1、CHAPTER 14细胞衰老、死亡与癌变,Cell aging,Death and Cancer,1,OUTLINE,14.1 细胞衰老(Cell Aging)14.1.1 衰老的概念14.1.2 细胞的寿限14.1.3 细胞衰老的特征14.1.4 细胞衰老的理论14.2 细胞死亡(Cell Death)14.2.1 程序性细胞死亡的基本特性14.2.2 程序性细胞死亡的机理14.2.3 程序性细胞死亡的生物学意义14.3 癌细胞（Cancer）14.3.1 癌生物学14.3.2 癌的起因：物理和化学致癌物14.3.3 肿瘤发生的遗传学,2,3,14.1 细胞衰老14.1.1 衰老的概念衰老(
2、senescing，aging)是机体在退化时期生理功能下降和紊乱的综合表现,是不可逆的生命过程。细胞的衰老与死亡是新陈代谢的自然现象。机体的衰老与细胞的衰老相关联。现代人类面临着3种衰老：生理性衰老病理性衰老心理性衰老,4,14.1.2 细胞的寿限：,1961年，Hayflick 首次报道了体外培养的人成纤维细胞具有增殖分裂的极限,且分裂能力与个体的年龄有关。来源于胚胎 分裂传代50次后开始死亡来源于成年组织 培养1530代就开始死亡动物体细胞在体外可传代的次数，与物种的寿命有关。,5,体外培养的年轻和老的人成纤维细胞的显微形态,6,物种的寿命与体外培养时细胞传代次数的关系,长寿物种的细胞体
3、外培养的代数比短寿物种的细胞代数多,7,Hayflick界限(Hayflick life span):细胞至少是体外培养细胞的增殖能力不是无限的，而是有一定界限，细胞的衰老控制着细胞的分裂次数,进而控制着细胞的数量。,细胞的寿限：各类细胞本身的寿命差别显著,一般说来,能够保持持续分裂能力的细胞是不容易衰老的。分化程度高又不分裂的细胞寿命是有限的。,8,14.1.3 细胞衰老的特征,细胞内水分减少色素生成和色素颗粒沉积衰老过程中细胞质膜的变化：流动性降低；兴奋性降低；配体受体复合物形成下降衰老过程中线粒体的变化数量减少，体积变大，膜破坏，DNA突变细胞核的变化核膜内折；染色质固缩；端粒缩短细胞骨
4、架的变化蛋白质合成的变化合成速度降低，蛋白定位改变,2024/4/29,9,Morphology,Senescent cells become flattened,enlarged and have increased-galactosidase(-半乳糖苷酶)activityIncreased size of nucleus and nucleoliIncreased number of multinucleated cellsIncreased number of lysosomes,Golgi and cytoplasmic microfilaments,2024/4/29,10,Sen
5、escent cells undergo three phenotypic changes,11,14.1.4 细胞衰老的理论,细胞衰老的线粒体损伤论(Mitochondria ageing)自由基理论：氧自由基(Reactive oxygen species(ROS)细胞衰老的端粒假说(Replicative senescence and telomere shortening)细胞衰老的表观调控:(Epigenetic regulation of senescence)衰老的进化论衰老的突变积聚、互逆多效理论,12,自由基攻击细胞的证据,2024/4/29,13,Replicative s
6、enescence is the progressive shortening of telomeres at chromosome endsCritically short telomeres trigger activation of cell cycle checkpointsPermanent cell cycle growth arrest due to activated cell cycle checkpoints,similar to those activated upon double strand breakageCells metabolically active bu
7、t cannot continue to divide,unlike quiesence 静止,Replicative senescence,2024/4/29,14,In the early embryonic period,cells have a determined length of telomere endings.As organism develops by cell differentiation,cells keep proliferating and during each division,telomeres get shorter because of replica
8、tion mechanism specificity.So nature determined that as organism get older,telomeres get shorter and cell goes to death.,2024/4/29,15,Telomere dysfunction contributes to cancer,2024/4/29,16,Epigenetic Regulation of Senescence,Epigenetics entails the study of the switching on and off of genes during
9、development,cell proliferation,senescence and also by environmental insults.Genome modifications resulting from epigenetic changes appear to play a critical role in the cellular senescene.Scatter experimental evidence suggests that epigenetic changes could also be critical determinants of cellular s
10、enescence and organisms senescence.,2024/4/29,17,Histone deacetylases(HDACs)participate in senescence Elevated HDAC activity appears causally related to cellular senescence,as overexpression of a p300 mutant protein,or treatment with a specific chemical inhibitor of p300,results in irreversible grow
11、th arrest and senescence of normal human cells.,DNA methylationSequential loss of DNA methylation could act as an alternative counting mechanism.A progressive loss of 5-methylcytosine in genomic DNA occurs during serial passage of normal cells in culture.The extent of CpG methylation also decreases
12、during aging of organisms.On the other hand,immortal cell lines maintain constant levels of DNA methylation.,2024/4/29,18,Chromatin remodeling and senescenceGenes in the p53,Rb,and ING(inhibitor of growth)pathways affect cell senescence and are capable of regulating gene expression through chromatin
13、 remodeling.p16INK4a is required for hSNF5 chromatin-remodeler induced cellular senescence in malignant tumor cells PASG,an SNF2 family member,is essential for properly maintaining normal DNA methylation and gene expression patterns.Disruption of PASG leads to accumulation of senescence-associated t
14、umor suppressor genes,and increased senescence-associated galactosidase as well as age-related phenotypes.,2024/4/29,19,Modification of different amino acid residues in histone H3 leads either to activation or repression of transcription.,2024/4/29,20,RNA Degradation and Aging,Model of age-related c
15、hanges in AU-rich elements(ARE)-directed mRNA decay.As cells age,HuR levels decline,shifting the balance to mRNA degradation.Many ARE-mRNAs encoding proteins that contribute to proliferation,thus,decline which contributes to the phenotype of senescence.,2024/4/29,21,The role of genetics in determini
16、ng life-span is complex and paradoxical.Although the heritability of life-span is relatively minor,some genetic variants significantly modify senescence of mammals and invertebrates,with both positive and negative impacts on age-related disorders and life-spans.,The Role of Genetics in Senescence,It
17、 appears certain that DNA mutations and chromosomal abnormalities increase with age in mice and humans,2024/4/29,22,A mutant model mouse is useful for studies of aging.The klotho phenotype(premature aging)is caused by a disruption of the single gene,klotho.,2024/4/29,23,Cellular senescence involved
18、in genetic errors,There is an invariant relationship between life span and the number of random mutations.A number of studies at a number of gene loci have shown that somatic mutations of a variety of types accumulate with age.,Deficient in DNA Repair and Transcription induce Premature Aging in Mice
19、.TTD and XPD,genes for DNA repair and replication.SCIENCE VOL 296 17 MAY 2002,Photograph of a 3-week-old XPA/TTD double-mutant(left),TTD(middle),and XPA(right)mouse.,2024/4/29,24,Evolutionary Theory of Senescence,Aging is a by-product of natural selection due to lack of selective pressure for the po
20、st-reproductive individual.Any individual has a probability to reproduce.It is zero at birth and reaches a peak in young adults.Then,it decreases due to the increased probability of death linked to various external(predators,illnesses,accidents)and internal causes(aging).,25,早老症儿童,26,细胞衰老的分子途径,p19AR
21、F/p53/p21Cip1:p16INK4a/Rb端粒-p53-PGC,CDK inhibitors,Senescence signal,27,Role of p53 in G1 arrest induced by DNA damage,Induction of p21 via p53 activation p21:Cdk inhibitor.inhibit DNA synthesis by interacting with PCNA(a subunit of DNA polymerase),28,Rb蛋白对细胞周期的调节,p16INK4a,2024/4/29,29,Polycomb grou
22、p protein BMI1 has been linked to proliferation,senescence and apoptosis.,30,Telomere-p53-PGC,PGC(perioxisome proliferator-activated receptor gamma coactivator)细胞代谢及线粒体功能的主要调控因子,31,14.2 细胞死亡细胞死亡概念：细胞死亡的一般定义是细胞生命现象不可逆的停止。细胞死亡有两种形式：一种为坏死性死亡，另一种为程序性死亡。,32,14.2.1 程序性细胞死亡及其特性,程序性细胞死亡(programmed cell deat
23、h,PCD),又称细胞凋亡(apoptosis)是指为维持内环境稳定，由基因控制的细胞自主的有序性的死亡，它涉及一系列基因的激活、表达以及调控等的作用，因而是具有生理性和选择性的。Apoptosis：希腊语，是指树叶或花的自然凋落；,33,程序性细胞死亡,34,程序性死亡细胞的形态结构变化,细胞变圆，染色质聚集、分块，胞质皱缩,35,程序性死亡细胞的DNA降解,PCD生化特征：染色质DNA的有控裂解：核DNA在核小体连接处断裂成核小体片段，200bp的倍数,DNA Ladder,36,细胞坏死与程序性细胞死亡,凋亡小体(apoptotic body),37,比较内容程序性细胞死亡细胞坏死质膜不
24、破裂发生破裂细胞核固缩，DNA片段化弥漫性降解细胞质由质膜包围溢出形成凋亡小体细胞破裂成碎片溶酶体的酶增多溶酶体解体蛋白质合成有无基因活动由基因调控无基因调控自吞噬常见缺少线粒体自身吞噬肿胀诱发因素生理性信号强烈刺激信号对个体影响生长、发育、引起炎症生存所必需,细胞坏死与程序性细胞死亡比较,38,14.2.2 程序性细胞死亡的机理,2002年的诺贝尔生理学和医学奖:英国的Brenner、Sulston和美国的Horvitz，用C.elegans 研究了调控器官发育程序性细胞死亡的关键基因及其功能，并进一步在高等哺乳动物中发现了相关功能基因。,Caenorhabditis elegans(C.e
25、legans)雌雄同体,39,程序性细胞死亡的过程死亡激活期(activation phase)：接收death signal死亡执行期(execution phase)：执行一套死亡程序,40,apoptosis related genes in C elegans:,决定死亡的两个基因，即ces-1(ces表示CE细胞存活的调控基因)和ces-2基因执行死亡的4个基因：ced-3、ced-4、ced-9和egl-1基因：“死亡机器”(death machinery)7个与死亡细胞被吞噬细胞所吞噬的基因，即ced-1、ced-2、ced-5、ced-6、ced-7、ced-10和ced-11
26、。ced-9可抵消ced-3和ced-4 的作用，防止细胞被杀死，因此是存活因子;死亡细胞在吞噬体中被降解的基因,细胞凋亡的机理：基因调控作用的结果,41,Apoptotic genes in C.elegans,42,Caspase自杀性蛋白水解酶是天冬氨酸特异性半胱氨酸蛋白酶(cysteine-containing aspartate specific protease)，简称caspase;caspase-3、6、7和8 在FAS/TNF介导的程序性细胞死亡途径中起作用；caspase-9和3 一起参与线粒体中Apaf-I、细胞色素c介导的程序性细胞死亡;在人类，已经鉴定了10种不同的c
27、aspase。,Apoptotic genes in mammalian cells,43,Apoptotic protease cascade in mammalian cells,自杀性蛋白酶家族自我切割,蛋白降解级联,44,执行者caspase在程序性细胞死亡中的作用,45,能够被caspase切割的靶蛋白蛋白激酶核纤层蛋白细胞结构蛋白与DNA修复相关的酶类caspase激活的DNase抑制蛋白,2024/4/29,46,Death receptors:CD95(or Fas)TNFR1(TNF receptor-1)DR4 and DR5.,细胞外信号（The extrinsic de
28、ath pathway）对程序性细胞死亡的激发,47,肿瘤坏死因子（tumor necrosis factor,TNF）,48,细胞内信号（The intrinsic death pathway）对程序性细胞死亡的激发内源信号DNA损伤细胞质中Ca2+浓度过高极度氧胁迫（产生大量的自由基）正控制信号 促进细胞死亡,如细胞色素C，凋亡蛋白酶激活因子（apoptotic protease-activating factor，Apaf）负控制信号抑制细胞死亡，如哺乳动物中的BCL-2和BCL-x蛋白。,49,细胞内源信号激发细胞程序性死亡,50,Apoptosis Regulators and ef
29、fectors,2024/4/29,51,Apoptotic proteins p53,Bax线粒体外膜通透性,2024/4/29,52,Bid,Apoptotic proteins Bcl-2 Family,Bid,2024/4/29,53,Apoptotic proteins Caspase family,2024/4/29,54,Apoptotic proteins IAP family（inhibitor of apoptosis protein),livin,2024/4/29,55,Apoptosis and senescence both are a failsafe(错误消除)mechanisms in cell,Cells respond to a number of potentially oncogenic stimuli by adopting a senescent or apoptosis,suggesting that both are fail-safe mechanisms that protects cells from tumorigenic transformation.,potentially oncogenic stimuli,2024/4/29,
