All ETDs from UAB

Advisory Committee Chair

Anita B Hjelmeland

Advisory Committee Members

Victor Darley-Usmar

G Yancey Gillespie

Douglas Hurst

Ralph Sanderson

Christopher Willey

Document Type

Dissertation

Date of Award

2018

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Glioblastomas (GBMs) are the most common primary malignant brain tumors in adults and one of the most aggressive cancers with high rates of recurrence and therapeutic resistance. In GBMs, subpopulations of highly tumorigenic cells called brain tumor initiating cells (BTICs) have the unique capacity to promote tumor maintenance, therapeutic resistance, and angiogenesis. Depending on the level, differentiation state, and tumor stage, reactive nitrogen and oxygen species inhibit or increase cancer growth and BTIC maintenance. GTP cyclohydrolase 1 (GCH1) is the rate limiting enzyme in a pathway that can regulate reactive species production but has not been thoroughly investigated in GBM. We sought to define the role of GCH1 in the regulation of GBM growth and brain tumor initiating cell maintenance. We examined GCH1 mRNA and protein expression in patient-derived xenografts, clinical samples and glioma gene expression datasets. GCH1 levels were modulated using lentiviral expression systems, and effects on cell growth, self-renewal, reactive species production and survival in orthotopic patient derived xenograft models were determined. We also employed our HPAanalyze software to gain more insight into the GCH1 pathway. In the last decade, large-scale and collaborative omic projects have generated a massive amount of data, providing cancer researchers with a wealth of information that may help accelerate their research. The ability to easily, reliably and reproducibly access these data is fundamental for our ability to draw meaningful conclusions. We developed HPAanalyze, an R software package to retrieve, analyze and visualize data from the Human Protein Atlas program. GCH1 was expressed in GBMs with elevated RNA and protein levels in BTICs in comparison to non-BTICs. Overexpression of GCH1 in GBM cells increased cell growth in vitro and decreased survival in an intracranial GBM mouse model. In converse experiments, GCH1 knockdown with short hairpin RNA led to GBM cell growth inhibition and reduced self-renewal in association with decreased CD44 expression. GCH1 was critical for controlling hydrogen peroxide levels in cancer cells, which mediated GCH1 cell growth effects. In silico analyses found associations between higher GCH1 levels in glioma patients and higher glioma grade, recurrence and worse survival.

Share

COinS