基础分 子 生物学 第九章疾病与 人类健康. 魏 文胜 新 生物楼

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1 基础分 子 生物学 第九章疾病与 人类健康 魏 文胜 新 生物楼

2 Chapter 9 - Outline 9.1 Molecular Mechanism of Disease_Pathology Perspective Cell Death Acute & Chronic Inflammation Infection & Host Response Neoplasia 9.2 Molecular Mechanism of Disease_Molecular Biology Perspective 9.3 Molecular Pathology of Disease Cancer Infectious Disease Inherited Disease Metabolic Disease 9.4 Practice of Molecular Medicine Molecular Diagnosis Pharmacogenomics & Personal Medicine 10

3 Chapter 9 - Outline 9.1 Molecular Mechanism of Disease_Pathology Perspective Cell Death Acute & Chronic Inflammation Infection & Host Response Neoplasia 9.2 Molecular Mechanism of Disease_Molecular Biology Perspective 9.3 Molecular Pathology of Disease Cancer Infectious Disease Inherited Disease Metabolic Disease 9.4 Practice of Molecular Medicine Molecular Diagnosis Molecular Assessment of Disease Pharmacogenomics & Personal Medicine 11

4 9.1 Molecular Mechanism of Disease: Cell Death A common theme in disease is death of cells. In diseases ranging from stroke to congestive heart disease to alcoholic cirrhosis of the liver, death of individual cells leads to irreversible functional loss in whole organs and ultimately mortality. Therapeutic goal: preventing cell death. In neoplasia, the uncontrollable growth of cancer cells leads to damage and failure of important organs. Therapeutic goal: killing the proliferating cancer cells. 12

5 9.1 Molecular Mechanism of Disease: Cell Death - MODES OF CELL DEATH Necrosis, a pathological term referring to areas of dead cells within a tissue or organ. Necrosis is typically the result of an acute and usually profound metabolic disruption, such as ischemia/reperfusion and severe toxicant-induced damage. Programmed cell death, most commonly manifested as apoptosis. In apoptosis, specific stimuli initiate execution of well-defined pathways leading to orderly resorption of individual cells with minimal leakage of cellular components into the extracellular space and little inflammation. Whereas necrotic cell death occurs with abrupt onset after adenosine triphosphate (ATP) depletion, apoptosis may take hours to go to completion and is an ATP-requiring process without a clearly distinguished point of no return. Apoptosis and necrosis can share initiating factors and signaling pathways to become extremes on a phenotypic continuum of necrapoptosis or aponecrosis. 13

6 9.1 Molecular Mechanism of Disease: Cell Death - Necrosis Necrosis cell rounding mitochondrial swelling rarefaction of cytosol dilatation of the ER and the space between the nuclear membranes (*) chromatin condensation discontinuities in the PM 14 Molecular Pathology. William B. Coleman, et al. 2009

7 9.1 Molecular Mechanism of Disease: Cell Death - Apoptosis Mammalian caspases. Caspases are evolutionarily conserved aspartate specific cysteine-dependent proteases that function in apoptotic and inflammatory signaling. Initiator caspases are involved in the initiation and propagation of apoptotic signaling Effector caspases act on a wide variety of proteolytic substrates to induce the final and committed phase of apoptosis. Initiator and inflammatory caspases have large prodomains containing oligomerization motifs such as the caspase recruitment domain (CARD) and the death effector domain. Effector caspases have short prodomains and are proteolytically activated by large prodomain caspases and other proteases. Proteolytic cleavage of procaspase precursors forms separate large and small subunits that assemble into active enzymes consisting of two large and two small subunits. Caspase activation occurs in multimeric complexes that typically consist of a platform protein that recruits procaspases either directly or by means of adaptors. Such caspase complexes include the apoptosome and the death-inducing signaling complex (DISC). Caspase 14 plays a role in terminal keratinocyte differentiation in ornified epithelium. 15 Molecular Pathology. William B. Coleman, et al. 2009

8 9.1 Molecular Mechanism of Disease: Cell Death - Apoptosis 16 Molecular Pathology. William B. Coleman, et al. 2009

9 9.1 Molecular Mechanism of Disease: Cell Death - Apoptosis TNFa apoptotic signaling. TNFa binds to its receptor, TNFR1, and Complex I forms composed of TRADD (TNFR-associated protein with death domain), RIP (receptor-interacting protein), TRAF-2 (TNF-associated factor-2]. Complex I activates NFkB (nuclear factor kappa B), and JNK (c-jun N-terminal kinase). NFkB activates transcription of survival genes, including anti-apoptotic inhibitor of apoptosis proteins (IAPs), antiapoptotic Bcl- XL, and inducible nitric oxide synthase. Complex I then undergoes ligand-dissociated internalization to form DISC Complex II. Complex II recruits FADD (Fas-associated death domain) via interactions between conserved death domains (DD) and activates procaspase 8 through interaction with death effector domains (DED). Active caspase 8 cleaves Bid to t Bid, which translocates to mitochondria leading to mitochondrial permeabilization, cytochrome c release, and apoptosis. Adapted with permission from. 17 Molecular Pathology. William B. Coleman, et al. 2009

10 9.1 Molecular Mechanism of Disease: Cell Death - Progression of mitophagy, apoptosis, and necrosis 18 Molecular Pathology. William B. Coleman, et al. 2009

11 9.1 Molecular Mechanism of Disease: Acute & Chronic Inflammation The recognition of pathogenic insults can be accomplished by a number of mechanisms that function to initiate inflammatory responses. This initial response when functioning optimally will lead to a minimal leukocyte accumulation and activation for the clearance of the inciting agent and have little effect on homeostatic function. Strong inflammatory response leads to the damage and tissue destruction in an attempt to clear the inciting agent from the system. ---> acutely catastrophic: leading to local or even systemic damage to the tissue or organs, resulting in degradation of normal physiologic function. Alternatively, the failure to regulate the response or clear the inciting agent could lead to chronic and progressively more pathogenic responses. 19

12 9.1 Molecular Mechanism of Disease: Acute & Chronic Inflammation - Toll-Like Receptors 20

13 9.1 Molecular Mechanism of Disease: Acute & Chronic Inflammation - Cytoplasmic pathogen receptors allow activation of cytokines responsible for the upregulation of inflammatory processes 21

14 9.1 Molecular Mechanism of Disease: Acute & Chronic Inflammation - Helicase proteins induce early response and activating cytokines by recognition of dsrna 22

15 9.1 Molecular Mechanism of Disease: Infection & Host Response Disease is one of the major driving forces of evolution. Humans have a generation time of roughly 20 years, and even small mammals reproduce in weeks to months. In contrast, microbial generation times range from minutes to days. Thus, microbes evolve hundreds to thousands of times more rapidly than their vertebrate hosts. It is remarkable that humans and other higher organisms have managed to survive at all. Large multicellular creatures represent concentrated, extremely rich nutrient sources for microbes. Therefore, the survival of multicellular creatures requires that they have sufficient defenses to prevent easy invasion and consumption. Because pathogens exert immense selective pressure, many aspects of host physiology have a role in preventing infection, in addition to the immune system. In most cases, the pathologies induced by microbial pathogens primarily serve to aid microbial spreading to new hosts. i.e., coughing, sneezing, and diarrhea. 23

16 9.1 Molecular Mechanism of Disease: Infection & Host Response Host Effector Mechanisms 24

17 9.1 Molecular Mechanism of Disease: Infection & Host Response Recognition of Microbial Products Through Toll-like Receptors 25

18 9.1 Molecular Mechanism of Disease: Infection & Host Response How Virus Damage Cells 26

19 27

20 9.1 Molecular Mechanism of Disease: Neoplasia - plasia Anaplasia dedifferentiation Aplasia when an entire organ or a part of an organ is missing Hypoplasia inadequate or below-normal number of cells Hyperplasia physiological proliferative Increase in number of cells Neoplasia abnormal proliferation Dysplasia change of phenotype (size,shape and organization of tissue) Metaplasia cell type conversion Prosoplasia cell type develops new function Desmoplasia connective tissue growth 28

21 9.1 Molecular Mechanism of Disease: Cancer Definition Cancer is a term used for diseases in which abnormal cells divide without control and are able to invade other tissues. Cancer cells can spread to other parts of the body through the blood and lymph systems. Cancer is not just one disease but many diseases. 29

22 9.1 Molecular Mechanism of Disease: What is Cancer? 30

23 9.1 Molecular Mechanism of Disease: Origins of Cancer Normal cell division Cell damage - no repair Cell Suicide or Apoptosis Cancer cell division First mutation Second mutation Third mutation Fourth or later mutation Uncontrolled growth 31

24 9.1 Molecular Mechanism of Disease: What Causes Cancer? Cancer arises from one single cell. The transformation from a normal cell into a tumor cell is a multistage process, a result of the interaction between a person's genetic factors and three categories of external agents, including: physical carcinogens, such as ultraviolet and ionizing radiation chemical carcinogens, such as asbestos ( 石棉 ), components of tobacco smoke, aflatoxin ( 黄曲霉素,a food contaminant) and arsenic ( 砒霜,a drinking water contaminant) biological carcinogens, such as infections from certain viruses, bacteria or parasites. 32

25 9.1 Molecular Mechanism of Disease: What Causes Cancer? Some viruses or bacteria Some chemicals Radiation Heredity Diet Hormones 33

26 9.1 Molecular Mechanism of Disease: What Causes Cancer? - Outcomes of Carcinogen Metabolic Activation 34 Burger s Medicinal Chemistry and Drug Discovery, 6th Edition, Vol. 5. ISBN , 2003.

27 9.1 Molecular Mechanism of Disease: What Causes Cancer? Some examples of infections associated with certain cancers: Viruses: hepatitis B and liver cancer, Human Papilloma Virus (HPV, 乳突淋瘤 ) and cervical cancer, and human immunodeficiency virus (HIV) and Kaposi sarcoma. Bacteria: Helicobacter pylori( 幽 门螺旋菌 )and stomach cancer. Parasites: schistosomiasis ( 血吸 虫病 ). 35

28 9.1 Molecular Mechanism of Disease: Heredity and Cancer All Breast Cancer Patients Inherited factor(s) Other factor(s) 36

29 9.1 Molecular Mechanism of Disease: Cancer Incidence Increases with Age Multiple mutations that lead to formation of a tumor may require many years to accumulate. The occurrence of cancer after the age of reproduction may be one reason that evolutionary restraints have not done more to suppress cancer. The requirement for multiple mutations lowers the frequency of cancer. Huge numbers of cells during our lifetimes mimic evolutionary selection for cells that proliferate. The tumor itself is not inherited. 37

30 Chapter 9 - Outline 9.1 Molecular Mechanism of Disease_Pathology Perspective Cell Death Acute & Chronic Inflammation Infection & Host Response Neoplasia 9.2 Molecular Mechanism of Disease_Molecular Biology Perspective 9.3 Molecular Pathology of Disease Cancer Infectious Disease Inherited Disease Metabolic Disease 9.4 Practice of Molecular Medicine Molecular Diagnosis Molecular Assessment of Disease Pharmacogenomics & Personal Medicine 38

31 9.2 Molecular Mechanism of Disease Protein malfunctions related to gene mutations lead to organ dysfunction and disease states. Many genetic diseases have been discovered as a result of a single mutation or a specific chromosomal rearrangement and are now understood at the molecular level. i.e., sicklecell anemia, hemophilia, cystic fibrosis, Duchenne muscular dystrophy, Tay-Sachs disease, Down syndrome, Li-Fraumeni syndrome, Wilm s tumor, Prader-Willi syndrome, Angelman s syndrome, and many metabolic disorders. Human diseases that can be traced to a single altered protein have a 1 percent frequency in the total population. Most diseases are multifactorial, caused by many genes and proteins interacting with one another and with the environment. 39

32 9.2 Molecular Mechanism of Disease 40

33 Mutations and Human Diseases Human mutations range from single point mutations to large deletions. Some common mutations occur where the modified base 5- methylcytosine is converted to thymine. 41

34 DNA Repair and Cancer 42 Lehninger Principles of Biochemistry, Fourth Edition

35 9.2 Molecular Mechanism of Disease Genes that code for receptors and membrane transport proteins can also be mutated and cause other diseases. 43

36 Abnormal or Missing Proteins: The Mutant Phenotype Chromosomal abnormalities include loss or gain of one or more chromosomes, loss or gain of a piece of a chromosome, or transfer of a piece from one chromosome to another. Some abnormalities are inherited. Some are the result of nondisjunction during meiosis (or early mitosis). About 90 percent of human zygotes that have one X chromosome and no Y (Turner Syndrome) fail to survive beyond 4 months of gestation. A common cause of mental retardation is fragile-x syndrome. 44

37 9.2 Molecular Mechanism of Disease: Human Genome - TYPES OF GENETIC DISEASES Genetic Diseases Associated with Gene Inversions i.e., Williams-Beuren syndrome, Angelman s syndrome, etc. Genetic Diseases Associated with Gene Deletions i.e., red-green color blindness Genetic Diseases Associated with Gene Duplications i.e., Charcot-Marie-Tooth disease (CMT) 45

38 9.2 Molecular Mechanism of Disease: Epigenetics Epigenetic processes, defined as the heritable patterns of gene expression that do not involve changes in the sequence of the genome, and their effects on gene repression are increasingly understood to be such a way of modulating phenotype transmission and development. The patterns of DNA methylation, histone modifications, micrornas, and several chromatin-related proteins of sick cells usually differ from those of healthy cells, highlighting the importance of epigenetic regulation in most human pathologies. 46

39 9.2 Molecular Mechanism of Disease: Epigenetics - A model for the disruption of histone modifications and DNA methylation patterns in cancer cells 47

40 9.2 Molecular Mechanism of Disease: Epigenome 48

41 Chapter 9 - Outline 9.1 Molecular Mechanism of Disease_Pathology Perspective Cell Death Acute & Chronic Inflammation Infection & Host Response Neoplasia 9.2 Molecular Mechanism of Disease_Molecular Biology Perspective 9.3 Molecular Pathology of Disease Cancer Infectious Disease Inherited Disease Metabolic Disease 9.4 Practice of Molecular Medicine Molecular Diagnosis Molecular Assessment of Disease Pharmacogenomics & Personal Medicine 49

42 9.3 Molecular Pathology of Disease: Key Facts of Cancer Cancer is a leading cause of death worldwide: it accounted for 7.4 million deaths (around 13% of all deaths) in Lung, stomach, liver, colon and breast cancer cause the most cancer deaths each year. The most frequent types of cancer differ between men and women. More than 30% of cancer deaths can be prevented. Tobacco use is the single most important risk factor for cancer. Deaths from cancer worldwide are projected to continue rising, with an estimated 12 million deaths in

43 9.3 Molecular Pathology of Disease: Cancer Statistics 全球 ~1000 多万 人新患癌症 / 年 ~740 多万 人死于癌症 / 年 ~ 每 4-5 秒钟就有 一名癌症患者死亡 中国 ~150 万 人新患癌症 / 年 ~80 万 人死于癌症 / 年 从 1949 年占总死亡原因的第 十位已经上升到第 一位 51

44 9.3 Molecular Pathology of Disease: Main Category of Cancer Carcinoma - cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma - cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia - cancer that starts in blood-forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and myeloma - cancers that begin in the cells of the immune system. Central nervous system cancers - cancers that begin in the tissues of the brain and spinal cord. 52

45 Main Category of Cancer (Continued) Some common carcinomas: Lung Breast (women) Leukemias: Bloodstream Lymphomas: Lymph nodes Colon Bladder Prostate (men) Some common sarcomas: Fat Bone Muscle 53

46 9.3 Molecular Pathology of Disease: Naming Cancer Cancer Prefixes Point to Location Prefix Meaning adeno- chondro- erythro- gland cartilage red blood cell hemangio- blood vessels hepatolipolymphomelanomyelomyoosteo- liver fat lymphocyte pigment cell bone marrow muscle bone There are more than 100 different types of cancer. Most cancers are named for the organ or type of cell in which they start - i.e., cancer that begins in the colon is called colon cancer; cancer that begins in basal cells of the skin is called basal cell carcinoma. 54

47 Genes Directly Related to Cancer Oncogenes encode defective signaling proteins. By continually giving the signal for cell division, they lead to tumor formation. Oncogenes are genetically dominant and may encode defective growth factors, receptors, G proteins, protein kinases, or nuclear regulators of transcription. Tumor suppressor genes encode regulatory proteins that normally inhibit cell division; mutations in these genes are genetically recessive but can lead to tumor formation. 55

48 Proto-oncogene 原癌基因 ( 细胞转化基因 ) Proto-oncogene Cellular oncogene, C-onc 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, 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因 56

49 Gain-of-Function Mutations Convert Proto-oncogenes into Oncogenes At least four mechanisms can produce oncogenes from the corresponding proto-oncogenes Point mutation (i.e., change in a single base pair) Chromosomal translocation that fuses two genes together to produce a hybrid gene encoding a chimeric protein whose activity, unlike that of the parent proteins, often is constitutive Chromosomal translocation that brings a growth regulatory gene under the control of a different promoter that causes inappropriate expression of the gene Amplification (i.e., abnormal DNA replication) of a DNA segment including a proto-oncogene, so that numerous copies exist, leading to overproduction of the encoded protein 57

50 Cancer-Causing Viruses Contain Oncogenes or Activate Cellular Proto-oncogenes RSV (Rous sarcoma virus) was discovered in 1911 by Peyton Rous by injecting cell free extract of chicken tumor into healthy Plymouth Rock chickens. The extract was found to induce oncogenesis. The tumor was found to be composed of connective tissue (a sarcoma). Rous was awarded the Nobel Prize for the significance of his discovery in

51 Structure of Retrovirus 59

52 Genome of Retrovirus 长末端重复序列 正常的病毒基因 癌基因 LTR gag pol env src LTR 调节和启动转录 产 生病毒表 面糖蛋 白 产 生逆转录酶和整合酶 产 生病毒垮膜蛋 白 产 生 p60 src 蛋 白质, 磷酸化蛋 白 靶蛋 白磷酸化 60

53 Origin of Retroviral v-onc LTR GAG POL ENV LTR LTR GAG POL ENV v-src LTR 61

54 Origin of Retroviral v-onc 62

55 Conversion of a regulatory gene to a viral oncogene 63 Lehninger, Principles of Biochemistry, 4th Edition

56 Oncogene-encoded Proteins 64

57 Tumor Suppressor Genes Normal cell Normal genes prevent cancer Remove or inactivate tumor suppressor genes Cancer cell Damage to both genes leads to cancer Mutated/inactivated tumor suppressor genes 65

58 Tumor Suppressor Genes Act Like a Brake Pedal Growth factor Tumor Suppressor Gene Proteins Receptor Cell nucleus Signaling enzymes Transcription factors DNA Cell proliferation 66

59 p53 Tumor Suppressor p53 is a tumor suppressor protein that in humans is encoded by the TP53 gene. p53 is important in multicellular organisms, where it regulates the cell cycle and, thus, functions as a tumor suppressor that is involved in preventing cancer. The name p53 is in reference to its apparent molecular mass: It runs as a 53-kilodalton (kda) protein on SDS-PAGE. But, based on calculations from its amino acid residues, p53's mass is actually only 43.7 kda. This difference is due to the high number of proline residues in the protein, which slow its migration on SDS-PAGE, thus making it appear heavier than it actually is. This effect is observed with p53 from a variety of species, including humans, rodents, frogs, and fish. 67

60 p53 Tumor Suppressor 68 Levine, A.J., and Oren, M. (2009). The first 30 years of p53: growing ever more complex. Nat Rev Cancer 9,

61 Tumor Suppressor Genes 69 Burger s Medicinal Chemistry and Drug Discovery, 6th Edition, Vol. 5. ISBN , 2003.

62 Acquired Capabilities of Cancer 70

63 Three Types of Properties of Cancer Cell Immortalization enables cells to overcome a limit on the number of cell divisions Transformation consists of a series of changes that release growth constraints on the immortalized cell Metastasis describes the stage at which the cancer cell gains the ability to invade normal tissue, so that it can move away from the tissue of origin and establish a new colony elsewhere in the body 71

64 9.3 Molecular Pathology of Disease: Cancer A sequence of events must occur before a normal cell becomes malignant. At least three tumor suppressor genes and one oncogene must be mutated in sequence for an epithelial cell in the colon to become metastatic. Although the likelihood of this happening to any given cell is small, the colon has millions of cells that divide constantly in the presence of carcinogens. 72

65 Linear Progression Model of Cancer 73

66 Linear Progression Model of Cancer Histologic and molecular changes in the development of pulmonary squamous cell carcinoma. These changes occur in a stepwise fashion, beginning in histologically normal epithelium. LOH. loss of heterozygosity. 74

67 Epigenetic Changes 75 Burger s Medicinal Chemistry and Drug Discovery, 6th Edition, Vol. 5. ISBN , 2003.

68 76 Burger s Medicinal Chemistry and Drug Discovery, 6th Edition, Vol. 5. ISBN , 2003.

69 Sustaining Proliferative Signaling 77

70 Seven Types of Proteins that Participate in Controlling Cell Growth and Proliferation Oncoproteins Extracellular signaling molecules (I) Signal receptors (II) Signal-transduction proteins (III) Transcription factors (IV) Tumor suppressors Cell cycle control proteins (VI) DNA-repair proteins (VII) Apoptotic proteins (V) include tumor suppressors that promote apoptosis and oncoproteins that promote cell survival. Virus encoded proteins that activate signal receptors (Ia) also can induce cancer. 78 Lehninger, Principles of Biochemistry, 4th Edition

71 79 Lehninger, Principles of Biochemistry, 4th Edition

72 Evading Growth Suppressors 80

73 Cell Cycle and Loss of Cell Cycle Control 81 Burger s Medicinal Chemistry and Drug Discovery, 6th Edition, Vol. 5. ISBN , 2003.

74 Loss of p53 Abolishes the DNA-Damage Checkpoint 82

75 Resisting Cell Death 83

76 Apoptosis and Reduced Sensitivity to Apoptosis 84 Burger s Medicinal Chemistry and Drug Discovery, 6th Edition, Vol. 5. ISBN , 2003.

77 p53 Tumor Suppressor 85 Brown, C.J., Lain, S., Verma, C.S., Fersht, A.R., and Lane, D.P. (2009). Awakening guardian angels: drugging the p53 pathway. Nat Rev Cancer 9,

78 Activating Invasion and Metastasis 86

79 Not all Tumors are Cancerous Benign tumors aren't cancerous. They can often be removed, and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body. Malignant tumors are cancerous. Cells in these tumors can invade nearby tissues and spread to other parts of the body. The spread of cancer from one part of the body to another is called metastasis. 87

80 Malignant vs. Benign Tumors Benign (not cancer) tumor cells grow only locally and cannot spread by invasion or metastasis Malignant (cancer) cells invade neighboring tissues, enter blood vessels, and metastasize to different sites Time 88

81 Why Cancer Is Potentially Dangerous Brain Melanoma cells travel through bloodstream Liver Melanoma (initial tumor) 89

82 Invasion and Metastasis 1 Cancer cells invade surrounding tissues and blood vessels 2 Cancer cells are transported by the circulatory system to distant sites 3 Cancer cells reinvade and grow at new location 90

83 Cancer Tends to Involve Multiple Mutations Benign tumor cells grow only locally and cannot spread by invasion or metastasis Malignant cells invade neighboring tissues, enter blood vessels, and metastasize to different sites Time Mutation inactivates suppressor gene Cells proliferate Mutations inactivate DNA repair genes Proto-oncogenes mutate to oncogenes More mutations, more genetic instability, metastatic disease 91

84 Cancer Tends to Corrupt Surrounding Environment Growth factors = proliferation Invasive Matrix Fibroblasts, adipocytes Proteases Blood vessel Cytokines Cytokines, proteases = migration & invasion 92

85 Cancer Metastasis 93

86 Inducing Angiogenesis 94

87 Tumor Growth Requires Formation of New Blood Vessels Tumors, whether primary or secondary, require recruitment of new blood vessels in order to grow to a large mass. In the absence of a blood supply, a tumor can grow into a mass of about 10 6 cells, roughly a sphere 2 mm in diameter. Most tumors induce the formation of new blood vessels that invade the tumor and nourish it, a process called angiogenesis. This complex process requires several discrete steps: degradation of the basal lamina that surrounds a nearby capillary, migration of endothelial cells lining the capillary into the tumor, division of these endothelial cells, formation of a new basement membrane around the newly elongated capillary. 95

88 Stimulator of Angiogenesis 96

89 Growth of Tumor Vessles 3-incorporation of BM-derived precursors 2-Intussusceptive growth 1-Sprouting 4-Cooption of existing vessels 5-Lymphangiogenesis 97

90 Enabling Replicative Immortality 98

91 99

92 Changes in telomere length over time during tumour progression, compared with changes in normal tissue 100 Blasco, M.A. (2005). Telomeres and human disease: ageing, cancer and beyond. Nat. Rev. Genet. 6,

93 Emerging Hallmarks 101

94 102

95 103