Tumor microRNA-335 expression is associated with poor prognosis in human glioma

MicroRNA-335 (miR-335), as a transcript of genomic region chromosome 7q32.2, acts as a tumor suppressor or tumor promoter in various human malignancies. Especially, it has been reportedly shown to be an oncogene in human glioma cell line in vitro, but its expression in human glioma tissues is not yet determined. The aim of this study was to investigate the clinical significance of miR-335 expression in glioma. MiR-335 expression in human gliomas and nonneoplastic brain tissues was measured by real-time quantitative RT-PCR assay. The association of miR-335 expression with clinicopathological factors and prognosis of glioma patients was statistically analyzed. The expression level of miR-335 in glioma tissues was significantly higher than that in corresponding nonneoplastic brain tissues (P < 0.001). In addition, high miR-335 expression was significantly associated with a higher WHO grade (P = 0.001). Survival analysis demonstrated that patients with high miR-335 expression tumors had significantly shorter survival times than those with low miR-335 expression tumors (P = 0.01) and that miR-335 was an independent prognostic factor (P = 0.02). Especially, subgroup analyses according to tumor histologic grade revealed that the mean survival time of patients with high grade (III-IV) was significantly worse for high miR-335 expression group than for low miR-335 expression group (P = 0.002), but no significant difference was found for patients with WHO grade I-II (P = 0.16). These results indicated that miR-335 expression was increased in human gliomas and was associated with advanced tumor progression. Furthermore, miR-335 expression was demonstrated for the first time to be an independent marker for predicting the clinical outcome of patients with gliomas.