Regulation of PERLECAN and 2OST Expression in Prostate Cancer Progression by Stress-activated Transcription Factors

Abstract

Heparan sulfate proteoglycans modulate many of the growth factor pathways that drive prostate cancer progression. Prior to being secreted into the extracellular matrix, the covalently attached HS chains are modified by sulfation which has been shown to increase the affinity of binding growth factors. The specific HSPG that I focus on in this dissertation is Perlecan (Pln). Previously, our group along with collaborators found that 54 percent of prostate cancer tumors had upregulated levels of Pln protein that correlated with increasing Gleason score [93]. The LNCaP-DU145-LN4 cell line series is introduced as a model for this subset of tumors because Pln levels increase 50-fold as the cells become more metastatic. It was found that three stress-induced transcription factors, HIF1α, NFkB, and ATF2, all stimulate Pln expression. ChIP analysis reveals that HIF1α and NFkB directly bind the Pln promoter while ATF2 does not. The ROS-generating NADPH Oxidase and the ROS-inducible p38 MAPK were also found to induce Pln expression. To address the subset of prostate cancer tumors that reach metastasis without upregulation of Pln, I focused on the 2-o-sulfotransferase enzyme and its effect on proliferation and invasion in the LNCaP-C4-2B cell model which does not show upregulation of Perlecan expression. 2OST RNAi resulted in a significant decrease in proliferation in each line of the series. 2OST RNAi in highly metastatic C4-2B cells caused a significant decrease in cell invasion. Cells with decreased levels of 2OST had increased accumulation of actin and E-cadherin suggesting the possible formation of adherens junctions. I also found that expression of 2OST increases four-fold as cells become more metastatic. I found HIF1α and ATF2 act in a direct manner while NFkB acts indirectly to stimulate 2OST expression. In summary, I have analyzed the effect of cellular stress on the expression of the Pln and 2OST genes and investigated the phenotype of 2OST knockdown in metastatic prostate cancer cells. These studies lead me to propose that the tumor stress response is necessary for prostate cancer progression due to the role of stress in the upregulation of extracellular HS that is required for growth factor signaling and metastatic behaviors.