Puerarin inhibits proliferation and induces apoptosis in human glioblastoma cell lines.

Puerarin has been widely used in clinical treatment and experiment research and is considered to exert an anticancer effect recently. The present study investigated the anticancer activity of puerarin in U251 and U87 human glioblastoma cells. The cells were treated with puerarin at various concentrations for different times. Cell viability and cell proliferation were detected by cell counting kit-8 (CCK-8) assay and 5-ethynyl-2'-deoxyuridine (EdU) staining respectively. Cell cycle and apoptosis were measured separately with PI staining and Annexin V-FITC/PI double staining method by flow cytometry. DNA damage of glioblastoma cells caused by puerarin exposure was evaluated by γ-H2AX foci detection, and the expressions of p-AKT, caspase-3 and apoptosis-related proteins were detected by Western blotting after puerarin treatment. Cell viability and proliferation of glioblastoma cells treated with puerarin were significantly lower than that of the control group; the apoptosis rate increased obviously compared to the control group. Puerarin significantly decreased the proportion at G1 phase of cell cycling accompanied by increased populations at the S and G2/M phases in both cell lines. At the same time, DNA damage level of puerarin treated cells was significantly higher than that in the control cells. Moreover, puerarin treatment suppressed the expression of p-Akt and Bcl-2 and promoted the expression of Bax and cleaved caspase-3 in U251 cells. These findings indicate that puerarin exerts antitumor effects both in U251 and U87 cells.

LRIG1 enhances the radiosensitivity of radioresistant human glioblastoma U251 cells via attenuation of the EGFR/Akt signaling pathway.

The radiotherapy as a local and regional modality is widely applied in treatment of glioma, but most glioblastomas are commonly resistant to irradiation treatment. It remains challengeable to seek out efficient strategies to conquer the resistance of human glioblastoma cells to radiotherapy. Leucine-rich repeats and immunoglobulin-like domains protein 1 (LRIG1) is a newly discovered tumor suppressor which involved in regulation of chemosensitivity in various human cancer cells. In the present study, we established a radioresistant U251 cell line (U251R) to investigate the role of LRIG1 in regulation of radiosensitivity in human glioblastoma cells. Significantly decreased expression level of LRIG1 and enhanced expression of EGFR and phosphorylated Akt were detected in U251R cells compared with the parental U251 cells. U251R cells exhibited an advantage in colony formation ability, which accompanied by remarkably reduced X-ray-induced γ-H2AX foci formation and cell apoptosis. LRIG1 overexpression significantly inhibited the colony formation ability of U251R cells and obviously enhanced X-ray-inducedγ-H2AX foci formation and cell apoptosis. In addition, up-regulated expression of LRIG1 suppressed the expression level of EGFR and phosphorylated Akt protein. Our results demonstrated that LRIG1 expression was related to the radiosensitivity of human glioblastoma cells and may play an important role in the regulation of cellular radiosensitivity of human glioblastoma cells through the EGFR/Akt signaling pathway.

MicroRNA-19a promotes glioma cell growth by repressing LRIG1.

Growing evidence indicates that deregulation of miRNAs contributes to the development of glioma. In present study, we found that the level of miRNA-19a was significantly elevated in glioma tissues and cell lines. Moreover, down-regulation of miRNA-19a dramatically repressed glioma cell growth in vitro and in vivo. Meanwhile, the expression of LRIG1, a tumor suppressor in glioma, was increased following miRNA-19a knockdown. Furthermore, luciferase reporter assay confirmed that LRIG1 was a direct target of miRNA-19a. In addition, silencing of LRIG1 could reverse the suppressive effect of miRNA-19a inhibitor. Taken together, our results demonstrated that down-regulation of miRNA-19a could suppress the growth of glioma cells, at least in part, through up-regulating LRIG1.