BECN1 is a haploinsufficient tumor suppressor gene that is monoallelically deleted or epigenetically silenced in many human cancers. In breast cancer, 40% of tumors exhibit monoallelic deletion of Beclin 1. Additionally, low Beclin 1 mRNA expression is observed in aggressive breast cancer subtypes and reduced expression is an independent predictor of overall patient survival. The role of Beclin 1 in cancer has almost exclusively been attributed to its function in autophagy. However, our lab demonstrated an alternative role for Beclin 1 in the regulation of growth factor receptor signaling that could contribute to cancer. The goal of my thesis project was to investigate the molecular basis by which Beclin 1 regulates breast tumor growth and progression in vivo. Using in vivo models, I discovered that Beclin 1 promotes endosomal recruitment of hepatocyte growth factor tyrosine kinase substrate (HRS), which is necessary for sorting receptors to intraluminal vesicles for signal silencing and degradation. Beclin 1-dependent recruitment of HRS results in the autophagy-independent regulation of endocytic trafficking and degradation of the epidermal growth factor (EGFR) and transferrin (TFR1) receptors. When Beclin 1 expression is low, endosomal HRS recruitment is reduced and receptor function is sustained to drive tumor proliferation. An autophagy-independent role for Beclin 1 in regulating tumor metabolism was also observed. Collectively, my results demonstrate a novel role for Beclin 1 in impeding tumor growth by coordinating the regulation of growth promoting receptors. These data provide an explanation for how low levels of Beclin 1 facilitate tumor proliferation and contribute to poor cancer outcomes, independently of autophagy.

In this study, we investigated differential activation and the role of two mTOR complexes in cell migration of prostate cancer cells. Specific knock-down of endogenous RAPTOR and RICTOR by siRNA resulted in decreased cell migration in LNCaP, DU145, and PC3 cells indicating that both mTORC1 and mTORC2 are required for cell migration. EGF treatment induced the activation of both mTORC1 and mTORC2 as determined by complex-specific phosphorylation of mTOR protein. Specific knock-down or inhibition of Rac1 activity in PC3 cells blocked EGF-induced activation of mTORC2, but had no effect on mTORC1 activation. Furthermore, the over-expression of constitutively active Rac1 (Rac1Q61L) resulted in significant increase in cell migration and activation of mTORC2 in PC3 cells, but had no effect on mTORC1 activation. Constitutively active Rac1 (Rac1Q61L) in PC3 cells was localized in the plasma membrane and was found to be in a protein complex which contained mTOR and RICTOR proteins, but not RAPTOR. In conclusion, we suggested that EGF-induced activation of Rac1 causes the phosphorylation/activation of mTORC2 via RICTOR, specific regulator of mTORC2 activation in numerous cancer cells. The major role played by mTOR in a wide array of cancers has in the recent decades led to the development of numerous mTOR inhibitors. One of the drawback of these first generation mTOR inhibitors are that m TORC1 activity is inhibited but effect on mTORC2 activity require high dosages and prolonged exposure in different cancer cell types including HeLa, PC3, LNCaP, and A549. High dosage of rapamycin and its associated rapalogs required for mTORC2 inhibition is clinically unsuitable. Studies have shown that the dual mTORC1/C2 inhibitors trigger feedback loops causing metastasis and affect the cell viability of normal tissues in vitro and in vivo. There is a need for specific mTORC1 and mTORC2 inhibitor, which overcome the disadvantages of the previously developed mTOR inhibitors. The Rac1-RICTOR axis suggested in this study could be used as a potential target for the development of mTORC2 inhibitor and lead to a potential therapeutic treatment for aggressive prostate cancer.

The largest U.S. cancer health disparity exists in prostate cancer, with African American men having the highest incidence and mortality rates. The present study evaluated the effects of ZIC2 and the underlying mechanisms in the E006 parental African-American cell line that produces tumors at accelerated growth rates because of the increase of ZIC2 genes in African-American males. We analyzed the experimental research that the overexpression of ZIC2 contributes to progression of prostate cancer. E006AA cells with overexpressed or suppressed ZIC2 were analyzed to determine phenotypic differences, PCR, cell proliferation and immunoblot assays. The expression levels of ZIC2 were analyzed by CRISPR-Cas9, Western blot and proliferation growth curves. We discovered using these experimental techniques to knockout ZIC2, reduced cell proliferation occurred. This research investigated the role of ZIC2 in prostate cancer progression and the effects of the loss or gain of function of ZIC2 by using CRISPR-Cas 9 genome editing technology.

Endogenous and exogenous agents that can damage DNA are a constant threat to genome stability in all living cells. In response, cells have evolved an array of mechanisms to repair DNA damage or to eliminate the cells damaged beyond repair. One of these mechanisms is nucleotide excision repair (NER) which is the major repair pathway responsible for removing a wide variety of bulky DNA lesions. Deficiency, or mutation, in one or several of the NER repair proteins is responsible for many diseases, including cancer. Prokaryotic NER involves only three proteins to recognize and incise a damaged site, while eukaryotic NER requires more than 25 proteins to efficiently recognize and incise a damaged site. XPC-RAD23B (XPC) is the damage recognition factor in eukaryotic global genome NER. The association rate of XPC to damaged DNA has been extensively studied; however, our data suggests that the dissociation of the XPC-DNA complex is the rate-limiting step in NER. The factor that verifies DNA-damage downstream of XPC is XPA. XPA also has been implicated in binding of ds-ssDNA junctions and has been found to bind at or near double-strand break sites in the premature aging syndrome Hutchinson-Gilford progeria (HGPS). This role for XPA is outside of its known function in NER and suggests that XPA may bind at collapsed replication forks in HGPS that are unprotected due to a lack of binding by replication proteins. Along with XPC and XPA, ataxia telangiectasia and Rad3-related (ATR) is activated in response to DNA damage and initiates the cell cycle checkpoint pathway to rescue cells from genomic instability. We found that ATR functions outside of its known role in the checkpoint signaling cascade. Our data demonstrate that ATR can rescue cells from apoptosis by inhibiting cytochrome c release at the mitochondria though direct interaction with the outer mitochondrial membrane and the proapoptotic protein tBid. The role of ATR in apoptosis is regulated by Pin1, which can change the structure of ATR at the backbone level. All of the results presented here suggest novel roles for DNA repair proteins in the maintenance of genome stability.

Cisplatin is a chemotherapy drug effective against several forms of cancer, but can also cause serious side-effects, including nephrotoxicity and ototoxicity. Curcumin, a natural plant compound, can increase cisplatin’s anti-cancer activity and counteract cisplatin’s deleterious effect on the auditory and renal systems. Unfortunately, curcumin exhibits poor bioavailability, which has promoted interest in the development of synthetic curcumin analogs (curcuminoids) that are soluble, target cancer, and do not cause side effects. This study investigated whether the curcuminoid (3E,5E)-3,5-bis[(2-fluorophenyl) methylene]-4-piperidinone (EF-24) increases the anti-cancer effects of cisplatin against a human ovarian cancer cell line (A2780) and its cisplatin-resistant counterpart (A2780cis), while preventing cisplatin-mediated side effects in a human kidney cell line (HEK-293T) and a mouse auditory hybridoma cell line (HEI-OC1). The effect of cisplatin and EF-24 on cellular viability was measured using the colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay. The expression and activity of signal transduction proteins in several apoptotic pathways was measured using caspase luminescence assays. Reactive oxygen species (ROS) production was also measured using flow cytometry. Our data suggest that cisplatin and EF-24 are effective against ovarian cancer cell lines, but both compounds may also have adverse effects on auditory and renal cells. This project provides relevant information that may improve our understanding of how these compounds function in different tissues, facilitating improved cancer treatment and circumvention of side effects commonly associated with cisplatin treatment.

The progesterone receptor membrane component 1 (PGRMC1) is a multifunctional protein with a heme-binding domain that promotes cellular signaling via receptor trafficking, and is essential for some elements of tumor growth and metastasis. PGRMC1 is upregulated in breast, colon, lung and thyroid tumors. We expanded the analysis of PGRMC1 in the clinical setting, and report the first analysis of PGRMC1 in human oral cavity and ovarian tumors and found PGRMC1 to correlate with lung and ovarian cancer patient survival. Furthermore, we discovered a specific role for PGRMC1 in cancer stem cell viability. PGRMC1 directly associates with the epidermal growth factor (EGFR) in cancer cells, and we reviewed multiple signaling-associated pathways that are important in trafficking wild-type and mutant EGFR. To better understand the potential of PGRMC1 in receptor tyrosine kinase trafficking, we extended our research to the insulin receptor (IR). Changes in insulin signaling have been linked to multiple diseases, because IR plays a key role in glucose metabolism, cellular survival and proliferation. We found PGRMC1 to co-precipitate with IR in cancer cells and in an adipose model system. PGRMC1 increased IR plasma membrane levels in multiple cancer cell lines, and was also found to increase plasma membrane levels of two glucose transporters. Treatment with a PGRMC1 ligand significantly increased IR levels in human adipocytes. Moreover, we demonstrate that both insulin binding and glucose uptake are dependent on PGRMC1.

Single molecule studies can provide information of biological molecules which otherwise is lost in ensemble studies. A wide variety of fluorescence-based techniques are utilized for single molecule studies. While these tools have been widely applied for imaging soluble proteins, single molecule studies of transmembrane proteins are much more complicated. A primary reason for this is that, unlike membrane proteins, soluble proteins can be easily isolated from the cellular environment. One approach to isolate membrane proteins into single molecule level involves a very low label expression of the protein in cells. However, cells generate background fluorescence leading to a very low signal to noise ratio. An alternative approach involves isolating membrane proteins in artificial membrane derived vesicles. This approach is limited to proteins which can be solubilized or stabilized in detergent solution. This intermediate step endangers the structural integrity of proteins with multiple subunits. Hence, we isolated transmembrane proteins into cell-derived vesicles which maintain the proteins in their physiological membrane without compromising their functional integrity. We studied the stoichiometric assembly of α3β4 nicotinic receptors which are pentameric receptor with possible stoichiometry of (α3)2(β4)3 and (α3)3(β4)2. We found that (α3)2(β4)3 is the predominant stoichiometry, and we have verified our finding with both single and double color experiments. We have also demonstrated that cell-derived vesicles can be utilized to study ligand receptor interactions. Cell-derived vesicles generated from cellular preparations provide a method to study the overall structural and functional properties of membrane proteins. However, organelle specific information is not available in this approach. Alternatively, separating vesicles based on their original organelle could provide information on the assembly and trafficking of membrane proteins. For example, it has been hypothesized that nicotine acts as a pharmacological chaperone of α4β2 nicotinic receptors and nicotine alters the assembly of the nicotinic receptors towards the high sensitivity isoform in the ER. To validate this hypothesis, we isolated α4β2 nicotinic receptors located on vesicles derived from the ER and plasma membrane origins and utilized single molecule studies to determine the stoichiometric assembly of the receptor. The data suggested that the ER has a higher percentage of the low sensitivity isoform ((α4)3(β2)2) than the plasma membrane indicating that the high sensitivity isoform trafficked more efficiently to the cell surface. When nicotine was added, the distribution of nicotinic receptors changes in those compartments. In both the ER and plasma membrane, the percentage of high sensitivity isoform was greater than the sample without the presence of nicotine. The results suggested that nicotine altered the assembly of nicotinic receptors to form the high sensitivity isoform in the ER and the altered assembly trafficked to the plasma membrane efficiently increasing the ratio of this isoform in the plasma membrane. The cell derived vesicles we utilized to isolate single receptors are structurally similar to liposomes, an FDA approved drug delivery system, which is spherical vesicles composed of at least one lipid bilayer. Hence, cell-derived vesicles possess potential to be utilized as drug delivery vehicles. I explored the applicability of cell-derived vesicles as general delivery vehicles to cultured cells. Additionally, we implanted xenografts into immune compromised nude mice and prepared cell derived vesicles labeled with dye molecules. The vesicles were injected in a mouse containing a xenograft to monitor whether these vesicles can reach to the xenograft. Our data suggested that cell-derived vesicles can successfully reach the xenograft and thus have potential to be utilized as a drug delivery vehicle.

Lung cancer is the number one cause of cancer related death worldwide, with more than 1.6 million fatalities each year. Non-small cell lung cancer (NSCLC) accounts for 80-85% of all lung cancers, with KRAS being one of the most prevalent oncogenic driver mutations. Therapeutic approaches for KRAS-mutated NSCLC have been extensively explored due to the US National Cancer Institute RAS Initiative, but methods of directly targeting KRAS or downstream effectors, such as MEK, still have poor results. Previous reports have shown that KRAS-mutated NSCLC activate distinct receptor tyrosine kinases (RTKs) depending on the epithelial or mesenchymal state. Epithelial-to-mesenchymal transition (EMT) is known to play a role in the metastasis and poor prognosis of cancer, and is induced by extracellular matrix (ECM) stiffness. Hallmarks of EMT include loss of E-Cadherin and increase in Vimentin. This research investigates the role of KRAS in EMT transition due to increased ECM stiffness in KRAS mutant NSCLC, and how this affects the efficacy of KRAS and MEK inhibition. To understand how KRAS mutations in NSCLC play a role in this stiffness induced EMT, experiments were performed to detect the gene and protein expression of EMT markers, as well as possible sources of mechanosensing, including primary cilia and receptor tyrosine kinases. We hypothesized that KRAS plays a role in activation of mechanosensors and directly correlates to EMT induced by increased mechanical forces. Results show when KRAS was inhibited and there was increased mechanical forces, either from stretch or substrate stiffness, there was a decreased activation of mechanosensors. KRAS inhibition also prevented the cells from undergoing stiffness-induced EMT. This supports our hypothesis that KRAS plays a key role in ECM stiffness induced EMT. Future studies include examining the mechanism behind this phenomenon and in vivo studies.

Telomeres are the chromosome end structures consisting of telomere-associated proteins and short tandem repeat sequences, TTAGGG, in humans and mice. Telomeres prevent chromosome termini from being recognized as broken DNA ends. The structural integrity of DNA including telomeres is constantly threatened by a variety of DNA damaging agents on a daily basis. To counteract the constant threats from DNA damage, organisms have developed a number of DNA repair pathways to ensure that the integrity of genome remains intact. A number of DNA repair proteins localize to telomeres and contribute to telomere maintenance; however, it is still unclear as to what extent. Telomere shortening has been linked to rare human disorders that present with bone marrow failure including Fanconi anemia (FA). FANCC is one of the most commonly mutated FA genes in FA patients and the FANCC subtype tends to have a relatively early onset of bone marrow failure and hematologic malignancies. Here, we studied the role of Fancc in telomere length regulation in mice. We demonstrated that deletion of Fancc did not affect telomerase activity, telomere length or telomeric end-capping in mice with long telomeres. We also showed that Fancc deficiency accelerates telomere shortening during high turnover of hematopoietic cells and promotes telomere recombination initiated by short telomeres. Telomere shortening has also been linked to human aging and cancer development, with oxidative stress as a major contributing factor. 8-oxo-7, 8-dihydroguanine is among the most common oxidative DNA lesions, and is substrates for OGG1-initiated DNA base excision repair. Mammalian telomeres consist of triple guanine repeats and are subject to oxidative guanine damage. Here, we investigated the impact of oxidative guanine damage and its repair by OGG1 on telomere integrity. We demonstrated that oxidative guanine damage can arise in telomeres where it affects length homeostasis, recombination, DNA replication, and DNA breakage repair. We also examined if telomeric DNA is particularly susceptible to oxidative guanine damage and if telomere specific factors affect the incision of oxidized guanines by OGG1. We showed that the GGG sequence context of telomere repeats and certain telomere configurations may contribute to telomere vulnerability to oxidative DNA damage processing.

Pain is the most feared symptom of cancer and can impact patients' lives more than the cancer itself. Despite improvements in cancer prevention and detection, pain is often the first sign of cancer, with an estimated 70-75% of advanced stage cancer patients presenting with skeletal metastases. Cancer metastasis to the bone is associated with persistent pain that increases in intensity over time. Current treatments follow the World Health Organization (WHO) analgesic ladder for cancer pain management suggesting non-steroidal anti-inflammatory drugs (NSAIDs) for mild to moderate pain and opioids for moderate to severe pain. However, estimates indicate as many as 50-80% of cancer patients worldwide receive inadequate pain management. Moreover, opioid doses required for these patients are associated with adverse side effects further diminishing quality of life. Development of improved non-opioid therapies is dependent on increased understanding of mechanisms driving cancer pain and its relief. The objective of this dissertation was to characterize a rat model of cancer-induced bone pain, to develop approaches to measure both ongoing and breakthrough pain and to investigate the contribution of underlying inflammatory mechanisms to pain, bone destruction and bone remodeling. Using female Fischer F344/NhSD rats, histocompatible MAT B III mammary adenocarcinoma cells were sealed into the intramedullary space of the right rear tibia for a time course of 13 days. Ongoing pain was characterized based on the WHO 3-step ladder for pain management utilizing novel behavioral and neurochemical assays. Morphine and peripheral nerve block were sufficient to control ongoing pain, whereas NSAID treatment failed to provide pain relief. Cancer-bearing rats selectively displayed movement-induced breakthrough pain to a background of morphine-controlled ongoing pain. Furthermore, we determined that breakthrough pain is initiated, but not maintained, by peripheral afferent input from the tumor-bearing tibia using lidocaine administration prior to or following movement. For the final part of this study, we investigated the role of transient receptor potential vanilloid 1 (TRPV1) and interleukin-6 (IL-6) blockade, as these have been shown to be important mediators in animal models CIBP. Acute blockade of TRPV1 channels by AMG9810 selectively reversed inflammatory-induced pain, but failed to control evoked or ongoing CIBP. Acute blockade of interleukin-6 signaling by TB-2-081, an IL-6 receptor antagonist, successfully reversed evoke pain responses, but like AMG9810, failed to control ongoing pain. Sustained administration of TB-2-081 reversed cancer-induced tactile hypersensitivity and tumor-induced bone remodeling of the tibia. Further in vitro analysis revealed TB-2-081 functions by inhibiting the Jak/STAT cascade on both tumor cells and osteoblasts, suggesting that blockade of IL-6 signaling can effectively modulate the bone microenvironment to reduce tumor burden and pain. Combined, our data introduce a rat model of breast cancer bone metastasis, in which the underlying mechanisms of ongoing and breakthrough CIBP can be effectively studied. From this, novel therapeutic agents can be developed and investigated to help improve quality of life in patients suffering from this disease.