Joyce Wu

JOYCE WU -MSc DEFENSE

“YB-1 is a Downstream Component of the PI3K/Akt Signaling Pathway and Regulates EGFR in Breast Carcinoma: A Mechanism for Breast Cancer Growth”

B.Sc. University of British Columbia, 2003
Thursday, August 17, 2006, 9:00 am, Room 3110, Child and Family Research Institute

Joyce Wu- MSc Defense program- pdf

SUPERVISORY COMMITTEE

Dr. Sandra Dunn
Dr. Rob Kay
Dr. Michael Kobor
Dr. Wan Lam

EXAMINING COMMITTEE

Chair:Dr. Wendy Robinson (Medical Genetics)
Supervisory Committee: Dr. Sandra Dunn, Research Supervisor (Medical Genetics), Dr. Michael Kobor (Medical Genetics)
University Examiners: Dr. Fabio Rossi (Medical Genetics)

ABSTRACT

High level of activated or phosphorylated serine/threonine kinase Akt is commonly observed in aggressive breast cancer. Hence, the Akt signaling pathway has become a popular target for therapeutic interventions. Previously our lab discovered that phosphorylated Akt is co-expressed with a transcription/translation factor called the Y-box Binding Protein-1 (YB-1) and that Akt phosphorylates YB-1 at Ser102 in vitro. It was also found that YB-1, but not the YB-1 mutant in which Ser102 is mutated to alanine (YB-1A102), enhanced breast cancer cell growth. Since YB-1 was originally isolated as a DNA binding protein that interacts with the regulatory elements of the epidermal growth factor receptor (EGFR), we addressed the possibility that phosphorylated YB-1 stimulates breast cancer cell growth by upregulating EGFR expression. First, we demonstrated that YB-1 was phosphorylated through the PI3K/Akt pathway ex vivo by immunoprecipitation and western blotting. We then illustrated that loss of Ser102 affects the nuclear translocation of YB-1, implying that Akt may also regulate YB-1 nuclear trafficking. By exogenously expressing YB-1 or YB-1A102 in breast cancer cell lines we showed that YB-1 but not YB-1A102 induced the levels of EGFR mRNA and protein. It was revealed that YB-1 bound to the -2 kb of the EGFR promoter by chromatin immunoprecipitation. Interestingly, disruption of Ser102 prevented YB-1 from interacting with the first 1 kb of the EGFR promoter, indicating that binding to this region by YB-1 is regulated by the PI3K/Akt signaling. We then demonstrated that mutation of Ser102 perturbed YB-1 from activating the -1 kb of the EGFR promoter by luciferase reporter assays. Finally, since activation of Akt depends on 3-phosphoinositide-dependent protein kinase-1 (PDK1), we examined the potential of a PDK1 inhibitor, OSU-03012, to inhibit the functions of YB-1. It was found that OSU-03012 blocked YB-1 nuclear translocation and binding to the -1 kb promoter of EGFR. Together these results suggested that activation of the PI3K/Akt pathway leads to phosphorylation of YB-1 at Ser102, resulting in up-regulation of EGFR gene expression. Here we propose that Akt, YB-1, and EGFR may all function in the same pathway to promote breast cancer cell growth.

SELECTED PUBLICATIONS

To K, Stratford A, Wu J, et. al. 3-phosphoinositide-dependent kinase-1 inhibitor, OSU-03012, prevents YB-1 from binding to the EGFR promoter in human breast cancer cell lines. Manuscript in preparation.

Wu J, et. al. Disruption of the Y-box binding protein-1 results in suppression of the epidermal growth factor receptor and HER-2. Cancer Research. 2006. May 1;66(9):4872-9

Sutherland BW, Kucab J, Wu J, et. al. Akt phosphorylates the Y-box binding
protein-1 at Ser102 located in the cold shock domain and affects the anchorage-independent growth of breast cancer cells. Oncogene. 2005. Jun
16;24(26):4281-92

SELECTED PRESENTATIONS

Wu J, et. al. The expression of epidermal growth factor receptors in breast carcinoma is controlled by the Y-box binding protein-1 (YB-1) through the PI3K/Akt signaling. 2006. Canadian Breast Cancer Research Association: Reasons for Hope Conference.

Wu J, et. al. The expression of epidermal growth factor receptors in breast
carcinoma is controlled by the Y-box binding protein-1 (YB-1) through the
PI3K/Akt signaling. 2006. Keystone Symposia: Signaling Networks.

Wu J, et. al. The expression of epidermal growth factor receptors in breast
carcinoma is controlled by the Y-box biding protein-1 (YB-1). 2005. AACR
Special Conference in Cancer Research: Advances in breast cancer research: Genetics, biology, and clinical applications.

Wu J, et. al. The expression of epidermal growth factor receptors in breast
carcinoma is controlled by the Y-box biding protein-1 (YB-1). 2005. BC Cancer Agency’s Annual Cancer Conference. *This presentation received a “First Prize” in the poster competition*

Wu J, et. al. The role of YB-1 in Pi3K/Akt signaling pathway in breast cancer
growth. 2005. Students Research Forum, BC Research Institute for Children’s and Women’s Health. *This presentation received a “Division Finalist” in the poster competition*

Visser JH, Wu J, et. al. The cytotoxic effect of celecoxib and its analogues,
OSU-03012 and OSU-03013, on pediatric rhabdomyosarcoma cell lines. 2004. United Kingdom Children’s Cancer Study Group (UKCCSG) Scientific Meeting.

AWARDS

2005 Graduate Studentship. BC Research Centre for Children’s and Women’s Health (BCRICHW)
2005 Poster Award First Prize. BC Cancer Research Centre Annual Conference
2004 Poster Award Division Finalist. Student Research Forum, BCRICWH

GRADUATE STUDIES

Field of Study: Molecular Biology, Breast Cancer, Medical Genetics

Courses:
MEDG520 Advanced Human Molecular Genetics, Dr. A. Brooks-Wilson
MEDG521 Molecular & Cellular Biology of Cancer, Dr. P. Hoodless
MEDG530 Advanced Human Genetics, Dr. L. Clarke
MEDG545 Current Topics in Medical Genetics Research, Dr. R Kay & Dr. P. Hoodless
MEDG548 Directed Studies, Dr. R. McMaster
MEDG 549 M.Sc. Thesis, Dr. C. Brown

Joyce Wu- MSc Defense program- pdf