Introduction: There is a need for a more robust, histology independent classification of astrocytomas. MicroRNAs (miRNAs) are a class of small noncoding RNAs that regulate protein synthesis at the post transcriptional level. Increased in vitro and in vivo evidence indicates that several miRNAs are dysregulated in all cancers including astrocytomas. We performed microRNA arrays and collected tumor tissue, blood and saliva to correlate microRNA expression levels with tumor grade.
Methods: MiRNAs-containing total RNA was isolated from archived formalin-fixed paraffin-embedded (FFPE) samples of WHO grade II-IV astrocytoma patients (N=15, 5 per tumor grade). FFPE samples from normal subjects were used as controls (N=5). RNA was extracted using the RecoverAll™ Total Nucleic Acid Isolation Kit (Ambion). RNA was labeled and hybridized to Affymetrix miRNA 2.0 arrays. Statistical analysis was performed with the PARTEK software. Ingenuity Pathway analisyis was used to construct molecular pathways associated with some of the most regulated miRNAs. Blood was collected from GBM patient and control individuals. Total RNA was isolated from plasma with the RNeasy mini kit (QIAGEN). cDNA synthesis was performed with the miScript II RT Kit (Sabiosciences). Real-time PCR was performed in a miScript miRNA 96-well PCR array (Sabiosciences) which contains 88 different miRNAs.
Results: PARTEK analysis identified 85 miRNAs differentially regulated in grade II, 72 miRNAs in grade III and 118 miRNAs in GBM compared with control samples. TAqMan-based assays confirmed the microRNA arrays findings. Some microRNAs resulted differentially abundant in the plasma of GBM patients vs. control individuals.
Conclusions: For each astrocytoma grade there is a characteristic miRNA expression profile. Some miRNAs are differentially abundant in all astrocytoma grades. In the future these miRNAs could be used as an aid in early diagnosis, progression follow up, and targets for therapy. Our results provide miRNA signatures to distinguish between WHO grade II, III and IV astrocytomas.
Patient Care: I believe microRNA will be helpful as a diagnostic aid and therapeutic target in the future of astrocytoma care.
Learning Objectives: By the conclusion of this session, participants should be able to: 1)Understand what a microRNA is 2)identify the dysregulated microRNAs presented in each astrocytoma grade. 3)Understand the role of microRNA in tumor proliferation and drug resistance