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Background: Zinc accumulation diminishes early in the course of prostate malignancy and continues to decline during progression toward hormone-independent growth. In contrast, constitutive levels of NF-kappaB activity increase during progression of prostate cells toward greater tumorigenic potential. We have reported previously that physiological levels of zinc suppress NF-kappaB activity in prostate cancer cells and reduce expression of pro-angiogenic and pro-metastatic cytokines VEGF, IL-6, IL-8, and MMP-9 associated with negative prognostic features in prostate cancer., Methods: Intracellular zinc levels were examined by atomic absorption spectroscopy. NF-kappaB activity was examined by TransAm and Luciferase reporter assays, and Western blot analysis of p50 nuclear translocation. VEGF, IL-6 and IL-8 levels were assessed by ELISA., Results: Selective zinc deficiency induced by the membrane-permeable zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl)-ethylenediamine (TPEN) increases activation of NF-kappaB and up-regulates expression of the NF-kappaB controlled pro-angiogenic and pro-metastatic cytokines VEGF, IL-6 and IL-8 in androgen-independent PC-3 and DU-145 prostate cancer cells. Pre-incubation with I kappaB alpha dominant mutant adenovirus efficiently blocks expression of these cytokines in zinc deficient cells indicating that the observed effects are NF-kappaB dependent., Conclusions: Our findings suggest that zinc deficiency may contribute to the tumor progression via augmented expression of the NF-kappaB-dependent pro-tumorigenic cytokines., ((c) 2008 Wiley-Liss, Inc.)

Purpose: Intracellular zinc levels and expression of the zinc uptake transporter, hZIP1, are markedly down-regulated in prostate adenocarcinomatous tissue compared with normal prostate tissue. Our previous studies have shown that zinc inhibits nuclear factor-kappaB (NF-kappaB) activity and reduces the malignant potential of prostate cancer cells in vitro. In this study, we investigate the functional effect of hZIP1 overexpression on NF-kappaB activity and tumorigenic potential in human prostate cancer cells in vitro and in vivo., Experimental Design: NF-kappaB activity in PC-3 prostate cancer cells was examined by Western blotting and luciferase assay. ELISA was used to examine the expression of tumorigenic cytokines. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, adhesion, and invasiveness assays were used to assess the malignant potential of tumor cells. The effect of hZIP1 overexpression on prostate tumor progression in vivo was assessed using a xenograft model., Results: Overexpression of the hZIP1 transporter in PC-3 cells results in significant inhibition of NF-kappaB activity in the presence of physiologic levels of zinc. NF-kappaB inhibition coincides with a reduction in expression of several NF-kappaB controlled prometastatic and antiapoptotic factors as well as sensitization of the cells to etoposide and tumor necrosis factor-mediated apoptosis-inducing ligand-mediated cell death. Moreover, overexpression of the hZIP1 transporter induces regression of prostate tumor growth in a xenograft model., Conclusions: Our results show that hZIP1 overexpression has a functional effect on the malignant potential of prostate cancer cells via inhibition of NF-kappaB-dependent pathways and support the concept that hZIP1 may function as a tumor suppressor gene in prostate cancer.

Background: NF-kappaB and AP-1 transcriptional factors contribute to the development and progression of prostate malignancy by regulating the expression of genes involved in proliferation, apoptosis, angiogenesis, and metastasis., Methods: NF-kappaB and AP-1 activities were examined by TransAm assay. Cytokines levels were assessed by ELISA. ICAM-1 and gp130 expression was examined by flow cytometry. Cell adhesion was examined by the ability of cells to adhere to fibronectin-coated plates. Cell viability was determined by propidium iodide staining., Results: Treatment with alpha-tocopherol succinate (VES) inhibits NF-kappaB but augments AP-1 activity, reduces expression of IL-6, IL-8, and VEGF, suppresses cell adhesion, ICAM-1 and gp130 expression in androgen-independent PC-3, DU-145, and CA-HPV-10 cells. VES supplementation also decreases the expression of anti-apoptotic XIAP and Bcl-X(L) proteins and sensitizes androgen-dependent LNCaP cells to androgen deprivation., Conclusions: Our findings propose a potential mechanism of VES-mediated anti-tumor activity and support the role of vitamin E analogs as potential chemopreventative agents against prostate cancer., ((c) 2007 Wiley-Liss, Inc.)

Nuclear factor-kappaB (NF-kappaB) and AP-1 nuclear transcriptional factors regulate expression of multiple genes involved in tumor growth, metastasis and angiogenesis; however, the relative contribution of each factor to cancer initiation and progression has not been established. Prostate carcinogenesis involves transformation of normal zinc-accumulating epithelial cells to malignant cells that do not accumulate zinc. Whereas activation of both NF-kappaB and AP-1 has been implicated in prostate cancer development and growth, we tested the relative effects of zinc supplementation on these important transcriptional factors. Herein, we demonstrate that physiological levels of zinc inhibit NF-kappaB but augment activities of AP-1 in DU-145 and PC-3 human prostate cancer cells. Additionally, we show that chelation of zinc with membrane-permeable zinc chelator, N,N,N',N',-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN) abolishes this effect. We further propose a potential mechanism for this observation by demonstrating that zinc supplementation induces phosphorylation of the members of three major MAPK subfamilies regulating AP-1 and NF-kappaB activation (ERK 1/2, JNK and p38) while blocking TNF-alpha-mediated degradation of the inhibitory subunit I kappa B alpha and nuclear translocation of RelA in prostate cancer cells. VEGF, IL-6, IL-8 and MMP-9 are major pro-angiogenic and pro-metastatic molecules whose promoter regions contain binding sites for both NF-kappaB and AP-1. These cytokines have been associated with negative prognostic features in prostate cancer. We demonstrate that treatment of human prostate cancer cell lines with zinc reduces expression of VEGF, IL-6, IL-8 and MMP-9. We further show that zinc reduces expression of intercellular adhesion molecule-1 and functionally suppresses tumor cell invasiveness and adhesion. Therefore, the ability of zinc supplementation to inhibit NF-kappaB supercedes zinc-mediated activation of AP-1 family members. Upregulation of intracellular zinc levels may have important implications for inhibiting the angiogenic and metastatic potentials of malignant cells, predominantly through suppression of NF-kappaB signaling.