Loan Thuy Bui

Graduation Semester and Year

2017

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Biomedical Engineering

Department

Bioengineering

First Advisor

Young-Tae Kim

Abstract

There are more than 120 types of primary brain and central nervous system tumors that affect people of all ages. Glioblastoma multiforme (GBM), for example, is the most frequent type of brain cancers and also among the deadliest of all cancers due to its high invasiveness and resistance to radiation and chemotherapy. Recently, most genetic mutations of malignant brain tumors have been well characterized, but the focus on migrating cancers that directly cause invasion is still in its infancy. We have learned from the literature that most glioma cells infiltrate surrounding brain tissue via by the confined tracks, and fascinated by the current microfluidic technology that can create confined microchannels. Therefore, this research was conducted to investigate uncovered migration properties of malignant brain tumor cells in physical confinement. Those include changes in biomolecular expression of aggressive migrating cells and the relationship of different mutations and migratory capacity, cellular viability, and drug resistance. Different tumor-related cell lines were used in this research: primary GBM and neuroblastoma, human brain cancer D54 and D54-EGFRvIII, and genetically modified mouse astrocytes p53−/−, p53−/− PTEN−/−, p53−/− Braf, and p53−/− PTEN−/− Braf. In the migration study, using microfluidic devices that provided physical confinements ranging from 3 × 5 μm2 to 20 × 5 μm2 in cross sections, cells with EGFRvIII and Braf mutation were found to exhibit high degree of migratory capacity in narrow confinement (3 × 5 μm2 and 5 × 5 μm2), for the first time. In the viability study, loss of PTEN combined with Braf activation (p53−/− PTEN−/− Braf) resulted in higher viability in narrow confinement (5 × 5 μm2) compared to the other mutated astrocytes. In addition, Braf conferred increased resistance to the microtubule-stabilizing drug, Paclitaxel, in narrow confinement. Similarly, survival of D54-EGFRvIII cells was unaffected following treatment with drug, whereas the viability of D54 cells was reduced significantly by 75%. The high chemo-resistance was also recognized in primary human GBM cells. Our results also suggested potential therapeutic targets based on genotypes, migratory capacity, and their specific survival phenotypes during migration through confinement. In fact, Doxorubicin and AZD-6244 were suggested to provide cytotoxic effect and migration inhibition on these aberrant cells, respectively. In the last but not least study, aggressive brain cancer cells, G55, migrating through microchannels were directly accessed and used for subsequent molecular analysis. The study was based on the developed microfluidic platform that facilitated the recruitment of a high number of migrating cells while preventing contamination of two-dimensional (2D) culture cells. As the results, migrating cells were found with increased Vimentin yet decreased β3-Tubulin and Met signal. As more difference in biomarker expression between migrating cells and 2D culture cells will be revealed, more unknown underlined features of cancer invasion or metastasis can be elucidated. The successful outcome of this research would provide improved targets for ceasing brain cancer.

Keywords

Brain tumor, Biomarkers, Microchannels, Physical confinement, Invasion, Genetic mutation, Migration, Drug resistance

Disciplines

Biomedical Engineering and Bioengineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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