Using distinct cell types as in vitro models of cancer, fibrosis and VE-822 aberrant angiogenesis, evidence is provided that StSPL disrupts S1P receptor signaling and thus mitigates pathophysiologic processes associated with increased levels of extracellular S1P. Furthermore, we used the chicken chorioallantoic membrane as a neovascularization model to show the effect of StSPL on in vivo angiogenesis. As an in vitro model of diseases associated with aberrant angiogenesis, the effect of StSPL on the human endothelial cell line EA.hy 926 was investigated. Again, S1P stimulated classical p42/p44-MAPKs phosphorylation, which was blocked by WT StSPL but not the K311A mutant. In endothelial cells, S1P stimulates molecular events underlying angiogenesis, which includes cell proliferation and migration. Cycloheximide Indeed, we found that S1P stimulated EA.hy 926 cell proliferation , which was impeded by WT StSPL but not K311A. Moreover, undirected endothelial cell migration was also stimulated by S1P as measured in an adapted Boyden chamber assay , and this effect was similarly prevented by WT StSPL but not K311A. To exclude that the endothelial cells were stimulated by the degradation products of S1P, they were treated with 2E-hexadecenal at a concentration of up to 10 mM. However, we could not measure an effect on MAPK activation. Our data demonstrate the potential of StSPL to combat aberrant angiogenesis commonly associated with diseases like cancer, diabetic retinopathy and macular degeneration. To investigate whether StSPL is also active under extracellular conditions in vivo, the WT enzyme was injected in mice and the degradation of S1P in mouse plasma was measured. As shown in Fig. 7, 1 h after injection of StSPL plasma S1P levels decreased to about 70%. After 3 h, S1P levels were partly recovered and normal control levels were reached 6 h after injection. Although this indicates that there is scope for further pharmacological improvements to enhance efficacy, it clearly demonstrates that recombinant StSPL retains its enzymatic acitivity also in vivo upon intravenous injection. On the other hand, it indicates that the S1P blood pool was effectively replenished by continuous production in blood cells and that StSPL was eliminated from the circulation. To demonstrate that StSPL can alter an S1P-dependent phenotype also under in vivo conditions, we investigated its effect on neovascularisation in the developing chorioallantoic membrane of the chicken embryo. As a trigger for angiogenesis, spheroids of MCF-7 cells, which showed increased VEGF secretion upon StSPL treatment were placed on the CAM of E8 chicken embryos.