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Transcriptome analyses in normal prostate epithelial cells following exposure to low-dose cadmium

ABSTRACT: BACKGROUND: Cadmium is implicated in prostate carcinogenesis, but its oncogenic action remains unclear. OBJECTIVES: In this study we aimed to decipher changes in cell growth and the transcriptome in an immortalized human normal prostate epithelial cell line (NPrEC) following exposure to low-dose Cd. METHODS: Synchronized NPrEC cells were exposed to different doses of Cd and assayed for cell viability and cell-cycle progression. We investigated changes in transcriptome by global profiling and used Ingenuity Pathways Analysis software to develop propositions about functional connections among differentially expressed genes. A neutralizing antibody was used to negate the effect of Cd-induced up-regulation of tumor necrosis factor (TNF) in NPrEC cells. RESULTS: Exposure of NPrEC to 2.5 μM Cd enhanced cell viability and accelerated cell-cycle progression. Global expression profiling identified 48 genes that exhibited ≥ 1.5-fold changes in expression after 4, 8, 16, and 32 hr of Cd treatment. Pathway analyses inferred a functional connection among 35 of these genes in one major network, with TNF as the most prominent node. Fourteen of the 35 genes are related to TNF, and 11 exhibited an average of > 2-fold changes in gene expression. Real-time reverse transcriptase-polymerase chain reaction confirmed the up-regulation of 7 of the 11 genes (ADAM8, EDN1, IL8, IL24, IL13RA2, COX2/PTGS2, and SERPINB2) and uncovered a 28-fold transient increase in TNF expression in Cd-treated NPrEC cells. A TNF-neutralizing antibody effectively blocked Cd-induced elevations in the expression of these genes. CONCLUSIONS: Noncytotoxic, low-dose Cd has growth-promoting effects on NPrEC cells and induces transient overexpression of TNF, leading to up-regulation of genes with oncogenic and immunomodulation functions. KEY WORDS: carcinogenesis, cytokine, global expression profiling, heavy metals, immune response, inflammation, Ingenuity Pathway Analysis, knowledge-based analysis, prostate cancer.

ORGANISM(S): Homo sapiens

PROVIDER: GSE9951 | GEO | 2008/03/01

SECONDARY ACCESSION(S): PRJNA103955

REPOSITORIES: GEO

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Project description:BACKGROUND: Cadmium (Cd) is implicated in prostate carcinogenesis but its oncogenic action remains unclear. OBJECTIVES: This study aims to decipher changes in cell growth and the transcriptome in an immortalized human normal prostate epithelial cell line (NPrEC) following exposure to low-dose Cd. METHODS: Synchronized NPrEC cells were exposed to different doses of Cd and assayed for cell viability and cell-cycle progression. Temporal changes in transcriptome were investigated by global profiling. Ingenuity Pathways Analyses were used to develop propositions about functional connections among differentially expressed genes. A neutralizing antibody was used to negate the effect of Cd-induced upregulation of TNF in NPrEC. RESULTS: Exposure of NPrEC to 2.5 microM of Cd enhanced cell viability and accelerated cell-cycle progression. Global expression profiling identified 48 genes that exhibited â?¥1.5-fold changes in expression after 4, 8, 16 and 32 hr of Cd treatment. Pathway analyses inferred a functional connection among 35 of these genes in one major network with TNF as the most prominent node. Fourteen out of the 35 genes in the network are related to TNF with 11 exhibited an average of â?¥2-fold changes in gene expression. Real-time RT-PCR confirmed the upregulation of 7 of the 11 genes (ADAM8, EDN1, IL8, IL24, IL13RA2, COX2/PTGS2 and SERPINB2) and uncovered a 28-fold transient increase in TNF expression in Cd-treated NPrEC. A TNF-neutralizing antibody effectively blocked Cd-induced elevations in the expression of these genes. CONCLUSIONS: Non-cytotoxic, low-dose Cd has growth-promoting effects on NPrEC and induces transient overexpression of TNF, leading to upregulation of genes with oncogenic and immunomodulation functions. Experiment Overall Design: A total of 19 samples were analyzed, each experimental condition having two biological replicates, except Cadmium 4hr which has only 1 sample. Cadmium-treated and control samples were taken at 0, 4, 8, 16, and 32 hours.

Project description:The androgen receptor (AR) is an androgen-activated nuclear receptor. The androgen signaling axis is critical in all stages of prostate cancer, although the mechanism by which it contributes to tumorigenesis remains unclear. Mutations in the AR have been detected in prostate tumors; one such mutant, E231G, exhibits increased ligand sensitivity in the presence of specific cofactors. Mice with prostate-specific expression of AR-E231G invariably develop prostatic intraepithelial neoplasia (PIN) by 12 weeks, and metastatic prostate cancer by 52 weeks. To determine a potential mechanism of AR-driven tumorigenesis in AR-E231G mice, we compared gene expression profiles in prostates of 12 week old AR-E231G mice with another AR-variant mouse strain (AR-T857A) that does not develop tumors. Pathway classification of the 132 candidate genes differentially expressed in AR-E231G mouse prostates compared to AR-T857A mouse prostates revealed enrichment for groups important in prostate cancer, including “cancer,” “fatty acid metabolism” and “cell cycle” pathways. Two genes significantly upregulated in the AR-E231G model were Adm and Cited1. siRNA suppression of ADM and CITED1 expression by up to 63% and 79%, respectively, in LNCaP human prostate cancer cells, resulted in an approximate 1.8-fold increase in cell death. Cell proliferation was reduced by 35% when CITED1 mRNA expression was suppressed, but not significantly altered by ADM suppression. A gene signature set derived from this model was able to distinguish between primary Gleason grade 3 and Gleason grade 4 tumors (p=0.04237), and between human non-malignant and cancerous prostate in a test (p=0.02352) and validation cohort (p=7.53x10-9), highlighting the relevance of the AR-E231G model to the human disease. RNA was extracted from ventral prostate tissue from 12-week old AR-E231G and AR-T857A mice in FVB background. Pooled RNA from 3 mice per genotype were extracted using the RNeasy kit (Qiagen, Germantown, MD, USA), and 10 µg RNA was hybridized to a total of 2 Affymetrix Mouse Genome 430 2.0 chip® microarrays. Microarray data was normalized by Robust Multiarray Averaging. Probes with expression changes were identified using a fold-change cut-off of log1.5. Normalized microarray data was analysed using Ingenuity Pathways Analysis (IPA, Redwood City, CA, USA).

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Transcriptome analyses in normal prostate epithelial cells following exposure to low-dose cadmium

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