Response of experimental malignant melanoma models to the pan-Aurora kinase inhibitor VE-465

Abstract

Aurora kinases represent promising novel cancer therapy targets. Genomic analyses of human cutaneous melanoma (CMM) models (N = 51, low passage) by classical and/or array CGH revealed frequent gains at chromosome 20q (65%, amplifications in 45%) repeatedly including the Aurora A gene locus. Accordingly, the majority of CMM cell cultures overexpressed Aurora A when compared to proliferating non-malignant cells. Moreover, CMM cells even when arrested in G1/S cell cycle phase contained readily detectable levels of Aurora A indicating incomplete degradation during mitosis. Already at low concentrations (10-100 nm), long-term (7-10 days) application of the pan-Aurora kinase inhibitor VE-465 completely prevented colony formation in all CMM models tested. In contrast, blockade of cell survival/proliferation and DNA synthesis as well as the induction of apoptosis by VE-465 distinctly differed in short-term experiments (up to 72 h exposure). Both cell cycle arrest and DNA synthesis blockade depended on the level of VE-465-mediated p53/p21 activation while p53/p21 unresponsiveness led to repetitive endoreduplication (>8n DNA content). In contrast, apoptosis induction by VE-465 and Aurora A siRNA did not correlate with p53/p21 responsiveness and DNA synthesis blockade. Moreover, application of the Aurora B-specific inhibitor ZM447439 and siRNA was less efficient to induce CMM cell death proofing that apoptosis induction by VE-465 depended predominantly on Aurora A targeting. In combination experiments with chemotherapeutic agents, VE-465 acted additive to antagonistic when applied concomitantly but in several cases even synergistic when applied consecutively. In summary, we suggest that the Aurora A kinase might represent a promising target of well-designed novel antimelanoma strategies.