Abstract 5602: Molecular mechanism underlying acquired resistance to Aurora A kinase inhibitor, Alisertib, in melanoma
Authors: Vilgelm Anna E. , Liu Yan , Levy Shawn , Richmond Ann 
Published: August 2012

Abstract
Malignant melanomas are notorious for their resistance to chemotherapeutic treatments. Thus the development of new therapeutic strategies that will allow overcoming drug resistance is essential. We have previously shown that Aurora A kinase (AurkA) inhibitor Alisertib (MLN8237) inhibited melanoma cell grouth by blocking mitosis and inducing senescence. In this study we used melanoma patients’ tissue specimens implanted under the skin of athymic mice and mouse melanoma tumors grown in immune-competent mice. Treatment with Alisertib inhibited melanoma tumor growth in both model systems. However, most of tumors re-grew after the treatment was paused and some of them acquired resistance to a second round of chemotherapy. Interestingly mouse melanoma cells collected from chemo-resistant tumors retained their resistance to Alisertib treatment when re-implanted into new hosts. In order to gain understanding of the molecular events facilitating Alisertib resistance we performed whole transcriptome sequencing in mouse melanoma tumors. Each Alisertib-treated tumor showed a large number of genomic alterations with the number of single nucleotide variations in protein-coding transcripts ranging from 807 to 2036. In total 613 genes were affected across 6 analyzed samples and among those, 253 genes carried nucleotide variations exclusively in drug resistant tumors. In silico pathway analysis revealed a statistically significant enrichment of this resistance-associated gene set with genes involved in cell cycle regulation (p&lt;0.0001). Among those were important regulators of cell cycle checkpoints, DNA repair and DNA damage response such as p53, Sesn3, TSC2, Camk2d, Lig1, Usp19, Slbp, Dgkz and Rpl24. This data together with our previous findings that that Alisertib induces polyploidy and subsequent activation of DNA damage response suggests that endoreduplication (DNA re-replication after failed mitosis) may promote the development of chemo-resistance in melanomas. We also found that Alisertib-induced endoreduplication can be blocked through activation of endogenous p53. Treatment with inhibitor of p53 degradation, Nutlin-3, significantly reduced Alisertib-associated polyploidy by inhibiting Rb phosphorylation and expression of genes involved in DNA replication licensing. This coincided with a decrease in phosphorylation levels of DNA-damage sensor histone H2AX and effector kinase Chk2. Notably, co-treatment with Nutlin-3 neither rescued melanoma cells from cytostatic effect of Alisertib treatment nor reversed Alisertib-induced senescence. Our findings suggest that pharmacological activation of endogenous p53 in combination with AurkA inhibitors could block endoreduplication-related genomic instability and potentially delay the development of drug resistance in melanoma tumors. This work was supported by grants from the NIH (CA116021-07) and VCORCDP (CA90625-11).
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 5602. doi:1538-7445.AM2012-5602