Date of Graduation

Spring 5-18-2024

Document Type

Thesis

Degree Name

Master of Science in Biology

College/School

College of Arts and Sciences

Department/Program

Biology

First Advisor

Christina Tzagarakis-Foster

Second Advisor

Sangman Kim

Third Advisor

Jennifer Dever

Abstract

The orphan nuclear receptor DAX-1 (Dosage Sensitive Sex Reversal, Adrenal Hypoplasia Congenita, critical region on the X chromosome, gene 1) plays a key role in mammalian sex determination and steroidogenesis. In addition to these canonical examples, DAX-1 has been shown to play a contradictory role in cancer development. While DAX-1 is overexpressed in lung and prostate cancer, it is downregulated in breast cancer. One of the explanations for the paradoxical role of DAX-1 in cancer development could be microRNA (miRNA) dysregulation. After broadly surveying over 96 miRNAs historically upregulated in MCF7 breast cancer cells, we compared the expression of DAX-1 in MCF7 and MCF10A (normal breast epithelial) cells with the presence of specific miRNA inhibitors. Our primary hypothesis remains that multiple miRNAs negatively regulate the expression of DAX-1 in human breast cancer cells and are not overexpressed in normal breast cells, providing another mechanism of lifting the repression of DAX-1 expression. Quantitative PCR and western blot analysis was performed indicating that miRNA-29b, 100, 199a, and 424 all downregulate DAX-1 expression. Similar techniques were explored to determine that miR-20b and miR-22 inhibition downregulates Estrogen Receptor α expression whereas miR-29b, 29c, and 424 inhibition indicates Cyclin D1 underexpression. Finally, we examined the migratory properties of MCF7 cells following miRNA inhibition via scratch-and-heal assays. This research will allow clinicians to screen for miRNAs that are elevated in BC patients substantially increasing the number of people diagnosed with breast cancer early on, and it will provide another method for diagnosing breast cancer or those who do not have access to preventative care.

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