ERK1/2-mediated activation of DRP1 regulates mitochondrial dynamics and apoptosis in chondrocytes.

OBJECTIVE: To determine the Dynamin-related protein 1 (DRP1) regulation of mitochondrial fission in chondrocytes under pathological conditions, an area which is underexplored in osteoarthritis pathogenesis. DESIGN: DRP1 protein expression was determined by immunohistochemistry (IHC) or immunofluorescence (IF) staining of cartilage sections. IL-1ß-induced DRP1 mRNA expression in chondrocytes was quantified by qPCR and protein expression by immunoblotting. Mitochondrial fragmentation in chondrocytes was visualized by MitoTracker staining or IF staining of mitochondrial marker proteins or by transient expression of mitoDsRed. Mitochondrial reactive oxygen species (ROS) levels were determined by MitoSOX staining. Apoptosis was determined by lactate dehydrogenase (LDH) release assay, Caspase 3/7 activity assay, propidium iodide (PI), and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and IF staining of cleaved caspase 3. Cytochrome c release was determined by confocal microscopy. Surgical destabilization of the medial meniscus (DMM) was used to induce osteoarthritis (OA) in mice. RESULTS: Expression of DRP1 and mitochondrial damage was high in human OA cartilage and in the joints of mice subjected to DMM surgery which also showed increased chondrocytes apoptosis. IL-1ß-induced mitochondrial network fragmentation and chondrocyte apoptosis via modulation of DRP1 expression and activity and induce apoptosis via Bax-mediated release of Cytochrome c. Pharmacological inhibition of DRP1 activity by Mdivi-1 blocked IL-1ß-induced mitochondrial damage and apoptosis in chondrocytes. Additionally, IL-1ß-induced activation of extracellular signal-regulated kinase 1/2 (ERK1/2) is crucial for DRP1 activation and induction of mitochondrial network fragmentation in chondrocytes as these were blocked by inhibiting ERK1/2 activation. CONCLUSIONS: These findings demonstrate that ERK1/2 is a critical player in DRP1-mediated induction of mitochondrial fission and apoptosis in IL-1ß-stimulated chondrocytes.

Lysosomal dysfunction in osteoarthritis and aged cartilage triggers apoptosis in chondrocytes through BAX mediated release of Cytochrome c.

OBJECTIVE: Lysosomes are the major catabolic organelle of the cell and regulate the macromolecular and organelle turnover and programmed cell death. Here, we investigated the lysosome dysfunction in cartilage and its role in chondrocytes apoptosis and the associated mechanism. DESIGN: Lysosomal acidification in Osteoarthritis (OA) and aged cartilage was determined by LysoSensor staining. Lysosomal function in chondrocytes was blocked by siRNA mediated depletion of Lysosomal Associated Membrane Protein 2 (LAMP2) or with lysosome inhibitors. Chondrocyte apoptosis was determined by LDH release, Caspase-3/7 activation, TUNEL and PI uptake assays. Loss of mitochondrial membrane potential (MMP/ΔΨM) and mitochondrial superoxide level was determined by JC-1 and MitoSOX staining, respectively. Colocalization of mitochondria with BCL2 associated X (BAX) and Cytochrome c was determined by immunostaining. Destabilization of medial meniscus (DMM) was performed to induce OA in mice. RESULTS: Lysosomal acidification was found to be significantly decreased in aged mouse and human and mouse OA cartilage which also showed increased chondrocyte apoptosis. Inhibition of lysosomal function resulted in increased oxidative stress, accumulation of dysfunctional mitochondria and apoptosis in chondrocytes in monolayer and in cartilage explant cultures. Depletion of LAMP2 expression or treatment of chondrocytes with lysosomal function inhibitors increased the expression and mitochondrial translocation of BAX leading to Cytochrome c release. Lysosomal dysfunction-induced apoptosis in chondrocytes was not blocked by antioxidants MitoTempo or Diphenyleneiodonium (DPI) but was abrogated by inhibiting BAX. CONCLUSION: Lysosomal dysfunction induce apoptosis in chondrocytes through BAX-mediated mitochondrial damage and release of Cytochrome c. Our data points to lysosomal function restoration and/or BAX inhibition in chondrocytes as a therapeutic approach for OA.

tRNA-derived fragments (tRFs) regulate post-transcriptional gene expression via AGO-dependent mechanism in IL-1ß stimulated chondrocytes.

OBJECTIVES: Recent studies have shown that tRNA-derived RNA fragments (tRFs) are novel regulators of post-transcriptional gene expression. However, the expression profiles and their role in post-transcriptional gene regulation in chondrocytes is unknown. Here, we determined tRFs expression profile and explored tRF-3003a role in post-transcriptional gene regulation in IL-1ß stimulated chondrocytes. METHODS: We used qPCR arrays to determine tRNAs and tRFs expression in age- and sex-matched primary human OA chondrocytes and TC28/I2 cells stimulated with IL-1ß. Chondrocytes were transfected with tRNA-CysGCA overexpression plasmid or tRF-3003a mimic and 3'UTR luciferase reporter plasmids of mRNAs harboring predicted tRF target "seed sequence". The AGO-RNA-induced silencing complex (AGO-RISC)-dependent repressive activity of tRF-3003a was determined by siRNA-mediated knockdown of AGO2. RESULTS: IL-1ß increased the expression levels of specific tRNAs and of tRF-3003a, a type 3 tRF produced by the cleavage of tRNA-CysGCA. tRF-3003a "seed sequence" was identified in the 3'UTR of JAK3 mRNA and tRNA-CysGCA overexpression or transfection of a tRF-3003a mimic in chondrocytes downregulated JAK3 expression and significantly reduced the activity of the 3'UTR reporter. RIP assay showed enrichment of tRF-3003a into AGO2/RISC in IL-1ß treated chondrocytes. The suppressive effect of tRF-3003a on JAK3 3'UTR reporter was abrogated with siRNA-mediated depletion of AGO2. CONCLUSIONS: We demonstrate that under pathological conditions chondrocytes display perturbations in the expression profile of specific tRNAs and tRFs. Furthermore, a specific tRF namely tRF-3003a can post-transcriptionally regulate JAK3 expression via AGO/RISC formation in chondrocytes. Identification of this novel mechanism may be of value in the design of precision therapies for OA.

Parkin clearance of dysfunctional mitochondria regulates ROS levels and increases survival of human chondrocytes.

OBJECTIVE: Mitochondrial dysfunction, oxidative stress and chondrocyte death are important contributors to the development and pathogenesis of osteoarthritis (OA). In this study, we determined the expression and role of Parkin in the clearance of damaged/dysfunctional mitochondria, regulation of reactive oxygen species (ROS) levels and chondrocyte survival under pathological conditions. METHODS: Human chondrocytes were from the unaffected area of knee OA cartilage (n = 12) and were stimulated with IL-1ß to mimic pathological conditions. Mitochondrial membrane depolarization and ROS levels were determined using specific dyes and flow cytometry. Autophagy was determined by Western blotting for ATG5, Beclin1, immunofluorescence staining and confocal microscopy. Gene expression was determined by RT-qPCR. siRNA, wild-type and mutant Parkin plasmids were transfected using Amaxa system. Apoptosis was determined by PI staining of chondrocytes and TUNEL assay. RESULTS: IL-1ß-stimulated OA chondrocytes showed high levels of ROS generation, mitochondrial membrane damage, accumulation of damaged mitochondria and higher incidence of apoptosis. IL-1ß stimulation of chondrocytes with depleted Parkin expression resulted in sustained high levels of ROS, accumulation of damaged/dysfunctional mitochondria and enhanced apoptosis. Parkin translocation to depolarized/damaged mitochondria and recruitment of p62/SQSTM1 was required for the elimination of damaged/dysfunctional mitochondria in IL-1ß-stimulated OA chondrocytes. Importantly we demonstrate that Parkin elimination of depolarized/damaged mitochondria required the Parkin ubiquitin ligase activity and resulted in reduced ROS levels and inhibition of apoptosis in OA chondrocytes under pathological conditions. CONCLUSIONS: Our data demonstrates that Parkin functions to eliminate depolarized/damaged mitochondria in chondrocytes which is necessary for mitochondrial quality control, regulation of ROS levels and chondrocyte survival under pathological conditions.

Sequencing in the presence of betaine: Improvement in sequencing of the localized repeat sequence regions.

The presence of several copies of the same class of repetitive element in DNA templates increases the probability of ambiguous base calling caused by band compression artifacts in the BigDye (Applied Biosystems, Foster City,CA) terminator cycle sequencing method. The presence of di-, tri-, and tetranucleotide repeats and short tandem repeats, which is widespread in the genome, poses a daunting task in sequencing laboratories, where a variety of DNA templates are submitted for sequencing.These base anomalies arise mainly as a result of the formation of secondary structures, including hairpins, and intramolecular base pairing between guanine and cytosine bases on the template strand. A common approach to the optimization of such sequencing reactions is either to replace the guanine with a base analog (such as deoxyinosine 5'-triphosphate [dITP] or 7-deaza-deoxyguanosine 5'-triphosphate [dGTP]) or to add a denaturant (such as dimethylsulfoxide [DMSO]) to the reaction mixture to overcome the undesired sequencing artifacts. Additives sometimes are ineffective for sequencing templates with GC-rich regions and repeat sequences. Herein we describe the effectiveness of (carboxymethyl)trimethylammonium (betaine) inner salt as an additive in the reaction mixture for reducing band compressions. The results presented show that betaine outperformed DMSO in sequencing through the localized regions containing GC-rich base pairs, guanine stretches, or TGC-type repeats in several DNA templates.

Immunization with TCR Vbeta10 peptide reduces the frequency of type-II collagen-specific Th1 type T cells in BUB/BnJ (H-2q) mice.

OBJECTIVE: Collagen induced arthritis (CIA) in mice is mediated by synergistic T cell and humoral immune responses specific for type II collagen (CII). We have previously shown that in arthritic joints of BUB mice (TCR Vbetaa, H-2q) the TCR repertoire is enrichedfor Vbeta10 expressing T cells, and that immunization with a Vbeta10 peptide (Vbeta10p) prevents the phenotypic expression of disease. The objective of the present study was to understand how immunization with a synthetic TCR Vbeta peptide affected the development of the pathogenic CII-specific immune response in BUB mice. METHODS: Arthritic and protected animals were tested for Vbeta10p- and CII-specific cytokine production by a highly specific and sensitive ELISA spot assay, andfor CII-specific antibody production by standard ELISA. In adoptive transfer experiments, Vbeta10p-specific LN cells (INF-gamma producing) were injected into naive mice prior to immunization with type-II collagen/CFA. RESULTS: Immune cells from arthritic animals produced IFN-gamma and IL-2, without IL-4 and IL-5 in response to CII and an immunodominant epitope, A2, derivedfrom CII. Serum from these mice contained anti-CII antibodies of both IgGI and IgG2a subtypes. Our results show for thefirst time that immunization with Vbeta10p resulted in Vbeta10p-specific IFN-gamma and IL-2 production that was restricted to the CD4+ T cell subset. Emergence of this Vbeta10p-specific immune response was associated with a dramatic decrease in the frequency of CII and A2-specific, cytokine producing T cells in arthritis protected mice. Protective immunity was cell mediated and could be adoptively transferred. In contrast, the protective immunization had only a marginal effect on the anti-CII antibody response indicating that the CII specific humoral immune response was not significantly affected. CONCLUSION: Immunization with TCR Vbeta10p leads to expansion of a population of Vbeta10p- specific CD4+ Tcells. This anti-TCR Vbeta10p specific type 1 cytokine producing immune response was protective in adoptive transfer studies and appears to inhibit the expansion of the pathogenic anti-CII cellular immunity. Additionally, the anti-TCR Vbeta10p-specific cellular immune response was mediated by CD4+ T cells and these T cells did not produce IL-4 or IL-5. Thus, our results suggest that protection against CIA in mice immunized with synthetic TCR Vbeta10p was achieved by a specific down-regulation of the CII-specific Thl type cellular immune response and not via immune deviation.

Expression profile of protein tyrosine kinase genes in human osteoarthritis chondrocytes.

OBJECTIVE: To determine the expression profile of protein kinase (PK) and protein tyrosine kinase (PTK) genes in human primary osteoarthritis (OA) chondrocytes and to compare it with that of immortalized human chondrocytes T/C 28a4 with a view to learning whether T/C 28a4 cells can be used for elucidating signal transduction pathways in human chondrocytes. DESIGN: We used the Atlas Human cDNA Array and a method based on PCR with degenerate primers to analyse the expression profile of protein kinase genes in primary human OA chondrocytes and compared it with that of immortalized human chondrocyte cell line T/C 28a4 using RT-PCR and Western blotting. RESULTS: A total of 21 PTK genes were identified and several of these have never been shown to be expressed in human OA chondrocytes. Comparative expression analysis of some selected kinase genes showed that the mRNA expression pattern of many protein kinase genes in OA chondrocytes was identical to that of T/C 28a4 cells. However, there were differences in the level of protein expression of selected protein kinases in these cells. For example, mRNA expression of the novel kinase HCK was detected in OA chondrocytes and in the cell lines analysed but by Western blotting HCK protein was not detected in OA chondrocytes. In these studies, we also identified a novel mutant form of the discoidin domain receptor 2 (DDR2) transcript from chondrocyte-like cell line HTB-94. CONCLUSIONS: Our results provide novel information about protein kinase gene expression in OA chondrocytes and indicate that the transformed chondrocyte cell line T/C 28a4 may be suitable for elucidating signal transduction pathways in chondrocytes and to investigate how they regulate chondrocyte function in inflammatory and degenerative joint diseases.

Involvement of caspase-3 in epigallocatechin-3-gallate-mediated apoptosis of human chondrosarcoma cells.

Green tea polyphenol-(-)epigallocatechin-3-gallate (EGCG)-is a potent chemopreventive agent in many test systems and has been shown to inhibit tumor promotion and induce apoptosis. In this study we describe a novel observation that EGCG displayed strong inhibitory effects on the proliferation and viability of HTB-94 human chondrosarcoma cells in a dose-dependent manner and induced apoptosis. Investigation of the mechanism of EGCG-induced apoptosis revealed that treatment with EGCG resulted in DNA fragmentation, induction of caspase-3/CPP32 activity, and cleavage of the death substrate poly(ADP-ribose)polymerase (PARP). Pretreatment of cells with a synthetic pan-caspase inhibitor (Z-VAD-FMK) and a caspase-3-specific inhibitor (DEVD-CHO) prevented EGCG-induced PARP cleavage. The induction of apoptosis by EGCG via activation of caspase-3/CPP32-like proteases may provide a mechanistic explanation for its antitumor effects.

Tumour necrosis factor alpha enhances the expression of hydroxyl lyase, cytoplasmic antiproteinase-2 and a dual specificity kinase TTK in human chondrocyte-like cells.

Tumour necrosis factor alpha (TNF-alpha) is a cytokine with pleiotropic effects on cells ranging from proliferation to apoptosis. These biological effects of TNF-alpha are believed to be elicited by the induction or enhancement of the expression of TNF-alpha responsive genes in the target cells. TNF-alpha is pro-inflammatory and a principal mediator in the pathogenesis of arthritis. The activation of an inflammatory cascade by TNF-alpha in arthritis results in the degradation of cartilage, joint destruction and loss of function. Because TNF-alpha is an important mediator in the pathogenesis of arthritis, the present study addresses the identification of novel TNF-alpha responsive genes in HTB-94 cell line which is of human origin and maintains a chondrocytic phenotype. The three identified cDNAs were previously not known to be induced or upregulated by TNF-alpha in chondrocytes or cells of chondrocytic lineage. One of the identified cDNAs had sequence similarity to human hydroxyl lyase mRNA (PLOD), an enzyme involved in collagen biosynthesis and its metabolism; the second cDNA had sequence similarity to the human cytoplasmic anti-proteinase-2 mRNA (CAP-2), a member of a group of proteins shown to be associated with protecting cells from TNF-alpha-induced apoptosis; and the third cDNA had sequence similarity to a dual specificity kinase, TTK, which is associated with cell proliferation. Relative gene expression level analysis by PCR and by Northern blotting revealed that treatment with TNF-alpha enhanced the expression of PLOD, CAP2 and TTK transcripts which confirmed the results obtained with display gels. Furthermore, TTK mRNA expression was also induced in human articular chondrocytes treated with TNF-alpha but not in untreated chondrocytes. Our results suggest that these genes may play a role in chondrocytic responses to TNF-alpha-mediated stimuli affecting the cartilage homeostasis.

Sequencing telomeric DNA template with short tandem repeats using dye terminator cycle sequencing.

The standard DNA sequencing methods for use in conjunction with commercially available sequencing kits are effective in sequencing a majority of templates. However, templates rich in dinucleotide and tetranucleotide repeats and a telomeric DNA containing tandem repeats are difficult to sequence adequately using these methods. Base compression artifacts due to formation of secondary structure on the nascent strands and slippage of the DNA polymerase accompanied by premature chain termination in homopolymer and short tandem repeat regions of DNA are commonly encountered problems in sequencing core laboratories. In an attempt to sequence such repeat regions of telomeric DNA templates using dye terminator chemistry, we investigated the effect of increasing the annealing time and temperature in combination with the use of denaturing conditions. Specifically, we compared the commonly used ABI PRISM BigDye, dGTP BigDye, and DYEnamic ET terminator chemistries for sequencing telomeric DNA templates rich in CA- and AACCCC-type repeats and for sequencing a template rich in dinucleotide (GT and CT) and tetranucleotide repeats. The routine reaction protocol was modified by adding either 1 M 1-carboxy-N,N,N-trimethylmethanaminium inner salt (betaine) or 5% dimethyl sulfoxide (DMSO) as denaturants in the reaction mixture. In addition, the annealing and denaturation times were increased to allow successful primer extension for linear growth of sequencing reaction product. Many of the artifacts in sequencing are known to be due to reduced stability of the hybrid formed between the template and the nascent strand. The effects of using denaturants to break secondary structures in the nascent chain and of increasing the denaturation and annealing times are discussed.We were able to sequence DNA templates with tandem repeats that failed to sequence under routine reaction conditions.

Prevention of collagen-induced arthritis in mice by a polyphenolic fraction from green tea.

Identification of common dietary substances capable of affording protection or modulating the onset and severity of arthritis may have important human health implications. An antioxidant-rich polyphenolic fraction isolated from green tea (green tea polyphenols, GTPs) has been shown to possess anti-inflammatory and anticarcinogenic properties in experimental animals. In this study we determined the effect of oral consumption of GTP on collagen-induced arthritis in mice. In three independent experiments mice given GTP in water exhibited significantly reduced incidence of arthritis (33% to 50%) as compared with mice not given GTP in water (84% to 100%). The arthritis index also was significantly lower in GTP-fed animals. Western blot analysis showed a marked reduction in the expression of inflammatory mediators such as cyclooxygenase 2, IFN-gamma, and tumor necrosis factor alpha in arthritic joints of GTP-fed mice. Histologic and immunohistochemical analysis of the arthritic joints in GTP-fed mice demonstrated only marginal joint infiltration by IFN-gamma and tumor necrosis factor alpha-producing cells as opposed to massive cellular infiltration and fully developed pannus in arthritic joints of non-GTP-fed mice. The neutral endopeptidase activity was approximately 7-fold higher in arthritic joints of non-GTP-fed mice in comparison to nonarthritic joints of unimmunized mice whereas it was only 2-fold higher in the arthritic joints of GTP-fed mice. Additionally, total IgG and type II collagen-specific IgG levels were lower in serum and arthritic joints of GTP-fed mice. Taken together our studies suggest that a polyphenolic fraction from green tea that is rich in antioxidants may be useful in the prevention of onset and severity of arthritis.

Involvement of interleukin-1beta-converting enzyme in apoptosis of irradiated retinoblastomas.

PURPOSE: To investigate whether interleukin-1beta-converting enzyme (ICE), a mammalian homologue of the Caenorhabditis elegans cell death gene ced-3, is involved in gamma-irradiation-induced apoptosis (programmed cell death) of human retinoblastoma cells. METHODS: The induction of apoptotic cell death in human retinoblastoma cell lines WERI-Rb-1 and Y79 by gamma-irradiation was determined with a modified 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide colorimetric assay and the DNA-binding fluorochrome bis (benzimide) trihydro-chloride (Hoechst 33258) staining. The change of ICE protein level in tumor cells during apoptosis was determined by immunoblotting assay. Whether the specific tetrapeptide ICE inhibitor Ac-YVAD-CMK affected gamma-irradiation-induced apoptosis in tumor cells was also examined. The effect of ICE overexpression on tumor cells was evaluated by a transient transfection assay using ICE expression vector. RESULTS: Gamma-irradiation inhibited the cell viability of WERI-Rb-1 and Y79 cells in a dose-dependent manner and induced apoptosis. The protein level of ICE was remarkably enhanced after the treatment. The apoptotic cell death induced by gamma-irradiation was suppressed by the tetrapeptide ICE inhibitor Ac-YVAD-CMK. Moreover, overexpression of ICE induced apoptosis in tumor cells. CONCLUSIONS: These findings suggest that ICE may play an important role in gamma-irradiation-induced apoptosis in retinoblastoma cells. Transfer of the ICE gene induces apoptosis in these cells without gamma-irradiation.

FADD gene therapy for malignant gliomas in vitro and in vivo.

Fas/APO-1 (CD95), a cell surface cytokine receptor, triggers apoptotic cell death by specific agonist antibody, suggesting that Fas/APO-1 may be a promising target for treatment of tumors. In this study, we show that treatment with anti-Fas antibody effectively induced apoptosis in malignant glioma cell lines with high expression of Fas/APO-1 (n = 3). Malignant glioma cells with low or undetectable expression of Fas/APO-1 (n = 6), however, were resistant to Fas/APO-1-dependent cytotoxicity. The purpose of this study, therefore, was to determine whether resistant tumors could be made susceptible to apoptosis. FADD/MORT1 constitutes a novel protein that associates specifically with the cytoplasmic death domain of Fas/APO-1 and induces apoptosis. We investigated whether overexpression of FADD would induce apoptosis in malignant glioma cells without activating Fas/APO-1. Results indicated that about 85% of malignant glioma cells, regardless of Fas/APO-1 expression levels, underwent apoptosis after transient transfection with FADD expression vector. To further improve gene transfer of FADD into malignant glioma cells, we constructed a retroviral vector containing the FADD gene. The retroviral transfer of FADD gene significantly enhanced the transduction efficiency and effectively inhibited both in vitro and in vivo survival of malignant glioma cells through induction of apoptosis. These findings suggest that the FADD gene is a novel and useful tool for the treatment of malignant gliomas.

Antisense telomerase treatment: induction of two distinct pathways, apoptosis and differentiation.

Telomerase, the enzyme that elongates telomeric DNA (TTAGGG)n, may be involved in cellular immortality and oncogenesis. To investigate the effect of inhibition of telomerase on tumor cells, we transfected the antisense vector against the human telomerase RNA into human malignant glioma cells exhibiting telomerase activity. After 30 doublings, some subpopulations of transfectants expressed a high level of interleukin-1beta-converting enzyme (ICE) protein and underwent apoptosis. In contrast, other subpopulations also showed enhanced ICE protein but escaped from apoptotic crisis and continued to grow, although their DNA synthesis, invasive ability, and tumorigenicity in nude mice were significantly reduced. Surviving cells demonstrated increased expression of glial fibrillary acidic protein and decreased motility, consistent with a more differentiated state. These cells also contained enhanced expression of the cyclin-dependent kinase inhibitors (CDKIs) p21 and p27. Treatment of surviving nonapoptotic cells with antisense oligonucleotides against p27, but not p21, induced apoptotic cell death, suggesting that p27 may have protected differentiating glioma cells from apoptosis. These data show that treatment with antisense telomerase inhibits telomerase activity and subsequently induces either apoptosis or differentiation. Regulation of these two distinct pathways may be dependent on the expression of ICE or CDKIs.

Inhibition of telomerase increases the susceptibility of human malignant glioblastoma cells to cisplatin-induced apoptosis.

Malignant glioblastomas grow very rapidly and are generally resistant to either DNA-damaging drugs or gamma-irradiation. If tumor cells could be made more susceptible to cell death with treatments, this would clearly represent a significant improvement in the success of treatment. Recently, telomerase has become a focus of interest among oncologists as a target for treating cancer cells. Telomerase elongates telomeric DNA repeats (TTAGGG)n and is important in protecting and replicating DNA. The vast majority of tumor cells, indeed, express telomerase activity whereas normal somatic cells, except for a few cells, do not. Since telomerase is essential for protecting DNA, we may be able to make tumors more sensitive to treatments with DNA-damaging drugs by inhibiting telomerase activity. In this study, we used cis-diamminedichloroplatinum (cisplatin)-sensitive U87-MG cells and cisplatin-resistant U251-MG of human malignant glioblastoma cell lines. U87-MG cells did not express telomerase activity, whereas telomerase was highly detected in U251-MG cells. Interestingly, inhibition of telomerase with an antisense telomerase expression vector not only decreased telomerase activity but also increased susceptibility to cisplatin-induced apoptotic cell death in U251-MG cells. These findings suggest that treatment with antisense telomerase may represent a new chemosensitisation for tumors resistant to anticancer drugs.

Antagonist effect of insulin-like growth factor I on protein kinase inhibitor-mediated apoptosis in human glioblastoma cells in association with bcl-2 and bcl-xL.

OBJECT: Tamoxifen (TAM) has been found to be effective in inhibiting proliferation of glioblastoma cells in vitro, but clinical studies have been disappointing. The purpose of this study was to determine whether insulin-like growth factor I (IGF-I), a potential autocrine/paracrine mitogen produced by glioblastomas, interferes with the antimitogenic actions of TAM. METHODS: Human glioblastoma cells were treated with or without TAM and/or IGF-I in vitro and evaluated for: viability by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenol tetrazolium bromide cleavage assay; apoptosis by histochemical analysis of nuclear morphology and 3'-OH DNA fragments; and expression of the IGF-I receptor, and the bcl-2, bcl-xL, and bax proteins by immunoblot analysis. In addition, p53 status was determined by DNA sequencing and by transient transfection with luciferase reporter plasmids containing wild-type or mutant p53. Results indicated that after 72 hours of exposure to 2 mg/ml TAM in vitro, 56.3% of WITG3 and 43.8% of U87-MG glioblastoma cells contained apoptotic nuclei (p < 0.01 compared with untreated cells). Apoptosis was independent of the presence of p53 because the WITG3 cells, in contrast to the U87-MG cells, expressed a mutant, nonfunctional p53. The WITG3 cells expressed IGF-I receptor proteins and demonstrated IGF-I binding. Exogenous IGF-I stimulated WITG3 cell proliferation and significantly (p < 0.05) antagonized the cytotoxic effects of TAM in a dose-dependent fashion; IGF-I, but not TAM, enhanced expression of bcl-2 and bcl-xL proteins; however, bax protein expression was unchanged by either treatment. CONCLUSIONS: Because many gliomas secrete large amounts of IGF-I in autocrine/paracrine growth pathways, these data may, in part, explain the failure of TAM to achieve clinical results as dramatic as those in vitro.

T cells reactive to a single immunodominant self-restricted allopeptide induce skin graft rejection in mice.

Alloreactive T lymphocytes can respond to foreign MHC complexed with foreign peptides through the direct pathway of allorecognition and can additionally recognize allopeptides expressed in the context of recipient (self) MHC through the indirect pathway. To better elucidate how indirect pathway-responsive CD4(+) T cells mediate allograft rejection, we isolated and characterized a TH1 T cell line from BALB/c recipients of B10.A skin that responds to a defined immunodominant, self-restricted allopeptide, I-Abetak58-71. When transferred into BALB/c severe combined immunodeficiency recipients of B10.A skin allografts, this cell line specifically induced a form of skin graft rejection characterized by the presence of TH1 cytokines, macrophage infiltration, and extensive fibrosis. Recall immune responses and immunofluorescence of the rejecting skin revealed only the presence of the peptide-specific T cells within the recipient animals, with no evidence of a direct pathway alloresponse. These studies demonstrate that T cells reactive to a single self-restricted allopeptide can mediate a form of allogeneic skin graft rejection that exhibits characteristics of a chronic, fibrosing process.

Retroviral transfer of CPP32beta gene into malignant gliomas in vitro and in vivo.

Malignant gliomas are highly aggressive neoplasms that are very resistant to current therapeutic approaches, including irradiation, chemotherapy, and immunotherapy. To improve the prognosis, it is absolutely essential to explore novel modalities of treatment. Recently, we have demonstrated that interleukin 1beta-converting enzyme (ICE), a mammalian homologue of the Caenorhabditis elegans cell death gene ced-3, induces apoptotic cell death in malignant glioma cells. To date, ICE and ICE-like proteases (the ICE family), such as Ich-1L, CPP32beta, Mch2alpha, and Mch3alpha, have been shown to mediate apoptosis in some cells. The purpose of this study is to determine whether the ICE gene family functions as a useful tool for the treatment of malignant glioma cells through induction of apoptosis. The transient transfection assays showed that CPP32beta and Mch2alpha genes induced apoptotic cell death in malignant glioma cells more effectively than did the ICE, Ich-1L, and Mch3alpha genes. To improve the efficiency of gene transfer into malignant glioma cells, we constructed the retroviral vectors containing the ICE gene family. The retroviral transfer of CPP32beta or Mch2alpha gene effectively induced apoptosis in malignant glioma cells in vitro. Furthermore, treatment of tumors grown in mice with retrovirus containing CPP32beta significantly inhibited growth of the tumors through induction of apoptosis. The retroviral transfer of CPP32beta or Mch2alpha, therefore, may be a novel and promising approach for the treatment of malignant glioma, an invariably fatal tumor.