Synthesis and functional analyses of nuclear clusterin, a cell death protein

Effect of Valproic Acid, a Histone Deacetylase Inhibitor, on Cell Death and Molecular Changes Caused by Low-Dose Irradiation

Valproic acid (VA), a histone deacetylase inhibitor (HDACI), in vitro induces differentiation of promyelocyte leukemia cell (HL-60) and proliferation arrest and apoptosis of various leukemia cell lines. In MOLT-4 cells (human T lymphocyte leukemia) the cell cycle arrest is caused by 2 mM VA, while 4 mM VA induces mainly apoptosis. In our work we studied effect of VA on molecular mechanisms responsible for cell cycle arrest (2 mM VA) or apoptosis induction (4 mM VA). The aim of our article was to evaluate a cotreatment by low (cytostatic) concentrations of VA with ionizing radiation and an effect of this combination on apoptosis induction in tumor cells MOLT-4. We prove that 24-h long incubation with VA causes acetylation of histones H3 and H4 in concentration-dependent manners. During first hours after the beginning of cultivation with VA in both studied concentrations (2 and 4 mM) an increase of p53 and its phosphorylation on serine 392 is detected, as well as a phosphorylation of Mdm2 on serine 166. After 8 and 24 h after the beginning of cultivation with 2 mM VA we detect p21, which is not observed after exposure to 4 mM VA. Cleavage of lamin B to 46 kDa fragment as an indicator of apoptosis was apparent after 24-h long incubation with 4 mM VA. In this article we prove radiosensitizing effect of VA. After 3-days long cultivation of cells with 2 mM VA the D(0) value decreased from 0.7 to 0.2 Gy. Also the EC70 value fell from 0.97 to 0.38 mM when the cells were irradiated with a dose of 1 Gy before the continual cultivation with VA. Continual cultivation of MOLT-4 cells irradiated by the dose of 1 Gy with VA caused during 14 days after irradiation significant increase of apoptotic cells in comparison to the cells exposed to only one factor. As a conclusion it can be postulated that continual exposure of MOLT-4 cells to VA increases apoptosis and decreases colony-forming capacity of the cells irradiated with small dose of radiation.

Clusterin up-regulation following sub-lethal oxidative stress and lipid peroxidation in human neuroblastoma cells

Clusterin/apolipoprotein J is a multifunctional protein up-regulated during various pathophysiological states. Since oxidative stress plays an important role in brain aging, and in many neurodegenerative disorders, to further understand the mechanistic underpinnings of clusterin expression, in this study, we examined clusterin expression in human neuroblastoma cells under conditions of increased production of reactive oxygen species and lipid peroxidation. Specifically, we analyzed clusterin mRNA and protein levels in human neuroblastoma IMR-32 and SH-SY5Y cells following exposure to sub-lethal amounts of iron-ascorbate to induce an increase in reactive oxygen species generation and lipid peroxidation. Under such conditions, we observed a time-dependent up-regulation of clusterin protein and mRNA levels, detected by immunoblot analysis and RT-PCR, respectively. Given the known roles of clusterin, the results of the present study support the notion that an increase in clusterin expression may be a physiological defence mounted to reduce cell damage and maintain cell viability during periods of increased oxidative stress.

Caspase-3 cleaves the formin-homology-domain-containing protein FHOD1 during apoptosis to generate a C-terminal fragment that is targeted to the nucleolus

The formin homology (FH) proteins play a crucial role in cytoskeleton remodelling during many essential processes. In this study, we demonstrate for the first time that the formin-homology-domain-containing protein FHOD1 is cleaved by caspase-3 at the SVPD(616) site during apoptosis. Using confocal microscopy, we further demonstrate that while full length FHOD1 is mostly cytoplasmic, the FHOD1 N-terminal cleavage product is diffusely localized throughout the cytoplasm and the nucleoplasm, whereas the C-terminal cleavage product is almost exclusively nuclear with some nucleolar localization. Finally, using a run-on transcription assay we show that the C-terminal FHOD1 cleavage product has the ability to inhibit RNA polymerase I transcription when overexpressed in HeLa cells as shown by blockage of BrUTP incorporation.

Clusterin and DNA repair: a new function in cancer for a key player in apoptosis and cell cycle control

The glycoprotein clusterin (CLU), has two known isoforms generated in human cells. A nuclear form of CLU protein (nCLU) is pro-apoptotic, while a secretory form (sCLU) is pro-survival. Both forms are implicated in various cell functions, including DNA repair, cell cycle regulation, and apoptotic cell death. CLU expression has been associated with tumorigenesis and the progression of various malignancies. In response to DNA damage, cell survival can be enhanced by activation of DNA repair mechanisms, while simultaneously stimulating energy-expensive cell cycle checkpoints that delay the cell cycle progression to allow more time for DNA repair. This review summarizes our current understanding of the role of clusterin in DNA repair, apoptosis, and cell cycle control and the relevance.

Expression of clusterin in prostate cancer correlates with Gleason score but not with prognosis in patients undergoing radical prostatectomy without neoadjuvant hormonal therapy

OBJECTIVES

To determine whether the expression level of clusterin in prostate cancer could be used as a prognostic predictor in patients who have undergone radical prostatectomy (RP).

METHODS

This study included 172 consecutive patients undergoing RP for clinically organ-confined prostate cancer without neoadjuvant hormonal therapy. Immunohistochemical staining was performed in RP specimens obtained from these patients to evaluate the expression level of clusterin protein. The cell proliferative activities and apoptotic features in these specimens were investigated using Ki-67 immunostaining and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay, respectively.

RESULTS

Varying levels of clusterin expression were noted in 169 of 172 prostate cancer specimens; 32 of the 172 normal prostatic tissue specimens did not exhibit any clusterin staining. Clusterin expression in prostate cancer tissue was significantly related to the Gleason score, but not to the other parameters, including age, serum prostate-specific antigen level, pathologic stage, perineural invasion, tumor volume, and lymph node metastasis. In addition, cell proliferative activity in the prostate cancer specimens was significantly associated with clusterin expression; however, no correlation was found between the apoptotic index and clusterin expression. In this series, 34 (19.8%) of 172 patients developed biochemical recurrence. No significant difference was found in biochemical/recurrence-free survival between patients with strong clusterin expression and those with weak expression.

CONCLUSIONS

Despite its detection in most prostate cancer tissue, clusterin expression failed to show a significant association with prognosis in patients undergoing RP without neoadjuvant hormonal therapy. This suggests a limited role for clusterin in the progression of clinically organ-confined prostate cancer in the absence of proapoptotic stimuli.

Clusterin is not essential for androgen-regulated involution and regeneration of the normal mouse prostate

BACKGROUND

Inhibition of clusterin expression has been shown to enhance the sensitivity of prostate cancer cells to chemo and hormone therapy. Clusterin antisense oligonucleotides (ASOs) are currently in phase II human clinical trials for treatment of hormone refractory prostate cancer. However, the role of clusterin in androgen-regulated involution and regeneration of the normal prostate gland has not been established.

METHODS

Prostate involution and regeneration was examined in clusterin-deficient mice undergoing up to three cycles of androgen withdrawal and restoration.

RESULTS

Surprisingly, clusterin deficiency did not affect the apoptotic index, and the temporal biochemical and morphological changes associated with involution and regeneration of the normal adult prostate following multiple rounds of androgen withdrawal and replacement.

CONCLUSION

Clusterin is not critical for normal prostate development or androgen-regulated involution and regrowth of the mouse prostate gland, suggesting that clusterin may have distinct functions in malignant versus normal prostatic epithelial cells.

Differential Expression of Serum Clusterin Isoforms in Colorectal Cancer

Clusterin is an enigmatic protein altered in tumors of colorectal cancer patients. Because there is no information available about serum clusterin regarding this pathology, we applied proteomic techniques to analyze its isoforms in donors and patients. First we separated serum proteins through concanavalin A, obtaining a fraction with non- and O-glycosylated proteins (FI) and a second fraction enriched in N-glycoproteins (FII) wherein clusterin was supposed to elute on the basis of its glycosylation. Surprisingly analysis of the FI fraction revealed the existence of an unexpected and aberrantly N-glycosylated clusterin that was overexpressed in patients and comprised at least five isoforms with different isoelectric points. On the other hand, two-dimensional electrophoretic analysis of the clusterin eluted in FII detected one isoform that was increased and 15 isoforms that were decreased or absent in serum of patients. Finally immunoquantification by slot blot showed that in total serum and in FI the clusterin levels were significantly increased in patients, whereas in FII there was no significant variation. Therefore, serum clusterin and some of its isoforms could have a potential value as colorectal tumor markers and are interesting subjects for biomarker studies.

Clusterin expression in primary and metastatic melanoma

Clusterin is a pleiotrophic glycoprotein that has been implicated in diverse physiologic processes. Recent studies of gene expression profiling found clusterin to be expressed in desmoplastic variants of malignant melanoma. In this study, we extended those observations and examined clusterin expression in a larger number of primary as well as in metastatic melanomas and melanocytic nevi. We used tissue microarray panels as well as selected conventional sections from formalin-fixed and paraffin-embedded tissue blocks. Positive staining for clusterin was found in seven of 21 (30%) primary desmoplastic and three of 21 (7%) non-desmoplastic melanoma. Among metastatic tumors, clusterin expression was found in five of 37 tumors (13.5%). Clusterin expression was not seen in melanocytes of normal skin or in any of the 10 melanocytic nevi tested. Clusterin expression was not entirely restricted to melanoma; it was also seen in a few non-neoplastic tissues, including perifollicular fibroblasts, occasional sebocytes, and the epithelial cells lining sebaceous duct and the isthmus of the hair follicle. Our findings confirm the observation that clusterin can be expressed in melanoma, in particular primary desmoplastic melanoma. However, clusterin appears to be present only in a minority of melanomas.

The leader sequence triggers and enhances several functions of clusterin and is instrumental in the progression of human prostate cancer in vivo and in vitro

OBJECTIVE

To investigate the role of the leader sequence (which during clusterin biosynthesis facilitates its proper post-translational processing and secretion) in the functional activities of clusterin, a ubiquitous secretory glycoprotein with many biological functions, reported to be pro-apoptotic and anti-apoptotic in target cells, but for which the dual mechanism remains unclear.

MATERIALS AND METHODS

We designed an expression vector starting from the second in-frame ATG on the full-length human clusterin cDNA that was capable of driving the expression of both the full-length and the truncated isoforms of clusterin. We established stable expression clones of the androgen-dependent prostate cancer line LNCaP expressing clusterin with and without the leader sequence. This induced expression provided an opportunity to evaluate both the in vivo and in vitro actions of clusterin expression.

RESULTS

The LNCaP cells expressing clusterin with the leader sequence resisted apoptosis induced by tumour necrosis factor (TNF)-alpha, but clones with no leader sequence were highly susceptible to TNF-alpha-induced apoptosis. Furthermore, in the absence of the leader sequence, the expressed clusterin had a molecular weight consistent with that of the predicted holoprotein (40 kDa), suggesting a compromised post-translational processing with diffuse distribution throughout the cytoplasm. However, cells transfected with the full-length vector expressed clusterin of 60 and 35 kDa variants, and located exclusively in the Golgi apparatus. In vivo, only the overexpression of the full-length clusterin is anti-apoptotic and stimulates the proliferation of tumour.

CONCLUSION

The leader sequence is important in determining the functions of clusterin, which include anti-apoptotic and anti-necrotic properties. The lack of the leader sequence allowed the incompletely processed clusterin to induce apoptosis in target cells; without the leader sequence, clusterin functions differently. Thus, the leader sequence is a trigger for many functions of clusterin in the progression of human prostate cancer cells.

The potential of clusterin inhibiting antisense oligodeoxynucleotide therapy for prostate cancer

This review summarise the authors' recent experience in the development of antisense (AS) oligodeoxynucleotide (ODN) therapy that targets a cytoprotective gene, clusterin, for the treatment of prostate cancer. The acquisition of resistance to a wide variety of proapototic stimuli was initially demonstrated by introducing the clusterin gene into prostate cancer cells. Furthermore, silencing clusterin expression using AS ODN synergistically enhanced the effects of several conventional therapeutic modalities through the effective induction of apoptosis in prostate cancer xenograft models. Based on these outcomes, Phase I clinical trials were conducted using AS clusterin ODN incorporating 2'-O-(2-methoxy)ethyl-gapmer backbone (OGX-011), and the optimal dose of OGX-011 capable of inducing </= 90% suppression of clusterin in human prostate cancer tissue was determined. Collectively, these findings suggest the utility of inactivating clusterin function using AS ODN technology as a novel therapeutic strategy for prostate cancer treatment. There have been four kinds of Phase II studies that have begun to further evaluate the efficacy of OGX-011 in patients with prostate, breast and lung cancers.

Rethinking some mechanisms invoked to explain translational regulation in eukaryotes

Real progress in understanding translational regulatory mechanisms lags behind the claims of progress. Novel mechanisms were proclaimed in recent months for some important regulatory proteins from Drosophila (e.g. Bruno, Sex-lethal, Reaper), but the evidence is thin. Many flaws in the design and interpretation of new experiments can be traced to older experiments which came to be accepted, not because the evidence was overwhelming, but because the ideas were appealing. Two of these classic examples of translational regulation are discussed before taking up the newer findings. One paradigm concerns regulation of 15-lipoxygenase production during reticulocyte maturation. The mechanism postulated for 15-lipoxygenase was pieced together in vitro and has never been linked in a meaningful way to what happens naturally in reticulocytes; nevertheless, these experiments have guided (or misguided) thinking about how sequences near the 3' end of an mRNA might regulate translation. The second paradigm concerns the regulation of cyclin B1 translation in Xenopus oocytes by a protein called Maskin, which purportedly interacts with initiation factors. A third topic discussed in some detail concerns the idea that in eukaryotes, as in prokaryotes, initiation of translation might involve base-pairing between mRNA and ribosomal RNA. Recent experiments undertaken to test this idea in yeast are far from conclusive. Many of the experimental defects brought to light in this review are simple-absence of controls, reliance on indirect tests, failure to test a new test system before using it; these things are fixable. Special problems are posed by the practice of using internal ribosome entry sequences (IRESs) as tools to figure out how translation might be regulated by other components. Unanswered questions about the IRESs themselves have to be resolved before they can be used confidently as tools.

Phagocytotic removal of apoptotic endocrine cells by folliculostellate cells and its functional implications in clusterin accumulation in pituitary colloids in helmeted guinea fowl (Numida meleagris)

The different cell types in the anterior pituitary behave as dynamic populations. The gland maintains a continuous renewal of cells to ensure a dynamic balance between cell division, differentiation, growth arrest and apoptosis. Apoptosis is a frequent event in the anterior pituitary in which unwanted cells are eliminated without affecting neighboring cells. We examined the link between apoptosis and the occurrence of colloids in the guinea fowl (Numida meleagris) pituitary gland and the relationship of clusterin accumulation in the colloids. S-100 positive folliculostellate (FS) cells were found surrounding colloids. Apoptotic cells detected by single stranded DNA (ssDNA) immunohistochemistry were observed in the whole anterior pituitary and preferentially near colloid masses. Clusterin protein was detected in endocrine cells, FS cells and in the colloids. In situ hybridization showed clusterin mRNA in endocrine cells and FS cells. Simultaneous localization was performed to determine whether clusterin mRNA and ssDNA within anterior pituitary was present within the same cell. Clusterin mRNA was not detected in apoptotic cells but was present in neighboring surviving cells. At the ultrastructural level, numerous endocrine cells at different stages of apoptosis were found phagocytosed by FS cells. Our results suggest that clusterin is produced by endocrine cells for cytoprotection before death. Apoptotic endocrine cells are phagocytosed by FS cells and digested by their lysosomal enzymes. In FS cells, clusterin interacts and aggregates with by-products of digestion that subsequently become stored in colloid as a residual body.

Nuclear clusterin accumulation during heat shock response: implications for cell survival and thermo-tolerance induction in immortalized and prostate cancer cells

Clusterin (CLU), whose role is still debated, is differentially regulated in several patho-physiological processes and invariably induced during apoptosis. In heat shock response, CLU is considered a stress-inducible, pro-survival/cyto-protective factor via an HSE element present in his promoter. In both human prostate PNT1A and PC-3 epithelial cells we found that apoptotic stimuli induced nuclear localization of CLU (nCLU), and that overexpression of nCLU is pro-apoptotic. We show here that CLU time-course accumulation kinetic is different from that of HSP70 in these cells, thus other factor(s) might mediate HSF-1 activation and CLU expression. Sub-lethal heat shock inhibited the secretion of CLU (sCLU), leading to increased cytoplasm accumulation of CLU (cCLU) in association to cell survival. At difference, lethal heat stress caused massive accumulation of pro-apoptotic nCLU in cells dying by caspase-3-dependent apoptosis. Double heat stress (sub-lethal heat shock followed by recovery and lethal stress) induced HSP70 and thermo-tolerance in PNT1A cells, but not in PC-3 cells. In PNT1A cells, CLU secretion was inhibited and cCLU was accumulated, suggesting that cCLU might be pro-survival, while in PC-3 cells accumulation of nCLU was concomitant to caspase-3 induction and PARP activation instead. Thus, CLU expression/sub-cellular localization is strictly related to cell fate. In particular, nCLU and physiological levels of HSP70 affected cell survival in an antagonistic fashion. Prevalence of heat-induced nCLU, not allowing PC-3 cells to cope with heat shock, could be the rational explaining why malignant cells are more sensitive to heat when delivered by minimally invasive procedures for ablation of localized prostate cancer.

Clusterin plays an important role in hepatocellular carcinoma metastasis

To identify genes associated with tumor metastasis in hepatocellular carcinoma (HCC), gene expression profiles between a pair of primary HCC (H2-P) and their matched metastatic HCC (H2-M) were compared. Overexpression of clusterin (CLU) was found in H2-M cells. To determine the roles CLU played in HCC metastasis, CLU was transfected into H2-P cells. Overexpression of CLU in H2-P cells increased cell migration by twofold in vitro and formation of metastatic tumor nodules in liver by eightfold in vivo. To evaluate the correlation of CLU expression with HCC metastasis, the expression levels of CLU in HCCs were investigated using a tissue microarray (TMA) containing 104 pairs of primary HCCs and their matched metastases. The frequency of CLU overexpression increased significantly in metastatic HCCs (59.1%) compared with that in primary tumors (32.6%, P<0.001). To gain additional insight into the function of CLU, the expression profile of H2P-CLU was compared with vector-transfected H2-P cells by cDNA microarray. A total of 35 upregulated and 14 downregulated genes were detected in H2P-CLU. One of the upregulated genes known as YKL-40, which is implicated in matrix-remodeling and metastasis, was further studied using TMA. A significant correlation (P<0.001) between the expression levels of YKL-40 and CLU was observed, implying that the CLU-YKL-40 pathway may play an important role in HCC metastasis.

Oncogenic HRAS suppresses clusterin expression through promoter hypermethylation

Silencing of gene expression by methylation of CpG islands in regulatory elements is frequently observed in cancer. However, an influence of the most common oncogenic signalling pathways onto DNA methylation has not yet been investigated thoroughly. To address this issue, we identified genes suppressed in HRAS-transformed rat fibroblasts but upregulated after treatment with the demethylating agent 5-Aza-2-deoxycytidine and with the MEK1,2 inhibitor U0126. Analysis of gene expression by microarray and Northern blot analysis revealed the MEK/ERK target genes clusterin, matrix metalloproteinase 2 (Mmp2), peptidylpropyl isomerase C-associated protein, syndecan 4, Timp2 and Thbs1 to be repressed in the HRAS-transformed FE-8 cells in a MEK/ERK- and methylation-dependent manner. Hypermethylation of putative regulatory elements in HRAS-transformed cells as compared to immortalized fibroblasts was detected within a CpG island 14.5 kb upstream of clusterin, within the clusterin promoter and within a CpG island of the Mmp2 promoter by bisulphite sequencing. Furthermore, hypermethylation of the clusterin promoter was observed 10 days after induction of HRAS in immortalized rat fibroblasts and a clear correlation between reduced clusterin expression and hypermethlyation could also be observed in distinct rat tissues. These results suggest that silencing of individual genes by DNA methylation is controlled by oncogenic signalling pathways, yet the mechanisms responsible for initial target gene suppression are variable.

Challenge and promise: roles for clusterin in pathogenesis, progression and therapy of cancer

Clusterin (CLU) has been implicated in various cell functions involved in carcinogenesis and tumour progression. There are two known CLU protein isoforms generated in human cells. A nuclear form of CLU protein (nCLU) is proapoptotic, and a secretory form (sCLU) is prosurvival. CLU expression has been associated with tumorigenesis of various malignancies, including tumours of prostate, colon, and breast. Furthermore, CLU expression is modulated by many factors that are believed to regulate tumour growth and/or apoptosis, including 1,25-dihydroxyvitamin D3, transforming growth factor beta-1, ultraviolet radiation, and IR. sCLU upregulation appears to be a general molecular stress response. Presently, preliminary results indicate that therapeutic modalities targeting CLU may be effective in cancer treatment. However, such strategies should make sure that nCLU is not eliminated or reduced. This review summarizes our present understanding of the importance of CLU in various physiological functions including tumour growth, and discusses its relevance to future cancer therapy.

Antisense oligodeoxynucleotide therapy targeting clusterin gene for prostate cancer: Vancouver experience from discovery to clinic

BACKGROUND

The objective of this study was to review our experience in the development of antisense (AS) oligodeoxynucleotide (ODN) therapy for prostate cancer targeting antiapoptotic gene, clusterin.

METHODS

We initially summarized our data demonstrating that clusterin could be an optimal therapeutic target for prostate cancer, then presented the process of developing AS ODN therapy using several preclinical animal models. Finally, the preliminary data of the recently completed phase I clinical trial using AS clusterin ODN as well as the future prospects of this therapy are discussed.

RESULTS

Expression of clusterin was highly up-regulated after androgen withdrawal and during progression to androgen-independence, but low or absent in untreated tissues in both prostate cancer animal model systems and human clinical specimens. Introduction of the clusterin gene into human prostate cancer cells confers resistance to several therapeutic stimuli, including androgen ablation, chemotherapy and radiation. AS ODN targeting the translation initiation site of the clusterin gene markedly inhibited clusterin expression in prostate cancer cells in a dose-dependent and sequence-specific manner. Systemic treatment with AS clusterin ODN enhanced the effects of several conventional therapies through the effective induction of apoptosis in prostate cancer xenograft models. Based on these findings, a phase I clinical trial was completed using AS clusterin ODN incorporating 2'-O-(2-methoxy)ethyl-gapmer backbone (OGX-011), showing up to 90% suppression of clusterin in prostate cancer.

CONCLUSIONS

The data described above identified clusterin as an antiapoptotic gene up-regulated in an adaptive cell survival manner following various cell death triggers that helps confer a phenotype resistant to therapeutic stimuli. Inhibition of clusterin expression using AS ODN technology enhances apoptosis induced by several conventional treatments, resulting in the delay of AI progression and improved survival. Clinical trials using AS ODN confirm potent suppression of clusterin expression and phase II studies will begin in early 2005.

Mornings with art, lessons learned: Feedback regulation, restriction threshold biology, and redundancy govern molecular stress responses

Work from the laboratory of Dr. Arthur B. Pardee has highlighted basic principles that govern cellular and molecular biological processes in living cells. Among the most important governing principles in cellular and molecular responses are: (i) threshold "restriction" responses, wherein a level of response is reached and a "point of no return" is achieved; (ii) feedback regulation; and (iii) redundancy. Lessons learned from the molecular biology of cellular stress responses in mammalian cancer versus normal cells after ionizing radiation (IR) or chemotherapeutic agent exposures reveal similar instances of these guiding principles in mammalian cells. Among these are the: (i) induction of cell death responses by beta-lapachone (beta-lap), a naphthoquinone anti-tumor agent that kills cancer cells via an NQO1 (i.e., X-ray-inducible protein-3, xip3)-dependent mechanism; (ii) induction of secretory clusterin (sCLU) in response to TGF-beta1 exposure, and the ability of induced sCLU protein to down-regulate TGF-beta1 signaling; and (iii) induction of DNA mismatch repair-dependent G(2) cell cycle checkpoint responses after exposure to alkylating agents. We have learned these lessons and now adopted strategies to exploit them for improved therapy. These examples will be discussed and compared to the pioneering findings of researchers in the Pardee laboratory over the years.

Clusterin as a therapeutic target for radiation sensitization in a lung cancer model

PURPOSE

Clusterin plays important roles in cell survival and death. Inactivation of clusterin enhances the therapeutic efficacy of chemotherapy in lung cancer models. The purpose of this study was to determine whether inhibition of clusterin by an antisense-based investigative drug enhances radiation sensitization in a lung cancer model.

METHODS AND MATERIALS

Cells were transfected with an antisense oligonucleotide (ASO) against clusterin (OGX-011). Apoptosis was determined by 7-aminoactinomycin D staining. Cell survival was examined by 3-(4, 5-methylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) and clonogenic assay. Xenograft model was used to demonstrate tumor growth and tumor blood flow.

RESULTS

OGX-011 specifically attenuated the expression of secreted clusterin (prosurvival), with no apparent effect on the expression of nuclear clusterin (proapoptotic). Apoptosis was significantly increased when H460 lung cancer cells were treated with OGX-011 plus radiation. Inhibition of clusterin followed by radiation greatly decreased cell survival. H460 xenografts that were treated with OGX-011 plus radiotherapy demonstrated growth delay beyond 17 days. Doppler studies showed that tumor blood flow was compromised when mice bearing H460 xenografts were treated with OGX-011 and radiation.

CONCLUSION

A combination of radiotherapy and OGX-011 improved control of tumor growth and vascular regression in the H460 lung cancer model.

Induction of clusterin/apoJ expression by histone deacetylase inhibitors in neural cells

The regulation of clusterin expression is poorly characterized although some regulatory elements have been identified, such as CpG-rich methylation domain. Environmental stress, aging, diet and diseases regulate DNA methylation and protein acetylation status but interestingly, the same insults increase clusterin expression in vivo. Our purpose was to elucidate whether histone deacetylase inhibitors, such as TSA, SAHA and M344, as well as an inhibitor of DNA methylation, 5'-aza-2'-deoxycytidine, could regulate the expression of clusterin in cultured neural cells. We observed that histone deacetylase inhibitors induced the expression of clusterin mRNA and protein in all neural cells studied. The induction of clusterin mRNA was blocked by actinomycin D which indicates that TSA regulates clusterin expression at the transcriptional level. An inhibitor of DNA methylation, 5'-aza-2'-deoxycytidine, itself did not affect the expression of clusterin mRNA but strongly potentiated the TSA-induced expression of clusterin. Proteasomal stress (MG-132 and PI-1 treatments) and apoptotic stress (okadaic acid treatment) did not affect clusterin expression which indicates that the induction of clusterin expression requires more specific inducers than cellular stress in general. Furthermore, LPS did not affect clusterin expression in N9 microglia although activated NF-kappaB signaling and IL-6 expression. CAPE and helenalin, inhibitors of NF-kappaB signalling, did not affect the clusterin mRNA expression either in non-treated or in TSA-treated N9 microglia. These observations suggest that clusterin induction is NF-kappaB-independent and unrelated to the inflammatory response in N9 microglia.

Protein profiling and identification of modulators regulated by human papillomavirus 16 E7 oncogene in HaCaT keratinocytes by proteomics

OBJECTIVES

Viral oncogenes E6 and E7 are selectively retained and expressed in carcinoma cells infected with human papillomavirus type 16 and cooperated with each other in immortalization and transformation of primary keratinocytes. This study was performed to identify proteins to be bound or modulated by high risk HPV E7 oncogene by using a proteomics.

METHODS

HaCaT normal keratinocyte was prepared to establish a stable cell line expressing E7. The E7-affinity column was also prepared to obtain E7-interacting proteins. In order to search the target molecules modulated by E7 expression, we used 2-dimensional electrophoresis and matrix-assisted laser desorption/ionization time of flight (MALDI/TOF) mass spectrometry. Pull down assay was also performed in order to confirm the E7-interacting proteins.

RESULTS

We identified 28 spots that are modulated by E7 in HaCaT/E7 using 2-dimensional electrophoresis (2-DE) and MALDI/TOF mass spectrometry. Proteomics analyses showed that actin and leukocyte elastase inhibitor were down-regulated, whereas stress-induced phosphoprotein 1, CD2 binding protein 1, catalase, T-complex protein 1, Ku70-binding protein, heat shock 60 kDa protein 1, G1/S-specific cyclin E1 and peroxiredoxin 2 were up-regulated. Western blot revealed that heat shock 60 kDa protein, catalase and peroxiredoxin 2 were also up-regulated. Pull down assay also showed that leukocyte elastase inhibitor (LEI) and Ku70-binding protein were bound to the E7 oncoprotein. By using E7-affinity column and 2-DE/MALDI-TOF, 22 spots were found to interact with E7 recombinant protein. MG11-like proteins, livin inhibitor-of-apoptosis, protein serine kinase c17, CD2 binding protein 1, cyclin E1, TATA box binding protein-associated factor and uridine-cytidine kinase 2 were up-regulated by E7 oncogene and also bound to E7 oncoprotein.

CONCLUSIONS

It is presumed that E7 can influence cell status by modulating the factors related to cell signaling, apoptosis and cell cycle regulation.

Expression of the secreted form of clusterin protein in renal cell carcinoma as a predictor of disease extension

OBJECTIVES

To evaluate the significance of clusterin expression in surgically resected renal cell carcinoma (RCC) specimens.

PATIENTS AND METHODS

Normal kidney and RCC specimens were obtained from 131 patients who had radical surgery. The expression of clusterin protein was analysed by immunohistochemical staining with an antibody recognizing all isoforms of clusterin. Cell proliferative activities and apoptotic features in these specimens were investigated using Ki-67 immunostaining and the terminal deoxynucleotidyl transferase mediated dUTP nick-end labelling assay, respectively. Findings were evaluated in relation to several clinicopathological factors.

RESULTS

There were various levels of clusterin expression in 128 of the 131 RCC specimens, while 37 of 131 normal kidney tissues (28.2%) had no clusterin staining. Clusterin protein was present in the cytoplasm of both normal and cancer cells, but there was no nuclear staining identified in either type of cell. The expression level of clusterin protein in RCC tissues was significantly related to tumour stage and grade, but not to age, gender or histological cell type. Cell proliferative activity in RCC specimens was significantly associated with clusterin expression, while the apoptotic index was inversely related to clusterin expression. Furthermore, recurrence-free survival in patients with strong clusterin expression was significantly lower than that in those with weak expression.

CONCLUSIONS

These findings suggest that the secreted form of clusterin may be involved in the progression of RCC, and that overexpression of clusterin could be a useful prognostic variable after radical surgery in patients with RCC.

Antisense clusterin oligodeoxynucleotides increase the response of HER-2 gene amplified breast cancer cells to Trastuzumab

Clusterin (CLU) is a heterodimeric secreted glycoprotein implicated in several physiological and pathological processes including cancer. Although recent data showed that overexpression of CLU is closely associated with disease progression in patients with breast tumor, the functional role of CLU expression in this tumor hystotype remains to be determined. The objectives in this study were to evaluate CLU expression levels after treatment with Trastuzumab, a HER2-targeted monoclonal antibody used in the clinical management of advanced breast cancer patients, and to test the usefulness of combined treatment with OGX-011, the second generation 2'-methoxyethyl gapmer oligonucleotides targeting the CLU gene, and Trastuzumab in this tumor hystotype. By using the HER-2 gene amplified-BT474 human breast cancer cells, we found Trastuzumab decreased HER-2 expression and inhibited cell proliferation without affecting apoptosis. Interestingly, Trastuzumab treatment up-regulated CLU protein expression in a dose-dependent fashion. We therefore hypothesized that the treatment with OGX-011, by blocking Trastuzumab-induced CLU expression, might potentiate the growth-inhibitory effect of Trastuzumab alone. Although OGX-011 had no effect on the behavior of the BT474 cells when used alone, it significantly enhanced the sensitivity of cells to Trastuzumab. A significant increase in the percentage of apoptotic cells, analyzed in terms of annexin V positivity and cleavage of poly(ADP-ribose) polymerase, was observed after combined treatment with OGX-011 plus Trastuzumab but not with either agent alone. Altogether our findings suggest that combined targeting of HER-2 and CLU may represent a novel, rational approach to breast cancer therapy.

Clusterin inhibits apoptosis by interacting with activated Bax

Clusterin is an enigmatic glycoprotein that is overexpressed in several human cancers such as prostate and breast cancers, and squamous cell carcinoma. Because the suppression of clusterin expression renders human cancer cells sensitive to chemotherapeutic drug-mediated apoptosis, it is currently an antisense target in clinical trials for prostate cancer. However, the molecular mechanisms by which clusterin inhibits apoptosis in human cancer cells are unknown. Here we report that intracellular clusterin inhibits apoptosis by interfering with Bax activation in mitochondria. Intriguingly, in contrast to other inhibitors of Bax, clusterin specifically interacts with conformation-altered Bax in response to chemotherapeutic drugs. This interaction impedes Bax oligomerization, which leads to the release of cytochrome c from mitochondria and caspase activation. Moreover, we also find that clusterin inhibits oncogenic c-Myc-mediated apoptosis by interacting with conformation-altered Bax. Clusterin promotes c-Myc-mediated transformation in vitro and tumour progression in vivo. Taken together, our results suggest that the elevated level of clusterin in human cancers may promote oncogenic transformation and tumour progression by interfering with Bax pro-apoptotic activities.

Clusterin regulates drug-resistance in melanoma cells

Clusterin has recently been shown to act as an antiapoptotic protein that confers drug-resistance in models of epithelial tumors. The aim of our work was to provide an insight into a possible role of clusterin in the regulation of drug-resistance in melanoma. In tissue samples, clusterin expression was low in nevi, but high in primary melanoma and melanoma metastases. Clusterin was also strongly expressed in melanoma cell lines, but was barely detectable in cultured melanocytes. To elucidate a possible role of clusterin in drug-resistance of melanoma, clusterin expression was regulated by either plasmid-driven overexpression or by antisense-mediated downregulation. Clusterin overexpression was associated with an increase in drug-resistance, i.e., with an increased survival of melanoma cells in the presence of cytotoxic drugs. In contrast, downregulation of clusterin by 2'-O-(2-methoxy)ethyl (2'MOE)-modified antisense oligonucleotides (AS-ODN) directed against clusterin mRNA significantly reduced drug-resistance, i.e., decreased survival of melanoma cells in the presence of cytotoxic drugs. To evaluate the effects of clusterin-antisense treatment in vivo, we applied an SCID-mouse/human-melanoma xenotransplantation model. Pre-treatment of mice with the 2'MOE-modified clusterin AS-ODN was associated with a significantly improved tumor response to dacarbazine as compared with animals pretreated with a scrambled control oligonucleotide. Taken together, we show that clusterin is strongly expressed in melanoma. Downregulation of clusterin reduces drug-resistance, i.e., reduces melanoma cell survival in response to cytotoxic drugs in vitro and in vivo. Thus, reducing clusterin expression may provide a novel tool to overcome drug-resistance in melanoma.

IR-inducible clusterin gene expression: a protein with potential roles in ionizing radiation-induced adaptive responses, genomic instability, and bystander effects

Clusterin (CLU) plays numerous roles in mammalian cells after stress. A review of the recent literature strongly suggests potential roles for CLU proteins in low dose ionizing radiation (IR)-inducible adaptive responses, bystander effects, and delayed death and genomic instability. Its most striking and evident feature is the inducibility of the CLU promoter after low, as well as high, doses of IR. Two major forms of CLU, secreted (sCLU) and nuclear (nCLU), possess opposite functions in cellular responses to IR: sCLU is cytoprotective, whereas nCLU (a byproduct of alternative splicing) is a pro-death factor. Recent studies from our laboratory and others demonstrated that down-regulation of sCLU by specific siRNA increased cytotoxic responses to chemotherapy and IR. sCLU was induced after low non-toxic doses of IR (0.02-0.5 Gy) in human cultured cells and in mice in vivo. The low dose inducibility of this survival protein suggests a possible role for sCLU in radiation adaptive responses, characterized by increased cell radioresistance after exposure to low adapting IR doses. Although it is still unclear whether the adaptive response is beneficial or not to cells, survival of damaged cells after IR may lead to genomic instability in the descendants of surviving cells. Recent studies indicate a link between sCLU accumulation and cancer incidence, as well as aging, supporting involvement of the protein in the development of genomic instability. Secreted after IR, sCLU may also alter intracellular communication due to its ability to bind cell surface receptors, such as the TGF-beta receptors (types I and II). This interference with signaling pathways may contribute to IR-induced bystander effects. We hypothesize that activation of the TGF-beta signaling pathway, which often occurs after IR exposure, can in turn activate the CLU promoter. TGF-beta and IR-inducible de novo synthesized sCLU may then bind the TGF-beta receptors and suppress downstream growth arrest signaling. This complicated negative feedback regulation most certainly depends on the cellular microenvironment, but undoubtedly represents a potential link between IR-induced adaptive responses, genomic instability and bystander effects. Further elucidation of clusterin protein functions in IR responses are clearly warranted.

Insertion/deletion polymorphism in clusterin gene influences serum lipid levels and carotid intima-media thickness in hypertensive Japanese females

Clusterin has been implicated in lipid metabolism and atherogenesis, however, the influence of genetic variation has not been examined in Japanese. In this study, we identified 11 single nucleotide polymorphisms (SNPs) of clusterin gene by direct sequencing. Among them, one promoter SNP (-4453T>G), one missense SNP (4183G>A), and 2 common SNPs (5608T>C and 6316delT) were genotyped in 525 asymptomatic hypertensives not treated with lipid lowering agents. -4453T>G, 4183G>A, and 5608T>C showed no correlation with the clinical characteristics, however, in the 6316delT, an insertion (I)/deletion (D) polymorphism, D/D subjects had significantly higher levels of total cholesterol and low-density lipoprotein (LDL)-cholesterol than I/I subjects in females but not in males. Female subjects with the D allele (D/D+I/D) had greater intima-media thickness of the carotid artery than I/I subjects. In a multiple logistic regression analysis, the D allele of 6316delT was detected as an independent predictor for the plaque prevalence. In conclusion, the clusterin gene polymorphism may contribute to the serum lipid levels and the progression of carotid atherosclerosis in hypertensive Japanese females.

Apolipoprotein J (clusterin) activates rodent microglia in vivo and in vitro

Apolipoprotein J (apoJ; also known as clusterin and sulfated glycoprotein (SGP)-2) is associated with senile plaques in degenerating regions of Alzheimer's disease brains, where activated microglia are also prominent. We show a functional link between apoJ and activated microglia by demonstrating that exogenous apoJ activates rodent microglia in vivo and in vitro. Intracerebroventricular infusion of purified human plasma apoJ ( approximately 4 microg over 28 days) activated parenchymal microglia to a phenotype characterized by enlarged cell bodies and processes (phosphotyrosine immunostaining). In vitro, primary rat microglia were also activated by apoJ, with changes in morphology and induction of major histocompatibility complex class II (MHCII) antigen. ApoJ increased the secretion of reactive nitrogen intermediates in a dose-dependent manner (EC(50) 112 nm), which was completely blocked by aminoguanidine (AG), a nitric oxide synthase inhibitor. However, AG did not block the increased secretion of tumor necrosis factor-alpha by apoJ (EC(50) 55 nm). Microglial activation by apoJ was also blocked by an anti-apoJ monoclonal antibody (G7), and by chemical cleavage of apoJ with 2-nitro-5-thiocyanobenzoate. The mitogen-activated protein kinase kinase and protein kinase C inhibitors PD98059 and H7 inhibited apoJ-mediated induction of reactive nitrogen intermediate secretion from cultured microglia. As a functional measure, apoJ-activated microglia secreted neurotoxic agents in a microglia-neuron co-culture model. We hypothesize that ApoJ contributes to chronic inflammation and neurotoxicity through direct effects on microglia.

Radiation-induced adaptive responses and bystander effects

A classical paradigm [correction of paradym] of radiation biology asserts that all radiation effects on cells, tissues and organisms are due to the direct action of radiation. However, there has been a recent growth of interest in the indirect actions of radiation including the radiation-induced adaptive response, the bystander effect, low-dose hypersensitivity, and genomic instability, which are specific modes of stress exhibited in response to low-dose/low-dose rate radiation. This review focuses on the radiation-induced bystander effect and the adaptive response, provides a description of the two phenomena, and discusses the contribution of the former to the latter.

Oncogenic role of clusterin overexpression in multistage colorectal tumorigenesis and progression

AIM: To investigate the expression pattern of clusterin in colorectal adenoma-carcinoma-metastasis series, and to explore the potential role of clusterin in multistage colorectal tumorigenesis and progression.

METHODS: A colorectal carcinoma (CRC)-tissue microarray (TMA), which contained 85 advanced CRCs including 43 cases of Dukes B, 21 of Dukes C and 21 of Dukes D tumors, were used for assessing the expression of clusterin (clone 41D) and tumor cell apoptotic index (AI) by immunohist-ochemistry and TUNEL assay, respectively. Moreover the potential correlation of clusterin expression with the patient’s clinical-pathological features were also examined.

RESULTS: The positive staining of clusterin in different colorectal tissues was primarily a cytoplasmic pattern. Cytoplasmic overexpression of clusterin was detected in none of the normal colorectal mucosa, 17% of the adenomas, 46% of the primary CRCs, and 57% of the CRC metastatic lesions. In addition, a significant positive correlation between overexpression of clusterin and advanced clinical (Dukes) stage was observed (P<0.01). Overexpression of cytoplasmic clusterin in CRCs was inversely correlated with tumor apoptotic index (P<0.01), indicating the anti-apoptotic function of cytoplasmic clusterin in CRCs.

CONCLUSION: These data suggests that overexpression of cytoplasmic clusterin might be involved in the tumorigenesis and/or progression of CRCs. The anti-apoptotic function of cytoplasmic clusterin may be responsible, at least in part, for the development and biologically aggressive behavior of CRC.

Upregulation of complement inhibitors in association with vulnerable cells following contusion-induced spinal cord injury

We have previously described the activation of the classical, alternative, and terminal complement cascade pathways after acute contusion spinal cord injury using the New York University (NYU) weight-drop impactor. In the present study, we examined the induction of protein regulators of the complement cascade, factor H (FH), and clusterin, in the same experimental paradigm. The spinal cord of laminectomized adult rats was subjected to mild or severe injury using impactor weight-drop heights of 12.5 and 50 mm, respectively. The spinal cords of control and injured animals were evaluated at 1, 7, and 42 days after injury. Immunocytochemistry revealed a robust increase in the numbers and intensity of staining of FH, and clusterin-positive cells in the injured cord at all three time points, with the highest increases observed at 1 and 42 days after injury. FH and clusterin-positive cells were observed among neurons as well as oligodendrocytes. The increased expression was detected both rostrally and caudally from the injury site, in the latter case at distances up to 20 mm. The precise biological significance of injury-induced upregulation of these proteins remains to be determined. However, FH and clusterin are potent regulators of complement activity targeting upstream (FH) and downstream (clusterin) molecules of the pro-inflammatory cascade, which could be of vital importance in preventing a "runaway" inflammatory reaction in the injured spinal cord.

Gene expression profiling of mouse teratocarcinomas uncovers epigenetic changes associated with the transformation of mouse embryonic stem cells

The molecular mechanisms of the development of teratocarcinomas from stem cells are largely unknown. To determine which genes are associated with the transformation of these cells, we have performed oligonucleotide microarray analysis, using Affymetrix U74A GeneChips, on both cell cultures and tumors in nude mice. We identified 68 genes that significantly differed in expression between the ES cell culture and the teratocarcinoma cell line, SCC-PSA1, and 51 genes with statistically different expression patterns between the ES cell tumors and the teratocarcinomas (P < .00005). We found that there were 20 genes that had common expression patterns in both groups. We also examined the role of the transition from in vitro to in vivo by comparing ES cell culture to ES cell tumor, and teratocarcinoma cell line to teratocarcinomas. We identified 22 genes that were upregulated in the ES cell tumors and 42 that had a decreased expression in the tumor (P < .0001). In comparing SCC-PSA1 to its tumor, we identified 34 upregulated genes and 25 downregulated genes (P < .001). There were only 10 genes in common from these two lists. GenMapp search revealed that several pathways, especially the cell cycle pathway, are actively involved in the induction of teratocarcinomas. Our results indicate that many key development genes may play a key role in the transformation of ES cells into teratocarcinoma cells.

Ketogenic diet prevents clusterin accumulation induced by kainic acid in the hippocampus of male ICR mice

We investigated the effect of ketogenic diet (KD) on clusterin accumulation in the kainic acid (KA)-induced seizure model. Two days after KA administration, strong clusterin-like immunoreactivity (IR) was detected in the hippocampus in the normal diet (ND)-fed mice. But in the KD-fed mice, few clusterin-like IR was detected. These results indicate that KD has neuroprotective effects throughout diminishing nuclear clusterin accumulation that is involved in caspase-3 independent cell death mechanism.

Delayed Activation of Insulin-like Growth Factor-1 Receptor/Src/MAPK/Egr-1 Signaling Regulates Clusterin Expression, a Pro-survival Factor

Secretory clusterin protein (sCLU) is a general genotoxic stress-induced, pro-survival gene product implicated in aging, obesity, heart disease, and cancer. However, the regulatory signal transduction processes that control sCLU expression remain undefined. Here, we report that induction of sCLU is delayed, peaking 72 h after low doses of ionizing radiation, and is dependent on the up-regulation of insulin-like growth factor-1 as well as phosphorylation-dependent activation of its receptor (IGF-1 and IGF-1R, respectively). Activated IGF-1R then stimulates the downstream Src-Mek-Erk signal transduction cascade to ultimately transactivate the early growth response-1 (Egr-1) transcription factor, required for sCLU expression. Thus, ionizing radiation exposure causes stress-induced activation of IGF-1R-Src-Mek-Erk-Egr-1 signaling that regulates the sCLU pro-survival cascade pathway, important for radiation resistance in cancer therapy.

Interaction of stress proteins with misfolded keratins

Misfolded and aggregated proteins are a characteristic feature of a variety of chronic diseases. Examples include neurofibrillary tangles in Alzheimer disease, Lewy bodies in Parkinson disease and Mallory bodies (MBs) in chronic liver diseases, particularly alcoholic and non-alcoholic steatohepatitis (ASH and NASH). MB formation is at least in part the result of chronic oxidative cell stress in hepatocytes and can be induced in mice by long-term intoxication with 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). Proteomic analysis revealed that MBs consist of ubiquitinated keratins and the stress proteins Hsp70, Hsp25, and p62. Furthermore, marked overexpression of clusterin, which shares functional properties with small heat shock proteins, was identified by gene expression profiling of DDC-treated mice livers. To investigate whether clusterin has a function in the stress response to misfolded keratins, we performed transfection studies utilizing expression constructs encoding ubiquitin, p62, Hsp27, clusterin, keratin 8, and keratin 18. Ubiquitin was found in a strong and constant association with keratin aggregates, whereas binding of p62 to keratin was variable. Hsp27 did not colocalize with keratin aggregates under these experimental conditions. In contrast, clusterin associated with misfolded keratin only if its signal peptide was deleted and its secretion inhibited. This suggests that clusterin has ability to bind misfolded proteins, including keratins but its physiological function is restricted to the extracellular space. The extracellular localization of clusterin was underlined by immunohistochemical studies in Alzheimer disease brains, where clusterin was constantly found in association with amyloid plaques; in contrast, cytoplasmic inclusions such as neurofibrillary tangles as well as MBs in ASH were negative. Furthermore, we found clusterin in association with elastic fibers in the extracellular matrix in several chronic liver diseases, including ASH and alpha1-antitrypsin deficiency, implying a possible role of clusterin in liver fibrosis.

Differential effects of clusterin/apolipoprotein J on cellular growth and survival

The secreted clusterin/apolipoprotein J (CLU) protein form is a ubiquitously expressed heterodimeric glycoprotein which is differentially regulated in many severe physiological disturbance states including cell death, ageing, cancer progression, and various neurological diseases. Despite extensive efforts CLU function remains an enigma, the main cause being the intriguingly distinct and usually opposed functions in various cell types and tissues. In the current report we investigated the effects of CLU on cellular growth and survival in three human osteosarcoma (OS) cell lines, namely KH OS, Sa OS, and U-2 OS that express very low, moderate, and high endogenous steady-state CLU amounts, respectively. We found that exposure of these established OS cell lines or primary OS cells to genotoxic stress results in CLU gene induction at distinct levels that correlate negatively to CLU endogenous amounts. Following CLU-forced overexpression by means of an artificial transgene, we found that although extracellular CLU inhibits cell death in all three OS cell lines, intracellular CLU has different effects on cellular proliferation and survival in these cell lines. Transgenic KH OS cell lines adapted to moderate intracellular CLU levels were growth-retarded and became resistant to genotoxic and oxidative stress. In contrast, transgenic Sa OS and U2 OS cell lines adapted to high intracellular CLU amounts were sensitive to genotoxic and oxidative stress. In these two cell lines, the proapoptotic CLU function could be rescued by caspase inhibition. To monitor the immediate effects of heterologous CLU overexpression prior to cell adaptation, we performed transient transfections in all three OS cell lines. We found that induction of high intracellular CLU amounts increases spontaneous apoptosis in KH OS cells and reduces DNA synthesis in all three cell lines assayed. On the basis of these novel findings we propose that although extracellular CLU as well as intracellular CLU at low/moderate levels is cytoprotective, CLU may become highly cytostatic and/or cytotoxic if it accumulates intracellularly in high amounts either by direct synthesis or by uptake from the extracellular milieu.

Overexpression of clusterin in human hepatocellular carcinoma

Clusterin has been reported to play a significant role in tumorigenesis, and its overexpression occurs in various human malignancies. We examine the clusterin overexpression in human hepatocellular carcinoma (HCC) and verify its clinical usefulness as a candidate biomarker by clinicopathologic and survival analysis. We examined clusterin overexpression immunohistochemically in 100 surgically resected HCCs using the tissue microarray method. A total of 89 HCCs exhibited clusterin overexpression, in 2 distinct staining patterns, cytoplasmic (n=35) and canalicular (n=54). Clusterin positivity demonstrated an inverse correlation with tumor cell apoptosis evaluated by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay (P=0.024). Within the clusterin-positive group, cytoplasmic overexpression had a positive correlation with tumor cell proliferative activity measured by the Ki-67 labeling index (P=0.003). HCCs demonstrating cytoplasmic clusterin overexpression were associated with poor Edmondson's histological grade and high TNM stage (P <0.05). In the survival analysis, the cytoplasmic-positive group demonstrated an overall poorer prognosis than the canalicular-positive group, according to univariate and multivariate analysis (P <0.05). In HCC, clusterin may play an important role in tumorigenesis and progression, corresponding to its subcellular localization. Cytoplasmic clusterin overexpression could be a potential new prognostic marker for the aggressiveness of HCC.

Up-regulated expression of cytoplasmic clusterin in human ovarian carcinoma

BACKGROUND

Recently, tumorigenic roles of the clusterin gene in several human malignancies have been suggested, but its potential role in the development and progression of ovarian carcinoma is unclear.

METHODS

In the current study, immunohistochemistry was used to examine the expression status of clusterin in 10 normal ovaries, 20 ovarian cystadenomas, 15 borderline ovarian tumors, and 240 ovarian carcinomas (nonmetastatic and metastatic) by tissue microarray. In addition, the apoptotic index of each tumor was assessed with a terminal deoxyuridine triphosphate nick-end labeling assay.

RESULTS

Positive staining for clusterin in different ovarian tissues was observed primarily a cytoplasmic pattern. Cytoplasmic overexpression of clusterin was detected in none of the normal ovaries, in 17% of cystadenomas, in 38% of borderline tumors, and in 58% of invasive ovarian carcinomas. A significant association was observed (P < 0.001) between the overexpression of clusterin and late clinical stage according to the International Federation of Gynecology and Obstetrics staging system. In addition, the overexpression of clusterin was detected more frequently in metastatic lesions than that in their matched primary tumors. The current results also provided evidence that the overexpression of cytoplasmic clusterin in carcinomas was correlated inversely with the tumors' apoptotic index, demonstrating an antiapoptotic function of cytoplasmic clusterin in ovarian carcinomas.

CONCLUSIONS

The current results suggested that the overexpression of cytoplasmic clusterin may represent an acquired malignant phenotypic feature of ovarian carcinoma and may be one of the important factors in determining the aggressive nature of ovarian carcinoma.

Upregulation of clusterin/apolipoprotein J in lactacystin-treated SH-SY5Y cells

Clusterin (apolipoprotein J) is a highly conserved, multifunctional, vertebrate glycoprotein. Several isoforms of clusterin have been described including the predominant secreted isoform (sCLU) and several nuclear isoforms (nCLU) associated with cell death. sCLU has been shown to bind a variety of partly unfolded, stressed proteins including those associated with Lewy bodies (LBs) in patients with Parkinson's disease (PD). The development of familial and sporadic PD has been associated with the ubiquitin-proteasome system (UPS) dysfunction and aberrant protein degradation. This suggests that failure of the UPS to degrade abnormal proteins may underlie nigral degeneration and LB formation in PD. The effects of toxin-mediated proteasomal impairment on changes in gene expression and cell viability were studied in differentiated SH-SY5Y cells. Clusterin expression was increased in cells exposed for 24 hr to the proteasomal inhibitor lactacystin (10 microM) as determined by gene microarray analysis. RT-PCR showed that sCLU, not nCLU, was the major clusterin isoform expressed in both control and lactacystin-treated cells. Western blot analysis identified statistically significant increases in sCLU in total cell lysates after 24 hr of lactacystin exposure and showed that sCLU fractionates with the endoplasmic reticulum. Time-course studies demonstrated that maximal decreases in proteasome activity (4 hr) preceded maximal increases in clusterin expression (24 hr). Together these data suggest that proteasome impairment results in the upregulation of sCLU in SH-SY5Y cells, supporting the hypothesis that the association of clusterin with LBs in PD may be related to UPS failure.

Clusterin overexpression in both malignant and nonmalignant prostate epithelial cells induces cell cycle arrest and apoptosis

Expression of the castration-induced clusterin protein is incompatible with the survival of human prostate cancer cells in tissues and in cell culture. To investigate the fate of human prostate epithelial cells, when engineered to maintain expression of clusterin protein, we have used an IRES-hyg vector and hygromycin selection. PC-3 prostate tumour cells were substantially more sensitive to clusterin expression than nonmalignant PNT1a cells, showing multiple phenotypic changes including cell cycle arrest and increased apoptosis. The results strengthen the hypothesis that clusterin expression is proapoptotic. Expression of exogenous clusterin in both cell types resulted in its relocation from the cytoplasm and a nuclear accumulation of the protein, as was also seen in the same cells when apoptosis was induced by etoposide treatment. To survive clusterin expression, the PC-3 tumour cells developed apoptosis-inhibitory properties. This could have significance for the resistance of prostate cancers to chemo/radiotherapy, where clusterin overexpression is observed.

Modulation of clusterin isoforms is associated with all-trans retinoic acid-induced proliferative arrest and apoptosis of intimal smooth muscle cells

OBJECTIVE

Clusterin is a heterodimeric glycoprotein which is implicated in several biological processes. The nuclear (n-CLU) and cytoplasmic secreted (s-CLU) isoforms have recently been described, but their role is still unclear. The aim of this study is to investigate the expression of clusterin and its isoforms during proliferative arrest and apoptosis of vascular smooth muscle cells (SMCs).

METHODS AND RESULTS

Clusterin expression was evaluated by immunohistochemistry and Western blotting in human arteries and rat aortas. In human diffuse myointimal thickening, clusterin was detected in cell cytoplasm and extracellular space, whereas it was practically absent in the media. In rat aortas 15 days after ballooning, intimal cells (IT cells) overexpressed s-CLU and n-CLU, the latter mainly in the inner neointima; clusterin expression decreased at 60 days. In vitro, IT cells maintained high clusterin expression and its antisense markedly reduced proliferation and increased apoptosis. Western blotting showed that all-trans retinoic acid-induced proliferative arrest and increased alpha-smooth muscle actin expression did associate to s-CLU and B-myb reduction, whereas bax-related apoptosis was associated to a shift from the s-CLU to n-CLU isoform.

CONCLUSIONS

Clusterin overexpression characterized neointimal SMCs; s-CLU expression decreased in IT cells during all-trans retinoic acid-induced proliferative arrest and redifferentiation, whereas n-CLU overexpression was characteristic of apoptosis. Clusterin was detected in human arterial myointimal thickening and absent in the underlying media. Rat neointimal cells overexpressed clusterin and clusterin antisense oligonucleotide reduced proliferation and increased apoptosis. All-trans retinoic acid-induced proliferative arrest showed association with s-CLU reduction and n-CLU overexpression with apoptosis, supporting a different biological role of these isoforms.

Clusterin-mediated apoptosis is regulated by adenomatous polyposis coli and is p21 dependent but p53 independent

Clusterin is a widely expressed glycoprotein that has been paradoxically observed to have both pro- and antiapoptotic functions. Recent reports suggest this apparent dichotomy of function may be related to two different isoforms, one secreted and cytoplasmic, the other nuclear. To clarify the functional role of clusterin in regulating apoptosis, we examined its expression in human colon cancer tissues and in human colon cancer cell lines. We additionally explored its expression and activity using models of adenomatous polyposis coli (APC)- and chemotherapy-induced apoptosis. Clusterin RNA and protein levels were decreased in colon cancer tissues largely devoid of wild-type APC when compared with matched normal tissue controls, suggesting a means for invasive cancers to avoid apoptosis. Conversely, induction of apoptosis by expression of wild-type APC or by treatment with chemotherapy led to increased clusterin RNA and protein levels localizing to apoptotic nuclei. We found that transient transfection of clusterin to colon cancer cell lines directly enhanced basal and chemotherapy-induced apoptosis. Clusterin-induced apoptosis was inhibited by antisense clusterin and was found to be highly dependent on p21 but not p53 expression, yet a deficit in p21 can be subverted by clusterin transfection. Collectively, these data support the hypothesis that nuclear clusterin function is proapoptotic when induced by APC or chemotherapy in the context of p21 expression. Absent of p21, clusterin in not induced, and apoptosis is significantly inhibited. These data support a potential therapeutic role for clusterin in enhancing chemotherapy-induced apoptosis and in promoting apoptosis in cells deficient in p21.

Progressive changes in regulation of apolipoproteins E and J in glial cultures during postnatal development and aging

Apolipoprotein (Apo) E and ApoJ are lipid- and cholesterol-carriers in the central nervous system and are implicated in age-related neurodegenerative diseases. The primary source of secreted ApoE and ApoJ (clusterin) in the brain is glia. Regulation of these apolipoproteins in mixed glial cultures from rat cerebral cortex differed most strongly between neonatal- and adult-derived glia. Basal secretion of ApoJ was two-fold greater in neonatal than adult glia. Responses to cytokines also differed by donor age. In adult glia, IL-6 increased ApoE secretion, but slightly decreased ApoJ. Both IL-1 beta and TNFalpha treatments increased ApoJ secretion from adult glia, with little effect on ApoE. In contrast to adult glia, neonatal ApoJ secretion did not respond to IL-1 beta, IL-6, or TNFalpha, and ApoE secretion from neonatal glia was slightly increased by IL-6. These differences may contribute to age-related neuroinflammatory processes, and are pertinent to the general use of neonatal-derived primary glia in models for neurodegenerative disease.

Isolation and characterization of a novel gene CLUAP1 whose expression is frequently upregulated in colon cancer

To disclose mechanisms of colorectal carcinogenesis and identify novel diagnostic markers and drug targets for treatment of these tumors, we previously analysed the expression profiles of 11 colorectal cancers using a genome-wide cDNA microarray containing 23,040 genes. Among the genes commonly transactivated in the cancers, we identified a novel human gene, which we termed CLUAP1 (clusterin-associated protein 1). It encodes a nuclear protein of 413 amino acids containing a coiled-coil domain. To investigate its function, we searched for CLUAP1-interacting proteins using yeast two-hybrid system and identified nuclear Clusterin. Expression of CLUAP1 was gradually increased in the late S to G2/M phases of cell cycle and it returned to the basal level in the G0/G1 phases. Suppression of this gene by short interfering RNAs resulted in growth retardation in the transfected cells. These data provide better understanding of colorectal carcinogenesis, and inactivation of CLUAP1 may conceivably serve in the future as a novel therapeutic intervention for treatment of colon cancer.

Intracellular Clusterin Induces G2-M Phase Arrest and Cell Death in PC-3 Prostate Cancer Cells1

Enhanced clusterin gene expression has been related frequently to organ remodeling, tissue involution, and cell death. Whether clusterin represents a leading cause or a consequence of apoptosis induction is still a matter of debate. Clusterin is known as an extracellular secreted glycoprotein in the mature form. However, truncated isoforms of the protein and nuclear localization of clusterin have been described recently in association to cell death. Here, we show the biological effects triggered in PC-3 androgen-independent prostate cancer cells by overexpression of an intracellular, not secreted form of clusterin (intracellular-clusterin). Transient transfection of PC-3 cells with intracellular-clusterin resulted in nuclear localization signal-independent massive nuclear localization of the protein leading to G2-M phase blockade followed by caspase-dependent apoptosis. Constitutive expression of intracellular-clusterin (pFLAG- intracellular-clusterin) in recombinant PC-3 cells caused clonogenic toxicity. The rare pFLAG-intracellular clusterin surviving clones showed inhibition of the proliferation rate and altered phenotype with impaired mitosis and endoreduplication. In these cells, caspase-independent cell death was induced. Impaired cell cycle progression in pFLAG-intracellular-clusterin clones was associated to arrest at the G2-M checkpoint by down-regulation of the mitotic complex cyclin B1/cyclin-dependent kinase 1. Intriguingly, intracellular-clusterin was localized exclusively in the cytoplasm in stably transfected cells, suggesting a negative correlation between nuclear clusterin accumulation and cell survival. These findings may possibly explain the conflicting results obtained in different laboratories, suggesting that clusterin might be a proapoptotic or a survival gene, also opening new perspectives for the characterization of androgen-independent and apoptosis-resistant prostate cancer cells.

The Retinoid Antagonist MX781 Induces Clusterin Expression in Prostate Cancer Cells via Heat Shock Factor-1 and Activator Protein-1 Transcription Factors

Retinoids mediate numerous biological responses through the transcriptional activation of nuclear retinoid receptors. Due to their antiproliferative activity, retinoids have shown promise as anticancer agents. Synthetic analogs have been described that selectively activate one subset of the retinoid receptors or inhibit their transcriptional activity. Some of these compounds exhibit strong anticancer activity, which is associated with their ability to induce apoptosis. Here we describe that the retinoid antagonist MX781 causes a substantial increase of clusterin mRNA and protein levels in prostate carcinoma cells. In contrast, retinoic acid and other synthetic agonists and antagonists show no effect on clusterin mRNA/protein levels. Induction of clusterin mRNA is associated with transcriptional activation of the clusterin promoter, which requires the proximal -218-bp region containing binding sites for heat shock factor (HSF)-1, activator protein (AP)-2, and AP-1 transcription factors. MX781 slightly induces AP-1 DNA binding activity, and mutation of the AP-1 site differentially affects the activation of the clusterin promoter in a cell type-specific manner. In contrast, a robust increase of HSF-1 DNA binding activity is observed in all cancer cell lines examined, and mutation of the heat shock element site in the clusterin promoter completely abolishes MX781-induced transcriptional activation in PC3 and DU145 cells. Other agonist retinoid-related molecules also induce AP-1 activity, but not HSF-1, and elicit no effect on clusterin expression levels. These data point to HSF-1 as an important factor regulating clusterin expression in response to MX781, although AP-1 activity may also participate in a cell type-specific manner.

Cell detachment and apoptosis induction of immortalized human prostate epithelial cells are associated with early accumulation of a 45 kDa nuclear isoform of clusterin

Clusterin, ubiquitously distributed in mammalians, was cloned and identified as the most potently induced gene during rat prostate involution following androgen deprivation. Also found to be involved in many other patho-physiological processes, its biological significance is still controversial, particularly with regard to apoptosis. We previously showed that transient over-expression of clusterin blocked cell cycle progression of simian-virus-40-immortalized human prostate epithelial cell lines PNT1A and PNT2. We show in the present study that the accumulation of an intracellular 45 kDa clusterin isoform was an early event closely associated with death of PNT1A cells caused by cell detachment followed by apoptosis induction (anoikis). Cell morphological changes, decreased proliferation rate and cell cycle arrest at G0/G1-S-phase checkpoint were all strictly associated with the production and early translocation to the nucleus of a 45 kDa clusterin isoform. Later, nuclear clusterin was found accumulated in detached cells and apoptotic bodies. These results suggest that a 45 kDa isoform of clusterin, when targeted to the nucleus, can decrease cell proliferation and promotes cell-detachment-induced apoptosis, suggesting a possible major role for clusterin as an anti-proliferative gene in human prostate epithelial cells.