Abstract. MicroRNAs (miRNAs) are small, non-coding RNA molecules that regulate protein expression by cleaving or repressing the translation of target mRNAs. miR-125b, one of the neuronal miRNAs, was recently found to be necessary for stem cell fission and for making stem cells insensitive to chemotherapy signals. Temozolomide (TMZ) is a promising chemotherapeutic agent for treating glioblastomas. However, resistance develops quickly and with a high frequency. Given the insensitivity of some glioblastomas to TMZ and the hypothesis that glioma stem cells cause resistance to drug therapy, exploring the functions and mechanisms of miR-125b action on TMZ-treated glioblastoma stem cells would be valuable. In this study, we found that miR-125b-2 is overexpressed in glioblastoma multiforme tissues and the corresponding stem cells (GBMSC); downregulation of miR-125b-2 expression in GBMSC could allow TMZ to induce GBMSC apoptosis. Additionally, the expression of the anti-apoptotic protein Bcl-2 was decreased after the TMZ+miR-125b-2 inhibitor treatment, while the expression of the proapoptotic protein Bax was increased. Further research demonstrated that the induction of apoptosis in GBMSC is also associated with increased cytochrome c release from mitochondria, induction of Apaf-1, activation of caspase-3 and poly-ADP-ribose polymerase (PARP). Taken together, these results suggest that miR-125b-2 overexpression might confer glioblastoma stem cells resistance to TMZ.

BackgroundGlioblastoma can be classified into four distinct molecular subtypes (Proneural, Neural, Classical and Mesenchymal), based on gene expression profiling. This study aimed to investigate the prevalence, clinicopathologic features and overall survival (OS) of the four molecular subtypes among all malignant gliomas.MethodsA total of 941 gene expression arrays with clinical data were obtained from the Rembrandt, GSE16011 and CGGA datasets. Molecular subtypes were predicted with a prediction analysis of microarray.ResultsAmong 941 malignant gliomas, 32.73% were Proneural, 15.09% Neural, 19.77% Classical and 32.41% Mesenchymal. The Proneural and Neural subtypes occurred largely in low-grade gliomas, while the Classical and Mesenchymal subtypes were more frequent in high-grade gliomas. A survival analysis showed that the Proneural subtype displayed a good prognosis, Neural had an intermediate correlation with overall survival, Mesenchymal had a worse prognosis than Neural, and Classical had the worst clinical outcome. Furthermore, oligodendrocytomas were preferentially assigned to the Proneural subtype, while the Mesenchymal subtype included a higher percentage of astrocytomas, compared with oligodendrocytomas. Additionally, nearly all classical gliomas harbored EGFR amplifications. Classical anaplastic gliomas have similar clinical outcomes as their glioblastoma counterparts and should be treated more aggressively.ConclusionsMolecular subtypes exist stably in all histological malignant gliomas subtypes. This could be an important improvement to histological diagnoses for both prognosis evaluations and clinical outcome predictions.

Gossypin is a flavone that was originally isolated from Hibiscus vitifolius and has traditionally been used for the treatment of diabetes, jaundice, and inflammation. Recently, gossypin was found to have potent anticancer properties; however, its effect on human gliomas still remain unknown. To investigate the potential anticancer effects of gossypin on malignant gliomas and analyze the associated molecular mechanisms, we treated human glioma U251 cells with gossypin. Our study showed that the treatment of U251 cells with gossypin inhibited cell proliferation in a dose- and time-dependent manner and was observed to be minimally toxic to normal human astrocytes. Gossypin's effect on cell cycle distribution was observed, and we found that it induced G2/M-phase arrest in U251 cells. An analysis of cell-cycle regulatory proteins indicated that the arresting effect of gossypin on the cell cycle at G2/M phase was involved in the phosphorylation of cell division cycle 25C (Cdc25C) tyrosine phosphatase via the activation of checkpoint kinase 1 (Chk1). These findings indicate that gossypin is a potential treatment of gliomas because of gossypin's potential to regulate the proliferation of U251 cells via the cell-cycle regulatory proteins Chk1 and Cdc25C.