Abstract 732: Characterization of gene expression changes associated with Erlotinib and Temsirolimus treatment in glioma cell lines
Authors: Garcia-Claver Ainoha , Perez-Diaz Gema , Granda Carmen , Campos-Martin Yolanda , Ruano Yolanda , Perez-Magan Elisa , Mollejo Manuela , Melendez Barbara 
Published: June 2012

Abstract
Background: The use of tyrosine kinase inhibitors as erlotinib (ERL) has been widely studied for the treatment of human tumors including malignant glioma. To enhance the effect of ERL, coadyuvant treatment with an inhibitor downstream the EGFR pathway, such as temsirolimus (TEMS), has been proposed (Wang et al, 2006). Here, we analyze the gene expression profiles of a large series of human glioma cell lines with different sensitivity to ERL and TEMS, to identify the molecular effects of both inhibitors.
Materials and methods: Eleven glioma cell lines (U373, U87MG, U118, SW1088, A172, SW1783, H4, GOS3, LN18, SF767, T98G) where treated for 24 hours in a serum-starved medium with 10µM ERL alone or in combination with 0,01µM TEMS. Both treatments and basal cultures were stimulated with 50ng/ml EGF during treatment. Total RNAs were trizol extracted. After cDNA synthesis and labeling, hybridations were made on Agilent's Whole Human Genome expression arrays that consist of about 40,000 genes. Statistical analyses were done with GEPAS and Babelomics.
Results: The samples, treated with ERL, ELR+TEMS or untreated, significantly grouped by cell line independently of treatment. There are 52 differentially expressed genes (FDR&lt;0,15) between treated and untreated cell lines. Among them, Gas5, which promotes apoptosis, raised its expression in treated cell lines, while PLK1 and BIRC5, that activates cell cycle and inhibits apoptosis, respectively, diminished its expression with treatment (FDR&lt;0.05). Analyses of gene ontologies (GO) showed 3 BIOCARTA pathways overexpressed before treatment in these cell lines (p&lt;0,05). Two of them related to cell cycle control (Ran and Akap95 pathways) and one to invasiveness and metastatis (Mta3 pathway).
Besides, we compared cell lines with different sensitivity to erlotinib (8 resistant and 3 sensitive, as characterized by viability assays) in order to identify genes responsible of the different response to ERL. Among the 1,191 significant deregulated genes (FDR&lt;0.15), we observed HRAS overexpression in resistant cell lines. In addition, 29 transcription factors were diferentially expressed (p&lt;0,05). Remarkably, Hes-1 also overexpressed in resistant cell lines, is involved in neurogenesis and keeps cells indiferenciated and in proliferation.
Conclusion: Although further confirmation of these results is needed, we have found that treatment of cell lines with ERL and ERL+TEMS affect cell cycle and cell growth. In addition, we have identify genes that could be related to the diferential response to ERL treatment in glioma cell lines, such as Hras and Hes-1.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 732. doi:10.1158/1538-7445.AM2011-732