Abstract
Background: Neutrophil gelatinase-associated lipocalin (NGAL), a member of the lipocalin family, is a secreted protein that is upregulated in multiple cancer types. Our group previously reported that NGAL overexpression significantly blocked invasion and angiogenesis in pancreatic ductal adenocarcinoma (PDAC). We and others have also demonstrated loss NGAL expression in advanced stages of PDAC. However, little is known about mechanisms that regulate NGAL expression in PDAC. As EGF-EGFR axis is significantly upregulated in PDAC, we examined EGF-mediated NGAL regulation in these cells.
Methods: NGAL-positive AsPC-1 and BxPC-3 cells were used as model system. Quantitative RT-PCR, western blot analysis, and immunofluorescence studies were used to investigate EGF-mediated effects on NGAL expression. E-cadherin expression was manipulated using lentiviral overexpression or shRNA constructs. NGAL promoter activity was assessed by luciferase-reporter assay and electrophoretic mobility shift assay (EMSA).
Results: NGAL expression was positively associated with tumor differentiation and was significantly downregulated after EGF treatment along with a concomitant reduction of E-cadherin expression in PDAC cells. E-cadherin downregulation was partly through the EGF receptor (EGFR)-dependent MEK1/2-ERK1/2 signaling pathway, which was demonstrated using pharmacologic inhibitors of EGFR (AG1478) and MEK1/2 (U0126 and PD98059). In addition, E-cadherin downregulation reduced NGAL expression in PDAC cells, whereas overexpression of E-cadherin led to increased NGAL expression and partly rescued inhibition of NGAL expression by EGF. Furthermore, EGF in part through E-cadherin reduced NGAL promoter activity by blocking NF-κB activation.
Conclusion: We demonstrated for the first time that EGF potently blocked NGAL expression in PDAC cells. This effect is partly mediated through activation of the EGFR-MEK1/2-ERK1/2 signaling pathway, which in turn downregulated E-cadherin with a subsequent reduction in NF-κB activation. Our findings illustrate a novel mechanism by which EGF regulates NGAL expression in PDAC.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5008. doi:10.1158/1538-7445.AM2011-5008
- ©2011 American Association for Cancer Research
Volume 71, Issue 8 Supplement
