Anti-sense inhibition of small-heat-shock-protein (HSP27) expression in MCF-7 mammary-carcinoma cells induces their spontaneous acquisition of a secretory phenotype

Heat shock protein 27 promotes cell cycle progression by down-regulating E2F transcription factor 4 and retinoblastoma family protein p130

Heat shock protein 27 (HSP27) protects cells under stress. Here, we demonstrate that HSP27 also promotes cell cycle progression of MRC-5 human lung fibroblast cells. Serum starvation for 24 h induced G₁ arrest in these cells, and upon serum refeeding, the cells initiated cell cycle progression accompanied by an increase in HSP27 protein levels. HSP27 levels peaked at 12 h, and transcriptional up-regulation of six G₂/M-related genes (CCNA2, CCNB1, CCNB2, CDC25C, CDCA3, and CDK1) peaked at 24-48 h. siRNA-mediated HSP27 silencing in proliferating MRC-5 cells induced G₂ arrest coinciding with down-regulation of these six genes. Of note, the promoters of all of these genes have the cell cycle-dependent element and/or the cell cycle gene-homology region. These promoter regions are known to be bound by the E2F family proteins (E2F-1 to E2F-8) and retinoblastoma (RB) family proteins (RB1, p107, and p130), among which E2F-4 and p130 were strongly up-regulated in HSP27-knockdown cells. E2F-4 or p130 knockdown concomitant with the HSP27 knockdown rescued MRC-5 cells from G₂ arrest and up-regulated the six cell cycle genes. Moreover, we observed cellular senescence in MRC-5 cells on day 3 after the HSP27 knockdown, as evidenced by increased senescence-associated β-gal activity and up-regulated inflammatory cytokines. The cellular senescence was also suppressed by the concomitant knockdown of E2F-4/HSP27 or p130/HSP27. Our findings indicate that HSP27 promotes cell cycle progression of MRC-5 cells by suppressing expression of the transcriptional repressors E2F-4 and p130.

Heat shock proteins in the retina: Focus on HSP70 and alpha crystallins in ganglion cell survival

Heat shock proteins (HSPs) belong to a superfamily of stress proteins that are critical constituents of a complex defense mechanism that enhances cell survival under adverse environmental conditions. Cell protective roles of HSPs are related to their chaperone functions, antiapoptotic and antinecrotic effects. HSPs' anti-apoptotic and cytoprotective characteristics, their ability to protect cells from a variety of stressful stimuli, and the possibility of their pharmacological induction in cells under pathological stress make these proteins an attractive therapeutic target for various neurodegenerative diseases; these include Alzheimer's, Parkinson's, Huntington's, prion disease, and others. This review discusses the possible roles of HSPs, particularly HSP70 and small HSPs (alpha A and alpha B crystallins) in enhancing the survival of retinal ganglion cells (RGCs) in optic neuropathies such as glaucoma, which is characterized by progressive loss of vision caused by degeneration of RGCs and their axons in the optic nerve. Studies in animal models of RGC degeneration induced by ocular hypertension, optic nerve crush and axotomy show that upregulation of HSP70 expression by hyperthermia, zinc, geranyl-geranyl acetone, 17-AAG (a HSP90 inhibitor), or through transfection of retinal cells with AAV2-HSP70 effectively supports the survival of injured RGCs. RGCs survival was also stimulated by overexpression of alpha A and alpha B crystallins. These findings provide support for translating the HSP70- and alpha crystallin-based cell survival strategy into therapy to protect and rescue injured RGCs from degeneration associated with glaucomatous and other optic neuropathies.

A rapid LC-MS/MS method for quantification of CSUOH0901, a novel antitumor agent, in rat plasma

CSUOH0901, a novel anticancer derivative of nimesulide, exhibits very promising anticancer activities in various cancer cell lines. In order to support further pharmacological and toxicological studies of this promising anticancer drug candidate, an LC-MS/MS method was developed and validated in accordance with the US Food and Drug Administration guidelines. The drug molecules were extracted from plasma samples by protein precipitation and then analyzed with LC-ESI-MS/MS. An excellent analyte separation was achieved using a phenomenex C18 column with a mobile phase of 90% methanol and 5 m m of ammonium formate. The validated linear dynamic range was between 0.5 and 100 ng/mL and the achieved correlation coefficient (r(2)) was >0.9996. The results of inter- and intra-day precision and accuracy were satisfactory, that is, <12% for accuracy and within ±5% for precision at a low and high quality control concentrations, respectively. In addition, the analyte and internal standard (JCC76) were found to be stable under the storage conditions at -20°C for about 2 months. Hence, the acquired results proved that the LC-ESI-MS/MS method developed is precise, accurate and selective for the quantification of CSUOH0901 in plasma, and can be used for pharmacokinetic studies.

Heat Shock Proteins: Intestinal Gatekeepers that Are Influenced by Dietary Components and the Gut Microbiota

Trillions of microorganisms that inhabit the intestinal tract form a diverse and intricate ecosystem with a deeply embedded symbiotic relationship with their hosts. As more detailed information on gut microbiota complexity and functional diversity accumulates, we are learning more about how diet-microbiota interactions can influence the immune system within and outside the gut and host health in general. Heat shock proteins are a set of highly conserved proteins that are present in all types of cells, from microbes to mammals. These proteins carry out crucial intracellular housekeeping functions and unexpected extracellular immuno-regulatory features in order to maintain the mucosal barrier integrity and gut homeostasis. It is becoming evident that the enteric microbiota is one of the major determinants of heat shock protein production in intestinal epithelial cells. This review will focus on the interactions between diet, gut microbiota and their role for regulating heat shock protein production and, furthermore, how these interactions influence the immune system and the integrity of the mucosal barrier.

Small heat shock proteins and the cytoskeleton: an essential interplay for cell integrity?

The cytoskeleton is a highly complex network of three major intracellular filaments, microfilaments (MFs), microtubules (MTs) and intermediate filaments (IFs). This network plays a key role in the control of cell shape, division, functions and interactions in animal organs and tissues. Dysregulation of the network can contribute to numerous human diseases. Although small HSPs (sHSPs) and in particular HSP27 (HSPB1) or αB-crystallin (HSPB5) display a wide range of cellular properties, they are mostly known for their ability to protect cells under stress conditions. Mutations in some sHSPs have been found to affect their ability to interact with cytoskeleton proteins, leading to IF aggregation phenotypes that mimick diseases related to disorders in IF proteins (i.e. desmin, vimentin and neuro-filaments). The aim of this review is to discuss new findings that point towards the possible involvement of IFs in the cytoprotective functions of sHSPs, both in physiological and pathological settings, including the likelihood that sHSPs such as HSPB1 may play a role during epithelial-to-mesenchymal transition (EMT) during fibrosis or cancer progression. This article is part of a Directed Issue entitled: Small HSPs in physiology and pathology.

Chaperones in cell cycle regulation and mitogenic signal transduction: a review

Chaperones/heat shock proteins (HSPs) of the HSP90 and HSP70 families show elevated levels in proliferating mammalian cells and a cell cycle-dependent expression. They transiently associate with key molecules of the cell cycle control system such as Cdk4, Wee-1, pRb, p53, p27/Kip1 and are involved in the nuclear localization of regulatory proteins. They also associate with viral oncoproteins such as SV40 super T, large T and small t antigen, polyoma large and middle S antigen and EpsteinBarr virus nuclear antigen. This association is based on a J-domain in the viral proteins and may assist their targeting to the pRb/E2F complex. Small HSPs and their state of phosphorylation and oligomerization also seem to be involved in proliferation and differentiation. Chaperones/HSPs thus play important roles within cell cycle processes. Their exact functioning, however, is still a matter of discussion. HSP90 in particular, but also HSP70 and other chaperones associate with proteins of the mitogen-activated signal cascade, particularly with the Src kinase, with tyrosine receptor kinases, with Raf and the MAP-kinase activating kinase (MEK). This apparently serves the folding and translocation of these proteins, but possibly also the formation of large immobilized complexes of signal transducing molecules (scaffolding function).

Low-scale phosphoproteome analyses identify the mTOR effector p70 S6 kinase 1 as a specific biomarker of the dual-HER1/HER2 tyrosine kinase inhibitor lapatinib (Tykerb) in human breast carcinoma cells

BACKGROUND

Discovery of key proliferative and/or survival cascades closely linked to the biological effects of human epidermal growth factor receptor (HER) 1 (erbB-1) and/or HER2 (erbB-2) inhibitors may identify a priori mechanisms responsible for the development of acquired resistance in breast cancer disease. Here, we took advantage of a semiquantitative protein array technology to identify intracellular oncogenic kinases that distinctively correlate with breast cancer cell sensitivity/resistance to the dual-HER1/HER2 tyrosine kinase inhibitor lapatinib (Tykerb(R)).

MATERIALS AND METHODS

MCF-7 cells were forced to overexpress HER2 following stable transduction with pBABE-HER2 retroviruses. The Human Phospho-MAPK Array Proteome Profilertrade mark (R&D Systems) was used to molecularly assess the effects of both the mono-HER2 inhibitor trastuzumab (Herceptintrade mark) and the dual-HER1/HER2 inhibitor lapatinib on 21 different oncogenic kinases. A model of acquired resistance to lapatinib (MCF-7/HER2-Lap10 cells) was established by chronically exposing MCF-7/HER2 cells to increasing concentrations of lapatinib for >10 months.

RESULTS

Treatment of MCF-7/HER2 cells with either trastuzumab or lapatinib similarly impaired HER2-enhanced activation status (i.e. phosphorylation) of the mitogen-activated protein kinases, c-Jun N-terminal kinases 1-3 and p38alpha/beta/gamma/delta and of the serine/threonine kinases AKT, glycogen synthase kinase-3, p90 ribosomal s6 kinase1/2, and mitogen- and stress-activated protein kinase1/2. Trastuzumab was less effective than lapatinib at blocking extracellular-signal regulated kinase (ERK) 1/2 and, notably, it failed to deactivate the mammalian target of rapamycin (mTOR) effector p70S6K1. Conversely, lapatinib treatment caused a drastic decrease in the phosphorylation of p70S6K1 at ERK1/2-regulated sites (Thr(421)/Ser(424)) and, as a consequence, p70S6K1 activity measured by its phospho-Thr(389) levels was abolished. The mTOR inhibitor rapamycin was found to supraadditively increase lapatinib efficacy in MCF-7/HER2 cells [ approximately 10-fold enhancement; combination index (CI(50)) = 0.243 < 1.0 = additivity, P < 0.001] but not in p70S6K1 gene-amplified MCF-7 parental cells ( approximately 1.3-fold enhancement; CI(50) = 0.920 congruent with 1.0 = additivity). Lapatinib-resistant MCF-7/HER2-Lap10 cells, which are capable of growing in the continuous presence of 10 microM lapatinib without significant effects on cell viability, notably exhibited a lapatinib-insensitive hyperphosphorylation of p70S6K1. Rapamycin cotreatment suppressed p70S6K1 hyperactivation and synergistically resensitized MCF-7/HER2-Lap10 cells to lapatinib (>20-fold increase in lapatinib-induced cytotoxicity; CI(50) = 0.175 < 1.0 = additivity).

CONCLUSIONS

Serine-threonine kinase p70S6K1, a marker for mTOR activity that regulates protein translation, constitutes a specific biomarker for the biological effects of the dual-HER1/HER2 inhibitor lapatinib. The clinical implications of our data are that the efficacy of lapatinib might be enhanced with therapies that target the mTOR pathway. Rapamycin analogues such as CCI-779 (Temsirolimus) and RAD001 (Everolimus) may warrant further clinical evaluation to effectively delay or prevent the development of acquired resistance to lapatinib in HER2-positive breast cancer patients.

Gene expression profiling in the mammary gland of rats treated with 7,12-dimethylbenz[a]anthracene

Identification of molecular markers of early-stage breast cancer development is important for the diagnosis and prevention of the disease. In the present study, we used microarray analysis to examine the differential expression of genes in the rat mammary gland soon after treatment with a known chemical carcinogen, 7,12-dimethylbenz[a]anthracene (DMBA), and prior to tumor development. Six weeks after DMBA, differential expression of multiple genes involved in cell growth, differentiation and microtubule dynamics were observed. Gene expression changes were further validated by a combination of techniques, including real-time PCR, RT-PCR, Western blotting and immunohistochemistry. An inhibition of differentiation in this early stage was suggested by the lower expression of beta-casein and transferrin and higher expression of hsp27 in glands from DMBA-treated rats. Possible cell cycle deregulation was indicated by an increased expression of cyclin D1 and hsp86, a heat shock protein associated with cyclin D1. Prior to tumor development, DMBA increased cellular proliferation as detected by Ki-67 and stathmin immunostaining in histologically normal mammary gland. Genes regulating microtubule function, including stathmin, Ran, alpha-tubulin and hsp27, were all overexpressed in the mammary gland of DMBA-treated rats, raising the possibility that disruption of microtubule dynamics and abnormal mitosis may be critical events preceding breast cancer development. Several of the altered proteins, including hsp27, hsp86 and stathmin, may ultimately serve as markers of early breast cancer development.

Paclitaxel inhibits expression of heat shock protein 27 in ovarian and uterine cancer cells

The purpose of the study was to determine whether paclitaxel inhibits the expression of heat shock protein 27 (HSP27) in two gynecologic cancer cell lines compared with other antineoplastic agents having different cytotoxic mechanisms. BG-1 ovarian cancer cells and HeLa uterine cancer cells were treated with a tubulin depolymerization inhibitor (paclitaxel), a topoisomerase-II inhibitor (etoposide), and two tubulin polymerization inhibitors (colcemid and vincristine). Cell kills were evaluated by counting the number of cells. Propidium iodide staining and flow cytometric analysis were applied for the determination of cell-cycle perturbation. HSP27 was stained by the indirect immunofluorescence technique and analyzed with a flow cytometer. In both BG-1 and HeLa cells, growth arrest and G2 / M accumulation were dependent on the dose of each cytotoxic agent. There were positive correlations between HSP27 overexpression and growth arrest and G2 / M accumulation when the cell lines were treated with etoposide, colcemid, or vincristine, but not with paclitaxel. Paclitaxel completely inhibited the expression of HSP27. The results of this study indicated that paclitaxel may possess unique mechanisms able to overcome drug resistance by inhibiting HSP27 expression.

The anti-apoptosis survivin gene and its role in human cancer: an overview

Malignant transformation of cells is accompanied by multiple genetic abnormalities with aberrant expression of genes. By using the reverse transcriptase polymerase chain reaction (RT-PCR) assay, we have assessed the regulation of survivin gene expression in a prospectively collected series of 83 human non small-cell lung cancers. Survivin gene transcripts were identified in 71 (85.5%) of the tumor samples, while they were detected in only 10 (12%) of the paired histopathologically normal lung samples. Furthermore, a diminished overall survival was associated with survivin expression (Log-rank, P=0.01). This review discusses the structure, expression, and function of the survivin gene. It presents updated pooled data on survivin, analyzed by either immunochemistry or by RT-PCR, and the clinical correlates of aberrant expression in several tumors. We conclude that estimation of survivin gene transcripts by RNA techniques may have relevant applications in the prognostic and therapeutic assessment of lung cancer.

Testis-specific human small heat shock protein HSPB9 is a cancer/testis antigen, and potentially interacts with the dynein subunit TCTEL1

Searching EST databases for new members of the human small heat shock protein family, we recently identified HSPB9, which is expressed exclusively in testis as determined by Northern blotting (Kappé et al., Biochim. Biophys. Acta 1520, 1-6, 2001). Here we confirm this testis-specific expression pattern by RT-PCR in a larger series of normal tissues. Interestingly, while screening HSPB9 ESTs, we also noted expression in tumours, which could be verified by RT-PCR. Protein expression of HSPB9 was also detected in normal human testis and various tumour samples using immunohistochemical staining. We thus conclude that HSPB9 belongs to the steadily growing number of cancer/testis antigens. To get a better understanding of the function of HSPB9, we performed a yeast two-hybrid screen to search for HSPB9-interacting proteins. TCTEL1, a light chain component of cytoplasmic and flagellar dynein, interacted in both the yeast two-hybrid system and in immunoprecipitation experiments with HSPB9. Additionally, immunohistochemical staining showed co-expression of HSPB9 and TCTEL1 in similar stages of spermatogenesis and in tumour cells. The possible functional significance of this interaction is discussed.

Role of BRCA1 in heat shock response

The heat shock response is an evolutionarily conserved response to heat and other stresses that promotes the maintenance of key metabolic functions and cell survival. We report that exposure of human prostate (DU-145) and breast (MCF-7) cancer cells to heat (42 degrees C) caused a rapid disappearance of the breast cancer susceptibility gene-1 (BRCA1) protein, starting at approximately 1 h after the onset of heating and slightly lagging behind the increase in heat shock protein 70 (HSP70) levels. The heat-induced loss of BRCA1 occurred at the protein level, since: (1) BRCA1 mRNA expression was unaffected; and (2) the BRCA1 protein loss was also observed in DU-145 cells that expressed exogenous wild-type BRCA1 (wtBRCA1). In addition to heat regulation of BRCA1 protein levels, we also found that BRCA1 could modulate the heat shock response. Thus, wtBRCA1 overexpressing DU-145 cell clones showed significantly decreased sensitivity to heat-induced cytotoxicity; and Brca1 mutant mouse embryo fibroblasts showed increased sensitivity to heat. The DU-145 wtBRCA1 clones also showed increased expression of the small heat shock protein HSP27; and reporter assays revealed that wtBRCA1 stimulated a two to four-fold increase in HSP27 promoter activity, consistent with its ability to upregulate HSP27 mRNA and protein levels. In studies using epitope-tagged truncated BRCA1 proteins, the ability to stimulate the HSP27 promoter and to mediate heat-induced degradation required the amino-terminus but not the carboxyl-terminus of BRCA1. Although the heat-induced loss of BRCA1 appeared to be due to protein degradation, various protein metabolic agents (or combinations) failed to block this event, including: MG132 (a 26S proteasomal inhibitor), N-acetyl-leucyl-leucyl-norleucinal (a calpain inhibitor), z-VAD-fmk (a pan-caspase inhibitor), and ammonium chloride and chloroquine (which stabilize lysosomes). These findings suggest that in addition to its other functions, BRCA1 may participate in mammalian heat shock response pathways.

Proteomics reveals protein profile changes in doxorubicin--treated MCF-7 human breast cancer cells

MCF-7 cells are extensively used as a cell model to investigate human breast tumors and the cellular mechanism of antitumor drugs such as doxorubicin (DOX), an anthracycline antitumor drug widely used in clinical chemotherapy. To understand the effects of DOX on the protein expression, we perform a comprehensive proteomics to survey global changes in proteins after DOX treatment in MCF-7 cells. Exposure of MCF-7 cells to 0.1 microM DOX for 2 days induced a differentiation-like phenotype with prominent perinuclear autocatalytic vacuoles, abundant filamentous material, and irregular microvilli at the cell surface. In this study, we also present a proteome reference map of MCF-7 cells with 21 identified protein spots via analysis of N-terminal sequencing, mass spectrometry, immunoblot and/or computer matching with protein database. Based on the proteome map, we found that DOX causes a markedly decrease in the levels of three isoforms of heat shock protein 27 (HSP27) whereas the levels of other stress associated proteins including HSP60, calreticulin, and protein disulfide isomerase were not significantly altered in DOX-treated MCF-7 cells. Taken together, we suggest that that action of DOX on breast tumor cells may be partly related to dysregulation of HSP27 expression. Modulation of HSP27 levels may be a clinically useful potential target for design of antitumor drugs and controlling breast tumor growth.

Actin cytoskeleton and small heat shock proteins: how do they interact?

Actin and small heat shock proteins (sHsps) are ubiquitous and multifaceted proteins that exist in 2 reversible forms, monomers and multimers, ie, the microfilament of the cytoskeleton and oligomers of the sHsps, generally, supposed to be in a spherical and hollow form. Two situations are described in the literature, where the properties of actin are modulated by sHsps; the actin polymerization is inhibited in vitro by some sHsps acting as capping proteins, and the actin cytoskeleton is protected by some sHsps against the disruption induced by various stressful conditions. We propose that a direct actin-sHsp interaction occurs to inhibit actin polymerization and to participate in the in vivo regulation of actin filament dynamics. Protection of the actin cytoskeleton would result from an F-actin-sHsp interaction in which microfilaments would be coated by small oligomers of phosphorylated sHsps. Both proteins share common structural motives suggesting direct binding sites, but they remain to be demonstrated. Some sHsps would behave with the actin cytoskeleton as actin-binding proteins capable of either capping a microfilament when present as a nonphosphorylated monomer or stabilizing and protecting the microfilament when organized in small, phosphorylated oligomers.

MCF-7 mammary tumour cells express the myeloid cell differentiation controlling factor, serine protease 3/myeloblastin

Our previous data indicated that HSP27 plays a role in MCF-7 cell differentiation similar to that it has in HL-60 cells. In the latter case, this involves a control of its levels by proteinase 3/myeloblastin (PR3/Mbn), a serine proteinase hitherto considered specific of the myeloid lineage. Having observed that the treatment of MCF-7 cells with the serine protease inhibitor N-tosyl-l-phenylalanine-chloromethyl ketone (TPCK) increased their content in HSP27 and induced them to acquire a secretory phenotype, we undertook this work to test the assumption that an enzyme similar or identical to PR3/Mbn might be expressed in this cell line. The data show that MCF-7 cells exhibited specific immunopositivity for a monoclonal antibody against PR3/Mbn. Western blot analysis of immunoprecipitates from MCF-7 cell extracts, obtained and checked with PR3/Mbn monoclonal antibodies, confirmed the presence of the 35 kDa glycosylated and 29 kDa mature forms of the protein. Finally, Northern blot analysis confirmed the expression of the corresponding mRNA. Together with our data with TPCK, this substantiates our hypothesis that, as in HL-60 cells, regulation of MCF-7 cells differentiation might involve a postranslation control on HSP27 levels by a serine protease.

Overexpression of murine small heat shock protein HSP25 interferes with chondrocyte differentiation and decreases cell adhesion

Although multiple functions for the small heat shock protein HSP25 have been proposed, its specific role during developmental and differentiation processes is not known. Cartilage is one of the tissues in which HSP25 is specifically and highly expressed during development. C1 cells, able to form aggregates in vitro, can be induced to differentiate into chondrocytes. In this study, we generated two stable transfected clones overexpressing HSP25 at two different levels. Cell morphology and growth rate were modified in both clones, although the actin content and distribution did not seem to be altered. Overexpressing clones had more difficulties in coalescing, leading to smaller aggregates and they did not differentiate into chondrocytes. Subsequently, these aggregates tended to dissociate into loose masses of dying cells. The strength of all these effects was directly correlated to the level of HSP25 overexpression. These data suggest that overexpressing HSP25 decreases cellular adhesion and interferes with chondrocyte differentiation.