published_or_final_version / abstract / Pathology / Master / Master of Philosophy

This dissertation examines the production and management of genetic risk for breast and ovarian cancer in the United States in the new era of multi-gene panel testing. Drawing on three years of ethnographic fieldwork and in-depth interviews with genetics health professionals and women with mutations, this project is the first social science study to examine how breast and ovarian cancer genetic risk is constructed and managed among women with variants of uncertain significance or moderate-risk mutations. Moving beyond an individual-level focus on women’s risk management decisions, this project instead explores how the structures, practices, and organization of genetic medicine constrain and enable those decisions. There are four key findings from this study. First, the adoption of panel testing has shifted the boundaries of risk, disease, and patienthood and contributed to a spectrum of medicalization of breast and ovarian cancer risk. Women with high-risk breast and ovarian cancer mutations are now typically viewed and treated like full patients with a "disease," while women with moderate-risk mutations occupy a liminal space of qualified patienthood. Second, the structures and organization of genetic medicine in the United States point women with breast and ovarian cancer mutations toward risk-reducing mastectomy and breast reconstruction and encourage choosing those surgical responses over breast surveillance or staying flat. Mastectomy has become the standard “treatment” for the “disease” of genetic risk for breast cancer, regardless of whether women have high- or moderate-risk mutations and despite more conservative recommendations in clinical guidelines. Third, the structures of genetic medicine and the contemporary gender order in the United States are mutually constituted and co-produced. Breast reconstruction and gynecologic surgery practices both emerge from and reinforce gendered social and cultural norms that prioritize women's appearance and their reproductive capacity over their embodied experiences and daily quality of life. Finally, the discourses and practices of genetic medicine leave many women un- or under-prepared for the duration and severity of the side effects and consequences associated with breast reconstruction and risk-reducing salpingo-oophorectomy. By closely examining the social and structural dimensions of how cancer genetic risk is produced and managed in the United States, this project illuminates how clinical practices that magnify and focus on reducing certain risks simultaneously obscure and generate exposure to others.

[Truncated abstract] Ovarian cancer is currently the leading cause of death from gynaecological malignancies in women from developed countries. Serous ovarian cancer is the most prevalent type of all ovarian cancers, with the majority diagnosed in an advanced stage where treatment efficacy is reduced and patient survival is poor. Because of this fact, the development of improved detection and treatment strategies are necessary, with much research focussing on the complex molecular pathways involved in ovarian tumour growth as one potential avenue for intervention. Apoptosis, or programmed cell death, is one such area of investigation because currently successful cancer treatments induce apoptosis in tumour cells. Molecular analysis of apoptosis in both normal tissue and tumours has established a positive relationship between increased expression of secreted frizzled-related protein 4 (SFRP4) and apoptosis, however to date, very little research has focussed on the role of this gene in the ovary . . . An examination of SFRP4 and β-catenin expression in 163 primary serous ovarian carcinomas revealed high SFRP4 expression was associated with low β-catenin expression and conversely, low SFRP4 was associated with high β-catenin expression in the majority of the ovarian tumours analysed, reinforcing the inverse relationship observed in the ovarian cell lines. A positive trend was observed between cancer stage and the expression level of these proteins, with increased SFRP4 expression and reduced β-catenin expression as cancer stage increased. Additionally, patient survival revealed a trend towards increased survival among ovarian cancer patients who had tumours expressing low levels of SFRP4. Taken together, the novel findings of this study indicate that the increased expression of SFRP4 observed in a large proportion of serous ovarian cancers is a cellular response to down-regulate the level of β-catenin, and thus an attempt to maintain cellular homeostasis by counteracting the excessive proliferating signals present in these tumour cells.

Indiana University-Purdue University Indianapolis (IUPUI) / Ovarian cancer (OC) is a lethal disease due to metastasis and chemoresistance. Our laboratory previously reported that tissue transglutaminase (TG2) is overexpressed in OC and enhances OC peritoneal metastasis. TG2 is a multifunctional protein which catalyzes Ca2+-dependent cross-linking of proteins. The purpose of this study was to explore the mechanism by which TG2 is upregulated in OC and its role in OC progression. We demonstrated that transforming growth factor (TGF)-β1 is secreted in the OC milieu and regulates the expression and function of TG2 primarily through the canonical Smad signaling pathway. Increased TG2 expression level correlates with a mesenchymal phenotype of OC cells, suggesting that TGF-β1 induced TG2 promotes epithelial-to-mesenchymal transition (EMT). TG2 induces EMT by negatively regulating E-cadherin expression. TG2 modulates E-cadherin transcriptional suppressor Zeb1 expression by activating NF-κB complex, which leads to increased cell invasiveness in vitro and tumor metastasis in vivo. The N-terminal fibronectin (FN) binding domain of TG2 (tTG 1-140), lacking both enzymatic and GTPase function, induced EMT in OC cells, suggesting the interaction with FN involved in EMT induction. A TGF-β receptor kinase inhibitor, SD-208, blocked TGF-β1 induced TG2 upregulation and EMT in vitro and tumor dissemination in vivo, which confirms the link between TGF-β1 and TG2 in EMT and tumor metastasis. TG2 expression was correlated with the number and size of self-renewing spheroids, the percentage of CD44+CD117+ ovarian cancer stem cells (CSCs) and with the expression level of stem cell specific transcriptional factors Nanog, Oct3/4, and Sox2. These data suggest that TG2 is an important player in the homeostasis of ovarian CSCs, which are critical for OC peritoneal metastasis and chemoresistance. TG2 expression was also increased in CSCs isolated from human ovarian tumors, confirming the implication of TG2 in CSCs homeostasis. Further, we demonstrated that TG2 protects OC cells from cisplatin-induced apoptosis by regulating NF-κB activity. We proposed a model whereby TGF-β-inducible TG2 modulates EMT, metastasis, CSC homeostasis and chemoresistance in OC. These findings contribute to a better understanding of the mechanisms of OC metastasis modulated by TG2.

Indiana University-Purdue University Indianapolis (IUPUI) / Telomere maintenance is a critical component of genomic stability. An increasing body of evidence suggests BRCA1, a tumor suppressor gene with a variety of functions including DNA repair and cell cycle regulation, plays a role in telomere maintenance. Mutations in BRCA1 account for approximately half of all hereditary breast and ovarian cancers, and the gene is silenced via promoter methylation and loss of heterozygosity in a proportion of sporadic breast and ovarian cancers. The objective of this study was to determine whether GRN163L, a telomerase inhibitor, currently in clinical trials for the treatment of cancer, has enhanced anti-cancer activity in BRCA1 mutant breast/ovarian cancer cell lines compared to wild-type cancer cells. BRCA1 mutant cancer cells were observed to have shorter telomeres and increased sensitivity to telomerase inhibition, compared to cell lines with wild-type BRCA1. Importantly, GRN163L treatment was synergistic with DNA-damaging drugs, suggesting potential synthetic lethality of the BRCA1 cancer subtype and telomerase inhibition In a related study to examine the roles of BRCA1/2 in telomere maintenance, DNA and RNA extracted from peripheral blood were used to investigate the age-adjusted telomere lengths and telomere-related gene expression profiles of BRCA1 and BRCA2 individuals compared to individuals who developed sporadic cancer and healthy controls. BRCA1 mutation carriers and breast cancer patients showed the shortest average telomere lengths compared to the other groups. In addition, distinct genomic profiles of BRCA mutation carriers were obtained regarding overexpression of telomere-related genes compared to individuals who developed sporadic or familial breast cancer. In summary, telomerase inhibition may be a viable treatment option in BRCA1 mutant breast or ovarian cancers. These data also provides insights into further investigations on the role of BRCA1 in the biology underlying telomere dysfunction in cancer development.