Abstract 1293: Neutrophil gelatinase-associated lipocalin regulates the expression of angiogenic cytokines and VEGF in human breast and ovarian cancer cells

Abstract

Abstract Neutrophil gelatinase-associated lipocalin (NGAL; lipocalin 2) is a small extracellular protein (25 kDa) that is a member of the lipocalin protein family. It has been shown to bind ferric siderophores and to play an important role in iron metabolism. Increased NGAL levels have been reported in a variety of epithelial cancers, including breast, ovary, pancreas, colon, esophagus and thyroid cancer. We have recently reported that NGAL promotes breast cancer progression by inducing the epithelial to mesenchymal transition. In the course of these studies, we observed an increase in microvessel density in NGAL-expressing tumors. In the current study, we explored the potential role of NGAL in tumor angiogenesis by studying its effects on the expression of angiogenic factors. We first determined the levels of vascular endothelial growth factor (VEGF) in NGAL-expressing cells derived from the MCF-7 human breast cancer cell line. Using reverse-transcriptase PCR and ELISA, VEGF was found to be induced by NGAL at both the transcript and protein levels. Consistently, HIF-1α, one of the most important transcriptional regulators of VEGF, was observed to be accumulated in the nuclei of NGAL-expressing cells. Silencing of HIF-1α in NGAL-expressing cells significantly reduced VEGF expression. Consistent with this NGAL-induced VEGF production, there was a significant increase in endothelial cell migration towards the conditioned media collected from NGAL-expressing cells. Interestingly, treatment with a VEGF-neutralizing antibody only partially inhibited the migration-inducing activity of the conditioned media, suggesting that NGAL might induce the secretion of other angiogenic factors. To investigate this possibility, a panel of angiogenic factors was compared between the conditioned media collected from NGAL-expressing cells and control MCF-7 cells using antibody arrays. Several angiogenic cytokines, including IL-6, MCP-1 and GM-CSF, were found to be upregulated with NGAL expression. The effects of NGAL on VEGF and angiogenic cytokine production were also studied in SKOV-3 ovarian cancer cells. In this study, NGAL was silenced in SKOV-3 cells using specific siRNAs. The levels of both VEGF and IL-6 were found to be reduced after NGAL silencing, suggesting that NGAL's control of VEGF and cytokine production may be common among cancer cell types. These results suggest a novel mechanism through which NGAL may promote tumor angiogenesis and progression. (This work is supported by NIH R01 CA118764, P01 CA045548 and The Advanced Medical Foundation.) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1293.