Vitamin E succinate inhibits human prostate cancer cell growth via modulating cell cycle regulatory machinery

Several epidemiological studies have demonstrated that vitamin E is a chemopreventative agent for prostate cancer. alpha-Tocopheryl succinate (VES), a derivative of vitamin E, effectively modulates prostate cancer cell growth. However, little is known about the mechanisms regarding this action. Here we show that VES causes human prostate cancer cell LNCaP arrest at G1 phase. This effect is accomplished through VES significantly decreasing expression of the cell cycle regulatory proteins cyclin D1, D3, and E, cdk2 and 4, but not cdk6. Furthermore, VES reduces cdk4 kinase activity, Rb phosphorylation, and cyclin E mRNA expression. Recently there is increasing interest in the protective effect of the VES and selenium combination on prostate cancer. Here we show that VES and selenium work through different mechanisms to exert their inhibitory effects on prostate cancer cells. Taken together, our studies suggest that VES-mediated prostate cancer cell G1/S arrest is a consequence of the regulation of multiple molecules of the cell cycle regulatory machinery.     

Microarray analysis of ageing-related signatures and their expression in tumors based on a computational biology approach

Ageing and cancer have been associated with genetic and genomic changes.The identification of common signatures between ageing and cancer can reveal shared molecular mechanisms underlying them.In this study,we collected ageing-related gene signatures from ten published studies involved in six different human tissues and an online resource.We found that most of these gene signatures were tissuespecific and a few were related to multiple tissues.We performed a genome-wide examination of the expression of these signatures in various human tumor types,and found that a large proportion of these signatures were universally differentially expressed among normal vs.tumor phenotypes.Functional analyses of the highly-overlapping genes between ageing and cancer using DAVID tools have identified important functional categories and pathways linking ageing with cancer.The convergent and divergent mechanisms between ageing and cancer are discussed.This study provides insights into the biology of ageing and cancer,suggesting the possibility of potential interventions aimed at postponing ageing and preventing cancer.     

Adenovirus-mediated delivery of human IFNgamma gene inhibits prostate cancer growth

Interferon gamma (IFNgamma) is regarded as a potent antitumor agent, but therapy with IFNgamma is hampered by its short half-life and significant side effects. We developed a replication defective adenovirus carrying the human IFNgamma gene and evaluated the effects of adenovirus-mediated IFNgamma (Ad-IFNgamma) gene transfer on human prostate cancer cell lines in vitro and on xenografts in vivo. Our results showed infection of prostate cancer cells with Ad-IFNgamma led to production of an active cytokine and resulted in an antiproliferative effect on the prostate cancer cells. Intratumoral injection of Ad-IFNgamma significantly inhibited the growth of DU-145 cell xenografts in vivo, while no significant toxicity effect was observed. RT-PCR analysis indicated transgene expression mainly enriched in tumors in vivo, and slightly distributed in livers. These findings suggest adenovirus-mediated IFNgamma gene transfer is a promising approach in the treatment of advanced prostate cancer.     

TFDP3 was expressed in coordination with E2F1 to inhibit E2F1-mediated apoptosis in prostate cancer

TFDP3 has been previously identified as an inhibitor of E2F molecules. It has been shown to suppress E2F1-induced apoptosis dependent P53 and to play a potential role in carcinogenesis. However, whether it indeed helps cancer cells tolerate apoptosis stress in cancer tissues remains unknown. TFDP3 expression was assessed by RT-PCR, in situ hybridization and immunohistochemistry in normal human tissues, cancer tissues and prostate cancer tissues. The association between TFDP3 and E2F1 in prostate cancer development was analyzed in various stages. Apoptosis was evaluated with annexin-V and propidium iodide staining and flow-cytometry. The results show that, in 96 samples of normal human tissues, TFDP3 could be detected in the cerebrum, esophagus, stomach, small intestine, bronchus, breast, ovary, uterus, and skin, but seldom in the lung, muscles, prostate, and liver. In addition, TFDP3 was highly expressed in numerous cancer tissues, such as brain-keratinous, lung squamous cell carcinoma, testicular seminoma, cervical carcinoma, skin squamous cell carcinoma, gastric adenocarcinoma, liver cancer, and prostate cancer. Moreover, TFDP3 was positive in 23 (62.2%) of 37 prostate cancer samples regardless of stage. Furthermore, immunohistochemistry results show that TFDP3 was always expressed in coordination with E2F1 at equivalent expression levels in prostate cancer tissues, and was highly expressed particularly in samples of high stage. When E2F1 was extrogenously expressed in LNCap cells, TFDP3 could be induced, and the apoptosis induced by E2F1 was significantly decreased. It was demonstrated that TFDP3 was a broadly expressed protein corresponding to E2F1 in human tissues, and suggested that TFDP3 is involved in prostate cancer cell survival by suppressing apoptosis induced by E2F1.     

Adrenomedullin inhibits prostate cancer cell proliferation through a cAMP-independent autocrine mechanism

Adrenomedullin (AM) is a multifunctional peptide expressed in the normal and malignant prostate, and in prostate cancer cells. To elucidate the potential role of AM in prostate cancer, we have transfected the human AM gene into PC-3, DU 145, and LNCaP prostate cancer cells. Northern blot, Western blot, and radioimmunoassay techniques confirmed an increase in the synthesis and secretion of the 6kDa mature peptide, in the AM-transfected clones. Proliferation and cell cycle assays demonstrated that AM overexpression inhibited cell proliferation in PC-3 and LNCaP cells through a G0/G1 cell cycle arrest, but not in DU 145 cells. In vivo growth assays also confirmed that, at least in PC-3, AM produced a very significant reduction of tumor volume. In addition, the three cell lines expressed the CL/RCP/RAMP-2 receptor complex by RT-PCR, which suggests that AM peptide acts through an autocrine loop in prostate cancer cells. Although cAMP elevation is the most common pathway involved in AM signalling, stimulation of PC-3, DU 145, and LNCaP with synthetic AM did not increase intracellular cAMP. However, short-term stimulation of PC-3 cells with synthetic AM increased ERK1/2 activation. On the contrary, long-term stimulation, or AM overexpression, caused a reduction in the basal activation of ERK1/2. In summary, our results demonstrate that AM (either overexpressed or exogenously added) causes an inhibition of prostate cancer cell growth. This inhibition does not depend on changes in intracellular cAMP levels, but may be related to ERK1/2 activation.     

WWOX suppresses prostate cancer cell progression through cyclin D1-mediated cell cycle arrest in the G1 phase

WW domain-containing oxidoreductase (WWOX) has been reported to be a tumor suppressor in multiple cancers, including prostate cancer. WWOX can induce apoptotic responses to inhibit tumor progression, and the other mechanisms of WWOX in tumor suppression have also been reported recently. In this study, we found significant down-regulation of WWOX in prostate cancer specimens and prostate cancer cell lines compared with the normal controls. In addition, an ectopically increased WWOX expression repressed tumor progression both in vitro and in vivo. Interestingly, overexpression of WWOX in 22Rv1 cells led to cell cycle arrest in the G1 phase but did not affect sub-G1 in flow cytometry. GFP-WWOX overexpressed 22Rv1 cells were shown to inhibit cell cycle progression into mitosis under nocodazole treatment in flow cytometry, immunoblotting and GFP fluorescence. Further, cyclin D1 but not apoptosis correlated genes were down-regulated by WWOX both in vitro and in vivo. Restoration of cyclin D1 in the WWOX-overexpressed 22Rv1 cells could abolish the WWOX-mediated tumor repression. In addition, WWOX impair c-Jun-mediated cyclin D1 promoter activity. These results suggest that WWOX inhibits prostate cancer progression through negatively regulating cyclin D1 in cell cycle lead to G1 arrest. In summary, our data reveal a novel mechanism of WWOX in tumor suppression.     

WWOX suppresses prostate cancer cell progression through cyclin D1-mediated cell cycle arrest in the G1 phase

WW domain-containing oxidoreductase (WWOX) has been reported to be a tumor suppressor in multiple cancers, including prostate cancer. WWOX can induce apoptotic responses to inhibit tumor progression, and the other mechanisms of WWOX in tumor suppression have also been reported recently. In this study, we found significant down-regulation of WWOX in prostate cancer specimens and prostate cancer cell lines compared with the normal controls. In addition, an ectopically increased WWOX expression repressed tumor progression both in vitro and in vivo. Interestingly, overexpression of WWOX in 22Rv1 cells led to cell cycle arrest in the G1 phase but did not affect sub-G1 in flow cytometry. GFP-WWOX overexpressed 22Rv1 cells were shown to inhibit cell cycle progression into mitosis under nocodazole treatment in flow cytometry, immunoblotting and GFP fluorescence. Further, cyclin D1 but not apoptosis correlated genes were down-regulated by WWOX both in vitro and in vivo. Restoration of cyclin D1 in the WWOX-overexpressed 22Rv1 cells could abolish the WWOX-mediated tumor repression. In addition, WWOX impair c-Jun-mediated cyclin D1 promoter activity. These results suggest that WWOX inhibits prostate cancer progression through negatively regulating cyclin D1 in cell cycle lead to G1 arrest. In summary, our data reveal a novel mechanism of WWOX in tumor suppression.     

Up-regulation of eEF1A2 promotes proliferation and inhibits apoptosis in prostate cancer

Background

eEF1A2 is a protein translation factor involved in protein synthesis, which possesses important function roles in cancer development. This study aims at investigating the expression pattern of eEF1A2 in prostate cancer and its potential role in prostate cancer development.

Methods

We examined the expression level of eEF1A2 in 30 pairs of prostate cancer tissues by using RT-PCR and immunohistochemical staining (IHC). Then we applied siRNA specifically targeting eEF1A2 to down-regulate its expression in DU-145 and PC-3 cells. Flow cytometer was used to explore apoptosis and Western-blot was used to detect the pathway proteins of apoptosis.

Results

Our results showed that the expression level of eEF1A2 in prostate cancer tissues was significantly higher compared to their corresponding normal tissues. Reduction of eEF1A2 expression in DU-145 and PC-3 cells led to a dramatic inhibition of proliferation accompanied with enhanced apoptosis rate. Western blot revealed that apoptosis pathway proteins (caspase3, BAD, BAX, PUMA) were significantly up-regulated after suppression of eEF1A2. More importantly, the levels of eEF1A2 and caspase3 were inversely correlated in prostate cancer tissues.

Conclusion

Our data suggests that eEF1A2 plays an important role in prostate cancer development, especially in inhibiting apoptosis. So eEF1A2 might serve as a potential therapeutic target in prostate cancer.     

Epigallocatechin-3-gallate (EGCG) inhibits PC-3 prostate cancer cell proliferation via MEK-independent ERK1/2 activation

Epigallocatechin-3-gallate (EGCG), a tea polyphenol, inhibits the proliferation of many cancer cell lines; however, the antiproliferative mechanism(s) are not well-characterized. The objective of this study is to identify the cellular signaling mechanism(s) responsible for the antiproliferative effects of EGCG in the PC-3 prostate cancer cell line. EGCG inhibited PC-3 cell proliferation in a concentration-dependent manner with an IC(50) value of 39.0 microM, but had no effect on the proliferation of a nontumorigenic prostate epithelial cell line (RWPE-1). Treatment of PC-3 cells with EGCG (0-50 microM) resulted in time and concentration-dependent activation of the extracellular signal-regulated kinase (ERK1/2) pathway. EGCG treatment did not induce ERK1/2 activity in RWPE-1 cells. The activation of ERK1/2 by EGCG was not inhibited using PD98059, a potent inhibitor of mitogen-activated protein kinase kinase (MEK), the immediate upstream kinase responsible for ERK1/2 activation; suggesting a MEK-independent signaling mechanism. Pretreatment of PC-3 cells with a phosphoinositide-3 kinase (PI3K) inhibitor partially reduced both EGCG-induced ERK1/2 activation and the antiproliferative effects of this polyphenol. These results suggest that ERK1/2 activation via a MEK-independent, PI3-K-dependent signaling pathway is partially responsible for the antiproliferative effects of EGCG in PC-3 cells.     

MALDI mass spectrometry in prostate cancer biomarker discovery

Matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry (MS) is a highly versatile and sensitive analytical technique, which is known for its soft ionisation of biomolecules such as peptides and proteins. Generally, MALDI MS analysis requires little sample preparation, and in some cases like MS profiling it can be automated through the use of robotic liquid-handling systems. For more than a decade now, MALDI MS has been extensively utilised in the search for biomarkers that could aid clinicians in diagnosis, prognosis, and treatment decision making. This review examines the various MALDI-based MS techniques like MS imaging, MS profiling and proteomics in-depth analysis where MALDI MS follows fractionation and separation methods such as gel electrophoresis, and how these have contributed to prostate cancer biomarker research. This article is part of a Special Issue entitled: Biomarkers: A Proteomic Challenge.     

Stemness markers characterize IGR-CaP1, a new cell line derived from primary epithelial prostate cancer

Deciphering molecular pathways involved in the early steps of prostate oncogenesis requires both in vitro and in vivo models derived from human primary tumors. However the few recognized models of human prostate epithelial cancer originate from metastases. To date, very few models are proposed from primary tumors and immortalizing normal human prostate cells does not recapitulate the natural history of the disease. By culturing human prostate primary tumor cells onto human epithelial extra-cellular matrix, we successfully selected a new prostate cancer cell line, IGR-CaP1, and clonally-derived subclones. IGR-CaP1 cells, that harbor a tetraploid karyotype, high telomerase activity and mutated TP53, rapidly induced subcutaneous xenografts in nude mice. Furthermore, IGR-CaP1 cell lines, all exhibiting negativity for the androgen receptor and PSA, express the specific prostate markers alpha-methylacyl-CoA racemase and a low level of the prostate-specific membrane antigen PSMA, along with the prostate basal epithelial markers CK5 and CK14. More importantly, these clones express high CD44, CD133, and CXCR4 levels associated with high expression of α2β1-integrin and Oct4 which are reported to be prostate cancer stemness markers. RT-PCR data also revealed high activation of the Sonic Hedgehog signalling pathway in these cells. Additionally, the IGR-CaP1 cells possess a 3D sphere-forming ability and a renewal capacity by maintaining their CSC potential after xenografting in mice. As a result, the hormone-independent IGR-CaP1 cellular clones exhibit the original features of both basal prostate tissue and cancer stemness. Tumorigenic IGR-CaP1 clones constitute invaluable human models for studying prostate cancer progression and drug assessment in vitro as well as in animals specifically for developing new therapeutic approaches targeting prostate cancer stem cells.     

Statistical issues and methods for meta-analysis of microarray data: a case study in prostate cancer

With the proliferation of related microarray studies by independent groups, a natural step in the analysis of these gene expression data is to combine the results across these studies. However, this raises a variety of issues in the analysis of such data. In this article, we discuss the statistical issues of combining data from multiple gene expression studies. This leads to more complications than those in standard meta-analyses, including different experimental platforms, duplicate spots and complex data structures. We illustrate these ideas using data from four prostate cancer profiling studies. In addition, we develop a simple approach for assessing differential expression using the LASSO method. A combination of the results and the pathway databases are then used to generate candidate biological pathways for cancer.     

Deltex E3 ubiquitin ligase 3 inhibits colorectal cancer cell growth and regulates cell cycle progression via upregulating E2F transcription factor 1

Molecular Biology Reports - The mortality rate of colorectal cancer (CRC) remains high in developing countries. Interventions that can inhibit the proliferation of tumor cells represent promising...     

Interactive gene expression pattern in prostate cancer cells exposed to phenolic antioxidants

Dietary phenolic compounds are known to elicite vital cellular responses such as cell cycle arrest, apoptosis and differentiation by activating a cascade of molecular events. As there is an increasing interest to improve the efficacy of these compounds for use as potential chemopreventive agents, we wanted to understand the impact of phenolic compounds on target genes in prostate cancer. In this study we used human cDNA microarrays with 2400 clones consisting of 17 prosite motifs to characterize alterations in gene expression pattern in response to the phenolic antioxidants ellagic acid (EA) and resveratrol (RE). Over a 48-hr exposure of androgen - sensitive LNCaP cells to EA and RE, a total of 593 and 555 genes respectively, showed more than a two fold difference in expression. A distinct set of genes in both EA-and RE-treated cells may represent the signature profile of phenolic antioxidant-induced gene expression in LNCaP cells. Although extensive similarity was found between effects of EA - and RE - responsive genes in prostate cancer cells, out of 246 genes with overlapping responses, 25 genes showed an opposite effect. Quantitative RT-PCR was used to verify and validate the differential expression of selected genes identified from cDNA microarrays. In-depth analysis of the data from this study provided insight into the alterations in the p53 - responsive genes, p300, Apaf-1, NF-kBp50 and p65 and PPAR families of genes, suggesting the activation of multiple signaling pathways that leads to growth inhibition of LNCaP cells. This is a first study to look for changes in a large number of human genes in response to dietary compounds.     

Genistein inhibits the contact-stimulated migration of prostate cancer cells

The results of several epidemiological studies have suggested that a soybean-based diet is associated with a lower risk of prostate cancer. We investigated the effect of the soy isoflavone genistein on the proliferation and contact-stimulated migration of rat prostatic carcinoma MAT-LyLu and AT-2 cell lines. Genistein almost completely inhibited the growth of both MAT-LyLu and AT-2 cells in the concentration range from 25 to 100 μM, but the addition of 1 μM genistein to the medium significantly stimulated the proliferation of both cell lines. Additionally, at concentrations above 25 μM, genistein showed a potent cytotoxic effect. However, the central finding of this study is that at physiologically relevant concentrations (1 μM and 10 μM), genistein inhibits the motility of prostate cancer cells stimulated by homo-and heterotypic contacts. These results show that at physiological concentrations, genistein exerts an inhibitory effect on the migration of prostate cancer cells and suggest that it may be one of the factors responsible for the anti-metastatic activity of plant isoflavonoids