Expression of TERRA in Different Grades of Astrocytoma

Brain tumors include burden of mortality from cancers. High grades of brain tumors are more aggressive and have poor prognosis. Introduction telomeres are the ends of linear chromosomes that serve as a protective cap to avoid permanent proliferation arrest, termed replicative senescence. In vertebrates, telomeres consist of tandem repeats of TTAGGG hexanucleotide sequences. In spite of heterochromatin structure of telomeres, they are transcribed into a non-coding RNA called telomeric repeat-containing RNA or TERRA which acts as a natural inhibitor of telomerase activity. Considering astrocytoma, as one of the most common tumors of the central nervous system (CNS), and a very poor prognosis tumor, the aim of this study was to evaluate the TERRA expression level in astrocytoma tumors and nontumoral controls. Furthermore, expression levels of TERRA were compared between different grades of astrocytoma. The mRNA of 26 brain tumor samples and 4 samples as nontumoral controls were extracted and cDNA was synthesized. Then, real-time reverse transcription polymerase chain reaction (SYBR Green kit) for quantitation of total TERRA levels was developed. We demonstrated the correlation between total TERRA levels of expression with different grades of astrocytoma. High grades (III and IV) of astrocytoma tumors had lower mean of ΔCt than low grades (II) and down-regulation for TERRA mRNA was 4.377-fold (P = 0.036). Additionally, measurement of TERRA expression in astrocytoma showed 4.969-fold less compared to levels of TERRA expression in nontumoral controls (P = 0.029). According to our study, TERRA may be prognostic marker in astrocytoma tumors.