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Multicellular Tumor Spheroids as a Model to Study Tumor Cell Adaptations within a Hypoxic Environment

Riffle, Stephen
http://orcid.org/0000-0002-5947-242X
http://rave.ohiolink.edu/etdc/view?acc_num=ucin151188562556805

Abstract Details

2017, PhD, University of Cincinnati, Medicine: Molecular and Developmental Biology.
Hypoxia is a common feature in solid tumors which facilitates the development of therapeutically resistant and aggressive tumor phenotypes. As oxygen levels decrease, cellular metabolism and energy production becomes impaired and the potential for catastrophic DNA damage increases. To prevent cell death, tumor cells undergo several adaptations which prevent depletion of nutrients, minimize DNA damage, and re-acquire blood flow. The mechanisms behind tumor cell survival during hypoxia are poorly understood. Tumor neovascularization is a critical step in facilitating continued tumor growth. Accordingly anti- angiogenic therapy has shown significant success in preventing progression free survival however increased tumor aggression and alternative neovascularization methods result in decreased overall patient survival. Vasculogenic mimicry is one such proposed method of alternative neovascularization wherein tumor cells transdifferentiate and form de novo vascular structures. Although there are indications that this process is driven by hypoxia and is linked to aggressive tumor phenotypes, there is little known about the signaling pathways inducing such an adaptation. Evidence from in vitro studies suggest that activation of DNA damage repair proteins in proliferating hypoxic cells is critical for sustained proliferation and cell viability thus implicating repair proteins as potential therapeutic targets. In vivo studies demonstrating a correlation between hypoxia and the formation of γ-H2AX further support this potential. The evaluation of such therapeutic targets is limited by the inability of in vitro monolayer culture models to recreate therapeutically relevant aspects of a 3D in vivo tumor. Multicellular tumor spheroids (MCTS) represent a 3D in vitro culture model in which tumor cell adaptations to the hypoxic tumor microenvironment are recreated. These include the accumulation of metabolic waste, appearance of nutrient gradients, and development of proliferative heterogeneity. MCTS have been used extensively to characterize radiation resistance in a hypoxic environment.We set out to describe the relationship between proliferation, hypoxia, DNA damage repair, and vasculogenic mimicry using the MCTS model. Using MCTS, we demonstrate for the first time the activation of DNA damage repair proteins in hypoxic proliferating cells residing within the MCTS core and further show the ability to study the efficacy of therapeutics targeting this cell population. Although metabolic adaptations and DNA damage repair protein activation are observed in this model, MCTS formed using the liquid overlay method do not experience vasculogenic mimicry. The results presented herein advances the field of tumor biology by validating the utility of MCTS as a model system in which clinically relevant features of a tumor can be recreated and studied. Furthermore our studies identify the Eyes Absent tyrosine phosphatase as a therapeutic target whose activity regulates DNA damage repair under both normoxic and hypoxic conditions and may be involved in vasculogenic mimicry.
Rashmi Hegde, Ph.D. (Committee Chair)
Zelia Correa, M.D. Ph.D. (Committee Member)
Richard Lang, Ph.D. (Committee Member)
Qing Richard Lu, Ph.D. (Committee Member)
Kathryn Wikenheiser-Brokamp, M.D. Ph.D. (Committee Member)
141 p.
Cellular Biology
Multicellular Tumor Spheroids; DNA damage repair; Eyes Absent; Hypoxia; Cancer; Ewing Sarcoma

Recommended Citations

Citations

  • Riffle, S. (2017). Multicellular Tumor Spheroids as a Model to Study Tumor Cell Adaptations within a Hypoxic Environment [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin151188562556805

    APA Style (7th edition)

  • Riffle, Stephen. Multicellular Tumor Spheroids as a Model to Study Tumor Cell Adaptations within a Hypoxic Environment. 2017. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin151188562556805.

    MLA Style (8th edition)

  • Riffle, Stephen. "Multicellular Tumor Spheroids as a Model to Study Tumor Cell Adaptations within a Hypoxic Environment." Doctoral dissertation, University of Cincinnati, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin151188562556805

    Chicago Manual of Style (17th edition)

ucin151188562556805
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© 2017, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.