Abstract 2485: Combined Src and aurora kinase inhibition in medulloblastoma

Abstract

Abstract Src kinase is overexpressed in many human cancers, including medulloblastoma (MB), the most common malignant pediatric brain tumor. Src plays a central role in many oncogenic signaling pathways, and has been implicated in cell migration. Recently, we observed that blockade of aurora kinases A and B, which regulate cell cycle progression and are expressed by MB cells, also inhibits MB proliferation and migration. Because metastatic disease is such a powerful predictor of survival in MB patients, we hypothesized that combined Src and aurora kinase inhibition may act in a synergistic manner to more effectively inhibit MB growth and progression. To test this hypothesis, we investigated the effects of Dasatinib, a potent Src inhibitor, and AT9283, an inhibitor of aurora kinases A and B, alone and in combination, against a panel of MB cells in vitro and in a mouse flank tumor model in vivo. In two human MB cell lines (DAOY, D556), we show a dose-dependent decrease in phosphorylation of Src and histone-H3 when treated with Dasatinib and AT9283 respectively. This correlated with decreased cell viability measured by MTT assay after treatment with each agent (Dasatinib 1nM, AT9283 10nM). When treated at hour 0 and measured at hour 96, without drug replenishment, Dasatinib inhibits cell viability by 57% (DAOY) and 86% (D556), and AT9283 inhibits viability by 47% (DAOY) and 76% (D556), compared to control. Viability was more potently inhibited in DAOY cells when used in combination at the above concentrations, decreasing by 81% compared to control. Similarly, in a mouse MB cell line (PS125), viability decreased by 47% and 48% after treatment with Dasatinib at 10nM and AT9283 at 10nM respectively. Interestingly, in PS125 cells, Dasatinib at 3nM did not impact viability, but when combined with AT9283 at 10nM, a marked decrease was observed compared to AT9283 at 10nM alone (70% vs 48%). Each agent also inhibits migration when measured by scratch assay. When treated with Dasatinib at 1nM, cell movement decreased by 94% (DAOY) and 60% (D556) at 24 hours, and 29% (DAOY) and 50% (D556) at 48 hours, without drug replenishment. Similarly, movement decreased by 42% (DAOY) and 23% (D556) at 24 hours, and 30% (DAOY) and 3% (D556) at 48 hours, when treated with AT9283 at 10nM. Movement was more potently inhibited when drugs were combined at the above concentrations, decreasing by 100% (DAOY) and 85% (D556) at 24 hours, and 82% (DAOY) and 90% (D556) at 48 hours, compared to control. Additionally, our preliminary in vivo data suggest that Dasatinib inhibits tumor growth in mice with implanted syngeneic flank tumors (PS125 cells). By day 20 of Dasatinib treatment (15 mg/kg po daily M-F), tumors were 36% smaller in treated mice compared to controls, without obvious differences in toxicity. We conclude that combined inhibition of Src and aurora kinases appears to synergistically inhibit proliferation and migration of MB cells in vitro, and Src inhibition appears to inhibit MB tumor growth in vivo. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2485. doi:1538-7445.AM2012-2485