Radiation-induced apoptosis in human sarcoma and glioma cell lines

Six human soft-tissue sarcoma and 14 glioma cell lines, exhibiting considerable differences in radioresponsiveness and histological grade of differentiation of the parental tumour, were examined with respect to apoptosis development after irradiation with ⁶⁰Co γ-rays. After test doses of 6 and 25 Gy, significant changes characteristic of apoptosis occurring within 6 to 30 hr were exhibited by only 2 differentiated sarcoma cell lines, EL7 and ESS2. The characteristic intemucleosomal fragmentation of DNA was detected as early as 6 hr after exposure of subconfluent monolayer cultures to 6 Gy. It was limited to cells that had detached from the culture plate, whereas adherent cells showed random degradation of DNA, namely after higher doses (25Gy) or longer incubation times (30 hr). As assessed by fluorescence microscopy of unfixed cultures stained with Hoechst 33342 and propidium iodide, the proportion of cells showing apoptotic bodies in non-irradiated controls was < 0.l% and 0.3% for EL7 and ESS2, respectively. The doseresponse relationship for apoptosis was determined at 9 hr post-irradiation. After 2 Gy, the percentage of apoptotic cells was elevated to 3.4% in EL7 and 4.5% in ESS2 cultures. Saturation was obtained above 6 Gy, with 8.4% apoptosis in EL7 and 15% in ESS2 after 25 Gy. Taken together, rapid ionizing-radiation-induced apoptosis seems to be limited to a subgroup of sarcomas and is unlikely to occur in gliomas. © 1995 Wiley-Liss Inc.     

榄香烯诱导神经胶质瘤细胞凋亡作用的剂量和时间依赖性研究

神经胶质瘤是目前最顽固的恶性肿瘤之一,我们应用榄香烯治疗胶质瘤取得了较为显著的疗效。在临床应用中,我们发现榄香烯的治疗效果与使用途径和用药剂量有很大关系。前期体外研究已经证实,榄香烯能抑制胶质瘤细胞的恶性增殖,并诱导凋亡。我们采用流式细胞分析方法,进一步探讨榄香烯诱导凋亡与药物浓度和作用时间的关系。     

Epigenetic silencing of PEG3 gene expression in human glioma cell lines

Genomic imprinting, the phenomenon in which alleles of genes are expressed differentially depending on their parental origins, has important consequences for mammalian development, and disturbance of normal imprinting leads to abnormal embryogenesis and some inherited diseases and is also associated with various cancers. In the context of screening for novel imprinted genes on human chromosome 19q13.4 with mouse A9 hybrids, we identified a maternal allele-specific methylated CpG island in exon 1 of paternally expressed imprinted gene 3 (PEG3), a gene that exhibits paternal allele-specific expression. Because PEG3 expression is downregulated in some gliomas and glioma cell lines, despite high-level expression in normal brain tissues, we investigated whether the loss of PEG3 expression is related to epigenetic modifications involving DNA methylation. We found monoallelic expression of PEG3 in all normal brain tissues examined and five of nine glioma cell lines that had both unmethylated and methylated alleles; the remaining four glioma cell lines exhibited gain of imprinting with hypermethylated alleles. In addition, treatment of glioma cell lines with the DNA demethylating agent 5-aza-2'-deoxycytidine reversed the silencing of PEG3 biallelically. In this article, we report that the epigenetic silencing of PEG3 expression in glioma cell lines depends on aberrant DNA methylation of an exonic CpG island, suggesting that PEG3 contributes to glioma carcinogenesis in certain cases.     

Oncostatin M signaling in human glioma cell lines

We have recently found that oncostatin M (OSM) is overexpressed in most human brain tumors. The effects of OSM are unclear with conflicting reports of growth stimulatory or inhibitory effects in various cell types. The aim of this study was to investigate the effects of OSM in 5 glioma cell lines and 7 short-term cultures of human gliomas and in normal cultured human astrocytes. None of the cell lines and short-term cultured tumor cells expressed OSM in vitro. OSM signals through a gp130 containing receptor complex over the JAK/STAT pathway. Immunofluorescence and RT-PCR analysis showed that the tumor cells express gp130 and the other receptor components, LIFRbeta and OSMRbeta. OSM treatment induced phosphorylation of STAT3 and STAT1 indicating presence of a functional JAK/STAT pathway. No OSM effect on proliferation was observed. OSM gave no protective effects against tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-induced cytotoxicity.     

Antitumor activity and apoptosis induction in human cancer cell lines by Dionysia termeana

Studies have demonstrated that plant extracts possess various biological effects including antitumor activity. In the present study, the antitumor activity of Dionysia termeana, a plant native to Iran, was investigated. Cytotoxic activity of the extract on tumor cell lines using MTT colorimetric assay was determined. Cell cycle analysis by flow cytometry and DNA fragmentation analysis on sensitive cell lines was then carried out. Results obtained indicated that the highest activity of D. termeana was against K562 leukemia cell line with IC50 less than 20 μ g/mL. Fifty-five percent inhibition of Jurkat cells due to exposure to D. termeana was found at 200 μ g/mL of the extract. A549, a lung carcinoma cell, and Fen bladder carcinoma cell line were less affected. In flow cytometry analysis, D. termeana induced apoptosis in the K562 and Jurkat cells. In DNA fragmentation analysis the extract produced ladder formation in both cells. In conclusion, these results indicated that the extract used in this study have antitumor activity through induction of apoptosis particularly in the leukemia cell lines.     

Gli1 inhibition induces cell-cycle arrest and enhanced apoptosis in brain glioma cell lines

The Hedgehog (HH)-Gli1 signaling pathway plays an important role in the patterning and development of the central nervous system during embryogenesis. Recent data have shown its possible involvement in a subset of human gliomas, and inhibition of the pathway resulted in tumor suppression in both in vitro and in vivo studies. The underlying mechanisms of tumor suppression, however, remain to be fully elucidated. Here, we investigated Gli1 expression in 65 surgically resected malignant glioma tissues and found the Ki-67 labeling index to be higher in Gli1-positive gliomas than in Gli1-negative gliomas. Depletion of Gli1 expression by small interfering RNA (siRNA) interference led to remarkably decreased cell proliferation and enhanced apoptosis in U87 glioma cell line. To explore the molecular mechanisms of the phenotypic changes, we performed real-time quantitative RT-PCR analysis to monitor the changes of a series of genes which play critical roles in the regulation of cell cycle and apoptosis. The result showed that downregulation of G₁ cyclins, downregulation of Bcl-2, and upregulation of p21 were detected after Gli1 downregulation. Additionally, cyclopamine was used to inhibit the HH signaling activity as an indirect approach to decrease Gli1 expression, and we observed that cyclopamine exclusively inhibited cell growth in HH-pathway-active glioma cell lines. The cell phenotypic and molecular changes induced by cyclopamine were consistent with those caused by siGli1 interference. In conclusion, our findings support an important role of Gli1 in cell-cycle and apoptosis regulation in human brain gliomas; hence, it can serve as a potential target of new therapeutic strategies for these diseases.     

Etoposide sensitivity of radioresistant human glioma cell lines

Purpose: Malignant gliomas display aggressive local behavior and are not cured by existing therapy. Etoposide, a topoisomerase-II-inhibitor agent, is one of the most active and useful antineoplastic agents. However, etoposide is not usually used on these tumors. We undertook an in vitro study to prove that etoposide is a useful drug for malignant gliomas. Methods: Five human glioma cell lines were the basis for this study. Following exposure to various concentrations of etoposide, the glioma cell lines were found to be sensitive; the median concentration inhibiting the number of cells by 50% (IC₅₀) was 8.76 μg/ml (range 8–15.8 μg/ml). Since topoisomerase II is the critical target for etoposide, it was of interest to determine the topoisomerase II activity (decatenation of kinetoplast DNA isolated from Cryphtidia fasciculata) and the etoposide-induced inhibition of topoisomerase II activity. Results: The topoisomerase II activity was homogeneous in glioma cell lines (average of 50% decatenation with 7,000 cells), and topoisomerase II was the target of the etoposide. Conclusions: Our results suggest that topoiomerase II-reactive agents may prove to be clinically useful drugs for patients with malignant gliomas. Received: 4 March 1997 / Accepted: 1 June 1997     

Inhibition of growth and induction of apoptosis in human cancer cell lines by tea polyphenols

In order to study the biological activities of tea preparations and purified tea polyphenols, their growth inhibitory effects were investigated using four human cancer cell lines. Growth inhibition was measured by [3H]thymidine incorporation after 48 h of treatment. The green tea catechins (-)-epigallocatechin-3-gallate (EGCG) and (-)- epigallocatechin (EGC) displayed strong growth inhibitory effects against lung tumor cell lines H661 and H1299, with estimated IC50 values of 22 microM, but were less effective against lung cancer cell line H441 and colon cancer cell line HT-29 with IC50 values 2- to 3- fold higher. (-)-Epicatechin-3-gallate, had lower activities, and (-)- epicatechin was even less effective. Preparations of green tea polyphenols and theaflavins had higher activities than extracts of green tea and decaffeinated green tea. The results suggest that the growth inhibitory activity of tea extracts is caused by the activities of different tea polyphenols. Exposure of H661 cells to 30 microM EGCG, EGC or theaflavins for 24 h led to the induction of apoptosis as determined by an annexin V apoptosis assay, showing apoptosis indices of 23, 26 and 8%, respectively; with 100 microM of these compounds, the apoptosis indices were 82, 76 and 78%, respectively. Incubation of H661 cells with EGCG also induced a dose-dependent formation of H2O2. Addition of H2O2 to H661 cells caused apoptosis in a manner similar to that caused by EGCG. The EGCG-induced apoptosis in H661 cells was completely inhibited by exogenously added catalase (50 units/ml). These results suggest that tea polyphenol-induced production of H2O2 may mediate apoptosis and that this may contribute to the growth inhibitory activities of tea polyphenols in vitro.      

Lovastatin-induced apoptosis in human melanoma cell lines

The cholesterol-lowering medications, statins, inhibit cellular proliferation and induce apoptosis in an array of cancer cell lines, including melanoma. We investigated the apoptotic mechanism of lovastatin on human melanoma cell lines in vitro. The cytotoxicity of statins on multiple cell lines was examined by Cell Titer 96 Aqueous One solution cell proliferation assay (MTS assay). Apoptosis was assayed by ethidium bromide and acridine orange morphologic assays, an Annexin V apoptosis detection kit and active caspase 3 assays. Farnesyl pyrophosphate and geranylgeranyl pyrophosphate add-back experiments were performed to better define the molecular mechanisms mediating lovastatin cytotoxicity. Lovastatin caused cytotoxicity in human and murine melanoma cells, but did not induce toxicity in an epidermoid carcinoma cell line A431. For human melanoma cells, lovastatin precipitated cell rounding, increased the percentage of apoptotic cells detected by ethidium bromide and acridine orange staining and by the Annexin V apoptosis detection kit, and resulted in a 50-fold increase in active caspase 3, corroborating that lovastatin induced apoptosis. Adding back geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate, reversed the effects of lovastatin in A375 cells. Of the five statins tested, pravastatin was least effective in killing melanoma cells. Lovastatin induced caspase-dependent apoptosis in multiple melanoma cell lines via a geranylation-specific mechanism. This study supports a possible role of lovastatin as a therapeutic, adjuvant or chemopreventive agent for melanoma.     

吲哚美辛对结肠癌细胞中细胞周期蛋白的影响

目的体外观察吲哚美辛对含突变型p53的SW480细胞及经野生型p53转染的结肠癌细胞株SW480(wtp53/SW480)的影响,探讨吲哚美辛抗结肠癌作用的分子机制.方法不同浓度的吲哚美辛作用于细胞株,采用Western斑点免疫印迹方法,分别检测SW480细胞及wtp53/SW480细胞中CDK2、CDK4和p21WAF1/PIC1蛋白的表达水平.结果吲哚美辛作用于wtp53/SW480细胞24 h后,其CDK2、CDK4蛋白表达水平随吲哚美辛浓度的增加而逐渐下调,呈浓度依赖性,以600μmol/L时抑制作用最强;而p21WAF1/PIC1蛋白表达水平上调,其表达水平随着一定范围内吲哚美辛浓度的增加而逐渐上调,以400μmol/L吲哚美辛时作用最强,600μmol/L时回到基础水平.在未经转染的SW480细胞中CDK2、CDK4和p21WAF1/PIC1蛋白表达没有发生明显改变.结论吲哚美辛抗结肠癌作用部分分子机制可能是通过下调CDK2、CDK4蛋白的表达和上调p21WAF1/PIC1蛋白来实现且存在p53-p21WAF1/CIP1依赖途径.     

Canthaxanthin induces apoptosis in human cancer cell lines

To investigate the possibility that canthaxanthin inhibits cancer cell growth by inducing apoptosis, human WiDr colon adenocarcinoma and SK- MEL-2 melanoma cells were treated with two different doses of the carotenoid for 48 h. Canthaxanthin was incorporated and/or associated to cells. The treatment with the carotenoid caused growth inhibition in both cell types. Concomitantly, apoptosis was induced. Increasing time of exposure and carotenoid concentration, this effect was more pronounced. At 48 h, the percentages of apoptotic cells were 13 and 15, using 1 microM canthaxanthin, and 18 and 20, using 10 microM canthaxanthin in WiDr and SK-MEL-2 cells, respectively. This study represents the first demonstration that canthaxanthin is able to induce apoptosis in tumour cells.      

Inhibition of cell growth and induction of apoptosis in human prostate cancer cell lines by 6-aminoquinolone WM13

Fluoroquinolones affect the proliferation and apoptotic cell death of several human malignancies. Therefore, we investigated whether new 6-aminoquinolone derivatives, initially synthesized as anti-HIV agents, could affect the proliferation and apoptotic cell death of human prostate cancer cell lines. PC3 and LNCaP cell lines were used as models of androgen-resistant and androgen-responsive prostate cancer, and proliferation of PC3 and LNCaP cells was strongly inhibited by 6-aminoquinolone WM13. Cytotoxicity, which was more pronounced in LNCaP, was accompanied by morphological changes, DNA damage, arrest at the S/G(2)/M phase of the cell cycle, and an increase of the sub-G(1) population. Molecular mechanism underlying WM13-induced cell death involved caspase-8 and -3 and modulation of the expression of apoptotic genes, as well as cleavage of poly-ADP ribose polymerase. Cell death following the treatment of human prostate cancer cell lines with WM13 can be attributed to apoptosis which, depending on the cell line, proceeds through different pathways.     

TGF-β1对人肝癌细胞系凋亡的调控作用研究

目的肝细胞对TGF-β1敏感性的丧失据认为是肝癌重要的致病因素之一。本研究旨在明确人肝肿瘤细胞系中TGF-β1的作用及其与凋亡的关系。方法选用三种含不同p53基因状态的人肝肿瘤细胞系,应用脱氧核糖核苷酸末瑞转移酶介导的dUTP缺口末端标记技术(TUNEL)对TGF-β1诱导的肝肿瘤细胞的凋亡进行定量检测。结果在应用TUNEL检测三个细胞系中,TGF-β1仅能诱导Hep3B细胞(缺失p53)则凋亡较少。这提示凋亡p53基因的表达具有明确的联系。结论HepG2细胞系比Huh-7和Hep3B系细胞更易发生TGF-β1诱导的凋亡,TGF-β1通过p53依赖性途径诱导肝癌细胞系发生凋亡。     

Cytotoxicity of human prostate cancer cell lines in vitro and induction of apoptosis using 213Bi-Herceptin alpha-conjugate

HER-2 has been implicated in the oncogenesis of human prostate cancer (CaP) and is the target of a new treatment for metastatic breast cancer using the humanised monoclonal antibody (MAb) trastuzumab (Herceptin). In this study, a novel alpha-particle emitting [213Bi]Herceptin construct, which targets the HER-2 extracellular domain on CaP cells, was prepared and evaluated in vitro. We used immunocytochemistry, flow cytometry and Western blot analysis to examine the expression of HER-2 in a panel of established human CaP cell lines, used the MTS assay to evaluate the cytotoxicity of 213Bi-Herceptin on these cell lines and the TUNEL assay to document apoptosis. The results indicate that LNCaP-LN3 cells express high levels of HER-2 protein, in contrast, DU 145 cells express low to medium levels, and PC-3 cells express an undetectable level of HER-2 protein. 213Bi-Herceptin was specifically cytotoxic to LNCaP-LN3 cells in a concentration-dependent fashion, cause the cells to undergo apoptosis, whereas DU 145 showed an HER-2 level-dependent response to 213Bi-Herceptin cytotoxicity. In contrast, PC-3 cells were resistant to 213Bi-Herceptin-induced cytotoxicity. The 213Bi-Herceptin induced apoptosis in LNCaP-LN3 cells could be inhibited by incubation with unlabeled Herceptin. Our results suggest that 213Bi-Herceptin alpha-conjugate might be a promising new agent for the treatment of preangiogenic cancer cell clusters or micro-metastases with high levels of HER-2 expression.     

Heterogeneity of the induction of HLA-DR expression by human immune interferon on glioma cell lines and their clones

The modulation of HLA-DR and HLA-A, -B, and -C by human recombinant immune interferon (IFN-gamma) was studied on 10 malignant glioma cell lines established in our laboratory, on 8 clones or subclones derived from these lines, and on a fetal astrocyte cell line. Comparative studies were performed with recombinant leukocyte interferon (IFN-alpha). The results not only confirmed the selective activity of IFN-gamma on the modulation of HLA-DR expression, as opposed to that of IFN-alpha, but also demonstrated a marked heterogeneity in the response of glioma cell lines and their clones to the two types of IFN tested. For example, all 3 clones of an inducible cell line could be modulated to express HLA-DR, whereas only 2 of 5 clones derived from a noninducible line were modulated. This heterogeneity did not seem to be due to the absence of the receptor for IFN-gamma on the surface of these cells, since almost all of the cell lines or clones tested (17 of 19) responded to IFN-gamma by the induction or enhancement of the expression for either HLA-DR or HLA-A, -B, and -C (or both). The heterogeneity of induction was also demonstrated between clones derived from a glioma line that did not express HLA-DR after IFN-gamma treatment. The production of HLA-DR by one of the clones was abundant enough to be confirmed by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis.     

Apoptotic induction by BE16627B on human malignant glioma cell lines by an anti-matrix metalloproteinase agent

We have elucidated the pharmacological action of the anti-matrix metalloproteinase inhibitor BE16627B on glioma cells. The study was limited to the noncytotoxic dose range. The aim of the study was to investigate whether the cytotoxicity of BE16627B, an anti-MMP agent, is related to apoptosis in the human malignant glioma cell lines U87MG, U251MG, and U373MG. MTT assay was performed to detect the cytotoxic dose range. Agarose gel electrophoresis was performed with purified genomic DNA following exposure to 20 to 500 μM BE16627B for 24h, compared with 0 μM for the control group. Transmission electron microscopy (TEM) was employed to study nuclear fragmentation following exposure to 0, 20, and 500 μM of the agent for 24 h. An in situ endolabeling assay was performed to determine the index of apoptotic induction. MTT assay revealed that concentrations of 100 μM and above were cytotoxic. DNA laddering was demonstrated in agarose gel electrophoresis. TEM disclosed condensing and fragmentation of the chromatin. None of these changes were observed in the control group and the noncytotoxic dose group. The in situ endolabeling study disclosed that the apoptotic index was significantly elevated by cytotoxic doses of this agent (U373MG; control, 4.0%; 500 μM, 68.5%). These results indicated that cytotoxic concentrations of BE16627B induced apoptosis in human malignant glioma cell lines. In our previous report, this agent inhibited activity of MMP in noncytotoxic concentrations. Further study should be done to determine the pharmacological action of toxic BE16627B.     

Growth inhibition and synergistic induction of apoptosis by zoledronate and dexamethasone in human myeloma cell lines.

Bisphosphonates (BPs) are commonly used in the treatment of myeloma-associated osteolytic lesions. Recent reports have suggested that BPs may also exert direct antitumor effects on myeloma cells. Here, we show that the treatment of myeloma cell lines with the combination of the potent BP zoledronate and dexamethasone inhibits cell growth and synergistically induces apoptotic cell death, providing a rationale for potential applications in vivo.