Week 1 Cancer Genetics PDF

CANCER GENETICS Rebecca de Kraa Cytogeneticist, Haematology Department, PathWest Laboratories, Fiona Stanley Hospital Learning Objectives 1) Understand that cancer is a disease of abnormal gene function and expression: Understand the concept of carcinogenesis; and that it is a multi-step process t...

CANCER GENETICS Rebecca de Kraa Cytogeneticist, Haematology Department, PathWest Laboratories, Fiona Stanley Hospital Learning Objectives 1) Understand that cancer is a disease of abnormal gene function and expression: Understand the concept of carcinogenesis; and that it is a multi-step process that involves genetic & epigenetic changes in many different processes of cellular division and regulation. 2) Understand the concept of oncogenes and tumour suppressor genes: What are the mechanisms involved in oncogenic activation & their potential to cause cancer? Understand how these genes act in a dominant transforming way. What are the functions of a tumour suppressor gene? Describe Knudson’s Two-Hit Hypothesis using tumour suppressor genes as an example. 3) Understand the underlying principles of the hallmarks of cancer and be able to give examples of these. Lecture Outline  Definition of cancer Overview of History and Timeline of Significant Events Cancer Classification Aetiology Carcinogenesis Brief overview of the cell cycle and regulatory systems  Cancer-associated genes • Proto-oncogenes and oncogenes Mechanisms of oncogene activation (mutations/amplification/rearrangements)  • Tumour suppressor genes • DNA Mismatch –Repair Genes Hallmarks of cancer Definition of Cancer • • • • • • • Disease of multicellular organisms Abnormal proliferation of cells Invasion of local tissue can metastasize Can cause significant morbidity/death Abnormal gene function Dysregulation of proliferation, differentiation & cell death Clonality or tumour cell population is favoured Cancer Genetics  Definition of cancer Overview of History and Timeline of Significant Events Cancer Classification Aetiology Carcinogenesis Brief overview of the cell cycle and regulatory systems  Cancer-associated genes • Proto-oncogenes and oncogenes Mechanisms of oncogene activation (mutations/amplification/rearrangements)  • Tumour suppressor genes • DNA Mismatch –Repair Genes Hallmarks of cancer Theoi Project Copyright © 2000 - 2008, Aaron J. Atsma, New Zealand History of Cancer (Karkinos) ~ 1600BC Heracles, the Hydra & the Crab, Athenian black-figure lekythos C5th B.C., Musée du Louvre, Paris ~ 300BC Cancer – Timeline of advances in cancer research 1960 Philadelphia chromosome 1970 First oncogene, src 1971 Knudson’s “2-Hit” Hypothesis 1979 Tp53 gene 1980’s The role of cyclins & cyclin-dependent kinases 1983 Polymerase chain reaction (PCR) 1984 Epstein Barr virus (EBV) 1990 FDA-approved gene therapy 1994 - 2003 Human Genome Project 2001 1st Targeted Therapy – Imatinib mesylate CML 2000s – Next-generation sequencing 2017 – CAR T-cell Therapies Cancer Genetics  Definition of cancer Overview of History and Timeline of Significant Events Cancer Classification Aetiology Carcinogenesis Brief overview of the cell cycle and regulatory systems  Cancer-associated genes • Proto-oncogenes and oncogenes Mechanisms of oncogene activation (mutations/amplification/rearrangements)  • Tumour suppressor genes • DNA Mismatch –Repair Genes Hallmarks of cancer Definition of Cancer • • • • • • • Disease of multicellular organisms Abnormal proliferation of cells Invasion of local tissue can metastasize Can cause significant morbidity/death Abnormal gene function Dysregulation of proliferation, differentiation & cell death Clonality or tumour cell population is favoured Cancer Classification 1) Primary site in the body where the cancer 1st developed: • Lungs ..... 8664 deaths in 2022 in Australia • Skin • Colon and Rectum • Female Breasts • Cervix and Uterus Simply indicated where the cancer is located but doesn’t specify the type of tissue involved 2) Histological type – tissue type in which the cancer originates: • Carcinomas • Sarcomas • Leukaemia • Lymphoma • Myeloma • Mixed Types Aetiology  Environmental factors that can lead to genetic changes & cause cancer to develop: Chemicals Radiation Diet and Exercise Infection – Retroviruses Physical Agents Hormones Terminology  “hereditary” cancers Chromosomes v rare, germline origin  “familial” Gene Locus position on chros clusters in families, combination germline & acquired  “acquired” (sporadic) not germline origin, all acquired mutations Alleles variant forms at same locus • Proliferation – cell growth & division • Dysregulation – impairment of a physiological regulatory mechanism Structure of a gene www.tokresource.org Transcription/gene expression = process by which a protein is formed from the genes that encode it Cancer Genetics  Definition of cancer Overview of History and Timeline of Significant Events Cancer Classification Aetiology Carcinogenesis Brief overview of the cell cycle and regulatory systems  Cancer-associated genes • Proto-oncogenes and oncogenes Mechanisms of oncogene activation (mutations/amplification/rearrangements)  • Tumour suppressor genes • DNA Mismatch –Repair Genes Hallmarks of cancer Carcinogenesis Process by which normal cells are transformed into cancer cells. Characterized by changes at the: • Cellular level • Genetic level • Epigenetic level • Through abnormal cell division Theories of Carcinogenesis  Knudson’s Two-Hit Hypothesis  The Multi-Step Nature of Cancer – Vogelstein B and Kinzler KW 1993  Somatic Mutation Theory (SMT) vs. Tissue Organization Field Theory (TOFT)  Variant theories – Stem cell Model Epigenetic variations Knudson’s Two-Hit Hypothesis 1. it is pecially true for recessive nature… 2. cancer was a multi step process (single) 1)Is especially true for the recessive nature of tumour suppressor genes 2) Multi-step process that involves > 1 mutation Multi-step nature of carcinogenesis metabolism&repair processes altered Chemical Carcinogen [Irreversible but not yet cancer] Promoters contribute by mechanisms cells to acquire more mutations [Form benign or precancerous lesions] [Selection/growth advantage] Multi-step tumour progression [Epigenetic changes. Local invasion/metastases to distant parts] [DNA instability increases with each step] Principles of Cancer Biology. Kleinsmith LJ. 2006. Pearson Benjamin Cummings Theories of Carcinogenesis SMT vs. TOFT  Somatic mutation Theory (SMT) Carcinogenic agents new mutations or affect cell growth, differentiation or function.  already mutated genes Tissue Organization Field Theory (TOFT) Carcinogenic agents disrupt interactions between cells that maintain the tissue architecture; it’s organization, repair and regulation. Variant updates of SMT and TOFT  Stem cell model  Epigenetic modifications – genetic changes other than mutations that involve:  epigenetic factors:  proteins/molecules e.g. growth factors  adjacent stromal cells e.g. endothelial cells  extracellular matrix (ECM) framework surrounding tumour cells  epigenetic mechanisms e.g. hypermethylation of genes Example: modification of an epigenetic mechanism e.g. hypermethylation of TAF (growth regulation) gene, as seen in breast ca M H3 methylation Unmethylated state M Laird P W Hum. Mol. Genet. 2005;14:R65-R76 Methylated state Function Biochemistry Genetics Genes Proteins Molecular Biology Art Writ, Five New Genes That Affect CAD, Discovered Heal Blog, Sept 2011 Take home message of carcinogenesis…..  Knudson’s 2 hit theory  Genetic mutations  Multi-step of carcinogens  Epigenetic changes Cancer Genetics  Definition of cancer Overview of History and Timeline of Significant Events Cancer Classification Aetiology Carcinogenesis Brief overview of the cell cycle and regulatory systems  Cancer-associated genes • Proto-oncogenes and oncogenes Mechanisms of oncogene activation (mutations/amplification/rearrangements)  • Tumour suppressor genes • DNA Mismatch –Repair Genes Hallmarks of cancer Mitosis M G2 The cell cycle G1 G0 Interphase S Checks & Balances √ Growth √ Differentiation √ Apoptosis Cell cycle regulation Cyclins Growth factors & growth factor receptors Signalling transduction pathways Transcriptional regulation Apoptosis Checkpoints Telomeres and telomerase Extracellular matrix DNA Mismatch repair Signal transduction pathways.svg Cancer Genetics  Definition of cancer Overview of History and Timeline of Significant Events Cancer Classification Aetiology Carcinogenesis Brief overview of the cell cycle and regulatory systems  Cancer-associated genes • Proto-oncogenes and oncogenes Mechanisms of oncogene activation (mutations/amplification/rearrangements)  • Tumour suppressor genes • DNA Mismatch –Repair Genes Hallmarks of cancer Cancer-associated genes  Proto-oncogenes and oncogenes Mechanisms of oncogene activation  Tumour suppressor genes  DNA mismatch-repair genes Proto-oncogenes and oncogenes Proto-oncogene – regulates cell growth & differentiation • • potential to become cellular oncogene Involved in signal transduction & execution of mitogenic signals e.g. myc involved in cell regulation - codes for transcription factor, eg’s ras, wnt Oncogene ( or cellular oncogene c-onc) – potential to increase the malignancy of a cell, once it becomes activated, constitutively expressed • eg’s c-myc, k-ras Classification of Oncogenes Function Mechanism of Action Examples Growth factors Overexpression – an oncogene may cause a cell to secrete growth factors even though it usually doesn’t. This induces uncontrolled proliferation (autocrine loop) and proliferation of neighbouring cells. c-sis Growth Factor Receptors (Receptor Tyrosine Kinases) Overexpression or amplification – receptor kinases add phosphate groups to the amino acid tyrosine in target proteins that can cause cancer by switching the receptor permanently on without signals from outside the cell. Epidermal growth factor receptor (EGFR) or erb-B1 in lung, breast, stomach cancers, platelet-derived growth factor receptor (PDGFR), and vascular endothelial growth factor receptor (VEGFR), HER2/neu Cytoplasmic tyrosine kinases Translocations leading to fusion hybrid protein Src-family, Syk-ZAP-70 family, and BTK family of tyrosine kinases, the Abl gene in CML - Philadelphia chromosome Cytoplasmic Serine/threonine kinases and their regulatory subunits Point mutations, amplifications or translocations Raf kinase, Cyclin D1 or CDK4 Regulatory GTPases Point mutations leading to deregulated overactivity Ras in many common cancers, lung, colon, pancreas Transcription factors Point mutations, amplifications or translocations c-myc amplification in dmins in AML, Mechanisms of oncogene activation 1) Mutations 2) Gene amplification 3) Chromosomal rearrangements Mechanisms of oncogene activation Mutations  alter structure of proto-oncogene  dominant gain-of-function   oncogene dominant means it need 1 allele to express itself. involve protein regulatory regions of the mutated protein uncontrolled continuous activity types of mutations: • • • • Point mutations Deletions Insertions Integration of proviral DNA from a retrovirus Mechanisms of oncogene activation Example of a point mutation DNA sequence analysis of K-ras gene at codon 12 K-ras involved in 30 -40% cancer g g t g wild type of K-ras g g g a t g g G to A mutation Sharaf HM, El- Kinawy NS, Mahmoud AO, Ali MA. Detection of a Point Mutation at Codon 12 of the Kirsten-Ras (K-ras) Oncogen in Myelodysplastic Syndrome . WebmedCentral HAEMATOLOGY2012;3(5):WMC003357 Mechanisms of oncogene activation Example of a deletion Chros 9 If 1 copy is deleted, it leads to expression/change of function (due to dominant gain-of function) Eg. “Oncogenic activation of the Notch1 gene by deletion of its promoter in Ikaros-deficient T-ALL” Robin Jeannet et al BLOOD, 16 DECEMBER 2010 VOLUME 116, NUMBER 25 http://www.bloodjournal.org/content/116/25/5443?sso-checked=true Note: gene dosage effect associated with deletions where obvious deletions in chromosomes represent an increased number of genes deleted eg 5q- syndrome in MDS Notch 1 gene Example of a mutation involving integration of proviral DNA from a retrovirus tax Retrovirus = RNA virus (can reverse transcribe RNA into proviral DNA) e.g. HTLV-1 activate TAX gene adult T-cell leukaemia/lymphoma TAX involved in proliferation Mechanisms of oncogene activation 1) Mutations 2) Gene amplification 3) Chromosomal rearrangements Mechanisms of onogene activation Gene Amplification = oncogene Mechanism: repeated copying in DNA replication process expansion in copy number deregulated cell growth increase in gene expression onc present Example of gene amplification resulting in dmins Amplification can result in: • double minutes (d-mins) • homogenously staining regions (hsrs) Amplified regions can contain > 100’s copies e.g. c-myc is amplified in small-cell lung ca, breast/ovarian ca and leukaemias. Example of gene amplification resulting in dmins Amplification can result in: • double minutes (d-mins) • homogenously staining regions (hsrs) Amplified regions can contain > 100’s copies e.g. c-myc is amplified in small-cell lung ca, breast/ovarian ca and leukaemias. FISH image of c-myc amplification in d-mins Case study example of double minutes (dmins) Case 1: Acute Myeloid Leukaemia patient with double minutes – metaphase Case 1: AML patient with double minutes – karyotype Case study examples of double minutes (dmins) Case 1: AML patient with double minutes – Interphase FISH showing myc amplification using MYC-IGH dual colour dual fusion LSI probe (MYC R IGH G) Case study example of double minutes (dmins) Case 1: AML patient with double minutes – directed metaphase FISH showing myc amplification using MYC-IGH dual colour dual fusion LSI probes (MYC R IGH G) Case study examples of double minutes (dmins) Case 2: AML patient with double minutes – interphase FISH showing KMT2A amplification KMT2A breakapart probe (5’ proximal R 3’ distal G ) Clone 1 Case study examples of double minutes (dmins) Case 2: AML patient with double minutes – interphase FISH showing KMT2A amplification KMT2A breakapart probe (5’ proximal R 3’ distal G ) Clone 2 Case study example of homogeneously stained regions (hsrs) Case 3: AML patient with a ring 3 chromosome showing a hsr - karyotype Case study example of homogeneously stained regions (hsrs) Case 3: AML patient with a ring 3 chromosome showing amplification of the MECOM gene – directed metaphase FISH using MECOM breakapart probe (5’ distal G 3’ proximal R) Mechanisms of oncogene activation 1) Mutations 2) Gene amplification 3) Chromosomal rearrangements Mechanisms of oncogene activation Chromosomal rearrangements Recurrent chromosomal rearrangement are often detected in haematological malignancies & some solid tumours Types of recurrent rearrangements: • chromosomal translocation – reciprocal exchange • Inversions – segment reversed end to end When these rearrangements happen, oncogenes can be activated by: 1) De regulated expression of oncogenes via regulatory control of an immunoglobulin gene IGH@ Proto-onco/onc is moved close to an immunoglobulin gene and falls under its control deregulated expression neoplastic transformation OR 2) Formation of novel hybrid fusion genes with transforming activity Juxtaposition of 2 different genes to form a novel fusion gene codes for chimeric protein transforming activity Types of abnormalities detected in haematological malignancies  Numerical Gains/losses (egs trisomies, monosomies) eg trisomy 8 (clone = at least 2 cells) monosomy 7 (clone = at least 3 cells)  Structural – any structural aberration (clone = at least 2 cells) Intrachromosomal Inversions – segments within a chromosome, reversed end to end duplications/deletions/insertions Others eg rings, markers Interchromosomal Translocations – reciprocal Insertions Mechanisms of oncogene activation Chromosomal rearrangements Recurrent chromosomal rearrangement are often detected in haematological malignancies & some solid tumours. Types of recurrent rearrangements: • chromosomal translocation – reciprocal exchange • Inversions – segment reversed end to end When these rearrangements happen, oncogenes can be activated by: 1) De regulated expression of oncogenes via regulatory control of an immunoglobulin gene IGH@ Proto-onco/onc is moved close to an immunoglobulin gene and falls under its control deregulated expression neoplastic transformation OR 2) Formation of novel hybrid fusion genes that encodes for a chimeric protein with transforming activity Juxtaposition of 2 different genes to form a novel fusion gene codes for chimeric protein transforming activity Mechanisms of oncogene activation 1)De regulated expression of oncogenes via regulatory control of an immunoglobulin gene IGH Case study 1: Patient with Mantle Cell Lymphoma t(11;14)(q13;q32) G-band and directed metaphase FISH using IGH-CCND1 dual colour dual fusion probe (CCND1 R, IGH G) CCND1(aka BCL1) involved in G1 to S transition Norback H et al, Cytogenetics at theWaisman Center, Atlas of Genetics and Cytogenetics in Oncology and Haematology Mechanisms of oncogene activation 1)De regulated expression of oncogenes via regulatory control of an immunoglobulin gene IGH Case study 2: Patient with Acute Lymphoblastic Leukaemia t(11;14)(q23;q32) - karyotype CCND1(aka BCL1) involved in G1 to S transition Norback H et al, Cytogenetics at theWaisman Center, Atlas of Genetics and Cytogenetics in Oncology and Haematology 1)De regulated expression of oncogenes via regulatory control of an immunoglobulin gene IGH Case study 2: Patient with ALL t(11;14)(q23;q32) - directed metaphase FISH using IGH breakapart FISH (3’p, 5’d) 5’distal IGH on der(11)t(11;14) 3’proximal IGH on der(14)t(11;14) Unrearranged IGH on normal 14 Norback H et al, Cytogenetics at theWaisman Center, Atlas of Genetics and Cytogenetics in Oncology and Haematology 1)De regulated expression of oncogenes via regulatory control of an immunoglobulin gene IGH Case study 3: Patient with Burkitt Lymphoma t(8;14)(q24;q32) - karyotype 1)De regulated expression of oncogenes via regulatory control of an immunoglobulin gene IGH Case study 3: Patient with Burkitt Lymphoma t(8;14)(q24;q32) – directed metaphase FISH using IGH breakapart FISH (3’p, 5’d) 5’distal IGH on der(8)t(8;14) 3’proximal IGH on der(14)t(8;14) Unrearranged IGH on normal 14 Mechanisms of oncogene activation 2) Formation of novel hybrid fusion genes that encodes for a chimeric protein with transforming activity Case study: CML patient with t(9;22)(q34;q11.2) by G-band and directed metaphase FISH using dual colour dual fusion BCR-ABL1 probe (ABL1 R, BCR G) BCR-ABL1 Classic e.g. of t(9;22) in CML ABL1 gene encodes tyrosine kinase activity Involved in cellular differentiation BCR located at 22q11 BCR::ABL1 fusion gene encodes chimeric protein Atlas of Genetics and Cytogenetics in Oncology and Haematology Cancer-associated genes  Proto-oncogenes and oncogenes Mechanisms of oncogene activation  Tumour suppressor genes  DNA mismatch-repair genes Tumour Suppressor genes Suppress cellular growth/survival when needed to prevent tumours forming. •  Outcomes triggered by tumour suppressor activation: • Arrest cell cycle to inhibit cell division • Induce cell cycle to DNA damage repair mechanisms • Promote apoptosis if damage cannot be repaired • Induce senescence Two most important tumour suppressor genes; TP53 and RB Other eg’s: APC, BRCA1, BRCA2 • Follow Knudson’s 2-Hit Hypothesis e.g. RB Usually recessive nature– both copies mutated before function is affected  The exception is TP53 it can be; recessive or dominant negative Recessive and Dominant Negative TP53 mutations Two normal TP53 genes. Homozygous recessive mutation Heterozygous recessive mutation. No TP53 produced No TP53 produced TP53 TP53 Dominant negative mutation. Altered TP53 Non-functional TP53 Adapted from Principles of Cancer Biology. Kleinsmith LJ. 2006. Pearson Benjamin Cummings. Take home message.... Difference between oncogenes & tumour suppressors Oncogenes Tumour suppressor genes Dominant-gain-of function Usually recessive nature Increase cell proliferation Inhibits cell proliferation Inhibit apoptosis Promotes apoptosis Take home message.... Oncogene activation 3 Mechanisms: 1) Mutation 2) Gene amplification 3) Chromosomal rearrangements by 2 mechanisms Cancer-associated genes  Proto-oncogenes and oncogenes Mechanisms of oncogene activation  Tumour suppressor genes  DNA mismatch-repair genes DNA Mismatch-Repair genes (same family as Tumour suppressor genes) • • The DNA mismatch-repair system normally recognizes and repairs errors that arise during replication and recombination e.g. insertions of nucleotides. But what happens if the repair is faulty? Results in ineffective repair • unstable genome What can go wrong with DNA Mismatch-repair genes? • Mutations • Hypermethylation of promoter regions of some of the genes e.g. mutation of hMSH2 gene causes faulty repair a lot of complex steps colorectal ca microsatellite instability Cancer Genetics  Definition of cancer Overview of History and Timeline of Significant Events Cancer Classification Etiology Carcinogenesis Brief overview of the cell cycle and regulatory systems  Cancer-associated genes • Proto-oncogenes and oncogenes Mechanisms of oncogene activation (mutation/amplification/rearrangements)  • Tumour suppressor genes • DNA Mismatch –Repair Genes Hallmarks of cancer Hallmarks of Cancer 2000 Hanahan and Weinberg 6 biological capabilities acquired by cancer cells: (1) Sustaining growth signalling (2) Evading growth suppressors (3) Resisting cell death (4) Enabling replicative immortality (5) Inducing angiogenesis (6) Activating invasion and metastasis 2011 sequel of 4 more 1) abnormal metabolic pathways 2) evading the immune system 3) chromosome abnormalities & unstable DNA (4) inflammation Hallmarks of Cancer (1) Sustaining growth signalling (2) Evading growth suppressors (3) Resisting cell death (4) Enabling replicative immortality (5) Inducing angiogenesis (6) Activating invasion and metastasis Hallmarks of cancer Sustaining Growth Signalling Cancer cells can sustain growth by: 1) producing their own growth factor molecules e.g. glioblastomas - PDGF 2) send their own growth signals  send their own signals to normal cells in ECM around tumour react and supply tumour with GF e.g. E-cadherin/catenin complex  receptor proteins at the cancer cell surface hyper responsive to usually limited supply growth signalling e.g. increased HER2/neu receptors in some breast cancers Outcome: circumvent limited pathway & keep growth signalling switched on Hallmarks of Cancer (1) Sustaining growth signalling (2) Evading growth suppressors (3) Resisting cell death (4) Enabling replicative immortality (5) Inducing angiogenesis (6) Activating invasion and metastasis Hallmarks of cancer Evading Growth Suppressors    Function of a growth suppressor is to control growth (regulatory pathways/factors) Many of these are dependent on tumour suppressor genes eg RB and TP53 Defects in pathways/genes cancer cells able to resist inhibitory signals that would usually stop their growth cyclin D- CDK4(6) cyclin E-CDK2 cyclin A-CDK2 ATP Growth suppression pRB active pRB - Phos inactive PP1 Mutated RB gene pRB inactivated ADP Cell proliferation PP1 phosphatase growth suppressor evaded, proliferates Retinoblastoma Protein phosphatase type 1, the product of the retinoblastoma susceptibility gene, and cell cycle control. Rubin E et al. Frontiers in BioScience 3 d1209-19219, Dec 1998. Hallmarks of Cancer (1) Sustaining growth signalling (2) Evading growth suppressors (3) Resisting cell death (4) Enabling replicative immortality (5) Inducing angiogenesis (6) Activating invasion and metastasis Hallmarks of cancer BCL2 - oncogene on chromosme 18 Signal transduction pathways.svg Apoptosis = programmed cell death Different pathways regulating/effecting apoptosis (e.g. TP53 mediated/BCL2 regulated) Opportunities for cancer cells to resist apoptosis through defects in these pathways Hallmarks of cancer p53/BCL2 regulatory pathway to Apoptosis  BCL2 can: anti cell death function(BCL2 hyperphos’d) promotes cell death  cell lives cell dies TP53 can: promote cell death promote DNA repair Apotosis acts to control cancer cells but it can be overcome if: 1) Over expression of BCL2 (translocation, controlled by IGH) OR 2) Mutation/loss of TP53 Hallmarks of cancer Resisting Cell Death   Normal situation: normal cell P normal regulation Normal situation: DNA damaged cell (e.g. stressed/aged) P P Bcl-2 P cell lives apoptosis induced cell death Bcl-2 P  BUT........ Scenario 1) Over expression BCL-2::IGH Translocation proliferate Bcl-2 Bcl-2 Bcl-2 Bcl-2 Bcl-2 Damage sensor Scenario 2) No TP53 or altered mutation/loss TP53 Usually multistep TP53 mutated >50% cancers Hallmarks of Cancer (1) Sustaining growth signalling (2) Evading growth suppressors (3) Resisting cell death (4) Enabling replicative immortality (5) Inducing angiogenesis (6) Activating invasion and metastasis Hallmarks of cancer Enabling Replicative Immortality   Multiply forever! Normally: cells have limited # growth/division cycles before senescence is reached or a crisis phase leads to cell death So what causes some cells to bypass this?  Telomeres involved immortalization • • • Telomeres protect ends of chromosomes As cells reach end of lifespan, telomeres shorten genome instability/apoptosis Telomerase, maintains telomere length is almost absent in normal cells but in 90% immortalized cells, including cancer cells Genetic mechanisms are unclear, but a combination of changes occur: loss of TP53 and RB pathway function& activation of RAS or myc telomerase genomic stability multiply forever Hallmarks of Cancer (1) Sustaining growth signalling (2) Evading growth suppressors (3) Resisting cell death (4) Enabling replicative immortality (5) Inducing angiogenesis (6) Activating invasion and metastasis Hallmarks of cancer Inducing Angiogenesis  Formation of new blood vessels.  Balanced by inducers and inhibitors  e.g. Inducers VEGF-A which bind to receptors on endothelial cells Inhibitor TSP-1 regulated by TP53   For cancer cells to grow they need a blood supply. During carcinogenesis an “angiogenic switch” is tripped and remains on. Inducers & inhibitors control this switch. e.g. TP53 loss or mutation can dysregulate TSP-1 and induce angiogenesis. as seen in growth of breast and melanoma cancers Hallmarks of Cancer (1) Sustaining growth signalling (2) Evading growth suppressors (3) Resisting cell death (4) Enabling replicative immortality (5) Inducing angiogenesis (6) Activating invasion and metastasis Hallmarks of cancer Activating invasion and metastasis    Tissue invasion: localized Metastasis: distant areas attach to ECM/ conscript normal cells for support Activated by changes in molecules needed for cell adhesion: - cadherins & integrins e.g. E-cadherin – assemble epith cells sheets & maintain integrity mutation or of E-cadherin by some cancer cells cells to detach activates invasion and metastasis e.g. integrins - mediate cell attachment/integrity & send signals to regulate this, - involved in the motility of cells. expression of integrins have been correlated with metastatic progression in breast, prostate and lung ca. Genetic alteration in cadherins/integrins or factors that regulate/effect their pathways activation of invasion/metastasis Lecture Outline  Definition of cancer Overview of History and Timeline of Significant Events Cancer Classification Aetiology Carcinogenesis Brief overview of the cell cycle and regulatory systems  Cancer-associated genes • Proto-oncogenes and oncogenes Mechanisms of oncogene activation (mutations/amplification/rearrangements)  • Tumour suppressor genes • DNA Mismatch –Repair Genes Hallmarks of cancer Nature Reviews Cancer Summary Cancer Genetics Cancer clonality Affect various pathways/factors ( 6 hallmarks) Genomic Instability Epigenetic changes Growth advantage/selection Acquired mutations Outcome: dysregulation of growth/apoptosis/function Altered gene expression oncogene/tumour suppressor gene activated Acquired mutation Aetiological agent , 6 339 (May 2006) | doi:10.1038/nrc1899