ORCID

http://orcid.org/0000-0003-3283-3958

Date of Award

Winter 12-15-2022

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Neurosciences)

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Glioblastoma (GBM) is the most common primary adult brain tumor diagnosed, with a 15-month prognosis using current standard of care treatment which includes chemotherapy with temozolomide (Temodar, TMZ). Chronotherapy, the practice of considering time of day in treating a disease, has been shown to improve outcome in several cancers, but had not been applied to GBM. Previous work in the lab on a cultured murine mesenchymal GBM cell line showed a time-of-day dependent maximum in sensitivity to TMZ corresponding with the daily peak of Bmal1 and trough of Per2 expression, two core clock genes. Based on this finding, we sought to understand the circadian biology of GBM tumors in vivo and the potential for timed TMZ treatment to extend survival in both mice and humans. In mice, we used orthotopic implants of GBM cell lines, Nf1-/- DNp53 mes-GBM (murine), GL261 (murine), and LN229 (human), to study tumor growth, circadian gene expression, and response to TMZ treatment. We found that cell lines formed tumors that entrained to the host, remained synchronized to mouse activity patterns through a 12h light shift, and consistently showed peak Bmal1:luc at ZT0-4 and peak Per2:luc at ZT17-19 across cell lines. We also found that TMZ treatment (70 mg/kg) at ZT1 or ZT11 suppressed tumor growth equally, without differences in survival time or tumor size reduction. In humans, we conducted a retrospective chart study of patients with newly diagnosed GBM at Washington University School of Medicine who had surgery, chemoradiation, and were prescribed TMZ to be taken in the morning or evening. We found superiority of morning TMZ at years one, two, and five with a three-month extension of overall survival in all patients and a six-month extension in the subset of patients having MGMT promoter methylation. Complementing this study, we conducted a prospective clinical trial (NCT02781792) to determine the feasibility and clinical impact of TMZ chronotherapy in patients with gliomas. We found that patients were 98% compliant with their prescribed dosing time and that dose time did not affect adverse event frequency or grade. Together, these studies support prescribing TMZ in the morning to extend survival without increasing side effects. A subset of patients in the prospective study wore wrist actimeters to track sleep habits throughout treatment and tumor bearing mice were housed with running wheels to monitor actigraphy. We aimed to identify differences in actigraphy that correlated with disease progression, beginning with variability in predicted dim light melatonin onset (DLMO) in humans and average weekly activity counts in mice. Preliminary results show that increased variability in DLMO in humans and decreased average activity counts in mice correlate with disease progression. The experiments described in this dissertation form the foundation for future experiments investigating the importance of dose in time of day sensitivity to TMZ, identifying new drug targets involved in tumor synchrony to the host, and validating improved mechanisms for tumor diagnosis and monitoring.

Language

English (en)

Chair and Committee

Erik D. Herzog

Committee Members

Erin M. Gibson, Albert H. Kim, Joshua B. Rubin, Paul H. Taghert,

Download

Share

COinS