Glioblastoma (GBM) remains the most aggressive primary brain tumor in adults. Since 2005, Standard of Care (SoC) consists of surgical resection followed by radiation and adjuvant chemotherapy with temozolomide. Treatment failure is attributed to intratumoral heterogeneity with populations capable of mechanisms to repair damaged DNA. Given the lack of progress to improve patient outcomes, the current work encompasses how multi-omic approaches can be utilized to uncover novel biology in GBM and develop precision medicines to exploit these cancer specific phenomena.
Using patient derived GBM samples I first used the surface marker CD133 to interrogate glioblastoma stem cells, a subpopulation of cells identified to withstand conventional therapies and lead to tumor relapse. I used a genome-wide CRISPR-Cas9 library to conduct an unbiased loss-of-function phenotypic screen to identify regulators of CD133. I then validated SOX2 as a direct transcription factor to PROM1 encoding CD133. These findings further show the untapped potential of CRISPR to uncover novel biology to directly apply to broader fields of stem cells and cancer biology.
Next, I combed GBM data sets at transcriptomic and proteomic levels to identify understudied proteins as potential targets for immunotherapies. Glycoprotein nonmetastatic melanoma protein B (GPNMB) has previously been identified as a clinically relevant target in GBM and shown to be active in the tumor immune microenvironment. I found GPNMB to be upregulated in recurrent GBM and macrophage populations which can be exploited in a more comprehensive manner to treat GBM. Through a series of models, I elucidated how GPNMB influences GBM biology, its effectiveness as a target for Chimeric Antigen Receptor T-cells, and how it can be paired with CD133 therapies to provide better coverage of tumor cells. Together, these studies highlight how advances in pre-clinical models and technologies can be leveraged to develop new therapies in a rational manner. / Thesis / Doctor of Science (PhD) / Glioblastoma (GBM) remains an aggressive and incurable brain cancer despite decades of intense research. Treatment failure is due to the untargeted approaches currently undertaken in the clinic. The current work uses multiples methods to interrogate how GBM grows and develops over time. Using GBM samples from consenting patients, I investigated an important population of the tumor using a surface marker CD133 and CRISPR to study which genes influenced it. I then successfully validated SOX2 as a direct regulator of CD133 expression. Next, I combed multiple data sets for a target to kill GBM cells without harming healthy tissue in patients. I found Glycoprotein Non-Metastatic Melanoma Protein B (GPNMB) to be exploitable and used several experimental methods to investigate its role in GBM progression. Finally, we used a novel immunotherapy to eliminate cells which express GPNMB. Together, these findings could apply to the broader field of stem cell biology and be used for a more targeted method to eliminate the cancer entirely.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/28482 |
| Date | January 2023 |
| Creators | SAVAGE, NEIL |
| Contributors | SINGH, SHEILA, Biochemistry |
| Source Sets | McMaster University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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