* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Presentation
Cre-Lox recombination wikipedia , lookup
Gene expression profiling wikipedia , lookup
Genome (book) wikipedia , lookup
Transcription factor wikipedia , lookup
Cancer epigenetics wikipedia , lookup
Gene therapy of the human retina wikipedia , lookup
Nutriepigenomics wikipedia , lookup
Microevolution wikipedia , lookup
History of genetic engineering wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Designer baby wikipedia , lookup
Oncogenomics wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Point mutation wikipedia , lookup
Primary transcript wikipedia , lookup
Mir-92 microRNA precursor family wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
Oncogenes & tumour suppressors Bart Vanhaesebroeck Cell Signalling Group cell signalling regulates every aspect of a cell’s life & death cancer is a consequence of deregulated cell signalling growth factor growth factor receptor effector region (often a tyrosine kinase) CYTOPLASM intracellular transducers create 2nd messengers NUCLEUS transcription factors DNA transcription mRNA proteins proliferation (cell cycle progression) growth survival metabolism examples: cell cycle control DNA repair anti-apoptosis differentiation migration death (apoptosis) growth factor eg. epidermal growth factor (EGF) growth factor receptor eg. EGF-receptor (EGF-R) effector region (often a tyrosine kinase) intracellular transducers create 2nd messengers eg. - Ras - protein kinases (Tyr, Ser, Thr) NUCLEUS transcription factors eg. Myc, p53 DNA transcription mRNA proteins examples: cell cycle control : Rb, p16, CDKs DNA repair : ATM anti-apoptosis : Bcl2, Bad normal cell signalling is deregulated in cancer this deregulation can occur by • mutation • gene amplification • gene translocation • gene conversion •… cancer is a disease of DNA (1) chromosomes of a normal cell cancer is a disease of DNA (2) chromosomes of a cancer cell normal cell signalling is de-regulated in cancer this deregulation can occur in oncogenes - genes capable of inducing one or more characteristics of cancer cells - dominant gain-of-function: dominant in genetic terms: have an effect even if only one of the 2 cellular copies of the gene is altered - the normal versions of the genes are called ‘proto-oncogenes’ tumour suppressor genes - genes that inhibit tumour development = ‘brakes’ - recessive loss-of-function: recessive in genetic terms: both copies of the gene need to be inactivated (this is the ‘classical’ theory – emerging evidence suggests that this may not be true for all tumour suppressor genes, some (like PTEN; see later) are ‘haplo-insufficient’, and already ‘cause trouble’ if one copy is lost). growth factor eg. vascular endothelial growth factor (VEGF) growth factor receptor eg. EGF-receptor (EGF-R) effector region (often tyrosine kinase) intracellular transducers create 2nd messengers eg. - Ras - protein kinases (Tyr, Ser, Thr) NUCLEUS transcription factors eg. Myc, p53 DNA transcription mRNA proteins examples: cell cycle control : Rb, p16, CDKs DNA repair : ATM anti-apoptosis : Bcl2, Bad growth factor eg. vascular endothelial growth factor (VEGF) Avastin TM (Genentech) - blocks action of VEGF, key molecule in angiogenesis - approved by the FDA in combination with chemotherapy (intravenous 5-fluorouracil [5-FU]based chemotherapy) for treatment of people diagnosed with metastatic colorectal cancer for the first time examples of oncogenes Tyrosine kinases: EGF-Receptor family members, BcrAbl Intracellular signalling protein: Ras transcription factor: Myc anti-apoptotic protein: Bcl2 growth factor eg. vascular endothelial growth factor (VEGF) growth factor receptor eg. EGF-receptor (EGF-R) effector region (often tyrosine kinase) intracellular transducers create 2nd messengers eg. - Ras - protein kinases (Tyr, Ser, Thr) NUCLEUS transcription factors eg. Myc, p53 DNA transcription mRNA proteins examples: cell cycle control : Rb, p16, CDKs DNA repair : ATM anti-apoptosis : Bcl2, Bad oncogenes EGF-Receptor family members overexpressed & constitutively active in breast cancer target for (1) antibody therapy: eg. Herceptin (Genentech) = monoclonal antibody that binds the extracellular domain of the EGF-R family member HER2 inhibits the growth of cells that overexpress this EGF-R (2) tyrosine kinase inhibitor therapy: eg. IRESSA (Astra Zeneca) = small molecule that inhibits the activity of the intracellular kinase domain of the EGF-R resting normal cell receptor nucleus cell membrane = hormone or growth factor (courtesy of Dr. Rob Stein) stimulated normal cell gene activation cell survival & division (courtesy of Dr. Rob Stein) cancer cell spontaneous receptor dimerisation & activation gene activation cell survival & division (courtesy of Dr. Rob Stein) effect of = inhibitor of receptor kinase activity growth inhibition & cell death (courtesy of Dr. Rob Stein) deregulated signalling proteins are increasingly used for ’targeted therapies’ tumours seem to critically depend on some of these pathways : ‘Achilles heels’ examples of oncogenes (cont’d) Tyrosine kinases (cont’d) BcrAbl Philadelphia chromosome translocation = t(9;22) : fuses * part of the bcr gene from chromosome 22 with * part of the abl tyrosine kinase gene on chromosome 9 creates the BcrAbl fusion protein in which the Abl tyrosine kinase (1) has kinase activity (2) localised throughout the cells (not only in the nucleus as in normal cells) phosphorylation of substrates that proliferation & protect from apoptosis in chronic myelocytic leukemia (CML) target for Gleevec (Novartis) = tyrosine kinase inhibitor almost 100% remission in chronic phase of disease (but resistance appears to develop). growth factor eg. epidermal growth factor (EGF) growth factor receptor eg. EGF-receptor (EGF-R) effector region (often tyrosine kinase) intracellular transducers create 2nd messengers eg. - Ras - protein kinases (Tyr, Ser, Thr) NUCLEUS transcription factors eg. Myc, p53 DNA transcription mRNA proteins examples: cell cycle control : Rb, p16, CDKs DNA repair : ATM anti-apoptosis : Bcl2, Bad examples of oncogenes (cont’d) Ras = intracellular signalling protein small GTPase controls MAP kinase protein cascade important for proliferation & gene induction mutated & constitutively active in many cancers Myc = transcription factor - in Burkitt lymphoma due to Epstein-Barr Virus (EBV): virus carried by >90% of the world's population – in severely immune-suppressed patients EBV immune surveillance B-cell lymphomas How does Myc become activated? translocation of c-myc proto-oncogene into or near one of the immunoglobulin loci found in almost every case of Burkitt’s B-cell lymphoma in man (see lecture D. Linch & A. Khwaja) examples of oncogenes (cont’d) Bcl2 = anti-apoptotic protein = B-cell leukemia-2 (see lecture notes D. Linch & A. Khwaja) protects against cell death was the first ‘oncogene’ discovered which does not regulate proliferation initially identified as a translocation breakpoint common in many B-cell lymphomas as a result of this translocation, the bcl-2 gene comes under the control of the immunoglobulin heavy chain enhancer & is constitutively expressed in B-cells the resulting protection from apoptosis apparently permits the survival & accumulation of aberrant B-cells that ultimately give rise to lymphoid malignancies examples of tumour suppressor genes gene regulator: Rb transcription factor: p53 lipid phosphatase: PTEN tumour suppressor genes - genes that inhibit tumour development - classical theory: recessive (in genetic terms): both gene copies in the cell need to be inactivated before cancer can arise almost all genes in our cells are present in 2 redundant copies (one from mother & one from father): if one copy is lost, the other copy serves as a backup. In the case of tumour suppressor genes, this offers a measure of protection. loss-of-heterozygosity = LOH = loss of the 2nd allele of a tumour suppressor (by gene conversion, mutation, gene deletion etc) some people carry an inactivating mutation in a tumour suppressor gene in their sperm or eggs offspring is more prone to lose the 2nd allele (eg. by a so-called ‘sporadic’ mutation) predisposition to cancer. eg. familial retinoblastoma : carry mutations in Rb gene (see also lecture notes Dr. Daniel Hochhauser) growth factor eg. epidermal growth factor (EGF) growth factor receptor eg. EGF-receptor (EGF-R) effector region (often tyrosine kinase) intracellular transducers create 2nd messengers eg. - Ras - protein kinases (Tyr, Ser, Thr) NUCLEUS transcription factors eg. Myc, p53 DNA transcription mRNA proteins examples: cell cycle control : Rb, p16, CDKs DNA repair : ATM anti-apoptosis : Bcl2, Bad Rb = retinoblastoma first identified in the rare eye tumour retinoblastoma (occurs only up to the age of 6-7) - arises from retinoblasts: cells in the embryonic retina that will become photoreceptors - ‘sporadic’ form: afflicted children have no close relatives who have previously contracted this cancer ( familial form) Alfred Knutson theory (based on epidemiological studies): > sporadic form: the 2 mutations occur one after another (either during embryonic development of shortly after birth), in one of the cells of the retina extremely rare & occurs slighly later in life (mean age: 30 months) children mostly carry a single retinal tumour in one eye > familial form: all cells of the embryo carry 1 mutated allele of the Rb gene (including all cells of the retina). chance of loss of 2nd allele (LOH) frequency of retinoblastoma & occurs early (mean age: 14 months) often multiple tumours in both eyes Rb = retinoblastoma protein ‘pocket’ protein: binds & inhibits E2F transcription factors ‘super’ phosphorylation of Rb (by cyclin-dependent kinases that act in cell cycle) release of E2F from the DNA brake is gone allows transcription of genes important for cell cycle progression in normal cell: P P RB P P P RB E2F G1 RB E2F S E2F cyclin E c-Myc other G1 in Rb -/- cell: loss-of-expression of Rb brake is lost no brakes on cell cycle progression examples of tumour suppressor genes (cont’d) p53 = transcription factor in 50% of tumours: lost or (in most cases) mutated such that it can no longer bind DNA = ‘GUARDIAN OF GENOME’: ‘senses’ DNA damage, stress if damage is moderate: stalls cells in cell cycle until DNA is repaired if damage is severe: induces cell death programme STRESS (irradiation, hypoxia, anoxia, …) p53 cell cycle arrest cell death examples of tumour suppressor genes (cont’d) p53 (cont’d): Not entirely clear how p53 works, but a very plausible pathway goes as follows: damage of cellular DNA activation of ATM / DNA-PK (DNA-dependent protein kinase) phosphorylation of p53 increased p53 stability p53 accumulation & activation induction of * cell cycle inhibitors (such as p21) * apoptosis-inducing proteins (such as Bax, Fas-receptor, ..) * IGF-BP3 (a secreted binding protein for the survival factor IGF-1) EXPRESSION OF THESE NEGATIVE REGULATORS IS LOST UPON LOSS OF p53 example of a dose-dependent tumour suppressor gene: PTEN signalling by PI 3-kinases cytosol PI3K receptor PIP2 ras + PIP3 CELLS: protein kinases PDK1, Akt/PKB, Btk, Itk, … proliferation Akt adaptor proteins Gab1, Bam32, DAPP1, … cancer survival growth differentiation GEFs / GAPs for small GTPases of Rac, Ras, Arf families DISEASE: migration deregulation of PI3K signalling in cancer inflammation diabetes deregulation of PI3K signalling in cancer (cont’d) by loss of function of the PTEN tumour suppressor gene PIP3 = lipid phosphatase : when inactivated PI3K pathways ‘on’ PIP2 germline PTEN mutations in many in some hamartoma sporadic cancers syndromes e.g. glioblastoma, e.g. Cowden syndrome endometrium, … PTEN +/- mice: develop cancer with 100% penetrance under those conditions, the wild-type PTEN allele is retained, and only the dose of PTEN enzyme is altered Apparently, lowering the dose of a tumour suppressor gene can already have dire effects for cancer development, and it is thus not always necessary to lose BOTH copies of a tumour suppressor gene !!! (( Knutson theory) summary: oncogenes and tumour suppressor genes can alter every step of cellular signalling growth factor eg. epidermal growth factor (EGF) growth factor receptor eg. EGF-receptor (EGF-R) effector region (often tyrosine kinase) intracellular transducers create 2nd messengers eg. - Ras - protein kinases (Tyr, Ser, Thr) NUCLEUS transcription factors eg. Myc, p53 DNA transcription mRNA proteins examples: cell cycle control : Rb, p16, CDKs DNA repair : ATM anti-apoptosis : Bcl2, Bad THE END (thank you for your attention)