Thesis (degree.)--Marshall University, 2009. / Title from document title page. Includes abstract. Document formatted into pages: contains 57 p. Includes bibliographical references p. 51-57.

Thesis (M.A.)--Catholic Theological Union at Chicago, 2007. / Vita. Includes bibliographical references (leaves 42-47).

Thesis (M.A.)--Catholic Theological Union at Chicago, 2007. / Vita. Includes bibliographical references (leaves 42-47).

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 4 uppsatser.

Activation of Ras/mitogen-activated protein kinase (ERK MAPK) signalling controls the differentiation of mouse embryonic stem (ES) cells. An established modulator of the ERK MAPK pathway is the IRS-1 (Insulin Receptor Substrate 1) family adaptor protein Gab1 (Grb2-associated binder 1). Gab1 is ubiquitously expressed and is activated by a wide range of cell surface receptors, mediating growth factor, cell-cell and cell-substratum interactions. The N-terminal region of Gab1 contains a pleckstrin homology (PH) domain required for membrane binding and a nuclear localisation sequence (NLS) that facilitates nuclear translocation. Undifferentiated mouse ES cells preferentially express high levels of a novel form of Gab1 (Gab1β) lacking the N-terminal region. Based on its novel structure and abundance, Gab1β may act in a dominant negative manner by binding and mislocalising downstream effectors. Alternatively, it may have a deregulated function unrestrained by the PH or NLS domains. Data presented here shows that Gab1β is tyrosine phosphorylated in response to the self-renewal factor Leukemia Inhibitory Factor (LIF) and/or Foetal Bovine Serum (FBS) stimulation. This then leads to the formation of complexes with Shp2 and the p85 subunit of PI3K. Experiments comparing the responses of wild-type and Gab1β knock-out ES cells indicate that Gab1β enhances ERK and potentially AKT phosphorylation in response to LIF. In contrast, Gab1β has a negative effect on ERK and AKT phosphorylation in response to IGF-1 (Insulin Growth Factor 1). These results suggest that the contribution of Gab1β to signalling activity is receptor specific and may imply that the response of ES cells to ERK activation is context specific. By reintroducing fluorescently tagged Gab1 proteins into Gab1β knockout ES cells, I investigated the localisation of Gab1β in ES cells. Gab1β localised at the cell membrane as well as in a perinuclear body. I next investigated the potential role of Gab1β in the differentiation of ES cells into neural precursors. A monolayer differentiation protocol was used to differentiate Gab1β wild-type and knock-out cells into neural precursors. Furthermore, the effect of insulin on the emergence of neural precursors from Gab1β-targeted cells was also explored.

C-X-C chemokine receptor type 4 (CXCR4) is known to regulate lung, pancreatic and prostate cancer stem cells. In breast cancer, CXCR4 signalling via stromal cell-derived factor-1 (SDF-1) has been reported to be a mediator of metastasis, and is linked to poor prognosis. However its role in normal and malignant breast stem cell function has not been investigated. Anoikis-resistant (AR) cells were collected from mammosphere culture from 2 immortalised (MCF10A, 226L) and 3 malignant (MCF7, T47D, SKBR3) breast cell lines. For all cell lines, AR cells had a significantly higher mammosphere forming efficiency (MFE) than unsorted cells. The AR cells of the normal cell lines also demonstrated increased formation of 3D structures using the Matrigel assay. In vivo, MCF7 and T47D AR cells demonstrated increased capacity to form tumours compared with unsorted cells. This suggests that AR cells are enriched for normal and malignant breast stem cells. We performed an Agilent custom gene microarray and demonstrated up-regulation of CXCR4 mRNA expression in AR cells. CXCR4 protein expression was also higher in AR cells, shown by flow cytometry. The effects of AMD3100 (CXCR4 antagonist) and SDF-1 (CXCR4 ligand) on stem cell activity were investigated in the mammosphere assay. In the normal cell lines, SDF-1 significantly reduced MFE and this decrease was rescued by AMD3100. Incubation with AMD3100 increased MFE in the estrogen receptor positive breast cancer cell lines (MCF7 and T47D) and patient-derived metastatic tumour samples. AMD3100 reduced the self-renewal of T47D cells, as assessed by second generation mammospheres. MCF7 cells were retro-virally transfected to over-express CXCR4 or sorted for CXCR4 cell surface expression. Mammosphere formation was significantly increased in CXCR4+ and CXCR4 over-expressing cells compared with CXCR4- and parental cells. There was a greater reduction in self-renewal following AMD3100 treatment in the CXCR4 over-expressing cells compared with parental cells. AMD3100 has been shown to have an agonistic effect on the novel chemokine receptor CXCR7, a scavenging receptor for SDF-1. All cell lines demonstrated cell surface expression of CXCR7, measured by flow cytometry and mRNA expression. Potential interactions between CXCR4, CXCR7 and SDF-1 must be considered in future investigation of the role of CXCR4 signalling. Our data establish that CXCR4 signalling has contrasting effects on normal and malignant breast stem cell activity. CXCR4 influences self-renewal of malignant stem cells which may account for its role in tumorigenesis. CXCR4 signalling may be important in tumour formation at the sites of metastases as well as in cell migration. Its role in stem cell migration merits further investigation. In conclusion, CXCR4-targeted therapy, alongside current standards of care, may improve breast cancer outcomes.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Nevada, Reno, 2006. / "May, 2006." Includes bibliographical references. Online version available on the World Wide Web.

Thesis (M.S.)--University of Alabama at Birmingham, 2006. / Description based on contents viewed Jan. 29, 2007; title from title screen. Includes bibliographical references (p. 51-54).

Thesis (Ph. D.)--University of Hong Kong, 2006. / Also available online.