A10228 Endothelial microparticles from vegf inhibitor (vegfi)-treated cancer patients mediates endothelial cell signaling and et-1 production

Abstract

Objectives: Vascular endothelial growth factor receptor inhibitors (VEGFRi), used as anti-angiogenic drugs to treat cancer, causes hypertension where mechanisms are still not fully elucidated. Microparticles (MPs) are biomarkers of cell damage. MPs also act as biovectors and influence vascular cell signalling and function. We questioned whether plasma levels of endothelial MPs from cancer patients treated with VEGFi are elevated (possibly reflecting underlying vascular injury) and whether these MPs influence endothelial cell signalling. Methods: Plasma MPs were isolated from cancer patients before and after treatment with VEGFRi (sunitinib, pazopanib or sorafenib). Human aortic endothelial cells (HAEC) were stimulated with isolated MPs (10*6 MPs/mL). MPs were characterized by flow cytometry; protein and gene expression by immunoblotting and qPCR; ROS and NO production by lucigenin and immunofluorescence. Results: VEGFRi treatment increased plasma endothelial cells-derived MPs (1.5 fold; p < 0.05 vs before treatment). HAEC exposed to post-treatment MPs increased pre-pro-ET-1 mRNA (9.1 fold; p < 0.01). Post-treatment MPs also increased ROS generation (5 min: 1.2 fold, p < 0.01; 30 min: 1.6 fold, p < 0.01; 60 min: 1.8 fold, p < 0.05) and phosphorylation of the inhibitory site of eNOS (Thr495) in HAEC (1.8 fold; p < 0.05). NO levels in HAEC exposed to MPs were decreased (1.2 fold; p < 0.05), an effect blocked by an ETB antagonist BQ788. Inflammatory marker gene expression was increased only in HAEC exposed to post-treatment MPs (p < 0.01). Conclusion: In conclusion, our data demonstrate that VEGFi treatment causes an increase in circulating MPs and that play a role in endothelial cell signalling and ET-1 production. These molecular processes may contribute to vascular dysfunction and hypertension in VEGFi-treated cancer patients.