MicroRNA, MGMT Methylation and PTEN & P53 Mutations in Glioblastomas
Irene Rodriguez-Hernandez, Jose-Maria Gonzalez-Valero, Ana E Rodriguez, Juan-Antonio Gomez-Moreta, Angel Santos-Briz, Manuel Sanchez-Martin, Jesus-Maria Hernandez-Rivas, Rogelio Gonzalez-Sarmiento, Juan-Luis Garcia. IBMCC.USAL/CSIC, Salamanca, Spain; IECSCYL, Salamanca, Spain; IBSAL, Salamanca, Spain; Hospital Virgen Vega, Salamanca, Spain; Hospital Universitario, Salamanca, Spain
Background: Glioblastoma is the most common and malignant intrinsic brain tumor. Because of its extremely unfavorable prognosis, it is important to develop more effective diagnostic and therapeutic strategies based on biological and clinical sub classification system. Genomic profiling and miRNA expression profiling have suggested the existence of multiple glioblastoma subclasses,although their number and characteristics vary among studies.
Design: We analyzed microRNA expression profiles using the mirCURY LNA TM microRNA Arrays platform in 33 glioblastomas multiformes. All cases were studied at diagnosis, the median age was 66 years and the most frequent localization was temporal (40%).The median overall survival was 10 months. The promoter status of MGMT was determined by MLPA. By direct sequencing PTEN, EFGR and P53 mutations were analyzed. FISH for PTEN and EFGR was also evaluated. After extraction, microRNAS were labeled with Hy3TM/Hy5TM fluorescent label using the miRCURYTM LNA Array labeling kit (Exiqon, Denmark) and hybridized to the miRCURYTM LNA array v8.0. The hybridization and wash steps were performed according to the miRCURYTM LNA array manual in a Tecan HS 4800 ProTM hyb (Tecan, Austria). Scanning was performed in a Genepix 4000B scanner (Axon Instruments). The quantified fluorescence intensities were normalized using the global LOWESS.
Results: We found that miR-483-3p is overexpressed in 15% of GBM. Hsa-mir-483 is located within intron 2 of the IGF2 locus in 11p15. In 10% of cases Hsa-miR-541, Hsa-miR-621 and Hsa-miR-218, located in 14q32, 13q14.11, and 5q34 respectively, are overexpressed. MGMT hypermethylation was evaluated in 22 cases, and MGMT hypermethylation was detected in 7 cases (32%). A supervised analysis by SAM showed differential expression (FDR<0,005). Thus nmu-mir718 was downregulated in hypermethylated cases, while hsa-miR50* and hsa-mir 483-3p were up-regulated in moderate or absence of methylathion. The mutational analysis of PTEN and P53 genes showed differential expression between mutated and wild type cases, in about 50 microRNA. Regarding PTEN deletion, we also observed differential profiles.
Conclusions: MicroRNA expression helps to define clinically and genetically distinct glioblastoma subclasses. The use of a classification system may aid in the selection of subclass-specific therapies that will improve outcome for glioblastoma patients.
Wednesday, March 6, 2013 1:00 PM
Poster Session VI # 240, Wednesday Afternoon