Breast cancer is a complex heterogenous disease that consists of several different subtypes displaying distinct behaviors and responses to different treatments. It is the second leading cause of cancer death among women, and is the most commonly diagnosed cancer in women. Although recent developments have helped shed light into this disease, there is still much to investigate. One particular subtype of breast cancer, known as triple-negative breast cancer, remains the most aggressive, as this tumor type is of high histological grade and preferentially affects women with BRCA1 mutations and women who are younger than 40 years of age. Unlike other subtypes with better prognoses, triple-negative breast cancer still has no targeted therapy, and chemotherapy remains the primary systemic treatment. Recently, there has been an increase of interest in the SOXC family of high mobility group transcription factors and their roles in tumor development. Studies have revealed some of the effects that SOXC genes may have on various tumor types. However, further studies are still needed to elucidate the roles, functions, regulations, and mechanisms of these transcription factors. This study aims to focus on one particular gene in the SOXC family known as sex determining region Y-box 11. Recent studies have shown that sex determining region Y-box 11, also known as SOX11, is one of the factors required for maintaining the basal-like breast cancer phenotype and is also critical in regulating growth, migration, invasion, and expression of signature basal-like breast cancer genes. Emerging evidence also reveals that this transcription factor may have an impact on homologous recombination repair when DNA damage occurs, in triple-negative breast cancer. Using SOX11 overexpression and knockout cell models combined with basic science laboratory techniques and omics, the next generation of laboratory tools, this study seeks to explore the role and function of SOX11 in DNA damage in triple-negative breast cancer. The results of this study have confirmed the recent findings of the role of SOX11 in cell proliferation and growth in triple-negative breast cancer. It has also revealed that overexpression of SOX11 in triple-negative breast cancer cell lines leads to an increase in DNA damage, loss of BRCA1 function, and dysregulation in the cell cycle. High expression of SOX11 is also associated with worse prognostic outcomes in triple-negative breast cancer patients. Because overexpression of SOX11 resulted in a loss of BRCA1 function, there may be a potential role for SOX11 in inducing the BRCAness phenotype commonly seen in basal-like breast cancers. The results of this study strongly suggest that SOX11 is involved in defective DNA damage repair pathways. Further studies need to be conducted in order to evaluate SOX11 as an inducer of the BRCAness phenotype, which occurs when there is a homologous recombination repair defect and no germline BRCA1 mutation present. Because of this, SOX11 may also have the potential to act as a functional biomarker for therapies targeting DNA damage, as recent developments in identifying therapies that could potentially target homologous recombination repair defects have been promising.

Inflammatory Breast Cancer (IBC) is a rare, lethal, and understudied form of breast cancer. Although affecting 1-2% of the population, the remission rate is half that of the spectrum of other breast cancers, and most cases present in the advanced stages due to rapid undetectable development. Of the diagnosed cases, systemic chemotherapeutics are relatively ineffective in comparison to non-IBC breast cancer cases, indicating other unique mechanisms driving IBC progression. Historically, the specific sensitivities of a particular tumor type or subtype have been linked to genetic alterations that represent addiction hubs, such as hyperactivation of oncogenes due to mutation. Although some efforts have been made to characterize the molecular fingerprint of inflammatory breast cancers (IBCs), unfortunately, no clinical application has emerged from these studies. Thus, we decided to utilize a different strategy to identify the Achilles' heel of IBC cells. Using shRNA libraries, we performed an unbiased genome-wide loss-of-function screen comparing the gene functions required for survival of IBC and non-IBC cells. Histone deacetylase 6 (HDAC6) emerged as one of the top genes required for IBC cell survival and was further validated. HDAC6 is vital in the cell's unfolded protein response (UPR) to clear misfolded or toxic protein, and IBC cells proved to be preferentially sensitive to this aspect of HDAC6 inhibition, displaying increased protein accumulation, ER stress indicators, and subsequent apoptosis upon failure to clear or refold accumulated proteins. These data indicate HDAC6 is a crucial gene required for IBC cell line survival, in part due to its function in IBC cell UPR. Furthermore, emerging orally bioavailable agents for HDAC6 inhibition make it a promising candidate towards tailored therapeutic implementation in IBC patient trials.

No description available.

Although there are hereditary risk factors strongly associated with breast cancer, only a small percentage of breast tumors can be attributed to these. Instead, it is believed that 85-90% of breast cancers are primarily of environmental origin. Polycylic aryl hydrocarbons (PAHs) are environmental carcinogens derived from combustion including fossil fuels. PAHs bind to a cellular aryl hydrocarbon receptor (AhR) that mediates downstream events leading to cellular transformation. Previous work in our laboratory used the prototypical PAH 7,12-dimethylbenz[a]anthracene (DMBA) to form tumors in mouse mammary glands that had constitutive AhR activation, increased Wnt signaling, and strong induction of the CK2 subunit CK2α (Currier, Solomon et al. 2005). Wnt, an important developmental pathway, is implicated in several cancers (Dominguez, Sonenshein et al. 2009). CK2 is a highly promiscuous, constitutively active serine/threonine kinase that is over-expressed in every cancer that has been examined for its presence (Meggio and Pinna 2003). Data from the DMBA-induced mouse tumors demonstrated that these factors may be involved in carcinogen-induced breast cancer, but their role in tumor development is uncertain. The hypothesis underlying this project was that CK2 and the Wnt pathway would be involved in early changes in mouse mammary and liver tissues in animals exposed to DMBA. We used qPCR, Western blotting, and immunohistochemistry to look at changes in Wnt pathway components and known Wnt-dependent genes, and CK2 subunits in mammary and liver tissues one and two weeks after DMBA exposure. Liver tissue was analyzed along with mammary gland tissue because the liver is the site of DMBA metabolism. Our results showed no change in liver or mammary gland morphology at these time points. There was induction of the AhR gene targets cyp1a1 and cyp1b1 in liver tissue but not in mammary gland. Liver also had evidence of Wnt pathway activation. Mammary glands did not have a strong AhR response but did show Wnt induction at two weeks post-exposure, suggesting that DMBA was affecting the liver before the mammary glands. CK2α had an unexpected early decrease in protein expression at one week in liver, which at two weeks resolved to the same levels as control tissue. In mammary glands, CK2α expression levels were the same as control at one week and decreased at two weeks, again suggesting a slower response than liver. Interestingly, CK2β was markedly overexpressed in mammary glands at the two week time-point. These results suggest there is a role for both Wnt and CK2 in early DMBA-generated tissue changes. It is still unclear if these pathways are separately affected by DMBA or if one initiates the other. Further experimentation, possibly in cell culture using inhibitors and siRNA, are called for to better understand these findings.

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Pathology / Master / Master of Medical Sciences

No description available.

No description available.

No description available.