Date of Award

5-1-2014

Degree Type

Dissertation

University or Center

Clark Atlanta University(CAU)

Degree Name

Ph.D.

Biological Sciences

First Advisor

Dr. Valerie Marah, Ph.D.

Abstract

Epithelial-mesenchymal transition (EMT) is a process by which cancer cells acquire mesenchymal properties, such as induction of vimentin, while epithelial-associated genes like E-cadherin are lost. This enables the cells to be more metastatic. Factors that can induce EMT include growth factors like transforming growth factor -P (TGF-P) and epidermal growth factor (EGF), and transcription factors like Snail. Snail-induced EMT promotes migration and invasion and we hypothesized that this may be mediated by urokinase (uPA) and its receptor (uPAR) activities. LNCaP, 22Rvl and ARCaP human prostate cancer (CaP) cells stably transfected with constitutively active Snail displayed increased cell invasion as compared to the empty vector control (Neo). Superarray analysis revealed an up-regulation in uPA and uPAR RNA expression in Snailtransfected ARCaP cells as compared to Neo control. Next, the protein expression levels of Snail, uPA, and uPAR were measured by western blot analysis in various prostate cancer cell lines which showed that overexpression of Snail increased uPA and uPAR protein levels. The activity of uPA in conditioned media was measured using an ELISA assay which revealed that uPA activity was elevated in LNCaP, 22Rvl and ARCaP cells overexpressing Snail. Additionally, transient silencing of uPAR in ARCaP cells overexpressing Snail using siRNA resulted in abrogation of Snail-mediated invasion. Snail overexpression was associated with increased ERK activity and antagonism of this activity with MAPK inhibitor, UO126, inhibited cell invasion and decreased uPA activity. Therefore, Snail-mediated cell invasion in human prostate cancer cells may occur via the regulation of uPA/ uPAR and the MAPK signaling pathways.

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