Most gene expression profiling studies of mesothelioma have been based on relatively small sample numbers, limiting their statistical power. We did Affymetrix U133A microarray analysis on 99 pleural mesotheliomas, in which multivariate analysis showed advanced-stage, sarcomatous histology and P16/CDKN2A homozygous deletion to be significant independent adverse prognostic factors. Comparison of the expression profiles of epithelioid versus sarcomatous mesotheliomas identified many genes significantly overexpressed among the former, including previously unrecognized ones, such as uroplakins and kallikrein 11, both confirmed by immunohistochemistry. Examination of the gene expression correlates of survival showed that more aggressive mesotheliomas expressed higher levels of Aurora kinases A and B and functionally related genes involved in mitosis and cell cycle control. Independent confirmation of the negative effect of Aurora kinase B was obtained by immunohistochemistry in a separate patient cohort. A role for Aurora kinases in the aggressive behavior of mesotheliomas is of potential clinical interest because of the recent development of small-molecule inhibitors. We then used our data to develop microarray-based predictors of 1 year survival; these achieved a maximal accuracy of 68% in cross-validation. However, this was inferior to prognostic prediction based on standard clinicopathologic variables and P16/CDNK2A status (accuracy, 73%), and adding the microarray model to the latter did not improve overall accuracy. Finally, we evaluated three recently published microarray-based outcome prediction models, but their accuracies ranged from 63% to 67%, consistently lower than reported. Gene expression profiling of mesotheliomas is an important discovery tool, but its power in clinical prognostication has been overestimated.

EWS-Fli1, a fusion gene resulting from the chromosomal translocation t(11;22, q24;q12), encodes a transcriptional activator, promotes cellular transformation, and is often found in Ewing sarcoma and primitive neuroectodermal tumor. The Aurora A and Aurora B kinases belong to a highly conserved family of serine/threonine protein kinases, are tightly regulated during the cell cycle, and are overexpressed in many carcinomas. Because the relationship between the Aurora A and/or Aurora B genes and the EWS-Fli1 fusion gene is unknown, we investigated the regulatory mechanism(s) by which Aurora kinases are controlled. Knockdown of EWS-Fli1 by small interfering RNA reduced mRNA levels not only of EWS-Fli1 but also of Aurora A and Aurora B. Luciferase assay using Aurora A and Aurora B promoters showed up-regulated activities compared with those of an empty vector. Experiments with deletion and point mutants showed positive regulatory Ets-binding sites located À84 and À71 bp upstream of the transcription initiation sites in Aurora A and Aurora B, respectively. Moreover, chromatin immunoprecipitation assay revealed that EWS-Fli1 gene products interact with both the Aurora A and Aurora B promoters. These results strongly suggest that the mitotic kinases Aurora A and Aurora B are regulated by EWS-Fli1 fusion protein in Ewing sarcoma cells.

EWS-Ewing sarcoma and other peripheral primitive neuroectodermal tumors are pediatric malignant solid tumors, Ͼ95% of which show the chromosomal translocations t(11;22, q24;q12) or t(21;22, q22;q12), which produce the fusion genes EWS-Fli1 and EWS-erg, respectively (1-4). Cytogenetic and molecular analyses of these translocation products have revealed that the 5Ј-region of the EWS gene (from band 22q12) is fused to the 3Ј-region of either the Fli-1 gene (from band 11q24) or the erg gene (from band 21q22), both of which are members of the ETS family of transcription factors. Less frequent chromosomal translocations involve the same region of the EWS gene and various other ETS genes, such as ETV-1, E1AF, or FEV (1, 2). We have previously shown that EWS preferentially binds to poly(G) and poly(U) RNA. The binding activity of EWS is located in the RGG box, which is in the carboxyl-terminal region.

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The present study demonstrated for the first time that combination of U0126 and LY294002 can augment the cytotoxicity of ActD against Ewing sarcoma cells in vitro and in vivo. Our results indicate that further study on combination of conventional chemotherapies with MEK and PI3K inhibitors may be considered for innovative treatments of Ewing sarcoma patients.