Exosomal Survivin-T34A: A Novel, Potential Cancer Therapeutic

<p>Pancreatic cancer is the fourth most common cause of cancer fatality in American men and women with a less than 5% survival rate. Currently, if diagnosed early, surgical resection remains the only viable cure. However, only 20% of pancreatic cancer patients meet these criteria. It is therefore necessary to discover new therapies or therapeutic combinations in order to impact significantly this deadly disease. The anti-metabolite agent Gemcitabine is currently being employed to treat pancreatic cancer. While Gem-citabine has shown significant benefit in clinical applications, its ability to more than modestly impact pancreatic cancer is limited. It has been speculated that combinatory treatments using Gemcitabine could improve survival rates. Survivin, a member of the inhibitor of apoptosis (IAP) protein family, is expressed in virtually all cancer cells, but not detectable in most normal cells outside of development. Mutation of Survivin’s Thre-onine 34 to Alanine (Survivin-T34A) abolishes a phosphorylation site for p34cdc2-cyclin B1 resulting in the initiation of the mitochondrial apoptotic pathway in cancer cells with little to no direct effects on normal cells. The possibility that targeting Survivin in this manner may provide a novel approach for selective cancer gene therapy has yet to be ful-ly evaluated. We have recently described that cells generated to express a stable form of the mutant protein, released this Survivin-T34A to the conditioned medium. When this conditioned medium was collected and deposited on naive tumor cells, conditioned me-dium containing Survivin-T34A was as effective as chemotherapy in induction of tumor cell apoptosis. When combined with other forms of genotoxic stress, Survivin-T34A po-tentiated their killing effects. We further determined that Survivin-T34A is trafficked by microvesicles called exosomes, which are released into the conditioned media. We showed strong evidence that exosomes containing Survivin-T34A elicited cellular death and synergistically enhanced cellular death during combination with low doses of Gem-citabine and we propose that these findings may lead to novel modalities for cancer therapies. This dissertation provides the rational for Survivin-T34A’s potential as a thera-peutic. Next, we provide evidence that extracellular Survivin-T34A can elicit its anti-tumor effects on treated cells. Finally, I show that extracellular Survivin-T34A is found in exosomes.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Basic Sciences

Year

2014

Author dc:creator

• Aspe, Jonathan Richard

Contributors dc:contributor

• Wall, Nathan R.
• Casiano, Carlos A.
• Duerksen-Hughes, Penelope J.
• Langridge, William H. R.
• Pearce, William J.

• Biochemistry
• Biochemistry, Biophysics, and Structural Biology
• Medicine and Health Sciences
• Neoplasms - Drug Therapy; Anticarcinogenic Agents; Recombinant Proteins; Inhibitor of Apoptosis Proteing; Cell Line - Tumor; Tumor Cells - Cultured; Membrane Potential - Mitochondrial; Antibodies - Monoclonal; Exosomes; Enzyme-linked Immunosorbent Assay
• Survivin-T34A; Pancreatic Cancer; Cancer Fatality; Anti-metabolity Agent; Gemcitabine; Genotoxic Stress

Statement dc:rights

• This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Language dc:language

English

Repository record dc:identifier

https://scholarsrepository.llu.edu/etd/201

OAI identifier oai:identifier

oai:scholarsrepository.llu.edu:etd-1198