) collagen chains were found to exert anti-tumorigenic and/or anti-angiogenic activities. A limitation to the therapeutic use of these matrikines is the large amount of purified recombinant proteins, in the milligram range in mice that should be administered daily throughout the experimental procedures. In the current study, we developed a new therapeutic approach based on tumstatin (NC1α3(IV)) overexpression in vivo in a mouse melanoma model. Gene electrotransfer of naked plasmid DNA (pDNA) is particularly attractive because of its simplicity, its lack of immune responsiveness and its safety. The pDNA electrotransfer in muscle mediates a substantial gene expression that lasts several months. A pVAX1© vector containing the tumstatin cDNA was injected into the legs of C57BL/6 mice and submitted to electrotranfer. Sera were collected at different times and tumstatin was quantified by ELISA. Tumstatin secretion reached a plateau at day 21 with an expression level of 12 μg/mL. For testing the effects of tumstatin expression on tumor growth in vivo, B16F1 melanoma cells were subcutaneously injected in mice 7 days after empty pVAX1© (Mock) or pVAX1©-tumstatin electrotransfer. Tumstatin expression triggered a large decrease in tumor growth and an increase in mouse survival. This new therapeutic approach seems promising to inhibit tumor progression in vivo.

What you always needed to know about electroporation based DNA vaccines

Vaccinations are increasingly used to fight infectious disease, and DNA vaccines offer considerable advantages, including broader possibilities for vaccination and lack of need for cold storage. It has been amply demonstrated, that electroporation augments uptake of DNA in both skin and muscle, and it is foreseen that future DNA vaccination may to a large extent be coupled with and dependent upon electroporation based delivery. Understanding the basic science of electroporation and exploiting knowledge obtained on optimization of DNA electrotransfer to muscle and skin, may greatly augment efforts on vaccine development. The purpose of this review is to give a succinct but comprehensive overview of electroporation as a delivery modality including electrotransfer to skin and muscle. As well, this review will speculate and discuss future uses for this powerful electrotransfer technology.

Recombinant rubistatin (r-Rub), an MVD disintegrin, inhibits cell migration and proliferation, and is a strong apoptotic inducer of the human melanoma cell line SK-Mel-28

Disintegrins are low molecular weight peptides isolated from viper venom. These peptides bind to integrin receptors using a conserved binding motif sequence containing an RGD or similar motif. As a consequence, disintegrins can inhibit platelet aggregation and inhibit cell migration, proliferation, and initiate apoptosis in cancer cell lines. Rubistatin is a MVD disintegrin cloned from a Crotalus ruber ruber venom gland. The biological activity of MVD disintegrins is poorly understood. Recombinant rubistatin (r-Rub) was cloned into a pET32b plasmid and expressed in reductase-deficient Escherichia coli. Expression was induced with IPTG and the resulting fusion peptide was affinity purified, followed by thrombin cleavage, and removal of vector coded sequences. r-Rub peptide inhibited ADP-induced platelet aggregation by 54% ± 6.38 in whole blood. We assessed the ability of r-Rub to initiate apoptosis in three human cancer cell lines. Cultures of SK-Mel-28, HeLA, and T24 cells were grown for 24 h with 2.5 μM r-Rub followed by Hoechst staining. Chromatin fragmentation was observed in treated SK-Mel-28, but not in T24 or HeLA cells. A TUNEL assay revealed that 51.55% ± 5.28 of SK-Mel-28 cells were apoptotic after 18 h of treatment with 3.5 μM of r-Rub. Cell migration and proliferation assays were performed in order to further characterize the biological effects of r-Rub on SK-Mel-28 cells. At 3 μM, r-Rub inhibited cell migration by 44.4% ± 0.5, while at 3.5 μM it was able to inhibit cell proliferation by 83% ± 6.0.

Antitumoral and antimetastatic effect of antiangiogenic plasmids in B16 melanoma: Higher efficiency of the recombinant disintegrin domain of ADAM 15

BACKGROUND

Despite the discovery of novel inhibitors of tumor angiogenesis, protein-based antiangiogenic cancer therapy suffers some limitations that antiangiogenic gene therapy could overcome. We investigated whether intra-tumoral electrotransfer of three angiogenic plasmids could inhibit tumor growth and metastasis.

METHODS

Plasmids encoding recombinant disintegrin domain of ADAM-15 (RDD), thrombospondin 1 (TSP-1), and the soluble isoform of the VEGF receptor 1 (sFlt-1) were injected into B16F10 melanoma-bearing C57BL/6 mice followed by electroporation. Tumor volume was measured daily using a digital caliper. Metastasis was monitored by in vivo bioluminescence after surgical removal of the primary luciferase-encoding B16F10 tumor 5 days after intra-tumoral electrotransfer. Markers of vascularization and cell proliferation were quantified by immunohistochemistry.

RESULTS

Intra-tumoral electrotransfer of the antiangiogenic plasmids induced a significant inhibition of tumor growth, doubling of mean survival time and long-term survivors (∼40% vs 0% in control). When the tumor was removed by surgery after intra-tumoral plasmid electrotransfer, a significant decrease in tumor metastasis was observed leading to long-term tumor-free survival especially after treatment with pRDD plasmid (84% vs 0% in control). Unlike pTSP-1 and psFlt-1, pRDD significantly decreased cell proliferation in B16F10 primary tumors which express αvβ3 and α5β1 integrins. No effect of antiangiogenic plasmid electrotransfer on normal skin blood flow was detected.

CONCLUSION

The intra-tumoral electrotransfer of the three antiangiogenic plasmids is a promising method for the treatment of melanoma. The plasmid encoding RDD seems to be particularly effective due to its direct antitumoral activity combined with angiogenesis suppression, and its marked inhibition of metastasis.

Antivascular effects of electrochemotherapy: implications in treatment of bleeding metastases

Solid tumors of various etiologies can be treated efficiently by electrochemotherapy (ECT), a combined use of electroporation (EP) and chemotherapeutic drugs, such as bleomycin and cisplatin. EP alone and ECT in particular, induce a profound reduction in tumor blood flow, which contributes to the antitumor effect. After EP and ECT, the time course of blood flow changes and follows the same two-phase pattern. The first rapid and short-lived vasoconstriction phase is followed by the second much longer-lived phase resulting from disrupted cytoskeletal structures and a compromised barrier function of the microvascular endothelium. In the case of ECT, however, tumor vascular endothelial cells are also affected by the chemotherapeutic drug, which leads to irrecoverable damage to tumor vessels and to a further decrease in tumor blood flow within hours after application of ECT. Tumor cells surviving the direct effects of ECT are consequently exposed to lack of oxygen and nutrients and are pushed into the secondary cascade of induced cell death. Clinically, the antitumor effectiveness of ECT has been proven extensively in the treatment of melanoma metastases, with 70-80% complete responses. The antivascular effects of ECT were also exploited for palliative treatment of bleeding melanoma metastases, with immediate cessation of bleeding and very good antitumor effectiveness. The antivascular effect of ECT is of utmost importance for translation of ECT into the treatment of deep-seated tumors, especially in well vascularized organs, such as the liver, where it prevents bleeding of the treated area.

Halting angiogenesis by non-viral somatic gene therapy alleviates psoriasis and murine psoriasiform skin lesions

Dysregulated angiogenesis is a hallmark of chronic inflammatory diseases, including psoriasis, a common skin disorder that affects approximately 2% of the population. Studying both human psoriasis in 2 complementary xenotransplantation models and psoriasis-like skin lesions in transgenic mice with epidermal expression of human TGF-β1, we have demonstrated that antiangiogenic non-viral somatic gene therapy reduces the cutaneous microvasculature and alleviates chronic inflammatory skin disorders. Transient muscular expression of the recombinant disintegrin domain (RDD) of metargidin (also known as ADAM-15) by in vivo electroporation reduced cutaneous angiogenesis and vascularization in all 3 models. As demonstrated using red fluorescent protein-coupled RDD, the treatment resulted in muscular expression of the gene product and its deposition within the cutaneous hyperangiogenic connective tissue. High-resolution ultrasound revealed reduced cutaneous blood flow in vivo after electroporation with RDD but not with control plasmids. In addition, angiogenesis- and inflammation-related molecular markers, keratinocyte proliferation, epidermal thickness, and clinical disease scores were downregulated in all models. Thus, non-viral antiangiogenic gene therapy can alleviate psoriasis and may do so in other angiogenesis-related inflammatory skin disorders.

Snake venom disintegrins and cell migration

Cell migration is a key process for the defense of pluricellular organisms against pathogens, and it involves a set of surface receptors acting in an ordered fashion to contribute directionality to the movement. Among these receptors are the integrins, which connect the cell cytoskeleton to the extracellular matrix components, thus playing a central role in cell migration. Integrin clustering at focal adhesions drives actin polymerization along the cell leading edge, resulting in polarity of cell movement. Therefore, small integrin-binding proteins such as the snake venom disintegrins that inhibit integrin-mediated cell adhesion are expected to inhibit cell migration. Here we review the current knowledge on disintegrin and disintegrin-like protein effects on cell migration and their potential use as pharmacological tools in anti-inflammatory therapy as well as in inhibition of metastatic invasion.

The mojastin mutant Moj-DM induces apoptosis of the human melanoma SK-Mel-28, but not the mutant Moj-NN nor the non-mutated recombinant Moj-WN

In this study, three recombinant mojastin peptides (Moj-WN, Moj-NN, and Moj-DM) were produced and compared functionally. Recombinant Moj peptides were purified as GST-fusions. GST-Moj-WN and GST-Moj-NN inhibited ADP-induced platelet aggregation in platelet rich plasma. The GST-Moj-WN had an IC(50) of 160nM, while the GST-Moj-NN had an IC(50) of 493nM. The GST-Moj-DM did not inhibit platelet aggregation. All three GST-Moj peptides inhibited SK-Mel-28 cell adhesion to fibronectin. The GST-Moj-WN inhibited the binding of SK-Mel-28 cells to fibronectin with an IC(50) of 11nM, followed by the GST-Moj-NN (IC(50) of 28nM), and the GST-Moj-DM (IC(50) of 46nM). The GST-Moj peptides' ability to induce apoptosis on SK-Mel-28 cells was determined using Annexin-V-FITC and nuclear fragmentation assays. Cells were incubated with 5muM GST-Moj peptides for 24h. At 5microM GST-Moj-DM peptide, 13.56%+/-2.08 of treated SK-Mel-28 cells were in early apoptosis. The GST-Moj-DM peptide also caused nuclear fragmentation as determined by fluorescent microscopy and Hoechst staining. The GST-Moj-WN and GST-Moj-NN peptides failed to induce apoptosis. We characterized the SK-Mel-28 integrin expression, as the first step in determining r-Moj binding specificity. Our results indicate that SK-Mel-28 cells express alphavbeta3, alphav, alpha6, beta1, and beta3 integrin receptors.

Secreted and membrane-bound isoforms of protease ADAM9 have opposing effects on breast cancer cell migration

Tumor cell migration is mediated by cell-autonomous signaling mechanisms as well as paracrine and autocrine factors secreted by activated stromal cells in the tumor microenvironment. Like other members of the ADAM (a disintegrin and metalloproteinase) family, the integrin-binding metalloproteinase ADAM9 modulates cell-cell and cell-matrix interactions as well as ectodomain shedding of cell surface receptors and ligands, thereby modifying intracellular and extracellular signaling. ADAM9 transcripts are alternatively spliced to express a transmembrane protein (ADAM9-L) and a secreted variant (ADAM9-S). In this study, we show that ADAM9-S promotes breast cancer cell migration in a manner requiring its metalloproteinase activity, whereas ADAM9-L suppresses cell migration independent of its metalloproteinase activity. Suppression of migration by ADAM9-L requires a functional disintegrin domain and integrin binding. Expression analysis revealed that both ADAM9 isoforms are expressed in breast cancer cell lines and tissues. Therefore, relative levels of membrane-tethered and secreted variants of ADAM9 are a key determinant in manifestation of aggressive migratory phenotypes associated with breast cancer progression.

Therapeutic levels of erythropoietin (EPO) achieved after gene electrotransfer to skin in mice

Gene electrotransfer refers to gene transfection by electroporation and is an effective non-viral method for delivering naked DNA into cells and tissues. This study presents data from gene electrotransfer with erythropoietin (EPO) to mouse skin. Nine-week-old female NMRI mice received one, two or three intradermal injections of 50 microg EPO plasmid and were subsequently electroporated. With plate electrodes and 100 microg of EPO, a significant increase in hemoglobin (P<0.01) was observed compared with controls. The level of hemoglobin peaked after 5 weeks but stayed significantly elevated for more than 3 months. Serum EPO was significantly increased (P<0.001) 24 h after the transfection and remained significantly different compared with controls until the maximum level of serum EPO was reached after 2 weeks. Eight weeks after the transfection serum EPO returned to baseline. In this study, we have established that gene electrotransfer to skin of even small amounts of DNA can lead to systemically therapeutic levels of protein. This means that in addition to DNA vaccinations, there is a potential utility for electroporation in alleviating systemic diseases such as cancer and protein deficiency disorders.

Gene expression analysis of drug-resistant MCF-7 cells: implications for relation to extracellular matrix proteins

PURPOSE

Since multidrug resistance is a multifactorial phenomenon, a large-scale expression analysis of drug-resistant cells by using high-density oligonucleotide microarrays may provide information about new candidate genes contributing to resistance. Extracellular matrix (ECM) is responsible for many aspects of proliferation and invasive/metastatic behavior of tumor cells. This study demonstrates alterations in gene expression levels of several ECM components, matrix metalloproteinases (MMPs), adamalysins (ADAMs and ADAMTSs) and tissue inhibitors of metalloproteinases (TIMPs) in paclitaxel, docetaxel, vincristine and doxorubicin-resistant MCF-7 cells.

METHODS

Resistant MCF-7 cells were developed by stepwise selection of cells in increasing concentrations of drugs. Affymetrix GeneChip Human Genome U133 Plus 2.0 Array was used for hybridizations. Statistical significance was determined by independent sample t test. The genes having altered expression levels in drug-resistant sublines were selected and filtered by volcano plots.

RESULTS

Genes up/downregulated more than twofolds were selected and listed. Expression of 25 genes encoding ECM proteins (including collagen, finronectin and syndecan) and integrin receptor subunits were found to be upregulated in drug-resistant cells. In addition, expression levels of, 13 genes encoding MMPs, ADAMs, ADAMTSs and TIMPs (including MMP1, MMP9, ADAM9 and TIMP3) were found to be altered in drug-resistant sublines when compared with sensitive MCF-7.

CONCLUSIONS

Based on the expression analysis profiles, this report provides a preliminary insight into the relationship between drug resistance and ECM components, which are related to invasion and metastasis. Correlation of each specific ECM component with drug resistance requires further analysis.

ADAM-17 regulates endothelial cell morphology, proliferation, and in vitro angiogenesis

Modulation of angiogenesis is a promising approach for treating a wide variety of human diseases including ischemic heart disease and cancer. In this study, we show that ADAM-17 is an important regulator of several key steps during angiogenesis. Knocking down ADAM-17 expression using lentivirus-delivered siRNA in HUVECs inhibited cell proliferation and the ability of cells to form close contact in two-dimensional cultures. Similarly, ADAM-17 depletion inhibited the ability of HUVECs to form capillary-like networks on top of three-dimensional Matrigel as well as in co-culture with fibroblasts within a three-dimensional scaffold. In mechanistic studies, both baseline and VEGF-induced MMP-2 activation and Matrigel invasion were inhibited by ADAM-17 depletion. Based on our findings we propose that ADAM-17 is part of a novel pro-angiogenic pathway leading to MMP-2 activation and vessel formation.

Proteases and bone remodelling

Bone remodelling is regulated by osteogenic cells which act individually through cellular and molecular interaction. These interactions can be established either through a cell-cell contact, involving molecules of the integrin family, or by the release of many polypeptidic factors and/or their soluble receptor chains. Proteolytic shedding of membrane-associated proteins regulates the physiological activity of numerous proteins. Proteases located on the plasma membrane, either as transmembrane proteins or anchored to cell-surface molecules, serve as activators or inhibitors of different cellular and physiological processes. This review will focus on the role of the proteases implicated in bone remodelling either through the proteolytic degradation of the extracellular matrix or through their relations with osteogenic factors. Their implication in bone tumor progression will be also considered.

The ADAM metalloproteinases

The ADAMs (a disintegrin and metalloproteinase) are a fascinating family of transmembrane and secreted proteins with important roles in regulating cell phenotype via their effects on cell adhesion, migration, proteolysis and signalling. Though all ADAMs contain metalloproteinase domains, in humans only 13 of the 21 genes in the family encode functional proteases, indicating that at least for the other eight members, protein–protein interactions are critical aspects of their biological functions. The functional ADAM metalloproteinases are involved in “ectodomain shedding” of diverse growth factors, cytokines, receptors and adhesion molecules. The archetypal activity is shown by ADAM-17 (tumour necrosis factor-α convertase, TACE), which is the principal protease involved in the activation of pro-TNF-α, but whose sheddase functions cover a broad range of cell surface molecules. In particular, ADAM-17 is required for generation of the active forms of Epidermal Growth Factor Receptor (EGFR) ligands, and its function is essential for the development of epithelial tissues. Several other ADAMs have important sheddase functions in particular tissue contexts. Another major family member, ADAM-10, is a principal player in signalling via the Notch and Eph/ephrin pathways. For a growing number of substrates, foremost among them being Notch, cleavage by ADAM sheddases is essential for their subsequent “regulated intramembrane proteolysis” (RIP), which generates cleaved intracellular domains that translocate to the nucleus and regulate gene transcription. Several ADAMs play roles in spermatogenesis and sperm function, potentially by effecting maturation of sperm and their adhesion and migration in the uterus. Other non-catalytic ADAMs function in the CNS via effects on guidance mechanisms. The ADAM family are thus fundamental to many control processes in development and homeostasis, and unsurprisingly they are also linked to pathological states when their functions are dysregulated, including cancer, cardiovascular disease, asthma, Alzheimer’s disease. This review will provide an overview of current knowledge of the human ADAMs, discussing their structure, function, regulation and disease involvement.

Enhancement of recombinant human ADAM15 disintegrin domain expression level by releasing the rare codons and amino acids restriction

This study was aimed at increasing the production of the recombinant human ADAM15 disintegrin domain (RADD) in Escherichia coli by releasing the rare codons and restricting amino acid residues. Three different strategies for increasing RADD production were examined: to select the suitable host strain, to optimize the rare codons, and to delete the amino acids residues. The total fusion protein glutathione-S-transferase (GST)-RADD concentration of 298 mg/l and 326 mg/l were achieved by selecting E. coli Rosetta (DE3) as the host strain and by changing GGA to GGC at the GST-RADD cassette, respectively. The RADD concentration was increased by 35.7% by eliminating the "Pro-Glu-Phe" residues at the GST-RADD junction. By combinational utilizing the preferred codon introduction and amino acid sequence optimization in E. coli Rosetta (DE3), the highest RADD concentration of 68 mg/l was achieved. The proposed strategy may provide an alternative approach for other enhanced recombinant protein production by E. coli.

Critical role of ADAM15 in tumor progression: targeting multiple factors for metastasis promotion

Evaluation of: Najy AJ, Day KC, Day ML: ADAM15 supports prostate cancer metastasis by modulating tumor cell–endothelial cell interaction. Cancer Res. 68, 1092–1099 (2008). Products of a disintegrin and metalloproteinase (ADAM) gene family are multifunctional proteins and have activities of metalloproteinase, integrin-binding, cell adhesion and intracellular signaling. ADAMs play important roles in many biological processes, such as neurogenesis, myogenesis, fertilization and growth factor shedding. Several ADAM genes are also implicated in various types of cancers; however, the exact function of ADAMs in tumorigenesis and tumor progression has not been well understood. In this report, Najy and colleagues have shown that ADAM15 plays a critical role in tumor growth and metastasis in human prostate cancer. Their results indicate that ADAM15 promotes the binding to extracellular matrix proteins, expression of metastatic-associated cell surface proteins, cleavage of N-cadherin and activation of matrix metalloproteinase 9. These events were followed by stimulation of transendothelial migration and bone metastasis. Therefore, ADAM15 signaling may serve as a potential therapeutic target for prostate cancer.

The ectodomain shedding of E-cadherin by ADAM15 supports ErbB receptor activation

The zinc-dependent disintegrin metalloproteinases (a disintegrin and metalloproteinases (ADAMs) have been implicated in several disease processes, including human cancer. Previously, we demonstrated that the expression of a catalytically active member of the ADAM family, ADAM15, is associated with the progression of prostate and breast cancer. The accumulation of the soluble ectodomain of E-cadherin in human serum has also been associated with the progression of prostate and breast cancer and is thought to be mediated by metalloproteinase shedding. Utilizing two complementary models, overexpression and stable short hairpin RNA-mediated knockdown of ADAM15 in breast cancer cells, we demonstrated that ADAM15 cleaves E-cadherin in response to growth factor deprivation. We also demonstrated that the extracellular shedding of E-cadherin was abrogated by a metalloproteinase inhibitor and through the introduction of a catalytically inactive mutation in ADAM15. We have made the novel observation that this soluble E-cadherin fragment was found in complex with the HER2 and HER3 receptors in breast cancer cells. These interactions appeared to stabilize HER2 heterodimerization with HER3 and induced receptor activation and signaling through the Erk pathway, supporting both cell migration and proliferation. In this study, we provide evidence that ADAM15 catalyzes the cleavage of E-cadherin to generate a soluble fragment that in turn binds to and stimulates ErbB receptor signaling.

An Adam15 amplification loop promotes vascular endothelial growth factor-induced ocular neovascularization

Proteins with a disintegrin and a metalloproteinase domain (ADAMs) are a family of membrane-bound proteinases that bind integrins through their disintegrin domain. In this study, we have found modest expression of ADAM15 in pericytes in normal retina and strong up-regulation of ADAM15 in retinal vascular endothelial cells in ischemic retina. Increased expression of vascular endothelial growth factor (VEGF) in the retina in the absence of ischemia also increased ADAM15 levels, and knockdown of Vegf mRNA in ischemic retina reduced Adam15 mRNA. Mice deficient in ADAM15 showed a significant reduction in ischemia-induced retinal neovascularization, choroidal neovascularization at rupture sites in Bruch's membrane, and VEGF-induced subretinal neovascularization. ADAM15-deficient mice also showed reduced levels of VEGF(164), VEGF receptor 1, and VEGF receptor 2 in ischemic retina. These data suggest that ADAM15 and VEGF participate in an amplification loop; VEGF increases expression of ADAM15, which in turn increases expression of VEGF and its receptors. Perturbation of the loop by elimination of ADAM15 suppresses ocular neovascularization in 3 different model systems, and thus ADAM15 provides a new therapeutic target for diseases complicated by neovascularization.

ADAM15 supports prostate cancer metastasis by modulating tumor cell-endothelial cell interaction

Using human tumor and cDNA microarray technology, we have recently shown that the ADAM15 disintegrin is significantly overexpressed during the metastatic progression of human prostate cancer. In the current study, we used lentiviral-based short hairpin RNA (shRNA) technology to down-regulate ADAM15 in the metastatic prostate cancer cell line, PC-3. ADAM15 down-regulation dramatically attenuated many of the malignant characteristics of PC-3 cells in vitro and prevented the s.c. growth of PC-3 cells in severe combined immunodeficient (SCID) mice. By inhibiting the expression of ADAM15 in PC-3 cells, we showed decreased cell migration and adhesion to specific extracellular matrix proteins. This was accompanied by a reduction in the cleavage of N-cadherin by ADAM15 at the cell surface. Fluorescence-activated cell sorting analysis revealed reduced cell surface expression of the metastasis-associated proteins alpha(v) integrin and CD44. Furthermore, matrix metalloproteinase 9 secretion and activity were abrogated in response to ADAM15 reduction. In an in vitro model of vascular invasion, loss of ADAM15 reduced PC-3 adhesion to, and migration through, vascular endothelial cell monolayers. Using an SCID mouse model of human prostate cancer metastasis, we found that the loss of ADAM15 significantly attenuated the metastatic spread of PC-3 cells to bone. Taken together, these data strongly support a functional role for ADAM15 in prostate tumor cell interaction with vascular endothelium and the metastatic progression of human prostate cancer.

ADAM15 suppresses cell motility by driving integrin alpha5beta1 cell surface expression via Erk inactivation

Human ADAM15 is unique among the A disintegrin and metalloprotease domain (ADAM) family because of the integrin binding motif Arg-Gly-Asp (RGD) within its disintegrin domain. Integrin alpha5beta1 has been reported to bind to ADAM15 in an RGD-dependent manner, but the biological significance of the interaction between ADAM15 and alpha5beta1 is unknown. To characterize the effects of ADAM15 on alpha5beta1-mediated cell adhesion and migration and elucidate the potential mechanism, CHO cells which express endogenous integrin alpha5beta1 were transfected with human ADAM15 cDNA. ADAM15 overexpression led to enhanced cell adhesion and decreased migration on fibronectin, which were suppressed by down-regulation of integrin alpha5. Overexpression of ADAM15 not only increased the cell surface expression of integrin alpha5 but also resulted in a more clustered staining of alpha5 on cell surface, while the beta1 subunit remained unchanged. Unexpectedly, results from immunoprecipitation and immunofluorescence indicated that ADAM15 and alpha5beta1 integrin did not interact directly in CHO cells. We found that ADAM15 expression decreased the phosphorylation of Erk1/2. Consistently, down-regulation of Erk1/2 phosphorylation by MEK inhibitor PD98059 or siRNA against Erk1/2 enhanced the expression of alpha5 on cell surface. By using a B16F10 pulmonary metastasis model, we revealed that overexpression of ADAM15 significantly reduced the number of metastatic nodules on the lung. Taken together, this study reveals for the first time that ADAM15 could drive alpha5 integrin expression on cell surface via down-regulation of phosphorylated Erk1/2. This presents a novel mechanism by which ADAM15 regulates cell-matrix adhesion and migration.

Distinct functions of natural ADAM-15 cytoplasmic domain variants in human mammary carcinoma

Adamalysins [a disintegrin and metalloproteinase (ADAM)] are a family of cell surface transmembrane proteins that have broad biological functions encompassing proteolysis, adhesion, and cell signal regulation. We previously showed that the cytoplasmic domain of ADAM-15 interacts with Src family protein tyrosine kinases and the adaptor protein growth factor receptor binding protein 2 (Grb2). In the present study, we have cloned and characterized four alternatively spliced forms of ADAM-15, which differ only in their cytoplasmic domains. We show that the four ADAM-15 variants were differentially expressed in human mammary carcinoma tissues compared with normal breast. The expression of the individual isoforms did not correlate with age, menopausal status, tumor size or grade, nodal status, Nottingham Prognostic Index, or steroid hormone receptor status. However, higher levels of two isoforms (ADAM-15A and ADAM-5B) were associated with poorer relapse-free survival in node-negative patients, whereas elevated ADAM-15C correlated with better relapse-free survival in node-positive, but not in node-negative, patients. The expression of ADAM-15A and ADAM-15B variants in MDA-MB-435 cells had differential effects on cell morphology, with adhesion, migration, and invasion enhanced by expression of ADAM-15A, whereas ADAM-15B led to reduced adhesion. Using glutathione S-transferase pull-down assays, we showed that the cytoplasmic domains of ADAM-15A, ADAM-15B, and ADAM-15C show equivalent abilities to interact with extracellular signal-regulated kinase and the adaptor molecules Grb2 and Tks5/Fish, but associate in an isoform-specific fashion with Nck and the Src and Brk tyrosine kinases. These data indicate that selective expression of ADAM-15 variants in breast cancers could play an important role in determining tumor aggressiveness by interplay with intracellular signaling pathways.

Inhibition of lung tumor colonization and cell migration with the disintegrin crotatroxin 2 isolated from the venom of Crotalus atrox

Disintegrins are low molecular weight proteins (4-15 kDa) with an RGD binding region at their binding loop. Disintegrin and disintegrin-like proteins are found in the venom of four families of snakes: Atractaspididae, Elapidae, Viperidae, and Colubridae. This report describes the biological activity of a disintegrin, crotatroxin 2, isolated by a three-step chromatography procedure from the venom of the Western diamondback rattlesnake (Crotalus atrox). The intact molecular mass for crotatroxin 2 was 7.384 kDa and 71 amino acids. Crotatroxin 2 inhibited human whole blood platelet aggregation with an IC(50) of 17.5 nM, inhibited cell (66.3p) migration by 63%, and inhibited experimental lung tumor colonization in BALB/c mice at 1000 microg/kg. Our data suggest that while crotatroxin 2 inhibits platelet aggregation, cancer cell migration, and lung tumor colonization, it is done via different integrins.

ADAM15 gene structure and differential alternative exon use in human tissues

Background

ADAM15 is a metalloprotease-disintegrin implicated in ectodomain shedding and cell adhesion. Aberrant ADAM15 expression has been associated with human cancer and other disorders. We have previously shown that the alternative splicing of ADAM15 transcripts is mis-regulated in cancer cells. To gain a better understanding of ADAM15 regulation, its genomic organization and regulatory elements as well as the alternative exon use in human tissues were characterized.

Results

Human ADAM15, flanked by the FLJ32785/DCST1 and ephrin-A4 genes, spans 11.4 kb from the translation initiation codon to the polyadenylation signal, being the shortest multiple-exon ADAM gene. The gene contains 23 exons varying from 63 to 316 bp and 22 introns from 79 to 1283 bp. The gene appeared to have several transcription start sites and their location suggested the promoter location within a CpG island proximal to the translation start. Reporter expression experiments confirmed the location of functional GC-rich, TATAless and CAATless promoter, with the most critical transcription-supporting elements located -266 to -23 bp relative to the translation start. Normal human tissues showed different complex patterns of at least 13 different ADAM15 splice variants arising from the alternative use of the cytosolic-encoding exons 19, 20a/b, and 21a/b. The deduced ADAM15 protein isoforms have different combinations of cytosolic regulatory protein interaction motifs.

Conclusion

Characterization of human ADAM15 gene and identification of elements involved in the regulation of transcription and alternative splicing provide important clues for elucidation of physiological and pathological roles of ADAM15. The present results also show that the alternative exon use is a physiological post-transcriptional mechanism regulating ADAM15 expression in human tissues.

ADAM-15: a metalloprotease that mediates inflammation

Cell-cell and cell-matrix interactions are of utmost importance in the pathogenesis of inflammatory diseases. For example, cell-cell and cell-matrix interactions are crucial for leukocyte homing and recruitment to inflammatory sites. The discovery of the disintegrin and metalloprotease (ADAM) proteins, which have both adhesive and proteolytic activities, raised the question of their involvement in inflammatory processes. More interestingly, the presence of the RGD integrin-binding sequence in the disintegrin domain of ADAM-15 (MDC-15; metargidin) highlighted ADAM-15 as a protein particularly involved in cell-cell interactions. These findings therefore prompted authors to investigate the roles of ADAM-15 in inflammatory diseases. Because of the early description of ADAM-15 expression in endothelial cells, work first focused on the roles of ADAM-15 in vascular diseases, and ADAM-15 was found to be associated with atherosclerosis. Other studies also pointed at ADAM-15 as a mediator of rheumatoid arthritis and intestinal inflammation as well as inherent angiogenesis. The roles of ADAM-15 in these diseases appear to involve mechanisms as different as cell-cell interactions, cell-extracellular matrix (ECM) interactions, and shedding activity. Here we review and discuss these recent discoveries pointing to ADAM-15 as a mediator of mechanisms underlying inflammation and as a possible therapeutic target for prevention of inflammatory diseases.