Treatments of AIDS-related Kaposi's sarcoma

Pathologic Angiogenesis of Malignant Vascular Sarcomas: Implications for Treatment

Angiosarcoma, epithelioid hemangioendothelioma, and Kaposi sarcoma are classified according to the line of differentiation that these neoplastic cells most closely resemble: the endothelial cell. Although these malignant vascular sarcomas demonstrate immunohistochemical and ultrastructural features typical of this lineage, they vary dramatically in presentation and behavior, reflecting oncologic mechanisms unique to each. Antineoplastic therapies offer significant benefit, but because of the rarity of these cancers, novel therapies are slow to develop, and treatment options for these cancers remain limited. Antiangiogenic approaches that have shown benefit in other malignancies have not fully realized their promise in vascular tumors, suggesting that these tumors do not depend entirely on either angiogenic growth factors or on neighboring endothelia that are affected by these agents. Nonetheless, translational studies have begun to unravel these distinct pathologies, identifying novel translocation products, targets of oncogenic virulence factors, and genomic mutations that hijack angiogenic signaling and drive malignant growth. Concurrently, an elaborate and highly regulated model of angiogenesis and lymphangiogenesis involving vascular endothelial growth factor–receptor tyrosine kinase and TGF-β and Notch pathways has emerged that informs treatment of these tumors as well as cancer in general. This review summarizes the literature on malignant vascular sarcomas in the context of current models of angiogenesis and, in light of recent clinical trial data, could help clinician-scientists generate novel therapeutic approaches.

Case report of ocular Kaposi's sarcoma

Background

Kaposi’s sarcoma (KS) is generally considered a neoplastic disorder of vascular origin and occurs in patients with acquired immunodeficiency syndrome (AIDS) or who have received immunosuppressive treatments after an organ transplant (Soulier et al., Blood 86(4):1276–80, 1995; Viejo-Borbolla and Schulz, AIDS Rev 5(4):222–9, 2003; Schulz, J Antimicrob Chemother 45(Suppl T3):15–27, 2000; Aversa et al. Crit Rev Oncol Hematol 53(3):253–65, 2005; Mbulaiteye and Engels, Int J Cancer 119(11):2685–91, 2006; Tessari et al., Eur J Dermatol 16(5):553–7, 2006). Several Kaposi’s sarcoma case reports involving eyelids and conjunctiva have been published (Bavishi et al., Int J STD AIDS 23(3):221–2, 2012; Baumann et al., Ger J Ophthalmol 4(4):239–45, 1995).

Case presentation

we report a 13 years old asian male patient rare case of ocular KS that was initiated from the sclera and progressed into the cornea and conjunctiva without an human Immunodeificiency Virus (HIV) or HHV-8 infection after a peripheral blood stem cells transplantation. In this case, anti- vascular endothelial growth factor (VEGF) therapy was attempted to stop the advance of ocular lesions and failed. Eventually, the KS was cured by a limbo-corneal lamellar graft, an amniotic membrane and scleral allograft transplantation plus intraoperative mitomycin C(MMC) after the complete excision of the tumors.

Conclusion

A compete surgical excision combined with the intraoperative application of MMC, as well as grafts to repair the scleral, conjunctival, and corneal surfaces, could prevent a recurrence of KS.

Different Cell Cycle Modulation in SKOV-3 Ovarian Cancer Cell Line by Anti-HIV Drugs

Antiretroviral drugs used for the treatment of human immunodeficiency virus (HIV) have proven to be effective even against cancer. Drawing from this background, the aim of our research project was to evaluate the effects of anti-HIV drugs that belong to the nucleoside and nucleotide reverse transcriptase inhibitor [NRTI; abacavir (ABC) and tenofovir (TDF)], nonnucleoside reverse transcriptase inhibitor [NNRTI; efavirenz (EFV) and etravirine (ETR)], and protease inhibitor [PI; darunavir (DRV)] categories on ovarian adenocarcinoma cell line SKOV-3. Using FACS analysis, we observed that treatment with NRTIs and NNRTIs showed a block in the G₀/G₁ phase. In particular, ETR displayed a relevant block in the progression of the G₀/G₁ phase of the cell cycle compared with the other examined drugs, and it also induced differentiation of SKOV-3 cells. In contrast, FACS analysis demonstrated that ABC and the PI inhibitor DRV showed no effect on the proliferation of cancer cells. DAPI (4′,6-diamidino-2-phenylindole) staining demonstrated that cells treated with NNRTIs (EFV and ETR) presented more DNA damage compared with other treatments. Immunoblotting analysis demonstrated that TDF, EFV, and ETR were able to obtain a reduction in the expression of cyclin D1 and Rb hypophosphorylation, and an increase in p21 concentration. Finally, we observed that ETR also induced differentiation, as demonstrated by Western blot, with high levels of E-cadherin expression. Therefore, our study provides additional evidence supporting the in vitro cytotoxic effects of ETR and EFV. Furthermore, it promotes the hypothesis for their potential use as therapeutic agents in ovarian cancer.

CYR61 suppresses growth of human malignant melanoma

Cysteine-rich protein 61 (CCN1/CYR61) is an important marker of proliferation and metastasis in malignant melanoma, making it a potential target for melanoma treatment. In this study, we compared the expression of CRY61 in Chinese patients with malignant melanoma with its expression in patients with other skin tumors or with no skin pathological conditions. We examined the effects of anti-human CYR61 monoclonal antibody on proliferation and evaluated the changes in CYR61 expression and cell proliferation in response to treatment with either epirubicin or interferon (IFN)-α. CYR61 was expressed at lower levels in patients with malignant melanoma than in patients with other skin tumors or with no pathology. Following the treatment of B16 cells with epirubicin and IFN-α, CYR61 levels increased, cell growth was inhibited, and proliferating cell nuclear antigen expression decreased. Thus, CYR61 could become a therapeutic target for malignant melanoma patients with high CYR61 expression.

Head and neck sarcomas: clinical and histopathological presentation, treatment modalities, and outcomes

BACKGROUND

Sarcoma of the head and neck is a rare condition that poses significant challenges in management and often requires radical multimodality treatment.

OBJECTIVES

This study aimed to analyse current clinical presentation, evaluation, management dilemmas and oncological outcomes.

METHODS

Computer records and case notes were analysed, and 39 patients were identified. Variables were compared using Pearson's chi-square test and the log-rank test, while survival outcomes were calculated using the Kaplan-Meier method.

RESULTS

The histopathological diagnosis was Kaposi sarcoma in 20.5 per cent of cases, chondrosarcoma in 15.3 per cent and osteosarcoma in 10.2 per cent. A range of other sarcomas were diagnosed in the remaining patients. The site of disease was most commonly sinonasal, followed by the oral cavity and larynx.

CONCLUSION

Wide local excision with clear resection margins is essential to achieve local control and long-term survival. There is a need for cross-specialty collaboration in order to accrue the evidence which will be necessary to improve long-term outcomes.

[Kaposi sarcoma in bronchopulmonary localization revealing HIV infection]

La maladie de Kaposi (MK) associée au VIH, forme dite épidémique, a été décrite la 1ère fois en 1981 par Hymmes. C'est l'affection maligne la plus fréquente au cours du SIDA. La MK est à l'origine de 10% des atteintes pleuropulmonaires au cours de l'infection par le VIH et 40% des pneumopathies en cas de MK cutanéomuqueuse. Les localisations pulmonaires occupent la deuxième place des atteintes viscérales après la forme digestive. Le diagnostic repose sur des arguments épidémiologiques, cliniques, radiologiques, biologiques, endoscopiques et histologiques. Nous rapportons un cas de MK broncho-pulmonaire compliquant une infection VIH chez un patient présentant une maladie de Kaposi cutanée de découverte fortuite au cours de l'atteinte pulmonaire. Le diagnostic a été retenu après avoir éliminé les maladies opportunistes à tropisme pulmonaire. Le Kaposi pulmonaire constitue l'atteinte la plus grave de la MK-sida et la survie après le diagnostic est courte malgré les thérapeutiques agressives.

Functional analysis of Kaposi's sarcoma-associated herpesvirus vFLIP expression reveals a new mode of IRES-mediated translation

Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic virus, the etiological agent of Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL). One of the key viral proteins that contributes to tumorigenesis is vFLIP, a viral homolog of the FLICE inhibitory protein. This KSHV protein interacts with the NFκB pathway to trigger the expression of antiapoptotic and proinflammatory genes and ultimately leads to tumor formation. The expression of vFLIP is regulated at the translational level by an internal ribosomal entry site (IRES) element. However, the precise mechanism by which ribosomes are recruited internally and the exact location of the IRES has remained elusive. Here we show that a 252-nt fragment directly upstream of vFLIP, within a coding region, directs translation. We have established its RNA structure and demonstrate that IRES activity requires the presence of eIF4A and an intact eIF4G. Furthermore, and unusually for an IRES, eIF4E is part of the complex assembled onto the vFLIP IRES to direct translation. These molecular interactions define a new paradigm for IRES-mediated translation.

The Significance of Interferon-γ in HIV-1 Pathogenesis, Therapy, and Prophylaxis

Interferon-γ (IFNγ) plays various roles in the pathogenesis of HIV/AIDS. In an HIV-1 infected individual, the production of IFNγ is detected as early as the acute phase and continually detected throughout the course of infection. Initially produced to clear the primary infection, IFNγ together with other inflammatory cytokines are involved in establishing a chronic immune activation that exacerbates clinical diseases associated with AIDS. Unlike Type 1 IFNs, IFNγ has no direct antiviral activity against HIV-1 in primary cultures, as supported by the in vivo findings of IFNγ therapy in infected subjects. Results from both in vitro and ex vivo studies show that IFNγ can instead enhance HIV-1 replication and its associated diseases, and therapies aimed at decreasing its production are under consideration. On the other hand, IFNγ has been shown to enhance cytotoxic T lymphocytes and NK cell activities against HIV-1 infected cells. These activities are important in controlling HIV-1 replication in an individual and will most likely play a role in the prophylaxis of an effective vaccine against HIV-1. Additionally, IFNγ has been used in combination with HIV-1 vaccine to augment antiviral immunity. Technological advancements have focused on using IFNγ as a biological marker to analyze the type(s) of immunity generated by candidate HIV vaccines and the levels of immunity restored by anti-retroviral drug therapies or novel immunotherapies. Hence, in addition to its valuable ancillary role as a biological marker for the development of effective HIV-1 prophylactic and therapeutic strategies, IFNγ has a vital role in promoting the pathogenesis of HIV.

Kaposi sarcoma-associated herpes virus and response to antiretroviral therapy: a prospective study of HIV-infected adults

BACKGROUND

The possible impact of coinfection with the Kaposi sarcoma-associated herpes virus (KSHV) on the response to antiretroviral therapy (ART) is unknown. Prospective studies are rare, particularly in Africa.

METHODS

We enrolled a prospective cohort of HIV-infected adults initiating ART in Johannesburg, South Africa. The subjects were defined as seropositive to KSHV if they were reactive to either KSHV lytic K8.1 or latent Orf73 antigen or to both. The subjects were followed from ART initiation until 18 months of treatment. HIV viral load and CD4 counts were tested 6 monthly. Linear generalized estimating and log-binomial regression models were used to estimate the effect of KSHV infection on immunologic recovery and response and HIV viral load suppression within 18 months after ART initiation.

RESULTS

Three hundred eighty-five subjects initiating ART from November 2008 to March 2009 were considered to be eligible including 184 (48%) KSHV+. The KSHV+ group was similar to the KSHV- in terms of age, gender, initiating CD4 count, body mass index, tuberculosis, and hemoglobin levels. The KSHV+ group gained a similar number of cells at 6 [difference of 10 cells per cubic millimeter, 95% confidence interval (CI): -11 to 31], 12 (3 cells per cubic millimeter, 95% CI: -19 to 25), and 18 months (24 cells per cubic millimeter, 95% CI: -13 to 61) compared with that gained by the KSHV- group. Adjusted relative risk of failure to suppress viral load to <400 copies per milliliter (1.03; 95% CI: 0.90 to 1.17) were similar for KSHV+ and KSHV- by 6 months on treatment.

CONCLUSIONS

In a population with a high KSHV prevalence, HIV-positive adults coinfected with KSHV achieved similar immunologic and virologic responses to ART early after treatment initiation compared with those with KSHV-.

Role of radiotherapy in local control of non-AIDS associated Kaposi's sarcoma patients in Korea: a single institution experience

PURPOSE

There has been no definite consensus on standard treatment, either local or systemic, for the Kaposi's sarcoma (KS). Radiotherapy (RT) can be a good local therapeutic choice especially in non-AIDS associated KS (NAKS) for its indolent behavior.

MATERIALS AND METHODS

Medical records of 17 KS patients treated with RT at the Seoul National University Hospital from February 1998 to January 2012 were retrospectively reviewed. One human immunodeficiency virus (HIV)+ patient with 3 lesions was excluded. The total number of the lesion was 23 among the 16 patients. The median follow-up period was 27.9 months. Correlation between response and variables was analyzed using the logistic regression model. Median age of the patients was 75 years. All the 23 lesions were located at the extremities. Fourteen (61%) of those had pain or local swelling as the initial presentation. Ten patients had possible causes of immunodeficiency and were regarded as iatrogenic, and other 6 were classic KS. Median dose of RT was 36 Gy.

RESULTS

No KS-related death was observed. Excluding 2 with short-term follow-up only, complete response and partial response were obtained in 2 (9%) and 19 (73%) lesions, respectively. Of those, 3 lesions underwent local progression. Six had out-of-field recurrence after RT. Symptom improvement was achieved in 13 (93%) of 14 patients. Grade 2 skin toxicities were found in 9 lesions but all got improvement after treatment. When divided into responsive and progressive group, free from progression was not related to any of the possible variables.

CONCLUSION

RT is effective in local control of NAKS resulting great response rate.

Immunotherapy in nonmelanoma skin cancer

Nonmelanoma skin cancer is the most common type of cancer in humans. The role of the immune system in the prevention and regression of cancer is significant. UV radiation, being the most important risk factor in the development of skin cancer, has a suppressive effect on local and systemic immune effectors. Different immunotherapeutic approaches have been used for the treatment of nonmelanoma skin cancer including adoptive T-cell therapies, vaccine-based strategies, cytokines and monoclonal antibodies. The most important advancement with promising effects in the field of nonmelanoma skin cancer immunotherapy is the topical immune response modifier imiquimod. In addition, immunoprevention has been successfully applied for autosomal dominant basal cell nevus syndrome. Immunotherapeutic approaches provide a new modality for the treatment of recurrent or multiple nonmelanoma skin tumors.

Activation of PI3K/AKT and ERK MAPK signal pathways is required for the induction of lytic cycle replication of Kaposi's sarcoma-associated herpesvirus by herpes simplex virus type 1

Background

Kaposi's sarcoma-associated herpesvirus (KSHV) is causally linked to several acquired immunodeficiency syndrome-related malignancies, including Kaposi's sarcoma (KS), primary effusion lymphoma (PEL) and a subset of multicentric Castleman's disease. Regulation of viral lytic replication is critical to the initiation and progression of KS. Recently, we reported that herpes simplex virus type 1 (HSV-1) was an important cofactor that activated lytic cycle replication of KSHV. Here, we further investigated the possible signal pathways involved in HSV-1-induced reactivation of KSHV.

Results

By transfecting a series of dominant negative mutants and protein expressing constructs and using pharmacologic inhibitors, we found that either Janus kinase 1 (JAK1)/signal transducer and activator of transcription 3 (STAT3) or JAK1/STAT6 signaling failed to regulate HSV-1-induced KSHV replication. However, HSV-1 infection of BCBL-1 cells activated phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB, also called AKT) pathway and inactivated phosphatase and tensin homologue deleted on chromosome ten (PTEN) and glycogen synthase kinase-3β (GSK-3β). PTEN/PI3K/AKT/GSK-3β pathway was found to be involved in HSV-1-induced KSHV reactivation. Additionally, extracellular signal-regulated protein kinase (ERK) mitogen-activated protein kinase (MAPK) pathway also partially contributed to HSV-1-induced KSHV replication.

Conclusions

HSV-1 infection stimulated PI3K/AKT and ERK MAPK signaling pathways that in turn contributed to KSHV reactivation, which provided further insights into the molecular mechanism controlling KSHV lytic replication, particularly in the context of HSV-1 and KSHV co-infection.

The key residues of active sites on the catalytic fragment for paclitaxel interacting with poly (ADP-ribose) polymerase

Poly(ADP-ribose) polymerase (PARP) is regarded as a target protein for paclitaxel (PTX) to bind. An important issue is to identify the key residues as active sites for PTX interacting with PARP, which will help to understand the potential drug activity of PTX against cancer cells. Using docking method and MD simulation, we have constructed a refined structure of PTX docked on the catalytic function domain of PARP (PDB code: 1A26). The residues Glu327(988), Tyr246(907), Lys242(903), His165(826), Asp105(766), Gln102(763) and Gln98(759) in PARP are identified as potential sites involved in interaction with PTX according to binding energy (E(b)) between PTX and single residue calculated with B3LYP/6-31G(d,p). These residues form an active binding pocket located on the surface of the catalytic fragment, possibly interacting with the required groups of PTX leading to its activity against cancer cells. It is noted that most of the active sites make conatct with the "southern hemisphere" of PTX except for one residue, Tyr246(907), which interacts with the "northern hemisphere" of PTX. The conformation of PTX in complex with the catalytic fragment is observed as being T-shaped, similar to that complexed with β-tubulin. The total Eb of -269.9 kJ/mol represents the potent interaction between PTX and the catalytic fragment, implying that PTX can readily bind to the active pocket. The tight association of PTX with the catalytic fragment would inhibit PARP activation, suggesting a potential application of PTX as an effective antineoplastic agent.

Sulfated polymannuroguluronate inhibits Tat-induced SLK cell adhesion via a novel binding site, a KKR spatial triad

AIM

Sulfated polymannuroguluronate (SPMG), a candidate anti-AIDS drug, inhibited HIV replication and interfered with HIV entry into host T lymphocytes. SPMG has high binding affinity for the transactivating factor of the HIV-1 virus (Tat) via its basic domain. However, deletion or substitution of the basic domain affected, but did not completely eliminated Tat-SPMG interactions. Here, we sought to identify other SPMG binding sites in addition to the basic domain.

METHODS

The potential SPMG binding sites were determined using molecular simulation and a surface plasmon resonance (SPR) based competitive inhibition assay. The effect of SPMG on Tat induced adhesion was evaluated using a cell adhesion assay.

RESULTS

The KKR domain, a novel high-affinity heparin binding site, was identified, which consisted of a triad of Lys12, Lys41, and Arg78. The KKR domain, spatially enclosed SPMG binding site on Tat, functions as another binding domain for SPMG. Further functional evaluation demonstrated that SPMG inhibits Tat-mediated SLK cell adhesion by directly binding to the KKR region.

CONCLUSION

The KKR domain is a novel high-affinity binding domain for SPMG. Our findings provide important new insights into the molecular mechanisms of SPMG and a potential therapeutic intervention for Tat-induced cell adhesion.

Cost-effectiveness of serum cryptococcal antigen screening to prevent deaths among HIV-infected persons with a CD4+ cell count < or = 100 cells/microL who start HIV therapy in resource-limited settings

BACKGROUND

Cryptococcal meningitis (CM) remains a common AIDS-defining illness in Africa and Asia. Subclinical cryptococcal antigenemia is frequently unmasked with antiretroviral therapy (ART). We sought to define the cost-effectiveness of serum cryptococcal antigen (CRAG) screening to identify persons with subclinical cryptococcosis and the efficacy of preemptive fluconazole therapy.

METHODS

There were 609 ART-naive adults with AIDS who started ART in Kampala, Uganda, and who had a serum CRAG prospectively measured during 2004-2006. The number needed to test and treat with a positive CRAG was assessed for > or = 30-month outcomes.

RESULTS

In the overall cohort, 50 persons (8.2%) were serum CRAG positive when starting ART. Of 295 people with a CD4(+) cell count < or = 100 cells/microL and without prior CM, 26 (8.8%; 95% confidence interval [CI], 5.8%-12.6%) were CRAG positive, of whom 21 were promptly treated with fluconazole (200-400 mg) for 2-4 weeks. Clinical CM developed in 3 fluconazole-treated persons, and 30-month survival was 71% (95% CI, 48%-89%). In the 5 CRAG-positive persons with a CD4(+) cell count < or = 100 cells/microL treated with ART but not fluconazole, all died within 2 months of ART initiation. The number needed to test and treat with CRAG screening and fluconazole to prevent 1 CM case is 11.3 (95% CI, 7.9-17.1) at costs of $190 (95% CI, $132-$287). The number needed to test and treat to save 1 life is 15.9 (95% CI, 11.1-24.0) at costs of $266 (95% CI, $185-$402). The cost per disability-adjusted life year saved is $21 (95% CI, $15-$32).

CONCLUSIONS

Integrating CRAG screening into HIV care, specifically targeting people with severe immunosuppression (CD4(+) cell count < or = 100 cells/microL) should be implemented in treatment programs in resource-limited settings. ART alone is insufficient treatment for CRAG-positive persons.

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.

Weekly paclitaxel for advanced aggressive classic Kaposi sarcoma: experience in 17 cases

BACKGROUND

Paclitaxel has proved to be highly effective in the treatment of severe AIDS-related Kaposi sarcoma (KS), for which it is now considered as a second-line monotherapy. Taxanes were recently shown to be active also in classic, endemic and post-transplantation KS.

OBJECTIVES

To evaluate the clinical efficacy and tolerability of standardized paclitaxel treatment (100 mg weekly, intravenously) in a homogeneous group of 17 patients with advanced aggressive and refractory classic KS (cKS).

METHODS

Seventeen patients with aggressive refractory cKS (stage IIIBc-IVBcv) were treated with intravenous paclitaxel 100 mg weekly. The response to the therapy was evaluated after 12 weeks. A maintenance treatment every 2 weeks was introduced for most of the patients and a final evaluation was made.

RESULTS

A partial/complete response was achieved in 14 of 17 patients. Two patients had allergic reactions, for which treatment was discontinued. One patient had progression of disease despite initial improvement. Patients received a mean of 16.8 courses. The treatment was generally well tolerated. Mean time to recurrence was 4.5 months from the end of the therapy and 7.35 months from the 12th course. In four of 10 patients who relapsed at follow-up, the recurrence was mild and responsive to local treatment, while the other six relapsing patients repeated paclitaxel with good response in five of them.

CONCLUSIONS

This study shows that low-dose paclitaxel proved to be effective and well tolerated in patients with aggressive refractory cKS, controlling the aggressiveness of the disease. The treatment can be repeated with good response.

Molecular modeling approaches to study the binding mode on tubulin of microtubule destabilizing and stabilizing agents

Tubulin targeting agents constitute an important class of anticancer drugs. By acting either as microtubule stabilizers or destabilizers, they disrupt microtubule dynamics, thus inducing mitotic arrest and, ultimately, cell death by apoptosis. Three different binding sites, whose exact location on tubulin has been experimentally detected, have been identified so far for antimitotic compound targeting microtubules, namely the taxoid, the colchicine and the vinka alkaloid binding site. A number of ligand- and structure-based molecular modeling studies in this field has been reported over the years, aimed at elucidating the binding modes of both stabilizing and destabilizing agent, as well as the molecular features responsible for their efficacious interaction with tubulin. Such studies are described in this review, focusing on information provided by different modeling approaches on the structural determinants of antitubulin agents and the interactions with the binding pockets on tubulin emerged as fundamental for antitumor activity.To describe molecular modeling approaches applied to date to molecules known to bind microtubules, this paper has been divided into two main parts: microtubule destabilizing (Part 1) and stabilizing (Part 2) agents. The first part includes structure-based and ligand-based approaches to study molecules targeting colchicine (1.1) and vinca alkaloid (1.2) binding sites, respectively. In the second part, the studies performed on microtubule-stabilizing antimitotic agents (MSAA) are described. Starting from the first representative compound of this class, paclitaxel, molecular modeling studies (quantitative structure-activity relationships - QSAR - and structure-based approaches), performed on natural compounds acting with the same mechanism of action and temptative common pharmacophoric hypotheses for all of these compounds, are reported.

Role of the ubiquitin system and tumor viruses in AIDS-related cancer

Tumor viruses are linked to approximately 20% of human malignancies worldwide. This review focuses on examples of human oncogenic viruses that manipulate the ubiquitin system in a subset of viral malignancies; those associated with AIDS. The viruses include Kaposi's sarcoma herpesvirus, Epstein-Barr virus and human papilloma virus, which are causally linked to Kaposi's sarcoma, certain B-cell lymphomas and cervical cancer, respectively. We discuss the molecular mechanisms by which these viruses subvert the ubiquitin system and potential viral targets for anti-cancer therapy from the perspective of this system.

Publication history: Republished from Current BioData's Targeted Proteins database (TPdb; ).

Enhanced microtubule binding and tubulin assembly properties of conformationally constrained paclitaxel derivatives

Microtubule binding and tubulin assembly promotion by a series of conformationally restricted paclitaxel (PTX) derivatives was investigated. In these derivatives, the C-4 acetate of the taxane is tethered to the C-3' phenyl at ortho and meta positions with different length linkers. The apparent affinity of these derivatives for GMPCPP-stabilized microtubules was assessed by a competition assay, and their influence on microtubule polymerization was evaluated by measuring the critical concentration of GDP-tubulin in the presence of the respective molecule. In general, taxane derivatives with higher apparent affinity for microtubules induced tubulin assembly more efficiently. Among the derivatives, molecules with the shortest tether display the strongest affinity for microtubules. These derivatives exhibited enhanced microtubule stabilization properties and efficiently induced GDP-tubulin assembly into microtubules at low temperature of 12 degrees C and in the absence of Mg2+ ions in 0.1 M PIPES. Based on molecular dynamics simulations, we propose that the enhanced ability to assemble microtubules by these taxane derivatives is linked to their ability to effectively shape the conformation of the M-loop of tubulin for cross-protofilament interaction.

Human herpesvirus 8 presence and viral load are associated with the progression of AIDS-associated Kaposi's sarcoma

OBJECTIVE

We present the largest longitudinal study to date that examines the association between Kaposi's Sarcoma (KS) disease progression and the presence and viral load of human herpesvirus 8 (HHV-8).

METHODS

Ninety-six men were enrolled at HIV clinics in Atlanta, Georgia, who had KS (n = 47) or were without KS but seropositive for HHV-8. Visits occurred at 6-month intervals for 2 years at which the patient's KS status was evaluated and oral fluid and blood were collected for quantification of HHV-8 DNA and antibodies.

RESULTS

The presence of HHV-8 DNA in blood was more common (P < 0.001) and the viral load higher (P < 0.001) in men with KS in comparison with men without KS. Mean HHV-8 viral loads in blood and oral fluids were associated with disease status, being highest among patients with progressing KS, intermediate among patients with stable KS, and lowest among patients with regressing KS. Consistent with our previous report high antibody titers to HHV-8 orf 65 were inversely associated with HHV-8 shedding in oral fluid.

CONCLUSIONS

We observed a significant association between changes in KS disease severity and the presence and viral load of HHV-8. HHV-8 viral load in blood may provide useful information to clinicians for assessment of the risk of further disease progression in patients with KS.

Interferon-alpha promotes abnormal vasculogenesis in lupus: a potential pathway for premature atherosclerosis

Individuals with systemic lupus erythematosus (SLE) have a striking increase in premature atherosclerosis of unclear etiology. Accelerated endothelial cell apoptosis occurs in SLE and correlates with endothelial dysfunction. Endothelial progenitor cells (EPCs) and myelomonocytic circulating angiogenic cells (CACs) are crucial in blood vessel repair after vascular damage, and decreased levels or abnormal function of EPCs/CACs are established atherosclerosis risk factors. We investigated if vascular repair is impaired in SLE. We report that SLE patients display abnormal phenotype and function of EPCs/CACs. These abnormalities are characterized by significant decreases in the number of circulating EPCs (310 +/- 50 EPCs/mL of blood in SLE versus 639 +/- 102 in controls) and significant impairments in the capacity of EPCs/CACs to differentiate into mature ECs and synthesize adequate levels of the proangiogenic molecules vascular endothelial growth factor (VEGF) and hepatic growth factor (HGF). These abnormalities are triggered by interferon-alpha (IFN-alpha), which induces EPC and CAC apoptosis and skews myeloid cells toward nonangiogenic phenotypes. Lupus EPCs/CACs have increased IFN-alpha expression and their supernatants promote higher induction of IFN-inducible genes. Importantly, neutralization of IFN pathways restores a normal EPC/CAC phenotype in lupus. SLE is characterized by an imbalance between endothelial cell damage and repair triggered by type I IFNs, which might promote accelerated atherosclerosis.

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.

Oncologic Complications of Human Immunodeficiency Virus Infection: Changing Epidemiology, Treatments, and Special Considerations in the Era of Highly Active Antiretroviral Therapy

Although highly active antiretroviral therapy (HAART) has revolutionized the treatment of human immunodeficiency virus (HIV)-positive patients, malignancies in the setting of HIV infection remain an appreciable problem. We evaluated the changing epidemiology of HIV-related malignancies, optimal neoplastics and their effect on viral dynamics, and evidence regarding drug interactions between chemotherapy and antiretrovirals. A MEDLINE search (January 1966-June 2006) was performed to identify clinical trials, review articles, and meta-analyses; abstracts from HIV conferences were also searched. Survival of patients with HIV-related malignancies has substantially improved since the advent of HAART. Chemotherapy for malignancies in the HIV-positive population generally resembles that for the HIV-negative population, with trials revealing an elevated frequency of toxicities in HIV-positive patients. Studies of antineoplastics have shown no long-term adverse effects on viral dynamics in terms of immunologic or virologic HIV markers. Limited pharmacokinetic data with antineoplastics and antiretrovirals suggest possible changes in some pharmacokinetic parameters, but these results should be interpreted cautiously because of the small numbers of patients enrolled in the trials. Researchers also report an increased frequency of chemotherapy-related toxicities when HAART was coadministered with antineoplastics. This increase was likely due to impairment of cytochrome P450 metabolism of antineoplastics by protease inhibitors. Because of the survival benefits of HAART, the integration of antiretrovirals with chemotherapy is now preferred for patients with HIV-related malignancies. However, because the metabolic pathways of many of these agents are similar, the effectiveness of antineoplastic therapy and its related toxicities should be vigilantly monitored in this patient population.

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.

The three-dimensional microvascular architecture of the human Kaposi sarcoma implanted in nude mice: a SEM corrosion casting study

The human Kaposi sarcoma represents one of the most common skin lesions associated with AIDS. Its clinical presentation and anatomopathological structure seem to demonstrate a particularly rich vascularity. The latest therapies aim to limit its intrinsic angiogenic activity in an attempt to reduce vascular density and the formation of new vessels. For these reasons, we decided to study the microvascular architecture of Kaposi sarcoma in three dimensions. We used a corrosion casting technique applied to nude mice previously transplanted subcutaneously with human modified neoplastic Kaposi sarcoma cells. The cooption of host vessels made by the tumor was demonstrated by three-dimensional scanning electron microscopy (SEM) images. At high magnification several angiogenic patterns were observed in the form of potato-shaped vessels, sprouts, intussusceptions and mouse tailed end tipped capillaries along with some ultrastructural features such as intercellular extravasations and endothelial cell modifications. Our investigation allowed us to build a detailed map of tumor vasculature in human Kaposi sarcoma. Furthermore, this study want to shed light on the sharp morphological three-dimensional conformation of angiogenic sprouts so to be able to better understand their modifications occurred during time and after antiangiogenic experimental therapies, by now observed only by immunohistochemical or immunofluorescent assays.

Evaluation of Antitumoral Properties of the Protease Inhibitor Indinavir in a Murine Model of Hepatocarcinoma

PURPOSE

Accumulating evidences show a higher incidence of hepatic neoplasm in HIV/hepatitis C virus (HCV)-coinfected individuals compared with HCV-monoinfected patients. Treatment with HIV-1 protease inhibitors inhibited cancer-promoted angiogenesis in HIV-infected patients affected by Kaposi sarcoma. We aimed to evaluate the antineoplastic potential activities of the protease inhibitor indinavir (Crixivan) in in vitro and in vivo hepatocarcinoma models.

EXPERIMENTAL DESIGN

We analyzed effects of indinavir on cell growth and invasiveness in Huh7 and SK-HEP-1 hepatocarcinoma cell lines and on in vivo tumor growth of the same cells in nude mice. Morphologic and molecular analyses on explanted tumors were carried out to evaluate vascularization and apoptosis.

RESULTS

We observed a reduced ability to invade an in vitro extracellular matrix for both cell lines treated with indinavir compared with controls (P = 0,001). Moreover, indinavir treatment was able to inhibit matrix metalloproteinase-2 proteolytic activation, whereas there was no effect on cell proliferation. The drug was also able to delay in vivo tumor growth. The inhibition of tumor growth was statistically significant from days 6 to 21 (P = 0.004 and P = 0.003, respectively). Moreover, the drug showed antiangiogenic and proapoptotic actions, as revealed by vessel count and apoptotic index by terminal deoxynucleotide transferase-mediated nick end labeling in explanted tumors. Finally, treatment with indinavir did not block the production of vascular endothelial growth factor in the tumors.

CONCLUSION

Indinavir could be helpful to prevent the development of hepatocarcinomas in HIV/HCV-coinfected individuals. In view of the current trend to substitute protease inhibitors with other antiretroviral agents, this information may have clinical implications.

AIDS-related malignancies: changing epidemiology and the impact of highly active antiretroviral therapy

PURPOSE OF REVIEW

Three cancers in people with HIV denote an AIDS diagnosis: Kaposi's sarcoma, high-grade B-cell non-Hodgkin's lymphoma and invasive cervical cancer. In addition a number of other cancers occur at increased frequency in this population group but are not AIDS-defining illnesses. This review discusses the impact of highly active antiretroviral therapy on the epidemiology and outcome of AIDS-defining cancers.

RECENT FINDINGS

The incidence of both Kaposi's sarcoma and non-Hodgkin's lymphoma has declined in the era of highly active antiretroviral therapy and the outcome of both tumours has improved. Moreover, highly active antiretroviral therapy alone produces a response in a majority of antiretroviral-naïve patients with Kaposi's sarcoma. In contrast, highly active antiretroviral therapy has had little impact on the incidence of human papilloma virus-associated tumours (cervical and anal cancer) in people with HIV, although it may improve survival by reducing opportunistic infection deaths. As people with HIV live longer with highly active antiretroviral therapy, an increased incidence of other non AIDS-defining cancers that have no known association with oncogenic infections is becoming apparent.

SUMMARY

For those with access to highly active antiretroviral therapy, the good news from the AIDS-defining cancers - particularly Kaposi's sarcoma and non-Hodgkin's lymphoma - may be balanced by the increasing numbers of non AIDS-defining cancers.