Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Biochemistry

Supervisor

Dr. Bonnie Deroo

Abstract

The extracellular matrix (ECM) is a highly organized, dynamic structure that maintains tissue integrity and regulates biological processes involved in organ development and function. To explore the role of ECM proteins in ovarian physiology and pathology, my thesis characterizes ECM proteins aberrantly overexpressed in the Estrogen Receptor (ER)β-null (βERKO) mouse ovary and epithelial ovarian cancer (EOC). The ECM undergoes extensive physical changes, and influences numerous cell functions, throughout folliculogenesis. This study identifies a role for ERβ in ovarian development earlier than previously believed. Nidogen 2 and Collagen 11a1 are aberrantly overexpressed in βERKO ovaries as early as postnatal day 13, and this dysregulation continues into adulthood, as determined by qPCR and immunofluorescence. Collagen IV, Nidogen 1 and Laminin are also more highly expressed in the βERKO ovary than in the wildtype ovary, suggesting that the repression of several ECM proteins in the ovary is ERβ-dependent. The molecular mechanisms that initiate gene repression by ERβ are not well understood; therefore a potential mechanism by which ERβ may act as a transcriptional repressor in the ovary is investigated. I characterized a novel ERβ transcriptional corepressor – transcription factor 21 (TCF21). In transient transfection and reporter assays, TCF21 represses ERβ transactivation of synthetic and natural estrogen-responsive promoters in various cell lines. As in the βERKO ovary, when the mechanisms regulating ECM dynamics during normal organ function are disrupted, the ECM becomes disorganized. This disorganization is associated with various pathologies, including cancers. The ECM protein, Spondin 1 (SPON1), is overexpressed in ovarian cancers and has been identified as a promising ovarian cancer marker, particularly for high-grade serous carcinomas; yet, its cellular functions and related mechanisms in EOC progression remain unknown. This study shows that SPON1 is expressed and secreted by immortalized EOC cell lines and human primary ascites-derived EOC cells. Treatment with exogenous SPON1 reduces EOC cell adhesion, viability and proliferation but not migration. Experiments utilizing a non-adherent culture surface suggest SPON1 does not effect EOC spheroid formation but is involved in spheroid anchoring and cell dispersion. These findings support an important role for ECM proteins in ovarian development and progression of ovarian carcinomas.

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