Down-regulation of MicroRNA-126 in glioblastoma and its correlation with patient prognosis: A pilot study

Glioblastoma is the most common primary malignant tumor of the adult human brain. Although microRNA-126 (miR-126) has been reported to exhibit expression abnormalities in various types of cancer, to date very few studies have examined changes in miR-126 level in glioblastoma. In this pilot study, we investigated the changes in miR-126 expression in newly-dissected primary glioblastoma to explore possible roles of miR-126 in patient prognosis. Total RNA was extracted from tumoral and adjacent non-cancerous tissues from 14 patients' paired frozen specimens. Using an established quantitative reverse transcriptase-PCR protocol, the levels of miR-126 in glioblastoma and adjacent non-tumor brain tissues were compared against small nucleolar RNA U48 (RNU48) as a reference gene. The expression of miR-126 in glioblastoma samples was significantly lower than in paired non-tumoral controls (p<0.05). Importantly, age-adjusted analyses suggest that glioblastoma patients with higher relative intratumoral miR-126 expression (i.e. 53-79% relative to that of the control tissue; n=7) had significantly improved survival duration than patients whose miR-126 levels were lower (i.e. 12-48%, n=7; stratified log-rank analysis p=0.011 when the dividing threshold was set at ≥51%; total: n=14, male: 8; female: 6). Thus, intraglioblastoma miR-126 may be down-regulated relative to normal tissue and patients with less downregulation of intratumoral miR-126 expression could have improved postsurgical prognosis. Future clinical studies with larger sample sizes should be performed to validate this observation.