Dataset Information

The DNA repair protein ALKBH2 mediates temozolomide resistance in human glioblastoma cells.

ABSTRACT:

Introduction

Glioblastoma multiforme (GBM; World Health Organization astrocytoma grade IV) is the most frequent and most malignant primary brain tumor in adults. Despite multimodal therapy, all such tumors practically recur during the course of therapy, causing a median survival of only 14.6 months in patients with newly diagnosed GBM. The present study was aimed at examining the expression of the DNA repair protein AlkB homolog 2 (ALKBH2) in human GBM and determining whether it could promote resistance to temozolomide chemotherapy.

Methods

ALKBH2 expression in GBM cell lines and in human GBM was determined by quantitative real-time PCR (qRT-PCR) and gene expression analysis, respectively. Drug sensitivity was assessed in GBM cells overexpressing ALKBH2 and in cells in which ALKBH2 expression was silenced by small-interfering (si)RNA. ALKBH2 expression following activation of the p53 pathway was examined by western blotting and qRT-PCR.

Results

ALKBH2 was abundantly expressed in established GBM cell lines and human GBM, and temozolomide exposure increased cellular ALKBH2 expression levels. Overexpression of ALKBH2 in the U87 and U251 GBM cell lines enhanced resistance to the methylating agents temozolomide and methyl methanesulfonate but not to the nonmethylating agent doxorubicin. Conversely, siRNA-mediated knockdown of ALKBH2 increased sensitivity of GBM cells to temozolomide and methyl methanesulfonate but not to doxorubicin or cisplatin. Nongenotoxic activation of the p53 pathway by the selective murine double minute 2 antagonist nutlin-3 caused a significant decrease in cellular ALKBH2 transcription levels.

Conclusion

Our findings identify ALKBH2 as a novel mediator of temozolomide resistance in human GBM cells. Furthermore, we place ALKBH2 into a new cellular context by showing its regulation by the p53 pathway.

SUBMITTER: Johannessen TC

PROVIDER: S-EPMC3578482 | biostudies-literature | 2013 Mar

REPOSITORIES: biostudies-literature

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Publications

The DNA repair protein ALKBH2 mediates temozolomide resistance in human glioblastoma cells.

Johannessen Tor-Christian Aase TC Prestegarden Lars L Grudic Amra A Hegi Monika E ME Tysnes Berit Bølge BB Bjerkvig Rolf R

Neuro-oncology 20121220 3

<h4>Introduction</h4>Glioblastoma multiforme (GBM; World Health Organization astrocytoma grade IV) is the most frequent and most malignant primary brain tumor in adults. Despite multimodal therapy, all such tumors practically recur during the course of therapy, causing a median survival of only 14.6 months in patients with newly diagnosed GBM. The present study was aimed at examining the expression of the DNA repair protein AlkB homolog 2 (ALKBH2) in human GBM and determining whether it could pr ...[more]

PMID: 23258843

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Project description:Glioblastoma (GBM) is the most common and aggressive primary brain tumor in adults and is universally fatal. The DNA alkylating agent temozolomide is part of the standard-of-care for GBM. However, these tumors eventually develop therapy-driven resistance and inevitably recur. While loss of mismatch repair (MMR) and re-expression of MGMT have been shown to underlie chemoresistance in a fraction of GBMs, resistance mechanisms operating in the remaining GBMs are not well understood. To better understand the molecular basis for therapy-driven temozolomide resistance, mice bearing orthotopic GBM xenografts were subjected to protracted temozolomide treatment, and cell lines were generated from the primary (untreated) and recurrent (temozolomide-treated) tumors. As expected, the cells derived from primary tumors were sensitive to temozolomide, whereas the cells from the recurrent tumors were significantly resistant to the drug. Importantly, the acquired resistance to temozolomide in the recurrent lines was not driven by re-expression of MGMT or loss of MMR but was due to accelerated repair of temozolomide-induced DNA double-strand breaks (DSB). Temozolomide induces DNA replication-associated DSBs that are primarily repaired by the homologous recombination (HR) pathway. Augmented HR appears to underpin temozolomide resistance in the recurrent lines, as these cells were cross-resistant to other agents that induced replication-associated DSBs, exhibited faster resolution of damage-induced Rad51 foci, and displayed higher levels of sister chromatid exchanges (SCE). Furthermore, in light of recent studies demonstrating that CDK1 and CDK2 promote HR, it was found that CDK1/2 inhibitors countered the heightened HR in recurrent tumors and sensitized these therapy-resistant tumor cells to temozolomide.ImplicationsAugmented HR repair is a novel mechanism underlying acquired temozolomide resistance in GBM, and this raises the possibility of improving the therapeutic response to temozolomide by targeting HR with small-molecule inhibitors of CDK1/2. Mol Cancer Res; 14(10); 928-40. ©2016 AACR.

Dataset Information

The DNA repair protein ALKBH2 mediates temozolomide resistance in human glioblastoma cells.

Introduction

Methods

Results

Conclusion

Publications

The DNA repair protein ALKBH2 mediates temozolomide resistance in human glioblastoma cells.

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