Cell Cycle Changes after Glioblastoma Stem Cell Irradiation: The Major Role of RAD51 (original) (raw)
Related papers
A radiosensitizing effect of RAD51 inhibition in glioblastoma stem-like cells
BMC Cancer, 2016
Background: Radioresistant glioblastoma stem cells (GSCs) contribute to tumor recurrence and identification of the molecular targets involved in radioresistance mechanisms is likely to enhance therapeutic efficacy. This study analyzed the DNA damage response following ionizing radiation (IR) in 10 GSC lines derived from patients. Methods: DNA damage was quantified by Comet assay and DNA repair effectors were assessed by Low Density Array. The effect of RAD51 inhibitor, RI-1, was evaluated by comet and annexin V assays. Results: While all GSC lines displayed efficient DNA repair machinery following ionizing radiation, our results demonstrated heterogeneous responses within two distinct groups showing different intrinsic radioresistance, up to 4Gy for group 1 and up to 8Gy for group 2. Radioresistant cell group 2 (comprising 5 out of 10 GSCs) showed significantly higher RAD51 expression after IR. In these cells, inhibition of RAD51 prevented DNA repair up to 180 min after IR and induced apoptosis. In addition, RAD51 protein expression in glioblastoma seems to be associated with poor progression-free survival. Conclusion: These results underscore the importance of RAD51 in radioresistance of GSCs. RAD51 inhibition could be a therapeutic strategy helping to treat a significant number of glioblastoma, in combination with radiotherapy.
Molecular Cancer Therapeutics, 2012
Glioblastoma multiforme (GBM) is the most common form of brain tumor with a poor prognosis and resistance to radiotherapy. Recent evidence suggests that glioma-initiating cells play a central role in radioresistance through DNA damage checkpoint activation and enhanced DNA repair. To investigate this in more detail, we compared the DNA damage response in nontumor forming neural progenitor cells (NPC) and glioma-initiating cells isolated from GBM patient specimens. As observed for GBM tumors, initial characterization showed that gliomainitiating cells have long-term self-renewal capacity. They express markers identical to NPCs and have the ability to form tumors in an animal model. In addition, these cells are radioresistant to varying degrees, which could not be explained by enhanced nonhomologous end joining (NHEJ). Indeed, NHEJ in glioma-initiating cells was equivalent, or in some cases reduced, as compared with NPCs. However, there was evidence for more efficient homologous recombination repair in glioma-initiating cells. We did not observe a prolonged cell cycle nor enhanced basal activation of checkpoint proteins as reported previously. Rather, cell-cycle defects in the G 1 -S and S-phase checkpoints were observed by determining entry into S-phase and radioresistant DNA synthesis following irradiation. These data suggest that homologous recombination and cell-cycle checkpoint abnormalities may contribute to the radioresistance of glioma-initiating cells and that both processes may be suitable targets for therapy.
Comparative Analysis of DNA Repair in Stem and Nonstem Glioma Cell Cultures
Molecular Cancer Research, 2009
It has been reported that cancer stem cells may contribute to glioma radioresistance through preferential activation of the DNA damage checkpoint response and an increase in DNA repair capacity. We have examined DNA repair in five stem and nonstem glioma cell lines. The population doubling time was significantly increased in stem compared with nonstem cells, and enhanced activation of Chk1 and Chk2 kinases was observed in untreated CD133 + compared with CD133 À cells. Neither DNA base excision or single-strand break repair nor resolution of pH2AX nuclear foci were increased in CD133 + compared with CD133 À cells. We conclude that glioma stem cells display elongated cell cycle and enhanced basal activation of checkpoint proteins that might contribute to their radioresistance, whereas enhanced DNA repair is not a common feature of these cells. (Mol Cancer Res
Journal of Radiation Research, 2007
Glioblastoma/High LET Charged Particle/p53/G2 block/Apoptosis. This study was conducted in order to evaluate the cytotoxicity of high linear-energy-transfer (LET) ionizing radiation (IR) on glioblastoma cells and fibroblasts using different modes of cell inactivation assays. Two human glioblastoma cell lines with or without p53-mutation, and fibroblasts were used as materials. Gamma rays and 290 MeV/u carbon beams with LET values of 20, 40, 80 keV/μm were used. To evaluate cell inactivation, we used colony formation assay, morphological detection of apoptosis, and flow-cytometry. Serial expressions of p53 and p21 were analyzed by immunoblotting. High-LET IR reduced the reproductive potency of these cells to identical levels in spite of differences in gammasensitivity, and yield of cell death correlated to LET values. A p53-wild-type glioblastoma cell line demonstrated a higher yield of apoptosis than other cell lines, whereas fibroblasts hardly displayed any cell death indicating senescence-like growth arrest even after high LET IR. A p53-mutant tumor cell line demonstrated very low yield of cell death with prominent G2/M arrest. Results of radiosensitivity differ according to what mode of cell inactivation is selected. While fibroblasts depend on G1 block after IR, G2/M blocks may play crucial roles in the radioresistance of p53-mutant glioblastoma cells.
Glioblastoma Stem Cells: Radiobiological Response to Ionising Radiations of Different Qualities
Radiation Protection Dosimetry, 2015
Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumor, with very poor prognosis. The high recurrence rate and failure of conventional treatments are expected to be related to the presence of radio-resistant cancer stem cells (CSCs) inside the tumor mass. CSCs can both self-renew and differentiate into the heterogeneous lineages of cancer cells. Recent evidence showed a higher effectiveness of C-ions and protons in inactivating CSCs, suggesting a potential advantage of Hadrontherapy compared to conventional radiotherapy for GBM treatment. In order to investigate the mechanisms involved in the molecular and cellular response of CSCs to ionising radiations, we irradiated two GBM stem cell (GSC) lines, named line # 1 and line # 83, derived from patients with different clinical outcome and having different metabolic profiles (as shown by NMR spectroscopy), with 137 Cs photons and with protons or C-ions of 62 MeV/u in the dose range 5-40 Gy. The biological effects investigated were: cell death, cell cycle progression, and DNA damage induction and repair. Preliminary results show a different response to ionising radiation between the two GSC lines for the different end points investigated. Further experiments are in progress to consolidate the data and to get more insights on the influence of radiation quality.
Cancer Letters, 2017
The role of histone deacetylase (HDAC) 4 and 6 in glioblastoma (GBM) radioresistance was investigated. We found that tumor samples from 31 GBM patients, who underwent temozolomide and radiotherapy combined treatment, showed HDAC4 and HDAC6 expression in 93.5% and 96.7% of cases, respectively. Retrospective clinical data analysis demonstrated that high-intensity HDAC4 and/or HDAC6 immunostaining was predictive of poor clinical outcome. In vitro experiments revealed that short hairpin RNA-mediated silencing of HDAC4 or HDAC6 radiosensitized U87MG and U251MG GBM cell lines by promoting DNA double-strand break (DSBs) accumulation and by affecting DSBs repair molecular machinery. We found that HDAC6 knock-down predisposes to radiation therapy-induced U251MG apoptosis-and U87MG autophagy-mediated cell death. HDAC4 silencing promoted radiation therapy-induced senescence, independently by the cellular context. Finally, we showed that p53 WT expression contributed to the radiotherapy lethal effects and that HDAC4 or HDAC6 sustained GBM stem-like radioresistant phenotype. Altogether, these observations suggest that HDAC4 and HDAC6 are guardians of irradiation-induced DNA damages and stemness, thus promoting radioresistance, and may represent potential prognostic markers and therapeutic targets in GBM.
Frontiers in Oncology, 2020
Glioblastoma is among the most common malignant brain tumors and has a dismal prognosis due to the poor response to therapeutic regimens such as ionizing radiation and DNA-alkylating agents. In our study, we investigated the radiosensitizing activity of the N 6-isopentenyladenosine (iPA), an naturally modified adenosine harboring an isopenenyl moiety, which shows antiproliferative effects on glioblastoma cell lines. We observed that co-treatment with ionizing radiation and iPA at micromolar concentration inhibited colony formation and viability of glioblastoma cell lines but not of non-malignant human cells. The combined treatment significantly attenuated the repair of radiation-induced DNA damage by inhibiting both the expression and irradiation-induced foci formation of RAD51, a key player in the homologous recombination repair process, leading to persistent DNA damage, as reflected by an increase of γ-H2AX foci. The radiosensitizing effect relied also on the inhibition of STAT5a/b activation, which is crucial for RAD51 expression, suggesting that iPA modulates the STAT5a/b-RAD51 axis following exposure to ionizing radiation. Overall, these data suggest that iPA, by acting through RAD51 inhibition at the mechanistic level, could function as a promising radiosensitizing agent and warrants further evaluation in prospective clinical trials.
DNA damage response and repair: insights into strategies for radiation sensitization of gliomas
Future oncology (London, England), 2011
The incorporation of radiotherapy into multimodality treatment plans has led to significant improvements in glioma patient survival. However, local recurrence from glioma resistance to ionizing radiation remains a therapeutic challenge. The tumoricidal effect of radiation therapy is largely attributed to the induction of dsDNA breaks (DSBs). In the past decade, there have been tremendous strides in understanding the molecular mechanisms underlying DSB repair. The identification of gene products required for DSB repair has provided novel therapeutic targets. Recent studies revealed that many US FDA-approved cancer agents inhibit DSB repair by interacting with repair proteins. This article will aim to provide discussion of DSB repair mechanisms to provide molecular targets for radiation sensitization of gliomas and a discussion of FDA-approved cancer therapies that modulate DSB repair to highlight opportunities for combination therapy with radiotherapy for glioma therapy.
Molecular biology of the cell cycle: Potential for therapeutic applications in radiation oncology
Seminars in Radiation Oncology, 1996
The cell cycle was first described by radiation biologists more than 40 years ago. Since then, radiation oncologists have used information regarding the cell cycle, in particular cell cycle kinetics, to design various treatment protocols; these have resulted in only modest improvements in patient outcome. Over the past 10 to 15 years there has been an explosion of scientific knowledge regarding the cell cycle, in particular the molecular regulation of the cell cycle checkpoints. In this review we will discuss the genetic events involved in regulating the G1 and G2 checkpoints and how this information may lead to future therapeutic breakthroughs. In addition we will discuss the potential clinic~r! impact of the recent cloning of the gene for ataxia telangiectasia.