In Situ Study of Chemokine and Chemokine-Receptor Expression in Kaposi Sarcoma

Unveiling the role of KSHV-infected human mesenchymal stem cells in Kaposi's sarcoma initiation

Kaposi's sarcoma (KS) may derive from Kaposi's sarcoma herpesvirus (KSHV)-infected human mesenchymal stem cells (hMSCs) that migrate to sites characterized by inflammation and angiogenesis, promoting the initiation of KS. By analyzing the RNA sequences of KSHV-infected primary hMSCs, we have identified specific cell subpopulations, mechanisms, and conditions involved in the initial stages of KSHV-induced transformation and reprogramming of hMSCs into KS progenitor cells. Under proangiogenic environmental conditions, KSHV can reprogram hMSCs to exhibit gene expression profiles more similar to KS tumors, activating cell cycle progression, cytokine signaling pathways, endothelial differentiation, and upregulating KSHV oncogenes indicating the involvement of KSHV infection in inducing the mesenchymal-to-endothelial (MEndT) transition of hMSCs. This finding underscores the significance of this condition in facilitating KSHV-induced proliferation and reprogramming of hMSCs towards MEndT and closer to KS gene expression profiles, providing further evidence of these cell subpopulations as precursors of KS cells that thrive in a proangiogenic environment.

KSHV enhances mesenchymal stem cell homing and promotes KS-like pathogenesis

Kaposi's sarcoma (KS) tends to occur in injured or inflamed sites of the body, which is described as the "Koebner phenomenon". KS is also unique in its extraordinary angio-hyperplastic inflammatory phenotype. Recently, evidence has accrued indicating that KS may derive from KSHV-infected mesenchymal stem cells (MSCs), which possess enhanced migration and homing ability. Inspired by these findings, we hypothesized that KS may arise from KSHV-infected MSCs that chemotactically migrate to preexisting inflammatory or injured sites. Here we report that KSHV infection of human MSCs significantly up-regulated expression of several chemokine receptors and enhanced cell migration ability in vitro. Furthermore, using a wound mouse model, we demonstrated that KSHV infection dramatically promotes MSCs migrating and settling in the wound sites. In addition, two mice in the KSHV-infected group showed purpura and tumors with KS-like features. Taken together, KSHV-enhanced MSC migration ability and inflammatory microenvironment play crucial roles in KS development.

HIV-1 Evolutionary Patterns Associated with Metastatic Kaposi's Sarcoma during AIDS

Kaposi's sarcoma (KS) in HIV-infected individuals can have a wide range of clinical outcomes, from indolent skin tumors to a life-threatening visceral cancer. KS tumors contain endothelial-related cells and inflammatory cells that may be HIV-infected. In this study we tested if HIV evolutionary patterns distinguish KS tumor relatedness and progression. Multisite autopsies from participants who died from HIV-AIDS with KS prior to the availability of antiretroviral therapy were identified at the AIDS and Cancer Specimen Resource (ACSR). Two patients (KS1 and KS2) died predominantly from non-KS-associated disease and KS3 died due to aggressive and metastatic KS within one month of diagnosis. Skin and visceral tumor and nontumor autopsy tissues were obtained (n = 12). Single genome sequencing was used to amplify HIV RNA and DNA, which was present in all tumors. Independent HIV tumor clades in phylogenies differentiated KS1 and KS2 from KS3, whose sequences were interrelated by both phylogeny and selection. HIV compartmentalization was confirmed in KS1 and KS2 tumors; however, in KS3, no compartmentalization was observed among sampled tissues. While the sample size is small, the HIV evolutionary patterns observed in all patients suggest an interplay between tumor cells and HIV-infected cells which provides a selective advantage and could promote KS progression.

HIV tropism and decreased risk of breast cancer

Background

During the first two decades of the U.S. AIDS epidemic, and unlike some malignancies, breast cancer risk was significantly lower for women with human immunodeficiency virus (HIV) infection compared to the general population. This deficit in HIV-associated breast cancer could not be attributed to differences in survival, immune deficiency, childbearing or other breast cancer risk factors. HIV infects mononuclear immune cells by binding to the CD4 molecule and to CCR5 or CXCR4 chemokine coreceptors. Neoplastic breast cells commonly express CXCR4 but not CCR5. In vitro, binding HIV envelope protein to CXCR4 has been shown to induce apoptosis of neoplastic breast cells. Based on these observations, we hypothesized that breast cancer risk would be lower among women with CXCR4-tropic HIV infection.

Methods and Findings

We conducted a breast cancer nested case-control study among women who participated in the WIHS and HERS HIV cohort studies with longitudinally collected risk factor data and plasma. Cases were HIV-infected women (mean age 46 years) who had stored plasma collected within 24 months of breast cancer diagnosis and an HIV viral load ≥500 copies/mL. Three HIV-infected control women, without breast cancer, were matched to each case based on age and plasma collection date. CXCR4-tropism was determined by a phenotypic tropism assay. Odds ratios (OR) and 95% confidence intervals (CI) for breast cancer were estimated by exact conditional logistic regression. Two (9%) of 23 breast cancer cases had CXCR4-tropic HIV, compared to 19 (28%) of 69 matched controls. Breast cancer risk was significantly and independently reduced with CXCR4 tropism (adjusted odds ratio, 0.10, 95% CI 0.002–0.84) and with menopause (adjusted odds ratio, 0.08, 95% CI 0.001–0.83). Adjustment for CD4⁺ cell count, HIV viral load, and use of antiretroviral therapy did not attenuate the association between infection with CXCR4-tropic HIV and breast cancer.

Conclusions

Low breast cancer risk with HIV is specifically linked to CXCR4-using variants of HIV. These variants are thought to exclusively bind to and signal through a receptor that is commonly expressed on hyperplastic and neoplastic breast duct cells. Additional studies are needed to confirm these observations and to understand how CXCR4 might reduce breast cancer risk.

Induction of angiogenic chemokine CCL2 by human herpesvirus 8 chemokine receptor

Human herpesvirus 8 (HHV-8) is associated with Kaposi's sarcoma (KS), an endothelial cell lesion believed to be initiated and driven primarily by cytokine dysregulation. Among the viral proteins suspected as contributing to viral pathogenesis is the lytically expressed viral G protein-coupled receptor (vGPCR), which can induce various cellular cytokines. CC ligand-2 (CCL2/MCP-1) is a vGPCR-regulated angiogenic chemokine found at elevated levels in KS lesions and induced by HHV-8 infection of endothelial cells. Here we show that vGPCR induces CCL2 in endothelial cells via activation of C/EBPbeta and that vGPCR and C/EBPbeta are critical components of CCL2 induction by HHV-8 infection of endothelial cultures. To our knowledge, this is the first report of vGPCR-mediated cytokine induction, and its characterization, in the context of virus infection. Our results identify a mechanism by which vGPCR can contribute, in a host cell shutoff-independent manner, to viral pathogenesis.

Cytokine production by human herpesvirus 8-infected dendritic cells

We have shown previously that human herpesvirus 8 (HHV-8)-infected dendritic cells (DCs) undergo incomplete maturation and have a defective antigen-presenting function. Here, we examined the effects of HHV-8 infection on cytokine production, which is critical to the function of DCs. We detected expression of interleukin (IL)-6, tumour necrosis factor (TNF)-alpha, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, RANTES and IL-12p40 from 2 to 6 h post-infection, and these peaked by 15-24 h. Expression of these factors decreased 24-48 h post-infection, with the exception of TNF-alpha which remained high throughout the entire 72 h. Interestingly, while IL-12p40 expression increased post-infection, bioactive IL-12p70 was not detected in the supernatants. These results suggest an intentional skewing of cytokine production in HHV-8-infected DCs towards induction of a Th2 response.

AIDS malignancies

Among individuals with HIV-infection, coinfection with oncogenic viruses including EBV, HHV-8, and HPV cause significant cancer-related morbidity and mortality. It is clear that these viruses interact with HIV in unique ways that predispose HIV-infected individuals to malignant diseases. In general, treatment directed specifically against these viruses does not appear to change the natural history of the malignant disease, and once the malignancy develops, if their health permits, HIV-infected patients should be treated using similar treatment protocols to HIV-negative patients. However, for the less frequent HIV-related malignancies, such as PEL, or MCD, optimal treatments are still emerging. For certain AIDS-defining malignancies, it is clear that the widespread access to HAART has significantly decreased the incidence, and improved outcomes. However, for other cancers, such as the HPV-related tumors, the role of HAART is much less clear. Further research into prevention and treatment of these oncogenic virally mediated AIDS-related malignancies is necessary.

AIDS-related malignancies: emerging challenges in the era of highly active antiretroviral therapy

Human immunodeficiency virus (HIV)-infected patients are at increased risk of developing cancer, particularly in the later stages of acquired immune deficiency syndrome (AIDS). Despite the advent of highly active anti-retroviral therapy (HAART), malignancy in this population is a leading cause of morbidity and mortality. Kaposi's sarcoma (KS) and AIDS-related non-Hodgkin's lymphoma (ARL) are the most common AIDS-defining malignancies. AIDS-related KS varies from minimal to fulminant disease. Treatment decisions for AIDS-related KS are guided largely by the presence and extent of symptomatic disease. In addition to HAART, excellent treatments exist for both localized disease (topical gel, radiotherapy, and intralesional therapy) and advanced disease (liposomal anthracyclines, paclitaxel). Novel therapies that have become available to treat AIDS-related KS include angiogenesis inhibitors and antiviral agents. ARL comprises a heterogeneous group of malignancies. With the immune restoration afforded by HAART, standard-dose chemotherapies now can be safely administered to treat ARL with curative intent. The role of analogous treatments used in HIV-negative patients, including monoclonal antibodies and autologous stem cell transplantation, requires further clarification in HIV-positive patients. HIV-infected patients also appear to be at increased risk for developing certain non-AIDS-defining cancers, such as Hodgkin's lymphoma and multiple myeloma. Although the optimal treatment of these neoplasms is at present uncertain, recent advances in chemotherapy, antiretroviral drugs, and supportive care protocols are allowing for more aggressive management of many of the AIDS-related cancers. This article provides an up-to-date review of the epidemiology, pathogenesis, clinical features, and treatment of various AIDS-related malignancies that are likely to be encountered by an oncologist practicing in the current HAART era.

Advances in the pathobiology and treatment of Kaposi sarcoma

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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