ZIA SC 010356 (ZIA) | |||
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Title | A Role for KSHV in the Pathogenesis of Malignancies | ||
Institution | NCI, Bethesda, MD | ||
Principal Investigator | Tosato, Giovanna | NCI Program Director | N/A |
Cancer Activity | N/A | Division | CCR |
Funded Amount | $247,753 | Project Dates | 01/01/1999 - 00/00/0000 |
Fiscal Year | 2015 | Project Type | Intramural |
Research Topics w/ Percent Relevance | Cancer Types w/ Percent Relevance | ||
Cancer (100.0%) |
Hodgkins disease (10.0%) Kaposi Sarcoma (40.0%) Leukemia (10.0%) Non Hodgkins Lymphoma (10.0%) Sarcoma (30.0%) |
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Research Type | |||
Cancer Progression & Metastasis Systemic Therapies - Discovery and Development |
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Abstract | |||
We have focused in four related areas: 1. the study of vFLIP, a KSHV latent gene product expressed in KSHV-infected cell targets and in Kaposi's sarcoma (KS), Primary Effusion Lymphoma (PEL) and Multicentric Castleman's disease (MCD); 2. the study of vIL-6, a KSHV viral product with structural similarity to cellular IL-6, and its role in the pathogenesis of MCD; 3. Peculiar clinical presentations of MCD; and 4. the development of new therapies for KSHV-induced malignancies occurring in AIDS patients. One of the characteristic features of KSHV is its ability to infect endothelial cells, and to indirectly promote angiogenesis and lymphangiogenesis predominantly by promoting the recruitment of cells that produce pro-angiogenic factors and promoting the expression of pro-angiogenic genes by the cells it infects. ORFK13/vFLIP encodes a 188-amino acid protein, which binds to the Ikb kinase (IKK) complex to activate NFkB. We examined ORFK13/vFLIP contribution to KS phenotype and potential for therapeutic targeting. To this end, we have retrovirally transduced ORFK13/vFLIP into primary human endothelial cells and examined the contribution of this gene to KS phenotype. We found that ORFK13/vFLIP induces the spindle morphology distinctive of KS cells and promotes formation of abnormal vascular networks typical of the disorderly KS vasculature. Microarray analysis of gene expression in endothelial cells transduced with ORFK13/vFLIP detected increased expression of certain pro-inflammatory cytokines, chemokines, and interferon-responsive genes. This study represents the first comprehensive analysis of gene regulation by KSHV-vFLIP. As one might expect from stimulation of pro-inflammatory cytokines and chemokines, we found that ORFK13/vFLIP stimulates adhesion of inflammatory cells characteristic of KS lesions. In additional experiments, we found that KSHV K13 induces the expression of the NF-kB regulatory proteins A20, ABIN-1 and ABIN-3 in primary human microvascular endothelial cells, and that KS spindle cells express A20 in KS tissue. In reporter assays, A20 strongly impaired K13-induced NF-kB activation in 293T cells, but ABIN-1 and ABIN-3 did not. Thus, these results provide evidence that KSHV finely modulates NF-kB in the host cells by both promoting NF-kB activation (resulting in expression of inflammatory cytokines) and tempering this activation by promoting expression of the NF-kB repressor A20 (resulting in inhibition of cell death). Previous studies from our group characterized vIL-6 as an early lytic gene expressed by KSHV, homologous to the cellular IL-6 cytokine. Unlike cellular IL-6, we found that vIL-6 can directly bind and signal through the gp130/JAK-STAT pathway without a requirement for the cellular IL-6 receptor, whose expression is restricted to certain cell types. Since gp130 is a fairly ubiquitous protein, vIL-6, in contract to the cellular cytokine can activate virtually all cells in the body. Previously, we have transduced vIL6 in NIH3T3 cells; when these cells were transferred to T-cell immunodeficient mice, they generated tumors at a significantly higher rate than control NIH3T3 cells and, importantly, the mice developed splenomegaly, hepatomegaly and plasmacytosis in many tissues. These features are common to patients with MCD. We have now produced transgenic mouse lines in which vIL-6 is ubiquitously expressed. These mice were found to exhibit vIL-6 serum levels comparable with those observed in KSHV-infected patients, to contain elevated amounts of phosphorylated STAT3 in spleen and lymph nodes, where vIL-6 was abundantly produced, and to spontaneously develop key features of human plasma cell-type MCD, including splenomegaly, multifocal lymphadenopathy, hypergammaglobulin-emia, and plasmacytosis. Interestingly, the vIL-6 transgenic mice crossed into IL-6-deficient mice did not yield the MCD-like phenotype observed in IL-6-competent mice. This indicated that endogenous cellular IL-6 is a critical co-factor in |