Date of Award

Fall 2019

Document Type

Open Access Thesis

Department

Chemistry and Biochemistry

First Advisor

Mythreye Karthikeyan

Abstract

Sex determining region Y-box 2 (Sox2) is a transcription factor essential for maintaining self-renewal and pluripotency of undifferentiated embryonic stem cells. Sox2 is involved in multiple processes of cancer cells, however, regulation of Sox2 expression and the consequences of that regulation in cancer remains elusive. Previously, we demonstrated that BMP9/GDF2 is significantly reduced in expression in ovarian cancer (OVCA) cells, methylated in patient tumors and, promoted anoikis resistance in both breast and OVCA cell lines. In an attempt to identify genes downstream of BMP9 that may provide anoikis resistance, transcriptomics was performed leading to the identification of Sox2, a developmental gene, as being significantly down regulated in response to BMP9. I find that Sox2 expression is broadly suppressed by BMP members including BMP2, BMP4 and BMP9 both in a time and dose dependent manner. To identify the specific ALK receptors utilized for Sox2 repression by BMPs, we used inhibitors to the ALK receptors and find specifically that ALK2 and ALK3 are receptors utilized by BMPs for Sox2 regulation. We also examined if Sox2 repression occurs via SMAD activation and find that SMAD1 activation is required for BMP-mediated Sox2 downregulation. This was validated via sh-RNA based approaches. Data from Sox2 promoter reporter assay suggests the involvement of the Sox2 promoter as the regulatory region involved in BMP-mediated downregulation, which was confirmed by expressing Sox2 from a heterologous CMV promoter which failed to be repressed by BMP. Furthermore, we find that de novo protein and RNA synthesis is required for BMP-mediated Sox2 repression as determined using cycloheximide and actinomycin D respectively. My findings indicate that BMP is a mediator of Sox2 downregulation in cancer, occurring via SMAD1-dependent mechanisms.

Rights

© 2019, Zainab Motolani Shonibare

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