Abstract 3458: Role of the EphB1 gene in mediating migration, proliferation, and radiosensitization of medulloblastoma cells

Abstract

Abstract Eph/ephrin signaling in a variety of cancers has been reported to promote aspects of tumorigenesis, including proliferation, migration, and angiogenesis. Medulloblastoma is an aggressive primitive neuroectodermal tumor originating in the cerebellum. Recently performed integrative genomic approach to a large cohort of medulloblastomas has identified four subtypes (A-D) based on clinical presentation, transcription profiles, genetic abnormalities, and clinical outcome. We show high levels of EphB1 expression in tumors derived from children with group D medulloblastomas, which are known to exhibit a poorer response to current therapies. The purpose of this study is to examine the effect knockdown of EphB1 has on cellular migration, proliferation, and radiosensitization of medulloblastoma tumors. Using a human-derived medulloblastoma cell line (DAOY) and small interfering RNA (siRNA) targeting EphB1, we compared cell migration in an electrical impedance-based transwell Boyden chamber assay (xCELLigence RTCA DP system). We show that siRNA knockdown of EphB1 results in significantly decreased migration. Assessment of proliferation by MTT assay indicates that knockdown of EphB1 affects cell cycle progression in DAOY. Results from cell cycle and sub-G1 analysis by flow cytometry demonstrate that knockdown of EphB1 results in G1 arrest. Our previous systems analysis investigation of global gene expression regulated by an intact ATM gene product also identified EphB1 as a downstream signaling molecule correlating with enhanced cellular radiation resistance. Our data strongly support EphB1 as an unequivocal target for radiation sensitization in human fibroblasts as well as in vitro medulloblastoma cell lines. siRNA knockdown of EphB1 expression in human medulloblastoma cell lines known to express high levels of EphB1 results in sensitization to ionizing radiation by clonogenic survival assays. Preliminary data from an in vivo xenograft medulloblastoma animal model suggest an enhanced response to radiation in tumors lacking the EphB1 gene. Our data indicate that EphB1 is a potential molecular target for medulloblastoma cancer treatment and radiosensitization. The mechanisms and downstream signaling cascades underlying EphB1's action on cell migration, proliferation, and cellular radiosensitization are currently under investigation. Citation Format: Nimrah A. Baig*, Olga Timofeeva*, Anatoly Dritschilo, Elena Pasquale, Marcel Kool, Brian Rood, Olga Rodriguez, Christopher Albanese^, Sana Karam^. Role of the EphB1 gene in mediating migration, proliferation, and radiosensitization of medulloblastoma cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3458. doi:10.1158/1538-7445.AM2014-3458