Lipoxins exert antiangiogenic and anti-inflammatory effects on Kaposi's sarcoma cells

Lipoxin A4 (LXA4) is an endogenously produced host molecule with anti-inflammatory resolution effects. Previous studies demonstrated it to be involved in anti-vascular endothelial growth factor (VEGF)-mediated angiogenesis and in a possible anticancer role via interaction with its receptor, lipoxin A 4 receptor (ALXR). Here, we examined the effects of LXA4 and its epimer 15-epi-LXA4 in inhibiting proinflammatory and angiogenic functions in a human Kaposi's sarcoma tumor-derived cell line (KS-IMM). KS-IMM cells expressed increased levels of inflammatory cyclooxygenase 2 (COX-2) and 5-lipoxygenase (5-LO) pathway enzymes when compared with human microvascular dermal endothelial cells (HMVEC-d). KS-IMM cells secreted high levels of prostaglandin E2 (PGE2) and chemotactic leukotriene B4 (LTB4). Treatment with LXA4 or 15-epi-LXA4 effectively reduced the levels of COX-2, 5-LO proteins, and secretion of PGE2 and LTB4 in KS-IMM cells. LXA4 or 15-epi-LXA4 treatment also decreased secretion of proinflammatory interleukin 6 (IL-6) and IL-8 cytokines but induced the secretion of anti-inflammatory IL-10. LXA4 treatment reduced the phosphorylation of VEGF receptor (VEGFR) and ephrin family receptor tyrosine kinases. LXA4 treatment effectively induced dephosphorylation of multiple cellular kinases such as Focal Adhesion Kinase, Protein kinase B, nuclear factor kappa-light-chain-enhancer of activated B cells, and Extracellular signal-regulated kinases (ERK)1/2, and reduced angiogenic factor VEGF-C secretion in KS cells. LX treatment drastically induced the Src-homology 2 domain-containing phosphatase tyrosine (Y542) phosphatase and reduced VEGFR-2 phosphorylation at sites Y1059, Y1175, and Y1212. Treatment of KS-IMM cells with LXA4 resulted in selective localization of VEGFR-2 in nonlipid raft (non-LR) and ALXR to LR fractions. These results demonstrated that LXA4 or 15-epi-LXA4 induce anti-inflammatory and antiangiogenic effects in KS cells and suggest that treatment with LXs is an attractive novel strategy against KS.