Date of Award

Spring 2017

Degree Type

Thesis

Degree Name

MS Biology

Department

Biology

Advisor

Jane L. Ko, PhD

Committee Member

Daniel Nichols, PhD

Committee Member

Heping Zhou, PhD

Committee Member

Agela V. Klaus, Ph.D

Keywords

Hypoxia, Cobalt, MOR, STAT3

Abstract

Hypoxia is a frequent characteristic of the solid tumor microenvironment, which occurs when cancer cells lack adequate access to oxygen. By selecting for cells that can adapt to and grow in low oxygen conditions, tumor hypoxia contributes to a more aggressive and invasive cancer phenotype that portends a poor clinical outcome. While many aspects of the cellular response to hypoxia have been explored, the roles of some factors have not been fully explained. Cell signaling factors, including signal transducer and activator of transcription 3 (STAT3), the mu opioid receptor (MOR), and the delta opioid receptor (DOR), as well as changes in the mitochondrial membrane potential may play a role in cancer cell adaptation to hypoxia. Importantly, the hypoxia-related actions of STAT3 and the human opioid receptors have not been thoroughly researched within the context of human neuronal cancer cells. To investigate the roles of these proteins in hypoxic adaptation, we developed and tested a model of chemically induced hypoxia using neuronal cells. We administered the hypoxia mimetic, cobalt chloride, to a human neuroblastoma cell line. The preliminary data of flow cytometry suggested that cobalt- induced hypoxia increased the total amount of STAT3 in neuroblastoma cells, but decreased the amount of phosphorylated STAT3 in a time dependent pattern. The preliminary results using JC- 1 staining with confocal microscopy indicated that cobalt exposure did not change mitochondrial membrane potential in surviving cells. RT-PCR (reverse transcription) analysis showed a decrease in MOR expression and no change in DOR expression. This decrease in expression lends support to an inhibitory role of MOR in neuronal adaptation to hypoxia. These results also implicated that survival of neuronal cells under cobalt treatment likely are independent of STAT3 tyrosine phosphorylation. Taken together this study provides a baseline for future use of this model to investigate hypoxia.

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