Unlike many other cancers, the prognosis for gliomas has not improved over recent decades.A new approach to tackle brain tumours is needed. In this thesis, I investigated the biological basis for important clinical problems in neuro-oncology, such as malignant progression and glioma-related seizures, using
ex vivo human brain tissue. I show that
ex vivo glioma cells can be detected in brain tissue fragments and blocks of brain tissue donated by people undergoing brain surgery. Living cells metabolize 5-aminolevulinic acid into Protoporphyrin IX (PpIX). Malignant glioma cells accumulate PpIX, which makes them fluorescent. Glioma infiltration in
ex vivo ultrasonic tissue fragments can be identified rapidly by imaging PpIX fluorescence.I used this screening method to capture intratumoural heterogeneity of gliomas. For example,I found that the methylation of the promoter of the O6-methylguanine-DNA methyltransferase (MGMT) gene, which encodes a DNA repair enzyme, varied within gliomas. Next, I sectioned blocks of
ex vivo human brain tissue into 300 – 500 µm slices.These slices preserved the architecture of the glioma and the adjacent healthy brain (peritumoural cortex). In ex vivo brain slices from lower grade gliomas, I observed clusters of cells that exhibited 5-ALA induced PpIX fluorescence. I refer to these clusters of cells asPpIX hotspots. I found that PpIX hotspots contain ‘putative’ nestin-positive glioma cells and endothelial cells. Hence, PpIX hotspots may harbour the potential for malignant progression.Lastly, I made local field potential recordings of brain activity across the glioma and peritumoural cortex in the
ex vivo brain slices. I recorded spontaneous “seizure-like”discharges. Analysis of the electrical discharges revealed that they could be subdivided into distinct types based on the major frequencies in the discharge. Higher frequency activity in these discharges inversely correlated to the degree of glioma infiltration. My findings suggest that
ex vivo human brain tissue has the potential to unravel the underlying mechanisms of malignant progression, and tumour-associated seizures
Mechanisms of malignant progression and tumour associated seizures in
ex vivo human brain tissue
Kirby, A. (Author). 1 Apr 2021
Student thesis: Doctoral Thesis › Doctor of Philosophy