Therefore, clinical factors alone are not sufficient to evaluate the prognoses of glioma patients, and further research is needed to search for better prognostic biomarkers. However, studies have shown that biological alterations in specific genes or molecules can affect the prognosis of glioma patients 7, 8. Some clinical factors impact the prognosis of glioma patients, such as age at diagnosis, WHO grade, duration of symptoms, tumor size, postoperative treatment, and karnofsky performance score (KPS) 7, 8. Although recent progress has been made in surgical and radiotherapy techniques, the prognoses of GBM patients have not significantly improved 4, 5, and GBM remains one of the most incurable cancers 6, with a 5-year survival rate of only 5.1% 3. Grade IV glioma, known as glioblastoma multiforme (GBM), is extremely aggressive, and comprises 55.1% of all gliomas 3. Low-grade gliomas (LGG, grades IвЂ“II) are well-differentiated and grow slowly, while high-grade gliomas (HGG, grades IIIвЂ“IV) are characterized by poor differentiation and rapid progression, and the prognosis of HGG is usually poor. According to the World Health Organization (WHO) classification, gliomas are classified as grade I through grade IV 2. Gliomas are one of the most common central nervous system (CNS) glial neoplasms, accounting for 30% of all CNS tumors and 80% of malignant brain tumors 1, respectively. Our findings suggest that higher expression of miR-21 is correlated with poorer glioma prognosis. A multivariate Cox regression analysis of the miR-21 expression in the TCGA glioma dataset revealed that overexpression of miR-21 was a potential independent prognostic biomarker of poorer OS (HRвЂ‰=вЂ‰1.27, 95% CI: 1.01, 1.59) and poorer PFS (HRвЂ‰=вЂ‰1.46, 95% CI: 1.17, 1.82). Among them, eight studies provided data on overall survival (OS) with a pooled HR of 1.91 (95% CI: 1.34, 2.73), indicating that higher expression of miR-21 was significantly associated with worse OS in glioma patients for the other study, which provided data on progression-free survival (PFS), no statistically significant HR was reported for PFS in the glioma patients (HRвЂ‰=вЂ‰1.23, 95% CI: 0.41, 3.72). Nine studies were included in the meta-analysis. We further used multivariate Cox regression analysis to assess miR-21 expression in the TCGA glioma dataset to validate the relationship between miR-21 expression and survival. Pooled hazard ratios (HRs) with 95% confidence intervals (CIs) were used to describe association strength.

Relevant data were extracted to assess the correlation between miR-21 expression and survival in glioma patients. In this study, we searched Embase, PubMed, Web of science, CNKI, SinoMed, and Wanfang databases for records up to May 2018. We performed a comprehensive study based upon a meta-analysis and The Cancer Genome Atlas (TCGA) glioma dataset validation to clarify the prognostic significance of miR-21 in glioma patients. However, the role of miR-21 in predicting prognosis remains controversial. Recent studies have highlighted the value of microRNA-21 (miR-21) as a prognostic biomarker in gliomas.

Comprehensive meta analysis 3