Abstract
Angiogenesis plays a critical role in tumor progression in various cancers, including neuroblastoma. We have previously shown that gastrin-releasing peptide (GRP) stimulates neuroblastoma growth and that its cell surface receptors, gastrin-releasing peptide receptors (GRP-R), are overexpressed in advanced-stage human neuroblastomas; however, the effects of GRP on angiogenesis are not clearly elucidated. Interleukin (IL) 8, a proinflammatory chemokine, plays an important role during tumor angiogenesis. Ets transcription factors, such as oncoproteins, cause tumor development and are also known to induce IL-8 expression. In the present study, we found an increased expression of Ets1 in more undifferentiated human neuroblastomas. Stable transfection of SK-N-SH human neuroblastoma cells with Ets1 plasmid resulted in increased IL-8 luciferase activity and IL-8 secretion into cell culture media. Conversely, silencing of Ets1 resulted in a significant decrease in IL-8 secretion in SK-N-SH cells. Moreover, exogenous GRP treatment increased Ets1 (T38) phosphorylation and Ets1 nuclear accumulation, and enhanced Ets1 binding to its DNA consensus sequence, resulting in the stimulation of IL-8 mRNA expression and protein secretion. Our findings demonstrate that GRP upregulates proangiogenic IL-8 expression in an Ets1-dependent manner, suggesting a critical role of this process during GRP-induced neuroblastoma angiogenesis and metastasis.