(优选)第二十章癌基因和抑癌基因课件.ppt

1、Normaltransformed 肿瘤肿瘤是机体在各种致瘤因素的作用下，局部组织的细胞在基因水是机体在各种致瘤因素的作用下，局部组织的细胞在基因水平上失掉了对其生长的正常调控，导致异常增生而形成的新生物。平上失掉了对其生长的正常调控，导致异常增生而形成的新生物。致瘤因素致瘤因素 正常细胞正常细胞 基因改变基因改变 肿瘤细胞肿瘤细胞Development of Cancer Defective cell cycles checkpoints mechanisms allows errors in the cell duplication process to persist into the

2、next generation and can lead to and regulated proliferation and the development of cancer.Two different types of mutations contribute to cancer formation:activating mutations in proto-oncogene and inactivating mutations in tumor suppressor genes.OncogenesStimulate ProliferationInhibit Differentiatio

3、nInhibit ApoptosisTumor Suppressor GenesInhibit ProliferationPromote DifferentiationStimulate Apoptosis一、癌基因的基本概念一、癌基因的基本概念癌基因（癌基因（oncogeneoncogene）是指存在于正常细胞内，是指存在于正常细胞内，与细胞生长发育调控有关的一组结构基因。与细胞生长发育调控有关的一组结构基因。癌基因发生结构异常或表达异常时，可以引起癌基因发生结构异常或表达异常时，可以引起细胞癌变。细胞癌变。癌基因可按其来源不同而分为癌基因可按其来源不同而分为病毒癌基因病毒癌基因（v-v-o

4、nconc）和和细胞癌基因细胞癌基因（c-oncc-onc）。）。Oncogenes were first discovered in certain retroviruses and were later identified as cancer-causing agents in many animals First link between viruses and cancer proposed by Francis Peyton Rous in 1910(Nobel Prize,1966):cell-free extracts from chicken tumors injected

5、into healthy chickens caused new tumors.History of oncogeneRous Peyton：The 1966 Nobel Prize in Physiology or Medicine LTR gag pol env src LTR癌基因癌基因酪氨酸酪氨酸蛋白激酶蛋白激酶Rous Sarcoma Virus(RSV)Discovered by Harold Varmus and Bishop,1975-76(Nobel Prize,1989).A transforming retrovirus:a cancer-causing single-s

6、tranded RNA virus that uses reverse transcriptase enzyme to make ssDNA,then ds DNA,which integrates into host DNA.Note:not all oncogenes caused by viruses.100s of oncogenes now known.Human T-cell leukemia virus(HTLV)is a human RV;codes a TF.Retroviral life cycleFigure 6 Retroviral life cycleRetrovir

7、uses have two identical copies of a plus single-stranded RNA genome and an outer envelope containing protruding viral glycoproteins.After envelope glycoproteins on a virion interact with a specific host-cell membraneprotein or group of proteins,the retroviral envelope fuses directly with the plasma

8、membrane without first undergoing endocytosis(step 1).Following fusion,the nucleocapsid enters the cytoplasm of the cell;then deoxynucleoside triphosphates from the cytosol enter the nucleocapsid,where viral reverse transcriptase and other proteins copy the ssRNA genome of the virus into a dsDNA cop

9、y(step 2).The viral DNA copy is transported into the nucleus(only one host-cell chromosome is depicted)and integrated into one of many possible sites in the host-cell chromosomal DNA(step 3).The integrated viral DNA,referred to as a provirus,is transcribed by the host-cell RNA polymerase,generating

10、mRNAs(light red)and genomic RNA molecules(dark red).The host-cell machinery translates the viral mRNAs into glycoproteins and nucleocapsid proteins(step 4).The latter assemble with genomic RNA to form progeny nucleocapsids,which interact with the membrane-bound viral glycoproteins,.Eventually the ho

11、st-cell membrane buds out and progeny virions are pinched off(step 5).Origin of Transforming Retroviruses病毒癌基因病毒癌基因v-src来源于宿主细胞的来源于宿主细胞的C-SRC基因基因 逆转录逆转录复制复制整合整合转录转录感染感染病毒病毒RNARNA-DNA前病毒前病毒DNA细胞基因组细胞基因组 DNA病毒病毒RNA-癌基因癌基因RNA病病毒颗粒毒颗粒宿主细胞宿主细胞再感染再感染宿主细胞宿主细胞携带癌基因携带癌基因的病毒颗粒的病毒颗粒RNARNA病毒与宿主细胞基病毒与宿主细胞基因组整合过程

12、示意图因组整合过程示意图癌变癌变因此，因此，病毒癌基因（病毒癌基因（v-onc）就是指一类存在于就是指一类存在于肿瘤病毒中，能使宿主细胞发生恶性转化的基肿瘤病毒中，能使宿主细胞发生恶性转化的基因。因。细胞癌基因细胞癌基因(c-onc)又称为原癌基因（又称为原癌基因（proto-oncogene），存在于细胞基因组中、正常情存在于细胞基因组中、正常情况下处于静止或低水平（限制性）表达状态况下处于静止或低水平（限制性）表达状态，对维持细胞正常功能具有重要作用，当受，对维持细胞正常功能具有重要作用，当受到致癌因素作用被活化而导致细胞恶变的基到致癌因素作用被活化而导致细胞恶变的基因因。广泛存在于生物界

13、广泛存在于生物界 基因序列高度保守基因序列高度保守 表达产物对细胞正常生长、繁殖、发育和分表达产物对细胞正常生长、繁殖、发育和分化起着精确的调控作用。化起着精确的调控作用。基因结构发生异常或表达失控，导致细胞生基因结构发生异常或表达失控，导致细胞生长增殖和分化异常长增殖和分化异常指来源于病毒等的启动子或增强子插入到细胞指来源于病毒等的启动子或增强子插入到细胞癌基因的附近或内部而使其开放并异常转录。癌基因的附近或内部而使其开放并异常转录。如鸡白细胞增生病毒引起的淋巴瘤，就是由于如鸡白细胞增生病毒引起的淋巴瘤，就是由于病毒的病毒的DNA序列整合到宿主细胞序列整合到宿主细胞c-myc基因附近基因附近

14、，成为该基因的强启动子，导致，成为该基因的强启动子，导致c-myc基因过强基因过强表达。表达。（一一）插入激活）插入激活即基因数量或拷贝数目明显增加。即基因数量或拷贝数目明显增加。常见的为常见的为myc原癌基因，由于其基因数目的增多原癌基因，由于其基因数目的增多而使其表达的蛋白产物增多。而使其表达的蛋白产物增多。（二二）基因扩增）基因扩增 常见的为常见的为ras原癌基因的点突变。原癌基因的点突变。ras原癌基因点突变后导致其原癌基因点突变后导致其GTPase活性下降，不能活性下降，不能将其结合的将其结合的GTP迅速水解，从而使其持续保持激活状态。迅速水解，从而使其持续保持激活状态。正常细胞正常

15、细胞 H-ras 基因碱基序列基因碱基序列 ATG ACG GAA TAT AAG CTG GTG GTG GTG GGC GCC GGC GGT GTG肿瘤细胞肿瘤细胞 H-ras 基因碱基序列基因碱基序列 ATG ACG GAA TAT AAG CTG GTG GTG GTG GGC GCC GTC GGT GTG正常细胞正常细胞 P21 蛋白氨基酸序列蛋白氨基酸序列 Met Thr Glu Tyr Lys Leu Val Val Val Gly Ala Gly Ala Val肿瘤细胞肿瘤细胞 P21 蛋白氨基酸序列蛋白氨基酸序列 Met Thr Glu Tyr Lys Leu Val V

16、al Val Gly Ala Val Ala ValH-ras基因的点突变基因的点突变（三三）点突变）点突变Ras Proto-oncogene Mutated in 30%of all cancers.A“molecular switch”in the signal transduction pathway leading from growth factors to gene expression controlling cell proliferation:GF receptor Ras TF target genes growth.A single amino acid change

17、in Ras protein can cause constant stimulation of the pathway,even in the absence of growth factors.由于染色体重排而导致细胞癌基因从正常位置转移到由于染色体重排而导致细胞癌基因从正常位置转移到另一位置，常常是插入一启动子后而使其转录活性增另一位置，常常是插入一启动子后而使其转录活性增加。加。Burkitt淋巴瘤中，含有淋巴瘤中，含有c-myc的的8号染色体易位，与号染色体易位，与14号染色体连接，靠近免疫球蛋白肽链的基因，与该区号染色体连接，靠近免疫球蛋白肽链的基因，与该区活性很高的启动子连接而受

18、到活化。活性很高的启动子连接而受到活化。c-abl原癌基因，经重排后插入到另一称为原癌基因，经重排后插入到另一称为bcr基因的启基因的启动子之后，而使其转录活性增加，从而引起慢性粒细动子之后，而使其转录活性增加，从而引起慢性粒细胞性白血病的发生。胞性白血病的发生。（四四）染色体易位）染色体易位Chromosomal Translocation that creates Philadelphia ChromosomeBCR-ABL Oncogene:Breaks in ABL Gene of Chromosome 9 andBCR Gene of Chromosome 22Fusion Prot

19、ein causes Chronic Myelogenous Leukemia 出现新的表达产物出现新的表达产物 出现过量的正常表达产物出现过量的正常表达产物 出现异常、截短的表达产物出现异常、截短的表达产物n 癌基因激活的结果：癌基因激活的结果：不同癌基因有不同的激活方式，一种癌基因也可有几种不同癌基因有不同的激活方式，一种癌基因也可有几种激活方式激活方式：c-myc、ras肿瘤细胞中常发现两种或多种细胞癌基因的活化肿瘤细胞中常发现两种或多种细胞癌基因的活化，如白血病细胞株HL-60中有c-myc和N-ras的同时活化。例：原代培养大鼠胚胎成纤维细胞作用于作用于细胞膜上的受体系统细胞膜上的受

20、体系统或或直接被传递直接被传递至细胞内至细胞内，通过蛋白激酶活化转录因子，引发，通过蛋白激酶活化转录因子，引发一系列基因的转录激活。一系列基因的转录激活。sis表达蛋白表达蛋白P28P28和和PDGFPDGF一样能促进血一样能促进血管的生长。管的生长。（一）细胞外生长因子（一）细胞外生长因子n 例如：例如：（二）跨膜的生长因子受体：（二）跨膜的生长因子受体：接受细胞外的生长信号并将其传入胞内。接受细胞外的生长信号并将其传入胞内。受体的胞质结构区具有特异的蛋白激酶活性，通受体的胞质结构区具有特异的蛋白激酶活性，通过磷酸化作用使其结构发生改变，增加激酶对底过磷酸化作用使其结构发生改变，增加激酶对底

21、物的活性，促进生长信号在胞内的传递。物的活性，促进生长信号在胞内的传递。n 例如例如 EGFREGFR、HER2HER2有有酪氨酸特异的蛋白激酶活性。酪氨酸特异的蛋白激酶活性。非受体酪氨酸激酶非受体酪氨酸激酶(src，abl)、丝氨酸、丝氨酸/苏苏氨酸激酶氨酸激酶(raf)，ras蛋白蛋白(H-ras，K-ras和和N-ras)及磷脂酶及磷脂酶(crk产物产物)。（三）细胞内信号传导分子（三）细胞内信号传导分子原癌基因的产物原癌基因的产物作为胞内信息传递体系成作为胞内信息传递体系成员，或者通过影响第二信使作用员，或者通过影响第二信使作用，将接受到的将接受到的信号由胞内传至核内，促进细胞生长。信

22、号由胞内传至核内，促进细胞生长。n 例如：例如：（四）核内转录因子（四）核内转录因子某些癌基因表达蛋白定位于细胞核内，某些癌基因表达蛋白定位于细胞核内，与靶基因的顺式调控元件相结合与靶基因的顺式调控元件相结合直接调节靶直接调节靶基因的转录活性。基因的转录活性。n 例如：例如：c-f o s 是 一 种 即 刻 早 期 反 应 基 因是 一 种 即 刻 早 期 反 应 基 因(immediate early gene，IEG)。作为传递信。作为传递信息的第三信使。息的第三信使。生长因子生长因子 生长因子受体生长因子受体 蛋白激酶及其他信号蛋白激酶及其他信号转导组分转导组分 细胞周期蛋白细胞周期蛋

23、白 细胞凋亡调控因子细胞凋亡调控因子 转录因子转录因子原癌基因原癌基因BRAFBRAF所编码的蛋白质属于丝所编码的蛋白质属于丝/苏氨苏氨酸激酶，是酸激酶，是MAPKMAPK信号通路的重要组成分子，在信号通路的重要组成分子，在调控细胞增殖、分化等方面发挥重要作用。调控细胞增殖、分化等方面发挥重要作用。约约60%的黑素瘤中的黑素瘤中BRAF发生发生突变，其第突变，其第600位氨基酸从缬氨酸突位氨基酸从缬氨酸突变为谷氨酸（变为谷氨酸（V600E）最为常见，）最为常见，导致导致B-Raf的持续激活。的持续激活。（一）（一）BRAFn 例如：例如：分子靶向药物分子靶向药物 威罗菲尼威罗菲尼Vemuraf

24、enibHER2HER2是表皮生长因子受体家族成员，具有是表皮生长因子受体家族成员，具有蛋白酪氨酸激酶活性，能激活下游信号通路，从蛋白酪氨酸激酶活性，能激活下游信号通路，从而促进细胞增殖和抑制细胞凋亡。而促进细胞增殖和抑制细胞凋亡。在在30%的乳腺癌中的乳腺癌中HER2基因基因发生扩增或者过度表达，其表达发生扩增或者过度表达，其表达水平与治疗后复发率和不良预后水平与治疗后复发率和不良预后显著相关。显著相关。（二）（二）HER2n例如：例如：单克隆抗体药物单克隆抗体药物 赫塞汀赫塞汀Herceptin慢性粒细胞白血病患者的慢性粒细胞白血病患者的9 9号染色体与号染色体与2222号染号染色体之间发

25、生易位，从而融合产生了癌基因色体之间发生易位，从而融合产生了癌基因BCR-BCR-ABLABL，编码的蛋白质，编码的蛋白质Bcr-AblBcr-Abl具有持续活化的蛋白具有持续活化的蛋白酪氨酸激酶活性，能促进细胞增殖，并增加基因酪氨酸激酶活性，能促进细胞增殖，并增加基因组的不稳定性。组的不稳定性。在在95%的慢性粒细胞白血病患的慢性粒细胞白血病患者中都伴随有者中都伴随有BCR-ABL融合基因的融合基因的产生，在一些急性淋巴白血病患者产生，在一些急性淋巴白血病患者中也有发现。中也有发现。（三）（三）BCR-ABLn 例如：例如：分子靶向药物分子靶向药物 伊马替尼伊马替尼 ImatinibAcqu

26、ired mutations of oncogenes Most cancer causing mutations involving oncogenes are acquired,not inherited.They generally activate oncogenes by chromosome rearrangements,gene duplication,or mutation.For example,a chromosome rearrangement leads to formation of the gene called BCR-ABL.This leads to the

27、disease chronic myeloid leukemia(CML).the gain-of-function mutations that convert proto-oncogenes to oncogenes act dominantly;that is,mutation in only one of the two alleles is sufficient for induction of cancer.Inherited mutations of oncogenes A few cancer syndromes are caused by inherited mutation

28、s of proto-oncogenes Multiple endocrine neoplasia type 2(多发性内分泌瘤)is caused by an inherited mutation in the gene called RET.Inherited mutations in the gene called KIT cause hereditary gastrointestinal stromal tumors(胃肠道间质瘤,GIST).Inherited mutations in the gene called MET cause hereditary papillary re

29、nal cancer（乳头状肾癌）.Cancers Usually Result from a Series of Mutations in a Single Cell Colon Cancer:MSH2MSH2和和MLH1MLH1基因失活基因失活染色体：染色体：改改 变：变：基基 因：因：5q 突变或缺失突变或缺失 FAP、APC、MCC？12q 突变突变 K-ras18q 缺失缺失 DCC17q 缺失和突变缺失和突变 p53正正 常常肠上皮肠上皮高增殖高增殖肠上皮肠上皮早期早期腺瘤腺瘤中期中期 腺瘤腺瘤晚期晚期 腺瘤腺瘤腺癌腺癌转转 移移 癌癌nm23突变突变DNADNA低甲基化低甲基化其

30、他基因的改变（如其他基因的改变（如TGF-TGF-受体）受体）Tumor Suppressor Genes Tumor Suppressor genes:are genes that act to inhibit cell proliferation and tumor development.If Tumor Suppressor Gene is Mutated Inactivated It will lead to cell transformationn 肿瘤抑制基因肿瘤抑制基因(tumor suppressor gene)也称抗癌基因（也称抗癌基因（anticancer gene）或抑

31、癌基）或抑癌基因，是调节细胞正常生长和增殖的基因。当这些基因，是调节细胞正常生长和增殖的基因。当这些基因不能表达，或者当它们的产物失去活性时，细胞因不能表达，或者当它们的产物失去活性时，细胞就会异常生长和增殖，最终导致细胞癌变。反之，就会异常生长和增殖，最终导致细胞癌变。反之，若导入或激活它则可抑制细胞的恶性表型。若导入或激活它则可抑制细胞的恶性表型。First discovered in 1960s by Henry Harris.Harris fused tumor cells with normal cells and discovered some of the hybrid cell

32、s were normal.Harris hypothesized that the normal cells contained gene products that suppressed uncontrolled cell proliferation.Five broad classes of proteins encoded by tumor-suppressor genes Intracellular proteins,such as the p16 cyclin-kinase inhibitor,that regulate or inhibit progression through

33、 a specific stage of the cell cycle.Receptors for secreted hormones(e.g.,tumor derived growth factor)that function to inhibit cell proliferation.Checkpoint-control proteins that arrest the cell cycle if DNA is damaged or chromosomes are abnormal.Proteins that promote apoptosis.Enzymes that participa

34、te in DNA repair.Sporadic retinoblastoma 60%of retinoblastoma cases.Develops in children with no family history.Occurs in one eye.Hereditary retinoblastoma 40%of retinoblastoma cases.Onset typically is earlier than sporadic cases.Multiple tumors involving both eyes.Retinoblastoma(Rb)caused bymutated

35、 Rb geneThe First Tumor-Suppressor Gene 视网膜母细胞瘤视网膜母细胞瘤Two mutations are required for the development of retinoblastoma.Sporadic retinoblastoma Child starts with two wild type alleles(RB+/RB+).Both alleles must mutate to produce the disease(RB/RB).Probability of both mutations occurring in the same c

36、ell is low;only one tumor forms(e.g.,one eye).Hereditary retinoblastoma Child starts with heterozygous alleles(RB/RB+).Only one mutation is required to produce disease(RB/RB).Mutations resulting in loss of heterozygosity(LOH)are more probable in rapidly dividing cells,and multiple tumors occur(e.g.,

37、both eyes).Loss of heterozygosity(LOH)杂合性缺失杂合性缺失Rb基因的表达产物为基因的表达产物为P105Rb，在细胞内存在低，在细胞内存在低磷酸化型（活性型）和高磷酸化型（非活性型磷酸化型（活性型）和高磷酸化型（非活性型）两种类型。）两种类型。不同类型的不同类型的P105Rb对转录因子对转录因子E2F有不同的亲和有不同的亲和力。力。G0 G1期期Rb蛋白蛋白E-2FS期期E-2FDNAmRNADNARb蛋白蛋白 Tumor suppressors must be inactivated This means both copies must be lost/

38、mutatedHereditary cancer is caused by the inheritance ofone copy of a defective tumor suppressor1.Antagonize the action of oncogenes eg.p53 is activated by oncogenes.p53 protects against cancer by inducing cell cycle arrest and/or apoptosisFunctions of Tumor Suppressor genesmyccell growthp532.Block

39、proliferation:Cell cycle inhibitors:eg.Rb blocks entry into S phase by binding to and inhibiting RB.INK-4 gene:that produces P16 that inhibits cdk4/cyclin D action(to phosphorylate Rb gene to inactivate its action)Repressor transcription factors:e.g.;WT1 is a repressor that appears to suppress trans

40、cription factor(Insulin like growth factor)which will contribute in the development of tumor.Activator transcription factors:e.g.;SMAD family that are activated by TGF-,leading to inhibition of cell proliferation.P53:that produces P21 that has the same action of P16 in inhibiting the action of cdk/c

41、yclin.Functions of Tumor Suppressor genes3.Induce apoptosis:Form of cell suicide.A cell which has lost growth control will often undergo apoptosis.Cell damage or stress can also lead to apoptosis.p53 is a critical regulator of apoptosis.Transcription factor which activates pro-apoptotic moleculesFun

42、ctions of Tumor Suppressor genes Most commonly mutated gene in cancers(50%of total).When p53 is mutated,DNA-damaged cells are not arrested in G1 and DNA repair does not take place.This failure to arrest DNA-damaged cells will be repeated in subsequent cell cycles permitting other mutations to accumu

43、late,culminating in neoplastic transformation.tumor formation and cancer.p53 Mutationsp53 the guardian ofthe genomeRegulation of the cell cycle4.DNA Repair DNA repair prevents the accumulation of mutations Defects in DNA repair genes leads to genomic instability Accelerates the activation of oncogen

44、es and the loss of tumor suppressors Many cancer prone syndromes associated with defects in DNA repair,BRCA1,ATM,MRE11,NBS,Functions of Tumor Suppressor genes A small proportion of breast cancer is heritable.Two genes are associated with predisposition to breast cancer.BRCA1 on chromosome 17 BRCA2 o

45、n chromosome 13 Normal function of both is in repair of ds DNA breaks.Breast Cancer Tumor Suppressors Tumor suppressor genes inhibit oncogenes suppress proliferation Induce cell death repair DNA prevent mutation These are“loss of function”or recessive mutations.Responsible for hereditary forms of ca

46、ncer Being heterozygous enhances the probability of cancer but this will require a mutation in the corresponding other allele.e.g.,it need to be homozygous for the gene.p53l A transcription factor that regulates genes controlling cell division and cell death.l Important in the cellular response to D

47、NA damage.l Aids in decision between repair and induction of cell death.Rbl Functions by altering transcription factor activity.l Contributes to the control of cellular division by acting as an inhibitor.APCl The APC protein binds and stimulates the degradation of a transcription factor.l Absence of

48、 functional APC protein leads to increased cell division.BRCAl BRCA proteins have multiple functions including repairing DNA damage and regulation of gene expression.l Non-functional BRCA leads to compromised DNA repair and gene regulation.第三节第三节n 生长因子生长因子(growth factor)一类由细胞分泌的、类似于激素的信号分一类由细胞分泌的、类似

49、于激素的信号分子，多数为肽类（含蛋白类）物质，具有调节子，多数为肽类（含蛋白类）物质，具有调节细胞生长与分化细胞生长与分化的作用。的作用。内分泌内分泌(endocrine)旁分泌旁分泌(paracrine)自分泌自分泌(autocrine)n 作用模式作用模式：生长因子分泌后，通过血液运输作用于远端靶细胞细胞分泌生长因子作用于邻近其它类型细胞，对自身细胞不发生作用生长因子作用于合成及分泌该生长因子的细胞本身（一）生长因子的分（一）生长因子的分类类生长因子名称生长因子名称组织来源组织来源功能功能表皮生长因子（表皮生长因子（EGF）唾液腺、巨噬细胞、唾液腺、巨噬细胞、血小板等血小板等促进表皮与上皮

50、细胞的生长，尤其是促进表皮与上皮细胞的生长，尤其是消化道上皮细胞的增殖消化道上皮细胞的增殖肝细胞生长因子（肝细胞生长因子（HGF）间质细胞间质细胞促进细胞分化和细胞迁移促进细胞分化和细胞迁移促红细胞生成素（促红细胞生成素（EPO）肾肾调节成红细胞的发育调节成红细胞的发育类胰岛素生长因子（类胰岛素生长因子（IGF）血清血清促进硫酸盐参入到软骨组织促进软骨促进硫酸盐参入到软骨组织促进软骨细胞的分裂、对多种组织细胞起胰岛细胞的分裂、对多种组织细胞起胰岛素样作用素样作用神经生长因子（神经生长因子（NGF）颌下腺含量高颌下腺含量高营养交感和某些感觉神经元、防止神营养交感和某些感觉神经元、防止神经元退化经