Carbon ion irradiation-induced DNA damage evokes cell cycle arrest and apoptosis via the pRb/E2F1/c-Myc signaling pathway in p53-deficient prostate cancer PC-3 cells

Carbon ion radiotherapy has the advantages of better therapeutic effect and fewer side effects compared with those of X-rays in many kinds of tumors,including prostate cancer,and thus is an attractive treatment approach for prostate cancer.However,the biological effects and underlying mechanisms of carbon ion irradiation in prostate cancer are not yet fully understood.Therefore,this study systematically compared the effects of carbon ion irradiation with those of X-ray irradiation on DNA damage response and found that carbon ion irradiation was more effective than X-ray irradiation.Carbon ion irradiation can induce a high level of DNA double-strand break damage,reflected by the number of y-H2 A histone family member X foci,as well as by the foci lasting time and size.Moreover,carbon ion irradiation exhibited strong and long-lasting inhibitory effect on cell survival capability,induced prolonged cell cycle arrest,and increased apoptosis in PC-3 cells.As an underlying mechanism,we speculated that carbon ion irradiation-induced DNA damage evokes cell cycle arrest and apoptosis via the pRb/E2 F1/c-Myc signaling pathway to enhance the radiosensitivity of p53-deficient prostate cancer PC-3 cells.Collectively,the present study suggests that carbon ion irradiation is more efficient than X-ray irradiation and may help to understand the effects of different radiation qualities on the survival potential of p53-deficient prostate cancer cells.

Dose-dependent effects of lead on cell-cycle arrest, DNA damage, and cyclin D1 expression in primary cultured rat hippocampal neurons

BACKGROUND： Previous studies have suggested that the hippocampus is one of the neurotoxic target sites for lead. However, the molecular mechanisms of action, including the effect of lead on cell-cycle arrest, remain poorly understood. OBJECTIVE： To investigate the effects of different lead concentrations on cell-cycle arrest, DNA damage, and cyclin D1 expression in primary cultured rat hippocampal neurons. DESIGN, TIME AND SETTING： A randomized, controlled, in vitro experiment was performed at the China Medical University between July 2008 and May 2009. MATERIALS： Antibodies specific to cyclin D1 and actin were synthesized and purified by Santa Cruz Biotechnology, USA. FACStar flow cytometer was purchased from Becton Dickinson, San Jose, California, USA. METHODS： Wistar rat hippocampal neurons were primary cultured for 7 days. Neurons in the control group were treated with 0.01 mol/L phosphate buffered saline. Neurons in the 0.2, 1.0, and 10 umol/L lead acetate groups were subjected to 0.2, 1.0, and 10 umol/L lead acetate. Subsequently hippocampal neurons in each group were cultured for 24 hours. MAIN OUTCOME MEASURES： The effects of lead on cell cycle were measured by flow cytometry, DNA damage was measured using the comet assay, and cyclin D1 expression was measured using Western blot analysis. RESULTS： Treatment of hippocampal neurons with 0.2 umol/L lead acetate did not significantly alter cell cycle phase distribution, i.e., sub-G1, S, G0/G1, G2/M, whereas treatment with 1.0 and 10 umol/L lead acetate significantly increased the percentage of S and sub-G1 phase cells （P 〈 0.05）. Olive tail moment in all lead-treated groups and the percentage of DNA in the tail in 1.0 umol/L and 10 umol/L lead acetate groups were significantly greater compared with the control group （P 〈 0.05）. In addition, the percentage of tail DNA was greater in the 0.2 umol/L lead acetate group compared with the control group （P 〉 0.05）. Following incubation with 0.2, 1.0, and 10 umol/L lead acetate for 24 hours, cyclin D1 expression gradually decreased with exposure to increasing lead acetate concentrations （1.0-10 umol/L）. CONCLUSION： Lead exposure to primary cultured rat hippocampal neurons resulted in dose-dependently disturbed cellular homeostasis, including DNA damage, reduced cyclin D1 expression, and stagnation of cell-cycle progression.

Functional role of ATM in the cellular response to DNA damage

Ataxia-telangiectasia mutated(ATM)plays a key role in regulating the cellular response to ionizing radiation.The tumor-suppressor gene ATM,mutations in which cause the human genetic disease ataxia telangiecta-sia,encodes a key protein kinase that controls the cellular response to double-stranded breaks.Activation of ATM results in phosphorylation of many downstream targets that modulate numerous damage response pathways,most notably cell cycle checkpoints.Here,we highlight some of the new developments in thefield in our understanding of the mechanism of activation of ATM and its signaling pathways,explore whether DNA double-strand breaks are the sole activators of ATM and ATM-dependent signaling pathways,and address some of the prominent,unanswered questions related to ATM and its function.The scope of this article is to provide a brief overview of the recent literature on this subject and to raise questions that could be addressed in future studies.

DNA损伤与细胞周期调控

Ｄ Ｎ Ａ 损伤和损伤后修复可引起细胞周期阻滞， 这一事件由三个阶段组成： 损伤的识别， 损伤信号的传递以及细胞周期阻滞． 在某些情况，

马兜铃酸Ⅰ致肾小管上皮细胞DNA损伤的逆转性实验

目的:研究探讨马兜铃酸Ⅰ(AAⅠ)对猪肾小管上皮细胞(LLC -PK1细胞)DNA损伤和细胞周期阻滞是否具有可逆性。 方法:采用LLC- PK1细胞为实验对象,选择不同浓度的AAⅠ(80, 320,和1 280ng/ml)体外刺激LLC- PK1细胞24h,然后去除含有AAⅠ的培养基,换不含AAⅠ的培养基继续培养细胞24和48h。同时设不加AAⅠ的细胞为对照组。采用单细胞凝胶电泳(又称彗星实验)检测经不同剂量AAⅠ处理的LLC- PK1细胞不同时间点DNA损伤情况,流式细胞仪技术检测它们对LLC -PK1细胞周期的影响。 结果:AAⅠ(80ng/ml)组细胞彗星实验为阴性,但AAⅠ(320和1 280ng/ml)导致细胞DNA损伤,出现明显的彗星拖尾现象,且细胞在G2 /M期的比例也明显增加,均呈剂量依赖性(P<0. 01 )。用不含AAⅠ的培养基继续培养细胞24和48h后,AAⅠ( 320ng/ml)组彗星拖尾现象明显减轻至消失,G2 /M期细胞的比例与同时间对照组比较无明显差异(P>0 .05 )。而AAⅠ(1280ng/ml)组彗星拖尾现象无明显改善(P<0. 01),G2 /M期细胞的比例仍明显高于同时间正常对照组(P<0 .05)。 结论:AAⅠ可导致LLC- PK1细胞DNA损伤,使细胞周期阻滞在G2 /M期。低剂量AAⅠ造成的DNA损伤可完全恢复,细胞进入正常的细胞周期,但高剂量所致DNA损伤不可逆转。

DNA损伤与肿瘤发生的研究进展

生物体基因组时刻都暴露在体内外各种应激因素的作用下,即使在非常健康的细胞其基因组DNA的完整性也持续受到威胁。DNA在细胞内外各种因素的作用下可不断产生损伤,如体内代谢过程中产生的自由基和其它活性化合物,DNA在复制和重组过程中自发的错误;环境中的紫外线和离子辐射以及一些化学物质均能损伤DNA。细胞能通过周期阻滞修复DNA或者细胞凋亡对DNA损伤产生反应。细胞对DNA损伤反应的异常将导致肿瘤的发生。本文综述当前对DNA损伤修复和凋亡的分子调控以及它与肿瘤发生的研究进展。

ATM、ATR和DNA损伤介导的细胞周期阻滞

ATM和ATR属于PIKK家族,是DNA损伤检查点的主要成员。它们被不同类型的DNA损伤所激活,通过磷酸化相应的下游蛋白Chk1和Chk2等,调节细胞周期各个检查点,引起细胞周期阻滞,使DNA损伤得以修复。ATM和ATR在维持基因组的稳定性中起到至关重要的作用。本文着重综述有关ATM和ATR在DNA损伤介导的细胞周期阻滞中发挥的作用以及相互关系的最新研究进展。

p53非依赖性信号通路在DNA损伤致细胞凋亡中的研究进展

p53在DNA损伤诱导细胞凋亡中发挥关键作用,但p53基因在大多数肿瘤细胞中易发生突变,突变率可超过50%。目前研究发现,p73、p63、Caspase 2、NF-κB等蛋白介导的信号通路能够在p53非依赖的DNA损伤诱导细胞凋亡中发挥作用。因此,有必要对p53非依赖信号通路近年来的研究进展作一综述,为癌症治疗提供新的思路。

虎刺醛对人早幼粒白血病细胞HL-60的生长抑制、周期阻滞、凋亡诱导及DNA损伤作用

利用生长曲线法、流式细胞术、AO/EB双染法及单细胞凝胶电泳法,分别检测了蒽醌化合物虎刺醛对人早幼粒白血病细胞HL-60的生长抑制、细胞周期阻滞、细胞凋亡诱导以及DNA损伤能力.结果表明,2.5～12.5μg.mL-1的虎刺醛对人早幼粒白血病细胞HL-60具有显著的生长抑制作用;不同浓度(5～40μg.mL-1)的虎刺醛,可引起HL-60细胞G1期、S期和G2/M期周期阻滞;在2.5～12.5μg.mL-1浓度范围和24～48h培养时间下,虎刺醛可不同程度诱导HL-60细胞,其凋亡率达到显著水平(P<0.05)或极显著水平(P<0.01),且具有时间和浓度依赖性关系;与对照组相比,药物处理组(5～12.5μg.mL-1)均有极显著性(P<0.01)的彗星率,这表明,该浓度条件下,虎刺醛可较大程度地导致细胞核DNA损伤,这可能是引起周期阻滞进而抑制细胞增殖,最终导致细胞凋亡的原因.

新型化合物XN4抑制急性粒细胞白血病细胞增殖与其诱导氧化性的DNA损伤的关系

目的研究XN4在体外抑制急性粒细胞白血病细胞(AML)增殖的作用与诱导DNA损伤的关系。方法 MTT法检测XN4对AML细胞增殖抑制作用;流式细胞术检测AML细胞反应性氧自由基(ROS)、DNA损伤、细胞周期和细胞凋亡;Western blot探讨XN4对相关蛋白表达的影响。结果 XN4明显抑制AML细胞增殖,半数抑制率(IC50)分别为(2.79±0.15)μmol·L-1和(2.76±0.20)μmol·L-1;XN4增加细胞ROS水平和r-H2AX的表达,诱导细胞阻滞在S期并增加细胞凋亡率;XN4能增加H2AX、ATM的磷酸化以及Parp和Caspase-3的切割,而减少CDK2和Cyclin E1的表达。结论 XN4通过激活ROS,诱导DNA的损伤和细胞周期S期阻滞,抑制DNA损伤修复和诱导细胞的凋亡,抑制HL-60及KG1α细胞的增殖,抗氧化剂NAC(N-乙酰半胱氨酸)能减少ROS的产生逆转XN4的作用。

HeLa细胞中hR24L基因的表达、DNA损伤修复、G_2/M阻滞与电离辐射之间的关系(简报)

DNA是生命活动中最重要的遗传物质,保持其分子结构的完整性对于细胞至关重要,因此研究DNA损伤修复是生命科学的重要课题之一.基因组比较简单,易于操作的单细胞真核生物酵母遂成为研究DNA损伤修复的重要材料.对紫外线或电离辐射敏感的酵母突变株称为rad突变株.酵母细胞的基因组中有近30个遗传位点与辐射抗性有关.根据单突变和双突变的敏感特征所得出的上位关系可将其分为3个上位显性组[1,2]:RAD3组,该组成员参与核苷酸的切除修复,其突变株对紫外线敏感;RAD6组,参与复制后修复,其突变株对化学诱变剂敏感;RAD52组,参与重组修复(包括链断裂修复),其突变株对电离辐射敏感.RAD24基因属于RAD3组,兼有其他组的某些特性.

胞外信号调节激酶促进DNA损伤反应的作用机制

机体在长期进化中拥有一整套DNA损伤反应(DNA damage response,DDR)系统来保证基因组的完整性,其中最重要的就是通过激活检验点以阻止细胞周期进程,并修复损伤的DNA。细胞外信号调节激酶(extracellular signal-regulated kinases,ERK)/丝裂原活化蛋白激酶(mitogen-activated protein kinase,MAPK)通路是经典的细胞信号转导通路,具有调节细胞增殖、分化、凋亡等多种功能,二者的功能性联系都能调节细胞增殖。本综述旨在阐述ERK激酶在DNA损伤反应中的作用。

Polo样激酶1抑制剂Rigosertib对细胞放射损伤的防护作用

DNA双链断裂是电离辐射诱发最严重DNA损伤,能启动细胞周期阻滞、修复和死亡系列信号反应,其中周期阻滞是DNA损伤应答的重要过程,为DNA损伤修复提供了充足的时间。周期蛋白依赖性激酶4/6(cyclin-dependent kinase 4/6,CDK4/6)、周期蛋白依赖性激酶1(cyclin-dependent kinase1,CDK1)和Polo样激酶1(Polo-like kinase 1,PLK1)等是细胞周期调控关键激酶,其抑制剂可以阻滞细胞周期进程,是否具有细胞放射防护作用有待进一步探究。本文选择人宫颈癌细胞HeLa、人正常乳腺细胞MCF-10A以及人脐静脉上皮细胞HUVEC为研究对象,研究比较了PLK1抑制剂Rigosertib、Volasertib,CDK4/6抑制剂Palbocilib,CDK1抑制剂Ro-3306的辐射防护作用。流式细胞术检测表明,Rigosertib、Volasertib、Ro-3306将细胞阻滞于G 2期(P<0.05,P<0.01或P<0.001),Palbocilib将细胞阻滞于G 1期(P<0.05,P<0.01或P<0.001)。免疫荧光检测结果显示,Rigosertib、Volasertib、Ro-330可显著减少γ射线照射后γH2AX foci数目(P<0.001),表明上述药物可促进DNA修复。HR和NHEJ报告系统证实,Rigosertib、Ro-3306同时通过同源重组和非同源末端连接2种修复途径提高DNA修复效率(P<0.05或P<0.001),Palbocilib、Volasertib能提高HR修复效率(P<0.01)。从上述结果优选出PLK1抑制剂Rigosertib进行深入研究,发现Rigosertib可显著降低辐射诱导的细胞凋亡(P<0.05或P<0.01)。CCK-8和克隆形成实验证实,Rigosertib促进受照后细胞的增殖与存活率(P<0.05,P<0.01或P<0.001)。综上所述,我们分析比较了Rigosertib、Volasertib、Palbocilib、Ro-3306四种药物对细胞放射敏感性的影响,其中Rigosertib保护细胞免受辐射损伤最为显著,为放射损伤防护药物的研发提供了新的技术路径和实验依据。

DNA损伤后细胞凋亡与周期停滞中Δ40P53的作用

目的探讨HCT116p53-/-细胞Δ40P53在脱氧核糖核酸(DNA)损伤时细胞凋亡和细胞周期停滞中的作用,明确Δ40P53与野生型P53的不同作用。方法荧光素酶报告基因和免疫印迹法检测Δ40P53在DNA损伤后转录活性和表达情况,流式细胞技术检测DNA损伤后细胞周期停滞情况,乳酸脱氢酶(LDH)检测分析DNA损伤后细胞凋亡情况,分析Δ40P53的生物学功能。结果 HCT116p53+/+细胞中bax和p21基因的启动子活性在甲烷磺酸甲酯(MMS)刺激时比无MMS刺激时高3～5倍,HCT116p53-/-细胞中bax和p21基因的启动子活性在有无MMS刺激时无显著不同;免疫印迹表明有和无MMS刺激的细胞Δ40P53保持在较高水平,野生型P53经MMS刺激过度表达;LDH法检测50μg/ml的MMS刺激后52.2%的HCT116p53+/+细胞凋亡,而只有32.5%的HCT116p53-/-细胞凋亡,差异有统计学意义(t=84.2,P<0.05);流式细胞仪检测MMS处理后88%的HCT116p53-/-细胞进入G2/S期细胞,66%的HCT116p53+/+细胞进入G2/S期细胞。结论经MMS刺激的HCT116p53-/-细胞的Δ40P53不能诱导细胞凋亡和细胞周期阻滞。

Epigenetic Enabled Normal Human Cells, Lead to <i>First Cell</i>’s Unique Division System, Driving Tumorigenesis Evolution

Normal cells must become cancer-enabling before anything else occurs, according to latest literature. The goal in this mini-review is to demonstrate special tetraploidy in the enabling process. This we have shown from genomic damage, DDR (DNA Damage Response) activity with skip of mitosis leading to diploid G2 cells at the G1 border in need of chromatin repair for continued cell cycling to the special tetraploid division system. In several studies specific methylation transferase genes were activated in normal human cells in tissue fields, containing different cell growth stages of the cancerous process. Histology studies, in addition to molecular chemistry for identification of oncogenic mutational change, were a welcome change (see below). In a study on melanoma origin, DDR also showed arrested diploid cells regaining cycling from methylation transferase activity with causation of 2n melanocytes transforming to 4n melanoblasts, giving rise to epigenetic tumorigenesis enabled First Cells. Such First Cells were from Barrett’s esophagus shown to have inherited the unique division system from 4n diplochromosomal cells, first described in mouse ascites cancer cells (below). We discovered that the large nucleus prior to chromosomal division turned 90° relative to the cytoskeleton axis, and divided genome reductive to diploid, First Cells, in a perpendicular orientation to the surrounding normal cells they had originated from. This unique division system was herein shown to occur at metastasis stage, implying activity throughout the cancerous evolution. Another study showed 4-chromatid tetraploidy in development to B-cell lymphoma, and that such cancer cells also proliferated with participation of this unusual division system. Such participation has long been known from Bloom’s inherited syndrome with repair chiasmas between the four chromatids, also an in vitro observation by us. Our cytogenetic approach also revealed that they believed mitotic division in cancer cells is wrong because such cell divisions were found to be from an adaptation between amitosis and mitosis, called amitotic-mitosis. Amitosis means division without centrosomes, which has long been known from oral cancer cells, in that MOTCs (microtubule organizing center) were lacking centrioles. This observation calls for re-introduction of karyotype and cell division studies in cancer cell proliferation. It has high probability of contributing novel approaches to cancer control from screening of drugs against the amitotic-mitotic division apparatus.

新生霉素通过诱导DNA损伤抑制慢粒白血病细胞增殖

目的研究新生霉素(novobiocin,Nov)在体外抑制慢粒白血病(CML)细胞增殖作用与诱导DNA损伤的关系。方法MTT及羟基荧光素二醋酸盐琥珀酰亚胺脂(CFSE)染色法检测Nov对CML细胞增殖的影响;流式细胞术检测CML细胞反应性氧自由基(ROS)含量、DNA损伤数量、细胞周期阻滞情况和细胞凋亡的比例;Western blot探讨Nov对DNA损伤、细胞周期和细胞凋亡调控通路相关蛋白表达的影响。结果 Nov明显抑制CML细胞增殖,半数抑制率(IC50)分别为(232.50±0.22)μmol·L-1和(237.10±0.13)μmol·L-1,减少CML细胞的增殖分裂代数;Nov增加细胞ROS水平,诱导细胞阻滞在G2/M期并增加凋亡率,呈剂量依赖关系;Nov增加H2AX、ATM、P53的磷酸化水平以及Parp和Caspase-3的切割,而减少CDC25A和CDC25C的表达。结论Nov通过激活ROS产生,诱导CML细胞DNA的损伤和线粒体途径激活的细胞凋亡。

DNA损伤检验点调控的分子机制

多种因素可以引起DNA损伤而最终导致基因产生错义突变、缺失或错误重组。为确保遗传准确性,细胞形成了复杂的细胞周期监督机制,即细胞周期检验点。其中DNA损伤检验点由许多检验点相关蛋白组成,可以识别损伤的DNA,经复杂的信号转导途径引发蛋白激酶的级联反应,减慢或阻滞细胞周期进程,从而为细胞修复损伤的DNA赢得时间。

低浓度MNNG诱发非DNA损伤依赖的细胞信号通路

目的 :研究基因组 DNA损伤与细胞信号通路激活的关系以及低浓度 N-甲基 - N’-硝基 - N-亚硝基胍(MNNG)对细胞膜表面受体的影响。方法 :采用 ELISA法来检测蛋白激酶 A(PKA)的活性 ,不连续梯度密度离心法完成细胞脱核 ,以及免疫荧光法和激光共聚焦显微镜观察细胞表面受体聚集情况。结果 :0 .2 μmol/ L MNNG能在脱核细胞中引起 PKA活性升高 2 .3倍 ,并可在 5 min内引起 vero细胞表面生长因子受体和肿瘤坏死因子 α受体的聚集 ;在脱核细胞中 ,表面受体聚集现象与在完整细胞中一样。结论 :低浓度 MNNG对 PKA的激活和诱导细胞表面受体聚集均不依赖于基因组 DNA的损伤 ,表明细胞信号转导通路的起源可能位于细胞膜或者细胞质中。

Effects of histone acetylation and DNA methylation on p21^(WAF1)regulation

Cell cycle progression is regulated by interactions between cyclins and cyclin-dependent kinases (CDKs). p21(WAF1) is one of the CIP/KIP family which inhibits CDKs activity. Increased expression of p21(WAF1) may play an important role in the growth arrest induced in transformed cells. Although the stability of the p21( WAF1) mRNA could be altered by different signals, cell differentiation and numerous influencing factors. However, recent studies suggest that two known mechanisms of epigenesis, i.e.gene inactivation by methylation in promoter region and changes to an inactive chromatin by histone deacetylation, seem to be the best candidate mechanisms for inactivation of p21( WAF1). To date, almost no coding region p21(WAF1) mutations have been found in tumor cells, despite extensive screening of hundreds of various tumors. Hypermethylation of the p21(WAF1) promoter region may represent an alternative mechanism by which the p21(WAF1/CIP1) gene can be inactivated. The reduction of cellular DNMT protein levels also induces a corresponding rapid increase in the cell cycle regulator p21(WAF1) protein demonstrating a regulatory link between DNMT and p21(WAF1) which is independent of methylation of DNA. Both histone hyperacetylation and hypoacetylation appear to be important in the carcinoma process, and induction of the p21(WAF1) gene by histone hyperacetylation may be a mechanism by which dietary fiber prevents carcinogenesis. Here, we review the influence of histone acetylation and DNA methylation on p21(WAF1) transcription, and affection of pathways or factors associated such as p 53, E2A, Sp1 as well as several histone deacetylation inhibitors.

S期H1299细胞热损伤后的延迟性DNA双链断裂

目的研究S期细胞热损伤后DNA双链断裂形成规律,以阐明S期细胞热敏感原因,并分析DNA双链断裂延迟性形成的可能机制。方法流式细胞术分析热损伤后细胞周期阻滞;Ed U掺入实验检测DNA复制能力;血清饥饿法同步H1299细胞周期;中性彗星实验动态观察热损伤后DNA双链断裂形成;台盼蓝拒染实验研究热损伤后细胞存活率;蛋白免疫印记实验检测ATM磷酸化及DNA结合RAD18情况。结果流式结果显示H1299细胞经45℃热损伤1 h后S期细胞较未加热组明显增多(P<0.01);热损伤后Ed U阳性率随时间变化趋势同S期比例变化;S期细胞热损伤后需经37℃正常孵育一定时间方可观察到"彗星拖尾"现象,且随着正常孵育时间延长,反映DNA双链断裂的尾力矩值越大;台盼蓝拒染实验显示S期细胞受热后7.5 h内死亡率保持较低水平,之后细胞死亡加速;热损伤后ATM磷酸化先增多后减少,热损伤导致DNA结合RAD18明显减少。结论细胞热损伤后可发生S期阻滞,阻滞期间因复制继续、DNA损伤修复抑制而延迟形成的致死性DNA双链断裂是S期细胞热敏感的可能原因。