人参皂甙单体Rh2对人脑胶质瘤细胞U251增殖和凋亡的影响及其机制探讨

目的观察人参皂甙单体Rh2（GS-Rh2）对人脑胶质瘤U251细胞增殖和凋亡的影响,并探讨其机制。方法用GS-Rh2处理人脑胶质瘤U251细胞,采用MTT法检测U251细胞增殖抑制率,流式细胞仪和Annexin V-FITC/PI双染法观察U251细胞凋亡情况,TRAP-ELISA法检测U251细胞端粒酶活性,RT-PCR法检测U251细胞人端粒酶逆转录酶（hTERT）mRNA的表达。结果 5、10、20、40、80μg/ml GS-Rh2组U251细胞增殖抑制率分别为20.42%、32.19%、45.09%、57.37%、73.82%。根据细胞增殖抑制曲线计算出IC30、IC50、IC70值分别为9.7、25.2、68.4μg/ml。FITC和PI荧光双参数点图显示实验组细胞分布区域与对照组相比出现明显改变,随着药物浓度的增加,早期凋亡、晚期凋亡或坏死的区域细胞数量逐渐增多。9.7、25.2、68.4μg/ml GS-Rh2处理12、24、48、72 h后U251细胞端粒酶活性随GS-Rh2浓度增加和作用时间的延长而降低。浓度为25.2μg/ml GS-Rh2作用24、48、72 h的U251细胞hTERTmRNA与β-actin灰度值比为0.964 9±0.004 2、0.401 8±0.001 4、0.297 8±0.001 8,对照组为0.976 4±0.005 1。作用48、72 h U251细胞hTERT mRNA与β-actin灰度值比与对照组相比P均〈0.05;作用48、72 h者相比P〈0.05。结论 GS-Rh2能够诱导人脑胶质瘤U25l细胞凋亡,抑制U25l细胞增殖。其机制与其抑制hTERT基因表达,降低端粒酶活性有关。     

表没食子儿茶素没食子酸酯抗消化道肿瘤作用的实验研究

背景：表没食子儿茶素没食子酸酯(EGCG)具有抗肿瘤作用，但是其有效浓度和可能作用机制尚不十分清楚。目的：研究EGCG对不同消化道肿瘤细胞株的杀伤作用及其抗肿瘤作用的靶位点，为其应用于临床肿瘤治疗奠定理论基础。方法：采用四唑蓝(MTT)比色法检测8株消化道肿瘤细胞株对EGCG敏感性的差异；采用流式细胞仪检测EGCG对敏感肿瘤细胞株细胞周期分布的影响；采用聚合酶链反应(PCR)-酶联免疫吸附测定(ELISA)检测EGCG对敏感肿瘤细胞株端粒酶活性的影响。结果：EGCG对8株消化道肿瘤细胞株均具有剂量依赖性杀伤作用。SW1116和MKN45细胞对EGCG最敏感，半数抑制浓度(IC50)分别为51．7μmol／L和55．9μmol／L；BGC823和SGC7901细胞次之，IC50分别为68．5μmol／L和79．1μmol／L；AGS细胞对低浓度EGCG不敏感，对高浓度EGCG敏感，IC50为83．8μmol／L；MKN28细胞对EGCG中等敏感，IC50为119．8μmol／L；HGC27和LoVo细胞对EGCG不敏感，IC50分别为183μmol／L和194．6μmol／L。3种不同浓度的EGCG作用48h后，敏感肿瘤细胞株MKN45的细胞周期分布与对照组相比均无明显改变。EGCG可抑制MKN45细胞的端粒酶活性，其作用呈剂量和时间依赖性。结论：EGCG对不同消化道肿瘤细胞株具有不同程度、呈剂量依赖性的杀伤作用；对敏感肿瘤细胞株MKN45的细胞周期分布无明显影响。EGCG的抗肿瘤作用可能与其抑制肿瘤细胞的端粒酶活性有关。     

抗纤灵对HepG2细胞端粒酶抑制作用的影响

[目的]观察抗纤灵对人肝癌细胞株（HepG2）端粒酶活性和端粒酶RNA的影响,探讨中药抗纤灵防止肝细胞癌变的作用机制。[方法]将10×半抑制浓度（IC50）,1.0×IC50,0.1×IC50抗纤灵药液加入到细胞培养液中,以0.85%氯化钠和环磷酰胺分别作阴性和阳性对照,在12、24、48、72、96 h收集细胞,并检测端粒酶的活性和端粒酶RNA的表达。[结果]抗纤灵杀伤HepG2的IC50为1 mg/ml,10×IC50为10 mg/ml,0.1×IC50为0.1 mg/ml;10×IC50浓度作用后,靶细胞端粒酶活性显示阴性,10×IC50及环磷酰胺对HepG2细胞端粒酶RNA有明显抑制作用;1.0×IC50和0.1×IC50则没有抑制作用。[结论]通过抑制端粒酶活性,抗纤灵能明显抑制HepG2生长。     

十全大补汤总多糖的体外抗肿瘤作用

目的探讨十全大补汤总多糖（以下简称总多糖）的体外抗肿瘤作用,为其临床应用及抗肿瘤药物的研发提供依据。方法以200、100、50μg/ml浓度总多糖干预体外培养的人肺癌A549细胞株、人肝癌Bel-7402细胞株、人结肠癌HCT-8细胞株和人宫颈癌Hela细胞株。作用24、48、72 h时采用MTT法测定细胞增殖抑制率（IR）。结果 200μg/ml总多糖作用48 h时A549细胞的IR最高;总多糖对另3种细胞的作用均为随浓度及作用时间延长IR逐渐升高,以200μg/ml、作用72 h时IR最高,呈剂量及时间依赖性。结论总多糖可在体外抑制肿瘤细胞生长;其有望作为抗肿瘤药物用于临床。     

南蛇藤乙酸乙酯提取物诱导HepG2细胞凋亡的实验研究

目的探讨南蛇藤乙酸乙酯提取物对HepG2细胞增殖和诱导凋亡的机制。方法采用CCK-8法检测细胞增殖;使用流式细胞仪检测细胞周期和细胞凋亡;采用分光光度计检测凋亡细胞胞浆caspase-3的活性变化。结果不同浓度的南蛇藤提取物能抑制HepG2细胞增殖,呈剂量效应和时间效应关系;药物作用24h时,其IC50为111.8μg/ml,作用48h时,其IC50为99.7μg/ml,作用72h时,其IC50为43.0μg/ml;药物干预24h时,HepG2细胞停滞在G0-G1期,并产生细胞凋亡亚二倍峰。在药物为15μg/ml、30μg/ml和60μg/ml时,细胞凋亡率分别为44.91%、31.95%和21.94%,与对照组比较,均有显著性差异（F=5.449,P〈0.05）;在药物浓度为30μg/ml、60μg/ml和120μg/ml并分别作用24h和48h时,Caspase-3活性逐渐增强。结论南蛇藤乙酸乙酯提取物抑制HepG2细胞增殖和诱导细胞凋亡的作用可能与其增强Caspase-3活性有关。     

雪松松针总黄酮的体外抗肿瘤作用

目的研究雪松松针总黄酮的体外抗肿瘤活性。方法采用MTT实验进行体外增殖抑制作用研究,从人宫颈癌He La细胞株、人胃癌MKN45细胞株、人肺癌A549细胞株、人肝癌Hep G2细胞株及人胶质瘤SHG44细胞株中筛选雪松松针总黄酮最敏感瘤株,采用细胞流式仪进行细胞周期及凋亡研究。结果雪松松针总黄酮不同浓度对各肿瘤细胞均有增殖抑制作用,并具剂量依赖性,对人肺癌细胞株A549、人肝癌细胞株Hep G2作用48 h后,IC50分别为211.39μg/ml和114.12μg/ml。结合MTT实验结果及IC50值,发现Hep G2细胞对雪松松针总黄酮最为敏感(P<0.05)。雪松松针总黄酮能够阻滞Hep G2细胞于G0/G1期,并诱导其凋亡。结论雪松松针总黄酮不同剂量组对5株肿瘤细胞均有一定抑制作用,其中对Hep G2细胞抑制作用最为显著。     

高良姜挥发油对不同肿瘤细胞株增殖的影响

目的评估高良姜挥发油对不同肿瘤细胞株的增殖抑制作用。方法利用水蒸气蒸馏法提取高良姜根茎的挥发油成分,采用MTT法观察其对人肝癌HepG2细胞、人结肠癌HT29细胞、人鼻咽癌CNE-2Z细胞、人甲状腺癌SW579细胞及人宫颈癌Hela细胞的增殖抑制率及半数抑制浓度(IC50)。结果高良姜挥发油提取率达1.2%,其可呈剂量依赖性抑制HepG2、HT29、CNE-2Z、SW579、Hela细胞株增殖,对HT29、Hela、CNE-2Z、HepG2、SW579细胞株的IC50值分别为2 352、717、458、431、329μg/mL。结论高良姜挥发油成分对多种类型肿瘤细胞的增殖均有一定抑制作用。     

重楼醇提物对恶性胸腹水中原代肿瘤细胞的抗肿瘤作用

目的研究中药重楼醇提物对恶性胸腹水中原代肿瘤细胞的抗肿瘤作用。方法收集25例经病理确诊的恶性胸腹水并分离原代肿瘤细胞，用CCK8法检测原代细胞对重楼醇提物及化疗药的药物敏感性，逆转录-聚合酶链反应（RT—PCR）法检测重楼醇提物对凋亡相关蛋白survivin mRNA表达的作用。结果重楼醇提物对人胃癌、肝癌、肺癌、大肠癌等4株细胞系的半数抑制浓度（IC50）平均值为41．13μg/ml，对25例恶性胸腹水中原代肿瘤细胞IC50平均值为82．33μg/ml，两者无显著差异（P〉0．05）。重楼醇提物对大肠癌来源的腹水中原代肿瘤细胞的IC50值显著高于其他组（P〈0．05），对胃癌、肺癌及其他消化道肿瘤来源的胸腹水中原代肿瘤细胞的抗肿瘤作用无明显差异（P〉0．05）。8例对重楼醇提物耐药的原代肿瘤细胞对多西紫杉醇、氟尿嘧啶、顺铂存在交叉耐药，而对化疗药物耐药的原代肿瘤细胞对重楼无交叉耐药。重楼醇提物对部分细胞系及原代细胞中凋亡相关蛋白survivin mRNA有下调作用（P〈0．05）。结论重楼醇提物对恶性胸腹水中原代肿瘤细胞，尤其是对化疗药物耐药的肿瘤细胞仍有一定的抗肿瘤作用。     

紫杉醇增强TRAIL诱导的胃癌BGC823细胞凋亡的机制

目的 探讨紫杉醇增强TRAIL诱导的胃癌BGC823细胞凋亡的机制。方法胃癌BGC823细胞传代堵养后,取对数生长期细胞用于实验。采用MTT法测定细胞活力,流式细胞仪检测细胞凋亡,Westernblot检测Akt、p-Akt蛋白表达。结果在胃癌BGC823细胞中,100ng／ml的TRAIL可致少量的细胞凋亡,同时检测到Akt的磷酸化。紫杉醇作用胃癌BGC823细胞24h,IC50剂量为8．97μg／ml。与单药TRAIL和紫杉醇相比,TRAIL（100ng／m1）联合紫杉醇（8．97μg／ml,24h的IC50剂量）对细胞的诱导凋亡作用明显增强（P〈0．05）。免疫印迹结果显示,TRAIL（100ng／ml）作用BGC823细胞24h,活化了Akt蛋白,而8．97μg／ml的紫杉醇抑制了Akt的磷酸化。TRAII（100ng／ml）联合紫杉醇（8．97μg/ml）作用后,TRAIL引起的Akt磷酸化被抑制。结论紫杉醇通过抑制TRAIL引起的Akt磷酸化,从而增强了TRAIL诱导的胃癌BGC823细胞凋亡。     

连翘醇提物对恶性胸腹水中原代肿瘤细胞的抗肿瘤作用

目的 研究中药连翘醇提物对恶性胸腹腔积液中原代肿瘤细胞的抗肿瘤作用. 方法 收集25例经病理确诊的恶性胸腹腔积液并分离原代肿瘤细胞,用CCK8法检测原代肿瘤细胞对连翘醇提物及化疗药的药物敏感性,提取细胞RNA,用荧光定量逆转录-聚合酶链反应(RT-PCR)法检测连翘醇提物对凋亡相关蛋白基因Survivin mRNA、Bcl-2 mRNA表达的作用. 结果 连翘醇提物对4种细胞系(胃癌细胞株BGC-823、肝癌细胞株SMMC-7721、肺癌细胞株A549和大肠癌细胞株LOVO )的半数抑制浓度(IC50)平均值为 191.88 μg/ml,对25例恶性胸腹腔积液中原代肿瘤细胞IC50平均值为406.13 μg/ml,两者无显著差异(P＞0.05).连翘醇提物对大肠癌、胃癌、肺癌及其他消化道肿瘤来源的胸腹腔积液中原代肿瘤细胞的抗肿瘤作用无明显差异(P＞0.05).连翘醇提物对接受化疗患者的胸腹腔积液中原代肿瘤细胞的IC50值为543.13 μg/ml,显著高于未接受化疗患者,年龄、性别以及体腔积液类型组间IC50值均无统计学差异.7例对连翘醇提物耐药的原代肿瘤细胞对多西紫杉醇、氟尿嘧啶、顺铂存在交叉耐药,而对化疗药物耐药的原代肿瘤细胞对连翘醇提物无交叉耐药.连翘醇提物对部分细胞系及原代细胞中凋亡相关蛋白Survivin mRNA和Bcl-2 mRNA有下调作用(P＜0.05). 结论 中药连翘醇提物对恶性胸腹腔积液中原代肿瘤细胞,尤其是对化疗药物耐药的原代肿瘤细胞仍有一定的抗肿瘤作用.     

Combined treatment with the checkpoint abrogator UCN-01 and MEK1/2 inhibitors potently induces apoptosis in drug-sensitive and -resistant myeloma cells through an IL-6-independent mechanism

The effects of combined exposure to the checkpoint abrogator UCN-01 and pharmacologic MEK1/2 inhibitors were examined in human multiple myeloma (MM) cell lines. Treatment of RPMI8226, NCI-H929, and U266 MM cells with a minimally toxic concentration of UCN-01 (150 nM) for 24 hours resulted in mitogen-activated protein (MAP) kinase activation, an effect that was blocked by coadministration of the MEK1/2 inhibitor PD184352. These events were accompanied by enhanced activation of p34(cdc2) and a marked increase in mitochondrial damage (loss of DeltaPsim; cytochrome c and Smac/DIABLO (direct IAP binding protein with low pI) release), poly(ADP-ribose) polymerase (PARP) cleavage, and apoptosis. PD184352/UCN-01 also dramatically reduced clonogenic survival in each of the MM cell lines. In contrast to As(2)0(3), apoptosis induced by PD184352/UCN-01 was not blocked by the free-radical scavenger N-acetyl-L-cysteine. Whereas exogenous interleukin 6 substantially prevented dexamethasone-induced lethality in MM cells, it was unable to protect them from PD184352/UCN-01-induced apoptosis despite enhancing Akt activation. Insulinlike growth factor 1 (IGF-1) also failed to diminish apoptosis induced by this drug regimen. MM cell lines selected for a high degree of resistance to doxorubicin, melphalan, or dexamethasone, or displaying resistance secondary to fibronectin-mediated adherence, remained fully sensitive to PD184352/UCN-01-induced cell death. Finally, primary CD138(+) MM cells were also susceptible to UCN-01/MEK inhibitor-mediated apoptosis. Together, these findings suggest that simultaneous disruption of cell cycle and MEK/MAP kinase signaling pathways provides a potent stimulus for mitochondrial damage and apoptosis in MM cells, and also indicate that this strategy bypasses the block to cell death conferred by several other well-described resistance mechanisms.     

Differential drug sensitivity of human neuroblastoma cells

A 6-day in vitro growth-inhibition assay was used to determine relative sensitivity of six human neuroblastoma cell lines to three classes of cancer chemotherapeutic agents: antimetabolites (methotrexate, methasquin, and cytarabine); antimitotics (vincristine, vinblastine, vindesine, colchicine, and demecolcine); and antibiotics (dactinomycin and doxorubicin). Human fibroblast lines served as a reference standard. Whereas response to antimetabolites by four of five neuroblastoma lines tested was similar to that of fibroblasts, SK-N-MC cells were significantly more sensitive (fivefold to 16-fold) to the three drugs. Human neuroblastoma cell lines were also differentially sensitive to antimitotics, especially to vincristine. In particular, SK-N-MC, IMR-32, and LA-N-2 cells were threefold to 17-fold more sensitive to this drug than were the SK-N-SH and SK-N-BE(2) lines. With the exception of SK-N-SH, all of the human neuroblastoma lines were considerably more sensitive to vincristine than were human fibroblasts. The same three highly vincristine-responsive lines were also significantly more sensitive to the other alkaloidal drugs as compared to fibroblasts. However, human neuroblastoma and fibroblastic cells responded similarly to the two antibiotics. The only cellular attribute consistently correlated with greater sensitivity to the antimitotics among the six cell lines tested was expression of the neurotransmitter biosynthetic enzyme choline acetyltransferase. A differential response to the vinca alkaloids was also exhibited by clonal sublines of SK-N-SH. One subpopulation (SH-EP) expressing a nonneuronal, substrate-adherent, variant phenotype was at least fourfold to eightfold more drug sensitive than its neuroblastic counterpart (SH-SY5Y) or the parental SK-N-SH population. In addition to confirming reports of clinical efficacy of the various classes of agents, these data have demonstrated a variation in response possibly related to type or degree of neuronal differentiation and emphasize the importance of understanding the phenotypic diversity commonly observed in neuroblastoma.     

Susceptibility of thyroid cancer cells to 7-hydroxystaurosporine-induced apoptosis correlates with Bcl-2 protein level.

7-Hydroxystaurosporine (UCN-01) is a selective protein kinase C (PKC) inhibitor and is being developed as a novel anticancer agent. Because of reports that PKC may be involved in the pathogenesis of some forms of thyroid cancers, we examined four thyroid carcinoma lines (FRO, KAT5, NPA, and WRO). These cells were found to have different susceptibility to UCN-01 treatment, and there appeared to be a correlation between UCN-01-induced death and expression levels of endogenous Bcl-2. KAT5 cells, which normally express a low amount of Bcl-2, exhibited significantly higher sensitivity to UCN-01-induced death than the other cell lines. Of interest, susceptibility did not relate to PKC activity or its inhibition by UCN-01. In order to investigate the role of Bcl-2 in UCN-01-induced death, KAT5 cells were transfected to overexpress Bcl-2. KAT5/Bcl-2 cells were capable of conferring resistance to UCN-01-induced death. Furthermore, upregulating of Bcl-2 by 1alpha,25-dihydroxyvitamin D3 (VD3) could protect primary thyroid cell from death induced by UCN-01. Both in situ TUNEL staining and the flow cytometric analysis of cytokeratin-18 (CK18) cleavage confirmed that UCN-01 was indeed inducing apoptosis, and that this effect was inhibited by increased expression of Bcl-2. These results suggest that the Bcl-2 can block the UCN-01-activated cell death pathway and that the expression of Bcl-2 is inversely related to thyroid carcinoma cell susceptibility to UCN-01. Therefore, the analysis of the expression of apoptosis suppressors provides a basis for the use of UCN-01 in the treatment of thyroid cancer.     

TNF-related apoptosis-inducing ligand (TRAIL) frequently induces apoptosis in Philadelphia chromosome-positive leukemia cells

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and Fas ligand (FasL) have been implicated in antitumor immunity and therapy. In the present study, we investigated the sensitivity of Philadelphia chromosome (Ph1)-positive leukemia cell lines to TRAIL- or FasL-induced cell death to explore the possible contribution of these molecules to immunotherapy against Ph1-positive leukemias. TRAIL, but not FasL, effectively induced apoptotic cell death in most of 5 chronic myelogenous leukemia-derived and 7 acute leukemia-derived Ph1-positive cell lines. The sensitivity to TRAIL was correlated with cell-surface expression of death-inducing receptors DR4 and/or DR5. The TRAIL-induced cell death was caspase-dependent and enhanced by nuclear factor kappa B inhibitors. Moreover, primary leukemia cells from Ph1-positive acute lymphoblastic leukemia patients were also sensitive to TRAIL, but not to FasL, depending on DR4/DR5 expression. Fas-associated death domain protein (FADD) and caspase-8, components of death-inducing signaling complex (DISC), as well as FLIP (FLICE [Fas-associating protein with death domain-like interleukin-1-converting enzyme]/caspase-8 inhibitory protein), a negative regulator of caspase-8, were expressed ubiquitously in Ph1-positive leukemia cell lines irrespective of their differential sensitivities to TRAIL and FasL. Notably, TRAIL could induce cell death in the Ph1-positive leukemia cell lines that were refractory to a BCR-ABL-specific tyrosine kinase inhibitor imatinib mesylate (STI571; Novartis Pharma, Basel, Switzerland). These results suggested the potential utility of recombinant TRAIL as a novel therapeutic agent and the possible contribution of endogenously expressed TRAIL to immunotherapy against Ph1-positive leukemias.     

Mitozantrone-induced toxicity and DNA strand breaks in leukaemic cells

By applying the fluorometric analysis of DNA unwinding (FADU) the in vitro effect of mitozantrone on DNA strand breaks was studied in seven different human leukaemic/lymphoma cell lines and in fresh leukaemic samples from seven patients with acute myeloid leukaemia refractory to conventional treatment. Pulse exposure to mitozantrone for 30 min invariably caused strand breaks. In the cell lines JM 1, KM3 and RPM I 8420 DNA strand breakage was progressive upon further incubation in drug free medium. These cell lines were killed by pulse exposure to mitozantrone. In the cell lines Molt 4, Daudi, Raji and HL-60, the DNA strand breaks induced by mitozantone were only moderate and these cell lines were also resistant to killing by mitozantrone in vitro. The leukaemic cells of one of the seven patients behaved also like the cell lines that were sensitive and a complete remission was achieved in this patient using mitozantrone as single agent therapy. The other patients with a pattern similar to the resistant cell lines proved to be clinically refractory. Thus mitozantrone induces rapidly progressive DNA strand breaks as early as 30 min in leukaemic cells that are sensitive. The measurement of DNA strand breaks by the fluorometric analysis of DNA unwinding is a rapid method which might predict response to drugs whose major effect is on the induction of strand breaks.     

Establishment and characterisation of two novel human KSHV- and EBV-negative Burkitt cell lines, GAL-01 and GAL-02, from a primary lymphomatous effusion

OBJECTIVES: Burkitt's lymphoma (BL) is a highly aggressive mature B-cell neoplasm comprising endemic, sporadic and immunodeficiency-associated variants. Human cell lines constitute a very useful tool to investigate the biology of lymphoid neoplasia. In this study, we succeeded in establishing two human cell lines, GAL-01 and GAL-02, from a HIV-negative patient with Epstein-Barr virus (EBV) -negative sporadic BL presenting as an effusion. GAL-01 and GAL-02 were established at diagnosis and after one course of polychemotherapy, respectively. The in vivo effusion occurred in a very peculiar clinical setting; the patient having a previous history of intestinal diffuse large B-cell lymphoma. METHODS: The morphologic, immunophenotypic and molecular genetic features of GAL cell lines are reported and compared with those of the parental tumour. The findings clearly demonstrated that the Burkitt effusion did not represent disease progression of the intestinal tumour, but represented a second primary haematological malignancy. The in vivo tumorigenic properties of the cells were tested by subcutaneous injection to NOD/SCID mice. RESULTS: Both cell lines were composed of medium-sized lymphoid cells with clumped chromatin, multiple medium-sized nucleoli and moderate amounts of vacuolated cytoplasm. GAL cells display the phenotype and genotype of a B-cell lineage (positive for CD20, CD79a and clonal rearrangement of Ig heavy chain), carry the c-MYC rearrangement by t(8;22)(q24;q11) translocation and are characterised by the expression of the germinal centre-associated antigens CD10, BCL6, CD38 and absent to low BCL2 expression. EBV and HHV8 were not identified within parental tumour or in cultured cells. Subcutaneous injection of both cell lines to NOD/SCID mice induced tumour formation. CONCLUSIONS: GAL-01 and GAL-02, two novel EBV-negative human BL cell lines represent a potentially useful experimental model to study the biology of BL possibly including the resistance to chemotherapy.     

Different induction of GRP78 and CHOP as a predictor of sensitivity to proteasome inhibitors in thyroid cancer cells

Proteasome inhibitors represent a novel class of antitumor agents with preclinical and clinical evidence of activity against hematological malignancies and solid tumors. Emerging lines of evidence suggest that the unfolded protein response is implicated in proteasome inhibitors-induced apoptosis. Glucose-regulated protein 78 kDa (GRP78) and CCAAT/enhancer-binding protein homologous protein (CHOP) as part of the unfolded protein response play critical roles in cell survival or death. Here we demonstrate that induction of GRP78 and CHOP are differently regulated upon proteasome inhibition in different thyroid cancer cell lines, and GRP78 levels as well as preferential induction of GRP78 or CHOP appears to be involved in the responsiveness. Insensitive ARO, 8305C, and 8505C cell lines inherently express relatively high levels of GRP78 compared with sensitive cell lines, and its levels are further up-regulated upon treatment with proteasome inhibitors. CHOP levels are dramatically induced in sensitive cell lines until 24 h after proteasome inhibition. On the other hand, only a slight increase is observed at 4 h in insensitive cell lines, and this increase is unable to be detected after 8 h. Insensitive cells are sensitized to proteasome inhibition by suppression of GRP78. Furthermore, suppression of CHOP induction or overexpression of GRP78 partially prevents proteasome inhibition-mediated cell death. Our study indicates a molecular mechanism by which the sensitivity of thyroid cancer cells is regulated by the level of GRP78 as well as preferential induction of GRP78 or CHOP upon treatment with proteasome inhibitors. Our experiments therefore suggest a novel approach toward sensitization of thyroid cancer cells to proteasome inhibitors.     

Regulation of tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in Burkitt's lymphoma cell lines

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potent inducer of apoptosis in sensitive cells and may be suitable for novel anti-cancer therapies aimed at inducing apoptosis via the activation of TRAIL receptors on malignant cells. Here we have characterized the TRAIL sensitivity of a panel of Burkitt's lymphoma (BL) cell lines. Overall, 5/12 BL cell lines and 1/2 lymphoblastoid cell lines were sensitive to TRAIL-induced apoptosis, although only one BL cell line approached the sensitivity of Jurkat cells, a widely used model for TRAIL-induced apoptosis. Whereas, 4/5 of the Epstein-Barr virus (EBV)-negative cell lines were TRAIL sensitive, only 1/7 EBV-positive BL cell lines were TRAIL sensitive. However, isogenic BL cell lines with different EBV status were not differently sensitive to TRAIL, indicating that EBV is not a major determinant of TRAIL sensitivity. All cell lines expressed the death receptor (DR)5 TRAIL receptor, whereas expression of DR4 was more variable. Differences in the expression of downstream signalling molecules [Fas-associated death domain protein (FADD), caspase 8] and inhibitors [decoy receptor 1 (DcR1), cellular FLICE-like inhibitory protein (c-FLIP)] did not correlate with TRAIL sensitivity. Therefore, a subset of BL cell lines are sensitive to TRAIL-induced apoptosis, however, the molecular mechanism that determines responsiveness remains to be identified.