Identification of Novel Therapeutic Approaches and Targets for the Treatment of Ovarian Carcinoma

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  • March 22, 2019
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  • Stevens, Ellen V.
    • Affiliation: School of Medicine, Department of Pharmacology
Abstract
  • The most imperative issues for ovarian carcinoma patients, due to high relapse rates against mainstay therapies, is to identify new molecular targets and develop novel therapeutics. This dissertation aims to address both of these issues by 1) defining the role, regulation and mechanism of Rho Guanine Nucleotide Dissociation Inhibitor 2 (RhoGDI2) in ovarian carcinoma and 2) testing nitric oxide (NO)-releasing nanoparticles as a potential targeted therapy for ovarian carcinoma. For the first part of my thesis, I demonstrated that RhoGDI2 protein expression is elevated in ovarian carcinoma cell lines and knockdown of RhoGDI2 in HeyA8 ovarian carcinoma cells results in increased Matrigel invasion and tail-vein lung metastasis of HeyA8 cells. RhoGDI2 associates primarily with Rac1 in HeyA8 cells and knockdown of RhoGDI2 decreases Rac1 activity and translocates Rac1 from the cytosol to membrane protrusions. Mechanistically, the phosphorylation of the MKK3/6/p38/JNK components of a key pathway downstream of Rac1, which is known to be important for ovarian cancer metastasis, decreased following RhoGDI2 knockdown in HeyA8 cells. My results suggest that RhoGDI2 overexpression contributes to the metastatic phenotype of ovarian carcinoma cells, although the exact mechanism responsible remains to be uncovered. For the second part of my thesis, I determined anti-tumor efficacy of NO-releasing silica nanoparticles against ovarian carcinoma cells. The NO-releasing nanoparticles display enhanced growth inhibition against ovarian tumor cells when compared to both control nanoparticles and a previously developed NO donor drug, PYRRO/NO. Confocal msicroscopy analysis revealed that fluorescently-labeled nanoparticles entered the cytosol of the cell, released NO, and localized to late endosomes and lysosomes. Additionally, we observed that nanoparticle efficacy against normal versus transformed ovarian cells depended on their size. Our study demonstrates the first application of nanoparticle-derived NO as an antitumor therapy. Collectively, my studies validated RhoGDI2 as a metastasis suppressor in ovarian carcinoma and supported the anti-tumor efficacy of nanoparticle delivery of NO.
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  • ... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Curriculum in Pharmacology
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  • Graves, Lee
  • Der, Channing
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