拓扑异构酶I抑制剂诱导白血病HL60/VCR耐药细胞凋亡的研究

目的　研究拓扑异构酶I抑制剂 (topotecan ;TPT)对白血病耐药细胞HL6 0 /VCR诱导凋亡的作用。方法　瑞氏 吉姆萨染色和吖啶橙 /溴化乙啶 (AO/EB)染色进行形态观察 ,采用TUNNEL、流式细胞仪检测细胞周期和AnnexinV观察TPT对HL6 0 /VCR细胞的抑制效应和促凋亡作用。WesternBlot检测bcl 2、活化的caspase 3和P糖蛋白 (Pgp)的表达变化。 结果　经TPT处理后的HL6 0 /VCR细胞 ,在光镜和AO/EB染色中均可见到典型的凋亡细胞形态学改变 ,并具有时间和剂量依赖性 ;AnnexinV染色后能检测到早期凋亡细胞 (2 6 .8% ) ,细胞周期显示 :G1期细胞比例增高 ,S期减低 ,并有 2 1.8%凋亡峰 ;TUNNEL能检测到 (6 2 .2± 3.5 ) %的阳性细胞 ;伴有活化的caspase 3的表达和bcl 2的下调 ,而Pgp的表达在细胞凋亡前后无变化。结论　TPT能诱导白血病耐药细胞凋亡 ,该过程伴有caspase 3的活化和bcl 2的表达下调。     

拓扑异构酶Ⅰ抑制剂与肿瘤耐药的相关性研究进展

TOPO Ⅰ是调节核酸拓扑构型的关键酶,已成为重要的抗癌药物研究新靶点。肿瘤对细胞TOPOⅠ抑制剂产生耐药是一个相当复杂的细胞生理化过程,也是化疗失败的重要原因。喜树碱类药物是经典的TOPO Ⅰ抑制剂,一些非喜树碱类TOPO Ⅰ抑制剂也见报道。     

黄酮类化合物的抗癌作用

黄酮类化合物广泛存在于植物界,是中草药的重要成分,其生物活性多种多样,并具有很强的药理活性.近年来大量研究显示,黄酮类化合物在肺癌、结肠癌、乳腺癌、前列腺癌、胰腺癌等的治疗和预防中均发挥重要作用.其抗癌机制涉及阻滞癌细胞增殖、诱导肿瘤细胞凋亡、抗氧化活性、抑制新生血管形成等各方面.     

急性淋巴细胞白血病患者DNA拓扑异构酶的表达及临床意义

 目的 探讨急性淋巴细胞白血病（ALL）患者DNA拓扑异构酶（Topo）mRNA水平的表达及其临床意义。方法 用半定量反转录-聚合酶链反应（RT-PCR）技术检测了90例ALL患者DNA Topo的表达。结果 DNA Topo各亚型（Topo-Ⅰ,Topo-Ⅱa,Topo-Ⅱb）的表达阳性率初治组（58.1 %,51.2 %,81.5 %）高于复发难治组（33.3 %,44.4 %,77.9 %）和完全缓解（CR）组（14.9 %,23.4 %,34.1 %）,各组比较差异均有统计学意义（P＜0.05）。表达量各组间比较,CR组与初治组差异有统计学意义（P＜0.005）;CR组与复发难治组Topo-Ⅱb差异有统计学意义（P＜0.05）,DNA To各亚型表达量之间有显著相关性（P＜0.001）,且各亚型表达量与WBC数之间亦有显著相关性（P＜0.01）。结论 ALL患者DNA Topo各亚型mRNA水平的表达量可能与WBC数共同作为Topo抑制剂药物个体化合理用药的参考指标,但不宜作为判断患者是否对Topo抑制剂耐药的参考指标。     

急性白血病患者Topo Ⅱα和DNA-PKcs的表达与多药耐药的关系

目的:探讨拓扑异构酶Ⅱα(TopoⅡα)和DNA依赖蛋白激酶催化亚单位(DNA-PKcs)在急性白血病(AL)患者中的表达及其与多药耐药的关系.方法:采用免疫组织化学SP法检测62例AL患者骨髓白血病细胞TopoⅡα和DNA-PKcs的表达.结果:1)TopoⅡα在耐药组和敏感组中阳性表达率分别为33.3%和69.0%,耐药组TopoⅡα阳性表达率明显低于敏感组(P＜0.01).2)DNA-PKcs在耐药组和敏感组中的阳性表达率分别为51.5%和20.7%,耐药组DNA-PKcs阳性表达率明显高于敏感组(P＜0.05).3)在TopoⅡα阳性表达的患者中,DNA-PKcs阳性表达组耐药率(61.5%)明显高于DNA-PKcs阴性表达组(16.7%)(P＜0.05).在DNA-PKcs阴性表达的患者中,TopoⅡα阴性表达组耐药率(61.9%)明显高于TopoⅡα阳性表达组(16.7%)(P＜0.01).TopoⅡα阳性表达DNA-PKcs阴性表达组耐药率最低(16.7%),而TopoⅡα阴性表达DNA-PKcs阳性表达组耐药率最高(90.0%)(P＜0.001).TopoⅡα和DNA-PKcs两者表达之间无相关性.结论:AL患者TopoⅡα表达水平下降,DNA-PKcs表达水平升高与临床耐药密切相关,联合检测TopoⅡα和DNA-PKcs对临床耐药和预后的判断有一定价值.     

修复基因XRCC1和XPD单核苷酸多态与急性白血病关联性的研究现状

目的:总结国内外关于X线修复交叉互补基因(XRCC1)和着色性干皮病基因(XPD)单核苷酸多态与急性白血病关联性研究现状。方法:以"DNA修复、XRCC1、XPD、基因多态性和白血病"为关键词检索1991-12-2010-05 CNKI和Pubmed数据库。纳入标准:1)XRCC1单核苷酸多态性与急性白血病的相关性;2)XPD单核苷酸多态性与急性白血病的相关性;3)DNA修复基因多态性对修复能力的影响。根据纳入标准分析25篇文献。结果:XRCC1和XPD蛋白分别是碱基切除修复和核苷酸切除修复中关键酶,编码区多态性通过改变其编码蛋白的结构或功能,影响DNA损伤的修复效率,导致基因组不稳定和白血病的发生发展。研究发现,XRCC1 Arg399Gln多态与儿童急性淋巴细胞白血病(ALL)易感性明显相关,399Gln突变基因型儿童ALL发病风险是399Lys野生型的2.2~2.4倍;XPD751Gln突变降低急性髓系白血病(AML)患者无病生存期(DFS)及生存率(OS),且增加治疗相关白血病危险性。结论:XRCC1和XPD单核苷酸多态性可能是急性白血病遗传易感性及预后异质性的重要基础。     

单纯疱疹病毒Ⅱ型与白血病的相关性研究

小鼠白血病可由C型病毒引起早已得到证实。在本实验中用C型病毒接种小鼠以后其白血病的发生率是41.02%,用HSV—2(333)接种的小鼠以及对照组的小鼠均未发生白血病。当用了C型病毒与HSV—2(333)共同接种小鼠以后其白血病的发病率高达79.16%。它与单独接种了C型病毒的小鼠白血病发病率相比较,在统计学上具有高度显著性差异(P<0.01)。实验结果表明HSV—2(333)对小鼠无致白血病作用,可是它对C型病毒诱发小鼠白血病具有促进作用。     

脑胶质瘤的恶性增殖与DNA拓扑异构酶Ⅱα的表达研究

目的通过观察DNA拓扑异构酶Ⅱα(TopoⅡα)在不同级别脑胶质瘤中表达,研究TopoⅡα表达与脑胶质瘤分化程度的关系.方法应用免疫组化二步法对59例脑胶质瘤标本及5例正常脑组织中TopoⅡα的表达进行对照研究.结果随着脑胶质瘤病理级别的升高,TopoⅡα标记指数也升高,低度恶性组与中、高度恶性组TopoⅡα表达差异均有显著性(P＜0.05),而中度恶性和高度恶性组间差异无显著性(P＞0.05).结论 TopoⅡα能较准确地反映脑胶质瘤增殖潜能和恶性程度,对判断脑胶质瘤患者的预后有参考价值.     

拓扑异构酶I抑制剂对K562细胞的杀伤与诱导凋亡作用

背景与目的:近年发现,拓扑异构酶Ⅰ抑制剂对加速期或急变期的慢性髓细胞白血病有较好疗效。为了深入理解拓扑异构酶Ⅰ抑制剂这一新的药理作用,本研究采用具有慢性髓细胞白血病特征性异常染色体犤t(9;22)犦的K562细胞株为实验对象,进一步探讨拓扑异构酶Ⅰ抑制剂拓扑替康(topotecan)对靶细胞的杀伤与诱导凋亡活性。方法:采用MTT法测定拓扑替康对K562细胞的杀伤作用;通过形态学与AnnexinVFITC染色,研究拓扑替康对靶细胞的促凋亡活性;采用caspase-8特异性抑制剂IETD-fmk,分析拓扑替康介导的细胞杀伤或凋亡和caspase活化的关系。结果:经0.15μmol/L拓扑替康处理至12、24、48及72h时,K562细胞的存活率与对照相比,逐渐降至(92±36)%犤P>0.05vs(94±27)%犦、(68±21)%犤P<0.05vs(119±13)%犦、(54±15)%犤P<0.05vs(132±31)%犦及(21±10)%犤P<0.01vs(114±19)%犦;同时,靶细胞出现磷脂酰丝氨酸外翻、细胞固缩、染色质边集、核碎裂,最终解离为大量凋亡小体;经caspase-8抑制剂与拓扑替康联合处理至24、48h时,K562细胞的存活率依然维持在(95±29)%与(87±11)%,后者显著高于单用拓扑替康者犤P<0.05vs(54±15)%犦,且无明确的凋亡小体形成。结论:拓扑异构酶Ⅰ抑制剂拓扑替康对K562细胞具有较强的杀伤活性与诱导凋亡作用     

Maternal prenatal intake of one-carbon metabolism nutrients and risk of childhood leukemia

Purpose

Folate, vitamins B12 and B6, riboflavin, and methionine are critical nutrients for the one-carbon metabolism cycle involved in DNA synthesis and epigenetic processes. We examined the association between maternal intake of these nutrients before pregnancy and risk of childhood acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) in a matched case–control study.

Methods

Maternal dietary intake and vitamin supplement use in the year before pregnancy was assessed by food frequency questionnaire for 681 ALL cases, 103 AML cases, and 1076 controls. Principal component analysis was used to construct a variable representing combined nutrient intake, and conditional logistic regression estimated the odds ratio (OR) and 95% confidence interval (CI) for the association of ALL and AML with the principal component and each nutrient.

Results

Higher maternal intake of one-carbon metabolism nutrients from food and supplements combined was associated with reduced risk of ALL (OR for one-unit change in the principal component = 0.91, CI 0.84–0.99) and possibly AML (OR for the principal component = 0.83, CI 0.66–1.04). When analyzed separately, intake of supplements high in these nutrients was associated with a reduced risk of ALL in children of Hispanic women only.

Conclusions

In conclusion, these data suggest that higher maternal intake of one-carbon metabolism nutrients may reduce risk of childhood leukemia.

     

Maternal and perinatal risk factors for childhood leukemia

This report describes an exploratory population-based study of maternal and perinatal risk factors for childhood leukemia in Sweden. The Swedish National Cancer Registry ascertained 411 cases in successive birth cohorts from 1973 through 1984 recorded in the Swedish Medical Birth Registry. Using the latter, we matched five controls without cancer to each case by sex and month and year of birth. Mothers of children with leukemia were more likely to have been exposed to nitrous oxide anesthesia during delivery than mothers of controls [odds ratio (OR) = 1.3; 95% confidence interval (CI) = 1.0, 1.6]. Children with leukemia were more likely than controls to have Down's syndrome (OR = 32.5; 95% CI = 7.3, 144.0) or cleft lip or cleft palate (OR = 5.0; 95% CI = 1.0, 24.8); to have had a diagnosis associated with difficult labor but unspecified complications (OR = 4.5; 95% CI = 1.1, 18.2) or with other conditions of the fetus or newborn (OR = 1.5; 95% CI = 1.1, 2.1), specifically, uncomplicated physiological jaundice (OR = 1.9; 95% CI = 1.2, 2.9); or to have received supplemental oxygen (OR = 2.6; 95% CI = 1.3, 1.3, 4.9). Because multiple potential risk factors were analyzed in this study, future studies need to check these findings. We did not confirm the previously reported higher risks for childhood leukemia associated with being male, having a high birth weight, or being born to a woman of advanced maternal age.     

Maternal diet and infant leukemia: the DNA topoisomerase II inhibitor hypothesis: a report from the children's oncology group.

BACKGROUND: The MLL 11q23 translocation arises in utero and is present in 75% of infant leukemias. That MLL+ acute myeloid leukemia (AML) can arise following chemotherapy with DNA topoisomerase II (DNAt2) inhibitors suggests that these substances, which also occur naturally in foods, may contribute toward infant leukemia. We hypothesized that maternal consumption of dietary DNAt2 inhibitors during pregnancy would increase the risk of infant leukemia, particularly AML(MLL+). METHODS: This Children's Oncology Group case-control study consisted of 240 incident cases of infant acute leukemia [AML and acute lymphoblastic leukemia (ALL)] diagnosed during 1996 to 2002 and 255 random digit dialed controls. Maternal diet during pregnancy was determined through a food frequency questionnaire. An index of specific foods identified a priori to contain DNAt2 inhibitors as well as vegetables and fruits were created and analyzed using unconditional logistic regression. RESULTS: There was little evidence of an association between the specific DNAt2 index and leukemia overall and by subtype. An exception was AML(MLL+); odds ratios (95% confidence intervals) comparing the second to fourth quartiles to the first were 1.9 (0.5-7.0), 2.1 (0.6-7.7), and 3.2 (0.9-11.9), respectively (P for trend = 0.10). For the vegetable and fruit index, there were significant or near-significant inverse linear trends for all leukemias combined, ALL(MLL+), and AML(MLL-). CONCLUSION: Overall, maternal consumption of fresh vegetables and fruits during pregnancy was associated with a decreased risk of infant leukemia, particularly MLL+. However, for AML(MLL+) cases, maternal consumption of specific DNAt2 inhibitors seemed to increase risk. Although based on small numbers, these data provide some support for distinct etiologic pathways in infant leukemia.     

Environmental and genetic susceptibility to MLL-defined infant leukemia

The study of rare cancers, including retinoblastoma, angiosarcoma, and vaginal clear cell carcinoma, has contributed greatly to our understanding of cancer mechanisms. Infants with leukemia may represent another important rare group. The majority of infants with leukemia have MLL gene rearrangements in their leukemia cells, and there is unequivocal laboratory evidence that these arise in utero. There is increasing evidence that environmental and genetic factors may contribute to the risk of MLL-defined infant leukemias. Because the infant exposure experience is only a small window in comparison to that of an individual who develops a malignancy in middle or late age, the pivotal factors responsible for this genetic anomaly may be easier to identify. With the largest case-control study of infant leukemia ever conducted underway in the Children's Oncology Group (COG AE24), there is a unique opportunity to integrate epidemiological data with laboratory data on MLL status and genotype.     

Maternal diet and acute lymphoblastic leukemia in young children.

Because leukemia clone-specific chromosomal abnormalities are present at birth in children who later develop leukemia, it has been hypothesized that maternal factors, including nutrition during pregnancy, might affect the risk of acute lymphoblastic leukemia (ALL) among young children. We have evaluated this hypothesis in a nationwide case-control study of ALL among children ages 12 to 59 months in Greece. Children (n=131) with ALL were gender and age matched to control children (n=131) hospitalized for minor conditions between 1999 and 2003. The mothers of the children were interviewed in person by trained interviewers who used an extensive food frequency questionnaire addressing diet during the index pregnancy. The analysis was done by modeling the data through conditional logistic regression, also controlling for total energy intake and possible confounding factors. Odds ratios (OR) and 95% confidence intervals (95% CI) were expressed per quintile increase of maternal intake during pregnancy of the specified food group. The risk of ALL in the offspring was lower with increased maternal intake of fruits (OR, 0.72; 95% CI, 0.57-0.91), vegetables (OR, 0.76; 95% CI, 0.60-0.95), and fish and seafood (OR, 0.72; 95% CI, 0.59-0.89) and higher with increased maternal intake of sugars and syrups (OR, 1.32; 95% CI, 1.05-1.67) and meat and meat products (OR, 1.25; 95% CI, 1.00-1.57). Children of women who tend to consume during their pregnancies what is currently considered to be a healthy diet maybe at lower risk of ALL.     

Phenotypic and genotypic heterogeneity in infant acute leukemia. I. Acute lymphoblastic leukemia

We have studied the immunophenotypic and genotypic features in 35 infants aged less than 1 year with acute lymphoblastic leukemia (ALL) or acute undifferentiated leukemia (AUL). A CD10 (common ALL antigen)-negative, CD19-positive pre-pre-B ALL phenotype was observed in 24 infants. Seventeen of them had blast cells coexpressing myeloid-associated markers such as CD15A (VIM-D5, MZ17) and/or VIM-2, but neither myeloperoxidase nor platelet peroxidase was detected in five of these cases analyzed by electron microscopy. Five patients showed a typical common ALL, five a pre-B ALL phenotype, and one infant was unclassifiable by surface-marker and morphologic analysis. Cytogenetic data, available in 21 of these patients, revealed chromosomal abnormalities involving 11q23 in 10 infants with a CD10-negative pre-pre-B ALL. Immunoglobulin (Ig) and T cell receptor (TCR) gamma, beta and delta gene analysis of 31 infants showed Ig heavy-chain gene rearrangement in all but one patient with evidence for clonal evolution in six and kappa-light-chain rearrangement in three infants. TCR beta-chain and TCR gamma-chain rearrangement occurred in six and five patients respectively, while TCR delta-chain rearrangement was identified in 15 patients. Our data indicate that ALL in infancy may present with heterogeneous immunophenotypic and genotypic features. The high frequency of coexpression of B-lineage and myeloid surface markers as well as of chromosomal rearrangement involving 11q23 suggests that the clonogenic cell of infant ALL may relate to a multipotent progenitor cell in most cases.     

Phenotypic and genotypic heterogeneity in infant acute leukemia. II. Acute nonlymphoblastic leukemia

We have studied the immunophenotypic and genotypic characteristic of acute nonlymphoblastic leukemias (ANLL) in infants aged less than one year. Sixty-four percent of cases (16/25) showed a myeloid or myelomonocytic differentiation pattern and 10 of these were classified as FAB M5 (7 M5a, 3 M5b). Only seven of the latter cases expressed the CD14 antigen. Acute megakaryocytic leukemia with a high number of glycoprotein IIb/IIIa or IIIa positive blasts were identified in five patients. Erythroleukemia with a high percentage of rather mature glycophorin A positive erythroblasts were diagnosed in two infants. Cytogenetic studies were successfully performed in all 20 cases investigated. Abnormalities involving chromosome 11 were present in 10 of 17 patients with an abnormal karyotype including five cases with a t(9;11)(p21;q23). Immunoglobulin (Ig) and T cell receptor (TCR) gene analyses were performed in 20 patients. A rearrangement of Ig heavy chain sequences was detected in five cases (20%), one of whom exhibited multiple rearranged fragments. Three of these patients showed additional TCR delta-chain gene rearrangements, while Ig kappa, TCR beta- as well as TCR gamma-chain genes showed a germline configuration in all cases analyzed. Our study confirms the high incidence of myelomonocytic and monoblastic subtypes in infants with ANLL, which are particularly closely associated with chromosome 11 abnormalities. However, we also observed an unexpected high frequency of megakaryoblastic leukemias as well as erythroleukemias. As previously reported for ALL in infants, ANLL of infancy shows a similar heterogeneity regarding phenotypic and genotypic features.     

Maternal exposure to potential inhibitors of DNA topoisomerase II and infant leukemia (United States): A report from the Children's Cancer Group

Nearly 80 percent of infant leukemias present with an abnormality involving the MLL gene at 11q23. Moreover, secondary acute myeloid leukemias (AML) that occur as the result of chemotherapy agents, which are known to inhibit DNA topoisomerase II, often manifest the same MLL abnormalities. It has been hypothesized that de novo infant leukemias may occur as a result of maternal exposure to agents in diet and medications that inhibit DNA topoisomerase II. Three epidemiologic studies of childhood leukemia with similar methodologies were conducted in the United States and Canada over the past 10 years by the Children's Cancer Group (CCG). Of the total 771 mothers of infants diagnosed at one year of age or less (<12.5 months) who originally were interviewed (303 infant cases and 468 matched controls) across the three studies, follow-up questionnaire data on maternal exposure to potential DNA topoisomerase II inhibitors during pregnancy were available on 84 cases and 97 matched controls in the US. For maternal diet, a composite variable was created that consisted of 10 foods identified a priori as containing DNA topoisomerase II inhibitors. There were no significant trends with increasing maternal consumption for either the overall group, or the acute lymphoblastic leukemia (ALL) stratum. However, within the AML stratum, there was a statistically significant positive association (P trend=0.04) with increasing consumption of DNA topoisomerase II-inhibitor containing foods (odds ratio [OR]=9.8, 95 percent confidence interval [CI]=1.1–84.8; OR=10.2, CI=1.1–96.4; for medium and high consumption, respectively). Other potential topoisomerase II inhibitors were explored; no significant findings were found. Results of this preliminary study, in combination with molecular data, should be used in future investigations of childhood leukemia (particularly, infant) to justify the incorporation of a detailed dietary history.Drs Ross and Robison are with the Division of Pediatric Epidemiology and Clinical Research, University of Minnesota, Minneapolis, MN, USA. Dr Potter is with the Cancer Prevention Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA, USA. Dr Reaman is with the Department of Pediatric Hematology-Oncology, Children's National Medical Center, Washington, DC. Dr Pendergrass is with the Department of Pediatric Hematology-Oncology, Children's Hospital and Medical Center, Seattle, WA. Address correspondence to Dr Ross, Children's Cancer Group, P.O. Box 60012, Arcadia, CA 91066-6012, USA. This research was supported in part by the University of Minnesota Children's Cancer Research Fund, NIH training grant T32 09607, and NCI grants CA42479, CA49450, CA58051 from the United States Department of Health and Human Services. Participating Children's Cancer Group investigators, institutions, and grant numbers (Division of Cancer Treatment, National Cancer Institute) are provided in the appendix.     

Alcohol intake and incidence of de novo adult acute leukemia

In a case-control study of adult acute leukemia we defined alcohol intake as either non-regular (<1 drink per week), light (1–5 drinks per week), moderate (6–8 drinks per week) or heavy (>8 drinks per week). An inverse association was found for light and moderate beer intake (RR = 0.58; 95% CI: 0.44, 0.76). In contrast, a positive association was found for moderate and heavy wine intake (RR = 2.1; 95% CI: 1.2, 3.8). Divergent results might reflect the effect of different nutrients in beer and wine, unmeasured confounding, or differing impacts of selection bias on these associations.     

Maternal reproductive history and birth characteristics in childhood acute lymphoblastic leukemia

Using birth-registration data, a case-control study was done to investigate the possible associations of childhood acute lymphoblastic leukemia (ALL) with birth characteristics and maternal reproductive history. The data included cases born and diagnosed in Minnesota since 1969. Matched analyses were conducted using 337 cases and 1336 birth year-matched controls. There was a statistically significant increased odds of ALL for birth to older (greater than 35 years) mothers (odds ratio (OR) = 2.14, 95% confidence interval (CI) = 1.28, 3.58), older fathers (OR = 1.62, 95% CI = 1.14, 2.30), mothers with at least a high school education (OR = 1.61, 95% CI = 1.05, 2.48), and larger intervals (greater than 5 years) between the birth of the proband and the preceding sibling (OR = 1.86, 95% CI = 1.12, 3.09). The increased odds of ALL for birth by Caesarean section approached significance (OR = 1.42, P = 0.06). No overall association was found for: gender, race, paternal education, fetal-loss history, birth order, prenatal care history, pregnancy complications, inducement of labor, multiple birth, gestational age, or birth weight. Age at diagnosis was an important effect modifier of some analyses. For cases diagnosed before age 2 years, there was a 2.7-fold increased odds of ALL if the last pregnancy had resulted in a fetal loss (P = 0.03). For cases diagnosed before age 4 years, birth weight greater than 3800 g was associated with a significant 2.05-fold increased odds of ALL. These data strengthen the hypothesis that prenatal events may play a causative role in childhood ALL, particularly in those cases diagnosed at a younger age.