Date of Award

Spring 5-22-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Science

First Advisor

Shafiq A. Khan Ph.D.

Second Advisor

Jaideep Chaudhary Ph.D.

Third Advisor

Valerie Odero-Marah Ph.D.

Abstract

Activator Protein-1(AP-1) family plays a central role in the transcriptional regulation of many genes that are associated with cell proliferation, migration, metastasis, and survival. Transforming growth factor beta (TGF-β) is a multi-functional regulatory cytokine that regulates many aspects of cellular function, including cellular proliferation, migration, and survival. This study investigated the role of FOS proteins in TGF-β signaling in prostate cancer cell proliferation, migration, and invasion. DU145 and PC3 prostate cancer cells were exposed to TGF-β1 at varying time and dosage, RT-PCR, western blot and immunofluorescence analyses were used to determine TGF-β1 effect on FOS mRNA and protein expression levels as well as FosB sub-cellular localization. Transient silencing of FOS protein was used to determine their role in cell proliferation, migration and invasion. Our data showed that FOS mRNA and proteins were differentially expressed in human prostate epithelial (RWPE-1) and prostate cancer cell lines (LNCaP, DU145, and PC3). TGF-β1 induced the expression of FosB at both the mRNA and protein levels in DU145 and PC3 cells, whereas cFos and Fra1 were unaffected and Fra2 protein expression increased in PC3 cell only. Immunofluorescence analysis showed an increase in the accumulation of FosB protein in the nucleus of PC3 cells after treatment with exogenous TGF-β1. Selective knockdown of endogenous FosB by specific siRNA did not have any effect on cell proliferation in PC3 and DU145 cells. However, basal and TGF-β1-and EGF- induced cell migration was significantly reduced in DU145 and PC3 cells lacking endogenous FosB. TGF-β1- and EGF-induced cell invasion were also significantly decreased after FosB knockdown in PC3 cells. Transient silencing of Fra2 resulted in decrease in cell proliferation in PC3 cells whereas transient silencing of cFos resulted in an increase in cell number in PC3 cells. And lastly, TGF-β1 reduced FosB: cJun dimerization; cJun knockdown increased cell migration in PC3 cells and its over expression decreased cell migration in DU145 cells. Our data suggest that FosB is required for migration and invasion in prostate cancer cells. We also conclude that TGF-β1 effect on prostate cancer cell migration and invasion may be mediated through the induction of FosB.