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RhoA-induced signaling pathways and gene expression patterns are being studied to determine the mechanisms of human prostate cancer cell invasion, a necessary step for distant spread. Highly invasive PC-3 prostate cancer cells demonstrated increased RhoA and NF-kappaB signaling activity and expression of several genes including tissue factor, interleukin 8, matrix metalloproteinase MMP-1, vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-beta. NF-kappaB, activator protein (AP-1) complex and other transcription factors may regulate genes leading to invasion and aggressive prostate cancer growth. The purpose of this study was to test the hypothesis that increased RhoA activity induces NF-kappaB activity and expression of genes affecting prostate cancer cell growth and invasive behavior. Stable expression of constitutively active RhoA Q63E or treatment of cells with micromolar concentrations of serum component lysophosphatidic acid (LPA) increased RhoA and NF-kappaB activities and Matrigel basement membrane invasion. Further, treatment of highly invasive PC-3 cells with LPA induced cellular tissue factor expression and secretion of vascular endothelial growth factor (VEGF) into the cell culture supernatant. Conversely, inhibition of RhoA activity by genetic and pharmacologic manipulation demonstrated that its activity was necessary for increased NF-kappaB activity and increased prostate cancer cell invasion. The LPA-induced NF-kappaB activation and prostate cancer cell invasion was also partially inhibited by pyrrolidine dithiocarbamate (PDTC) or lactacystin treatment and completely blocked by protein kinase C inhibitors and calcium chelator BAPTA. These findings point to a model where increased RhoA activity leads to increased NF-kappaB activity and expression of genes regulating prostate cancer cell growth and invasion. The role of RhoA and Rho-induced genes for in vivo prostate cancer cell invasion and metastasis and clinical prostate cancer progression are the focus of continuing investigations. These studies have potential to reveal markers of clinically aggressive prostate cancer behavior and novel molecular targets to control prostate cancer spread. This work is supported by a Department of Defense New Investigator Grant DAMD17-02-1-0162 and a Research Career Development Award from the National Cancer Institute Prostate S.P.O.R.E. P50 CA90386 at the Northwestern University Robert H. Lurie Comprehensive Cancer Center.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]