Ex vivo purging of leukemia cells using tumor-necrosis-factor-related apoptosis-inducing ligand in hematopoietic stem cell transplantation.

The aim of this study was to evaluate the potential of tumor-necrosis-factor-related apoptosis-inducing ligand TRAIL to eradicate leukemia cell lines, while sparing normal hematopoietic stem cells. Human Jurkat and Molt-4 cell lines were used to optimize the purging process in umbilical cord blood (UCB) mononuclear cells. The Jurkat cell line was TRAIL sensitive and TRAIL-resistant Molt-4 cell line became sensitive after being treated with TRAIL and a low dose of doxorubicin (0.1 micro M), but UCB mononuclear cells remained resistant. DR4 expression was increased when Jurkat cells were treated with TRAIL, and DR5 expression increased after exposing Molt-4 cells to TRAIL plus a low dose of doxorubicin for 24 h. The expression of DR4 and DR5 in UCB mononuclear cells was unchanged after treatment with TRAIL, a low-dose doxorubicin, or TRAIL plus a low dose of doxorubicin. In TRAIL-sensitive Jurkat cells, caspases 8, 9, 3, and 7 were activated by TRAIL treatment and activation of caspases was augmented by TRAIL plus a low dose of doxorubicin than TRAIL or a low dose of doxorubicin alone in Molt-4 cells. Experiments involving mixture of UCB mononuclear cells and Jurkat or Molt-4 cells showed a marked eradication of leukemia cells and the limiting dilution assay demonstrated an eradication rate of more than 4 logs after 24 h incubation with 100 ng/ml of TRAIL in Jurkat cells. In the case of Molt-4 cells, the eradication rate was about 3 logs when TRAIL was used in combination with a low dose of doxorubicin. No significant decrease in the number of granulocyte-macrophage colony-forming unit) (CFU-GM) colonies was detected when UCB mononuclear cells were treated with TRAIL in combination with a low dose of doxorubicin. These results suggest that TRAIL offers the possibility of being used as an ex vivo purging agent for autologous transplantation in hematologic malignancies.     

Down regulation of membrane‐bound Neu3 constitutes a new potential marker for childhood acute lymphoblastic leukemia and induces apoptosis suppression of neoplastic cells

Membrane‐linked sialidase Neu3 is a key enzyme for the extralysosomal catabolism of gangliosides. In this respect, it regulates pivotal cell surface events, including trans‐membrane signaling, and plays an essential role in carcinogenesis. In this report, we demonstrated that acute lymphoblastic leukemia (ALL), lymphoblasts (primary cells from patients and cell lines) are characterized by a marked down‐regulation of Neu3 in terms of both gene expression (−30 to 40%) and enzymatic activity toward ganglioside GD1a (−25.6 to 30.6%), when compared with cells from healthy controls. Induced overexpression of Neu3 in the ALL‐cell line, MOLT‐4, led to a significant increase of ceramide (+66%) and to a parallel decrease of lactosylceramide (−55%). These events strongly guided lymphoblasts to apoptosis, as we assessed by the decrease in Bcl2/Bax ratio, the accumulation of Neu3 transfected cells in the sub G0–G1 phase of the cell cycle, the enhanced annexin‐V positivity, the higher cleavage of procaspase‐3. Therefore, the reduced expression of Neu3 in ALL could help lymphoblasts to survive, maintaining the cellular content of ceramide below a critical level. Interestingly, we found that Neu3 activity varied in relation to disease progression, increasing in clinical remission after chemotherapy, and decreasing again in patients that relapsed. In addition, a negative correlation was observed between Neu3 expression and the percentage of the ALL marker 9‐OAcGD3 positive cells. Consequently, Neu3 could represent a new potent biomarker in childhood ALL, to assess the efficacy of therapeutic protocols and to rapidly identify an eventual relapse.     

膜受体介导的细胞凋亡与细胞周期的关系

背景与目的：线粒体介导的细胞凋亡大部分与细胞周期相关,但膜受体介导的细胞凋亡是否与细胞周期有关尚不清楚。本研究旨在观察膜受体介导的人类细胞凋亡与细胞周期特异性,阐明膜受体介导的细胞凋亡与细胞周期的关系。方法：用肿瘤坏死因子-α、抗Fas抗体分别处理指数生长期的Molt-4、Jurkat以及健康人外周血淋巴细胞;应用Annexin V／PI和API等方法,通过流式细胞仪检测细胞凋亡和细胞周期特异性。结果：处于静止期的外周血淋巴细胞对凋亡诱导剂不敏感,凋亡率是6％-8％。Molt-4、Jurkat细胞以及加入植物血凝素刺激的外周血淋巴细胞经肿瘤坏死因子-α、抗Fas抗体诱导后出现了明显的细胞凋亡．凋亡率是15％-28％。膜受体介导的细胞凋亡主要发生在细胞周期的早G1期。结论：膜受体介导的细胞凋亡与细胞周期相关,具有细胞周期特异性。     

Mechanistic mathematical modelling of mercaptopurine effects on cell cycle of human acute lymphoblastic leukaemia cells

The antimetabolite mercaptopurine (MP) is widely used to treat childhood acute lymphoblastic leukaemia (ALL). To study the dynamics of MP on the cell cycle, we incubated human T-cell leukaemia cell lines (Molt-4 sensitive and resistant subline and P12 resistant) with 10 microM MP and measured total cell count, cell cycle distribution, percent viable, percent apoptotic, and percent dead cells serially over 72 h. We developed a mathematical model of the cell cycle dynamics after treatment with MP and used it to show that the Molt-4 sensitive controls had a significantly higher rate of cells entering apoptosis (2.7-fold, P<0.00001) relative to the resistant cell lines. Additionally, when treated with MP, the sensitive cell line showed a significant increase in the rate at which cells enter apoptosis compared to its controls (2.4-fold, P<0.00001). Of note, the resistant cell lines had a higher rate of antimetabolite incorporation into the DNA of viable cells (>1.4-fold, P<0.01). Lastly, in contrast to the other cell lines, the Molt-4 resistant subline continued to cycle, though at a rate slower relative to its control, rather than proceed to apoptosis. This led to a larger S-phase block in the Molt-4 resistant cell line, but not a higher rate of cell death. Gene expression of apoptosis, cell cycle, and repair genes were consistent with mechanistic dynamics described by the model. In summary, the mathematical model provides a quantitative assessment to compare the cell cycle effects of MP in cells with varying degrees of MP resistance.     

TNF-α诱导Molt-4细胞Bcl-2蛋白磷酸化的周期特异性

目的以肿瘤坏死因子-α诱导的Molt-4细胞凋亡为模式,观察Bcl-2蛋白磷酸化有无细胞周期特异性,探讨膜受体途径介导的细胞凋亡的周期特异性发生机制。方法TNF-α诱导Molt-4细胞凋亡,API法检测细胞凋亡的细胞周期特异性。流式细胞仪分选各个细胞周期时相的细胞群,蛋白免疫印迹检测Bcl-2蛋白的细胞周期特异性表达。结果TNF-α诱导Molt-4细胞凋亡主要发生在细胞周期的G1期。Bcl-2蛋白在TNF-α诱导后表达增加,G1期Molt-4细胞中bcl-2部分磷酸化,在时间上与凋亡发生的时间一致。结论加入TNF-α培养的Molt-4细胞Bcl-2蛋白磷酸化失活与细胞凋亡的细胞周期时相一致,具有细胞周期特异性。     

血液肿瘤细胞对氧化砷的敏感性与其抗氧化能力的关系

目的　探讨血液肿瘤细胞对三氧化二砷 (As2 O3 )的敏感性和细胞抗氧化能力的关系。方法　应用 9个血液肿瘤细胞系 ,通过细胞活力、形态学和流式细胞仪检测细胞凋亡 ,并测定细胞系的谷胱甘肽 (GSH)含量和 4种抗氧化酶的活性。结果　除了HL 6 0、U937、K5 6 2和Jurkat细胞外 ,其他5个细胞对As2 O3 诱导的凋亡敏感。与敏感细胞系比较 ,As2 O3 耐受细胞系存在较高的GSH含量和(或 )过氧化氢酶活性。谷胱甘肽过氧化物酶、谷胱甘肽S转移酶和超氧化物歧化酶活性与细胞对As2 O3 诱导凋亡效应敏感性无明显相关。结论　细胞内GSH水平和过氧化氢酶的活性是决定血液肿瘤细胞对As2 O3 敏感性的重要因素。     

Isolation and characterization of adriamycin-resistant HL-60 cells which are not defective in the initial intracellular accumulation of drug

Two human leukemia cell lines (Molt-4 and HL-60) have been used for establishing cells which exhibit a low level resistance to Adriamycin. Analysis of drug uptake patterns shows that the Molt-4 resistant cells are defective in the initial intracellular accumulation of drug. In contrast to Molt-4 the levels of drug which accumulate in the sensitive and resistant HL-60 cells during a 60-min incubation period are essentially the same. However, when incubations are continued there is a major reduction in intracellular drug levels in the resistant cell. Further studies show that resistant cells incubated in the presence of drug for extended time periods efflux drug at a rate considerably greater than that exhibited by the sensitive parent line. Similar efflux patterns are obtained with nuclei isolated from drug-sensitive and -resistant cells. Additional studies using an in vitro phosphorylation system demonstrate distinct protein changes in membranes of Molt-4 and HL-60 resistant cells. Thus, we have found that a membrane fraction from the Molt-4 resistant line contains a Mr 170,000 protein which is not detected in a similar fraction from cells sensitive to drug. HL-60 resistant membranes contain two proteins with molecular weights of 150,000 and 120,000 which are also not found in membranes from drug-sensitive cells. The results of this study suggest that drug resistance in HL-60 cells is related to an efflux mechanism which is triggered only after cells are exposed to drug for prolonged periods.     

硼替佐米调控内质网应激诱导人急性T淋巴细胞白血病细胞株凋亡的机制探讨

目的:探讨硼替佐米对人急性T淋巴细胞白血病（T cell acute lymphoblastic leukemia，T-ALL）细胞株Molt-4细胞凋亡的影响。方法:硼替佐米（0、100、200和400 nmol/L）处理人急性T淋巴细胞白血病细胞株Molt-4细胞后，运用MTT法测定Molt-4细胞活力；使用Hoechst 33258染色法观察凋亡细胞形态；采用荧光定量PCR法测定Bax以及Bip mRNA水平；运用Western blot法测定Bax以及Bip蛋白水平。结果:100、200和400 nmol/L的硼替佐米处理Molt-4细胞24 h后，可浓度依赖性地降低细胞活力。100、200和400 nmol/L的硼替佐米作用细胞24 h后，Molt-4细胞核发生固缩或裂解。硼替佐米（100、200和400 nmol/L）处理细胞24 h后，Molt-4细胞的Bax mRNA和蛋白表达水平明显增加且可显著上调Bip mRNA和蛋白表达水平。结论:硼替佐米可诱导人急性T淋巴细胞白血病细胞株Molt-4细胞凋亡，作用机制可能与它调控内质网应激有关。     

The inhibition of ERK/MAPK not the activation of JNK/SAPK is primarily required to induce apoptosis in chronic myelogenous leukemic K562 cells

In this study, the downstream signaling of Bcr-Abl tyrosine kinase responsible for apoptosis resistance was investigated. DNA fragmentation, a hallmark of apoptosis, was observed after 2 days of herbimycin A treatment with a peak on 3 day. During the apoptosis induced by the treatment of herbimycin A, stress-activated protein kinase (SAPK) and p38 kinase were activated time- and dose-dependently, while extracellular signal-regulated kinase (ERK) was inhibited. However, apoptosis was induced by the treatment of PD98059, a specific inhibitor of MEK (MAPK or ERK kinase), not by the treatment of sorbitol, a strong activator of SAPK and p38 kinase. Although K562 cells were very resistant to sorbitol-induced apoptosis, DNA fragmentation was induced rapidly in Jurkat, HL-60 and U937 cells after exposure to sorbitol, despite that these apoptosis-sensitive cells have similar or lower activities of JNK/SAPK and p38 kinase compared with K562 cells after treatment of sorbitol. K562 cells had a much higher basal activity of ERK/MAPK than other apoptosis-sensitive cell lines, which were very susceptible to apoptosis induced by low dose of PD98059 compared with K562 cells. In HL-60 cells, sorbitol-induced apoptosis was prevented by the treatment of phorbol myristate 13-acetate (PMA), which activates the ERK/MAPK pathway, and this was blocked by PD98059. From these results, it could be suggested that the inhibition of ERK/MAPK not the activation of JNK/SAPK is primarily required to induce apoptosis in K562 cells.     

Aberrant expression of ganglioside and asialoglycosphingolipid antigens in adult T-cell leukemia cells

Gangliosides (GM3, GD3, GM2, gangliotetraose-series gangliosides) and their asialo derivatives of several adult T-cell leukemia (ATL) cell lines (ATL-1K, ATL-3I, ATL-5S, and MT-2 cells) and the lymphocytes from a patient with ATL were quantified by highly sensitive enzyme-immunostaining on silica gel thin layer chromatograms using specific antiglycolipid antibodies. GM2 and GD3 gangliosides and asialo GM1 (GA1) newly appeared in all cultured ATL cells and the lymphocytes from patients with ATL but not in normal human T-lymphocyte-rich fraction. Gangliotetraose-series gangliosides, GM1a, GD1a and GD1b, were also found in cultured ATL cells, but were not detected in normal human lymphocytes or the lymphocytes of a patient with ATL. Quantitative immunostaining analysis of GM2, GD3 gangliosides and GA1 in T-cell lines from non ATL leukemia (Molt-3, CEM and Jurkat) revealed GM2 gangliosides in all the T-cells from non ATL tested and GA1 in Jurkat cells, but no GD3 ganglioside was found in the non ATL leukemia cells tested. The above results indicate that ganglioside GD3 may be a T-cell glycosphingolipid antigen associated with ATL, and ganglioside GM2 and GA1 may be useful as surface markers related with ATL, as well as T-cell lymphoma. The contents of GA1, GM3, GD3, GM2 and gangliotetraose-series gangliosides in ATL cells were all different, even though all the cells used have a common antigen reactive with monoclonal OKT-4 antibody, indicating that there are several subsets of human inducer/helper T-cells, which possess different metabolism and expression of gangliosides.     

Selective susceptibility of transformed T lymphocytes to induction of apoptosis by PSC 833, an inhibitor of P-glycoprotein

P-glycoprotein is a cellular efflux pump. The P-glycoprotein inhibitor PSC 833 causes apoptosis of cancer cells and induces a rise in the intracellular levels of ceramide. Our aims were to determine whether a cause and effect relationship exists between these two actions of PSC 833, and to assess whether the PSC 833-induced apoptosis is restricted to transformed cells. Apoptosis was determined by flow cytometry and radioactive quantitation of DNA fragmentation. PSC 833 induced apoptosis in the human T leukemia cell lines: Molt-4 and Jurkat. Analysis of the apoptosis in Molt-4 and Jurkat cells revealed that PSC 833 induced a rise in the cellular ceramide levels (as measured by the DG kinase assay). PSC 833-induced apoptosis was significantly reduced by specific inhibitors of ceramide de novo synthesis (i.e., fumonisin B1 and L-cycloserine). On the other hand, PSC 833 did not induce apoptosis in normal peripheral blood T cells regardless of whether these cells were quiescent, activated, or proliferating. Our results suggest that PSC 833 induces apoptotic death in human transformed T lymphocytes through an increase in ceramide de novo synthesis. In addition, normal lymphocytes are not susceptible to induction of apoptosis by PSC 833. This difference between normal lymphocytes and leukemia cells presents a potential target for chemotherapy.     

小檗碱诱导白血病Molt-4细胞株凋亡及对NF-κB/p65、Caspase-3表达的影响

 【摘要】　目的　研究小檗碱对急性T淋巴细胞白血病细胞株Molt-4增殖的抑制作用及其机制探讨。方法　将0、10、100 μg／ml小檗碱作用于Molt-4细胞后,经细胞形态学观察、流式细胞术、DNA凝胶电泳检测细胞凋亡情况,用免疫印迹法检测NF-κB及Caspase-3的表达。结果　小檗碱作用于Molt-4细胞后,光镜下可见形成凋亡小体,流式细胞术可见存在G2／M期增加和S期减少,DNA凝胶电泳出现典型的DNA梯形条带。Western blot法检测发现部分Caspase-3酶原被激活,而细胞核中p65表达降低。结论　小檗碱可导致白血病细胞Molt-4细胞凋亡,而NF-κB、Caspase-3可能参与了Molt-4细胞凋亡的调控。     

An echo-contrast agent, Levovist, lowers the ultrasound intensity required to induce apoptosis of human leukemia cells

To verify the effect of echo-contrast agent (ECA) on apoptosis induced by ultrasound, leukemia cell lines (Jurkat, Molt-4 and U937) were sonicated at intensities previously shown to induce optimal apoptosis with or without Levovist, an ECA. The results showed that loss of viability and apoptosis can be induced in all three cell lines, apoptosis highest with Molt-4, based on viability and DNA fragmentation assay. Such finding was supported by corresponding increase of cells with low mitochondrial membrane potential, high superoxide production, increased intracellular calcium concentration, and phosphorylation of histone H2AX after sonication. Optimal ultrasound condition was 0.3W/cm(2), 1MHz, 10% duty factor pulsed at 100Hz; but in the presence of Levovist, an apparent shift of cell killing induction was observed at 0.2W/cm(2). While these results further confirmed previous findings on ultrasound-induced apoptosis, they also suggest that use of an enhancing factor, such as addition of ECA, may be useful in cancer therapy when a much lower intensity is desired.     

Targeting cannabinoid receptors to treat leukemia: role of cross-talk between extrinsic and intrinsic pathways in Delta9-tetrahydrocannabinol (THC)-induced apoptosis of Jurkat cells

Targeting cannabinoid receptors has recently been shown to trigger apoptosis and offers a novel treatment modality against malignancies of the immune system. However, the precise mechanism of apoptosis in such cancers has not been previously addressed. In this study, we used human Jurkat leukemia cell lines with defects in intrinsic and extrinsic signaling pathways to elucidate the mechanism of apoptosis induced by Delta9-tetrahydrocannabinol (THC). We observed that Jurkat cells deficient in FADD or caspase-8 were partially resistant to apoptosis, while dominant-negative caspase-9 mutant cells were completely resistant to apoptosis. Use of caspase inhibitors confirmed these results. Furthermore, overexpression of Bcl-2 rendered the cells resistant to THC at early time points but not upon prolonged exposure. THC treatment led to loss of Deltapsi(m), in both wild-type and FADD-deficient Jurkat cells thereby suggesting that THC-induced intrinsic pathway was independent of FADD. THC treatment of wild-type Jurkat cells caused cytochrome c release, and cleavage of caspase-8, -9, -2, -10, and Bid. Caspase-2 inhibitor blocked THC-induced caspase-3 in wild-type Jurkat cells but not loss of Deltapsi(m). Together, these data suggest that the intrinsic pathway plays a more critical role in THC-induced apoptosis while the extrinsic pathway may facilitate apoptosis via cross-talk with the intrinsic pathway.     

Treatment of neuroblastoma meningeal carcinomatosis with intrathecal application of alpha-emitting atomic nanogenerators targeting disialo-ganglioside GD2.

Labeling of specific antibodies with bifunctional chelated Actinium-225 ((225)Ac; an alpha generator) allows the formation of new, highly potent and selective alpha-emitting anticancer drugs. We synthesized and evaluated a radioimmunoconjugate based on 3F8, an IgG(3) antibody that specifically binds to ganglioside GD2, which is overexpressed by many neuroectodermal tumors including neuroblastoma. The (225)Ac-1,4,7,10-tetra-azacylododecane (DOTA)-3F8 construct was evaluated for radiochemical purity and sterility, immunoreactivity, cytotoxicity in vitro, induction of apoptosis on GD2-positive cells, as well as for pharmacological biodistribution and metabolism of the (225)Ac generator and its daughters in a nude mouse xenograft model of neuroblastoma. The (225)Ac-3F8 showed an IC(50) of 3 Bq/ml (80 pCi/ml) on the neuroblastoma cell line, NMB7, in vitro. Apoptosis of these cells was not observed. Biodistribution in mice showed specific targeting of a subcutaneous tumor; there was redistribution of the (225)Ac daughter nuclides mainly from blood to kidneys and to small intestine. Toxicity was examined in cynomolgus monkeys. Monkeys injected with 1 to 3 doses of intrathecal (225)Ac-3F8 radioimmunoconjugate (80 to 150 kBq/kg total dose) did not show signs of toxicity based on blood chemistry, complete blood counts, or by clinical evaluations. Therapeutic efficacy of intrathecal (225)Ac-3F8 was studied in a nude rat xenograft model of meningeal carcinomatosis. The (225)Ac-3F8 treatment improved survival 2-fold from 16 to 34 days (P = 0.01). In conclusion, in vivo alpha generators targeted by 3F8 warrant additional study as a possible new approach to the treatment of carcinomatous meningitis.     

硼替佐米联合多柔比星对淋巴母细胞淋巴瘤Molt-4细胞的作用

 目的　研究硼替佐米联合多柔比星对淋巴母细胞淋巴瘤细胞株Molt-4的作用。方法　硼替佐米与多柔比星作用于Molt-4细胞后,采用CCK-8检测细胞的增殖,锥虫蓝染色计数细胞的活性,应用AnnexinV-FITC凋亡试剂盒及线粒体膜电位检测试剂盒经流式细胞术（FCM）检测细胞凋亡,用免疫标记经FCM检测细胞膜表面Fas的表达。结果　硼替佐米与多柔比星单药作用对Molt-4细胞具有生长抑制作用,生长抑制率与药物浓度呈正相关（r＝0.863,P＝0.027;r＝0.915,P＝0.038）;两者联合应用对细胞生长抑制有协同作用,48 h作用最明显,抑制率达（57.24±0.10）%;联合应用细胞总凋亡率增高48 h达（23.08±1.25）%,与硼替佐米和多柔比星单药组（15.11±1.09）%和（15.96±0.81）%比较差异具有统计学意义（t值分别为0.046,0.037,均P＜0.05）,早期凋亡率无明显变化（t值分别为0.052、0.048,均P＞0.05）。线粒体膜电位检测显示联合作用较单药作用细胞凋亡率升高分别为15.84 %、5.38 %、5.52 %,FCM检测药物联合作用后细胞表面Fas表达无明显改变（t＝0.040,P＞0.05）。结论　硼替佐米联合多柔比星能够有效抑制淋巴母细胞淋巴瘤细胞株Molt-4细胞增殖并诱导其凋亡,作用机制与活化线粒体凋亡途径有关,与外源性凋亡途径无关。     

Preferential induction of apoptosis by interferon (IFN)-beta compared with IFN-alpha2: correlation with TRAIL/Apo2L induction in melanoma cell lines.

On the basis of in vitro inhibition of tumor cell growth, IFNs have been generally considered to be antiproliferative proteins. To probe further the potential mechanisms of the antitumor effects of IFNs, we have assessed apoptosis in response to IFN-alpha2 and IFN-beta in cell lines of varied histologies, with a focus on melanomas. Many of the cell lines tested underwent apoptosis in response to IFN-beta, as assessed both by Annexin V and terminal deoxynucleotidyl transferase-mediated nick end labeling staining. In general, IFN-beta had greater growth inhibitory and proapoptotic effects than IFN-alpha2 on all cell lines. The melanoma cell line WM9, sensitive to growth inhibition by IFNs, had a greater degree of apoptosis than A375 melanoma cells, which were largely resistant to antigrowth effects of IFNs. IFN-beta-induced apoptosis was dependent on activation of the caspase cascade with cleavage of caspases 3, 8, and 9 and of the caspase 3 substrate, poly(ADP-ribose) polymerase. Caspase inhibitors benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl keton or benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethyl keton, inhibited IFN-beta-induced apoptosis. Other changes associated with apoptosis, including the movement of cytochrome c from mitochondria to cytoplasm and DNA fragmentation, were also identified in response to IFN-beta. Apo2L ligand [tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)] was one of the early genes induced by IFN-beta in apoptosis-sensitive WM9 cells. Other sensitive melanoma cell lines had a similar IFN-beta-specific induction of TRAIL. Neutralizing antibody to TRAIL inhibited IFN-beta-induced apoptosis in WM9 cells. In resistant A375 cells, IFN-beta did not induce TRAIL/Apo2L expression. Thus, induction of TRAIL by IFNs in some tumor types may initiate the apoptotic cascade. This study offers another mechanism for the antitumor effects of IFNs.     

紫杉醇诱导急性白血病细胞S期特异性凋亡

背景与目的:化疗药物的细胞周期特异性是临床设计化疗方案的重要依据。一般认为,紫杉醇为G2/M期特异性化疗药物。但是近来的相关研究却表明,药物在体内的细胞周期特异性可能与体外不同。本研究旨在观察紫杉醇作用于不同生长状态下白血病细胞的细胞周期特异性有无改变。方法:利用流式细胞分析技术,对紫杉醇作用于人急性淋巴细胞性白血病细胞株Molt-4以及作用于17例急性白血病细胞所诱导的凋亡效应进行了观察。结果:紫杉醇诱导在对数生长状态下的Molt-4细胞株G2/M期特异性凋亡,在高密度状态下培养的Molt-4细胞为G0/G1期特异性凋亡,而在临床标本中诱导S期特异性凋亡。结论:紫杉醇在不同模型诱导不同的细胞周期特异性凋亡。与一般认为的不同,紫杉醇引起患者白血病细胞S期特异性凋亡。这些不同很可能与细胞处于不同的生长状态有关。     

Intracellular mediators of erucylphosphocholine-induced apoptosis

Induction of apoptosis contributes to the cytotoxic action of the intravenously applicable alkylphosphocholine erucylphosphocholine (ErPC). To define molecular requirements for ErPC-induced apoptosis, activation of caspases-8, -9 and -3 and cleavage of the caspase-3 substrates PARP and ICAD were tested in normal Jurkat T cells, Jurkat cells resistant to death receptor (CD95 or TNFalpha-related apoptosis inducing ligand (TRAIL)-induced apoptosis, Jurkat cells lacking caspase-8 or Fas-associated death domain (FADD) Jurkat cells expressing a dominant-negative caspase-9 or overexpressing Bcl-2 as well as BJAB B-lymphoma cells expressing a dominant-negative FADD (FADD-DN). ErPC induced a time- and dose-dependent apoptotic cell death in Jurkat and BJAB cells, which was characterized by breakdown of the phosphatidylserine asymmetry, depolarization of the mitochondrial membrane potential, release of cytochrome c, activation of caspases-9, -8 and -3, cleavage of PARP and ICAD, as well as chromatin condensation. ErPC-induced apoptosis was independent from CD95-receptor signaling and FADD since CD95- and TRAIL-resistant, caspase-8- and FADD-negative Jurkat cells, as well as BJAB cells expressing FADD-DN were sensitive to ErPC-induced apoptosis. In contrast, inhibition of caspase-9 and overexpression of Bcl-2 significantly reduced ErPC-induced caspase activation and apoptosis. Thus, ErPC triggers apoptosis via a Bcl-2-dependent mitochondrial but death receptor-independent pathway.     

Dysregulation of apoptosis and a novel mechanism of defective apoptotic signal transduction in human B-cell neoplasms

Apoptotic cell death is essential for normal B-cell development and for shaping the B-cell repertoire. Dysregulation of the Bcl-2 related proteins and alterations of the p53/p14ARF pathway are implicated in the pathogenesis and treatment resistance in human B-cell malignancies. We found a novel mechanism of dysregulated apoptosis in human B lymphoma Raji cells that differs from that of altered Bcl-2 and p53 functions. This cell line was resistant to nuclear apoptosis induced by various stimuli, and neither mitochondrial activation nor activation of caspase-3 led to DNA fragmentation. DNA in purified Raji nuclei was degraded in the presence of lysates from the apoptosis-sensitive cell line HL-60, whereas Raji cell lysates did not induce DNA fragmentation in HL-60 nuclei. Cleavage of ICAD/DFF-45 was normal. These results indicate that the apoptosis signal transduction pathway is defective downstream of caspase-3 in Raji cell cytoplasm. Therefore, exploring the molecular mechanism in this system should provide insight into apoptosis resistance in human B-cell malignancies.