Interleukin 6 and AIDS-associated Kaposi's sarcoma: a nested case control study within the Multicenter AIDS Cohort Study

Human herpesvirus 8 induces polyfunctional B lymphocytes that drive Kaposi's sarcoma

Kaposi’s sarcoma (KS) is an unusual neoplasia wherein the tumor consists primarily of endothelial cells infected with human herpesvirus 8 (HHV-8; Kaposi’s sarcoma-associated herpesvirus) that are not fully transformed but are instead driven to excess proliferation by inflammatory and angiogenic factors. This oncogenic process has been postulated but unproven to depend on a paracrine effect of an abnormal excess of host cytokines and chemokines produced by HHV-8-infected B lymphocytes. Using newly developed measures for intracellular detection of lytic cycle proteins and expression of cytokines and chemokines, we show that HHV-8 targets a range of naive B cell, IgM memory B cell, and plasma cell-like populations for infection and induction of interleukin-6, tumor necrosis factor alpha, macrophage inhibitory protein 1α, macrophage inhibitory protein 1β, and interleukin-8 in vitro and in the blood of HHV-8/HIV-1-coinfected subjects with KS. These B cell lineage subsets that support HHV-8 infection are highly polyfunctional, producing combinations of 2 to 5 of these cytokines and chemokines, with greater numbers in the blood of subjects with KS than in those without KS. Our study provides a new paradigm of B cell polyfunctionality and supports a key role for B cell-derived cytokines and chemokines produced during HHV-8 infection in the development of KS.

Kaposi’s sarcoma (KS) is the most common cancer in HIV-1-infected persons and is caused by one of only 7 human cancer viruses, i.e., human herpesvirus 8 (HHV-8). It is unclear how this virus causes neoplastic transformation. Development and outgrowth of endothelial cell lesions characteristic of KS are hypothesized to be dependent on virus replication and multiple immune mediators produced by the KS cells and inflammatory cells, yet the roles of these viral and cell factors have not been defined. The present study advances our understanding of KS in that it supports a central role for HHV-8 infection of B cells inducing multiple cytokines and chemokines that can drive development of the cancer. Notably, HIV-1-infected individuals who developed KS had greater numbers of such HHV-8-infected, polyfunctional B cells across a range of B cell phenotypic lineages than did HHV-8-infected persons without KS. This intriguing production of polyfunctional immune mediators by B cells serves as a new paradigm for B cell function and classification.

Modulation of host gene expression by the K15 protein of Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) contains several open reading frames (ORFs) encoding proteins capable of initiating signal transduction pathways. Among them is the K15 ORF, which consists of eight exons encoding a protein with 12 predicted transmembrane domains and a cytoplasmic C terminus. When transiently expressed, the 8-exon K15 transcript gives rise to a protein with an apparent molecular mass of 45 kDa. K15 interacts with cellular proteins, TRAF (tumor necrosis factor receptor-associated factor) and Src kinases, and activates AP-1, NF-kappaB, and the mitogen-activated protein kinases (MAPKs) c-jun-N-terminal kinase and extracellular signal-regulated kinase. This signaling activity of K15 is related to phosphorylation of Y(481) of the K15 SH2-B motif Y(481)EEV. In this study we demonstrate the expression of an endogenous 45-kDa K15 protein in KSHV BAC36-infected epithelial cells. This endogenous K15 protein shows the same intracellular localization as transiently expressed K15, and expression kinetic studies suggest it to be a lytic gene. We have further determined the downstream target genes of K15 signaling using DNA oligonucleotide microarrays. We demonstrate that K15 is capable of inducing expression of multiple cytokines and chemokines, including interleukin-8 (IL-8), IL-6, CCL20, CCL2, CXCL3, and IL-1alpha/beta, as well as expression of Dscr1 and Cox-2. In epithelial cells, K15-induced upregulation of most genes was dependent on phosphorylation of Y(481), whereas in endothelial cells mutation of Y(481) did not result in a complete loss of Dscr1 and Cox-2 expression and NFAT-activity. Our study establishes K15 as one of the KSHV lytic genes that are inducing expression of multiple cytokines, which have been shown to play an important role in KSHV-associated pathogenesis.

Therapy of AIDS-associated Kaposi's sarcoma: targeting pathogenetic mechanisms

Only a small number of the many agents with the potential to inhibit factors known to stimulate KS growth have been tested clinically, and many were investigated at a time when treatment options for HIV infection were relatively ineffective. The failure of some of these agents to induce KS regression may not signify failure to achieve a relevant biologic effect in all cases, but may simply mean that in a neoplasm that expresses a broad array of growth factors, inhibition of a single factor may be insufficient to achieve tumor regression. Moreover, agents that inhibit angiogenesis may be expected to stabilize tumors rather then eradicate them, but tumor stabilization is a difficult endpoint to quantify. In fact, given the redundancy of growth factors believed to be involved in KS development, it is perhaps remarkable that members of several classes of agents (eg, a synthetic retinoid, an MMPI, thalidomide, IL-12) have induced KS regression in a substantial minority of patients. It is likely, however, that drug combinations that target several pathogenetic mechanisms will be more effective than will single drugs in suppressing KS growth. A particular need. especially in the early evaluation of therapies aimed at specific pathogenic targets, is the development of assays to measure specific biologic effects (eg, changes in the activity of signal transduction pathways within tumor biopsy specimens) related to the agent's putative mechanism of action. Greater availability and clinical application of these types of markers of biologic efficacy may speed the identification of potentially active agents that could then be "fast tracked" into larger efficacy trials and combination studies.

Activation of cellular and heterologous promoters by the human herpesvirus 8 replication and transcription activator

The key regulator of the switch from latent to lytic replication of the human herpesvirus 8 (HHV-8; KSHV) is the replication and transcription activator (Rta). The ability of Rta to regulate cellular gene expression was examined by transient transfection into cells that were not infected with HHV-8. Rta induced some, but not all, NF-kappa B-responsive reporters through mechanisms that did not involve activation of classic forms of NF-kappa B. Furthermore, transfection of the NF-kappa B subunit Rel A inhibited the ability of Rta to transactivate some but not all reporters. For example, Rel A inhibited the ability of Rta to transactivate the IL-6 promoter, but only when sequences upstream of the NF-kappa B site were present. The ability of Rel A to inhibit Rta-mediated transactivation was not dependent on a functional NF-kappa B site within the promoter, suggesting an indirect mechanism for inhibition. These studies suggest that Rta expression during lytic reactivation of HHV-8 would lead to expression of some cellular genes, including IL-6, whereas activation of NF-kappa B could inhibit some responses to Rta.

Antitumor activity of oral 9-cis-retinoic acid in HIV-associated Kaposi's sarcoma

OBJECTIVE

To assess the efficacy, safety and tolerance of oral 9-cis-retinoic acid in HIV-infected patients with Kaposi's sarcoma.

METHODS

Sixty-six patients with AIDS-related Kaposi's sarcoma were enrolled at 14 centers; 60 received the study medication and were analyzed and, of these, 45 (75%) had received prior therapy for Kaposi's sarcoma. Once daily oral 9-cis-retinoic acid (alitretinoin, Panretin) was administered at doses up to 140 mg/m2. Most patients (72%) received a maximum dose of 100 mg/m2. Response was assessed using AIDS Clinical Trials Group (ACTG) criteria.

RESULTS

The median age was 38 years and the median absolute CD4 cell count was 194 x 10(6) cells/l (range 6-784 x 10(6)). Despite the use of three- and four-drug antiviral regimens (83%), the median HIV RNA at baseline was 8701 copies/ml [range < 500 (lower limit of detection) to 4.24 x 10(6)]. The tumor response rate was 37% (95% confidence interval 25-49). Tumor response was associated with improved quality-of-life measures. There was a significant increase in interleukin 6 (IL-6) levels from baseline to week 4. Responders had significantly lower baseline soluble IL-6 receptor levels (P = 0.029) than non-responders. The median time to response was 9 weeks (mean, 13 weeks; range, 4-36). HIV RNA levels did not change significantly during therapy nor did they correlate with tumor responses. Study drug was discontinued by 28 patients for adverse events, which included headache (13) and skin toxicity (10).

CONCLUSION

Oral 9-cis-retinoic acid is an active antitumor drug for AIDS-related Kaposi's sarcoma. Treatment is associated with skin and constitutional toxicity and further studies are needed to improve its long-term tolerance.

An IL6 promoter polymorphism is associated with a lifetime risk of development of Kaposi sarcoma in men infected with human immunodeficiency virus

Kaposi sarcoma (KS) is an angioproliferative inflammatory condition that occurs commonly in patients infected with human immunodeficiency virus (HIV). Inflammatory cytokines and growth factors promote the development of KS. Because physiologically important cytokine polymorphisms modulate host inflammatory responses, we investigated the association between KS and common regulatory polymorphisms in 5 proinflammatory cytokine genes encoding interleukin (IL) IL-1α, IL-1β, tumor necrosis factor (TNF) α, TNF-β, and IL-6 and in the IL-1 receptor antagonist (IL1RN). We also examined the contribution of stromal-derived factor 1 and chemokine receptor 5 (Δ32) polymorphisms to KS development. The population consisted of 115 HIV-infected men with KS and 126 deceased HIV-infected men without KS. The only strong association was observed between an IL6promoter polymorphism (G-174C) and susceptibility to KS in HIV-infected men (P = .0035). Homozygotes for IL6 allele G, associated with increased IL6 production, were overrepresented among patients with KS (P = .0046), whereas allele C homozygotes were underrepresented (P = .0062). Substantial in vitro evidence indicates that IL-6 contributes to the pathogenesis of KS. Our results show thatIL6 promoter genotypes associated with altered gene expression are risk factors for development of KS. Identification of a genetic risk factor for development of KS has important clinical implications for prevention and therapy.

An IL6 promoter polymorphism is associated with a lifetime risk of development of Kaposi sarcoma in men infected with human immunodeficiency virus

Kaposi sarcoma (KS) is an angioproliferative inflammatory condition that occurs commonly in patients infected with human immunodeficiency virus (HIV). Inflammatory cytokines and growth factors promote the development of KS. Because physiologically important cytokine polymorphisms modulate host inflammatory responses, we investigated the association between KS and common regulatory polymorphisms in 5 proinflammatory cytokine genes encoding interleukin (IL) IL-1α, IL-1β, tumor necrosis factor (TNF) α, TNF-β, and IL-6 and in the IL-1 receptor antagonist (IL1RN). We also examined the contribution of stromal-derived factor 1 and chemokine receptor 5 (Δ32) polymorphisms to KS development. The population consisted of 115 HIV-infected men with KS and 126 deceased HIV-infected men without KS. The only strong association was observed between an IL6promoter polymorphism (G-174C) and susceptibility to KS in HIV-infected men (P = .0035). Homozygotes for IL6 allele G, associated with increased IL6 production, were overrepresented among patients with KS (P = .0046), whereas allele C homozygotes were underrepresented (P = .0062). Substantial in vitro evidence indicates that IL-6 contributes to the pathogenesis of KS. Our results show thatIL6 promoter genotypes associated with altered gene expression are risk factors for development of KS. Identification of a genetic risk factor for development of KS has important clinical implications for prevention and therapy.

Human herpesvirus 8-encoded interleukin 6 activates HIV-1 in the U1 monocytic cell line

OBJECTIVE

Human herpesvirus 8 (HHV-8) encodes a viral interleukin 6 (vIL-6) which is structurally and functionally similar to human interleukin 6 (hIL-6). Since hIL-6 has been shown to upregulate the expression of HIV-1, the objectives of this study were to examine the ability of vIL-6 to upregulate HIV-1, and to determine the interactions of this virokine (viral cytokine) with the components of the interleukin 6 (IL-6) receptor complex.

DESIGN AND METHODS

Recombinant HHV-8 vIL-6 (rvIL-6) was assayed for bioactivity in the IL-6-dependent cell line MH60.BSF2. HIV-1 p24 production by the U1 monocytic and ACH-2 T-cell lines, which are chronically infected with HIV-1, was used to assess the ability of vIL-6 to affect HIV-1 expression. hIL-6 and vIL-6 receptor utilization was determined by quantifying HIV-1 p24 production after neutralization of components of the IL-6 receptor complex, CD126'IL-6R' and CD130'gp130', on U1 cells with blocking antibodies.

RESULTS

HHV-8 rvIL-6 was seen to have IL-6-like bioactivity in MH60.BSF2 cells, and readily upregulated HIV-1 p24 production in U1 monocytic cells, but not in ACH-2 T cells. The vIL-6 appeared to utilize the IL-6-specific component of the IL-6 signaling complex, CD126'IL-6R', in U1 cells.

CONCLUSIONS

HHV-8 vIL-6 clearly has the potential to upregulate HIV-1 expression in monocytic cells, and therefore may play a role in AIDS pathogenesis in individuals infected with both viruses.

The development of AIDS-associated Burkitt's/small noncleaved cell lymphoma is preceded by elevated serum levels of interleukin 6

B cell hyperactivation accompanies HIV infection and is believed to contribute to the increased incidence of B cell lymphoma in persons with AIDS. To examine B cell activation which precedes the development of AIDS-associated lymphoma, we measured levels of two B cell stimulatory molecules, soluble CD23 (sCD23) and interleukin 6 (IL6), in the serum of HIV-infected individuals prior to the diagnosis of lymphoma. Serum sCD23 was elevated in those subjects who developed lymphoma, compared to AIDS, HIV+, and HIV- controls (P = 0.001). Serum IL6 was significantly elevated in subjects who developed Burkitt's/small noncleaved cell lymphoma (BL/SNC, P = 0.01), but not in those subjects who developed large cell, immunoblastic, or central nervous system lymphomas, compared to CD4-matched AIDS controls who did not have lymphoma. These results suggest that lymphomagenesis of the BL/SNC subtype of AIDS lymphoma reflects B cell hyperactivation of a different nature from that which precedes other subtypes of AIDS-associated B cell lymphoma.