Selenoprotein-P is down-regulated in prostate cancer, which results in lack of protection against oxidative damage.

BACKGROUND: Oxidative stress plays a role in prostate cancer (PrCa) initiation and development. Selenoprotein-P (SepP; a protein involved in antioxidant defence) mRNA levels are down-regulated in PrCa. The main goal of our study was to assess whether SepP protects prostate cells from reactive oxygen species (ROS) in prostate carcinogenesis. METHODS: Modification of SepP levels and ROS conditions in C3(1)/Tag-derived cell lines representing prostate epithelial neoplasia (PIN) lesions (Pr-111, with high SepP expression); and invasive tumors (Pr-14, with very low SepP expression). RESULTS: Both Pr-111 and Pr-14 cells express ApoER2 (SepP receptor), which suggests that they may uptake SepP. Pr-14 cells had much higher ROS levels than Pr-111 cells and were highly sensitive to H(2)O(2)-mediated cytotoxicity. When SepP mRNA levels were knocked down with siRNAs in Pr-111 cells, a significant increase in ROS and cell growth inhibition upon H(2)O(2) exposure was found. Subsequent administration of purified SepP in the culture medium of these cells was able to rescue the original phenotype. Similarly, administration of SepP to Pr-14 cells was able to reduce ROS concentrations. Administration of flutamide decreased SepP mRNA levels whereas dihydrotestosterone or synthetic androgens induced SepP expression, indicating the importance of androgens for SepP expression. Immunohistochemical analysis using a PrCa tissue microarray further revealed that SepP protein was reduced in 60.8% prostate tumors compared to benign prostates. CONCLUSIONS: Levels of SepP in prostate cells determine basal ROS levels and sensitivity to H(2)O(2)-induced cytotoxicity. Deregulation of SepP during prostate carcinogenesis may increase free radicals, thus promoting tumor development and de-differentiation.

Repetitive nicotine exposure leads to a more malignant and metastasis-prone phenotype of SCLC: a molecular insight into the importance of quitting smoking during treatment.

Cigarette smoking is strongly correlated with the onset of lung cancer. Nicotine, a major component in cigarette smoke, has been found to promote tumor growth and angiogenesis, as well as protect cancer cells from apoptosis. Among all lung cancer cases, small cell lung cancer (SCLC) is found almost exclusively in smokers; metastasis and chemoresistance are the main reasons for the high mortality rates associated with SCLC. Retrospective studies have shown that patients with tobacco-related cancers who continue to smoke after their diagnosis display lower response rates and a shorter median survival compared with those who stop smoking. In the current work, we examined the effects of acute and repetitive exposure to nicotine, in the concentrations found in the lungs of active smokers, on the malignant properties of N417 SCLC cells in vitro. We observed that repetitive nicotine exposure induced a neuronal-like appearance in N417 cells along with increased adhesion to the extracellular matrix and chemoresistance. These changes were accompanied by enhanced migration through collagen matrices and adhesion to and transmigration across lymphatic endothelial cell monolayers. SCLC differentiation reverted after cessation of nicotine exposure. Here, we provide evidence for the leading role of the CXCR4/CXCL12 axis in these phenomena. Finally, we show how nicotine-differentiated N417 cells produced bigger and more vascularized tumors in mice, with lower apoptotic rates, than their nondifferentiated counterparts. In short, these findings identify the mechanisms through which nicotine increases SCLC malignancy and provide further evidence that CXCR4 is a potential anticancer target for nicotine-associated SCLC.

VEGF elicits epithelial-mesenchymal transition (EMT) in prostate intraepithelial neoplasia (PIN)-like cells via an autocrine loop.

Vascular endothelial growth factor (VEGF) is overexpressed during the transition from prostate intraepithelial neoplasia (PIN) to invasive carcinoma. We have mimicked such a process in vitro using the PIN-like C3(1)/Tag-derived Pr-111 cell line, which expresses low levels of VEGF and exhibits very low tumorigenicity in vivo. Elevated expression of VEGF164 in Pr-111 cells led to a significant increase in tumorigenicity, invasiveness, proliferation rates and angiogenesis. Moreover, VEGF164 induced strong changes in cell morphology and cell transcriptome through an autocrine mechanism, with changes in TGF-beta1- and cytoskeleton-related pathways, among others. Further analysis of VEGF-overexpressing Pr-111 cells or following exogenous addition of recombinant VEGF shows acquisition of epithelial-mesenchymal transition (EMT) features, with an increased expression of mesenchymal markers, such as N-cadherin, Snail1, Snail2 (Slug) and vimentin, and a decrease in E-cadherin. Administration of VEGF led to changes in TGF-beta1 signaling, including reduction of Smad7 (TGF-beta inhibitory Smad), increase in TGF-betaR-II, and translocation of phospho-Smad3 to the nucleus. Our results suggest that increased expression of VEGF in malignant cells during the transition from PIN to invasive carcinoma leads to EMT through an autocrine loop, which would promote tumor cell invasion and motility. Therapeutic blockade of VEGF/TGF-beta1 in PIN lesions might impair not only tumor angiogenesis, but also the early dissemination of malignant cells outside the epithelial layer.

Methylseleninic acid enhances the effect of etoposide to inhibit prostate cancer growth in vivo.

New therapeutic agents are needed for the treatment of androgen-independent prostate cancer (PrCa). We have investigated the effect of methylseleninic acid (MSA) on tumor stage-specific prostate cells derived from the C3 (1)/Tag model for PrCa: Pr111, a slow-growing and nontumorigenic cell line isolated from a prostate intraepithelial neoplasia lesion; Pr14, a tumorigenic line derived from a primary tumor; and Pr14C1, a sub-clone of Pr14 explanted from a lung metastasis. We demonstrate that MSA strongly inhibits cell growth and induces apoptosis in C3 (1)/Tag tumor cells, in a dose-dependent manner. A decrease in phosphorylated ERK1/2 and AKT was also found in tumor cells, but not in Pr111. Microarray analysis using affymetrix showed that the number of genes with an altered expression in tumor cells is significantly higher (p < 0.01) than in nontumoral cells. Pathways analyses revealed a decrease in the expression of genes involved in metabolism (Fabp5, Cyba), signal transduction (ERK, AKT), angiogenesis (neuropilin-1, Flt-4) and transcription (cAMP response element-binding protein) in tumor cells. The expression of neuropilin-1, a protein involved in VEGF signaling and tumor angiogenesis, was 97-fold repressed in Pr14 cells treated with MSA. Combination treatments using low doses of etoposide or taxotere (docetaxel), plus low doses of MSA revealed a strong enhancement of cell growth inhibition and apoptosis in tumor cells. Our in vivo studies using Pr14 cells xenografted into nude mice demonstrated that MSA significantly enhances the chemotherapeutical effect of etoposide, resulting in 78.3% tumor growth inhibition. These results suggest that MSA could be used against PrCa to enhance the effect of etoposide.

Prostate cancer and the genomic revolution: Advances using microarray analyses.

The emerging technology of microarray analysis allows the establishment of molecular portraits of prostate cancer and the discovery of novel genes involved in the carcinogenesis process. Many novel genes have already been identified using this technique, and functional analyses of these genes are currently being tested. The combination of microarray analysis with other recently developed high-throughput techniques, such as proteomics, tissue arrays, and gene promoter-methylation, especially using tissue microdissection methods, will provide us with more comprehensive insights into how prostate cancer develops and responds to gene-targeted therapies. Animal models of prostate cancer are being characterized by high throughput techniques to better define the similarities and differences between those models and the human disease, and to determine whether particular models may be useful for specific targeted therapies in pre-clinical studies. Although profiling of mRNA expression provides important information of gene expression, the development of proteomic technologies will allow for an even more precise global insight into cellular signaling and structural alterations during prostate carcinogenesis. Not only will the "omic" revolution change basic science, but it will lead to a new era of molecular medicine.

Gene expression profiling identifies IL-13 receptor alpha 2 chain as a therapeutic target in prostate tumor cells overexpressing adrenomedullin.

Human adrenomedullin (AM) is a 52 amino acid peptide, which shares homology with the calcitonin gene-related peptide. Overexpression of AM in the prostate carcinoma cell line PC-3 results in growth inhibition with a 20% (for human AM) and 35% (for rat AM) increase in doubling time compared to parental or mock-transfected cells. We demonstrate by gene expression profiling that AM overexpression results in the dysregulation of approximately 100 genes. Examples of such genes include many involved in the formation of the cytoskeleton, cell adhesion and the extracellular matrix, as well as regulators of the cell cycle and apoptosis, cytokines and transcription factors. Several genes related to cell growth arrest, such as GADD45, IGF-BP6 and RUNX-3, are upregulated by AM. Interestingly, interleukin-13 receptor alpha 2 (IL-13R alpha 2) transcripts were significantly increased in clones overexpressing AM, which was confirmed by semiquantitative RT-PCR analysis. In addition, PC-3 cells treated with AM showed an overexpression of IL-13R alpha 2, which was abolished when cells were preincubated with an anti-AM blocking antibody. When PC-3 cells overexpressing AM and the IL-13R alpha 2 were treated with the highly specific IL13-PE38 cytotoxin, which binds to this receptor, a concentration-dependent inhibition of protein synthesis was observed. The IC(50) (concentration of cytotoxin inhibiting protein synthesis by 50%) ranged from 1 to 4 ng/ml. This cytotoxicity was specific as it was neutralized by the excess of IL-13 and confirmed by clonogenic assays. This study describes a novel AM-induced mechanism of tumor sensitization through the upregulation of functional IL-13R alpha 2 chain, an ideal target for the highly specific recombinant chimeric cytotoxin IL13-PE38.