The impact of EPLINα (Epithelial protein lost in neoplasm) on endothelial cells, angiogenesis and tumorigenesis

EPLIN (epithelial protein lost in neoplasm) is a cytoskeletal associated protein involved in the regulation of actin dynamics and subsequently in cell motility. EPLIN expression is frequently reduced in a variety of cancer cells and tissues and this loss may account for increased invasive traits in cancer cells. The current study aimed to assess the role of EPLIN in endothelial cells and the angiogenic process. EPLIN alpha expression was enhanced in HECV endothelial cells through transfection with a pEF6 expression plasmid containing the full coding sequence of EPLIN alpha. The impact of EPLIN alpha on HECV cells was then assessed using a range of in vitro and in vivo models. Transfection and over-expression of HECV cells with EPLIN alpha expression plasmid resulted in a significant reduction in cell-matrix adhesion (P = 0.003), the rate of migration (P = 0.009) and tubule formation (P = 0.007) and also enhanced paxillin staining compared to transfection controls. Additionally, MDA-MB-231 breast cancer cells co-injected with HECVEPLIN exp cells developed at a slower rate than those co-injected with HECVpEF6 cells (day 26, P = 0.05; day 33, P = 0.065, overall deviation over time P < 0.001). Treatment of HECVEPLIN exp cells with ERK inhibitor could rescue HECV cells from the inhibitory effect of EPLIN alpha over-expression on tubule formation, returning these cells to control levels. EPLIN alpha over-expression can regulate HECV cell motility, matrix adhesion and tubule formation in vitro and slow in vivo tumour formation, suggesting an anti-angiogenic role for EPLIN alpha. Extracellular signal-regulated kinase (ERK) also appears to be linked to the ability of EPLIN alpha to inhibit tubule formation in vitro.