<p>Bmi1 is a member of the Polycomb Group proteins and has been demonstrated as being vital in stem cell regulation. Bmi1 is overexpressed in many cancers, including glioblastoma, and has been shown to regulate cancer cell self-renewal and proliferation both <em>in vitro</em> and <em>in vivo</em>. This study aimed to determine if Bmi1 modulates brain tumour initiating cell properties using a spontaneous primary glioblastoma cell line and a commercial glioblastoma cell line. To determine the role of Bmi1 in glioblastoma cells, stem cell assays and <em>in vivo</em> analysis of tumour formation was performed on both control cells and Bmi1 knockdown cells. In both cell lines, Bmi1 was found to play a positive regulatory role in stem cell properties. When Bmi1 was knocked down in brain tumour initiating cells, properties such as self-renewal, proliferation and tumour formation were impaired compared to control cells. This study supports recent literature which shows that Bmi1 regulates stem cell properties in glioblastoma cells and supports the potential use of Bmi1 as a therapeutic target in glioblastoma brain tumours.<strong><br /> </strong></p> / Master of Science (MSc)