Circulating miR-26a and miR-21 as biomarkers for glioblastoma multiform

Glioblastoma multiform is the most common and lethal primary central nervous system tumor. Circulating microRNAs (miRNAs), present in cell-free bodily fluids, have been gaining importance as cancer biomarkers. The primary aim of this study was to assess whether circulating miRNA-128, -21, and -26a in glioblastoma patients can be used as diagnostic biomarkers. Venous blood samples were collected from 11 noncancerous volunteers and 15 glioblastoma patients pre- and post operation. Also, tissue tumor samples were obtained intra-operationally to assay consistency of miRNA levels in serum and tissue samples. Serum and tissue levels of miRNAs were determined by quantitative reverse transcription PCR. miR-21 and miR-26a were both significantly upregulated in pre- and postoperation serum samples of glioblastoma patients compared with the serum samples of noncancerous controls. We found that all three miR-128, -21, and -26a expression levels were reduced in postoperative serum samples compared with pre-operative serum samples, though this decrease was only significant for miR-26a. The serum miR-26a and miR-21 upregulation in glioblastoma patients compared to noncancerous controls and their downregulation in postoperative serum from glioblastoma patients suggest that these miRNAs could be used as serum-derived miRNA biomarkers for glioblastoma.