Integrin-dependent Akt1 activation regulates PGC-1 expression and fatty acid oxidation

BACKGROUND

Poly-N-acetyl glucosamine nanofibers derived from a marine diatom have been used to increase cutaneous wound healing. These nanofibers exert their activity by specifically activating integrins, which makes them a useful tool for dissecting integrin-mediated pathways. We have shown that short-fiber poly-N-acetyl glucosamine nanofiber (sNAG) treatment of endothelial cells results in increased cell motility and metabolic rate in the absence of increased cell proliferation.

RESULTS

Using a Seahorse Bioanalyzer to measure oxygen consumption in real time, we show that sNAG treatment increases oxygen consumption rates, correlated with an integrin-dependent activation of Akt1. Akt1 activation leads to an increase in the expression of the transcriptional coactivator, peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α). This is not due to increased mitochondrial biogenesis, but is associated with an increase in the expression of pyruvate dehydrogenase kinase 4 (PDK4), suggesting regulation of fatty acid oxidation. Blockade of fatty acid oxidation with etomoxir, an O-carnitine palmitoyltransferase-1 inhibitor, blocks the sNAG-dependent increased oxygen consumption. (3)H-palmitate uptake experiments indicate a PDK4-dependent increase in fatty acid oxidation, which is required for nanofiber-induced cell motility.

CONCLUSIONS

Our findings imply a linear pathway whereby an integrin-dependent activation of Akt1 leads to increased PGC-1α and PDK4 expression resulting in increased energy production by fatty acid oxidation.

Poly-N-acetyl glucosamine gel matrix as a non-viral delivery vector for DNA-based vaccination

Intramuscular administration of plasmid DNA vaccines is one of the main delivery approaches that can generate antigen specific T cell responses. However, major limitations of the intramuscular delivery strategy are the low level of myocyte transfection, resulting in a minimal level of protein expression; the inability to directly target antigen presenting cells, in particular dendritic cells, which are critical for establishment of efficacious antigen-specific immune responses. Although several viral vectors have been designed to improve plasmid DNA delivery, they have limitations, including the generation of neutralizing antibodies in addition to lacking the simplicity and versatility required for universal clinical application. We have developed an inexpensive non-viral delivery vector based on the polysaccharide polymer poly-N-acetyl glucosamine with the capability to target dendritic cells. This vector is fully biocompatible, biodegradable, and nontoxic. The advantage of the application of this delivery system relative to other approaches is discussed.

The design and testing of a dual fiber textile matrix for accelerating surface hemostasis

The standard treatment for severe traumatic injury is frequently compression and application of gauze dressing to the site of hemorrhage. However, while able to rapidly absorb pools of shed blood, gauze fails to provide strong surface (topical) hemostasis. The result can be excess hemorrhage-related morbidity and mortality. We hypothesized that cost-effective materials (based on widespread availability of bulk fibers for other commercial uses) could be designed based on fundamental hemostatic principles to partially emulate the wicking properties of gauze while concurrently stimulating superior hemostasis. A panel of readily available textile fibers was screened for the ability to activate platelets and the intrinsic coagulation cascade in vitro. Type E continuous filament glass and a specialty rayon fiber were identified from the material panel as accelerators of hemostatic reactions and were custom woven to produce a dual fiber textile bandage. The glass component strongly activated platelets while the specialty rayon agglutinated red blood cells. In comparison with gauze in vitro, the dual fiber textile significantly enhanced the rate of thrombin generation, clot generation as measured by thromboelastography, adhesive protein adsorption and cellular attachment and activation. These results indicate that hemostatic textiles can be designed that mimic gauze in form but surpass gauze in ability to accelerate hemostatic reactions.

Differential effect of materials for surface hemostasis on red blood cell morphology

The design of devices for surface (topical) hemostasis has been based on maximizing activation of platelets and accelerating coagulation pathways. The studies reported herein examine another aspect of blood contact with topical hemostasis materials, i.e., surface binding of red blood cells (RBCs) and related alterations in RBC morphology. Whole blood was allowed to contact poly-N-acetyl glucosamine (pGlcNAc) containing materials: pGlcNAc nanofibers with parallel polymer alignment (beta-pGlcNAc), chitin, and chitosan. The effect on RBC morphology and function via contact with the artificial surfaces on the cell's morphology was examined with scanning and transmission electron microscopy (TEM). beta-pGlcNAc was found to densely bind RBCs and induce a stomatocytic-like morphology. Chitin and chitosan also bound RBCs, but with approximately 10-fold lower levels and with less distinct general morphologies. beta-pGlcNAc is thus unique in the nature of its interaction with RBCs. These studies indicate that the differential ability of various materials to bind and alter the morphology of RBCs at the artificial surface interface with blood is an important consideration in the design of devices for surface hemostasis.

Poly-N-acetyl glucosamine nanofibers regulate endothelial cell movement and angiogenesis: dependency on integrin activation of Ets1

Poly-N-acetyl glucosamine (pGlcNAc) nanofiber-derived materials effectively achieve hemostasis during surgical procedures. Treatment of cutaneous wounds with pGlcNAc in a diabetic mouse animal model causes marked increases in cell proliferation and angiogenesis. We sought to understand the effect of the pGlcNAc fibers on primary endothelial cells (EC) in culture and found that pGlcNAc induces EC motility. Cell motility induced by pGlcNAc fibers is blocked by antibodies directed against alphaVbeta3 and alpha5beta1 integrins, both known to play important roles in the regulation of EC motility, in vitroand in vivo. pGlcNAc treatment activates mitogen-activated protein kinase and increases Ets1, vascular endothelial growth factor (VEGF) and interleukin 1 (IL-1) expression. pGlcNAc activity is not secondary to its induction of VEGF; inhibition of the VEGF receptor does not inhibit the pGlcNAc-induced expression of Ets1 nor does pGlcNAc cause the activation of VEGF receptor. Both dominant negative and RNA interference inhibition of Ets1 blocks pGlcNAc-induced EC motility. Antibody blockade of integrin results in the inhibition of pGlcNAc-induced Ets1 expression. These findings support the hypothesis that pGlcNAc fibers induce integrin activation which results in the regulation of EC motility and thus in angiogenesis via a pathway dependent on the Ets1 transcription factor and demonstrate that Ets1 is a downstream mediator of integrin activation.

Hemostatic properties of glucosamine-based materials

Glucosamine- and N-acetyl glucosamine-containing polymers are being used in an increasing number of biomedical applications, including in products for surface (topical) hemostasis. The studies presented here investigate the relationship between the structure (conformation) and function (activation of hemostasis) of glucosamine-based materials. Several polymer systems were studied, including fibers isolated from a microalgal source containing poly-N-acetyl glucosamine polymers that are organized in a parallel, hydrogen-bonded tertiary structure and can be chemically modified to an antiparallel orientation; and gel formulation derivatives of the microalgal fibers consisting of partially deacetylated (F2 gel) and fully deacetylated (F3 gel) polymers. Comparison of the properties of the poly-N-acetyl glucosamine fiber-derived materials with chitin, chitosan, and commercial chitosan-based products are presented. Several studies were performed with the glucosamine-based materials, including (1) an analysis of the ability of materials to activate platelets and turnover of the intrinsic coagulation cascade, (2) an examination of the viscoelastic properties of mixtures of platelet-rich plasma and the glucosamine-based materials via thromboelastography, and (3) scanning electron microscopic studies to examine the morphology of the glucosamine-based materials. The results presented demonstrate that hemostatic responses to the glucosamine-based materials studied are highly dependent on their chemical nature and tertiary/quaternary structure. The unique natural microalgal fibers were found to have strongly prohemostatic activity compared to the other materials studied.

Review: novel nonviral delivery approaches for interleukin-12 protein and gene systems: curbing toxicity and enhancing adjuvant activity

It has become increasingly apparent that the ability to generate an optimal host immune response requires effective cross talk between the innate and adaptive components of the immune system. Pro-inflammatory cytokines, in particular those that can induce a danger signal, often called signal 3, are crucial in this role of initiating and augmenting the presentation of exogenous antigen to T cells by dendritic cells. Interleukin-12 (IL-12) in particular has been defined as a "signal 3" cytokine required for the antigen cross priming. Given this unique interactive function, a significant amount of work has been performed to define possible therapeutic applications for IL-12. Systemic IL-12 administration can clearly act as a potent adjuvant for postvaccination T cell responses in a variety of diseases. As an example, in the cancer setting, systemic IL-12 is capable of suppressing tumor growth, metastasis, and angiogenesis in vivo. IL-12, however, has been associated with significant dose- and schedule-dependent toxicity in early clinical trials, results that have proven to be a major obstacle to its clinical application. Recent research has focused on decreasing the toxicity of IL-12 using different delivery approaches, including virus-based and gene-modified cell-based delivery. Although effective, these approaches also have limitations, including the generation of neutralizing antibodies, in addition to lacking the simplicity and versatility required for universal clinical application. Thus, there is a significant interest in the development of alternative delivery approaches for IL-12 administration that can overcome these issues. Several nonviral delivery approaches for IL-12 protein or gene expression vectors are being defined, including alum, liposomes, and polymer-based delivery. These developing approaches have shown promising adjuvant effects with significantly lessened systemic toxicity. This article discusses the potential capabilities of these nonvirus-based IL-12 delivery systems in different disease settings, including allergy, infection, and cancer.

Synergistic platelet integrin signaling and factor XII activation in poly--acetyl glucosamine fiber-mediated hemostasis

The polymer poly-N-acetylglucosamine (pGlcNAc) containing fiber material is becoming increasingly important as a topical agent for hemostasis at wound sites. The pGlcNAc polymeric fiber provides hemostasis through redundant mechanisms that include platelet activation for fibrin network formation. The research presented here better defines the mechanism for the effect of pGlcNAc containing fibers on platelet-mediated processes. Adsorption experiments demonstrated that pGlcNAc fibers tightly bind most major plasma proteins and a specific sub-set of platelet surface proteins, including the integrin beta(3) subunit (CD61) and the von Willebrand receptor GP1b (CD42b). The result of this interaction is a platelet-dependent acceleration of fibrin gel formation. Accelerated fibrin polymerization is sensitive to factor XII inhibition by corn trypsin inhibitor and integrin inactivation with integrilin. Confocal microscopy studies show that when platelet integrins contact plasma protein-saturated pGlcNAc fibers, an increase in intracellular free calcium for platelet activation occurs to drive surface expression of phosphatidyl serine (PS). Thus, a catalytic surface for thrombin generation and accelerated fibrin clot formation results from the interaction of platelets with pGlcNAc. These findings, when considered with the observation that pGlcNAc fibers also induce red blood cell agglutination and vasoconstriction, provides an explanation for the ability of the pGlcNAc material to provide hemostasis in a wide variety of clinical applications.

Arterial embolization using poly-N-acetyl glucosamine gel in a rat kidney model

Aqueous solutions of poly-N-acetyl glucosamine (p-GlcNAc) exhibit a liquid-gel transition at physiological pH and temperature. This feature inspired the authors to conduct a study to evaluate the macro- and histological changes of rat kidneys after embolization using either p-GlcNAc gel injection into the renal artery or ligation of the renal artery. The procedures were performed in 46 rats through open abdominal surgeries. Animals were sacrificed at 3 days and at 1, 3, 5, and 8 weeks postoperatively. The results of both macro-observation and histological study showed that p-GlcNAc gels were effective in causing necrosis and subsequent fibrosis in all embolized kidneys. The data indicate that p-GlcNAc gel may have promise as an effective agent for therapeutic embolization.

Isolation, Purification, and Characterization of Poly-N-Acetyl Glucosamine Use as a Hemostatic Agent

BACKGROUND

A new polymeric material, poly-N-acetyl glucosamine (p-GlcNAc) fiber, has been identified and is effective in achieving hemostasis in surgical procedures and trauma. The p-GlcNAc material is purified from large-scale cultures of a marine microalga.

METHODS

Poly-N-acetyl glucosamine materials have been formulated as films, sponges, gels, and microspheres. The polymer's structure has been characterized by chemical composition, carbohydrate analysis, spectroscopic techniques, intrinsic viscosity, and electron microscopy.

RESULTS

Carbohydrate analyses indicate that the primary sugar present in p-GlcNAc is N-acetyl glucosamine. Elemental analyses yield percentage values for carbon, nitrogen, and hydrogen that support that the polymer is fully acetylated. Molecular weight determinations indicate that the polymer has a molecular weight of 2.0 x 10(6) Da. Fourier transform infrared, nuclear magnetic resonance, and circular dichroism spectral data have defined a unique tertiary structure. Biologic testing demonstrated that p-GlcNAc materials are fully biocompatible.

CONCLUSION

The p-GlcNAc fiber has a unique beta-tertiary structure.

Paracrine release of IL-12 stimulates IFN-gamma production and dramatically enhances the antigen-specific T cell response after vaccination with a novel peptide-based cancer vaccine

Interleukin-12 can act as a potent adjuvant for T cell vaccines, but its clinical use is limited by toxicity. Paracrine administration of IL-12 could significantly enhance the response to such vaccines without the toxicity associated with systemic administration. We have developed a novel vaccine delivery system (designated F2 gel matrix) composed of poly-N-acetyl glucosamine that has the dual properties of a sustained-release delivery system and a potent adjuvant. To test the efficacy of paracrine IL-12, we incorporated this cytokine into F2 gel matrix and monitored the response of OT-1 T cells in an adoptive transfer model. Recipient mice were vaccinated with F2 gel/SIINFEKL, F2 gel/SIINFEKL/IL-12 (paracrine IL-12), or F2 gel/SIINFEKL plus systemic IL-12 (systemic IL-12). Systemic levels of IL-12 were lower in paracrine IL-12-treated mice, suggesting that paracrine administration of IL-12 may be associated with less toxicity. However, paracrine administration of IL-12 was associated with an enhanced Ag-specific T cell proliferative and functional response. Furthermore, paracrine IL-12 promoted the generation of a stable, functional memory T cell population and was associated with protection from tumor challenge. To study the mechanisms underlying this enhanced response, wild-type and gene-deficient mice were used. The enhanced immune response was significantly reduced in IFN-gamma(-/-) and IL-12R beta 2(-/-) recipient mice suggesting that the role of IL-12 is mediated, at least in part, by host cells. Collectively, the results support the potential of F2 gel matrix as a vaccine delivery system and suggest that sustained paracrine release of IL-12 has potential clinical application.

The RDH bandage: hemostasis and survival in a lethal aortotomy hemorrhage model

BACKGROUND

The Rapid Deployment Hemostat (RDH) Bandage has been designed in collaboration with the Office of Naval Research for the treatment of bleeding because of extremity trauma. It is intended as both a battlefield and civilian severe trauma wound dressing. It consists of a specific formulation of Marine Polymer Technologies' proprietary hemostatic polymer poly-N-acetyl glucosamine, and has received FDA clearance. This study compares the hemostatic capabilities of the RDH Bandage with the standard U.S Army First Aid Field Bandage (AFAFB), utilizing a controlled lethal aortotomy model of hemorrhage.

MATERIALS AND METHODS

Aortic punch wounds 4 mm in diameter were made in the abdominal aortas of female Yorkshire White swine, and were allowed to bleed for 5 s before application of test materials. Test hemostats were applied to the wound with manual compression for 10 min. Total loss of blood was determined in each experiment. Bandages were removed at the end of 2 h, for those animals that survived, and the onset of re-bleeding was observed. Animals were monitored for an additional 30 min to assess survival following bandage removal. Hemostatic efficacy was judged by the total loss of blood, and the survival of the animals.

RESULTS

Eighty percent of the animals treated with the RDH Bandage survived the study through the entire protocol, whereas only 40% of those treated with the Army First Aid Field Bandage survived the removal of manual compression step, and none survived following the removal of bandage after the 2 h observation/monitoring period. The average blood loss for the RDH Bandage treated animals was 234 ml, and the average blood loss for the Army First Aid Field Bandage treated animals was 1071 ml, through the observation/monitoring period.

CONCLUSIONS

The RDH Bandage is significantly superior to the standard issue U.S. Army First Aid Field Bandage in the control of hemorrhage in a lethal swine abdominal aortotomy hemorrhage model, resulting in decreased blood loss and increased survival.

Mechanisms of enhanced antigen-specific T cell response following vaccination with a novel peptide-based cancer vaccine and systemic interleukin-2 (IL-2)

Systemic interleukin-2 (IL-2) therapy has been shown to enhance the clinical efficacy of peptide-based cancer vaccines. However, the mechanisms involved in this complex response remain poorly defined. IL-2 is known to be a potent T cell growth factor, but recent studies suggest that IL-2 is also involved in the regulation of T cell immune responses by increasing the susceptibility of proliferating T cells to apoptosis. Using an adoptive transfer model, we demonstrate that the administration of systemic IL-2 significantly enhances the primary and memory immune responses following peptide-based vaccination. In order to define the mechanisms of IL-2 therapy on the antigen-specific T cell response, the kinetics of T cell proliferation, apoptosis, and trafficking were explored. Systemic IL-2 therapy did not appear to alter the kinetics of T cell proliferation immediately following vaccination, but did prolong the proliferative response. Furthermore, IL-2 therapy did not significantly influence apoptosis of proliferating T cells. Such therapy did, however, potentiate L-selectin (CD62L) downregulation on activated antigen-specific T cells, and altered their trafficking confirming their potential therapeutic value. Our findings support the use of systemic IL-2 following peptide-based vaccination, and suggest that IL-2 therapy enhances the primary and memory immune responses by prolonging the proliferative response and altering the trafficking of antigen-specific T cells.

Vascular effects of poly-N-acetylglucosamine in isolated rat aortic rings

BACKGROUND

[corrected] Poly-N-acetylglucosamine (p-GlcNAc) is a secretion of marine diatoms that is known to be useful in controlling bleeding. As a component of promoting hemostasis, p-GlcNAc is thought to exert vasoconstrictor effects in arteries. The present study was undertaken to determine whether p-GlcNAc induced a significant vasoconstrictor effect and, if so, what the mechanism of this effect might be.

MATERIALS AND METHODS

We examined vascular effects of p-GlcNAc on isolated aortic rings obtained from Sprague-Dawley rats. The rings were suspended in organ baths and precontracted with U46619, a thromboxane A2 mimetic.

RESULTS

p-GlcNAc produced a concentration-dependent vasoconstriction over the range of 14 to 100 microg/ml. At a concentration of 100 microg/ml, p-GlcNAc significantly contracted aortic rings by 133 +/- 20 mg of developed force (P < 0.01). Neither a deacetylated derivative of p-GlcNAc nor a structurally related macromolecule, chitin, contracted rat aortic rings, indicating a specificity for p-GlcNAc. The vasoconstriction to p-GlcNAc was totally abolished in deendothelialized rat aortic rings, suggesting that an endothelial component is essential to the vasoconstriction. Pretreatment with the endothelin ET(A) receptor antagonist, JKC-301 (0.5 and 1 microM), significantly diminished p-GlcNAc-induced vasoconstriction by 57 to 61% (P < 0.01). However, p-GlcNAc did not significantly diminish nitric oxide release from rat aortic endothelium.

CONCLUSION

These results provide evidence that p-GlcNAc significantly contracts isolated rat aortic rings via an endothelium-dependent mechanism, partly via enhancement of endothelin-1 release from endothelial cells.

Sustained release of granulocyte-macrophage colony-stimulating factor from a modular peptide-based cancer vaccine alters vaccine microenvironment and enhances the antigen-specific T-cell response

The recent identification and molecular characterization of tumor antigens provides the opportunity to explore the rational development of peptide-based cancer vaccines. However, the response to these vaccines remains variable, and peptide-based cancer vaccines may even produce tolerance induction and enhanced tumor growth. The authors have developed a unique method for the isolation of a polysaccharide polymer of chemically pure poly- N -acetyl glucosamine (p-GlcNAc). This highly purified polysaccharide can be formulated into a stable gel matrix (designated F2 gel matrix) with unique properties of a sustained-release delivery system that has previously been shown to be an effective immune adjuvant. F2 gel matrix is capable of providing sustained release of antigenic peptide and cytokine in vitro. The purposes of this study were to characterize the ability of F2 gel matrix to provide sustained local release of cytokines in vivo and to test the hypothesis that such sustained release can enhance the microenvironment for antigen presentation, leading to a more effective antitumor response. Subcutaneous administration of F2 gel/cytokine matrix resulted in sustained release of cytokine at the vaccine site for up to 120 hours. Sustained release of granulocyte-macrophage colony-stimulating factor (GM-CSF) was associated with an increased inflammatory infiltrate at the vaccine site and enhanced dendritic cell activation. Further, accination with F2 gel/SIINFEKL/GM-CSF matrix resulted in enhanced antigen-specific immunity. Addition of GM-CSF to the F2 gel matrix resulted in an increase in the percentage of antigen-specific T cells in the draining lymph nodes, enhanced cytotoxicity, a sustained presence of antigen-specific T cells in the peripheral blood, and protection from E.G7 tumor challenge. These results support the potential of an F2 gel matrix modular vaccine delivery system that can provide sustained local release of cytokine in vivo, and confirm the powerful effects of GM-CSF as an immune adjuvant.

Sustained Release of Granulocyte-Macrophage Colony-Stimulating Factor From a Modular Peptide-Based Cancer Vaccine Alters Vaccine Microenvironment and Enhances the Antigen-Specific T-Cell Response

SUMMARY: The recent identification and molecular characterization of tumor antigens provides the opportunity to explore the rational development of peptide-based cancer vaccines. However, the response to these vaccines remains variable, and peptide-based cancer vaccines may even produce tolerance induction and enhanced tumor growth. The authors have developed a unique method for the isolation of a polysaccharide polymer of chemically pure poly- N -acetyl glucosamine (p-GlcNAc). This highly purified polysaccharide can be formulated into a stable gel matrix (designated F2 gel matrix) with unique properties of a sustained-release delivery system that has previously been shown to be an effective immune adjuvant. F2 gel matrix is capable of providing sustained release of antigenic peptide and cytokine in vitro. The purposes of this study were to characterize the ability of F2 gel matrix to provide sustained local release of cytokines in vivo and to test the hypothesis that such sustained release can enhance the microenvironment for antigen presentation, leading to a more effective antitumor response. Subcutaneous administration of F2 gel/cytokine matrix resulted in sustained release of cytokine at the vaccine site for up to 120 hours. Sustained release of granulocyte-macrophage colony-stimulating factor (GM-CSF) was associated with an increased inflammatory infiltrate at the vaccine site and enhanced dendritic cell activation. Further, accination with F2 gel/SIINFEKL/GM-CSF matrix resulted in enhanced antigen-specific immunity. Addition of GM-CSF to the F2 gel matrix resulted in an increase in the percentage of antigen-specific T cells in the draining lymph nodes, enhanced cytotoxicity, a sustained presence of antigen-specific T cells in the peripheral blood, and protection from E.G7 tumor challenge. These results support the potential of an F2 gel matrix modular vaccine delivery system that can provide sustained local release of cytokine in vivo, and confirm the powerful effects of GM-CSF as an immune adjuvant.

CaSm/gemcitabine chemo-gene therapy leads to prolonged survival in a murine model of pancreatic cancer

BACKGROUND

CaSm, the cancer-associated Sm-like oncogene, is overexpressed in greater than 80% of pancreatic tumors. We previously reported that an adenovirus expressing antisense RNA to CaSm (Ad-alpha CaSm) can decrease pancreatic tumor growth in vivo but is not curative. In the current study we investigated the mechanism of Ad-alpha CaSm's antitumor effect to rationally approach combinatorial therapy for improved efficacy.

METHODS

AsPC-1 and Panc-1 human pancreatic cancer cells were treated with Ad-alpha CaSm and examined by MTT assay for in vitro proliferation changes. Flow cytometry determined the effect of CaSm down-regulation on the cell cycle, and then cells treated with Ad-alpha CaSm in combination with cisplatin, etoposide, or gemcitabine chemotherapies were reexamined by MTT assay. SCID-Bg mice bearing subcutaneous AsPC-1 tumors were treated with Ad-alpha CaSm, gemcitabine, or the combination and monitored for tumor growth and survival.

RESULTS

Treatment with Ad-alpha CaSm reduced the proliferation of AsPC-1 and Panc-1 cells (59% and 44%, respectively; P <.05). The cell cycle revealed a cytostatic block with decreased G(1) phase and increased DNA content in treated cells. The combination of Ad-alpha CaSm with gemcitabine significantly reduced in vitro proliferation (66% vs 39% and 48% for controls), decreased in vivo AsPC-1 tumor growth by 71% (n = 10), and extended survival time from 57 to 100 days.

CONCLUSIONS

Down-regulation of CaSm reduces the growth of pancreatic cancer cells by altering the cell cycle in a cytostatic manner. The combination of Ad-alpha CaSm with gemcitabine is more effective than either agent used separately.

The cancer-associated Sm-like oncogene: a novel target for the gene therapy of pancreatic cancer

BACKGROUND

The prognosis for pancreatic cancer (PC) remains dismal, providing a clear need for the development of novel therapies. We have previously shown that the cancer-associated Sm-like (CaSm) oncogene is overexpressed in the great majority of pancreatic tumors and is required to maintain the transformed phenotype. The purpose of this study was to determine whether the application of CaSm antisense gene therapy would generate a significant antitumor effect against PC.

METHODS

An adenoviral vector (Ad-alphaCaSm) expressing a 900-base pair antisense RNA to CaSm was created. The PC cell lines AsPC-1 and Capan-1 were infected with this vector and examined for changes in in vitro proliferation by using methyl thiazol tetrazolium and soft agar assays. SCID-Bg mice bearing subcutaneous AsPC-1 tumors were treated with Ad-alphaCaSm (1 x 10(9) plaque-forming units) as a single intratumor injection with tumor growth and survival monitored.

RESULTS

AsPC-1 and Capan-1 cells showed decreased in vitro proliferation (93%, P =.0041, and 70%, P =. 0038, respectively) and anchorage independent growth (55%, P =.02, and 45%, P =.03, respectively) after treatment. Ad-alphaCaSm reduced in vivo AsPC-1 tumor growth by 40% (n = 10), extending median survival time from 35 to 60 days.

CONCLUSIONS

Ad-alphaCaSm demonstrates a significant antitumor effect against pancreatic cancer both in vitro and in vivo. These results support the role of CaSm as a significant gene involved in the neoplastic transformation of pancreatic tumors. Thus CaSm represents a novel gene target in PC and holds potential as a new treatment approach either alone or in combination with existing therapies.

Endoscopic injection of bleeding esophageal varices with a poly-N-acetyl glucosamine gel formulation in the canine portal hypertension model

BACKGROUND

It has been shown that poly-N-acetyl glucosamine produces rapid hemostasis by stimulating erythrocyte aggregation. Endoscopic injection of this substance may be effective in the treatment of bleeding varices.

METHODS

In eight heparinized dogs with a bleeding esophageal varix greater than 2 mm in diameter, 2.5% to 3.5% poly-N-acetyl glucosamine gel was injected intravariceally and paravariceally. Endoscopy, endosonography, and histopathology were performed at 1, 7, 21, and 90 days after injection.

RESULTS

In all cases, the variceal hemorrhage was stopped with three to four injections of a mean total gel volume of 1.9 mL. No recurrence of bleeding, ulceration, or stricture formation occurred. Through replacement of the gel by connective tissue, the varix was permanently obliterated in its whole course in five cases and in more than 70% of its length in three cases. No embolization and no poly-N-acetyl glucosamine antibodies were detected.

CONCLUSIONS

Endoscopic injection of bleeding esophageal varices in this animal model with the use of poly-N-acetyl glucosamine gel was an effective and safe method for stopping the hemorrhage and inducing permanent varix obliteration.

Characterization of a sustained-release delivery system for combined cytokine/peptide vaccination using a poly-N-acetyl glucosamine-based polymer matrix

Identification of tumor-associated antigens (TAAs) and their class I MHC-restricted epitopes now allows for the rational design of peptide-based cancer vaccines. A biocompatible system capable of sustained release of biologically relevant levels of cytokine and TAA peptide could provide a more effective microenvironment for antigen presentation. Our goal was to test a sustained-release cytokine/TAA peptide-based formulation using a highly purified polysaccharide [poly-N-acetyl glucosamine (p-GlcNAc)] polymer. Granulocyte-macrophage colony-stimulating factor (GM-CSF; 100 microgram) and MART-1(27-35) peptide (128 microgram in DMSO) were formulated into p-GlcNAc. Peptide release was assayed in vitro using interleukin 2 production from previously characterized MART-1(27-35)-specific Jurkat T cells (JRT22). GM-CSF release was assayed via ELISA and proliferation of M-07e (GM-CSF-dependent) cells. Local bioavailability of MART-1(27-35) peptide for uptake and presentation by antigen-presenting cells was demonstrated for up to 6 days (>0.5 microgram/ml). More than 1.0 microgram/ml GM-CSF was concomitantly released over the same period. Biocompatibility and local tissue response to p-GlcNAc releasing murine GM-CSF was determined in C57BL/6 mice via s.c. injection using murine GM-CSF (0. 2 microgram/ml) in 200 microliter of a 2.5% polymer gel. Significant lymphocytic and eosinophilic infiltration was observed 2-7 days after injection with polymer containing murine GM-CSF. The results of our studies show that this biocompatible system is capable of a sustained concomitant release of biologically active peptide and cytokine into the local microenvironment. These findings support further studies to validate a p-GlcNAc delivery system vehicle for a cytokine/TAA peptide-based cancer vaccine.

The primary structure of a fungal chitin deacetylase reveals the function for two bacterial gene products

Chitin deacetylase (EC 3.5.1.41) hydrolyzes the N-acetamido groups of N-acetyl-D-glucosamine residues in chitin. A cDNA to the Mucor rouxii mRNA encoding chitin deacetylase was isolated, characterized, and sequenced. Protein sequence comparisons revealed significant similarities of the fungal chitin deacetylase to rhizobial nodB proteins and to an uncharacterized protein encoded by a Bacillus stearothermophilus open reading frame. These data suggest the functional homology of these evolutionarily distant proteins. NodB is a chitooligosaccharide deacetylase essential for the biosynthesis of the bacterial nodulation signals, termed Nod factors. The observed similarity of chitin deacetylase to the B. stearothermophilus gene product suggests that this gene encodes a polysaccharide deacetylase.

An efficient technique for obtaining sequences flanking inserted retroviruses

Genomic mapping studies frequently employ retrovirus-mediated transfer of dominant selectable markers to specific target chromosomes. DNA probes containing sequences adjacent to inserted proviruses are valuable mapping tools in such studies. We have implemented a strategy for amplification of chromosomal sequences flanking the 5' LTR of MoMuLV-based vectors. Probes derived from these amplification products successfully differentiated murine versus human proviral localization in retrovirus-infected mouse-human chromosome 17q hybrid cells.

Optimization of the microenvironment for mammalian cell culture in flexible collagen microspheres in a fluidized-bed bioreactor

Flexible, three-dimensional, collagen Microspheres have been developed to actively promote a natural, optimal microenvironment for large-scale tissue culture of mammalian cells. The transport of nutrients into and cell products out of the Microspheres is enhanced by forced convective flow, which is the result of the tumbling of Microspheres and the dynamic properties of media flow in the fluidized-bed bioreactor. The collagen Microspheres have important characteristics of composition and morphology essential for optimal cell-matrix and cell-cell interactions. These interactions lead to high cell density and productivity through the dynamic modification of the microenvironment by cell-derived extracellular constituents. The collagen and Microsphere/fluidized-bed system provides the means to control and optimize the diffusive and contact components of the cells' microenvironment. Adaptation of cells to this microenvironment often results in dramatic increases in cell-specific productivity. Production of biotherapeutics in this process can be routinely performed in serum-free media, often leading to high productivity and product quality.

Determination of equilibrium binding affinity of distamycin and netropsin to the synthetic deoxyoligonucleotide sequence d(GGTATACC)2 by quantitative DNase I footprinting

A new method for determining the equilibrium binding constant of antitumor drugs to specific DNA sequences by quantitative DNase I footprinting is presented. The use of a short synthetic DNA oligomer to define a homogeneous population of DNA binding sites enables the calculation of the free drug concentration and the fraction of DNA sites complexed with drug in solution and is described for the first time. Since a 1:1 stoichiometry is observed for each drug-oligomer DNA complex, it becomes possible to calculate equilibrium binding constants in solution. By use of this technique, the binding affinities of the nonintercalating drugs netropsin and distamycin to the synthetic oligonucleotide d(GGTATACC)2 are determined to be Ka (25 degrees C) = 1.0 X 10(5) and 2.0 X 10(5) M-1, respectively. Quantitation of the temperature dependence associated with complex formation results in a determination of standard enthalpies of -3.75 and -8.48 kcal mol-1 for the binding of netropsin and distamycin, respectively. Calculation of other thermodynamic parameters are found to be in agreement with previous studies and indicate that the DNA binding process for these compounds is predominantly enthalpy driven. This method of quantitative DNase I footprinting is demonstrated to be a useful technique for the measurement of drug affinities to specific binding sites on DNA oligomers which are designed and synthesized expressly for this purpose. Applications of the technique to the determination of drug binding affinities at specific sites within native DNA sequences are discussed.

Properties of DNase I digestion of the deoxyoligonucleotide: 5'd(ATCGTACGAT)2(3')

Deoxyribonuclease I digestion of the deoxyoligodecamer 5'd(ATCGTACGAT)2(3') has been examined in detail to study the kinetic and structural properties of this enzyme substrate system in solution. In addition, these studies have defined, in general, those DNase I conditions to be used in future drug-DNA footprinting experiments. Special attention has been taken of those properties of DNase I that are critical for quantitation of ligand binding to small DNA fragments, and that aid in designing oligomers to be used in footprinting experiments. Enzyme activity was observed at all phosphodiester bonds in the decamer studied with varying affinity, except for the first four bonds at the 5' end of the oligomer. The DNA substrate concentration is always in excess, in order to achieve conditions of no more than one DNase I cleavage per DNA molecule. Reactions were controlled so that 65% or more of the initial amount of decamer substrate remained after DNase I digestion. It was observed that the rate of enzyme reactivity decreases with digestion time and is sensitive to the experimental conditions.

Computer assisted microdensitometric analysis of footprinting autoradiographic DATA

A system comprised of a linear scanning microdensitometer interfaced to a personal computer has been developed to facilitate analysis of ligand-DNA footprinting autoradiograms. The system, which can be used to record density and sequence information from autoradiographic films, enables the user to relate the area under an autoradiographic band to the concentration of radiolabeled molecules present in the electrophoresis gel. This report describes the computer program which performs the calculations and discusses the ability of the system to accurately determine oligonucleotide concentration, as a function of band separation, photographic response, and the computational algorithm used to calculate band areas.

RNA structure analysis using methidiumpropyl-EDTA.Fe(II): a base-pair-specific RNA structure probe

Methidiumpropyl-EDTA.Fe(II) [MPE.Fe(II)] in the presence of dithiothreitol, is shown to cleave phenylalanine-accepting tRNA (tRNAPhe) in a structure-specific fashion. Molar ratios of MPE.Fe(II) to tRNAPhe of less than 1 preferentially cleave phosphodiester bonds known to occur in double-stranded regions of the tRNAPhe molecule. Microdensitometric analysis of autoradiograms of MPE.Fe(II) cleavage products following gel electrophoresis reveals a correspondence between preferred sites of MPE.Fe(II) cleavage and sites in tRNAPhe most sensitive to cobra venom ribonuclease, a double-strand-specific endoribonuclease. Conversely, sites of cleavage by the single-strand-specific S1 nuclease correspond to those nucleotides that are least susceptible to MPE.Fe(II) hydrolysis. Sensitive helical regions in tRNAPhe include the dihydrouracil and the "T psi C" stems, which cannot be detected by cobra venom ribonuclease because of steric constraints. Phosphodiester bonds within the T psi C and dihydrouracil loop regions, which are not detected by S1 nuclease under rigorously controlled digestion conditions, are revealed by inference from their relative insensitivity to MPE.Fe(II). These results demonstrate the utility of MPE.Fe(II) as a general small molecular weight probe of RNA structure, having a greater accessibility to base-paired regions than do the more bulky enzymic probes.

RNA structure analysis using T2 ribonuclease: detection of pH and metal ion induced conformational changes in yeast tRNAPhe

We describe the use of an enzymic probe of RNA structure, T2 ribonuclease, to detect alterations of RNA conformation induced by changes in Mg2+ ion concentration and pH. T2 RNase is shown to possess single-strand specificity similar to S1 nuclease. In contrast to S1 nuclease, T2 RNase does not require divalent cations for activity. We have used this enzyme to investigate the role of Mg2+ ions in the stabilization of RNA conformation. We find that, at neutral pH, drastic reduction of the available divalent metal ions results in a decrease in the ability of T2 RNase to cleave the anticodon loop of tRNAPhe. This change accompanies an increase in the cleavage of the molecule in the T psi C and in the dihydrouracil loops. Similar treatment of Tetrahymena thermophila 5S ribosomal RNA shows that changes in magnesium ion concentration does not have a pronounced effect on the cleavage pattern produced by T2 RNase. T2 RNase activity has a broader pH range than S1 nuclease and can be used to study pH induced conformational shifts in RNA structure. We find that upon lowering the pH from 7.0 to 4.5, nucleotide D16 in the dihydrouracil loop of tRNAPhe becomes highly sensitive to T2 RNase hydrolysis. This change accompanies a decrease in the relative sensitivity of the anticodon loop to the enzyme. The role of metal ion and proton concentrations in maintenance of the functional conformation of tRNAPhe is discussed.

Quantitation of base substitutions in eukaryotic 5S rRNA: selection for the maintenance of RNA secondary structure

Eukaryotic 5S rRNA sequences from 34 diverse species were compared by the following method: (1) The sequences were aligned; (2) the positions of substitutions were located by comparison of all possible pairs of sequences; (3) the substitution sites were mapped to an assumed general base pairing model; and (4) the R-Y model of base stacking was used to study stacking pattern relationships in the structure. An analysis of the sequence and structure variability in each region of the molecule is presented. It was found that the degree of base substitution varies over a wide range, from absolute conservation to occurrence of over 90% of the possible observable substitutions. The substitutions are located primarily in stem regions of the 5S rRNA secondary structure. More than 88% of the substitutions in helical regions maintain base pairing. The disruptive substitutions are primarily located at the edges of helical regions, resulting in shortening of the helical regions and lengthening of the adjacent nonpaired regions. Base stacking patterns determined by the R-Y model are mapped onto the general secondary structure. Intrastrand and interstrand stacking could stabilize alternative coaxial structures and limit the conformational flexibility of nonpaired regions. Two short contiguous regions are 100% conserved in all species. This may reflect evolutionary constraints imposed at the DNA level by the requirement for binding of a 5S gene transcription initiation factor during gene expression.

RNase H-catalyzed site-specific deadenylylation of rabbit alpha- and beta- globin mRNAs. Secondary structure of 3'-noncoding regions

A general method is described for the removal of 3'-terminal polyadenylate tracts from eukaryotic messenger RNA to generate essentially homogeneous length products that can be 3'-end labeled and sequenced. Hybridization of specific oligodeoxyribonucleotides was used to direct ribonuclease H to the junction of the 3'-noncoding region and the polyadenylate sequence of rabbit alpha and beta globin mRNAs. Site-specific deadenylylation of both globin mRNAs is demonstrated by partial enzymatic sequence analysis following 3'-terminal labeling with 5'-pCp (where p indicates the labeled phosphate group). The secondary structure of the 3'-noncoding region is studied by enzymatic digestion with S1 nuclease and cobra venom ribonuclease. Structural features of the 3'-noncoding regions of these mRNAs are described, including the protein synthesis termination and the poly(A) addition recognition sites.

Sequence specificity of actinomycin D and Netropsin binding to pBR322 DNA analyzed by protection from DNase I

A direct approach to determining the sequence specificities of equilibrium binding drugs by using the DNase protection technique is described. The method utilizes singly end-labeled restriction fragments and partial digestion of the drug fragment complex with DNase I. Microdensitometry of autoradiograms produced after electrophoretic separation of digestion products allows determination of sequences that are affected by drug binding. The feasibility of the technique for locating small ligands bound to DNA and its eventual use as a quantitative thermodynamic approach to studying ligand binding to heterogeneous DNA as a function of sequence is illustrated by using actinomycin D and Netropsin.

Genetic manipulation of antibiotic-producing microorganisms

The application of directed selection techniques and genetic engineering methods for manipulation of antibiotic-producing microorganisms is generating a new era in industrial microbiology. Modern methods, based on advances in the knowledge of the biosynthetic pathways and regulatory mechanisms involved in the induction and repression of genes involved in antibiotic synthesis, provide a means of increasing antibiotic activity. Hence, recombinant DNA and protoplast fusion methods are used to alter the genetics of antibiotic producers in a semirandom fashion for the development of novel hybrid antibiotics. Directed mutation and selection, protoplast fusion, and both semirandom and specific recombinant DNA methods are examples of alternative procedures for manipulating the biosynthetic pathways of microorganisms for strain improvement and for new hybrid antibiotic synthesis.

Secondary structure of Bombyx mori and Dictyostelium discoideum 5S rRNA from S1 nuclease and cobra venom ribonuclease susceptibility, and computer assisted analysis

The 5S rRNAs from Bombyx mori and Dictyostelium discoideum were end-labeled with [32-P] at either the 5' or 3' end and sequenced using enzymatic digestion. The secondary structure of these molecules was studied using the single-strand specific S1 nuclease and the base-pair specific cobra venom ribonuclease. Computer analysis of these results was performed and was used to generate a consensus secondary structure for each molecule. A comparison of these results with those of other workers is presented.

Computer-aided prediction of RNA secondary structures

A brief survey of computer algorithms that have been developed to generate predictions of the secondary structures of RNA molecules is presented. Two particular methods are described in some detail. The first utilizes a thermodynamic energy minimization algorithm that takes into account the likelihood that short-range folding tends to be favored over long-range interactions. The second utilizes an interactive computer graphic modelling algorithm that enables the user to consider thermodynamic criteria as well as structural data obtained by nuclease susceptibility, chemical reactivity and phylogenetic studies. Examples of structures for prokaryotic 16S and 23S ribosomal RNAs, several eukaryotic 5S ribosomal RNAs and rabbit beta-globin messenger RNA are presented as case studies in order to describe the two techniques. Anm argument is made for integrating the two approaches presented in this paper, enabling the user to generate proposed structures using thermodynamic criteria, allowing interactive refinement of these structures through the application of experimentally derived data.

Labeling of eukaryotic messenger RNA 5' terminus with phosphorus -32: use of tobacco acid pyrophosphatase for removal of cap structures

In recent years, there has been a growing appreciation of the potential applications of 5'-32P-end-labeled mRNA, not only for screening recombinant clones and mapping gene structure, but also for revealing possible nucleotide sequence and structural signals within mRNA molecules themselves, which may be important for eukaryotic mRNA processing and turnover and for controlling differential rates of translational initiation. Three major problems, however, have retarded progress in this area, lack of methods for efficient and reproducible removal of m7G5ppp5'-cap structures, which maintain the integrity of an RNA molecule; inability to generate a sufficient amount of labeled mRNA, owing to the limited availability of most pure mRNA species; and the frequent problem of RNA degradation during in vitro end-labeling owing to RNAse contamination. The procedures presented here permit one to decap and label minute quantities of mRNA, effectively. Tobacco acid pyrophosphatase is relatively efficient in removing cap structures from even nanogram quantities of available mRNA, and enough radioactivity can be easily generated from minute amounts ofintact mRNA with very high-specific-activity [gamma-32P]ATP and the inhibition of ribonuclease contamination with diethylpyrocarbonate. These procedures can be modified and applied to almost any other type of RNA molecule as well. In Section III of this volume, we explore in detail how effectively 5'-end-labeled mRNA can be used not only for nucleotide sequence analysis, but also for mapping mRNA secondary structure.

Secondary structure of mouse and rabbit alpha- and beta-globin mRNAs: differential accessibility of alpha and beta initiator AUG codons towards nucleases

The nucleotide sequence from the 5' terminus inward of one third of mouse alpha- and beta maj-globin messenger RNAs has been established. In addition, using 5' 32P end-labeled mRNAs as substrates and S1 and T1 nucleases as probes for single-stranded regions, the secondary structures of mouse and rabbit alpha- and beta-globin mRNAs have been analyzed. Our results indicate that the AUG initiator codon in both mouse and rabbit beta-globin mRNA is quite susceptible to cleavage with S1 and T1 nucleases, suggesting that it resides in a single-stranded exposed region. In contrast, the initiator AUG in the alpha-globin mRNA of both species is inaccessible to cleavage, indicating that it is either buried by tertiary structure or is base-paired. Since the rate of initiation of protein synthesis with beta-globin mRNA in rabbit reticulocyte is 30--40% faster than for alpha-globin mRNA, these results imply a possible correlation between the differential rates of initiation with these two mRNAs and the accessibility of the respective AUG initiator codons.

Sequence and secondary structure of Drosophila melanogaster 5.8S and 2S rRNAs and of the processing site between them

Drosophila melanogaster 5.8S and 2S rRNAs were end-labeled with 32p at either the 5' or 3' end and were sequenced. 5.8S rRNA is 123 nucleotides long and homologous to the 5' part of sequenced 5.8S molecules from other species. 2S rRNA is 30 nucleotides long and homologous to the 3' part of other 5.8S molecules. The 3' end of the 5.8S molecule is able to base-pair with the 5' end of the 2S rRNA to generate a helical region equivalent in position to the "GC-rich hairpin" found in all previously sequenced 5.8S molecules. Probing the structure of the labeled Drosophila 5.8S molecule with S1 nuclease in solution verifies its similarity to other 5.8S rRNAs. The 2S rRNA is shown to form a stable complex with both 5.8S and 26S rRNAs separately and together. 5.8S rRNA can also form either binary or ternary complexes with 2S and 26S rRNA. It is concluded that the 5.8S rRNA in Drosophila melanogaster is very similar both in sequence and structure to other 5.8 rRNAs but is split into two pieces, the 2S rRNA being the 3' part. 2S anchors the 5.8S and 26S rRNA. The order of the rRNA coding regions in the ribosomal DNA repeating unit is shown to be 18S - 5.8S - 2S - 26S. Direct sequencing of ribosomal DNA shows that the 5.8S and 2S regions are separated by a 28 nucleotide spacer which is A-T rich and is presumably removed by a specific processing event. A secondary structure model is proposed for the 26S-5.8S ternary complex and for the presumptive precursor molecule.

End labeling of enzymatically decapped mRNA

A method is presented for rapid and efficient 5' end labeling with 32P of capped mRNAs, by a series of three enzymatic reactions: the blocking nucleotide of the cap structure is removed by tobacco acid pyrophosphatase, and after dephosphorylation with alkaline phosphatase the 5' end is labeled with gamma-32-P-ATP and T4 polynucleotide kinase.

The effect of magnesium and manganese ions on the structure and template activity for reverse transcriptase of polyribocytidylate and its 2'-0-methyl derivative

The secondary structure of the hydrogen bonded hybrids polycytidylate-oligodeoxguanylate (poly(rC)-(dG)12-18 and poly (2'-oMe) cytidylate-oligodeoxyguanylate (poly (rCm)-(dG)12-18 was studied at several magnesium and manganese ion concentrations. These hybrids are effective template-primer complexes for the synthesis of poly(dG) by avian myeloblastosis virus (AMV) DNA polymerase under disparate ionic conditions. Circular dichroism spectra and thermal melting data were obtained as a function of ion concentration, including conditions that allow optimum rates of poly (dG) synthesis by each complex. These studies demonstrate that both hybrids can change conformation and stability depending on their ionic environment. Comparison of enzyme activity and physical data suggest that the polymerase recognizes particular secondary structure features. Changes in the activity of the AMV polymerase can be induced by varying the Mg++ and Mn++ concentrations alone and in combination. These variations in enzyme activity are correlated with observed changes in the base-stacking alignment of the synthetic template primers. The ions, therefore, seem to affect enzyme activity by altering the conformation of the polnucleotide complexes.

Specific hydrolysis of rabbit globin messenger RNA by S1 nuclease

S1 nuclease isolated from Aspergillus oryzae has been used to investigate the secondary structure of rabbit globin messenger RNA (mRNA). The enzyme, which is specific for single stranded nucleotides, digests globin mRNA to a limited extent, with 65-75% of the mRNA nucleotides resistant to digestion under mild conditions. This limited digestion is not due to enzyme inactivation, but rather to the normal activity of the single-strand nuclease. The reaction was studied as a function of temperature, salt and enzyme concentration. Analysis of the products of digestion on 20% acrylamide- 7M urea slab gels reveals a stable pattern of unique fragments ranging in size from 9 to 71 nucleotides. Separated alpha and beta globin mRNAs show similar, but not identical gel patterns, indicating strong structural similarities between the two species. The high degree of nuclease resistance, along with the fragment patterns seen on polyacrylamide gels, gives evidence to support a model of rabbit globin mRNA which contain specific, rather than random, helical structure.