Browsing by Subject "EGFR"
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Item Dietary energy balance modulates growth factor signaling during multistage epithelial carcinogenesis in mouse skin(2010-12) Moore, Tricia Wallace; DiGiovanni, John; Hursting, Stephen; Kline, Kimberly; deGraffenried, Linda; Fischer, Susan; Vasquez, KarenEnergy balance refers to the relationship between energy intake and energy expenditure. Epidemiological studies have established a clear association between energy balance and cancer, however the underlying mechanisms are unclear. The objective of the current study was to evaluate the impact of caloric consumption on epithelial carcinogenesis and identify potential mechanisms of inhibition or enhancement. Using ICR female mice, we demonstrated that positive energy balance enhanced, while negative energy balance inhibited susceptibility to multistage carcinogenesis in mouse skin. We next evaluated diet-induced changes in the epidermal proliferative response. Calorie restriction (CR) significantly reduced epidermal hyperproliferation, in the presence and absence of tumor promotion, as compared to diet-induced obesity (DIO). Additional studies were conducted to determine the impact of dietary manipulation on TPA-induced growth factor signaling. CR reduced, while DIO increased insulin like growth factor-1 receptor (IGF-1R) and epidermal growth factor receptor (EGFR) activation, which subsequently modulated signaling downstream to Akt and mTOR. These diet-induced changes in growth factor signaling were confirmed under steady-state conditions in multiple epithelial tissues (i.e., skin, liver and dorsolateral prostate) in multiple mouse strains (FVB/N, C57BL/6 and ICR). Further analyses demonstrated that caloric consumption directly correlated with levels of cell cycle progression related proteins and inversely correlated with levels of cell cycle inhibitory proteins. Genetic reduction of circulating IGF-1, liver IGF-1 deficient (LID) mouse model, inhibited two-stage skin carcinogenesis, reduced epidermal hyperproliferation and attenuated IGF-1R and EGFR growth factor signaling during tumor promotion, similar to CR, suggesting a potential for IGF-1R and EGFR crosstalk. Further studies, demonstrated that IGF-1 induced EGFR activation in cultured mouse keratinocytes, possibly due to IGF-1R and EGFR heterodimerization or IGF-1 induced changes in EGFR mRNA expression. In vivo, CR reduced, while DIO increased IGF-1R and EGFR association during tumor promotion. Furthermore, CR attenuated EGFR ligand mRNA expression both in the presence and absence of TPA treatment. Collectively, these findings suggest that dietary energy balance modulates epithelial carcinogenesis, at least in part due to diet-induced changes in levels of circulating IGF-1, which then modulate IGF-1R and EGFR crosstalk and downstream signaling to cell cycle related proteins, subsequently altering epidermal hyperproliferation.Item Interactions of composite gold nanoparticles with cells and tissue : implications in clinical translation for cancer imaging and therapy(2012-12) Tam, Justina Oichi; Sokolov, Konstantin V. (Associate professor)Current methods to diagnose and treat cancer often involve expensive, time-consuming equipment and materials that may lead to unwanted side effects and may not even increase a patient’s chance of survival. Thus, for a while now, a large part of the research community has focused on developing improved methods to detect, diagnose, and treat cancer on the molecular scale. One of the most recently discovered methods of cancer therapy is targeted therapy. These targeted therapies have potential to provide a patient with a form of personalized medicine because these therapies are biological molecules that specifically target other molecules involved with a cancer’s growth. Past trials using these therapeutic molecules, however, have led to controversial results, where certain patients responded better than others to the therapy for unknown reasons. Elucidating the reason behind these mixed results can be accomplished using metal nanoparticle technologies which could provide a bright signal to monitor the path that these therapeutic molecules take in vivo as well as enhance the molecule’s efficacy. Literature has shown that presenting targeting molecules in a dense manner to their target will increase these molecules’ binding affinity. This concept has been explored here to increase binding affinity of therapeutic molecules by attaching these molecules in a dense manner on the surface of gold nanoparticles, and correlating this increased affinity with therapeutic efficacy. Additionally, gold nanoparticles provide an easy surface for molecules to be functionalized on and have shown to be effective imaging, x-ray, and photothermal therapy agents. A major roadblock to using these gold nanoparticles clinically is their non-degradability and thus potential to cause long-term negative side effects in vivo. A platform for developing biodegradable gold nanoparticles is also explored here to take advantage of the gold nanoparticles’ excellent imaging and drug delivery capabilities while still allowing them to be used safely in the long term.Item Mechanisms of Action of Metformin as an Anti-cancer Agent(2014-08-13) Ramachandran Nair Vasanthakum, VijayalekshmiCancer is the second leading cause of death worldwide and epidemiological studies suggest the association of diabetes mellitus with an enhanced risk for multiple cancers. Metformin (1,1-dimethylbiguanide hydrochloride) is the most widely prescribed anti-diabetic drug. However, in addition to its anti-diabetic activity metformin exhibits antineoplastic effects by inhibiting development of tumors and also by inhibiting tumor growth, survival and metastasis. Specificity protein (Sp) transcription factors (TFs) belong to the Sp/Kruppel-like family of transcription factors (KLFs). Sp1 and other Sp proteins are overexpressed in many tumors and regulate the expression of genes essential for cancer cell proliferation, growth, angiogenesis, and survival. Based on the reported metformin-induced activities in cancer cells and tumors, we hypothesize that the anti-neoplastic effect of metformin is due, in part, to downregulation of Sp transcription factors in cancer cells. Treatment of pancreatic cancer cells with metformin inhibited cell proliferation, induced apoptosis and also downregulated Sp1, Sp3 and Sp4 proteins and several prooncogenic Sp-regulated genes. Metformin also decreased microRNA-27a and induced the Sp repressor, ZBTB10, and disruption of miR-27a:ZBTB10 interaction by metformin was mediated by MAPK phosphatases 1 and 5 (MKP1 & MKP5). Furthermore, we also demonstrated that treatment with metformin or downregulation of Sp TFs by RNA interference (RNAi) inhibited two major pro-oncogenic pathways in pancreatic cancer cells, namely insulin-like growth factor receptor (IGF-1R) mediated mTOR signaling and epidermal growth factor (EGFR)-dependent activation of RAS. Knockdown of IGF-1R and EGFR inhibited mTOR signaling and RAS activity respectively. Metformin also inhibited pancreatic tumor growth and downregulated Sp and Sp regulated genes in tumors in an orthotopic model. We also investigated the antineoplastic effect of metformin in breast cancer cells. The effects of metformin in breast cancer cells were comparable to those observed in pancreatic cancer cells. In addition, metformin also decreased expression of ErbB2 in breast cancer cells overexpressing this oncogene. Treatment with metformin or downregulation of Sp TFs by RNAi decreased expression of ErbB2, YY1 and mTOR signaling. Results of this study have unraveled an important mechanism of action of metformin in cancer cells which will facilitate the design of clinical applications of metformin in various combination drug therapies.Item The Non-genomic Signaling Pathways Mediated By G-protein Coupled Estrogen Receptor 1 (GPER) In Coronary Arteries(2014-12-04) Yu, XuanCoronary heart disease (CHD) remains the leading cause of death throughout the world, and postmenopausal women are at particularly high risk for CHD. A promising new avenue of study is the novel G protein-coupled estrogen receptor (GPER) which mediates estrogen action. The major purpose of my studies in this dissertation is to investigate the role of GPER in porcine coronary artery tone regulation. In a series of studies, we tested four hypotheses: 1) activation of GPER regulates coronary artery tone by paradoxically inducing relaxation and potentiating contraction; 2) activation of GPER induces coronary artery relaxation by Gs/cAMP-dependent pathway(s); 3) activation of GPER induces coronary artery relaxation via inhibition of RhoA/Rho kinase pathway by cAMP downstream targets: the exchange proteins directly activated by cAMP (Epac) as well as PKA; and 4) activation of GPER potentiates coronary artery contraction by a G??/EGFR-dependent pathway. Isometric tension studies were performed on endothelium-denuded porcine coronary arteries to test the function role of GPER and its signaling pathways. RT-PCR, Western blots, patch-clamp experiments and kinase activity assays also were employed in these studies to confirm the expression and phosphorylation of subjective proteins, channel activities and kinase activities in porcine and human coronary artery smooth muscle cells (SMCs) and coronary artery tissues. Results from these studies suggest: 1) GPER is expressed in porcine and human coronary artery SMCs; 2) GPER mediated coronary artery relaxation is NO-independent and involves BKCa channel activity; 3) activation of GPER stimulates the production of cAMP, thus activates its downstream targets PKA and Epac; 4) GPER mediates coronary relaxation through activation of MLCP via inhibition of RhoA activity by both PKA and Epac; 5) the interaction between AKAP and PKA is involved in the cAMP/PKA signaling mediated by GPER in coronary artery; and 6) GPER potentiates coronary artery contraction via G?? signaling to stimulate transactivation of EGFR and activation of ERK1/2. These findings provided evidence of the dual effects of GPER in coronary regulation, which may help reveal the controversial actions of estrogen and provide a molecular basis for developing new compounds that better target estrogen signaling for a variety of clinical applications.