BACKGROUND. Gliomas account for approximately 80% of all primary malignant brain tumors and, despite advances in clinical care, remain still associated with poor prognosis. They are currently classified by the WHO system in Low Grade Gliomas (LGGs, WHO I, II) and High Grade Gliomas (HGGs, WHO grade III, IV) based on histological features such as nuclear atypia, mitotic figures, microvascular proliferation and necrosis. LGGs and HGGs share several morphological traits and pathways abnormalities but have a different clinical behaviour. miRNAs have emerged as key regulators of many biological processes mediating genesis and dissemination of cancer. Molecular analyses based on miRNA measurements have shown to be able to better stratify and discriminate the two tumor types. We hypothesize the comparison of miRNA profile between LGGs and HGGs may lead to the identification of miRNAs associated with the most aggressive form, that is GBM (Glioblastoma Multiforme, WHO IV). MATERIAL AND METHODS. miRNA expression profiling was performed in 8 LGGs, 24 HGGs, and 4 Normal Brain Tissues (NBT) by using the Affymetrix GeneChip® miRNA Array 1.0. Data analysis was performed by Partek Genomic Suite software, setting a significative p-value ≤ 0.01 and a fold change cutoff of 2. A relative quantification method (RT-qPCR) with standard curve was used to validate the 22 miRNA signature resulted by array analysis. The prognostic performance of the 13 validated miRNAs was estimated by using the Tumor Cancer Genome Atlas (TCGA). RESULTS. miRNA profiling identified 80 miRNAs differentially expressed in LGGs vs NBT and 71 in HGGs vs NBT. A panel of 22 miRNAs clearly differentiated HGGs and LGGs. RT-qPCR assay confirmed differential expression for 13 out of the 22 miRNAs in LGG vs HGG. In addition, 6 among our 13-miRNA signature (miR-21, miR-210, miR-22, miR-155, miR-223, miR-219-2-3p) were found to be significantly associated with GBM molecular subtypes when compared on TCGA dataset. Moreover miR-21 and miR-210 show correlation with worse overall survival in both univariate and multivariate Cox Regression analysis (HR 1.19 95% CI 1.008-1.406 p=0.04; and 1.18 95%C 1.018-1.375 p=0.03). CONCLUSIONS. We show the comparison of LGGs and HGGs profiles is able to identify miRNAs associated with invasive phenotype. Our results support a direct involvement of miR-21 and miR-210 in glioma progression, suggesting they may represent promising targets for new therapeutic approaches in gliomas.
A miRNA signature distinguishing low-grade and high-grade gliomas shows miR-21 and 210 as promising biomarkers of aggressive phenotype and prognosis
2014-01-01
Abstract
BACKGROUND. Gliomas account for approximately 80% of all primary malignant brain tumors and, despite advances in clinical care, remain still associated with poor prognosis. They are currently classified by the WHO system in Low Grade Gliomas (LGGs, WHO I, II) and High Grade Gliomas (HGGs, WHO grade III, IV) based on histological features such as nuclear atypia, mitotic figures, microvascular proliferation and necrosis. LGGs and HGGs share several morphological traits and pathways abnormalities but have a different clinical behaviour. miRNAs have emerged as key regulators of many biological processes mediating genesis and dissemination of cancer. Molecular analyses based on miRNA measurements have shown to be able to better stratify and discriminate the two tumor types. We hypothesize the comparison of miRNA profile between LGGs and HGGs may lead to the identification of miRNAs associated with the most aggressive form, that is GBM (Glioblastoma Multiforme, WHO IV). MATERIAL AND METHODS. miRNA expression profiling was performed in 8 LGGs, 24 HGGs, and 4 Normal Brain Tissues (NBT) by using the Affymetrix GeneChip® miRNA Array 1.0. Data analysis was performed by Partek Genomic Suite software, setting a significative p-value ≤ 0.01 and a fold change cutoff of 2. A relative quantification method (RT-qPCR) with standard curve was used to validate the 22 miRNA signature resulted by array analysis. The prognostic performance of the 13 validated miRNAs was estimated by using the Tumor Cancer Genome Atlas (TCGA). RESULTS. miRNA profiling identified 80 miRNAs differentially expressed in LGGs vs NBT and 71 in HGGs vs NBT. A panel of 22 miRNAs clearly differentiated HGGs and LGGs. RT-qPCR assay confirmed differential expression for 13 out of the 22 miRNAs in LGG vs HGG. In addition, 6 among our 13-miRNA signature (miR-21, miR-210, miR-22, miR-155, miR-223, miR-219-2-3p) were found to be significantly associated with GBM molecular subtypes when compared on TCGA dataset. Moreover miR-21 and miR-210 show correlation with worse overall survival in both univariate and multivariate Cox Regression analysis (HR 1.19 95% CI 1.008-1.406 p=0.04; and 1.18 95%C 1.018-1.375 p=0.03). CONCLUSIONS. We show the comparison of LGGs and HGGs profiles is able to identify miRNAs associated with invasive phenotype. Our results support a direct involvement of miR-21 and miR-210 in glioma progression, suggesting they may represent promising targets for new therapeutic approaches in gliomas.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
