AAV-mediated gene transfer of tissue inhibitor of metalloproteinases-1 inhibits vascular tumor growth and angiogenesis in vivo

Microvascular Experimentation in the Chick Chorioallantoic Membrane as a Model for Screening Angiogenic Agents including from Gene-Modified Cells

The chick chorioallantoic membrane (CAM) assay model of angiogenesis has been highlighted as a relatively quick, low cost and effective model for the study of pro-angiogenic and anti-angiogenic factors. The chick CAM is a highly vascularised extraembryonic membrane which functions for gas exchange, nutrient exchange and waste removal for the growing chick embryo. It is beneficial as it can function as a treatment screening tool, which bridges the gap between cell based in vitro studies and in vivo animal experimentation. In this review, we explore the benefits and drawbacks of the CAM assay to study microcirculation, by the investigation of each distinct stage of the CAM assay procedure, including cultivation techniques, treatment applications and methods of determining an angiogenic response using this assay. We detail the angiogenic effect of treatments, including drugs, metabolites, genes and cells used in conjunction with the CAM assay, while also highlighting the testing of genetically modified cells. We also present a detailed exploration of the advantages and limitations of different CAM analysis techniques, including visual assessment, histological and molecular analysis along with vascular casting methods and live blood flow observations.

TARBP2 promotes tumor angiogenesis and metastasis by destabilizing antiangiogenic factor mRNAs

Tumor angiogenesis is a crucial step in the further growth and metastasis of solid tumors. However, its regulatory mechanism remains unclear. Here, we showed that TARBP2, an RNA‐binding protein, played a role in promoting tumor‐induced angiogenesis both in vitro and in vivo through degrading the mRNAs of antiangiogenic factors, including thrombospondin1/2 (THBS1/2), tissue inhibitor of metalloproteinases 1 (TIMP1), and serpin family F member 1 (SERPINF1), by targeting their 3′untranslated regions (3′UTRs). Overexpression of TARBP2 promotes tumor cell–induced angiogenesis, while its knockdown inhibits tumor angiogenesis. Clinical cohort analysis revealed that high expression level of TARBP2 was associated with poor survival of lung cancer and breast cancer patients. Mechanistically, TARBP2 physically interacts with the stem‐loop structure located in the 3′UTR of antiangiogenic transcripts, leading to mRNA destabilization by the dsRNA‐binding domains 1/2 (dsRBDs1/2). Notably, the expression level of TARBP2 in human tumor tissue is negatively correlated with the expression of antiangiogenic factors, including THBS1/2, and brain‐specific angiogenesis inhibitor 1 (BAI1). Moreover, TARBP2 expression is strongly associated with tumor angiogenesis in a group of human lung cancer samples. Collectively, our results highlight that TARBP2 is a novel tumor angiogenesis regulator that could promote tumor angiogenesis by selectively downregulating antiangiogenic gene expression.

Melatonin Enhances the Usefulness of Ionizing Radiation: Involving the Regulation of Different Steps of the Angiogenic Process

Radiotherapy is a part of cancer treatment. To improve its efficacy has been combined with radiosensitizers such as antiangiogenic agents. Among the mechanisms of the antitumor action of melatonin are antiangiogenic effects. Our goal was to investigate whether melatonin may modulate the sensitivity of endothelial cells (HUVECs) to ionizing radiation. Melatonin (1 mM) enhanced the inhibition induced by radiation on different steps of the angiogenic process, cell proliferation, migration, and tubular network formation. In relation with the activity and expression of enzymes implicated in estrogen synthesis, in co-cultures HUVECs/MCF-7, radiation down-regulated aromatase mRNA expression, aromatase endothelial-specific promoter I.7, sulfatase activity and expression and 17β-HSD1 activity and expression and melatonin enhanced these effects. Radiation and melatonin induced a significant decrease in VEGF, ANG-1, and ANG-2 mRNA expression. In ANG-2 and VEGF mRNA expression melatonin potentiated the inhibitory effect induced by radiation. In addition, melatonin counteracted the stimulatory effect of radiation on FGFR3, TGFα, JAG1, IGF-1, and KDR mRNA expression and reduced ANPEP expression. In relation with extracellular matrix molecules, radiation increased MMP14 mRNA expression and melatonin counteracted the stimulatory effect of radiation on MMP14 mRNA expression and increased TIMP1 expression, an angiogenesis inhibitor. Melatonin also counteracted the stimulatory effect of radiation on CXCL6, CCL2, ERK1, ERK2, and AKT1 mRNA expression and increased the inhibitory effect of radiation on NOS3 expression. In CAM assay, melatonin enhanced the reduction of the vascular area induced by radiation. Melatonin potentiated the inhibitory effect on the activation of p-AKT and p-ERK exerted by radiation. Antiangiogenic effect of melatonin could be mediated through AKT and ERK pathways, proteins involved in vascular endothelial (VE) cell growth, cell proliferation, survival, migration, and angiogenesis. In addition, radiation increased endothelial cell permeability and melatonin counteracted it by regulating the internalization of VE-cadherin. Radiation has some side effects on angiogenesis that may reduce its effectiveness against tumor growth and melatonin is able to neutralize these negative actions of radiation. Additionally, melatonin potentiated radiation-induced antiangiogenic actions on several steps of the angiogenic process and enhanced its antitumor action. Our findings point to melatonin as a useful molecule as adjuvant to radiotherapy in cancer treatment.

Antitumorigenic targets of cannabinoids - current status and implications

INTRODUCTION

Molecular structures of the endocannabinoid system have gained interest as potential pharmacotherapeutical targets for systemic cancer treatment.

AREAS COVERED

The present review covers the contribution of the endocannabinoid system to cancer progression. Particular focus will be set on the accumulating preclinical data concerning antimetastatic, anti-invasive and anti-angiogenic mechanisms induced by cannabinoids.

EXPERT OPINION

The main goal of targeting endocannabinoid structures for systemic anticancer treatment is the comparatively good safety profile of cannabinoid compounds. In addition, antitumorigenic mechanisms of cannabinoids are not restricted to a single molecular cascade but involve multiple effects on various levels of cancer progression such as angiogenesis and metastasis. Particularly the latter effect has gained interest for pharmacological interventions. Thus, drugs aiming at the endocannabinoid system may represent potential 'antimetastatics' for an upgrade of a future armamentarium against cancer diseases.

Expanding the Activity of Tissue Inhibitors of Metalloproteinase (TIMP)-1 against Surface-Anchored Metalloproteinases by the Replacement of Its C-Terminal Domain: Implications for Anti-Cancer Effects

Tissue inhibitors of metalloproteinases (TIMPs) are the endogenous inhibitors of the matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinases (ADAMs). TIMP molecules are made up of two domains: an N-terminal domain that associates with the catalytic cleft of the metalloproteinases (MP) and a smaller C-terminal domain whose role in MP association is still poorly understood. This work is aimed at investigating the role of the C-terminal domain in MP selectivity. In this study, we replaced the C-terminal domain of TIMP-1 with those of TIMP-2, -3 and -4 to create a series of "T1:TX" chimeras. The affinity of the chimeras against ADAM10, ADAM17, MMP14 and MMP19 was investigated. We can show that replacement of the C-terminal domain by those of other TIMPs dramatically increased the affinity of TIMP-1 for some MPs. Furthermore, the chimeras were able to suppress TNF-α and HB-EGF shedding in cell-based setting. Unlike TIMP-1, T1:TX chimeras had no growth-promoting activity. Instead, the chimeras were able to inhibit cell migration and development in several cancer cell lines. Our findings have broadened the prospect of TIMPs as cancer therapeutics. The approach could form the basis of a new strategy for future TIMP engineering.

Effects of the use of assisted reproduction and high-caloric diet consumption on body weight and cardiovascular health of juvenile mouse offspring

Maternal obesity and the use of assisted reproductive technologies (ART) are two suboptimal developmental environments that can lead to offspring obesity and cardiovascular disease. We hypothesized that these environments independently and synergistically adversely affect the offspring's weight and cardiovascular performance at ~7 weeks of age. Mice were fed either 24% fat and 17.5% high-fructose (HF) corn syrup or maintenance chow (5% fat; low-fat, no-fructose (LF)). Dams were subdivided into no ART and ART groups. ART embryos were cultured in Whitten's medium and transferred into pseudopregnant recipients consuming the same diet as the donor. Offspring were fed the same diet as the mother. Body weights (BW) were measured weekly and mean arterial pressure (MAP) was collected through carotid artery catheterization at killing (55±0.5 days old). Expression of genes involved in cardiovascular remodeling was measured in thoracic aorta using qRT-PCR, and levels of reactive oxygen species (ROS) were measured intracellularly and extracellularly in mesenteric resistance arteries. ART resulted in increased BW at weaning. This effect decreased over time and diet was the predominant determinant of BW by killing. Males had greater MAP than females (P=0.002) and HF consumption was associated with greater MAP regardless of sex (P<0.05). Gene expression was affected by sex (P<0.05) and diet (P<0.1). Lastly, the use of ART resulted in offspring with increased intracellular ROS (P=0.05). In summary, exposure to an obesogenic diet pre- and/or post-natally affects weight, MAP, and gene expression while ART increases oxidative stress in mesenteric resistance arteries of juvenile offspring, no synergistic effects were observed.

Critical appraisal of the potential use of cannabinoids in cancer management

Cannabinoids have been attracting a great deal of interest as potential anticancer agents. Originally derived from the plant Cannabis sativa, there are now a number of endo-, phyto- and synthetic cannabinoids available. This review summarizes the key literature to date around the actions, antitumor activity, and mechanisms of action for this broad range of compounds. Cannabinoids are largely defined by an ability to activate the cannabinoid receptors – CB₁ or CB₂. The action of the cannabinoids is very dependent on the exact ligand tested, the dose, and the duration of exposure. Some cannabinoids, synthetic or plant-derived, show potential as therapeutic agents, and evidence across a range of cancers and evidence in vitro and in vivo is starting to be accumulated. Studies have now been conducted in a wide range of cell lines, including glioma, breast, prostate, endothelial, liver, and lung. This work is complemented by an increasing body of evidence from in vivo models. However, many of these results remain contradictory, an issue that is not currently able to be resolved through current knowledge of mechanisms of action. While there is a developing understanding of potential mechanisms of action, with the extracellular signal-regulated kinase pathway emerging as a critical signaling juncture in combination with an important role for ceramide and lipid signaling, the relative importance of each pathway is yet to be determined. The interplay between the intracellular pathways of autophagy versus apoptosis is a recent development that is discussed. Overall, there is still a great deal of conflicting evidence around the future utility of the cannabinoids, natural or synthetic, as therapeutic agents.

Reconstructed adeno-associated virus with the extracellular domain of murine PD-1 induces antitumor immunity

BACKGROUND

The negative signaling provided by interactions of the co-inhibitory molecule, programmed death-1 (PD-1), and its ligands, B7-H1 (PD-L1) and B7-DC (PD-L2), is a critical mechanism contributing to tumor evasion; blockade of this pathway has been proven to enhance cytotoxic activity and mediate antitumor therapy. Here we evaluated the anti-tumor efficacy of AAV-mediated delivery of the extracellular domain of murine PD-1 (sPD-1) to a tumor site.

MATERIAL AND METHODS

An rAAV vector was constructed in which the expression of sPD-1, a known negative regulator of TCR signals, is driven by human cytomegalovirus immediate early promoter (CMV-P), using a triple plasmid transfection system. Tumor-bearing mice were then treated with the AAV/sPD1 construct and expression of sPD-1 in tumor tissues was determined by semi quantitative RT-PCR, and tumor weights and cytotoxic activity of splenocytes were measured.

RESULTS

Analysis of tumor homogenates revealed sPD-1 mRNA to be significantly overexpressed in rAAV/sPD-1 treated mice as compared with control levels. Its use for local gene therapy at the inoculation site of H22 hepatoma cells could inhibit tumor growth, also enhancing lysis of tumor cells by lymphocytes stimulated specifically with an antigen. In addition, PD-1 was also found expressed on the surfaces of activated CD8+ T cells.

CONCLUSION

This study confirmed that expression of the soluble extracellular domain of PD-1 molecule could reduce tumor microenvironment inhibitory effects on T cells and enhance cytotoxicity. This suggests that it might be a potential target for development of therapies to augment T-cell responses in patients with malignancies.

Strain variation in response to lung ischemia: role of MMP-12

Background

Systemic neovascularization of the lung during chronic ischemia has been observed in all mammals studied. However, the proteins that orchestrate the complex interaction of new vessel growth and tunneling through lung tissue matrix have not been described. Although previous work has demonstrated the CXC chemokines are essential growth factors in the process of angiogenesis in mice and rats, key matrix proteins have not been identified.

Methods

Since the degradation of chemokines has been shown to be dependent on metalloproteinases (MMP), we first surveyed gene expression patterns (real time RT-PCR) of several lung matrix proteins in DBA/J (D2) mice and C57Bl/6 (B6) mice, strains known to have divergent parenchymal responses in other lung disease models. We studied changes in the time course of MMP-12 activity in D2 and B6 mice. Functional angiogenesis was determined 14 days after the onset of complete left lung ischemia induced by left pulmonary artery ligation (LPAL), using fluorescent microspheres.

Results

Our results confirmed higher levels of MMP-12 gene expression in D2 mice relative to B6, which corresponded to a phenotype of minimal systemic angiogenesis in D2 mice and more robust angiogenesis in B6 mice (p < 0.01). MMP-12 activity decreased over the course of 14 days in B6 mice whereas it increased in D2 mice (p < 0.05). MMP-12 was associated largely with cells expressing the macrophage marker F4/80. Genetic deficiency of MMP-12 resulted in significantly enhanced neovascularization (p < 0.01 from B6).

Conclusion

Taken together, our results suggest macrophage-derived MMP-12 contributes to angiostasis in the ischemic lung.

Update on the endocannabinoid system as an anticancer target

INTRODUCTION

Recent studies have shown that the endocannabinoid system (ECS) could offer an attractive antitumor target. Numerous findings suggest the involvement of this system (constituted mainly by cannabinoid receptors, endogenous compounds and the enzymes for their synthesis and degradation) in cancer cell growth in vitro and in vivo.

AREAS COVERED

This review covers literature from the past decade which highlights the potential of targeting the ECS for cancer treatment. In particular, the levels of endocannabinoids and the expression of their receptors in several types of cancer are discussed, along with the signaling pathways involved in the endocannabinoid antitumor effects. Furthermore, the beneficial and adverse effects of old and novel compounds in clinical use are discussed.

EXPERT OPINION

One direction that should be pursued in antitumor therapy is to select compounds with reduced psychoactivity. This is known to be connected to the CB1 receptor; thus, targeting the CB2 receptor is a popular objective. CB1 receptors could be maintained as a target to design new compounds, and mixed CB1-CB2 ligands could be effective if they are able to not cross the BBB. Furthermore, targeting the ECS with agents that activate cannabinoid receptors or inhibitors of endogenous degrading systems such as fatty acid amide hydrolase inhibitors may have relevant therapeutic impact on tumor growth. Additional studies into the downstream consequences of endocannabinoid treatment are required and may illuminate other potential therapeutic targets.

Systemic delivery of TNF-related apoptosis-inducing ligand (TRAIL) elevates levels of tissue inhibitor of metalloproteinase-1 (TIMP-1) and prevents type 1 diabetes in nonobese diabetic mice

Recent studies have demonstrated that TNF-related apoptosis-inducing ligand (TRAIL) is a modulator of the immune response. The relation between TRAIL and type 1 diabetes (T1D) as an autoimmune inflammatory disease in vivo is relatively unknown. To explore the potential role of TRAIL in the development of T1D, we examined its in vivo effects in nonobese diabetic (NOD) mice. NOD mice at 7 wk of age were iv injected with an adenovirus carrying either human TRAIL (Ad.hTRAIL) or β-galactosidase genes. Blood glucose was monitored weekly, and the expression of hTRAIL was evaluated in plasma and liver of mice. To investigate whether hTRAIL elicits its effect through the induction of tissue inhibitor of metalloproteinase-1 (TIMP-1), we examined the concentration of plasma TIMP-1 by ELISA and the inhibition of matrix metalloproteinase (MMP) by gelatin zymography. Here, we show that Ad.hTRAIL-transduced mice had significantly reduced blood glucose levels and markedly increased production of TIMP-1 compared with control β-galactosidase animals. Pancreatic tissue isolated from Ad.hTRAIL-treated NOD mice showed reduced MMP activities associated with significantly improved insulitis. In addition, TIMP-1 in vitro suppressed cytokine-induced apoptosis in insulin-producing INS-1 cells. These results indicate that T1D can be prevented by TRAIL overexpression through enhancement of TIMP-1 function. Elevated TIMP-1 production inhibits the activity of MMPs, which may contribute to suppress the transmigration of diabetogenic T cells into the pancreatic islets and protects pancreatic β-cells from cytokine-induced apoptosis. Therefore, TRAIL and TIMP-1 induction may be potential targets to prevent development of T1D.

Cyclooxygenase-2 and tissue inhibitor of matrix metalloproteinases-1 confer the antimigratory effect of cannabinoids on human trabecular meshwork cells

Cannabinoids have received considerable attention as potential antiglaucomatous drugs. Recently, prostaglandins (PG) have been suggested to contribute to this effect. Within the factors conferring the development of glaucoma, depletion of the aqueous humor outflow-regulating trabecular meshwork (TM) cells elicited by migration from the outflow system is considered to play a pivotal role. This study therefore investigates the impact of two cannabinoids, Delta(9)-tetrahydrocannabinol (THC) and R(+)-methanandamide (MA), on the migration of human TM cells and the involvement of the PG-synthesizing enzyme cyclooxygenase-2 (COX-2) and one of its potential downstream targets, the tissue inhibitor of matrix metalloproteinases-1 (TIMP-1), to this response. Using Boyden chamber assays cannabinoids were shown to elicit an antimigratory effect that was reversed by antagonists for CB(1) as well as CB(2) receptors and accompanied by upregulation of COX-2 and TIMP-1 expression and PGE(2) synthesis. Knockdown of cannabinoid-induced COX-2 or TIMP-1 expression by siRNA or inhibition of COX-2 activity by NS-398 led to a significant suppression of this antimigratory action. Migration was also diminished by the major COX-2 product PGE(2) and by recombinant TIMP-1. Experiments using selective E prostanoid (EP) receptor agonists and antagonists revealed that decreased migration by PGE(2), THC and MA was mediated via EP(2) and EP(4) receptors. Finally, the cannabinoid-mediated increases of TIMP-1 levels were abolished by NS-398, and PGE(2) was shown to elicit a concentration-dependent increase of TIMP-1. Collectively, this data demonstrate a COX-2-dependent upregulation of TIMP-1 conferring the antimigratory action of cannabinoids. A decreased migration reducing TM cell loss in glaucoma might be involved in the antiglaucomatous action of cannabinoids.

The Chick Embryo Chorioallantoic Membrane as an In Vivo Assay to Study Antiangiogenesis

Antiangiogenesis, e.g., inhibition of blood vessel growth, is being investigated as a way to prevent the growth of tumors and other angiogenesis-dependent diseases. Pharmacological inhibition interferes with the angiogenic cascade or the immature neovasculature with synthetic or semi-synthetic substances, endogenous inhibitors or biological antagonists.The chick embryo chorioallantoic membrane (CAM) is an extraembryonic membrane, which serves as a gas exchange surface and its function is supported by a dense capillary network. Because its extensive vascularization and easy accessibility, CAM has been used to study morphofunctional aspects of the angiogenesis process in vivo and to study the efficacy and mechanism of action of pro- and anti-angiogenic molecules. The fields of application of CAM in the study of antiangiogenesis, including our personal experience, are illustrated in this review article.

Extracellular matrix molecules: potential targets in pharmacotherapy

The extracellular matrix (ECM) consists of numerous macromolecules classified traditionally into collagens, elastin, and microfibrillar proteins, proteoglycans including hyaluronan, and noncollagenous glycoproteins. In addition to being necessary structural components, ECM molecules exhibit important functional roles in the control of key cellular events such as adhesion, migration, proliferation, differentiation, and survival. Any structural inherited or acquired defect and/or metabolic disturbance in the ECM may cause cellular and tissue alterations that can lead to the development or progression of disease. Consequently, ECM molecules are important targets for pharmacotherapy. Specific agents that prevent the excess accumulation of ECM molecules in the vascular system, liver, kidney, skin, and lung; alternatively, agents that inhibit the degradation of the ECM in degenerative diseases such as osteoarthritis would be clinically beneficial. Unfortunately, until recently, the ECM in drug discovery has been largely ignored. However, several of today's drugs that act on various primary targets affect the ECM as a byproduct of the drugs' actions, and this activity may in part be beneficial to the drugs' disease-modifying properties. In the future, agents and compounds targeting directly the ECM will significantly advance the treatment of various human diseases, even those for which efficient therapies are not yet available.

Antitumorigenic effects of cannabinoids beyond apoptosis

According to the World Health Organization, the cases of death caused by cancer will have been doubled until the year 2030. By 2010, cancer is expected to be the number one cause of death. Therefore, it is necessary to explore novel approaches for the treatment of cancer. Over past years, the antitumorigenic effects of cannabinoids have emerged as an exciting field in cancer research. Apart from their proapoptotic and antiproliferative action, recent research has shown that cannabinoids may likewise affect tumor cell angiogenesis, migration, invasion, adhesion, and metastasization. This review will summarize the data concerning the influence of cannabinoids on these locomotive processes beyond modulation of cancer cell apoptosis and proliferation. The findings discussed here provide a new perspective on the antitumorigenic potential of cannabinoids.

Role of matrix metalloproteinases in the inflammatory process of respiratory diseases

Matrix metalloproteinases (MMPs) are a group of proteases known to regulate the turnover of extracellular matrix and thus are suggested to be important in the process of several diseases associated with tissue remodeling. Furthermore, the concept that modulation of airway remodeling including excessive proteolysis damage of the tissue, may be of interest as a basis for future treatment. Degradation of extracellular matrix is currently associated with structural and recruited cell activation and release of inflammatory mediators and MMPs. Indeed, a marked increase in their expression is observed associated with a variety of inflammatory diseases, including respiratory pathologies. In these conditions, we have to consider MMPs as therapeutic targets which can be inhibited by non-selective and/or selective inhibitors as anti-inflammatory compounds. The present review aims to discuss the potential interest of the inhibition of MMP in inflammatory diseases with a focus on respiratory diseases.

Transcriptional targeting of tumor endothelial cells for gene therapy

It is well known that angiogenesis plays a critical role in the pathobiology of tumors. Recent clinical trials have shown that inhibition of angiogenesis can be an effective therapeutic strategy for patients with cancer. However, one of the outstanding issues in anti-angiogenic treatment for cancer is the development of toxicities related to off-target effects of drugs. Transcriptional targeting of tumor endothelial cells involves the use of specific promoters for selective expression of therapeutic genes in the endothelial cells lining the blood vessels of tumors. Recently, several genes that are expressed specifically in tumor-associated endothelial cells have been identified and characterized. These discoveries have enhanced the prospectus of transcriptionally targeting tumor endothelial cells for cancer gene therapy. In this manuscript, we review the promoters, vectors, and therapeutic genes that have been used for transcriptional targeting of tumor endothelial cells, and discuss the prospects of such approaches for cancer gene therapy.

Changes in the endocannabinoid system may give insight into new and effective treatments for cancer

The endocannabinoid system comprises specific cannabinoid receptors such as Cb1 and Cb2, the endogenous ligands (anandamide and 2-arachidonyl glycerol among others) and the proteins responsible for their synthesis and degradation. This system has become the focus of research in recent years because of its potential therapeutic value several disease states. The following review describes our current knowledge of the changes that occur in the endocannabinoid system during carcinogenesis and then focuses on the effects of anandamide on various aspects of the carcinogenic process such as growth, migration, and angiogenesis in tumors from various origins.

Biology and potential clinical implications of tissue inhibitor of metalloproteinases-1 in colorectal cancer treatment

Colorectal cancer (CRC) is the second leading cause of cancer-related death in the industrialized world. About half of "curatively" resected patients develop recurrent disease within the next 3-5 years despite the lack of clinical, histological and biochemical evidence of remaining overt disease after resection of the primary tumour. Availability of validated biological markers for early detection, selection for adjuvant therapy, prediction of treatment efficacy and monitoring of treatment efficacy would most probably increase survival. Tissue inhibitor of metalloproteinases-1 (TIMP-1) may be such a marker. TIMP-1 inhibits the proteolytic activity of metalloproteinases, which are centrally involved in tumour invasion and metastases. However, in clinical investigations high tumour tissue or plasma levels of TIMP-1 have shown a strong and independent association with a shorter survival time in CRC patients, suggesting that TIMP-1 could have a tumour-promoting function. Furthermore, measurement of plasma TIMP-1 has been shown to be useful for disease detection, with a high sensitivity and high specificity for early-stage colon cancer. This review describes some basic information on the current knowledge of the biology of TIMP-1 as well as the potential use of TIMP-1 as a biological marker in the management of CRC patients.

Inhibition of cancer cell invasion by cannabinoids via increased expression of tissue inhibitor of matrix metalloproteinases-1

BACKGROUND

Cannabinoids, in addition to having palliative benefits in cancer therapy, have been associated with anticarcinogenic effects. Although the antiproliferative activities of cannabinoids have been intensively investigated, little is known about their effects on tumor invasion.

METHODS

Matrigel-coated and uncoated Boyden chambers were used to quantify invasiveness and migration, respectively, of human cervical cancer (HeLa) cells that had been treated with cannabinoids (the stable anandamide analog R(+)-methanandamide [MA] and the phytocannabinoid delta9-tetrahydrocannabinol [THC]) in the presence or absence of antagonists of the CB1 or CB2 cannabinoid receptors or of transient receptor potential vanilloid 1 (TRPV1) or inhibitors of p38 or p42/44 mitogen-activated protein kinase (MAPK) pathways. Reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblotting were used to assess the influence of cannabinoids on the expression of matrix metalloproteinases (MMPs) and endogenous tissue inhibitors of MMPs (TIMPs). The role of TIMP-1 in the anti-invasive action of cannabinoids was analyzed by transfecting HeLa, human cervical carcinoma (C33A), or human lung carcinoma cells (A549) cells with siRNA targeting TIMP-1. All statistical tests were two-sided.

RESULTS

Without modifying migration, MA and THC caused a time- and concentration-dependent suppression of HeLa cell invasion through Matrigel that was accompanied by increased expression of TIMP-1. At the lowest concentrations tested, MA (0.1 microM) and THC (0.01 microM) led to a decrease in invasion (normalized to that observed with vehicle-treated cells) of 61.5% (95% CI = 38.7% to 84.3%, P < .001) and 68.1% (95% CI = 31.5% to 104.8%, P = .0039), respectively. The stimulation of TIMP-1 expression and suppression of cell invasion were reversed by pretreatment of cells with antagonists to CB1 or CB2 receptors, with inhibitors of MAPKs, or, in the case of MA, with an antagonist to TRPV1. Knockdown of cannabinoid-induced TIMP-1 expression by siRNA led to a reversal of the cannabinoid-elicited decrease in tumor cell invasiveness in HeLa, A549, and C33A cells.

CONCLUSION

Increased expression of TIMP-1 mediates an anti-invasive effect of cannabinoids. Cannabinoids may therefore offer a therapeutic option in the treatment of highly invasive cancers.

Adeno-associated virus-mediated antiangiogenic gene therapy with thrombospondin-1 type 1 repeats and endostatin

PURPOSE

Recombinant adeno-associated virus (rAAV)-mediated antiangiogenic gene therapy offers a powerful strategy for cancer treatment, maintaining sustained levels of antiangiogenic factors with coincident enhanced therapeutic efficacy. We aimed to develop rAAV-mediated antiangiogenic gene therapy delivering endostatin and 3TSR, the antiangiogenic domain of thrombospondin-1.

EXPERIMENTAL DESIGN

rAAV vectors were constructed to express endostatin (rAAV-endostatin) or 3TSR (rAAV-3TSR). The antiangiogenic efficacy of the vectors was characterized using a vascular endothelial growth factor (VEGF)-induced mouse ear angiogenesis model. To evaluate the antitumor effects of the vectors, immunodeficient mice were pretreated with rAAV-3TSR or rAAV-endostatin and received orthotopic implantation of cancer cells into the pancreas. To mimic clinical situations, mice bearing pancreatic tumors were treated with intratumoral injection of rAAV-3TSR or rAAV-endostatin.

RESULTS

rAAV-mediated i.m. gene delivery resulted in expression of the transgene in skeletal muscle with inhibition of VEGF-induced angiogenesis at a distant site (the ear). Local delivery of the vectors into the mouse ear also inhibited VEGF-induced ear angiogenesis. Pretreatment of mice with i.m. or intrasplenic injection of rAAV-endostatin or rAAV-3TSR significantly inhibited tumor growth. A single intratumoral injection of each vector also significantly decreased the volume of large established pancreatic tumors. Tumor microvessel density was significantly decreased in each treatment group and was well correlated with tumor volume reduction. Greater antiangiogenic and antitumor effects were achieved when rAAV-3TSR and rAAV-endostatin were combined.

CONCLUSIONS

rAAV-mediated 3TSR and endostatin gene therapy showed both localized and systemic therapeutic effects against angiogenesis and tumor growth and may provide promise for patients with pancreatic cancer.

Matrix metalloproteinases and their inhibitors in vascular remodeling and vascular disease

Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that degrade various components of the extracellular matrix (ECM). Members of the MMP family include collagenases, gelatinases, stromelysins, matrilysins and membrane-type MMPs. ProMMPs are cleaved into active forms that promote degradation of ECM proteins. Also, recent evidence suggests direct or indirect effects of MMPs on ion channels in the endothelium and vascular smooth muscle, and on other mechanisms of vascular relaxation/contraction. Endogenous tissue inhibitors of metalloproteinases (TIMPs) reduce excessive proteolytic ECM degradation by MMPs. The balance between MMPs and TIMPs plays a major role in vascular remodeling, angiogenesis, and the uterine and systemic vasodilation during normal pregnancy. An imbalance in the MMPs/TIMPs activity ratio may underlie the pathogenesis of vascular diseases such as abdominal aortic aneurysm, varicose veins, hypertension and preeclampsia. Downregulation of MMPs using genetic manipulations of endogenous TIMPs, or synthetic pharmacological inhibitors such as BB-94 (Batimastat) and doxycycline, and Ro-28-2653, a more specific inhibitor of gelatinases and membrane type 1-MMP, could be beneficial in reducing the MMP-mediated vascular dysfunction and the progressive vessel wall damage associated with vascular disease.

[The role of matrix metalloproteinases and tissue inhibitors of metalloproteinases in invasion of tumours of neuroepithelial tissue]

Tumour invasion requires degradation of extracellular matrix components and migration of cells through degraded structures into surrounding tissues. Matrix metalloproteinases (MMP) constitute a family of zinc and calcium-dependent endopeptidases that play a key role in the breakdown of extracellular matrix, and in processing of cytokines, growth factors, chemokines and cell surface receptors. Their activity is regulated at the levels of transcription, activation and inhibition by tissue inhibitors of metalloproteinases (TIMP). Changes in expression of MMP and TIMP are implicated in tumour invasion, because they may contribute to both migration of tumour cells and angiogenesis. Alterations of MMP expression observed in brain tumours arouse interest in the development and evaluation of synthetic matrix metalloproteinase inhibitors as antitumour agents.

Emerging targets and novel strategies in the treatment of AIDS-related Kaposi's sarcoma: bidirectional translational science

Through the mentorship process, Dr. Arthur Pardee emphasized the critical importance of bidirectional translational research-not only advancing drug development from bench to bedside, but also bringing back precious clinical material to the laboratory to assess the biologic effects of therapeutic agents on their targets. This mini-review focuses on the signal transduction pathways of Kaposi's sarcoma (KS) and on how the knowledge of such pathways has led to the rational development of molecularly targeted pathogenesis-driven therapies. Acquired immune deficiency syndrome (AIDS) related-KS results from co-infection with human immunodeficiency virus and KS herpesvirus/human herpesvirus-8 (KSHV/HHV8), which leads to the development of an angiogenic-inflammatory state that is critical in the pathogenesis of KS. KS is driven by KSHV/HHV8-specific pathways, which include viral G protein-coupled receptor (vGPCR), viral interleukin-6 (vIL-6), and viral chemokine homologues. In addition, cellular growth/angiogenic pathways, such as vascular endothelial growth factor (VEGF), insulin-like growth factor, platelet-derived growth factor (PDGF), angiopoietin and matrix metalloproteinases (MMPs) are "pirated" by KSHV/HHV8. As a very tangible example of how translational research has led to a marked improvement in patient outcome, the signal transduction inhibitor imatinib (a tyrosine kinase inhibitor of c-kit and PDGF) was administered to patients with KS whose tumors were serially biopsied. Not only did the patients' tumors regress, but also the regression was correlated with the inhibition of PDGF receptor (PDGFR) in the biopsy samples. Recent and future clinical trials of molecularly targeted therapy for the treatment of KS are a prelude to a shift in the paradigm of how KS is managed.

The use of tissue inhibitors of matrix metalloproteinases to increase the efficacy of a tumor necrosis factor/interferonγ antitumor therapy

Owing to its impressive ability to kill tumor cells, especially in combination with interferon-gamma (IFNgamma), tumor necrosis factor (TNF) is widely appreciated as being a potential systemic therapeutic for the treatment of cancer. On the other hand, owing to its proinflammatory activities, administration of TNF leads to many systemic side effects and eventually to a potentially lethal systemic inflammatory response syndrome (SIRS). However, systemic treatment of tumor-bearing mice with TNF/IFNgamma in combination with BB-94 (a broad-spectrum metalloproteinase inhibitor) confers protection against TNF/IFNgamma-induced mortality, whereas preserving the antitumor activity. In this study, we investigated the effect of the adenoviral delivery of human tissue inhibitors of matrix metalloproteinase (hTIMP)-1 and hTIMP-2 genes on the outcome of TNF/IFNgamma antitumor therapy. The dose of adenovirus was limited to 10(8) PFU per mouse owing to the additive toxicity of combining it with TNF/IFNgamma therapy. Nevertheless, this dose was sufficient to achieve highly efficient adenoviral transfer and expression of hTIMP-1 and hTIMP-2 in the liver, but not the tumor. Treatment with this low dose of AdhTIMP-1 or AdhTIMP-2 was not enough to protect the host against the toxic effects of TNF/IFNgamma. However, it was sufficient to show a synergistic effect of hTIMPs with TNF/IFNgamma such that tumors regressed significantly faster. Interestingly, only AdTIMP-2 was able to prevent relapses after treatment.

Adenovirus-mediated expression of TIMP-1 and TIMP-2 in bone inhibits osteolytic degradation by human prostate cancer

Matrix metalloproteinases (MMPs) are proteolytic enzymes that play critical roles in the pathogenesis of human cancers. Clinical trials using synthetic small molecule MMP inhibitors have been carried out but with little success. Tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors that block the extracellular matrix-degrading activity of MMPs. Here, we investigated the possibilities of genetically modifying human bones with TIMPs to create a high-TIMP bone microenvironment, which is hostile to metastatic prostate cancer cells using adenovirus-mediated gene transfer technology and SCID-hu end-organ colonization mouse model. Two strategies were used to achieve bone-specific TIMP expression: (i) ex vivo bone adenoviral infection followed by in vivo bone implantation; and (ii) ex vivo BMS cell infection followed by injection into in vivo implanted human fetal bones. PC-3 prostate cancer cells were injected into human fetal bones 4 weeks after implantation in SCID mice. In vitro, adenovirus-mediated expression of TIMP-1 or TIMP-2 in bone fragments inhibited MMP-2 activity, bone turnover and prostate cancer cell-induced proteolytic degradation as determined by gelatin zymography, calcium measurement and DQ protein quenched fluorescence assay, respectively. In vivo, immunohistochemistry confirmed TIMP-2 expression in AdTIMP-2-infected bone implants 4 weeks after implantation in SCID mice. Mice receiving AdTIMP-treated bone fragments showed significantly reduced PC-3-induced osteolysis, osteoclast recruitment and bone turnover in the implanted bones. We propose that adenoviral gene transfer of TIMP-1 and TIMP-2 can prevent the proteolytic activity of prostate cancer cells in bone and that enhancing anti-proteolytic defense mechanisms in target organs represents a promising form of prostate cancer gene therapy.

Signal transduction targets in Kaposi's sarcoma

PURPOSE OF REVIEW

AIDS-related Kaposi's sarcoma results from co-infection with HIV and Kaposi's sarcoma herpesvirus/human herpesvirus-8, which leads to the development of an angiogenic-inflammatory state that is critical in the pathogenesis of the condition. Recent discoveries regarding Kaposi's sarcoma herpesvirus/human herpesvirus-8 infection and its activation of signal transduction have led to a greater understanding into Kaposi's sarcoma pathogenesis and have identified potential targets for therapy.

RECENT FINDINGS

Kaposi's sarcoma is driven by Kaposi's sarcoma herpesvirus/human herpesvirus-8-specific pathways, which include viral G protein-coupled receptor, viral IL-6, and viral chemokine homologues. In addition, cellular growth/angiogenic pathways such as vascular endothelial growth factor, insulin growth factor, platelet-derived growth factor, angiopoietin and matrix metalloproteinases are 'pirated' by Kaposi's sarcoma herpesvirus/human herpesvirus-8. Recent findings show Kaposi's sarcoma herpesvirus/human herpesvirus-8 specific signaling pathways and pirated pathways to be important therapeutic targets.

SUMMARY

Numerous advances have been made recently that expand the understanding of Kaposi's sarcoma pathogenesis. These findings and recent clinical trials of targeted therapy for treatment are a prelude to a shift in the paradigm of how AIDS-related Kaposi's sarcoma is managed.

Cancer gene therapy targeting angiogenesis: An updated Review

Since the relationship between angiogenesis and tumor growth was established by Folkman in 1971, scientists have made efforts exploring the possibilities in treating cancer by targeting angiogenesis. Inhibition of angiogenesis growth factors and administration of angiogenesis inhibitors are the basics of anti-angiogenesis therapy. Transfer of anti-angiogenesis genes has received attention recently not only because of the advancement of recombinant vectors, but also because of the localized and sustained expression of therapeutic gene product inside the tumor after gene transfer. This review provides the up-to-date information about the strategies and the vectors studied in the field of anti-angiogenesis cancer gene therapy.

Gene therapy targeting to tumor endothelium

Tumor-associated vasculature is a relatively accessible component of solid cancers that is essential for tumor survival and growth, providing a vulnerable target for cancer gene therapy administered by intravenous injection. Several features of tumor-associated vasculature are different from normal vasculature, including overexpression of receptors for angiogenic growth factors, markers of vasculogenesis, upregulation of coagulation cascades, aberrant expression of adhesion molecules and molecular consequences of hypoxia. Many of these differences provide candidate targets for tumor-selective 'transductional targeting' of genetically- or chemically modified vectors and upregulated gene expression can also enable 'transcriptional targeting', regulating tumor endothelia-selective expression of transgenes following nonspecific gene delivery. Tumor vasculature also represents an important site of therapeutic action by the secreted products of antiangiogenic gene therapies that are expressed in non-endothelial cells. In this review we assess the challenges faced and the vectors that may be suitable for gene delivery to exploit these targets. We also overview some of the strategies that have been developed to date and highlight the most promising areas of research.

Evaluation of an improved tissue inhibitor of metalloproteinase 1 dual monoclonal sandwich immunoassay

BACKGROUND

It has previously been shown that increased levels of plasma tissue inhibitor of metalloproteinase 1 (TIMP-1) is associated with shorter survival for patients with colorectal cancer (CRC). Furthermore, plasma TIMP-1 levels have been found to be elevated in patients with early-stage CRC.

OBJECTIVE

It was the aim of this study to develop a new dual monoclonal antibody (mAb) sandwich immunoassay for TIMP-1 in order to achieve better resolution of non-cancer and cancer plasma specimens.

METHODS

Chemiluminescence immunoassay techniques were used to screen 240 combinations of TIMP-1 mAbs for their ability to interact with each other and to allow for further characterization of the sandwiching antibody pairs. Five mAb pair combinations were selected for assessment of their ability to resolve non-cancerous and cancerous plasma specimens by TIMP-1 measurement. Based on this testing, a final assay format was chosen for further validation. The results for the final assay were compared with measurements obtained in a TIMP-1 ELISA that had previously demonstrated the ability to resolve healthy blood donors and CRC specimens.

RESULTS

The clinical results support that the new dual monoclonal immunoassay has statistical discrimination equivalent to the ELISA. Additionally, the immunoassay had a high reproducibility and specificity.

CONCLUSION

The clinical evaluation of five TIMP-1 immunoassays resulted in the development of a new immunoassay. The new TIMP-1 immunoassay showed superior analytical performance to our previously used ELISA.

Signal transducers and activators of transcription-3 up-regulates tissue inhibitor of metalloproteinase-1 expression and decreases invasiveness of breast cancer

Signal transducers and activators of transcription (STAT)-3 is an oncogenic protein that is constitutively activated in many human cancers, including 30 to 60% of primary breast cancer. The biological significance of STAT3 activation in breast cancer is not fully understood. We have previously shown that STAT3 up-regulates tissue inhibitors of metalloproteinase (TIMP)-1, a cytokine known to block metalloproteinases and decrease invasiveness in certain cancer cell types. We hypothesize that STAT3 activation may modulate tumor invasiveness of breast cancer by regulating TIMP1 expression. Using MCF-7 cells transfected with tetracycline-off STAT3C (constitutively active STAT3), we generated an in vitro system in which STAT3C levels can be tightly controlled in breast cancer cells. Increasing tetracycline levels gradually decreased STAT3C and TIMP1 in a dose-dependent manner, and down-regulation of these proteins led to a reciprocal decrease in invasiveness of these cells in Matrigel. Addition of a neutralizing anti-TIMP1 antibody increased invasiveness in the same experimental system. Using immunohistochemistry and 142 primary breast tumors, we found a significant association between the expression of the phosphorylated/active form of STAT3 (pSTAT3) and that of TIMP1. Importantly, STAT3 activation correlated significantly with a lower frequency of vascular and lymphatic invasion (P = 0.015 and P = 0.0002, respectively). Our data support the concept that STAT3 activation significantly modulates the biological and clinical behavior of breast cancer.

Tissue fibrosis and carcinogenesis: divergent or successive pathways dictate multiple molecular therapeutic targets for oligo decoy therapies

The extracellular matrix (ECM) is composed of several families of macromolecular components: fibrous proteins such as collagens, type I collagen (COL1), type III collagen (COL3), fibronectin, elastin, and glycoconjugates such as proteoglycans and matrix glycoproteins. Their receptors on the cell membrane, most of which in the case of the ECM belong to the integrins, which are heterodimeric proteins composed of alpha and beta chains. COL1 is the major fibrous collagen of bone, tendon, and skin; while COL3 is the more pliable collagen of organs like liver. Focus will not only be given to the regulation of synthesis of several fibrogenic parameters but also modulation of their degradation during growth factor-induced tissue fibrosis and cancer development. Evidence will be provided that certain tissues, which undergo fibrosis, also become cancerous. Why does there exist a divergency between tissues, which undergo frank fibrosis as an endpoint, and those tissues that undergo fibrosis and subsequently are susceptible to carcinogenicity; resulting from the etiological factor(s) causing the initial injury? For example, why does a polyvinyl alcohol (PVA) sponge implant become encapsulated and filled with fibrous tissue then fibrosis tissue growth stops? Why does the subcutaneous injection of a fibrogenic growth factor cause a benign growth and incisional wounding results in fibrosis and ultimately scarring? There are many examples of tissues, which undergo fibrosis as a prerequisite to carcinogenesis. Is there a cause-effect relationship? If you block tissue fibrosis in these precancerous tissues, would you block cancer formation? What are the molecular targets for blocking fibrosis and ultimately carcinogenesis? How can oligo decoys may be used to attenuate carcinogenesis and which oligo decoys specifically attenuate fibrogenesis as a prelude to carcinogenesis? What are other molecular targets for oligo decoy therapy in carcinogenesis?

Adeno-associated virus vectors: potential applications for cancer gene therapy

Augmenting cancer treatment by protein and gene delivery continues to gain momentum based on success in animal models. The primary hurdle of fully exploiting the arsenal of molecular targets and therapeutic transgenes continues to be efficient delivery. Vectors based on adeno-associated virus (AAV) are of particular interest as they are capable of inducing transgene expression in a broad range of tissues for a relatively long time without stimulation of a cell-mediated immune response. Perhaps the most important attribute of AAV vectors is their safety profile in phase I clinical trials ranging from CF to Parkinson's disease. The utility of AAV vectors as a gene delivery agent in cancer therapy is showing promise in preclinical studies. In this review, we will focus on the basic biology of AAV as well as recent progress in the use of this vector in cancer gene therapy.

GPI-anchored TIMP-1 treatment renders renal cell carcinoma sensitive to FAS-meditated killing

The resistance of tumours to immune-mediated lysis has been linked to the biology of matrix metalloproteinases (MMPs), and specifically to the cell surface expression of MMPs by the tumour cell. The endogenous tissue inhibitors of metalloproteinases (TIMPs) exhibit diverse physiological/biological functions including the moderation of tumour growth, metastasis and apoptosis. These biologic activities are mediated in part by the stoichiometry of TIMP/MMP/cell surface protein interactions. A glycosylphosphatidylinositol (GPI) anchor was fused to TIMP-1 to focus defined concentrations of this inhibitory protein on the surface of three renal cell carcinoma (RCC) cell lines (RCC-26, RCC-53 and A498) independently of cell surface protein-protein interactions. Exogenously added TIMP-1-GPI efficiently inserted into the RCC cell membrane and dramatically altered the association of MMPs with the cell surface. TIMP-1-GPI treatment inhibited RCC proliferation and rendered the normally FAS-resistant RCC cells sensitive to FAS-induced apoptosis but did not alter perforin-mediated lysis by cytotoxic effector cells. The increased sensitivity to FAS-mediated apoptosis correlated with an alteration in the balance of pro- and antiapoptotic BCL-2-family proteins. By interfering with the proliferative capacity and inducing sensitivity to immune effector mechanisms GPI-anchored TIMP-1 may represent a more effective version of the TIMP-1 protein for therapeutic strategies.

Treatment of human disease by adeno-associated viral gene transfer

During the past decade, in vivo administration of viral gene transfer vectors for treatment of numerous human diseases has been brought from bench to bedside in the form of clinical trials, mostly aimed at establishing the safety of the protocol. In preclinical studies in animal models of human disease, adeno-associated viral (AAV) vectors have emerged as a favored gene transfer system for this approach. These vectors are derived from a replication-deficient, non-pathogenic parvovirus with a single-stranded DNA genome. Efficient gene transfer to numerous target cells and tissues has been described. AAV is particularly efficient in transduction of non-dividing cells, and the vector genome persists predominantly in episomal forms. Substantial correction, and in some instances complete cure, of genetic disease has been obtained in animal models of hemophilia, lysosomal storage disorders, retinal diseases, disorders of the central nervous system, and other diseases. Therapeutic expression often lasted for months to years. Treatments of genetic disorders, cancer, and other acquired diseases are summarized in this review. Vector development, results in animals, early clinical experience, as well as potential hurdles and challenges are discussed.

Fusion of the Human Immunodeficiency Virus Type 1 Tat Protein Transduction Domain to Thymidine Kinase Increases Bystander Effect and Induces Enhanced Tumor KillingIn Vivo

The clinical success of suicide gene therapy using herpes simplex virus type 1 thymidine kinase (TK) is largely dependent on the capacity of this enzyme to effectively induce the death of bystander cells. We have shown that fusion of TK to an 11-amino acid peptide from the basic domain of the human immunodeficiency virus type 1 Tat protein (Tat11) imparts cell membrane-translocating ability to the enzyme and significantly increases its cytotoxic activity. Here we report on the efficacy of this strategy in two different mouse models of adoptive tumorigenesis, based on the implantation of human Kaposi sarcoma (KS-IMM) cells in nude mice or of B16F10 melanoma cells in syngeneic C57BL/6J mice. Experiments were performed by the subcutaneous injection of mixtures of unmodified tumor cells containing different fractions of TK or Tat11-TK producing cells followed by animal treatment with ganciclovir (GCV). In both systems we consistently found that mice bearing tumors containing Tat11-TK cells displayed significantly retarded tumor growth and prolonged survival as compared with mice inoculated with cells expressing unmodified TK. Collectively, these results demonstrate that fusion of Tat11 to TK imparts remarkable intercellular trafficking capability to the enzyme. This modification of TK might constitute an important step in the optimization of TK suicide gene strategy for gene therapy of cellular proliferation.

Potent inhibition of arterial intimal hyperplasia by TIMP1 gene transfer using AAV vectors

Seminal to the process of arterial restenosis after balloon angioplasty is extracellular matrix degradation by metalloproteinases (MMPs); activity of these proteins is strongly inhibited by the tissue inhibitors of MMPs (TIMPs). Here we exploit gene transfer using an adeno-associated virus (AAV) for TIMP1 gene delivery in a rat model of intimal hyperplasia. High-titer AAV-Timp1 efficiently transduced human coronary artery smooth muscle cells (SMCs) in vitro and inhibited the capacity of these cells to migrate through a Matrigel barrier. In injured rat carotid arteries, AAV vectors were found to transduce SMCs efficiently and to maintain transgene expression for several weeks in vivo. In AAV-Timp1-transduced animals, the intima:media ratio of injured carotids was significantly reduced by 70.5% after 2 weeks, by 58.5% after 1 month, and by 52.4% after 2 months from treatment. The decrease in intimal hyperplasia was paralleled by a significant inhibition of collagen accumulation and by increased elastin deposition in the neointima, two findings that relate to the inhibition of MMP activity. These results indicate that AAV vectors are efficient tools for delivering genes to the arterial wall and emphasize the importance of MMPs for the generation of intimal hyperplasia. Local TIMP1 gene transfer might thus represent an efficient strategy to prevent restenosis.

Advances in the pathobiology and treatment of Kaposi sarcoma

PURPOSE OF REVIEW

Kaposi sarcoma, which has reached epidemic proportions in parts of Africa and in the Western world, continues to pose a problem in patients with AIDS receiving highly active antiretroviral therapy (HAART). This article reviews the new and important information regarding the epidemiology, biology, and management of Kaposi sarcoma that was published in the last year.

RECENT FINDINGS

Worldwide Kaposi sarcoma herpesvirus/human herpesvirus 8 (HHV8) seropositivity has been found to exceed the incidence of Kaposi sarcoma. Therefore, investigators have justifiably implicated other cofactors (eg, blood-sucking arthropods, angiotensin converting enzyme inhibitors, hemodialysis, and iron) in the development of Kaposi sarcoma. In the transplant setting, Kaposi sarcoma lesions have been shown to originate from the engraftment of donor tumor cells. The detection of HHV8 in Kaposi sarcoma lesions has provided a new diagnostic tool to help differentiate Kaposi sarcoma from its mimics. Kaposi sarcoma lesional cells, now confirmed to be of lymphatic origin, have been shown to express several chemokine receptors, some of which may help explain the predilection for skin. Regression of Kaposi sarcoma has been characterized histologically for the first time. The finding that some tumor cells can remain in an atrophic state even in completely regressed lesions suggests that they have the potential to recur. Protease inhibitor-based and nonnucleoside reverse transcriptase inhibitor-based HAART regimens have been verified to be similarly effective. Although antiretrovirals have been noted to favorably alter the clinical characteristics of Kaposi sarcoma favorably, they seem not to alter the natural history of this disease. In the HAART era, because CD4 cell count was shown no longer to provide prognostic information about AIDS-related Kaposi sarcoma, the traditional classification system for staging AIDS-related Kaposi sarcoma has been refined. Also, a new staging system for classic Kaposi sarcoma has been proposed.

SUMMARY

Numerous advances have emerged regarding Kaposi sarcoma during the last year, many of which still need to be translated into clinically useful information. The results of new clinical trials involving antivirals purposely directed against HHV8 and antiretrovirals for HIV-uninfected people are anticipated. Finally, although investigators during this period did provide us with additional potential therapeutic targets, more novel approaches such as RNA interference and gene therapy have been also proposed as options in the future management of Kaposi sarcoma.