Data from HDM2 Regulation by AURKA Promotes Cell Survival in Gastric Cancer

Abstract

<div>Abstract<p><b>Purpose:</b> Suppression of P53 (tumor protein 53) transcriptional function mediates poor therapeutic response in patients with cancer. Aurora kinase A (AURKA) and human double minute 2 (HDM2) are negative regulators of P53. Herein, we examined the role of AURKA in regulating HDM2 and its subsequent effects on P53 apoptotic function in gastric cancer.</p><p><b>Experimental Design:</b> Primary tumors and <i>in vitro</i> gastric cancer cell models with overexpression or knockdown of AURKA were used. The role of AURKA in regulating HDM2 and cell survival coupled with P53 expression and activity were investigated.</p><p><b>Results:</b> Overexpression of AURKA enhanced the HDM2 protein level; conversely, knockdown of endogenous AURKA decreased expression of HDM2 in AGS and SNU-1 cells. Dual co-immunoprecipitation assay data indicated that AURKA was associated with HDM2 in a protein complex. The <i>in vitro</i> kinase assay using recombinant AURKA and HDM2 proteins followed by co-immunoprecipitation revealed that AURKA directly interacts and phosphorylates HDM2 protein <i>in vitro</i>. The activation of HDM2 by AURKA led to induction of P53 ubiquitination and attenuation of cisplatin-induced activation of P53 in gastric cancer cells. Inhibition of AURKA using an investigational small-molecule specific inhibitor, alisertib, decreased the HDM2 protein level and induced P53 transcriptional activity. These effects markedly decreased cell survival <i>in vitro</i> and xenograft tumor growth <i>in vivo</i>. Notably, analysis of immunohistochemistry on tissue microarrays revealed significant overexpression of AURKA and HDM2 in human gastric cancer samples (<i>P</i> < 0.05).</p><p><b>Conclusion:</b> Collectively, our novel findings indicate that AURKA promotes tumor growth and cell survival through regulation of HDM2-induced ubiquitination and inhibition of P53. <i>Clin Cancer Res; 20(1); 76–86. ©2013 AACR</i>.</p></div>