The Inflammatory Kinase MAP4K4 Promotes Reactivation of Kaposi's Sarcoma Herpesvirus and Enhances the Invasiveness of Infected Endothelial Cells

Kaposi's sarcoma (KS) is a mesenchymal tumour, which is caused by Kaposi's sarcoma herpesvirus (KSHV) and develops under inflammatory conditions. KSHV-infected endothelial spindle cells, the neoplastic cells in KS, show increased invasiveness, attributed to the elevated expression of metalloproteinases (MMPs) and cyclooxygenase-2 (COX-2). The majority of these spindle cells harbour latent KSHV genomes, while a minority undergoes lytic reactivation with subsequent production of new virions and viral or cellular chemo- and cytokines, which may promote tumour invasion and dissemination. In order to better understand KSHV pathogenesis, we investigated cellular mechanisms underlying the lytic reactivation of KSHV. Using a combination of small molecule library screening and siRNA silencing we found a STE20 kinase family member, MAP4K4, to be involved in KSHV reactivation from latency and to contribute to the invasive phenotype of KSHV-infected endothelial cells by regulating COX-2, MMP-7, and MMP-13 expression. This kinase is also highly expressed in KS spindle cells in vivo. These findings suggest that MAP4K4, a known mediator of inflammation, is involved in KS aetiology by regulating KSHV lytic reactivation, expression of MMPs and COX-2, and, thereby modulating invasiveness of KSHV-infected endothelial cells. © 2013 Haas et al

Sarcostemma viminale activates macrophages to a pro-inflammatory phenotype

Sarcostemma viminale (L.) R.Br, also known as caustic or milk bush, is a semi-succulent plant commonly found in the North West of Australia. Local Aboriginal populations have long used the milky white sap from this plant to treat skin cancers. An ethanol extract from S. viminale was tested by exposing the RAW264.7 cell line as an in vitro murine macrophage model, to the extract. Flow cytometric analysis was performed to determine if S. viminale skewed macrophages towards a pro-inflammatory or anti-inflammatory phenotype using a number of cell surface markers. Cell culture supernatants were also analysed by cytometric bead array to determine if S. viminale exposed macrophages produced pro-inflammatory or anti-inflammatory cytokines. After exposure to S. viminale, a significantly greater number of macrophages expressed pro-inflammatory major histocompatibility complex (MHC) class II molecules and significantly greater expression levels of the dendritic cell marker CD11c. Cytometric bead array analysis found that S. viminale induced significant amounts of the potent pro-inflammatory cytokine tumour necrosis factor (TNF) from macrophages. The markers CD40 and ICAM-1 were expressed but were not significantly different from the controls. Also, significantly higher expression of CX3CR1 indicated that macrophages were preparing to migrate. No anti-inflammatory cytokines were produced. No significant production of NO2-, IL-6, IFN-? or IL-12 was found. These results demonstrate that S. viminale drives resting macrophages into a pro-inflammatory phenotype, reminiscent of activated immature dendritic cells. If this activation could be achieved in the peri-tumour environment, then S. viminale could be useful as an adjunct therapy for skin cancer. © 2014 Springer-Verlag London