Numerous three-dimensional model systems have emerged for emulating the biochemical and physiological states of native tissue. Yet little is known about the effects of mechanical forces on cell behavior in the context of an organized tissue structure in three-dimensional cell-culture. Epithelial cells cultured in a three-dimensional environment comprised of extracellular matrix proteins form spheroids of polarized cells. Cellular responses to mechanical cues, generated from dynamic interactions with the extracellular matrix and neighboring cells, are known to influence cellular behavior to a great extent. Previous studies have shown that tumorigenic progression has been frequently linked to the down regulation of E-cadherin, a cell-cell adhesion protein. This work proposes that E-cadherin plays a pivotal role in maintaining epithelial tissue integrity and homeostasis. Novel FRET-based biosensors were used to measure force across E-cadherin. First, I observed that 3D acini had significantly higher force than 2D monolayers. Next, I determined that low-force mutant phenotypes of E-cadherin resulted in impaired lumen formation. In order to examine the effects of E-cadherin force on the disruption of homeostasis, TGF-b was used to induce epithelial to mesenchymal transition (EMT). TGF-b resulted in a decrease in E-cadherin force, even at early time points prior to transcriptional changes. Forskolin, a known regulator of acini lumen size, was shown to increase E-cadherin force. Furthermore, forskolin was able to prevent TGF-b disruptions in acini homeostasis. Finally, I examined how changes in substrate stiffness, known to affect acini lumen structure, altered E-cadherin forces. Stiffer substrates (mediated by collagen doping of Matrigel) delivered higher E-cadherin forces while simultaneously including acinar luminal filling. It is possible that signaling through non-junction forces, due to changes in ECM proteins, may mediate loss of the lumen. Thus, the major conclusion of these studies is that higher E-cadherin force is required for the formation and maintenance of a single central lumen in epithelial acini. Lower junctional forces induced acinar luminal filling, possibly through disruption in the polarity and subsequent cellular reorganization. This work, thus, establishes the role of E-cadherin as a key regulator of tissue homeostasis.

The development and advancement of prostate cancer is supported by a plethora of genetic and proteomic abnormalities, including events of post-translational modifications. The protein arginine methyltransferase 5 (PRMT5) enzyme regulates epigenetic events of histone modifications and protein post-translational modifications within protein signaling pathways. PRMT5 functions by catalyzing the symmetric dimethylation of terminal arginine residues on target protein substrates. Under abnormal conditions of overexpression and upregulation, PRMT5 methyltransferase activity constitutively drives the growth and proliferation of dysregulated cells. Overexpression or upregulation of PRMT5 correlates with disease progression as observed among numerous cancer types, including breast, colorectal, leukemia, lung, melanoma and prostate cancers. We demonstrated previously that PRMT5 knockdowns attenuated both growth and proliferation of lung and prostatic tumors, in vitro and in vivo. Plants naturally produce chemical toxins as mechanisms of defense against microbial and other biological threats. Human exploitation, consumption and application of agents isolated from plants for therapeutic intervention dates back throughout the millennia. In this study, we extracted, purified and evaluated natural, small, chemical compounds from plant products that antagonize PRMT5 activity in prostate cancer cells. We found that crude and purified extracts of Dendrobium aurantiacum var. denneanum (D. denneanum) plants attenuated prostate tumor growth and proliferation by selective inhibition of PRMT5 methyltransferase activity. These findings establish the first set of natural PRMT5-specific inhibitors reported.

ATP-Binding-Cassette (ABC) transporters are primary active pumps that typically couple the binding and hydrolysis of ATP to the translocation of compounds across cellular membranes. Some, like ABCB1, ABCC1 and ABCC3, are polyspecific and can efflux clinically important drugs which may contribute to their therapeutic failure. In this study I have investigated (1) the mechanism of ABC transporter function, (2) studied the potential for regulation by ubiquitin ligases (both using ABCB1 as a model), and (3) tested the involvement of ABCC1 and ABCC3 in autocrine signalling in cancer. (1) In 1966, Jardetzky et. al [1] proposed that membrane pumps function by exposing their ligand-binding pocket alternately on different sides of the membrane. For ABC transporters, this coupling of the aspect and affinity of the ligand-binding cavities of the two transmembrane domains (TMDs) to the ATP catalytic cycle of the two nucleotide-binding domains (NBDs) is fundamental to the transport mechanism but is poorly understood at the molecular level. Structure data suggest signals are transduced through intracellular loops of the TMDs which slot into grooves on the top surface of the NBDs. At the base of these grooves is the Q-loop. By analysing the function of Q-loop mutants in combination with ligand binding cavity mutants I have discovered that the Q-loops are crucial to the transport cycle and that they are required to couple ligand binding to conformational changes at the NBDs necessary to drive the transporter into an inward closed state. 4 (2) ABCB1 is known to be a key component of chemical barrier separating the circulation from the cerebrospinal fluid. It has also been reported to transport β-amyloid across the lumenal membrane and into the circulation. Loss of ABCB1 from the barrier with age has therefore been suggested to play a role in Alzheimer’s Disease. The ubiquitin ligase Nedd4-1 has been implicated in the post-translational regulation of ABCB1 abundance in cells. Here, I report that ABCB1 can be ubiquitinated by Nedd4-1 in vitro and identify the residues modified (by mass spectrometry). (3) Lysophosphatidylinositol (LPI) is an autocrine metabolite produced by cancer cells that binds to the G-protein coupled transmembrane receptor GPR55 on the surface of cells. Stimulation of GPR55 activates a signalling cascade that induces proliferation and metastases of the cancer cells. How LPI is released from the cells was not known. In this study I show that ABCC1 and ABCC3, which are known to be expressed in ovarian and pancreatic cancers, can transport LPI into inside-out vesicles suggesting a new role for these “drug resistance” transporters in cancer biology.

It is estimated that nearly 50,000 individuals in the United States will be diagnosed with head and neck cancer in 2017 (American Cancer Society www.cancer.org). Ninety percent of oral cancers are head and neck squamous cell carcinoma (HNSCC). Major obstacles in the treatment of HNSCC are recurrence and treatment resistance, which contributes to increased mortality. Therefore, there is increased need to determine genetic alterations in HNSCC that may be ideal novel drug targets, and biomarkers to improve diagnostic and prognostic testing. Abnormal localization and overexpression of base excision repair protein and transcriptional regulator Apurinic/Apyrimidic endonuclease (APE1) has been associated with treatment resistance and poor prognosis. Therefore, we explored mechanisms for how APE1 contributes to treatment resistance and increased mortality in HNSCC. Because oxidative stress heavily influences APE1’s expression and transcriptional regulatory activities, we examined genes involved in oxidative stress management, including SOD3 and NRF2. PPARGC1A, a NRF2 transcriptional co-activator, was also examined as our lab previously observed a link between APE1 and PPARGC1A expression. This previous work also revealed that APE1 suppressed gene expression of tumor suppressor, decorin (DCN). To examine possible mechanisms for how APE1 regulates expression of tumor suppressors and antioxidants, digital image analysis of immunohistochemistry staining was used to identify alterations in protein expression. Nuclear and total cellular protein expression of APE1, DCN, NRF2, PPARGC1A, and SOD3 were quantified in regions of proximal benign, carcinoma in situ (CIS) and invasive HNSCC. Patient survival analysis revealed that increased APE1, DCN, and PPARGC1A protein levels were significantly associated with reduced survival in CIS, benign, and invasive tissues respectively. Using multivariate analysis of protein expression, we identified that increased APE1 protein levels in the CIS of primary tumors were associated with the presence of cancer invaded lymph nodes. Elevated DCN and SOD3 protein levels in benign tissue were associated with poorly differentiated tumors as was reduced PPARGC1A in CIS. Most importantly, potential prognostic biomarkers for use in early cancer development were identified. Identifying poor prognosis in early cancer development allows the possibility of improved treatment strategies, which could prevent invasive cancer development, and increase patient survival.

The dissertation consists of three major projects with the focus on the immunotoxicity of chromium and the behavior disorders caused by early ETOH exposure respectively. Hexavalent chromium [Cr(VI)] is widely used in various industrial processes and has been recognized as a carcinogen. As the first line of host defense system, the immune system can be a primary target of Cr(VI). T cell population represents a major arm of the immune system that plays a critical role in host anti-tumor immunity. Dysfunction of T cells compromises host anti-tumor immunity resulting in oncogenesis. Using mouse splenic T cells as an in vitro model system, the present study assessed the effects of Cr(VI) on T cell functions, as the first step of our investigation of the mechanism underlying Cr(VI)-inhibited immunosurveillance and carcinogenesis. Our results showed that Cr(VI) decreased the viability of CD4+ and CD8+ T cells, inhibited T cell activation, functions, including cytokine release, and degranulation. Fetal ethanol (ETOH) exposure can damage the developing central nervous system and lead to cognitive and behavioral deficits, known as fetal alcohol spectrum disorders (FASD). The use of animal models, especially mouse models is essential for investigating the neurogenetic mechanism of fetal ETOH effects and screening pharmacotherapies against it, due to the extensive knowledge of mouse genetics. However, the availability of mouse model is limited. Via adopting various dosage, timing and administration routes of ETOH exposure, we developed two mouse models to assess behavioral or cognitive changes caused by fetal ETOH exposure in pre-weaning and adolescent period. Our results show that high dosage of ETOH exposure (4 g/kg) during PD 4-10 resulted in hyperactivity, disinhibition, and deficits in learning and memory in mouse offspring, which lays the groundwork for the future FASD research.

Ovarian cancer is the fifth leading cause of cancer death in women between the ages of 35 and 74. With 22 thousand new cases and 15 thousand deaths annually ovarian cancer is among the most deadly cancers with a death to incidence ratio of 68%. With 70% of cases High Grade Serous Ovarian Carcinoma (HGSOC) is the most common type of ovarian cancer and causes 90% of ovarian cancer deaths. 80% of patients have reoccurrence within five years and only 15-30% of patients with recurrent metastatic ovarian cancer respond to current therapies, chemotherapy and surgery. One reason for the high reoccurrence rate is thought to be linked to the heterogeneity of tumors: there is evidence that, among tumor cells, a subpopulation is cancer stem cells (CSCs). Since CSCs are frequently drug resistant, when the patient undergoes chemotherapy many of the cells may die but the CSCs are left behind and the tumors can therefore regrow. CSCs are also more likely to undergo epithelial-mesenchymal transition which gives these cells the ability to more readily migrate and invade through the extracellular matrix, leaving the primary tumor to form metastases. One key inducer of EMT and therefore possibly of metastasis of particular interest in this project is SNAI1 (Snail). It is therefore the goal of this project to understand the growth, makeup and metastatic ability of HGSOC cell lines to test possible strategies to decrease growth of cancer and prevent metastasis. In this thesis project the phenotype, CSC population make up, and functionality of various HGSOC cell lines was examined. The cell lines assessed were A2780, Kuramochi, OVSAHO, COV318, SKOV3 and OVCAR8. A Snail knockdown OVCAR8 cell line was also assessed as described above and in a xenograft model. It was determined that the cell lines show varying phenotype from epithelial like to mesenchymal like morphology and the cell lines have varying concentrations of cancer stem cells. It was also determined that the CSC population of the HGSOC cell lines were positive for both epithelial and mesenchymal markers in the same cells. OVCAR8 stood out as a hybrid line with both epithelial and mesenchymal characteristics and was therefore chosen for the Snail knockdown model. In the Snail knockdown we observed that CSC markers were reduced, however no change between control and knockdown was seen in the in vitro functional experiments. There was a difference seen between Snail knockdown and control in the in vivo mouse xenograft model. Snail knockdown showed a trend for decreasing tumor burden in both primary and metastatic tumors and showed a significant decrease in growth of metastatic tumor at day 43. Based on these results Snail may be an important target for cancer therapy.

Our laboratory delineated a role for alternative pre-mRNA splicing (AS) in triple negative breast cancer (TNBC). We found the translational regulator cytosolic polyadenylation element binding protein 2 (CPEB2) which has two isoforms, CPEB2A and CPEB2B, is alternatively spliced during acquisition of anoikis resistance (AnR) and metastasis. The splicing event which determines the CPEB2 isoform is via inclusion/ exclusion of exon four in the mature mRNA transcript. The loss of CPEB2A with a concomitant increase in CPEB2B is required for TNBC cells to metastasize in vivo. We examined RNAseq profiles of TNBC cells which had CPEB2 isoforms specifically downregulated to examine the mechanism by which CPEB2 isoforms mediate opposing effects on cancer-related phenotypes. Downregulation of the CPEB2B isoform inhibited pathways driving the epithelial-to-mesenchymal transition (EMT) and hypoxic response, whereas downregulation of the CPEB2A isoform did not have this effect. Specifically, CPEB2B functioned as a translational activator of TWIST1 and HIF1a. Functional studies showed that specific downregulation of either HIF1α or TWIST1 inhibited the ability of CPEB2B to induce AnR and drive metastasis. The mechanism governing inclusion/ exclusion of exon 4 was determined to be serine/ arginine-rich splicing factor 3 (SRSF3). Binding of SRSF3 to a consensus sequence within CPEB2 exon 4 promoted its inclusion in the mature mRNA, and mutation of this sequence abolished association of SRSF3 with exon 4. SRSF3 expression was upregulated in TNBC cells upon acquisition of AnR correlating with a reduction in the CPEB2A/B ratio. Importantly, downregulation of SRSF3 by siRNA in these cells induced the exclusion of exon 4. Downregulation of SRSF3 also reversed the CPEB2A/B ratio in a wild-type CPEB2 exon 4 minigene construct, but not a mutant CPEB2 minigene with the SRSF3 RNA cis-element ablated. Physiologic studies demonstrated SRSF3 downregulation ablated AnR in TNBC cells, and was “rescued” by ectopic expression of CPEB2B. Importantly, biostatistical analysis of The Cancer Genome Atlas database showed a positive relationship between alterations in SRSF3 expression and lower overall survival in TNBC. Overall, this study demonstrates that SRSF3 modulates CPEB2 AS to induce the expression of the CPEB2B isoform that drives TNBC phenotypes correlating with aggressive human breast cancer.

Over 200,000 cases of breast cancer are diagnosed every year. Nearly 20% of these patients supplement their diets with some form of vitamin D. This high frequency of vitamin D supplement use may be due in part to research suggesting that cancer patients with higher serum vitamin D3 levels have better prognoses than patients with low serum vitamin D3. However, double-blind clinical trials on the efficacy of vitamin D3 supplementation in breast cancer have been inconclusive. A recent meta-analysis showed evidence of reduced cancer recurrence in patients taking vitamin D3 supplements who had ‘estrogen receptor positive’ (ERα66+) breast cancer, but not those who had estrogen receptor negative’ (ERα66-) breast cancer. Once ingested, vitamin D3 is metabolized in the liver into the circulating pre-hormone 25(OH)D3, which is then further metabolized into 1a,25(OH)2D3 and 24R,25(OH)2D3. 24R,25(OH)2D3 has been shown to activate a number of membrane signaling pathways, some of which overlap with 17b-estradiol (E2) signaling through ERα36, a membrane isoform of ERα66. The central hypothesis of this thesis was that 24R,25(OH)2D3 is tumorigenic in certain cancers and that this tumorigenicity is mediated in part by ERa isoforms. E2 signaling through ERa36 has been described in the ERa66-, ERa36+ breast cancer cell line HCC381. Specific aim 1 determined whether E2 signaling through ERa36 was tumorigenic other cancers with different ERa profiles. Specific aim 2 determined how 24R,25(OH)2D3 affected tumorigenicity in breast cancer using the common breast cancer cell line MCF7 (ERa66+, ERa36+) as a model. Specific aim 3 investigated the role of ERa isoforms in 24R,25(OH)2D3 signaling in breast cancer cell lines by comparing the tumorigenic effects of 24R,25(OH)2D3 in MCF7 cells (ERa66+, ERa36+) and HCC38 cells (ERa66-, ERa36+). To determine whether ERa66 regulates the effects of 24R,25(OH)2D3, ERa66 was expressed in two ERα66- cell lines. The effect of 24R,25(OH)2D3 on apoptosis was assessed in wild-type and ERa-expressing cell lines.

It has been shown that the amino terminus and second extracellular loop (EC2) of CXCR2 are crucial for ligand binding and receptor activation. The lack of an ionic lock motif in the third intracellular loop of CXCR2 focuses an investigation of the mechanism by which these two extracellular regions contribute to receptor recognition and activation. The first objective of this investigation was to predict the structure of CXCR2 based on known structures of crystallized GPCRs. Rhodopsin, β2-adrenergic receptor, CXCR4 were used for homology modeling of CXCR2 structure. Highly conserved motifs found in sequence alignments of the template GPCRs were helpful to generate CXCR2 models. We also studied solvent accessibility of residues in the EC2 of CXCR2 in the inactive state. Most of the residues in the EC2 were found to be solvent accessible in the inactive state, suggesting the residues might be involved in ligand recognition. Second, we studied the role of charged residues in the EC2 of CXCR2 in ligand binding and receptor activation using constitutively active mutants (CAM) of CXCR2, D9K and D9R. Combinatorial mutations consisting of the CAM in the amino terminus and single mutations of charged residues in the EC2 were generated to study two concepts including “attraction” and “repulsion” models. The mutant receptors were used to test their effects on cell surface expression, ligand binding, receptor activation through PLC-β3, and cellular transformation. All the mutations in the repulsion model result in CXCR2 receptors that are unable to bind ligand, suggesting that each of the Arg residues in the EC2 are important for ligand recognition. Interestingly, mutations in the attraction model partially inhibited receptor activation by the CAM D9K, suggesting that Glu198 and Asp199 residues in the EC2 are associated with receptor activation. Furthermore, a novel CAM, E198A/D199A, was identified in this study. These negatively charged residues are very close to a conserved disulfide bond linking the EC2 and the third transmembrane. In this sense, these current discoveries concerning the structural basis of CXCR2 and interdisciplinary approaches would provide new insights to investigate unknown mechanisms of interaction with its cognate ligands and receptor activation.

The androgen receptor’s (AR) resurgence following treatment leads to castration resistant prostate cancer (CRPC). Studies show that the aryl hydrocarbon receptor (AhR) regulates AR signaling, is constitutively active, and enhances AR signaling in CRPC. AhR has ligands with carcinogenic properties and interacts with phytochemicals with anti-tumorigenic properties. Curcumin inhibits AhR activity and multidrug transporter ABCG2 activity, which mediates substrates out of the cell. Elevated ABCG2 expression causes resistance to anticancer drugs. AhR transcriptionally activates ABCG2 and our hypothesis is that inhibition of AhR activity by curcumin will decrease ABCG2 expression and activity in CRPC cells. C4-2 cells were treated with increasing concentrations of curcumin (0, 10, 25, 50µM) and CH223191 (50µM). Results show that curcumin decreases AhR, CYP1B1 and ABCG2 gene expression. Higher concentrations of curcumin diminish AhR and ABCG2 protein expression, ABCG2 activity, and cell proliferation. These results will help reveal a role for AhR in drug resistance.