Kaposi’s sarcoma (KS) is the most common cancer in HIV-infected untreated individuals. Kaposi’s sarcoma-associated herpesvirus (KSHV; also known as human herpesvirus 8 (HHV8)) is the infectious cause of this neoplasm. In this Review we describe the epidemiology of KS and KSHV, and the insights into the remarkable mechanisms through which KSHV can induce KS that have been gained in the past 16 years. KSHV latent transcripts, such as latency-associated nuclear antigen (LANA), viral cyclin, viral FLIP and viral-encoded microRNAs, drive cell proliferation and prevent apoptosis, whereas KSHV lytic proteins, such as viral G protein-coupled receptor, K1 and virally encoded cytokines (viral interleukin-6 and viral chemokines) further contribute to the unique angioproliferative and inflammatory KS lesions through a mechanism called paracrine neoplasia.

Approximately twelve percent of all human cancers are caused by oncoviruses. Human viral oncogenesis is complex and only a small percentage of the infected individuals develop cancer and often many years to decades after initial infection. This reflects the multistep nature of viral oncogenesis, host genetic variability and the fact that viruses contribute to only a portion of the oncogenic events. In this review, the Hallmarks of Cancer framework of Hanahan & Weinberg (2000 and 2011) is used to dissect the viral, host and environmental co-factors that contribute to the biology of multistep oncogenesis mediated by established human oncoviruses. The viruses discussed include Epstein Barr Virus (EBV), high-risk Human Papillomaviruses (HPV16/18), Hepatitis B and C viruses (HBV, HCV respectively), Human T-cell lymphotropic virus-1 (HTLV-1) and Kaposi’s sarcoma herpesvirus (KSHV).

The clinical benefit conferred by vascular endothelial growth factors (VEGF)-targeted therapies is variable, and tumors from treated patients eventually reinitiate growth. Here, we identify a glycosylation-dependent pathway that compensates for the absence of cognate ligand and preserves angiogenesis in response to VEGF blockade. Remodeling of the endothelial cell (EC) surface glycome selectively regulated binding of galectin-1 (Gal1), which upon recognition of complex N-glycans on VEGFR2, activated VEGF-like signaling. Vessels within anti-VEGF-sensitive tumors exhibited high levels of α2-6-linked sialic acid, which prevented Gal1 binding. In contrast, anti-VEGF refractory tumors secreted increased Gal1 and their associated vasculature displayed glycosylation patterns that facilitated Gal1-EC interactions. Interruption of β1-6GlcNAc branching in ECs or silencing of tumor-derived Gal1 converted refractory into anti-VEGF-sensitive tumors, whereas elimination of α2-6-linked sialic acid conferred resistance to anti-VEGF. Disruption of the Gal1-N-glycan axis promoted vascular remodeling, immune cell influx and tumor growth inhibition. Thus, targeting glycosylation-dependent lectin-receptor interactions may increase the efficacy of anti-VEGF treatment.

The Kaposi's sarcoma-associated herpesvirus (KSHV/HHV8) is a gamma-2 herpesvirus that is implicated in the pathogenesis of Kaposi's sarcoma and of primary effusion B-cell lymphomas (PELs). KSHV infects malignant and progenitor cells of Kaposi's sarcoma and PEL, it encodes putative oncogenes and genes that may cause Kaposi's sarcoma pathogenesis by stimulating angiogenesis. The G-protein-coupled receptor encoded by an open reading frame (ORF 74) of KSHV is expressed in Kaposi's sarcoma lesions and in PEL and stimulates signalling pathways linked to cell proliferation in a constitutive (agonist-independent) way. Here we show that signalling by this KSHV G-protein-coupled receptor leads to cell transformation and tumorigenicity, and induces a switch to an angiogenic phenotype mediated by vascular endothelial growth factor, an angiogenesis and Kaposi's-spindle-cell growth factor. We find that this receptor can activate two protein kinases, JNK/SAPK and p38MAPK, by triggering signalling cascades like those induced by inflammatory cytokines that are angiogenesis activators and mitogens for Kaposi's sarcoma cells and B cells. We conclude that the KSHV G-protein-coupled receptor is a viral oncogene that can exploit cell signalling pathways to induce transformation and angiogenesis in KSHV-mediated oncogenesis.

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Transfection of a Kaposi's sarcoma (KS) herpesvirus (KSHV) Bacterial Artificial Chromosome (KSHVBac36) into mouse bone marrow endothelial-lineage cells generates a cell (mECK36) that forms KS-like tumors in mice. mECK36 expressed most KSHV genes and were angiogenic, but they didn't form colonies in soft agar. In nude mice, mECK36 formed KSHV-harboring vascularized spindle cell sarcomas that were LANA+/podoplanin+, overexpressed VEGF and Angiopoietin ligands and receptors, and displayed KSHV and host transcriptomes reminiscent of KS. mECK36 that lost the KSHV episome reverted to nontumorigenicity. siRNA suppression of KSHV vGPCR, an angiogenic gene upregulated in mECK36 tumors, inhibited angiogenicity and tumorigenicity. These results show that KSHV malignancy is in vivo growth restricted and reversible, defining mECK36 as a biologically sensitive animal model of KSHV-dependent KS.

The t(4;14) translocation occurs frequently in multiple myeloma (MM) and results in the simultaneous dysregulated expression of 2 potential oncogenes, FGFR3 (fibroblast growth factor receptor 3) from der(14) and multiple myeloma SET domain protein/Wolf-Hirschhorn syndrome candidate gene 1 from der(4). It is now shown that myeloma cells carrying a t(4;14) translocation express a functional FGFR3 that in some cases is constitutively activated by the same mutations that cause thanatophoric dysplasia. As with activating mutations of K-ras and N-ras, which are reported in approximately 40% of patients with MM, activating mutations of FGFR3 occur during tumor progression. However, the constitutive activation of ras and FGFR3 does not occur in the same myeloma cells. Thus the activated forms of these proteins appear to share an overlapping role in tumor progression, suggesting that they also share the signaling cascade. Consistent with this prediction, it is shown that activated FGFR3-when expressed at levels similar to those seen in t(4;14) myeloma-is an oncogene that acts through the MAP kinase pathway to transform NIH 3T3 cells, which can then generate tumors in nude mice. Thus, FGFR3, when overexpressed in MM, may be not only oncogenic when stimulated by FGF ligands in the bone marrow microenvironment, but is also a target for activating mutations that enable FGFR3 to play a ras-like role in tumor progression. IntroductionChromosomal translocations to the immunoglobulin heavy-chain (IgH) locus on chromosome 14q32 are the hallmark of many B-cell malignancies, and their characterization has led to the identification of critical dysregulated oncogenes (eg, c-myc, bcl-2, cyclin D1) that play a key role in the pathogenesis of these diseases. In contrast, conventional cytogenetics failed to identify recurrent translocations in patients with multiple myeloma (MM). Recently, we developed a molecular approach and identified frequent IgH translocations in MM. 1 Three chromosome loci are most frequently involved-11q13, 16q23, and 4p16-with the consequent dysregulation of cyclin D1, c-maf, and fibroblast growth factor receptor 3 (FGFR3), respectively. [2][3][4] In particular, we previously reported that the novel, karyotypically silent t(4;14)(p16;q32) translocation occurs in approximately 20% of MM cells and tumors. 4 More recently, others 5,6 have confirmed a high incidence of t(4;14)(p16;q32) translocation in patients with MM. As a result of this translocation, the expression of 2 genes at the 4p16.3 locus is dysregulated. The expression of FGFR3 is dysregulated by juxtaposition to the 3Ј C␣ enhancer on der(14), whereas multiple myeloma SET domain protein/Wolf-Hirschhorn syndrome candidate gene 1 (MMSET/WHSC1) is dysregulated by association with the intronic enhancer (E) on der(4). 7 It remains unclear how each of these dysregulated genes contributes to the pathogenesis of MM.FGFR3 is one of 4 high-affinity tyrosine kinase receptors for the FGF family of ligands. It is normally expressed in the lungs and kidneys, and it is...

Disrupting Gal-1 interactions with N-glycans prevents hypoxia-driven angiogenesis to suppress tumorigenesis of Kaposi’s sarcoma