Abstract
Abstract Glioblastoma (GBM) is the most aggressive tumor of the human brain, which inevitably escapes the standard treatment modalities that include surgery, radiotherapy and chemotherapy. Consequently, the median survival of GBM patients remains 12-15 months despite these aggressive treatments. Therefore, to develop effective therapies, it is important to understand how GBM cells develop therapeutic resistance. Aurora A is a ubiquitously expressed serine/threonine kinase, which plays essential roles in mitotic regulation. This protein kinase, which phosphorylates p53, PP1, CEBP, and histone H3 among other regulators of cell division, is overexpressed in various neoplasms including GBM and invariably associated with poor prognosis. Recent studies have demonstrated that Aurora A contributes to radio-resistance in various solid neoplasm including GBM. Importantly, Aurora A inhibitors are currently in phase I/II clinical trials for solid cancer. Notably, Aurora A inhibitor MLN8237 that crosses the blood brain barrier specifically inhibits Aurora A at concentrations ≤ maximally tolerated dose in animal models and in phase I clinical trials. We found that Aurora A protein level is upregulated by ionizing radiation in GBM cells. This was, in part, mediated by radiation-induced inhibition of 26S-proteosomal degradation of Aurora A. Aurora A was silenced using both lentiviral mediated shRNA expression and a specific Aurora A inhibitor in three different established cell lines, and were treated with 6 gy radiation. We found that pharmacological inhibition and RNAi-mediated knockdown of Aurora A sensitized the GBM cells to radiation therapy resulting in reduced cell proliferation and increased apoptosis. Interestingly, we observed that RNAi-mediated down-regulation of Aurora A was associated with a decrease in X-linked inhibitor of apoptosis (XIAP) expression in GBM cells. We also found that Aurora A and XIAP were co-localized in GBM cells. Taken, together our results reveal a mechanism by which Aurora A confers radio-resistance in GBM cells and further rationalize the use of Aurora A inhibitors as radio-sensitizer in solid neoplasms including GBM. Funding sources: This work was supported by R01CA108633 (To AC), 1RC2CA148190 (To AC) U10CA180850-01 (To AC), 1R01CA169368 (To AC) from the National Cancer Institute (NCI), Brain Tumor Funders Collaborative Grant (To AC), Ohio State University Comprehensive Cancer Center Award (To AC) Citation Format: Brinda Ramasubramanian, Kamalakannan Palanichamy, Disha Patel, Saikh Jaharul Haque, Arnab Chakravarti. Role and regulation of Aurora A in radiation resistance mechanisms in glioblastoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 522.
Published Version
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