Abstract 3118: Platelet-derived growth factor-D contributes to aggressiveness of breast cancer cells by up-regulation of Notch and NF-κB signaling pathways

Abstract

Abstract Platelet-derived growth factor-D (PDGF-D) has been suggested to be associated with progression of several human malignancies; however, its role in breast cancer progression has not been investigated. We found that PDGF-D expressing breast cancer cell lines MDA-MB-231 and SUM-149 are more aggressive compared to the cell lines with little or no expression of PDGF-D, such as MDA-MB-468 and MCF-7 cells. In order to test our hypothesis that PDGF-D influences cell proliferation, invasion and metastasis mediated by the activation of Notch and NF-κB signaling, we over-expressed PDGF-D in MDA-MB-468 and MCF-7 by cDNA transfection as well as silenced it in MDA-MB-231 and SUM-149 cells using PDGF-D siRNA, for mechanistic studies. We found that PDGF-D over-expression increased cell proliferation while its silencing resulted in decreased cell proliferation and increased induction of apoptosis. PDGF-D expression correlated with the activated expression of several members of Notch-signaling, namely, Notch-1, Notch-4 and Jagged-1, and attenuation of PDGF-D levels led to the inactivation of Notch signaling. PDGF-D over-expression was also found to induce the expression of mesenchymal markers (Vimentin and ZEB-2) concomitant with decreased expression of epithelial marker E-cadherin, which appears to be one of the mechanism by which PDGF-D may contribute to the aggressiveness of breast cancer cells. Since NF-κB plays a crucial role in Notch signaling as well as in the processes of epithelial-mesenchymal transition (EMT), we studied the effect of PDGF-D signaling on the DNA binding activity of NF-κB. We found that PDGF-D over-expression led to increased expression of Notch-1 and increased the DNA binding activity of NF- κB whereas the silencing of PDGF-D reduced the expression of Notch-1 and also reduced the DNA binding activity of NF-κB, suggesting that PDGF-D is upstream of Notch and NF-κB signaling pathways. These results were also consistent with the expression and activity of MMP-9 and VEGF, as well as invasive characteristics. From these results, we conclude that PDGF-D plays an important role in breast tumor aggressiveness and this process is mechanistically linked with Notch-1 and NF-κB signaling. 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 3118.