The adult Drosophila central nervous system is produced by two phases of neurogenesis: the first phase occurs during embryonic development where the larval brain is formed and the second occurs during larval development to form the adult brain. Neurogenesis in both phases is caused by the activation of neural stem cell division and subsequent progenitor cell division and terminal differentiation. Proper activation of neural stem cell division in the larval brain is essential for proper patterning and functionality of the adult central nervous system. Initiation of neural stem cell proliferation requires signaling from the Fibroblast Growth Factor (FGF) homolog Branchless (Bnl) and by the Hedgehog (Hh) growth factor. I have focused on the interactions between both of these signaling pathways with respect to post-embryonic neural stem cell proliferation using the Drosophila larval brain. Using proliferation assays and quantitative real-time PCR, I have shown that Bnl and Hh signaling is inter-dependent in the 1st instar larval brain and activates neural stem cell proliferation. I have also shown that overexpression of bnl can rescue signaling and neuroblast proliferation in a hh mutant. However, overexpression of hh does not rescue signaling or neuroblast proliferation in a bnl mutant, suggesting that Bnl is the signaling output of the Bnl-Hh feedback loop and that all central brain and optic lobe neural stem cells require Bnl signaling to initiated proliferation.

Thesis (Ph. D. in Cancer Biology)--Vanderbilt University, Dec. 2008. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago, Dept. of Neurobiology, Pharmacology and Physiology, June 2001. / Includes bibliographical references. Also available on the Internet.

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains vii, 78 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 70-78).

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: factor; FGF-23; phosphatonin; microarray; expression; phosphate; time; gene; RT-PCR; growth; fibroblast. Includes bibliographical references (p. 127-136).

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

Fibroblast Growth Factor (FGF) 21 is a liver-derived endocrine factor with multiple metabolic effects on glucose and lipid homeostasis in animals. The adipose tissue has been proposed as a major target of FGF21, where it enhances glucose uptake and modulates lipolysis as well as thermogenesis. However, the molecular mechanisms underlying the pleiotropic effects of FGF21 in adipocytes and the physiological roles of FGF21 in regulating energy homeostasis remain poorly characterized. Therefore, the present study aimed to investigate: 1) the signal transduction pathway whereby FGF21 enhances glucose uptake in white adipocytes; 2) the role of FGF21 in lipolysis in both mouse and human white adipose tissues (WAT) and its underlying mechanisms involved; 3) the phenotypes of FGF21 knockout (KO) mice with respect to energy expenditure and adiposity under both standard chow and high fat diet. Key findings: 1. In vitro studies demonstrated that extracellular signal-regulated kinases (ERK1/2) play an obligatory role in mediating FGF21-induced upregulation of glucose transporter-1 (GLUT1) expression and hence elevation of glucose uptake in 3T3-L1 adipocytes. 2. Chromatin immunoprecipitation assay revealed that Serum Response Factor (SRF) and ETS-like protein-1 (Elk-1), the two transcription factors which are known as the downstream targets of ERK1/2, were recruited to the endogenous GLUT1 promoter in adipocytes. A conserved binding motif for these two transcription factors was also identified in the GLUT1 promoter responsive to FGF21 stimulation in 3T3-L1 adipocytes by site-directed mutagenesis and luciferase assay. 3. In WAT of diet-induced obese mice, FGF21-evoked downstream signaling events, including the phosphorylation of ERK1/2 and SRF/Elk-1, the upregulation of GLUT1, and the increased glucose uptake, were markedly blunted compared to lean controls, suggesting the existence of “FGF21 resistance” in obesity. 4. In vivo and ex vivo studies on fasted wild type and FGF21 KO mice demonstrated that FGF21 acutely suppressed basal and forskolin-stimulated lipolysis in WAT. 5. FGF21-inhibited lipolysis was mediated by Akt-dependent reduction of cyclic adenosine monophosphate (cAMP) levels in both mouse and human WAT. 6. FGF21 KO mice were resistant to diet- and aging-induced obesity, which was attributed to decreased fat mass. The increased lipolysis and fatty acid oxidation in FGF21 KO mice may explain in part the lean phenotype of FGF21 KO mice. Conclusions: These results collectively suggest FGF21 as a key modulator of glucose and lipid metabolism in WAT, by activation of ERK1/2 kinase and Akt respectively. FGF21 and its signaling components may represent potential targets for the future development of new strategies for treating obesity and its medical complications. / published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

Hepatocellular carcinoma (HCC) is the fifth most common malignancy and the third leading cause of cancer related death worldwide. Chemo-therapy has been commonly used to treat unresectable HCC but with limited efficacy. Therefore, there is an urgent demand for the development of better therapeutic approaches. Granulin-epithelin precursor (GEP) is a novel growth factor with over-expression in more than 70% of HCCs and has been demonstrated as potential therapeutic target. The aims of this study are to examine the role of GEP in chemo-resistance and the therapeutic potential of GEP antibody therapy in combination with chemo-therapy in HCC. The role of GEP in HCC chemo-resistance has been examined by HCC in vitro models in the first part of the study and by in vivo human HCC xenograft models in immunocompromised mice in the second part of the study. It was shown that the chemo-therapeutic agents selected HCC cells in vitro and in vivo resulted in increased cellular expression of GEP, ABCB5, hepatic cancer stem cell (CSC) marker CD133/EpCAM positive populations and demonstrated enhanced CSCs properties including colony formation ability and chemo-resistance. Over-expression and knockdown of GEP expressions respectively demonstrated that GEP levels were important in conferring resistance to the chemo-therapeutic agents and the drug-induced apoptosis. GEP antibody therapy not only sensitized the parental HCC populations but also the chemo-resistant subpopulations to chemo-therapy induced apoptosis. Importantly, combination of GEP antibody therapy with chemo-therapy inhibited the chemo-therapy induced GEP, ABCB5 and heaptic CSCs marker over-expression through neutralization of the secretary GEP levels in the culture supernatant, and the serum GEP levels in the HCC orthotopic mice model. In human HCC xenograft models, GEP antibody treatment alone is consistently able to inhibit the tumor growth, but is unable to eliminate the established intrahepatic tumor. Cisplatin treatment, low and high dose respectively, was only able to eradicate a fraction of the intrahepatic tumor and the residual tumors grew aggressively after chemo-drug withdrawal. Combination of GEP antibody with low dose of cisplatin resulted in significant proliferation inhibition and apoptosis induction respectively. Importantly, combination of GEP antibody with high dose of cisplatin resulted in eradication of all established intrahepatic tumor. In addition, chemo-therapy induced the Akt/PKB and MEK/ERK prosurvival pathways, disturbed the balanced between the ratio of pro-apoptotic (Bax) to anti-apoptotic (Bcl-2) member through the induction of Bcl-2. Nonetheless, combination GEP antibody therapy suppressed the chemo-therapy induced phosphorylation of PDK1, Akt, MEK, ERK, and Bcl-2 levels. It was shown that Wortmannin, the PI3K/Akt inhibitor, suppressed the expression of ABCB5 and Bcl-2 induced by chemo-therapy but showed no effect on GEP expression levels. In summary, the study demonstrated the chemo-therapy treatment alone induced the expression of growth factor GEP, drug transporter ABCB5, hepatic cancer stem cell markers expressions, and the residual cancer cells showed enhanced CSCs properties. Combination treatment with GEP antibody reversed the signaling and cancer stem cell properties induced by chemo-therapy alone. Therefore, further investigations of this combination treatment approach may lead to the development of novel therapeutic approach for the clinical treatment of chemo-resistant HCC. / published_or_final_version / Surgery / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / toc / Zoology / Master / Master of Philosophy

published_or_final_version / Zoology / Master / Master of Philosophy