Date of Award

5-2010

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Biology

Thesis Sponsor/Dissertation Chair/Project Chair

Reginald Halaby

Committee Member

Kirsten Monsen-Collar

Committee Member

Carlos Molina

Abstract

Cancer is the second leading cause of death in the United States, and with the rates of breast cancer increasing steadily over time there is a need to develop new anticancer treatments. This research seeks to investigate how triptolide, an extract from the Chinese herb Tripterygium wilfordii Hook F, induces apoptosis in human breast cancer cells. Studies have shown that triptolide can act as an anti-proliferative, antiinflammatory, and anti-cancer agent in many different clinical applications. It has been used for over two centuries in Chinese medicine and is now used to treat certain autoimmune diseases, such as rheumatoid arthritis. With breast cancer plaguing the United States as the second leading cause of cancer related deaths amongst women, as well as the adverse effects of current treatment methods, there is a need for the development of safer and alternative therapies. Triptolide is known to induce apoptosis in many cancer cells lines, but the exact mechanisms that regulate this are largely unknown. It has been suggested that triptolide activates the p53 pathway to trigger apoptosis in these cells. However, our results demonstrate that other cellular mechanics are at work in conjunction with p53, such as the differential regulation of pro- and anti-apoptotic proteins; lysosomal degradation; and a change in mitochondrial membrane permeability suggesting the release of cytochrome c.

Our studies examined the ability of triptolide to regulate the protein expression levels of caspase-3, caspase-7, and caspase-9, poly (ADP-riobse) polymerase (PARP), and Bcl-2 via colorimetric Western blot analysis. Apoptosis was monitored using the MTT cell viability assay and morphological observations. LysoTracker™ and MitoTracker™ were used to stain lysosmes and mitochondria, respectively. An acid phosphatase, a marker enzyme for lysosomes, assay was conducted in order to measure the activity of lysosomal enzymes. Our results demonstrated that the amount of apoptosis, which was significantly increased by triptolide, was both time- and dosedependent, suggesting that there may be an optimal triptolide concentration for maximal anticancer efficacy. Triptolide also differentially regulated the expression of pro- and anti-apoptotic proteins. Furthermore, the apoptotic death of cells was shown to be a lysosomal-mediated cell death. Future investigations will try to decipher the molecular mechanisms by which triptolide regulates apoptosis in vivo using an MCF-7 xenograft model in nude mice.

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