Chemokines and Kaposi’s sarcoma

Modulation of gene expression in Kaposi’s sarcoma-associated herpesvirus-infected lymphoid and epithelial cells

Aim: To evaluate the gene expression changes that occur soon after the active infection of two susceptible cell types with human herpesvirus 8 (HHV-8). Materials & methods: The expression profile of 282 human genes involved in the inflammatory process was investigated in HHV-8 A1 or C3 subtype-infected and mock-infected human epithelial cells and lymphoid cells. Results: The HHV-8-induced transcriptional profiles in the epithelial and lymphoid cells were very different. A robust increase in the expression was found in genes belonging to different categories, especially the categories of inflammation response and signal transduction. Conclusion: These results indicate that during early infection, HHV-8 induces a variety of cell type-specific processes, thus providing infection signatures useful as potential targets for therapeutic intervention.

Disseminated Kaposi's sarcoma in patients with HIV infection correlates to high serum levels of IL-10

Human herpesvirus 8 (HHV-8) is the etiologic agent of all Kaposi's sarcoma (KS), the outcome of which is associated with immuno-dysregulation, resulting in the abnormal production of inflammatory cytokines and chemokines. We quantified by enzyme-linked immunosorbent assay serum levels of interleukin (IL)-10, IL-17, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α from patients with KS-AIDS, classic KS, and human immunodeficiency virus (HIV) without KS. A correlation between HHV-8 molecular detection and cytokine production was also performed. We observed that IL-10 production was higher in patients with KS-AIDS when compared to those with classic KS or HIV. However, no significant differences were seen for IFN-γ, TNF-α, or IL-17 production between studied groups. When patients with KS-AIDS were analyzed according to lesion topography, IL-10 levels were higher in patients with disseminated disease than those observed in patients with only cutaneous lesions or cutaneous and digestive and/or respiratory tract lesions. Finally, patients with KS-AIDS that presented viral DNA for HHV-8 in serum showed a higher production of IL-10 when compared with those patients with a negative result for nested polymerase chain reaction for the virus. The results presented here are the first to demonstrate that there exists a stratification of patients with KS-AIDS according to lesion topography where IL-10 levels are higher in those individuals with disseminated disease than those with only localized lesions.

ERK-dependent downregulation of the atypical chemokine receptor D6 drives tumor aggressiveness in Kaposi sarcoma

D6 is an atypical chemokine receptor acting as a decoy and scavenger for inflammatory CC chemokines expressed in lymphatic endothelial cells. Here, we report that D6 is expressed in Kaposi sarcoma (KS), a tumor ontogenetically related to the lymphatic endothelium. Both in human tumors and in an experimental model, D6 expression levels were inversely correlated with tumor aggressiveness and increased infiltration of proangiogenic macrophages. Inhibition of monocyte recruitment reduced the growth of tumors, while adoptive transfer of wild-type, but not CCR2(-/-) macrophages, increased the growth rate of D6-competent neoplasms. In the KS model with the B-Raf V600E-activating mutation, inhibition of B-Raf or the downstream ERK pathway induced D6 expression; in progressing human KS tumors, the activation of ERK correlates with reduced levels of D6 expression. These results indicate that activation of the K-Ras-B-Raf-ERK pathway during KS progression downregulates D6 expression, which unleashes chemokine-mediated macrophage recruitment and their acquisition of an M2-like phenotype supporting angiogenesis and tumor growth. Combined targeting of CCR2 and the ERK pathway should be considered as a therapeutic option for patients with KS.

Blockade of cannabinoid receptors reduces inflammation, leukocyte accumulation and neovascularization in a model of sponge-induced inflammatory angiogenesis

OBJECTIVE

Angiogenesis depends on a complex interaction between cellular networks and mediators. The endocannabinoid system and its receptors have been shown to play a role in models of inflammation. Here, we investigated whether blockade of cannabinoid receptors may interfere with inflammatory angiogenesis.

MATERIALS AND METHODS

Polyester-polyurethane sponges were implanted in C57Bl/6j mice. Animals received doses (3 and 10 mg/kg/daily, s.c.) of the cannabinoid receptor antagonists SR141716A (CB1) or SR144528 (CB2). Implants were collected at days 7 and 14 for cytokines, hemoglobin, myeloperoxidase, and N-acetylglucosaminidase measurements, as indices of inflammation, angiogenesis, neutrophil and macrophage accumulation, respectively. Histological and morphometric analysis were also performed.

RESULTS

Cannabinoid receptors expression in implants was detected from day 4 after implantation. Treatment with CB1 or CB2 receptor antagonists reduced cellular influx into sponges at days 7 and 14 after implantation, although CB1 receptor antagonist were more effective at blocking leukocyte accumulation. There was a reduction in TNF-α, VEGF, CXCL1/KC, CCL2/JE, and CCL3/MIP-1α levels, with increase in CCL5/RANTES. Both treatments reduced neovascularization. Dual blockade of cannabinoid receptors resulted in maximum inhibition of inflammatory angiogenesis.

CONCLUSIONS

Blockade of cannabinoid receptors reduced leukocyte accumulation, inflammation and neovascularization, suggesting an important role of endocannabinoids in sponge-induced inflammatory angiogenesis both via CB1 and CB2 receptors.

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.

Role of the chemokines CCL3/MIP-1 alpha and CCL5/RANTES in sponge-induced inflammatory angiogenesis in mice

OBJECTIVE

We examined the potential contribution of CCL3 and CCL5 to inflammatory angiogenesis in mice.

METHODS

Polyester-polyurethane sponges were implanted in mice and blood vessel counting and hemoglobin, myeloperoxidase and N-acetylglucosaminidase measurements used as indexes for vascularization, neutrophil and macrophage accumulation, respectively.

RESULTS

CCL3 and CCL5 were expressed throughout the observation period. Exogenous CCL3 enhanced angiogenesis in WT, but angiogenesis proceeded normally in CCL3(-/-) mice, suggesting that endogenous CCL3 is not critical for sponge-induced angiogenesis in mice. CCL5 expression was detected at day 1, but levels significantly increased thereafter. Exogenous CCL5 reduced angiogenesis in WT mice possible via CCR5 as CCL5 was without an effect in CCR5(-/-) mice. Treatment of WT with the CCR1/CCR5 antagonist, Met-RANTES, prevented neutrophil and macrophage accumulation, but enhanced sponge vascularization.

CONCLUSION

Thus, endogenous CCL3 appears not to play a role in driving sponge-induced inflammatory angiogenesis in mice. The effects of CCL5 were anti-angiogenic and appeared to be mediated via activation of CCR5.

Leukotriene A4 hydrolase expression in PEL cells is regulated at the transcriptional level and leads to increased leukotriene B4 production

Primary effusion lymphoma (PEL) is a herpesvirus-8-associated lymphoproliferative disease characterized by migration of tumor cells to serous body cavities. PEL cells originate from postgerminal center B cells and share a remarkable alteration in B cell transcription factor expression and/or activation with classical Hodgkin's disease cells. Comparative analysis of gene expression by cDNA microarray of BCBL-1 cells (PEL), L-428 (classical Hodgkin's disease), and BJAB cells revealed a subset of genes that were differentially expressed in BCBL-1 cells. Among these, four genes involved in cell migration and chemotaxis were strongly up-regulated in PEL cells: leukotriene A4 (LTA4) hydrolase (LTA4H), IL-16, thrombospondin-1 (TSP-1), and selectin-P ligand (PSGL-1). Up-regulation of LTA4H was investigated at the transcriptional level. Full-length LTA4H promoter exhibited 50% higher activity in BCBL-1 cells than in BJAB or L-428 cells. Deletion analysis of the LTA4H promoter revealed a positive cis-regulatory element active only in BCBL-1 cells in the promoter proximal region located between -76 and -40 bp. Formation of a specific DNA-protein complex in this region was confirmed by EMSA. Coculture of ionophore-stimulated primary neutrophils with BCBL-1 cells leads to an increased production of LTB4 compared with coculture with BJAB and L-428 cells as measured by enzyme immunoassay, demonstrating the functional significance of LTA4H up-regulation.