Randomized Phase II Trial of Matrix Metalloproteinase Inhibitor COL-3 in AIDS-Related Kaposi's Sarcoma: An AIDS Malignancy Consortium Study

Review of latent and lytic phase biomarkers in Kaposi's sarcoma

INTRODUCTION

Kaposi's sarcoma (KS) is a vascular neoplasm with distinct clinical-epidemiological subtypes and varied clinical presentations. While the association of KS with human herpesvirus-8 (HHV8, KSHV) infection is well known, additional factors are needed for tumorigenesis. The precise sequence of events involved in KS development, progression and regression continues to be investigated. The discovery of KSHV biomarkers is helpful for diagnostic purposes, for understanding KS pathogenesis and for identifying potential druggable targets.

AREAS COVERED

This article reviews a number of key biomarkers relevant for the diagnosis of KS and HHV8-related pathogenesis. New developments in KS, potential therapeutic targets and the challenges involved in their discovery are highlighted.

EXPERT OPINION

Although there is currently no cure for KS, continued research devoted to uncovering biomarkers and understanding their pathogenic roles remains encouraging. The hope is that sometime soon one of these candidate targets will provide a curative therapy for this enigmatic sarcoma.

Biotic acts of antibiotics

Biological functions of antibiotics are not limited to killing. The most likely function of antibiotics in natural microbial ecosystems is signaling. Does this signaling function of antibiotics also extend to the eukaryotic – in particular mammalian – cells? In this review, the host modulating properties of three classes of antibiotics (macrolides, tetracyclines, and β-lactams) will be briefly discussed. Antibiotics can be effective in treatment of a broad spectrum of diseases and pathological conditions other than those of infectious etiology and, in this capacity, may find widespread applications beyond the intended antimicrobial use. This use, however, should not compromise the primary function antibiotics are used for. The biological background for this inter-kingdom signaling is also discussed.

Potential clinical applications of matrix metalloproteinase inhibitors and their future prospects

Matrix metalloproteinases (MMPs) are endopeptidases that are involved in extracellular matrix degradation. They are also implicated in a number of abnormal bioprocesses, such as tumor growth, invasion, and metastasis. Therefore, controlling MMP activities has generated considerable interest as a possible therapeutic target. The tissue inhibitors of metalloproteinases (TIMPs) are the major naturally occurring proteins that specifically inhibit MMPs and assist in maintaining the balance between extracellular matrix destruction and formation. However, TIMPs are probably not suitable for pharmacological applications due to their short half-lives in vivo. During the last few decades, synthetic MMP inhibitors (MMPIs) have undergone rapid clinical development in attempts to control MMP enzymatic activities in abnormal bioprocesses. Although studies with these agents have met with limited clinical success, the field of MMPIs is still expanding, and generation of highly effective and selective MMPIs might be a promising direction of this research area.

Non-antibiotic properties of tetracyclines and their clinical application in dermatology

Dermatologists have used tetracyclines since the 1950s to treat disorders that do not necessarily have an infectious aetiology. Their anti-inflammatory and anti-collagenase properties contribute significantly to their success in treating diseases such as rosacea and acne. This article reviews the non-antibiotic properties of tetracyclines and their clinical application in dermatology.

COL-3, a chemically modified tetracycline, inhibits lipopolysaccharide-induced microglia activation and cytokine expression in the brain

Microglia activation results in release of proinflammatory molecules including cytokines, which contribute to neuronal damage in the central nervous system (CNS) if not controlled. Tetracycline antibiotics such as minocycline inhibit microglial activation and cytokine expression during CNS inflammation. In the present study we found that administration of chemically modified tetracycline-3 (COL-3), inhibits lipopolysaccharide (LPS)-induced microglial and p38 MAPK activation, as well as the increase in TNF-α, but not IL-1β expression, in the brains of BALB/c mice. COL-3 has been described to have no antibacterial activity. We observed that COL-3 had no activity against a Gram-negative bacteria, Escherichia coli; however surprisingly, COL-3 had antibacterial activity against a Gram-positive bacteria Staphylococcus aureus, with a minimum inhibitory concentration of 1 mg/ml. Our data show that COL-3 has some antibacterial activity against S. aureus, inhibits LPS-induced neuroinflammation, and displays potential as a therapeutic agent for treatment of conditions involving CNS inflammation.

Human herpesvirus-8: Kaposi sarcoma, multicentric Castleman disease, and primary effusion lymphoma

Human herpesvirus 8 (HHV8) is a gamma herpesvirus associated with Kaposi sarcoma, multicentric Castleman disease, and primary effusion lymphoma, lymphoproliferative diseases that are most commonly observed in immunocompromised individuals. The viral genome expresses genes responsible for inhibition of apoptosis, cell cycle entry, and angiogenesis. Viral homologs of human regulatory genes are expressed, providing stimuli for angiogenesis, B-cell proliferation, and immune evasion. Variations in expression of these factors give rise to the 3 known HHV8-associated malignancies. Identification of these pathogenetic mechanisms has led to exploration of targeted treatment approaches for all 3 of these disorders with success in Kaposi sarcoma and multicentric Castleman disease; primary effusion lymphoma remains a clinical challenge.

Matrix metalloproteinase inhibitor COL-3 prevents the development of paclitaxel-induced hyperalgesia in mice

OBJECTIVE

To study the potential of chemically modified tetracycline-3 (COL-3), a potent matrix metalloproteinase (MMP) inhibitor, to protect against the development of paclitaxel-induced painful neuropathy and its immunomodulatory effects.

MATERIALS AND METHODS

The reaction latency to thermal stimuli (hot plate test) of female BALB/c mice was recorded before and after treatment with paclitaxel (2 mg/kg i.p.), paclitaxel plus COL-3 (4, 20 or 40 mg/kg p.o.) or their vehicles for 5 consecutive days. Gene transcripts of CD11b (marker for microglia), 5 cytokines (IFN-γ, IL-1β, IL-6, IL-10 and TNF-α) and 3 chemokines (CCL2, CXCL10 and CX3CL1) were quantified by real-time PCR in the brains, spinal cords and spleens of mice sacrificed on day 7 after treatment.

RESULTS

Treatment with paclitaxel reduced the reaction latency time to thermal stimuli (thermal hyperalgesia) for 4 weeks, with maximum effect on days 7 and 10. The coadministration of paclitaxel with COL-3 40 mg/kg, but not lower doses, prevented the development of paclitaxel-induced thermal hyperalgesia. Treatment with paclitaxel alone or coadministration with COL-3 increased CD11b transcript levels in the brain but not in the spinal cord. Treatment with paclitaxel reduced IL-6 transcript levels in the spinal cord but did not alter the transcript levels of other cytokines or chemokines in the brain, spinal cord or spleen. The coadministration of COL-3 with paclitaxel significantly increased the transcript levels of IL-6 in the spleen and decreased CX3CL1 transcripts in the brain in comparison to treatment with paclitaxel alone.

CONCLUSION

Our results indicate that the MMP inhibitor COL-3 protected against paclitaxel-induced thermal hyperalgesia and, thus, could be useful in the prevention of chemotherapy-induced painful neuropathy.

Non-antibacterial tetracycline formulations: clinical applications in dentistry and medicine

In 1983, it was first reported that tetracyclines (TCs) can modulate the host response, including (but not limited to) inhibition of pathologic matrix metalloproteinase (MMP) activity, and by mechanisms unrelated to the antibacterial properties of these drugs. Soon thereafter, strategies were developed to generate non-antibacterial formulations (subantimicrobial-dose doxycycline; SDD) and compositions (chemically modified tetracyclines; CMTs) of TCs as host-modulating drugs to treat periodontal and other inflammatory diseases. This review focuses on the history and rationale for the development of: (a) SDD which led to two government-approved medications, one for periodontitis and the other for acne/rosacea and (b) CMTs, which led to the identification of the active site of the drugs responsible for MMP inhibition and to studies demonstrating evidence of efficacy of the most potent of these, CMT-3, as an anti-angiogenesis agent in patients with the cancer, Kaposi's sarcoma, and as a potential treatment for a fatal lung disease (acute respiratory distress syndrome; ARDS). In addition, this review discusses a number of clinical studies, some up to 2 years' duration, demonstrating evidence of safety and efficacy of SDD formulations in humans with oral inflammatory diseases (periodontitis, pemphigoid) as well as medical diseases, including rheumatoid arthritis, post-menopausal osteopenia, type II diabetes, cardiovascular diseases, and a rare and fatal lung disease, lymphangioleiomyomatosis.

ADAM28 is elevated in humans with the metabolic syndrome and is a novel sheddase of human tumour necrosis factor-α

Metalloproteinases are implicated in cleaving numerous proinflammatory mediators from the cell surface. Interestingly, the elevated levels of tumour necrosis factor-α (TNF-α) have been associated with the metabolic syndrome. We aimed to ascertain whether the human metalloproteinase ADAM28 correlates with parameters of the metabolic syndrome and whether ADAM28 is a novel sheddase of human TNF-α. To identify novel metalloproteinases associated with the metabolic syndrome, we conducted microarray studies on peripheral blood mononuclear cells from a well characterised human cohort. Human ADAM28 and TNF-α were overexpressed and ADAM28 expression or activity was reduced with small-interfering RNA (siRNA) or pharmacological inhibition. TNF-α levels were measured in cell supernatant by enzyme-linked immunosorbent assay. We also conducted ADAM28 inhibition studies in human THP-1 macrophages. Human ADAM28 expression levels were positively correlated with parameters of the metabolic syndrome. When human ADAM28 and TNF-α were overexpressed in HEK293 cells, both proteins co-localised, co-immunoprecipitated and promoted TNF-α shedding. The shedding was significantly reduced when ADAM28 activity was inhibited or ADAM28 expression was downregulated. In human THP-1 macrophages, endogenous ADAM28 and TNF-α were co-expressed and TNF-α shedding was significantly reduced when ADAM28 was inhibited by pharmacological inhibition or siRNA knockdown. Our data suggest a novel mechanistic role for the metalloproteinase ADAM28 in inflammation, obesity and type 2 diabetes.

Chemically modified tetracyclines: Novel therapeutic agents in the management of chronic periodontitis

Chronic periodontitis is a complex infection initiated by gram-negative bacteria which destroy the supporting structures of the tooth. Recently, it has been recognized that it is the host response to bacterial infection which causes greater destruction of the connective tissue elements, periodontal ligament and alveolar bone in periodontitis. This has led to the development of various host modulating approaches to target cells and their destructive mediators involved in tissue degradation. Chemically modified tetracyclines (CMTs) are derivatives of tetracycline group of drugs which lack antimicrobial action but have potent host modulating affects. They inhibit pathologically elevated matrix metal loproteinases, pro-inflammtory cytokines and other destructive mediators. Bone resorption is also suppressed due to their combined anti-proteinase and apoptotic affects on osteoblasts and osteoclasts, respectively. Development of resistant bacteria and gastrointestinal toxicity seen with parent tetracyclines is not produced by CMTs. Hence, CMTs are viewed as potential therapeutic agents in the management of chronic diseases like periodontitis that involve destruction of connective tissue and bone.

Phase II study of bevacizumab in patients with HIV-associated Kaposi's sarcoma receiving antiretroviral therapy

PURPOSE

Alternatives to cytotoxic agents are desirable for patients with HIV-associated Kaposi's sarcoma (KS). Vascular endothelial growth factor-A (VEGF-A) contributes to KS pathogenesis. We evaluated the humanized anti-VEGF-A monoclonal antibody, bevacizumab, in patients with HIV-KS.

PATIENTS AND METHODS

Patients with HIV-KS who either experienced progression while receiving highly active antiretroviral therapy (HAART) for at least 1 month or did not regress despite HAART for at least 4 months were administered bevacizumab 15 mg/kg intravenously on days 1 and 8 and then every 3 weeks. The primary objective was assessment of antitumor activity using modified AIDS Clinical Trial Group (ACTG) criteria for HIV-KS. HIV-uninfected patients were also eligible and observed separately.

RESULTS

Seventeen HIV-infected patients were enrolled. Fourteen patients had been receiving effective HAART for at least 6 months (median, 1 year). Thirteen patients had advanced disease (ACTG T(1)), 13 patients had received prior chemotherapy for KS, and seven patients had CD4 count less than 200 cells/μL. Median number of cycles was 10 (range, 1 to 37 cycles); median follow-up was 8.3 months (range, 3 to 36 months). Of 16 assessable patients, best tumor responses observed were complete response (CR) in three patients (19%), partial response (PR) in two patients (12%), stable disease in nine patients (56%), and progressive disease in two patients (12%). Overall response rate (CR + PR) was 31% (95% CI, 11% to 58.7%). Four of five responders had received prior chemotherapy for KS. Over 202 cycles, grade 3 to 4 adverse events at least possibly attributed to therapy included hypertension (n = 7), neutropenia (n = 5), cellulitis (n = 3), and headache (n = 2).

CONCLUSION

Bevacizumab is tolerated in patients with HIV-KS and has activity in a subset of patients.

KSHV activation of VEGF secretion and invasion for endothelial cells is mediated through viral upregulation of emmprin-induced signal transduction

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of Kaposi's sarcoma (KS)-one of the most common tumors arising in the setting of immune suppression. Hallmarks of KS lesions include KSHV-infected cells of endothelial lineage and neoangiogenesis. Promigratory factors secreted in the tumor microenvironment by KSHV-infected cells promote endothelial cell (EC) migration and angiogenesis but existing therapies targeting these pathways are not widely utilized. This underscores the need for additional characterization of KSHV-host interactions relevant to EC pathogenesis to identify new therapeutic targets. We recently demonstrated that de novo infection by KSHV promotes EC invasion through upregulation of extracellular matrix metalloproteinase inducer (emmprin)-a multifunctional glycoprotein previously shown to induce tumor cell invasion and regional angiogenesis through upregulation of signal transduction and promotion of tumor-stroma interactions. This study was undertaken to determine whether EC invasion for KSHV-infected cells is induced through activation of specific signal transduction pathways and proangiogenic factors by emmprin. We found that KSHV activation of emmprin induces PI3K/Akt- and mitogen-activated protein kinase (MAPK)-dependent secretion of vascular endothelial growth factor (VEGF). Functionally, EC invasion following de novo infection is induced by emmprin-dependent PI3K/Akt and MAPK activation of VEGF. These findings support the potential utility of targeting emmprin for reducing VEGF secretion and EC migration in the KS microenvironment.

Non-antibacterial tetracyclines modulate mediators of periodontitis and atherosclerotic cardiovascular disease: a mechanistic link between local and systemic inflammation

Periodontitis, one of the most common chronic inflammatory diseases afflicting man, is increasingly being recognized as a risk factor for atherosclerotic cardiovascular disease (ASCVD). Non-antimicrobial tetracyclines are known to have inhibitory effects on inflammatory mediators and effector molecules, including cytokines and matrix metalloproteinases (MMPs), associated with both diseases. In this paper, we discuss the evidence that doxycycline and related non-antibiotic chemically modified tetracyclines (e.g., CMT-3) can effectively reduce cytokine (TNF-α, IL-6, and MCP-1) production by human mononuclear inflammatory cells when stimulated either by endotoxin (LPS) or by a complex of C-reactive protein/oxidized LDL cholesterol relevant to the pathogenesis of periodontal disease and ASCVD, respectively. This inhibition by tetracycline compounds appears to be mediated at least in part by a suppression of the phosphorylation/activation of the NFκB cell signaling pathway. We are currently conducting clinical trials on patients who exhibit both diseases, and our preliminary data suggest that virtually all acute coronary syndrome (ACS) patients exhibit moderate-to-severe periodontitis, a higher incidence of this oral inflammatory disease than that seen in the population at large. In other studies, a non-antimicrobial formulation of doxycycline (SDD) has been found to dramatically reduce hsCRP, IL-6 and MMP-9 levels in plasma of ACS patients, and SDD has also been found to significantly increase serum levels of both cardio-protective HDL cholesterol and its core molecule apolipoprotein A-I in ASCVD-vulnerable patients with periodontitis. Our current research suggests that one mechanism involved may be the ability of SDD to inhibit MMP-mediated HDL loss by protecting apolipoprotein A-I from proteinase attack. These pleiotropic mechanisms of non-antimicrobial tetracyclines provide significant therapeutic potential to treat chronic inflammatory diseases including both periodontitis and ASCVD.

Viral oncogenesis and its role in nonmelanoma skin cancer

In recent years, the contribution of viruses to cutaneous oncogenesis has steadily gained recognition. The archetype is human herpesvirus 8, which is well established as the causative agent in Kaposi sarcoma. Other viruses believed to play a role in nonmelanoma skin cancer include human papillomavirus and the recently described Merkel cell polyomavirus. We review the mechanisms by which these three viruses interact with the host cell, ultraviolet radiation and immunosuppression to result in carcinogenesis.

Phase II AIDS Malignancy Consortium trial of topical halofuginone in AIDS-related Kaposi sarcoma

Using a novel blinded intrapatient vehicle control design, we conducted a phase II study of topically administered halofuginone, an angiogenesis inhibitor that inhibits collagen type-I and matrix metalloproteinases (MMPs), in patients with AIDS-related Kaposi sarcoma. Serial Kaposi sarcoma biopsies assessed treatment effects on angiogenic factors and Kaposi sarcoma herpesvirus-latency associated nuclear antigen-1 (KSHV-LANA). We observed marked heterogeneity of KSHV-LANA expression. Although the small number of subjects whose response could be evaluated precluded definitive assessment of halofuginone's efficacy, we observed a significant decrease in type-I collagen only in halofuginone-treated lesions, but no effect on MMP-2. The trial design is applicable to future studies of topical agents.

Using tetracyclines to treat osteoporotic/osteopenic bone loss: from the basic science laboratory to the clinic

Periodontitis (progressive inflammatory disease characterized by alveolar bone loss, a major cause of tooth loss worldwide) is associated with both systemic osteoporosis and its milder form, osteopenia. Tetracyclines, by virtue of their non-antimicrobial pro-anabolic and anti-catabolic properties, are excellent candidate pharmaceuticals to simultaneously treat these local and systemic disorders. This paper reviews the foundational basic science and translational research which lead to a pivotal multicenter randomized clinical trial in postmenopausal women with both periodontitis and systemic (skeletal) osteopenia. This trial was designed primarily to examine whether subantimicrobial dose doxycycline (SDD) could reduce progressive alveolar (oral) bone loss associated with periodontitis and, secondarily, whether SDD could reduce systemic bone loss in the same subjects. This paper describes the efficacy and safety findings from this clinical trial and also outlines future directions using this promising and novel approach to manage both oral and systemic bone loss.

Update on HHV-8-Associated Malignancies

The human herpesvirus 8 (HHV-8) is the oncogenic virus associated with Kaposi's sarcoma (KS) and lymphoproliferative disorders, namely, primary effusion lymphoma and multicentric Castleman's disease. KS is among the most common malignancies seen in HIV-infected patients despite the decreased incidence of KS in the era of highly active antiretroviral therapy. Advances in molecular pathology reveal HHV-8 tumorigenesis is mediated through molecular mimicry wherein viral-encoded proteins can activate several cellular signaling cascades while evading immune surveillance. This knowledge has led to the evolution of multiple therapeutic strategies against specific molecular targets. Many such therapeutic modalities have shown activity, but none have proven to be curative. Identifying possible prognostic factors is another active area of research. This review summarizes the recent developments in the fields of virus transmission, molecular biology, and treatment of HHV-8-related neoplasms.

The tetracycline resistome

Resistance to tetracycline emerged soon after its discovery six decades ago. Extensive clinical and non-clinical uses of this class of antibiotic over the years have combined to select for a large number of resistant determinants, collectively termed the tetracycline resistome. In order to impart resistance, microbes use different molecular mechanisms including target protection, active efflux, and enzymatic degradation. A deeper understanding of the structure, mechanism, and regulation of the genes and proteins associated with tetracycline resistance will contribute to the development of tetracycline derivatives that overcome resistance. Newer generations of tetracyclines derived from engineering of biosynthetic genetic programs, semi-synthesis, and in particular recent developments in their chemical synthesis, together with a growing understanding of resistance, will serve to retain this class of antibiotic to combat pathogens.

Target therapy in gastrointestinal tract sarcoma: What is new?

Soft tissue sarcoma are rare tumors arising mostly from embryonic mesoderm, that can affect almost any part of the human body, including the gastrointestinal tract. The prognosis associated with soft tissue sarcoma is still poor, mainly because of the low efficacy of traditional approaches based on surgery and chemotherapy. As a result of genetic and molecular analysis, several new target therapies have been developed, leading to a significant improvement in the survival of patients affected by advanced disease. In this review we aim to explore the therapeutic potential and benefit of target therapy in the management of gastrointestinal soft tissue sarcoma and the possible complications or pitfalls of such an approach.

Doxycycline [corrected] inhibits mononuclear cell-mediated connective tissue breakdown

Chronic periodontitis is the most common chronic inflammatory disease and has been associated with an increased risk for serious medical conditions including cardiovascular disease (CVD). Endotoxin (lipopolysaccharide), derived from periodontopathogens, can induce the local accumulation of mononuclear cells in the inflammatory lesion, increasing proinflammatory cytokines and matrix metalloproteinases (MMPs), resulting in the destruction of periodontal connective tissues including bone. In this study, we show that doxycycline, originally developed as a broad-spectrum tetracycline antibiotic (and, more recently, as a nonantimicrobial therapy for chronic inflammatory periodontal and skin diseases), can inhibit extracellular matrix degradation in cell culture mediated by human peripheral blood-derived monocytes/macrophages. The mechanisms include downregulation of cytokines and MMP-9 protein levels and the inhibition of the activities of both collagenase and MMP-9. These pleiotropic, but nonantibiotic, effects of doxycycline explain, at least in part, its therapeutic potential for various chronic inflammatory diseases including periodontitis, and may reduce the risks of systemic diseases (e.g. CVDs, less manageable diabetes) associated with this and other local diseases.

Targeted therapy for Kaposi sarcoma

Kaposi sarcoma (KS) occurs as a result of Kaposi sarcoma-associated herpesvirus (KSHV) infection, typically in the context of one of several immunodeficient states. In the US, patients with KS may either be co-infected with HIV or receiving immunosuppressant therapy following solid-organ transplantation. Systemic treatment of KS has traditionally involved one of several chemotherapeutic agents administered either in combination or as single agents, which typically provide reasonable response rates and short-term control. However, recurrence of KS is common, and progression-free intervals are under 1 year. For these reasons, new therapies have been sought and with the elucidation of novel pathogenic mechanisms of KS infection, rational therapeutic targets have been identified. These include KSHV replication, restoration of immune competence, and signal transduction pathways utilized by KSHV in the propagation of KS. This review focuses on these emerging targets in the treatment of patients with KS and also highlights important clinicopathologic characteristics.

New approaches to the treatment of human herpesvirus 8-associated disease

Human herpesvirus 8 (HHV-8, also known as Kaposi sarcoma-associated herpesvirus or KSHV) is the etiologic agent of Kaposi sarcoma (KS) and primary effusion lymphoma (PEL), as well as many cases of Castleman disease. Despite significant advances in understanding the biology and natural history of these diseases, current treatment options have important limitations, and strategies to prevent their development in high-risk individuals are lacking. This article reviews the scope of HHV-8-associated disease, as well as the efficacy of current treatment options. Finally, novel approaches to treatment and prevention are described, including antiviral agents, targeted molecular therapy and a combination of these modalities.

Matrix metalloproteinase inhibitors reduce collagen gel contraction and alpha-smooth muscle actin expression by periodontal ligament cells

BACKGROUND AND OBJECTIVE

Orthodontic tooth movement requires remodeling of the periodontal tissues. The matrix metalloproteinases (MMPs) degrade the extracellular matrix components of the periodontal ligament, while the tissue inhibitors of metalloproteinases (TIMPs) control their activity. Synthetic MMP inhibitors have been developed to inhibit MMP activity. In this study, periodontal ligament cells in contracting collagen gels served as a model for enhanced periodontal remodeling. The effect of MMP inhibitors on gel contraction and on MMP and TIMP expression was analyzed.

MATERIAL AND METHODS

Human periodontal ligament cells were cultured in three-dimensional collagen gels and incubated with the MMP inhibitors BB94, CMT-3, doxycycline and Ilomastat. Gel contraction was determined using consecutive photographs. The relative amounts of MMPs and TIMPs were analyzed using substrate zymography and mRNA expression using quantitative polyermase chain reaction.

RESULTS

All MMP inhibitors reduced MMP activity to about 20% of the control activity. They all reduced contraction, but CMT-3 and doxycycline had the strongest effect. These inhibitors also reduced MMP-2, MMP-3 and alpha-smooth muscle actin mRNA expression. The expression of MMP-1 mRNA seemed to be increased by CMT-3. No effects were found on the amounts of MMPs and TIMPs.

CONCLUSION

Synthetic MMP inhibitors strongly reduced gel contraction by periodontal ligament cells. This was primarily caused by an inhibitory effect on MMP activity, which reduces matrix remodeling. In addition, alpha-smooth muscle actin expression was reduced by CMT-3 and doxycycline, which limits the contractile activity of the fibroblasts.

Kaposi sarcoma: a continuing conundrum

Kaposi sarcoma (KS) remains a challenge. Its classic or Mediterranean form tends to be benign. In transplant recipients it may be less so. As part of the AIDS pandemic, of which it was an original defining component, it may be life-threatening. It is due to human herpesvirus-8, which is necessary but not sufficient to produce the disease. KS has a low prevalence in the general population of the United States and United Kingdom, with an intermediate rate in Italy and Greece, and a high one in parts of Africa. In Italy, hot spots include its southern regions, the Po River Valley, and Sardinia, possibly related to a high density of blood-sucking insects. An important challenge is to treat KS patients without immunocompromising them. The potential of effective anti-herpes virus therapy and the use of sirolimus in transplantation recipients have added new opportunities for KS prevention.

LEARNING OBJECTIVES

At the conclusion of this learning activity, participants should be able to provide the most recent information about Kaposi sarcoma in the context in which it occurs. Its classic or Mediterranean form, its pattern in transplant recipients and others iatrogenically immunosuppressed, and its occurrence as a potentially life-threatening part of the AIDS pandemic will be stressed. Its etiology and transmission will be discussed in detail to facilitate understanding of Kaposi sarcoma and of human herpesvirus-8 infection in the general population of the United States and United Kingdom, in Italy and Greece, and in certain parts of Africa. Its therapy, including the concept of doing it without immunocompromising the patient, will be stressed. New opportunities for Kaposi sarcoma prevention will also be discussed.

Natural products to drugs: natural product-derived compounds in clinical trials

Natural product and natural product-derived compounds that are being evaluated in clinical trials or are in registration (as at 31st December 2007) have been reviewed, as well as natural product-derived compounds for which clinical trials have been halted or discontinued since 2005. Also discussed are natural product-derived drugs launched since 2005, new natural product templates and late-stage development candidates.

Phase 1/2 trial of BMS-275291 in patients with human immunodeficiency virus-related Kaposi sarcoma: a multicenter trial of the AIDS Malignancy Consortium

BACKGROUND

Matrix metalloproteinases (MMPs) are overexpressed in Kaposi sarcoma (KS). The safety and efficacy of a novel, orally bioavailable MMP inhibitor, BMS-275291, was evaluated in patients with human immunodeficiency virus-associated KS and the correlation between changes in the percentage of apoptotic cells in tumor biopsies and response was explored.

METHODS

Cohorts of 6 patients were to be treated with BMS-275291. The initial cohort received 1200 mg once a day; subsequent doses were to be escalated to 600 mg twice daily and 1200 mg twice daily, or decreased to 600 mg/day. Tumor biopsies for apoptosis assays were collected pretreatment and on Day 29. Prospectively defined dose level adjustments were to be based on dose-limiting toxicity (DLT), tolerability, changes in the percentage of apoptotic cells, and treatment response.

RESULTS

Sixteen patients were enrolled; 15 received the study drug and could be evaluated. The median duration of treatment was 20 weeks (range, 3-54 weeks). A dose of 1200 mg once a day was well tolerated but induced only 1 response. A DLT occurred in 3 patients treated with 600 mg twice daily, and included grade 3 fatigue, grade 3 allergic reaction, and grade 3 arthralgias; 2 responses were noted at this dose level (toxicity was graded according to the National Cancer Institute Common Toxicity Criteria [version 2.0]). Based on predetermined endpoints, the trial was closed after accrual of 15 treated patients. Assessment of biologic response for dose escalation/de-escalation decisions utilizing the apoptosis assay was not feasible.

CONCLUSIONS

BMS-275291 given at a dose of 600 mg twice daily induced unacceptable toxicity. The better-tolerated schedule of 1200 mg once a day demonstrated inadequate efficacy in patients with human immunodeficiency virus-associated KS. The apoptosis assay was not helpful in predicting response.

Molecularly targeted therapies in adult soft tissue sarcomas: present approach and future directions

BACKGROUND

Sarcomas are rare neoplasms. Given the overwhelming chemotherapy resistance of the disease, patients with progressive and metastatic soft tissue sarcomas are ideal candidates for trials of investigational new drugs.

OBJECTIVE

The authors review the molecular mechanisms underlying soft tissue sarcomas and discuss molecularly targeted therapies developed to improve the poor outcome of these uncommon tumors.

METHODS

A Medline and American Society of Clinical Oncology abstract search was conducted using the keyword 'soft tissue sarcoma'. Articles and abstracts were reviewed and eligible for inclusion if they used targeted therapies for the treatment of patients with soft tissue sarcomas.

RESULTS/CONCLUSION

Phase II clinical trials for patients with soft tissue sarcomas using novel targets and present recognized targets are ongoing and planned.

Anti-cancer therapies targeting the tumor stroma

For anti-tumor therapy different strategies have been employed, e.g., radiotherapy, chemotherapy, or immunotherapy. Notably, these approaches do not only address the tumor cells themselves, but also the tumor stroma cells, e.g., endothelial cells, fibroblasts, and macrophages. This is of advantage, since these cells actively contribute to the proliferative and invasive behavior of the tumor cells via secretion of growth factors, angiogenic factors, cytokines, and proteolytic enzymes. In addition, tumor stroma cells take part in immune evasion mechanisms of cancer. Thus, approaches targeting the tumor stroma attract increasing attention as anti-cancer therapy. Several molecules including growth factors (e.g., VEGF, CTGF), growth factor receptors (CD105, VEGFRs), adhesion molecules (alphavbeta3 integrin), and enzymes (CAIX, FAPalpha, MMPs, PSMA, uPA) are induced or upregulated in the tumor microenvironment which are otherwise characterized by a restricted expression pattern in differentiated tissues. Consequently, these molecules can be targeted by inhibitors as well as by active and passive immunotherapy to treat cancer. Here we discuss the results of these approaches tested in preclinical models and clinical trials.

Inhibition of smooth muscle cell proliferation by a chemically modified tetracycline

INTRODUCTION

Chemically modified tetracyclines (CMTs) are a group of nonantimicrobial derivatives of tetracycline, which exert antiproliferative and anticollagenolytic properties. The molecular mechanisms, however, are poorly understood.

MATERIALS AND METHODS

The effect of CMT-3 on cultured, subconfluent rat aortic smooth muscle cells (SMCs) was analyzed by [(3)H]-thymidine incorporation, counting cell numbers, and flow cytometry analysis.

RESULTS

CMT-3 inhibited the incorporation of [(3)H]-thymidine and reduced the cell number dose-dependently, with approximately 60% inhibition at the maximal CMT-3 concentration used (20 mumol/l). CMT-3 decreased the SMC proportion in S-phase and gradually increased the proportion at G2/M. Initially, the proportion of cells in G1-phase increased and then gradually decreased back to baseline as the CMT-3 concentration increased. CMT-3 treatment of confluent SMCs for 24 h did not induce apoptosis.

CONCLUSIONS

CMT-3 inhibited SMC proliferation by inducing cell cycle arrest at the G2/M restriction point. Nonetheless, CMT-3 did not induce SMC apoptosis.

Influence of the microenvironment on melanoma cell fate determination and phenotype

Tumor cells communicate bidirectionally with the surrounding microenvironment, sending and receiving topographical and molecular cues that direct diverse cellular phenomena, including differentiation, growth, and invasion. The microenvironment has long been acknowledged as a facilitator of melanoma progression, and recent studies have illuminated tumor-associated factors, including hypoxia and the extracellular matrix, as important mediators of melanocyte transformation and transdifferentiation. Although these findings portray the microenvironment as a perilous obstacle to the successful treatment of advanced melanomas, it is important to note that certain molecular milieus may be capitalized on as potential treatment modalities. Indeed, our group and others have elucidated the unique ability of embryonic microenvironments to normalize aggressive melanoma cells toward a more benign melanocytic phenotype. The microenvironment therefore presents a novel target for the treatment and ultimately the prevention of melanoma progression and metastasis.

Targeted therapy for Kaposi's sarcoma and Kaposi's sarcoma-associated herpesvirus

PURPOSE OF REVIEW

To summarize major recent findings on the biology of human herpesvirus-8, i.e. Kaposi's sarcoma-associated herpesvirus, and the implications of these findings for Kaposi's sarcoma treatment.

RECENT FINDINGS

Although reduced in incidence in developed countries since the introduction of highly active antiretroviral therapy, Kaposi's sarcoma incidence is still markedly increased in HIV-infected patients in resource-rich areas of the world and is a major complication among HIV-infected individuals in sub-Saharan Africa. The Akt/mammalian target of rapamycin pathway has emerged as a major driving force in Kaposi's sarcoma. In addition, the roles of p53, the Kaposi's sarcoma-associated herpesvirus viral cyclin and nuclear factor-kappaB in the development and progression of Kaposi's sarcoma are being further clarified, and therapeutic agents are being developed that may target these pathogenetic mechanisms. New Kaposi's sarcoma treatments should be considered that target the molecular interface between virus and host.

SUMMARY

The growing knowledge of Kaposi's sarcoma biology provides multiple opportunities for rational targeted therapies. Further research is needed to better understand the mechanisms by which Kaposi's sarcoma develops and to develop therapeutic strategies that prevent resistance to treatment.

Matrix metalloproteinase dysregulation in HIV infection: implications for therapeutic strategies

The emerging role of immune activation and inflammation in the pathogenesis of human immunodeficiency virus (HIV) disease has stimulated the search for new approaches for managing HIV infection. Recent evidence suggests that an imbalance between matrix metalloproteinases (MMPs) and endogenous tissue inhibitors of MMPs (TIMPs) might contribute to HIV-associated pathology by inducing remodelling of the extracellular matrix. Here, we discuss the evidence and the potential mechanisms for altered MMP or TIMP function in HIV infection and disease. Furthermore, we outline the possible medical implications for the use of compounds that target MMP activity, and we propose that antiretroviral drugs, particularly HIV protease inhibitors (PIs), and compounds with anti-inflammatory properties, such as statins, natural omega-3 fatty acids and tetracyclines, which inhibit MMP function, might represent useful therapeutic approaches to mitigate potential MMP-related damage during HIV infection.

HIV-associated Kaposi sarcoma: pathogenesis and therapy

While classical Kaposi sarcoma is a slowly progressing tumor, AIDS-related Kaposi sarcoma is much more aggressive. After introduction of antiretroviral therapy and with the use of well- tolerated chemotherapeutic agents, complete remission of the tumor can be achieved. Local therapeutic options include excision, cryosurgery, radiation and alitretinoin gel. In 45 % of patients with more than 400/microl CD4+ lymphocytes, interferon-alpha induces complete remission. New concepts of pathogenesis lead to therapeutic targets, such as inhibition of angiogenesis.

Fumagillin: an anti-infective as a parent molecule for novel angiogenesis inhibitors

Fumagillin is an active amebicide and anti-infective isolated from the fungus Aspergillus fumigatus. Since its characterization in 1951, fumagillin has been studied extensively for its anti-infective properties. Although fumagillin is not approved for systemic use in the USA, this compound has one of the highest efficacies for the treatment of microsporidial infections in HIV-positive patients. Fumagillin does exhibit some side effects that have deterred its acceptance as a viable treatment, but the current body of research on the synthesis of novel analogs of this molecule shows an exciting and promising revival of this drug as both an anti-infective and antiangiogenic agent.

AIDS-associated Kaposi's sarcoma: is there still a role for interferon alfa?

Interferon alfa (IFNalpha) was one of the first agents to be used therapeutically in AIDS-associated Kaposi's sarcoma (KS) more than 25 years ago, and induces tumor regression in a subset of patients. Although much has been learned about the clinical role of IFNalpha in KS treatment, little is currently known about the mechanism(s) by which IFNalpha causes KS regression. This is despite a growing understanding of both KS pathogenesis and relevant IFNalpha activities. To a large extent other agents have supplanted IFNalpha as treatments for KS, but there may still remain a therapeutic role for IFNalpha, possibly in combination with other agents targeting angiogenesis and/or HHV-8-encoded human gene homologs that encode proteins involved in cell cycle regulation and signaling.

Management of oral lesions in HIV-positive patients

HIV/AIDS is currently the leading cause of death in Africa and the fourth leading cause of death worldwide. This systematic review of the literature was conducted to evaluate the evidence for treatment of the most common oral lesions associated with HIV: oral candidiasis with or without oropharyngeal involvement (OPC), oral hairy leukoplakia (OHL), recurrent aphthous-like ulcerations (RAU), oral Kaposi's sarcoma (OKS), orolabial herpes simplex infection (HSV), oral herpes zoster infection (VZV), intraoral or perioral warts (HPV), and HIV-associated periodontal diseases. Treatment of HIV-associated salivary gland disease is addressed in a different section of this World Workshop. We found the largest body of evidence for treatment of OPC in HIV patients. Future trials will be needed to test drugs currently in development for treatment of Candida strains that are resistant to existing therapies. There were no double blind, placebo-controlled randomized clinical trials (RCT) for topical treatment of OHL, and only one RCT for systemic treatment of the lesion with desciclovir. Systemic thalidomide was the only drug tested in RCT for treatment or prevention of RAU. Only 1 double-blind RCT comparing vinblastine and sodium tetradecyl sulfate was identified for localized treatment of OKS. Three drugs (famciclovir, acyclovir, and valaciclovir) were shown to be effective in randomized, double-blind trials for treatment or suppression of mucocutaneous HSV lesions in HIV patients. In all 3 trials, the effects of these medications on orolabial HSV lesions were not reported separately. There were no double-blind, placebo-controlled RCT testing topical treatments for orolabial HSV lesions in HIV patients. No trials testing treatments of oral VZV were identified. There were no double-blind, placebo-controlled RCT for treatment of HIV-associated intraoral or perioral warts or periodontal diseases. In conclusion, there is a need for well-designed RCTs to assess the safety and efficacy of topical and systemic treatments of most oral mucosal and perioral lesions in HIV patients. There is also a need to develop newer drugs for treatment of resistant fungal and viral microorganisms. Finally, standardized outcome measures should be developed for future clinical trials to allow comparisons of studies using different populations.

Kaposi sarcoma as a model of oncogenesis and cancer treatment

Kaposi sarcoma is the most common cancer among HIV-infected individuals and one of the most common cancers in sub-Saharan Africa. Kaposi sarcoma lesions are highly vascularized, and comprised of spindle-shaped tumor cells. Kaposi sarcoma herpesvirus is etiologically linked to Kaposi sarcoma development and encodes genes that contribute to cellular transformation, evasion of apoptosis, aberrant angiogenesis and an inflammatory tumor microenvironment. The study of Kaposi sarcoma herpesvirus-driven malignancies has provided a model of oncogenesis and identified some of the key steps and, therefore, therapeutic targets of Kaposi sarcoma development. However, current Kaposi sarcoma treatments are not specific and rely on reconstitution of the immune system and systemic administration of cytotoxic agents. Recent studies have demonstrated that mechanism-based therapeutics, such as vascular endothelial growth factor A or mammalian target of rapamycin inhibitors, are promising therapeutic approaches bridging basic research with clinical practice.

Emerging drugs for the treatment of soft tissue sarcomas

Soft tissue sarcomas are rare cancers of mesenchymal origin. Recent progress in the understanding of the biology of these rare tumours has enabled the identification of distinct molecular and pathological entities within this heterogenous group of neoplasms, and has paved the way for the development of targeted therapeutics directed against activated kinases. One of the most clear examples is the identification of KIT and platelet-derived growth factor receptor-alpha kinase mutations in gastrointestinal stromal tumours, a subset of sarcomas arising from precursors of the interstitial cells of Cajal in the digestive tract, which led to the development of imatinib, sunitinib and other tyrosine kinase inhibitors for the treatment of solid tumours. This model has become the paradigm of a targeted treatment of solid tumours designed to inhibit the causal alteration in the oncogenesis of these tumours. This review summarises treatment strategies in the context of advanced disease and discusses new compounds being developed for patients with soft tissue sarcomas.

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.

Management of AIDS-related Kaposi's sarcoma

The advent of highly active antiretroviral therapy (HAART) has lead to a substantial reduction in the prevalence, morbidity, and mortality associated with AIDS-related Kaposi's sarcoma. Similarly, concomitant advances in chemotherapy and supportive-care protocols have allowed for Kaposi's sarcoma to be managed more effectively in comparison with the pre-HAART era. Furthermore, developments in our understanding of the pathogenesis of Kaposi's sarcoma have identified several molecular targets that can potentially provide new therapeutic strategies. This Review discusses the role of conventional chemotherapeutic and immunomodulatory agents in the treatment of Kaposi's sarcoma and summarises the current status and future prospects of novel molecularly targeted agents in the treatment of this disease.

A phase II and pharmacological study of the matrix metalloproteinase inhibitor (MMPI) COL-3 in patients with advanced soft tissue sarcomas

This phase II study evaluated the antitumor activity of the tetracycline analog COL-3, a potent inhibitor of metalloproteinases (MMPs), particularly MMP-2 and MMP-9, on a continuous oral schedule at a dose of 50 mg/m2 daily in patients with advanced and/or metastatic soft tissue sarcoma (STS). The principal endpoints were the rate of objective tumor regression and the proportion of patients who did not experience disease progression during the first 8 weeks of treatment. Other study objectives included an assessment of pharmacology of COL-3, time to progression (TTP), and overall survival. A Simon two-stage design with multinomial stopping rule was employed, with 15 patients enrolled during the first stage of the study. Although COL-3 was generally well-tolerated, there were no objective responses and 5(33%) patients experienced disease progression during the first 8 weeks of treatment, which exceeded the criteria established a priori with regard to pursuing further evaluations of COL-3 in STS. The median values for TTP and survival were 109 and 279 days, respectively. Based on these results, further studies of COL-3 on this administration schedule in patients with STS are not warranted.