Matrix metalloproteinases in the progression and regression of Kaposi's sarcoma

Kaposi Sarcoma, a Trifecta of Pathogenic Mechanisms

Kaposi's sarcoma is a rare disease with four known variants: classic, epidemic, endemic and iatrogenic (transplant-related), all caused by an oncogenic virus named Human Herpes Virus 8. The viral infection in itself, along with the oncogenic properties of HHV8 and with immune system dysfunction, forms the grounds on which Kaposi's Sarcoma may develop. Infection with HHV8 occurs through saliva via close contacts, blood, blood products, solid organ donation and, rarely, vertical transmission. Chronic inflammation and oncogenesis are promoted by a mix of viral genes that directly promote cell survival and transformation or interfere with the regular cell cycle and cell signaling (of particular note: LANA-1, v-IL6, vBCL-2, vIAP, vIRF3, vGPCR, gB, K1, K8.1, K15). The most common development sites for Kaposi's sarcoma are the skin, mucocutaneous zones, lymph nodes and visceral organs, but it can also rarely appear in the musculoskeletal system, urinary system, endocrine organs, heart or eye. Histopathologically, spindle cell proliferation with slit-like vascular spaces, plasma cell and lymphocyte infiltrate are characteristic. The clinical presentation is heterogenic depending on the variant; some patients have indolent disease and others have aggressive disease. The treatment options include highly active antiretroviral therapy, surgery, radiation therapy, chemotherapy, and immunotherapy. A literature search was carried out using the MEDLINE/PubMed, SCOPUS and Google Scholar databases with a combination of keywords with the aim to provide critical, concise, and comprehensive insights into advances in the pathogenic mechanism of Kaposi's sarcoma.

Human Immunodeficiency Virus (HIV) Infection and Use of Illicit Substances Promote Secretion of Semen Exosomes that Enhance Monocyte Adhesion and Induce Actin Reorganization and Chemotactic Migration

Semen exosomes (SE) from HIV-uninfected (HIV−) individuals potently inhibit HIV infection in vitro. However, morphological changes in target cells in response to SE have not been characterized or have the effect of HIV infection or the use of illicit substances, specifically psychostimulants, on the function of SE been elucidated. The objective of this study was to evaluate the effect of HIV infection, psychostimulant use, and both together on SE-mediated regulation of monocyte function. SE were isolated from semen of HIV− and HIV-infected (HIV+) antiretroviral therapy (ART)-naive participants who reported either using or not using psychostimulants. The SE samples were thus designated as HIV−Drug−, HIV−Drug+, HIV+Drug−, and HIV+Drug+. U937 monocytes were treated with different SEs and analyzed for changes in transcriptome, morphometrics, actin reorganization, adhesion, and chemotaxis. HIV infection and/or use of psychostimulants had minimal effects on the physical characteristics of SE. However, different SEs had diverse effects on the messenger RNA signature of monocytes and rapidly induced monocyte adhesion and spreading. SE from HIV infected or psychostimulants users but not HIV−Drug− SE, stimulated actin reorganization, leading to the formation of filopodia-like structures and membrane ruffles containing F-actin and vinculin that in some cases were colocalized. All SE stimulated monocyte chemotaxis to HIV secretome and activated the secretion of matrix metalloproteinases, a phenotype exacerbated by HIV infection and psychostimulant use. SE-directed regulation of cellular morphometrics and chemotaxis depended on the donor clinical status because HIV infection and psychostimulant use altered SE function. Although our inclusion criteria specified the use of cocaine, humans are poly-drug and alcohol users and our study participants used psychostimulants, marijuana, opiates, and alcohol. Thus, it is possible that the effects observed in this study may be due to one of these other substances or due to an interaction between different substances.

Increased phosphorylation of eIF2α in chronic myeloid leukemia cells stimulates secretion of matrix modifying enzymes

Recent studies underscore the role of the microenvironment in therapy resistance of chronic myeloid leukemia (CML) cells and leukemia progression. We previously showed that sustained mild activation of endoplasmic reticulum (ER) stress in CML cells supports their survival and resistance to chemotherapy. We now demonstrate, using dominant negative non-phosphorylable mutant of eukaryotic initiation factor 2 α subunit (eIF2α), that phosphorylation of eIF2α (eIF2α-P), which is a hallmark of ER stress in CML cells, substantially enhances their invasive potential and modifies their ability to secrete extracellular components, including the matrix-modifying enzymes cathepsins and matrix metalloproteinases. These changes are dependent on the induction of activating transcription factor-4 (ATF4) and facilitate extracellular matrix degradation by CML cells. Conditioned media from CML cells with constitutive activation of the eIF2α-P/ATF4 pathway induces invasiveness of bone marrow stromal fibroblasts, suggesting that eIF2α-P may be important for extracellular matrix remodeling and thus leukemia cells-stroma interactions. Our data show that activation of stress response in CML cells may contribute to the disruption of bone marrow niche components by cancer cells and in this way support CML progression.

A viral microRNA downregulates metastasis suppressor CD82 and induces cell invasion and angiogenesis by activating the c-Met signaling

Kaposi’s sarcoma (KS) is the most common AIDS-associated malignancy etiologically caused by Kaposi’s sarcoma-associated herpesvirus (KSHV). KS is a highly disseminated and vascularized tumor comprised of poorly differentiated spindle-shaped endothelial cells. KSHV encodes 12 pre-microRNAs (pre-miRNAs) that yield 25 mature miRNAs, but their roles in KSHV-induced tumor dissemination and angiogenesis remain largely unknown. KSHV-encoded miR-K12-6 (miR-K6) can produce two mature miRNAs, miR-K6-3p and miR-K6-5p. Recently, we have shown that miR-K6-3p promoted cell migration and angiogenesis by directly targeting SH3 domain binding glutamate-rich protein (SH3BGR) (PLoS Pathog. 2016;12(4):e1005605). Here, by using mass spectrometry, bioinformatics analysis and luciferase reporter assay, we showed that miR-K6-5p directly targeted the coding sequence (CDS) of CD82 molecule (CD82), a metastasis suppressor. Ectopic expression of miR-K6-5p specifically inhibited the expression of endogenous CD82 and strongly promoted endothelial cells invasion in vitro and angiogenesis in vivo. Overexpression of CD82 significantly inhibited cell invasion and angiogenesis induced by miR-K6-5p. Mechanistically, CD82 directly interacted with c-Met to inhibit its activation. MiR-K6-5p directly repressed CD82, relieving its inhibition on c-Met activation and inducing cell invasion and angiogenesis. Deletion of miR-K6 from KSHV genome abrogated KSHV suppression of CD82 resulting in compromised KSHV activation of c-Met pathway, and KSHV-induced invasion and angiogenesis. In conclusion, these results show that by inhibiting CD82, KSHV miR-K6-5p promotes cell invasion and angiogenesis by activating the c-Met pathway. Our findings illustrate that KSHV miRNAs may play an essential role in the dissemination and angiogenesis of KSHV-induced malignancies.

Kaposi's sarcoma-associated herpesvirus (KSHV)-encoded microRNAs promote matrix metalloproteinases (MMPs) expression and pro-angiogenic cytokine secretion in endothelial cells

The human oncogenic virus Kaposi's sarcoma-associated herpesvirus (KSHV) is linked to Kaposi's sarcoma (KS), a tumor of endothelial cells characterized by angiogenesis and invasiveness. KSHV genome encodes 25 mature microRNAs (miRNAs), but their roles in KSHV-induced tumor dissemination and angiogenesis are not fully understood. In this study, we constructed the sensor reporters of KSHV miRNAs and used a luciferase reporter assay to demonstrate the function of the mimics of KSHV miRNAs. Then, we examined the expression of matrix metalloproteinases (MMPs) and pro-angiogenic cytokines that are related to cell migration and angiogenesis in the KSHV 25 miRNAs transfected endothelial cells. We found that all KSHV miRNAs increased the expression of the transcripts of MMP1, MMP13, VEGFA, and VEGFR2 in different degrees, as well as the secretion of VEGFA protein in the supernatant of endothelial cells. Our results reveal that KSHV miRNAs contribute to regulating MMPs and expression of pro-angiogenic factors, thus, suggesting that these miRNAs might play a crucial role in KSHV-induced cell motility and angiogenesis.

The SH3BGR/STAT3 Pathway Regulates Cell Migration and Angiogenesis Induced by a Gammaherpesvirus MicroRNA

Kaposi’s sarcoma (KS)-associated herpesvirus (KSHV) is a gammaherpesvirus etiologically associated with KS, a highly disseminated angiogenic tumor of hyperproliferative spindle endothelial cells. KSHV encodes 25 mature microRNAs but their roles in KSHV-induced tumor dissemination and angiogenesis remain unknown. Here, we investigated KSHV-encoded miR-K12-6-3p (miR-K6-3p) promotion of endothelial cell migration and angiogenesis, which are the underlying mechanisms of tumor dissemination and angiogenesis. We found that ectopic expression of miR-K6-3p promoted endothelial cell migration and angiogenesis. Mass spectrometry, bioinformatics and luciferase reporter analyses revealed that miR-K6-3p directly targeted sequence in the 3’ untranslated region (UTR) of SH3 domain binding glutamate-rich protein (SH3BGR). Overexpression of SH3BGR reversed miR-K6-3p induction of cell migration and angiogenesis. Mechanistically, miR-K6-3p downregulated SH3BGR, hence relieved STAT3 from SH3BGR direct binding and inhibition, which was required for miR-K6-3p maximum activation of STAT3 and induction of cell migration and angiogenesis. Finally, deletion of miR-K6 from the KSHV genome abrogated its effect on the SH3BGR/STAT3 pathway, and KSHV-induced migration and angiogenesis. Our results illustrated that, by inhibiting SH3BGR, miR-K6-3p enhances cell migration and angiogenesis by activating the STAT3 pathway, and thus contributes to the dissemination and angiogenesis of KSHV-induced malignancies.

Kaposi’s Sarcoma (KS), caused by infection of Kaposi’s sarcoma (KS)-associated herpesvirus (KSHV), is a tumor of endothelial cells characterized by angiogenesis and invasiveness. In vitro, KSHV-infected endothelial cells display an increased invasiveness and angiogenicity. KSHV encodes twelve precursor miRNAs (pre-miRNAs), which are processed into at least 25 mature miRNAs. However, the roles of these miRNAs in KSHV-induced tumor dissemination and angiogenesis remain unknown. Here, we investigated KSHV-encoded miR-K12-6-3p (miR-K6-3p) promotion of endothelial cell migration and angiogenesis, which are the underlying mechanisms of tumor dissemination and angiogenesis. We demonstrated that miR-K6-3p promoted cell migration and angiogenesis by directly targeting SH3 domain binding glutamate-rich protein (SH3BGR). Furthermore, we found that STAT3, which was negatively regulated by SH3BGR mediated miR-K6-3p-induced cell migration and angiogenesis. MiR-K6-3p downregulation of SH3BGR, hence relieved SH3BGR direct inhibition of STAT3 resulting in the activation of STAT3 and induction of cell migration and angiogenesis. These results identify miR-K6-3p and its the downstream pathway as potential therapeutic targets for the treatment of KSHV-associated malignancies.

Isolated kaposi sarcoma of the tonsil: a case report and review of the scientific literature

Kaposi sarcoma is a tumour caused by human herpes virus 8, also known as Kaposi sarcoma-associated herpes virus. It usually affects the skin and oral mucosa; however, it can also sometimes affect the lungs, the liver, the stomach, the bowel, and lymph nodes. Several body sites may be affected simultaneously. The involvement of the tonsils is rare. We described an isolated localization of Kaposi's sarcoma of the right tonsil in a HIV-positive patient.

Manipulation of endothelial cells by KSHV: implications for angiogenesis and aberrant vascular differentiation

Kaposi sarcoma (KS), a viral cancer associated to Kaposi sarcoma herpesvirus (KSHV) infection, is currently the most common tumor in men in sub-Saharan Africa. KS is an angiogenic tumor and characterized by the presence of aberrant vascular structures in the lesion. Although our understanding of how KSHV causes the aberrant differentiation of endothelial cells and the typical vascular abnormalities in KS tumors is far from complete, the experimental evidence reviewed here provides a comprehensive description of the role of KSHV in the pathogenesis of this unusual tumor. In contrast to other tumor viruses, whose interference with cellular processes relating to cell cycle, apoptosis and DNA damage may be at the heart of their oncogenic properties, KSHV may cause KS primarily by its ability to engage with the differentiation and function of endothelial cells. Although the intracellular pathways engaged by KSHV in the endothelial cells are being explored as drug targets, a better understanding of the impact of KSHV on endothelial cell differentiation and vasculogenesis is needed before the encouraging findings can form the basis for new targeted therapeutic approaches to KS.

The inflammatory kinase MAP4K4 promotes reactivation of Kaposi's sarcoma herpesvirus and enhances the invasiveness of infected endothelial cells

Kaposi's sarcoma (KS) is a mesenchymal tumour, which is caused by Kaposi's sarcoma herpesvirus (KSHV) and develops under inflammatory conditions. KSHV-infected endothelial spindle cells, the neoplastic cells in KS, show increased invasiveness, attributed to the elevated expression of metalloproteinases (MMPs) and cyclooxygenase-2 (COX-2). The majority of these spindle cells harbour latent KSHV genomes, while a minority undergoes lytic reactivation with subsequent production of new virions and viral or cellular chemo- and cytokines, which may promote tumour invasion and dissemination. In order to better understand KSHV pathogenesis, we investigated cellular mechanisms underlying the lytic reactivation of KSHV. Using a combination of small molecule library screening and siRNA silencing we found a STE20 kinase family member, MAP4K4, to be involved in KSHV reactivation from latency and to contribute to the invasive phenotype of KSHV-infected endothelial cells by regulating COX-2, MMP-7, and MMP-13 expression. This kinase is also highly expressed in KS spindle cells in vivo. These findings suggest that MAP4K4, a known mediator of inflammation, is involved in KS aetiology by regulating KSHV lytic reactivation, expression of MMPs and COX-2, and, thereby modulating invasiveness of KSHV-infected endothelial cells.

Kaposi's sarcoma (KS) is a tumour caused by Kaposi's sarcoma herpesvirus (KSHV) and dysregulated inflammation. Both factors contribute to the high angiogenicity and invasiveness of KS. Various cellular kinases have been reported to regulate the KSHV latent-lytic switch and thereby virus pathogenicity. In this study, we have identified a STE20 kinase family member – MAP4K4 – as a modulator of KSHV lytic cycle and invasive phenotype of KSHV-infected endothelial cells. Moreover, we were able to link MAP4K4 to a known mediator of inflammation and invasiveness, cyclooxygenase-2, which also contributes to KSHV lytic replication. Finally, we could show that MAP4K4 is highly expressed in KS lesions, suggesting an important role for this kinase in tumour development and invasion.

Gene Expression Profiling Associated with the Progression of Classic Kaposi's Sarcoma

Although Kaposi's sarcoma (KS) gene expression profile is closer to lymphatic (LEC) rather than blood vascular endothelial cells (BEC), uncertainty still surrounds the cellular origin of KS. To follow KS progression from early to late (nodular) stage, and characterize the molecular fingerprinting associated with each stage, gene arrays were used to compare gene expression profile of 9 skin samples of classic KS (4 Early, 2 Mixed, and 3 Nodular CKS samples) to 4 normal samples. Results for selected genes were validated by Real-time (RT) PCR and immunohistochemistry. Genes regulating immune and defense responses, angiogenesis, apoptosis and proliferation were differentially expressed in different KS stages compared to normal skin. Hierarchical clustering separated normal skin from KS with a clear gradient from early to nodular KS lesions. The gene expression level of endothelium markers, metalloproteinases, angiogenic factors and chemokines, gradually increased from normal through all KS stages. The expression of LEC genes highly increased from early to nodular KS. In the initiation phase we noticed a higher expression of growth factors, as compared to progressive stages. LEC and BEC markers co-exist in “KS expression signature”, although the LEC signature prevailed. Our results also show a complex environment of inflammatory cells and chemokines during KS evolution. A pathogenic hypothesis where cellular hyperproliferation is driven by local expression of chemokines and growth factors without clonal expansion of cells is suggested.

Kaposi's sarcoma associated herpes virus (KSHV) induced COX-2: a key factor in latency, inflammation, angiogenesis, cell survival and invasion

Kaposi's sarcoma (KS), an enigmatic endothelial cell vascular neoplasm, is characterized by the proliferation of spindle shaped endothelial cells, inflammatory cytokines (ICs), growth factors (GFs) and angiogenic factors. KSHV is etiologically linked to KS and expresses its latent genes in KS lesion endothelial cells. Primary infection of human micro vascular endothelial cells (HMVEC-d) results in the establishment of latent infection and reprogramming of host genes, and cyclooxygenase-2 (COX-2) is one of the highly up-regulated genes. Our previous study suggested a role for COX-2 in the establishment and maintenance of KSHV latency. Here, we examined the role of COX-2 in the induction of ICs, GFs, angiogenesis and invasive events occurring during KSHV de novo infection of endothelial cells. A significant amount of COX-2 was detected in KS tissue sections. Telomerase-immortalized human umbilical vein endothelial cells supporting KSHV stable latency (TIVE-LTC) expressed elevated levels of functional COX-2 and microsomal PGE2 synthase (m-PGES), and secreted the predominant eicosanoid inflammatory metabolite PGE2. Infected HMVEC-d and TIVE-LTC cells secreted a variety of ICs, GFs, angiogenic factors and matrix metalloproteinases (MMPs), which were significantly abrogated by COX-2 inhibition either by chemical inhibitors or by siRNA. The ability of these factors to induce tube formation of uninfected endothelial cells was also inhibited. PGE2, secreted early during KSHV infection, profoundly increased the adhesion of uninfected endothelial cells to fibronectin by activating the small G protein Rac1. COX-2 inhibition considerably reduced KSHV latent ORF73 gene expression and survival of TIVE-LTC cells. Collectively, these studies underscore the pivotal role of KSHV induced COX-2/PGE2 in creating KS lesion like microenvironment during de novo infection. Since COX-2 plays multiple roles in KSHV latent gene expression, which themselves are powerful mediators of cytokine induction, anti-apoptosis, cell survival and viral genome maintainence, effective inhibition of COX-2 via well-characterized clinically approved COX-2 inhibitors could potentially be used in treatment to control latent KSHV infection and ameliorate KS.

Kaposi's sarcoma associated herpes virus (KSHV), with a 160 kb DNA genome, has evolved with two distinct life cycle phases, namely latency and lytic replication. KS, a complex angioproliferative disease, is regulated by a balance between pro-angiogenic and anti-angiogenic factors. In our previous study, we showed that KSHV modulates host factors COX-2/PGE2 for its own advantage to promote its latent (persistent) infection. The premise that COX-2 is involved in growth and progression of several types of solid cancers and inflammation associated diseases has been well documented but has never been studied in KS. Here, utilizing COX-2 inhibition strategies, including chemical inhibition and a gene silencing approach, we systematically identified the potential role of KSHV induced COX-2/PGE2 in viral pathogenesis related events such as secretion of inflammatory and angiogenic cytokines, MMPs and cell adhesion in de novo infected or latently infected endothelial cells. We report that COX-2/PGE2 inhibition down-regulates viral latent gene expression and survival of latently infected endothelial cells. The data emanating from our in vitro studies is valuable, informative and requires further examination using an in vitro angiogenic model and in vivo nude mice model to further validate COX-2 as a novel therapeutic to target latent infection and the associated diseases like KS.

Immunohistochemistry in Kaposi's sarcoma

The importance of immunohistochemistry (IHC) to our understanding, ability to confidently diagnose and treat Kaposi's sarcoma (KS) has grown steadily in the past few decades. IHC has been performed on many KS specimen types, with > 100 different primary antibodies. Therefore, it is not surprising that IHC has helped unravel the histogenesis, understand the pathogenesis and facilitate the diagnosis of KS and identify novel therapeutic targets in the disease. This paper reviews the literature on the use of IHC in the study of KS.

Histological variants of cutaneous Kaposi sarcoma

This review provides a comprehensive overview of the broad clinicopathologic spectrum of cutaneous Kaposi sarcoma (KS) lesions. Variants discussed include: usual KS lesions associated with disease progression (i.e. patch, plaque and nodular stage); morphologic subtypes alluded to in the older literature such as anaplastic and telangiectatic KS, as well as several lymphedematous variants; and numerous recently described variants including hyperkeratotic, keloidal, micronodular, pyogenic granuloma-like, ecchymotic, and intravascular KS. Involuting lesions as a result of treatment related regression are also presented.

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.

Differential expression of stromal MMP-1, MMP-9 and TIMP-1 in basal cell carcinomas of immunosuppressed patients and controls

Matrix metalloproteinases (MMPs) have an important role in the initiation, growth, and invasion of malignant tumors. Basal cell cancer (BCC) is the most common human malignancy. The risk of BCC is 10-16 times higher among organ transplant recipients compared with the nontransplanted population. The aim of this study was to compare the expression of several MMPs and their tissue inhibitors (TIMPs) in BCCs from kidney transplant recipients and controls. Expression of MMPs-1, -7, -8, -9, -10, -13, -26, and TIMPs-1 and -3 was evaluated by immunohistochemistry in 25 samples of BCC of kidney transplant recipients and 25 matched controls representing superficial and nodular subtypes. No significant differences were detected in MMP expression of BCC tumor cells between immunocompetent and immunodeficient patients. However, MMPs-1 and -9 and TIMP-1 were expressed more frequently in stromal macrophages in the BCCs of immunocompetent patients. When tumor subtypes were compared irrespective of the patient group, more MMP-1-positive fibroblasts and MMP-9-positive neutrophils were detected in the superficial subtype, while stromal MMP-10 expression was more abundant in nodular tumors. Our results suggest that abundant peritumoral expression of TIMP-1 in non-immunocompromised patients limits ECM degradation permissive for cancer cell migration.

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.