Abstract 288: PDGFR alpha and PDGFR beta differentially regulate cell proliferation and migration/invasion in medulloblastoma cells

Abstract

Abstract Medulloblastoma (MB) is the most common brain tumor in children and often spread to the spinal cord though the cerebrospinal fluid. Understanding the biological mechanism of this disease would provide a better care for these patients. Recently, overexpression of platelet derived growth factor receptor (PDGFR) alpha and beta has been linked to a metastatic stage of the disease. To comprehensively analyze the functions of PDGFRs and find their potential downstream targets in MB, we utilized Daoy cells, a metastatic MB cell line, as a MB model to assess the roles of PDGFR alpha and beta in this disease. The expression levels of PDGFR alpha and beta were determined by real time PCR and immunobloting. It was shown that Daoy cells express both PDGFR alpha and PDGFR beta. By using siRNAs to knockdown PDGFR alpha or beta specifically, and neutralizing antibody specific to PDGFR alpha and PDGFR beta respectively, it was demonstrated that PDGFR alpha signaling hinders cell proliferation and cell migration/invasion while PDGFR beta signaling promotes cell proliferation and migration/invasion. To elucidate the mechanism and find their potential downstream targets, total RNAs from the PDGFR knockdown cells were further analyzed by real time PCR and our results showed that PDGFR alpha and PDGFR beta signaling differentially modulate a set of genes which are important for cell death/surviving and proliferation such as NF kappa B, ATF3, Txnip and cMYC. To elucidate which pathway might govern the different roles of PDGFR alpha and beta in tumor cell proliferation/surviving, an NF kappa B report plasmid was co-transfected with siRNAs of PDGFRs into the MB cells and then the NF kappa B activities in the co-transfected cells were determined using a luciferase assay system. It was demonstrated that the NF kappa B activity was largely reduced in PDGFR beta knockdown cells, which suggested that PDGFR alpha and PDGFR beta may balance the cell proliferation/surviving signaling via cMYC and NF kappa B pathway. Furthermore, by analyzing the expression of cell surface protein on the PDGFR knockdown cells using immunohistochemistry staining, we demonstrated that CD44, a hall marker for cell migration/invasion was down regulated by PDGFR beta knockdown but not by PDGFR alpha knockdown, which implicated PDGFRs balance their migration/invasion signaling via CD44. Taken together, these data suggest that PDGFR alpha and PDGFR beta play different roles in cell proliferation and migration/invasion in MB brain tumor cells and these studies also highlight the potential of targeting PDGFRs signaling therapy in MB. 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 288.