Clusterin (CLU) and Prostate Cancer

Therapeutic Potential of Clusterin Inhibition in Human Cancer

Clusterin (CLU) protein is involved in various pathophysiological processes including carcinogenesis and tumor progression. In recent years, the role of the secretory isoform has been demonstrated in tumor cells, where it inhibits apoptosis and favors the acquisition of resistance to conventional treatments used to treat cancer. To determine the possible therapeutic potential of inhibiting this protein, numerous studies have been carried out in this field. In this article, we present the existing knowledge to date on the inhibition of this protein in different types of cancer and analyze the importance it could have in the development of new therapies targeted against this disease.

Clusterin Expression in Colorectal Carcinomas

Colorectal cancer is the third most diagnosed cancer, behind only breast and lung cancer. In terms of overall mortality, it ranks second due to, among other factors, problems with screening programs, which means that one of the factors that directly impacts survival and treatment success is early detection of the disease. Clusterin (CLU) is a molecular chaperone that has been linked to tumorigenesis, cancer progression and resistance to anticancer treatments, which has made it a promising drug target. However, it is still necessary to continue this line of research and to adjust the situations in which its use is more favorable. The aim of this paper is to review the current genetic knowledge on the role of CLU in tumorigenesis and cancer progression in general, and discuss its possible use as a therapeutic target in colorectal cancer.

Clusterin and Its Isoforms in Oral Squamous Cell Carcinoma and Their Potential as Biomarkers: A Comprehensive Review

Oral squamous cell carcinoma (OSCC) is a prevalent type of head and neck cancer, ranked as the sixth most common cancer worldwide, accounting for approximately 300,000 new cases and 145,000 deaths annually. Early detection using biomarkers significantly increases the 5-year survival rate of OSCC by up to 80-90%. Clusterin (CLU), also known as apolipoprotein J, is a sulfated chaperonic glycoprotein expressed in all tissues and human fluids and has been reported to be a potential biomarker of OSCC. CLU has been implicated as playing a vital role in many biological processes such as apoptosis, cell cycle, etc. Abnormal CLU expression has been linked with the development and progression of cancers. Despite the fact that there are many studies that have reported the involvement of CLU and its isoforms in OSCC, the exact roles of CLU and its isoforms in OSCC carcinogenesis have not been fully explored. This article aims to provide a comprehensive review of the current understanding of CLU structure and genetics and its correlation with OSCC tumorigenesis to better understand potential diagnostic and prognostic biomarker development. The relationship between CLU and chemotherapy resistance in cancer will also be discussed to explore the therapeutic application of CLU and its isoforms in OSCC.

A pan-cancer analysis reveals role of clusterin (CLU) in carcinogenesis and prognosis of human tumors

Clusterin (CLU) is a chaperone-like protein that has been demonstrated to have a direct relationship with cancer occurrence, progression, or metastasis. Clusterin was downregulated in tumor tissues using three datasets of tongue squamous carcinoma from the Gene Expression Omnibus. We further retrieved datasets from The Cancer Genome Atlas and Gene Expression Omnibus to thoroughly investigate the carcinogenic consequences of Clusterin. Our findings revealed that decreased Clusterin expression in malignancies was associated with a worse overall survival prognosis in individuals with multiple tumors; Clusterin gene deep deletions were found in almost all malignancies and were connected to most cancer patient's prognosis, Clusterin DNA methylation level was dependent on tumor type, Clusterin expression was also linked to the invasion of cancer-associated CD8+ T-cells and fibroblasts in numerous cancer forms. Moreover, pathway enrichment analysis revealed that Clusterin primarily regulates biological processes such as cholesterol metabolism, phospholipid binding, and protein-lipid complex formation. Overall, our pan-cancer research suggests that Clusterin expression levels are linked to tumor carcinogenesis and prognosis, which contributes to understanding the probable mechanism of Clusterin in tumorigenesis as well as its clinical prognostic significance.

Convolutional neural network in proteomics and metabolomics for determination of comorbidity between cancer and schizophrenia

The association between cancer risk and schizophrenia is widely debated. Despite many epidemiological studies, there is still no strong evidence regarding the molecular basis for the comorbidity between these two pathological conditions. The vast majority of assays have been performed using clinical records of schizophrenic patients or those undergoing cancer treatment and monitored for sufficient time to find shared features between the considered conditions. We performed mass spectrometry-based proteomic and metabolomic investigations of patients with different cancer phenotypes (breast, ovarian, renal, and prostate) and patients with schizophrenia. The resulting vast quantity of proteomic and metabolomic data were then processed using systems biology and one-dimensional (1D) convolutional neural network (1DCNN) machine learning approaches. Traditional systematic approaches permit the segregation of schizophrenia and cancer phenotypes on the level of biological processes, while 1DCNN recognized "signatures" that could segregate distinct cancer phenotypes and schizophrenia at the comorbidity level. The designed network efficiently discriminated unrelated pathologies with a model accuracy of 0.90 and different subtypes of oncophenotypes with an accuracy of 0.94. The proposed strategy integrates systematic analysis of identified compounds and application of 1DCNN model for unidentified ones to reveal the similarity between distinct phenotypes.

Clusterin overexpression in mice exacerbates diabetic phenotypes but suppresses tumor progression in a mouse melanoma model

Clusterin (CLU) is an ATP-independent small heat shock protein-like chaperone, which functions both intra- and extra-cellularly. Consequently, it has been functionally involved in several physiological (including aging), as well as in pathological conditions and most age-related diseases, e.g., cancer, neurodegeneration, and metabolic syndrome. To address CLU function at an in vivo model we established CLU transgenic (Tg) mice bearing ubiquitous or pancreas-targeted CLU overexpression (OE). Our downstream analyses in established Tg lines showed that ubiquitous or pancreas-targeted CLU OE in mice affected antioxidant, proteostatic and metabolic pathways. Targeted OE of CLU in the pancreas, which also resulted in CLU upregulation in the liver likely via systemic effects, increased basal glucose levels in the circulation and exacerbated diabetic phenotypes. Furthermore, by establishing a syngeneic melanoma mouse tumor model we found that ubiquitous CLU OE suppressed melanoma cells growth, indicating a likely tumor suppressor function in early phases of tumorigenesis. Our observations provide in vivo evidence corroborating the notion that CLU is a potential modulator of metabolic and/or proteostatic pathways playing an important role in diabetes and tumorigenesis.

The Dual Roles of Clusterin in Extracellular and Intracellular Proteostasis

Clusterin (CLU) was the first reported secreted mammalian chaperone and impacts on serious diseases associated with inappropriate extracellular protein aggregation. Many studies have described intracellular CLU in locations outside the secretory system and recent work has shown that CLU can be released into the cytosol during cell stress. In this article, we critically evaluate evidence relevant to the proposed origins of cellular CLU found outside the secretory system, and advance the hypothesis that the cytosolic release of CLU induced by stress serves to facilitate the trafficking of misfolded proteins to the proteasome and autophagy for degradation. We also propose future research directions that could help establish CLU as a unique chaperone performing critical and synergic roles in both intracellular and extracellular proteostasis.

Proteomic Profiling Change and Its Implies in the Early Mycosis Fungoides (MF) Using Isobaric Tags for Relative and Absolute Quantification (iTRAQ)

Purpose

Mycosis fungoides (MF) is the most common T-cell lymphoma, with indolent biologic behavior in the early stage and features of invasive in the tumor stage. The diagnosis of MF is still ambiguous and difficult. We focused on the proteomic profiling change in the pathogenesis of early MF and identified candidate biomarkers for early diagnosis.

Methods

We collected peripheral blood samples of MF patients and healthy individuals (HI) performed proteomic profiling analysis using isobaric tags for relative and absolute quantification (iTRAQ) platform. Differently expressed proteins (DEPs) were filtered, and involved biological functions were analyzed through Gene Ontology (GO) and Ingenuity Pathway Analysis (IPA) software.

Results

We identified 78 DEPs including fifty proteins were upregulated and 28 proteins were downregulated in the MF group with HI as a control. Total DEPs were analyzed according to the biological regulation and metabolic process through GO analysis. The pathways of LXR/RXR activation and FXR/RXR activation were significantly activated, in which APOH, CLU, and ITIH4 were involved. The top annotated disease and function network was (Cancer, Organismal Injury and Abnormalities, Reproductive System Disease), with a key node CLU. These DEPs were involved in cancer, including thyroid carcinoma, head and neck carcinoma, and cancer of secretory structure, in which CLU, GNAS, and PKM played an indirect role in the occurrence and development of cancer. Relevant causal network was IL12 (family), which is related to GNAS, PKM, and other DEPs.

Conclusion

Proteomic profiling of early-stage MF provided candidate protein biomarkers such as CLU, GNAS, and PKM, which benefit the early diagnosis and understanding of the mechanism of MF development. Besides, lipid metabolism may be one of the pathogenesis of MF, and IL12 was a potential marker for the diagnosis and treatment of early MF.

Immune-Related Gene-Based Novel Subtypes to Establish a Model Predicting the Risk of Prostate Cancer

BACKGROUND

There is significant heterogeneity in prostate cancer (PCa), but immune status can reflect its prognosis. This study aimed to explore immune-related gene-based novel subtypes and to use them to create a model predicting the risk of PCa.

METHODS

We downloaded the data of 487 PCa patients from The Cancer Genome Atlas (TCGA) database. We used immunologically relevant genes as input for consensus clustering and applied survival analysis and principal component analysis to determine the properties of the subtypes. We also explored differences of somatic variations, copy number variations, TMPRSS2-ERG fusion, and androgen receptor (AR) scores among the subtypes. Then, we examined the infiltration of different immune cells into the tumor microenvironment in each subtype. We next performed Gene Set Enrichment Analysis (GSEA) to illustrate the characteristics of the subtypes. Finally, based on the subtypes, we constructed a risk predictive model and verified it in TCGA, Gene Expression Omnibus (GEO), cBioPortal, and International Cancer Genome Consortium (ICGC) databases.

RESULTS

Four PCa subtypes (C1, C2, C3, and C4) were identified on immune status. Patients with the C3 subtype had the worst prognosis, while the other three groups did not differ significantly from each other in terms of their prognosis. Principal component analysis clearly distinguished high-risk (C3) and low-risk (C1 + 2 + 4) patients. Compared with the case in the low-risk subtype, the Speckle-type POZ Protein (SPOP) had a higher mutation frequency and lower transcriptional level in the high-risk subtype. In C3, there was also a higher frequency of copy number alterations (CNA) of Clusterin (CLU) and lower CLU expression. In addition, C3 had a higher frequency of TMPRSS2-ERG fusion and higher AR scores. M2 macrophages also showed significantly higher infiltration in the high-risk subtype, while CD8+ T cells and dendritic cells had significantly higher infiltration in the low-risk subtype. GSEA revealed that MYC, androgen, and KRAS were relatively activated and p53 was relatively suppressed in high-risk subtype, compared with the levels in the low-risk subtype. Finally, we trained a six-gene signature risk predictive model, which performed well in TCGA, GEO, cBioPortal, and ICGC databases.

CONCLUSION

PCa can be divided into four subtypes based on immune-related genes, among which the C3 subtype is associated with a poor prognosis. Based on these subtypes, a risk predictive model was developed, which could indicate patient prognosis.

The Possibility of Preventive and Therapeutic Use of Green Tea Catechins in Prostate Cancer

BACKGROUND

Prostate cancer is one of the most frequent types of cancer. Despite the existence of various treatment strategies, treatment of prostate cancer still presents serious difficulties (especially in advanced stages). Polyphenols have been extensively assessed in terms of their potential use for prostate cancer treatment and prevention. Catechins are among the most well-known polyphenols in this respect.

OBJECTIVE

In this review, we summarize clinical study results concerning catechin applications with regard to prostate cancer treatment and prevention. We discuss some of the main mechanisms of the anticarcinogenic action of catechins.

CONCLUSION

The main mechanisms of the anticarcinogenic action of catechins are subdivided into two major types: (i) direct action on cancer cells and (ii) indirect effect based on catechins's impact on the microenvironment of cancer cells, particularly in relation to the immune system. At this level catechins might reduce tumor-associated inflammation and immune tolerance.

Clusterin Silencing in Prostate Cancer Induces Matrix Metalloproteinases by an NF-κB-Dependent Mechanism

Clusterin (CLU) is a stress-activated glycoprotein, whose expression is altered both in inflammation and cancer. Previously, we showed that abrogation of CLU expression in cancer-prone mice (TRAMP) results in the enhancement of tumor spreading and homing, concomitant with an enhanced expression of NF-κB. In the present paper, we carried out an extensive experimental work by utilizing microarray gene expression data, as well as in vitro and in vivo models of prostate cancer (PCa). Our results demonstrated that (i) CLU expression is significantly downregulated in human PCa and inversely correlates with the expression of p65 in metastases; (ii) CLU overexpression in PCa cells reduces the Ser₅₃₆ phosphorylation of p65, inhibits NF-κB nuclear translocation, and reduces the transcription of matrix metalloproteinase-9 and metalloproteinase-2 (MMP-9 and MMP-2). Conversely, CLU silencing promotes NF-κB activation and transcriptional upregulation of MMP-9; and (iii) expression and activity of MMP-2 and MMP-9 are increased in CLU^−/− mice (CLUKO) and in TRAMP/CLUKO mice in comparison to their relative Clu^+/+ littermates. Taken together, our data support the hypothesis that CLU downregulation, an early and relevant event in PCa onset, may inhibit NF-κB activation and limit the execution of a transcriptional program that favor the disease progression towards a metastatic stage.

DNA methylation changes in infants between 6 and 52 weeks

Infants undergo extensive developments during their first year of life. Although the biological mechanisms involved are not yet fully understood, changes in the DNA methylation in mammals are believed to play a key role. This study was designed to investigate changes in infant DNA methylation that occurs between 6 and 52 weeks. A total of 214 infant saliva samples from 6 or 52 weeks were assessed using principal component analyses and t-distributed stochastic neighbor-embedding algorithms. Between the two time points, there were clear differences in DNA methylation. To further investigate these findings, paired two-sided student’s t-tests were performed. Differently methylated regions were defined as at least two consecutive probes that showed significant differences, with a q-value < 0.01 and a mean difference > 0.2. After correcting for false discovery rates, changes in the DNA methylation levels were found in 42 genes. Of these, 36 genes showed increased and six decreased DNA methylation. The overall DNA methylation changes indicated decreased gene expression. This was surprising because infants undergo such profound developments during their first year of life. The results were evaluated by taking into consideration the extensive development that occurs during pregnancy. During the first year of life, infants have an overall three-fold increase in weight, while the fetus develops from a single cell into a viable infant in 9 months, with an 875-million-fold increase in weight. It is possible that the findings represent a biological slowing mechanism in response to extensive fetal development. In conclusion, our study provides evidence of DNA methylation changes during the first year of life, representing a possible biological slowing mechanism. We encourage future studies of DNA methylation changes in infants to replicate the findings by using a repeated measures model and less stringent criteria to see if the same genes can be found, as well as investigating whether other genes are involved in development during this period.

Clusterin enhances AKT2-mediated motility of normal and cancer prostate cells through a PTEN and PHLPP1 circuit

Clusterin (CLU) is a chaperone-like protein with multiple functions. sCLU is frequently upregulated in prostate tumor cells after chemo- or radiotherapy and after surgical or pharmacological castration. Moreover, CLU has been documented to modulate the cellular homolog of murine thymoma virus akt8 oncogene (AKT) activity. Here, we investigated how CLU overexpression influences phosphatidylinositol 3'-kinase (PI3K)/AKT signaling in human normal and cancer epithelial prostate cells. Human prostate cells stably transfected with CLU were broadly profiled by reverse phase protein array (RPPA), with particular emphasis on the PI3K/AKT pathway. The effect of CLU overexpression on normal and cancer cell motility was also tested. Our results clearly indicate that CLU overexpression enhances phosphorylation of AKT restricted to isoform 2. Mechanistically, this can be explained by the finding that the phosphatase PH domain leucine-rich repeat-containing protein phosphatase 1 (PHLPP1), known to dephosphorylate AKT2 at S474, is markedly downregulated by CLU, whereas miR-190, a negative regulator of PHLPP1, is upregulated. Moreover, we found that phosphatase and tensin homolog (PTEN) was heavily phosphorylated at the inhibitory site S380, contributing to the hyperactivation of AKT signaling. By keeping AKT2 phosphorylation high, CLU dramatically enhances the migratory behavior of prostate epithelial cell lines with different migratory and invasive phenotypes, namely prostate normal epithelial 1A (PNT1A) and prostatic carcinoma 3 (PC3) cells. Altogether, our results unravel for the first time a circuit by which CLU can switch a low migration phenotype toward a high migration phenotype, through miR-190-dependent downmodulation of PHLPP1 expression and, in turn, stabilization of AKT2 phosphorylation.

Comprehensive Genomic Profiling of Androgen-Receptor-Negative Canine Prostate Cancer

Canine carcinomas have been considered natural models for human diseases; however, the genomic profile of canine prostate cancers (PCs) has not been explored. In this study, 14 PC androgen-receptor-negative cases, 4 proliferative inflammatory atrophies (PIA), and 5 normal prostate tissues were investigated by array-based comparative genomic hybridization (aCGH). Copy number alterations (CNAs) were assessed using the Canine Genome CGH Microarray 4 × 44K (Agilent Technologies). Genes covered by recurrent CNAs were submitted to enrichment and cross-validation analysis. In addition, the expression levels of TP53, MDM2 and ZBTB4 were evaluated in an independent set of cases by qPCR. PC cases presented genomic complexity, while PIA samples had a small number of CNAs. Recurrent losses covering well-known tumor suppressor genes, such as ATM, BRCA1, CDH1, MEN1 and TP53, were found in PC. The in silico functional analysis showed several cancer-related genes associated with canonical pathways and interaction networks previously described in human PC. The MDM2, TP53, and ZBTB4 copy number alterations were translated into altered expression levels. A cross-validation analysis using The Cancer Genome Atlas (TCGA) database for human PC uncovered similarities between canine and human PCs. Androgen-receptor-negative canine PC is a complex disease characterized by high genomic instability, showing a set of genes with similar alterations to human cancer.

Glucocorticoids Induce Stress Oncoproteins Associated with Therapy-Resistance in African American and European American Prostate Cancer Cells

Glucocorticoid receptor (GR) is emerging as a key driver of prostate cancer (PCa) progression and therapy resistance in the absence of androgen receptor (AR) signaling. Acting as a bypass mechanism, GR activates AR-regulated genes, although GR-target genes contributing to PCa therapy resistance remain to be identified. Emerging evidence also shows that African American (AA) men, who disproportionately develop aggressive PCa, have hypersensitive GR signaling linked to cumulative stressful life events. Using racially diverse PCa cell lines (MDA-PCa-2b, 22Rv1, PC3, and DU145) we examined the effects of glucocorticoids on the expression of two stress oncoproteins associated with PCa therapy resistance, Clusterin (CLU) and Lens Epithelium-Derived Growth Factor p75 (LEDGF/p75). We observed that glucocorticoids upregulated LEDGF/p75 and CLU in PCa cells. Blockade of GR activation abolished this upregulation. We also detected increased GR transcript expression in AA PCa tissues, compared to European American (EA) tissues, using Oncomine microarray datasets. These results demonstrate that glucocorticoids upregulate the therapy resistance-associated oncoproteins LEDGF/p75 and CLU, and suggest that this effect may be enhanced in AA PCa. This study provides an initial framework for understanding the contribution of glucocorticoid signaling to PCa health disparities.

Comparative Proteomics Analysis of Urine Reveals Down-Regulation of Acute Phase Response Signaling and LXR/RXR Activation Pathways in Prostate Cancer

Detecting prostate cancer (PCa) using non-invasive diagnostic markers still remains a challenge. The aim of this study was the identification of urine proteins that are sufficiently sensitive and specific to detect PCa in the early stages. Comparative proteomics profiling of urine from patients with PCa, benign prostate hyperplasia, bladder cancer, and renal cancer, coupled with bioinformatics analysis, were performed. Statistically significant difference in abundance showed 20 and 85 proteins in the 2-D DIGE/MS and label-free LC-MS/MS experiments, respectively. In silico analysis indicated activation, binding, and cell movement of subset of immune cells as the top affected cellular functions in PCa, together with the down-regulation of Acute Phase Response Signaling and Liver X Receptor/ Retinoid X Receptor (LXR/RXR) activation pathways. The most promising biomarkers were 35, altered in PCa when compared to more than one group. Half of these have confirmed localization in normal or PCa tissues. Twenty proteins (CD14, AHSG, ENO1, ANXA1, CLU, COL6A1, C3, FGA, FGG, HPX, PTGDS, S100A9, LMAN2, ITIH4, ACTA2, GRN, HBB, PEBP1, CTSB, SPP1) are oncogenes, tumor suppressors, and multifunctional proteins with highly confirmed involvement in PCa, while 9 (AZU1, IGHG1, RNASE2, PZP, REG1A, AMY1A, AMY2A, ACTG2, COL18A1) have been associated with different cancers, but not with PCa so far, and may represent novel findings. LC-MS/MS data are available via ProteomeXchange with identifier PXD008407.

Clusterin inhibition mediates sensitivity to chemotherapy and radiotherapy in human cancer

Since its discovery in 1983, the protein clusterin (CLU) has been isolated from almost all human tissues and fluids and linked to the development of different physiopathological processes, including carcinogenesis and tumor progression. During the last few years, several studies have shown the cytoprotective role of secretory CLU in tumor cells, inhibiting their apoptosis and enhancing their resistance to conventional treatments including hormone depletion, chemotherapy, and radiotherapy. In an effort to determine the therapeutic potential that the inhibition of this protein could have on the development of new strategies for cancer treatment, numerous studies have been carried out in this field, with results, in most cases, satisfactory but sometimes contradictory. In this document, we summarize for the first time the current knowledge of the effects that CLU inhibition has on sensitizing tumor cells to conventional cancer treatments and discuss its importance in the development of new strategies against cancer.

Investigation of serum proteome alterations in human endometriosis

Endometriosis is a common benign gynecological disease, characterized by proliferation of functional endometrial glands and stroma outside the uterine cavity. The present study involves investigation of alterations in the serum proteome of endometriosis patients compared to healthy controls using 2DE and 2D-DIGE combined with MALDI TOF/TOF-MS. Comparison of serum proteome of endometriosis patients and healthy subjects revealed 25 significant differentially expressed proteins. Gene ontology and network analysis, performed using PANTHER, DAVID, WebGestalt and STRING, revealed that the differentially expressed proteins are majorly involved in response to stimulus, immune system, metabolic, localization and cellular processes. For serum diagnostic marker identification, several robust statistical screening procedures were applied to identify the set of the most significant proteins responsible for successful diagnosis of different endometriosis stages. Partial least squares (PLS) based marker selection tool and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used to identify the most significant proteins for disease prediction. Western blotting validation in a separate cohort of patients revealed that haptoglobin (HP), Ig kappa chain C region (IGKC), alpha-1B-glycoprotein (A1BG) can be considered effective serum protein markers for the diagnosis of Stage II, III and IV endometriosis. For diagnosis of Stage I, only IGKC and HP seemed promising.

BIOLOGICAL SIGNIFICANCE

Globally, about 12 in 100 women of reproductive age are diagnosed with endometriosis. The pathogenesis of the disease still remains unclear, leading to non-specific therapeutic approaches for disease management. Moreover, there is a delay of 8-12years in correct diagnosis after the initial onset of symptoms leading to a considerable impact on the woman's lifestyle. Also, the gold standard for diagnosis of endometriosis, laparoscopy, is an invasive procedure. The value of a noninvasive or semi-invasive diagnostic test for endometriosis with easily accessible fluids such as plasma, serum, urine, and saliva is, therefore, rightfully recognized. The present study is expected to considerably improve the understanding of the disease pathogenesis along with improved diagnostics and therapeutic approaches leading to better management of the disease.

Deficiency of clusterin exacerbates high-fat diet-induced insulin resistance in male mice

The present study examined the role of clusterin in insulin resistance in high fat-fed wild-type and clusterin knockout (KO) mice. The plasma levels of glucose and C-peptide and islet size were increased in clusterin KO mice after an 8-week high-fat diet. In an ip glucose tolerance test, the area under the curve for glucose was not different, whereas the area under the curve for insulin was higher in clusterin KO mice. In a hyperinsulinemic-euglycemic clamp, the clamp insulin levels were higher in clusterin KO mice after the high-fat diet. After adjusting for the clamp insulin levels, the glucose infusion rate, suppression of hepatic glucose production, and glucose uptake were lower in clusterin KO mice in the high fat-fed group. The plasma levels of clusterin and clusterin mRNA levels in the skeletal muscle and liver were increased by the high-fat diet. The mRNA levels of the antioxidant enzymes were lower, and the mRNA levels of nicotinamide adenine dinucleotide phosphate oxidase (NOX) 1 and cytokines and protein carbonylation were higher in the skeletal muscle and liver in clusterin KO mice after the high-fat diet. Palmitate-induced gene expressions of NOX1 and cytokines were higher in the primary cultured hepatocytes of clusterin KO mice compared with the wild-type mice. Clusterin inhibited the gene expression and reactive oxygen species generation by palmitate in the hepatocytes and C2C12. AKT phosphorylation by insulin was reduced in the hepatocytes of clusterin KO mice. These results suggest that clusterin plays a protective role against high-fat diet-induced insulin resistance through the suppression of oxidative stress and inflammation.

Hypoxia inducible factor-1α directly regulates nuclear clusterin transcription by interacting with hypoxia response elements in the clusterin promoter

Differential transcription of the clusterin (CLU) gene yields two CLU isoforms, a nuclear form (nCLU) and a secretory form (sCLU), which play crucial roles in prostate tumorigenesis. Pro-apoptotic nCLU and anti-apoptotic sCLU have opposite effects and are differentially expressed in normal and cancer cells; however, their regulatory mechanisms at the transcriptional level are not yet known. Here, we examined the transcriptional regulation of nCLU in response to hypoxia. We identified three putative hypoxia response elements (HREs) in the human CLU promoter between positions -806 and +51 bp. Using a luciferase reporter, electrophoretic gel mobility shift, and chromatin immunoprecipitation assays, we further showed that hypoxia-inducible factor-1α (HIF-1α) bound directly to these sites and activated transcription. Exposure to the hypoxiamimetic compound CoCl₂, incubation under 1% O₂ conditions, or overexpression of HIF-1α enhanced nCLU expression and induced apoptosis in human prostate cancer PC3M cells. However, LNCaP prostate cancer cells were resistant to hypoxia-induced cell death. Methylation-specific PCR analysis revealed that the CLU promoter in PC3M cells was not methylated; in contrast, the CLU promoter in LNCap cells was methylated. Co-treatment of LNCaP cells with CoCl₂ and a demethylating agent promoted apoptotic cell death through the induction of nCLU. We conclude that nCLU expression is regulated by direct binding of HIF-1α to HRE sites and is epigenetically controlled by methylation of its promoter region.

Apocynin, an NADPH oxidase inhibitor, suppresses rat prostate carcinogenesis

Recent evidence suggests that oxidative stress contributes to the pathogenesis of prostate cancer. The present study focused on the effect of apocynin, an inhibitor of NADPH oxidase, on prostate carcinogenesis using the transgenic rat for adenocarcinoma of prostate (TRAP) model. There were no toxic effects with apocynin treatment. The percentages and numbers of carcinomas in both the ventral and lateral prostate were significantly reduced by apocynin treatment, with dose dependence. Reduction of reactive oxygen species by apocynin was confirmed by immunohistochemistry of 8-OHdG and dihydroethidium staining. Positivity of Ki67 was significantly reduced by apocynin treatment, and downregulation of clusterin expression, as well as inactivation of the MEK-ERK1/2 pathway, was a feature of the apocynin treated groups. In human prostate cancer cell line LNCaP, apocynin also inhibited reactive oxygen species production and blocked cell growth by inducing G0/G1 arrest with downregulation of clusterin and cyclin D1. These data suggest that apocynin possesses chemopreventive potential against prostate cancer.

Clusterin plays an important role in clear renal cell cancer metastasis

OBJECTIVE

Clusterin (CLU) is implicated in regulating clear renal cell carcinoma (CRCC) progression and metastasis, yet the mechanisms are not elucidated. In the present study, we explored the potential role of CLU in CRCC metastasis.

METHODS

Levels of CLU mRNA and CLU protein were measured by RT-PCR and immunohistochemistry analysis in 22 CRCC with metastasis and 22 without metastasis and 22 samples of normal kidney tissue. After CLU silencing and re-expression, the migration and invasion in vitro and in vivo of Caki-2 cells were determined by wound healing assay, transwell migration assay and pulmonary nodule assay, respectively. The expression of pERK1/2 and MMP-9 were detected by RT-PCR and Western blot assay.

RESULTS

We found a significant increase of CLU and CLU mRNA expression in CRCC, and the expression of CLU is strongly correlated in patients with metastatic disease. We discovered that CLU-rich Caki-2 cells displayed higher invasive ability which prompted us to investigate if CLU silencing could reduce the migration and invasion in Caki-2 cells. Compared with the vector-transfected cells, CLU knocked-down (CLUi) cells showed reduced migration and invasion in vitro, as well as decreased metastatic potential in experimental metastasis. Re-expression of CLU in CLUi cells restored the invasive phenotypes. We found that MMP-9 was downregulated in CLUi cells. We also discovered that levels of activated ERK1/2 correlated with the rich expression of CLU and MMP-9.

CONCLUSION

Our data suggest that CLU may regulate aggressive behavior of human CRCC cells through modulating ERK1/2 signaling and MMP-9 expression.

Identification of O-glycosylated proteins that are aberrantly excreted in the urine of patients with early stage ovarian cancer

Cancer is known to induce or alter the O-glycosylation of selective proteins that may eventually be excreted in the patients' urine. The present study was performed to identify O-glycosylated proteins that are aberrantly excreted in the urine of patients with early stage ovarian cancer (OCa). These urinary glycoproteins are potential biomarkers for early detection of OCa. In this study, urinary proteins of patients with early stage OCa and age-matched OCa negative women were subjected to two-dimensional gel electrophoresis and detection using a lectin that binds to the O-glycosylated proteins. Our analysis demonstrated significant enhanced expression of clusterin and leucine-rich alpha-2-glycoprotein, but lower levels of kininogen in the urine of the OCa patients compared to the controls. The different altered levels of these urinary glycoproteins were further confirmed using competitive ELISA. Our data are suggestive of the potential use of the aberrantly excreted urinary O-glycosylated proteins as biomarkers for the early detection of OCa, although this requires further validation in a large clinically representative population.

Small interfering RNA targeted to secretory clusterin blocks tumor growth, motility, and invasion in breast cancer

Clusterin/apolipoprotein J (Clu) is a ubiquitously expressed secreted heterodimeric glycoprotein that is implicated in several physiological processes. It has been reported that the elevated level of secreted clusterin (sClu) protein is associated with poor survival in breast cancer patients and can induce metastasis in rodent models. In this study, we investigated the effects of sClu inhibition with small interfering RNAs (siRNAs) on cell motility, invasion, and growth in vitro and in vivo. MDA-MB-231 cells were transfected with pSuper-siRNA/sClu. Cell survival and proliferation were examined by 3-(4,5-dimethyl-thiazol-2yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and clonogenic survival assay. The results showed that sClu silencing significantly inhibited the proliferation of MDA-MB-231 cells. The invasion and migration ability were also dramatically decreased, which was detected by matrigel assays. TUNEL staining and caspase-3 activity assay demonstrated that sClu silencing also could increase the apoptosis rate of cells, resulting in the inhibition of cell growth. We also determined the effects of sClu silencing on tumor growth and metastatic progression in an orthotopic breast cancer model. The results showed that orthotopic primary tumors derived from MDA-MB-231/pSuper sClu siRNA cells grew significantly slower than tumors derived from parental MDA-MB-231 or MDA-MB-231/pSuper scramble siRNA cells, and metastasize less to the lungs. These data suggest that secretory clusterin plays a significant role in tumor growth and metastatic progression. Knocking-down sClu gene expression may provide a valuable method for breast cancer therapy.

Stable knockdown of clusterin by vectorbased RNA interference in a human breast cancer cell line inhibits tumour cell invasion and metastasis

OBJECTIVE

Overexpression of the clusterin (CLU) gene occurs in breast cancer and is associated with lymph node metastasis. The present study explored the effect of CLU silencing on invasion and metastasis, and the relationship between CLU expression and the extracellular signal-regulated kinase (ERK) / matrix metalloproteinase-9 (MMP) signalling pathway in human breast cancer cells.

METHODS

A pcDNA3.1-based RNA interference approach was used to knockdown the CLU gene in MDA-231 cells (MDA-231-CLUi); control MDA-231 cells were transfected with an empty vector (MDA-231-Vec). Reverse transcription-polymerase chain reaction was used to assess CLU and MMP-9 mRNA levels, and Western blotting was used to analyse CLU, MMP-9 and ERK protein levels. Metastatic potential was evaluated using in vitro and in vivo models of invasion and metastasis.

RESULTS

Compared with MDA-231-Vec cells, the MDA-231-CLUi cells demonstrated reduced migration and invasion in vitro and decreased metastatic potential in vivo. Reintroduction and reexpression of the CLU gene into the MDA-231-CLUi cells restored the invasive phenotype. MMP-9 mRNA and protein levels were reduced in MDA-231-CLUi cells, and there was a correlation between activated ERK and CLU and MMP-9 protein levels.

CONCLUSION

CLU may regulate the aggressive behaviour of human breast cancer cells through modulation of ERK signalling and MMP9 expression.

TGF-β mediated DNA methylation in prostate cancer

Almost all tumors harbor a defective negative feedback loop of signaling by transforming growth factor-β (TGF-β). Epigenetic mechanisms of gene regulation, including DNA methylation, are fundamental to normal cellular function and also play a major role in carcinogenesis. Recent evidence demonstrated that TGF-β signaling mediates cancer development and progression. Many key events in TGF-β signaling in cancer included auto-induction of TGF-β1 and increased expression of DNA methyltransferases (DNMTs), suggesting that DNA methylation plays a significant role in cancer development and progression. In this review, we performed an extensive survey of the literature linking TGF-β signaling to DNA methylation in prostate cancer. It appeared that almost all DNA methylated genes detected in prostate cancer are directly or indirectly related to TGF-β signaling. This knowledge has provided a basis for our future directions of prostate cancer research and strategies for prevention and therapy for prostate cancer.

Circulating clusterin (apolipoprotein J) levels do not have any day/night variability and are positively associated with total and LDL cholesterol levels in young healthy individuals

CONTEXT

Clusterin has been associated with several pathologies, including cardiovascular disease and neoplasias. However, little is known about its physiology and its association with metabolic and anthropometric parameters in humans.

OBJECTIVE

The aim of the study was to examine whether circulating clusterin levels exhibit a day/night variation pattern and whether clusterin is associated with anthropometric and metabolic parameters.

DESIGN

Study A was a frequent sampling study to evaluate potential periodicity in clusterin secretion. Study B was an observational study to evaluate the cross-sectional and prospective associations of clusterin with anthropometric and metabolic parameters.

PARTICIPANTS

Study A participants were healthy males (n = 6) and females (n = 6), aged 22.3 ± 3.1 and 22.8 ± 3.4 yr, respectively. Study B participants were 186 healthy males aged 18.4 ± 0.14 yr. Ninety-one of the study B subjects were studied again 2 yr later and clusterin's associations with change of anthropometric and metabolic parameters were thus investigated prospectively.

INTERVENTION

Samples in study A were collected every 15 min during an overnight admission, and subsequently pooled every hour. Samples in study B were collected during a screening visit.

MAIN OUTCOME MEASURE

Circulating clusterin levels were measured.

RESULTS

In study A, spectral domain and cosinor regression analysis failed to reveal any day/night variation pattern. In study B, clusterin was positively correlated with total and low-density lipoprotein cholesterol (r = 0.23, P = 0.002; and r = 0.20, P = 0.005). Baseline clusterin did not predict change of any anthropometric, biochemical, or metabolic parameters prospectively.

CONCLUSIONS

We report for the first time that circulating clusterin does not have a day/night variation pattern in healthy young individuals. Clusterin levels are associated with total and low-density lipoprotein cholesterol cross-sectionally but do not predict short-term changes in metabolic parameters in healthy young males.

Selenium-responsive proteins in the sera of selenium-enriched yeast-supplemented healthy African American and Caucasian men

BACKGROUND

Studies have shown that supplementation of adult men with selenium-enriched yeast (SY) was protective against prostate cancer (PCa) and also reduced oxidative stress and levels of prostate-specific antigen. Here, we determined the effect of SY supplementation on global serum protein expression in healthy men to provide new insights into the mechanism of selenium chemoprevention; such proteins may also serve as biomarkers of disease progression.

METHODS

Serum samples from 36 adult men were obtained from our previous SY clinical trial, 9 months after supplementation with either SY (247 microg/d; n = 17) or placebo (nonenriched yeast; n = 19).

RESULTS

Proteomic profiling using two-dimensional difference in gel electrophoresis followed by liquid chromatography-tandem mass spectrometry revealed a total of 1,496 candidate proteins, of which, 11 were differentially expressed in the SY group as compared with placebo. Eight proteins were upregulated [clusterin isoform 1 (CLU), transthyretin, alpha-1B-glycoprotein, transferrin, complement component 4B proprotein, isocitrate dehydrogenase, haptoglobin, and keratin 1] and three proteins were downregulated [alpha-1 antitrypsin (AAT), angiotensin precursor, and albumin precursor] by SY. All of the identified proteins were redox-sensitive or involved in the regulation of redox status. Because both AAT and CLU have been previously linked to PCa development, their identities were confirmed by two-dimensional Western blot analysis.

CONCLUSIONS

We identified AAT and CLU as potential candidate proteins involved in the mechanism of PCa prevention by SY. Collectively, proteins identified in this study might serve as potential new biomarkers for monitoring and comparing responses to selenium-based chemopreventive agents.

IMPACT

Proteomic analysis of serum might be useful for the early detection and monitoring efficacy of chemopreventive agents.

Castration-refractory prostate cancer: New drugs in the pipeline

The standard treatment for patients with castration-refractory prostate cancer (CRPC) is the combination docetaxel-prednisone, if the patient can support chemotherapy. Several new treatments have been tested in chemotherapy-naïve or docetaxel-pretreated patients with CRPC. Some of these treatments have shown activity in first-line and second-line treatment. In this review, an update is given of new treatment studies performed in patients with CRPC.