Circadian regulation of MGMT expression and promoter methylation underlies daily rhythms in TMZ sensitivity in glioblastoma

Jan 26, 2024Journal of neuro-oncology

Daily rhythms in tumor sensitivity to chemotherapy linked to body clock control of MGMT gene activity and DNA modification in brain cancer

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Abstract

Morning administration of TMZ is associated with a 6-month increase in median survival for patients with MGMT-methylated glioblastoma.

GBM cells exhibit daily rhythms in the expression of key genes related to circadian timing and DNA repair.
GBM cells showed increased susceptibility to TMZ when treatment coincided with the peak expression of the Bmal1 gene.
In vivo studies demonstrated that morning TMZ administration reduced tumor size and increased body weight in mice with GBM.
Inhibition of MGMT activity altered the daily sensitivity patterns of GBM cells to TMZ, suggesting a timing-dependent effect.
Timing of biopsy for MGMT methylation status assessment should consider the time-of-day to ensure accurate results.

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BACKGROUND: Glioblastoma (GBM) is the most common primary brain tumor in adults. Despite extensive research and clinical trials, median survival post-treatment remains at 15 months. Thus, all opportunities to optimize current treatments and improve patient outcomes should be considered. A recent retrospective clinical study found that taking TMZ in the morning compared to the evening was associated with a 6-month increase in median survival in patients with MGMT-methylated GBM. Here, we hypothesized that TMZ efficacy depends on time-of-day and O-Methylguanine-DNA Methyltransferase (MGMT) activity in murine and human models of GBM. 6

METHODS AND RESULTS: In vitro recordings using real-time bioluminescence reporters revealed that GBM cells have intrinsic circadian rhythms in the expression of the core circadian clock genes Bmal1 and Per2, as well as in the DNA repair enzyme, MGMT. Independent measures of MGMT transcript levels and promoter methylation also showed daily rhythms intrinsic to GBM cells. These cells were more susceptible to TMZ when delivered at the daily peak of Bmal1 transcription. We found that in vivo morning administration of TMZ also decreased tumor size and increased body weight compared to evening drug delivery in mice bearing GBM xenografts. Finally, inhibition of MGMT activity with O-Benzylguanine abrogated the daily rhythm in sensitivity to TMZ in vitro by increasing sensitivity at both the peak and trough of Bmal1 expression. 6

CONCLUSION: We conclude that chemotherapy with TMZ can be dramatically enhanced by delivering at the daily maximum of tumor Bmal1 expression and minimum of MGMT activity and that scoring MGMT methylation status requires controlling for time of day of biopsy.

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Circadian regulation of MGMT expression and promoter methylation underlies daily rhythms in TMZ sensitivity in glioblastoma

Abstract

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