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Epigenetic preconditioning with decitabine sensitizes glioblastoma to temozolomide via induction of MLH1.


ABSTRACT: INTRODUCTION:To improve the standard treatment paradigm for glioblastoma (GBM), efforts have been made to explore the efficacy of epigenetic agents as chemosensitizers. Recent data suggest possible synergy between decitabine (DAC), a DNA hypomethylating agent, and temozolomide (TMZ) in GBM, but the mechanism remains unclear. The objective of this study was to determine the effects of DAC on TMZ sensitization in a consecutively derived set of primary GBM cultures, with a focus on mismatch repair (MMR) proteins. METHODS:Half maximal inhibitory concentrations (IC50) of TMZ were calculated in eleven consecutive patient-derived GBM cell lines before and after preconditioning with DAC. MMR protein expression changes were determined by quantitative immunoblots and qPCR arrays. Single-molecule real-time (SMRT) sequencing of bisulfite (BS)-converted PCR amplicons of the MLH1 promoter was performed to determine methylation status. RESULTS:TMZ IC50 significantly changed in 6 of 11 GBM lines of varying MGMT promoter methylation status in response to DAC preconditioning. Knockdown of MLH1 after preconditioning reversed TMZ sensitization. SMRT-BS sequencing of the MLH1 promoter region revealed higher levels of baseline methylation at proximal CpGs in desensitized lines compared to sensitized lines. CONCLUSIONS:DAC enhances TMZ cytotoxicity in a subset of GBM cell lines, comprising lines both MGMT methylated and unmethylated tumors. This effect may be driven by levels of MLH1 via E2F1 transcription factor binding. Using unbiased long-range next-generation bisulfite-sequencing, we identified a region of the proximal MLH1 promoter with differential methylation patterns that has potential utility as a clinical biomarker for TMZ sensitization.

SUBMITTER: Gallitto M 

PROVIDER: S-EPMC7256087 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Epigenetic preconditioning with decitabine sensitizes glioblastoma to temozolomide via induction of MLH1.

Gallitto Matthew M   Cheng He Rossana R   Inocencio Julio F JF   Wang Huaien H   Zhang Yizhou Y   Deikus Gintaras G   Wasserman Isaac I   Strahl Maya M   Smith Melissa M   Sebra Robert R   Yong Raymund L RL  

Journal of neuro-oncology 20200319 3


<h4>Introduction</h4>To improve the standard treatment paradigm for glioblastoma (GBM), efforts have been made to explore the efficacy of epigenetic agents as chemosensitizers. Recent data suggest possible synergy between decitabine (DAC), a DNA hypomethylating agent, and temozolomide (TMZ) in GBM, but the mechanism remains unclear. The objective of this study was to determine the effects of DAC on TMZ sensitization in a consecutively derived set of primary GBM cultures, with a focus on mismatch  ...[more]

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