Abstract 572: Suppression of urokinase plasminogen activator receptor blocks recruitment of endothelial cells by inhibiting irradiation-induced monocyte chemo-attractant protein-1 in meningioma

Abstract

Abstract Chemokines, a common outcome of inflammatory reaction, play a vital role in recruiting various cell types during tissue repair. Radiation, a major therapeutic modality in cancer treatment, has been described to induce inflammatory response, which might lead to the expression of several chemokines. In the present study, we investigated the mechanisms underlying radiation-induced monocyte chemo-attractant protein (MCP-1) in meningioma cell lines and the paracrine effect on human microvascular endothelial cells (HMEC). Upon radiation, meningioma cell lines (IOMM Lee and SF 3061) showed an increased expression of MCP-1. In addition, irradiated meningioma cancer cell culture conditioned medium (CM) demonstrated an increased ability to attract HMEC and stimulated MCP1-induced protein (MCPIP), VEGF and angiogenin expression in HMEC as compared to HMEC grown in non-irradiated cancer cell CM. This chemotactic activity and angiogenic stimulator effect in HMEC was nearly abrogated by depleting MCP-1 from the irradiated cancer cell CM using a neutralizing anti-MCP-1 monoclonal antibody. Inhibition of ERK activation and NF-κB nuclear translocation hindered irradiation-induced MCP-1 expression in both meningioma cell lines. Considering that radiation induces uPA/uPAR expression and stimulates the ERK signaling pathway, we correlated the role of irradiation-induced uPA/uPAR in MCP-1 regulation. Supplementing cancer cells with exogenous ATF-uPA (with and without radiation) activated ERK phosphorylation, nuclear translocation of the NF-κB p65 sub-unit (Rel-A), and MCP-1 expression. Downregulation of uPA and uPAR by transfecting the cancer cells with a siRNA-expressing plasmid (pU) inhibited irradiation-induced ERK activation, nuclear translocation of Rel-A, NF-κB DNA binding activity, and MCP-1 expression. Further, pU-transfected cancer cells (with or with radiation) reduced the potential to attract and stimulate angiogenic signaling in HMEC under in vitro conditions. Under in vivo conditions, we observed that pU transfected cancer cells (with and without irradiation) showed a significant reduction in number of CD31+ endothelial cells and CD14+ monocytes present in the tumor regions compared to tumor formed from irradiated cancer cells. In conclusion, we demonstrated that blockade of uPA/uPAR expression inhibits irradiation-induced MCP-1, thereby inhibiting the chemo-attractant ability of cancer cells to recruit other cells during the inflammatory process induced by radiation. 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 572. doi:10.1158/1538-7445.AM2011-572