Abstract 2172: Deregulation of the mitotic spindle assembly checkpoint pathway in malignant pleural mesothelioma (MPM) tumors revealed by gene expression profiling

Abstract

Abstract MPM is a lethal neoplasm exhibiting low median survival of patients and lacks effective therapeutic options. There is an urgent need to understand the underlying pathobiology and discover novel therapeutic targets. We undertook a messenger RNA (mRNA) expression profiling strategy to determine the pathways and biomarkers significantly altered in MPM tumors. We isolated total RNA from 55 MPM tumors with 38 paired controls representing 39 epitheloid, 8 biphasic and 6 sarcomatoid cases. The paired controls were adjacent non-tumor tissue samples and histopathological analysis revealed a tumor content of greater than 70 % in most of these tumors cases. The RNA was labeled and hybridized onto Affymetrix U133 Plus 2.0 chips to ascertain the global expression profile in these tumors. Bioinformatic analysis of the microarray data using a two sample t-test was applied on a probe-by-probe basis followed by Beta-uniform Mixture for multiple comparisons. Finally paired t-test was applied to determine the differences between tumor vs normal samples. About ∼955 highly significant probesets representing ∼ 670 genes, at a FDR of e-09, were obtained and subjected to pathway analysis using MetaCore software suite (GeneGo, Inc.). The most significantly altered pathway in MPM tumors was the Mitotic Spindle Assembly Checkpoint (MSAC) pathway due to up-regulation of at least 15 genes including a ∼3.4 fold increase in Aurora kinase A, which is currently being explored in other cancers as a potential therapeutic target. The other genes belonging to this pathway, also up-regulated in tumors, include Mad2L1 and BUBR1 which together regulate cell division cycle 20 (Cdc20) protein, an essential cofactor needed by the Anaphase Promoting Complex to initiate the anaphase of cell cycle. Interestingly we also discovered that some of the MSAC pathway genes show a histotype-specific graded expression pattern with higher levels in sarcomatoid tumors compared to biphasic tumors and with lowest expression levels seen in epitheloid tumors. Additionally survivin, the product of which localizes to the mitotic spindle and negatively regulates apoptosis by inhibiting caspase activation, was expressed more than 2 fold in MPM tumors compared to normal samples. The microarray data also revealed other pathways significantly upregulated in MPM tumors including the Wnt and Cell-Adhesion signaling pathways. We are currently validating the expression microarray data using quantitative Polymerase Chain Reaction (PCR) platform with respect to key components of MSAC pathway. This will be followed by proteomic analysis of these components on tumor lysates to confirm the alterations in their expression profiles. Supported by Grants: DOD PROSPECT W81XWH-07-1-030602, Fleming Foundation for Mesothelioma Research, Aileen Dillon and Lee Bourg Mesothelioma Endowment and NIH K12 CA088084 08 award. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2172.