Knockdown of Checkpoint Kinase 1 Is Associated with the Increased Radiosensitivity of Glioblastoma Stem-Like Cells

Abstract

Glioblastoma multiforme is an aggressive brain tumor with a poor prognosis. The glioblastoma stem-like cells (GSCs) represent a rare fraction of human glioblastoma cells with the capacity for multi-lineage differentiation, self-renewal and exact recapitulation of the original tumor. Interestingly, GSCs are more radioresistant compared with other tumor cells. In addition, the remarkable radioresistance of GSCs has been known to promote radiotherapy failure and therefore is associated with a significantly higher risk of a local tumor recurrence. Moreover, the hyperactive cell cycle checkpoint kinase (Chk) 1 and 2 play a pivotal role in the DNA damage response including radiation and chemical therapy. Based on aforementioned, we hypothesized that knockdown of Chk1 or Chk2 might confer radiosensitivity on GSCs and thereby increases the efficiency of radiotherapy. In this study, we knocked down the expression of Chk1 or Chk2 in human GSCs using lentivirus-delivered short hairpin RNA (shRNA) to examine its effect on the radiosensitivity. After radiation, the apoptosis rate and the cell cycle of GSCs were measured with Flow Cytometry. Compared with control GSCs (apoptosis, 7.82 ± 0.38%; G2/M arrest, 60.20 ± 1.28%), Chk1 knockdown in GSCs increased the apoptosis rate (37.87 ± 0.32%) and decreased the degree of the G2/M arrest (22.37 ± 2.01%). In contrast, the radiosensitivity was not enhanced by Chk2 knockdown in GSCs. These results suggest that depletion of Chk1 may improve the radio-sensitivity of GSCs via inducing cell apoptosis. In summary, the therapy targeting Chk1 gene in the GSCs may be a novel way to treat glioblastoma.

The role of glioma stem cells in chemotherapy resistance and glioblastoma multiforme recurrence

“…Knockdown of Chk1 and Chk2 kinases with siRNA has proven effective in vitro in preventing cell cycle arrest and inducing apoptosis [99]. Checkpoint, ATM and other inhibitors are of avid interest in decreasing cell cycle arrest, promoting apoptosis after DNA damage from alkylating chemotherapy or radiation [100–103].…”

Radiation-induced G2/M arrest rarely occurred in glioblastoma stem-like cells

“…Bao et al (2006) have found that the proportion of survived CD133-positive GSLCs after radiation was increased relative to that of CD133-negative GDCs, and this finding was attributed to greater activation of checkpoints, such as ATM, Rad17, Chk1, and Chk2, in response to irradiation. Additionally, recent studies have shown that Chk1, but not Chk2, exerts dominant functions in the DNA damage repair of GSLCs after irradiation (Uto et al 2004;Wu et al 2012;Bo et al 2014).…”

Radiosensitization effect of hsa-miR-138-2-3p on human laryngeal cancer stem cells

“…Kobayashi et al (2014b) found that the removal of Brachyury that was related to cell proliferation, migration, invasion, radiation and chemotherapy resistance of Adenoid Cystic carcinoma CSCs could improve tumor stem cell radiation sensitivity. Wu et al (2012a) developed a model of CDK1 knock-out brain malignant glioma and found that CDK1 contributed to enhance radiosensitivity of CSCs by inducing cell apoptosis. Cell cycle checkpoint kinases (CDK1 and CDK2) play key roles in DNA damage response in radiation and chemotherapy.…”