Expression and clinical role of RBQ3 in gliomas.

RBQ3, also known as RBBP5 (RB-binding protein 5), was an RB-binding protein. Besides, it was one of core components of MLL1 (mixed lineage leukemia 1), which were required for H3K4 methyltransferase activity. MLL1 dysfunction was found to be associated with the progression of some cancers such as acute leukemias. However, the precise role of RBQ3 in tumor progression remains obscure. In this study, we explored the expression and clinical role of RBQ3 in gliomas. Our results showed that RBQ3 was significantly upregulated in clinical glioma specimens by Western blot and immunohistochemistry. Moreover, its level was significantly associated with the pathology grades. High RBQ3 expression was suggested to be an independent prognostic factor for glioma patients' survival by univariate and multivariate analyses. Serum starvation and refeeding assay indicated that the expression of RBQ3 increased 8h after serum-stimulation, together with percentage of cells at S phase. In addition, knockdown of RBQ inhibited U87-MG cell proliferation with CCK8 kit, flow cytometry assays and colony formation analyses; while the depletion of RBQ3 induced the apoptosis of U87-MG cells. All the findings suggested that RBQ3 might play an important role in glioma, and RBQ3 inhibitors might be novel anti-tumor agents.