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Tumor genetics. Minna Thullberg. minna.thullberg@labmed.ki.se. 08-585 87985. Break. Basic concepts of carcinogenesis. Cancer is a disease of the genes. Phenotypes of cancer cells. What is an oncogene. What is a tumor suppressor gene. Inherited versus sporadic cancer.
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Tumor genetics Minna Thullberg minna.thullberg@labmed.ki.se 08-585 87985
Break Basic concepts of carcinogenesis Cancer is a disease of the genes Phenotypes of cancer cells What is an oncogene What is a tumor suppressor gene Inherited versus sporadic cancer The molecular pathway concept Discussion and microarray Summary of the most important stuff
nucleus cell M chromosomes G1 G2 R X S G0 (t) Do not form tumors Terminally differentiated Cells in arrest G0 (i) Latent ability to regenerate Form tumors occasionally Dividing cells Form tumors with highest frequency Cells in the cell cycle
Chromosome 5q 12p 18q 17p : Alteration: . mut or loss mut loss loss Gene: APC K-ras . DCC p53 DNA other hypo alterations methylation Intermediate Late Normal Hyperprolifer - Early Carcinoma Metastasis adenoma adenoma adenoma epithelium ating epithelium Vogelstein 1990
Phenotypes of cells in a tumor Loss of Differentiation Increased Proliferation Heterogeneity All tumors seemto be different
Common characteristics of cancer cells Increased cell proliferation due to * Growth without growth factors * Insensitivity to growth inhibitors Resistance to apoptosis (committed cell death) Indefinite lifespan= limitless replicative potential Genetic instability due to e.g. Protection against apoptosis or defect DNA repair Sustained angiogenesis In the invasive tumor Tissue invasion metastasis
Proliferation Growth stimulation Growth inhibition e.g. Growth factors e.g. Growth inhibitors Growth factor receptors Growth inhibitor receptors GTPases kinases Adhesion e.g. Extracellular matrix Cell-cell contact GTPases Signal transduction Contact receptors kinases Gene transcription Transcription factors Contact inhibition Cell-cell contact
Intracellular stress Extracellular stress Arrest or Apoptosis Cellular response of STRESS Protease cascade apoptosis caspase DNA damage HEAT Chemical imbalance caspase Cell cycle arrest Cytokines Ca2+ concentration Stress receptor Stress sensor p53 ATM P53 and/or ATM trigger arrest or apoptosis upon DNA damage
Telomeres protect the end of chromosomes Telomere tandem Parslow M
The telomeres get shorter for each round of replication Until a certain limit when the cell stops to divide Cell division with too short telomeres induces gene instability Stem cells and most cancer cells express TELOMERASE an enzyme which synthesize telomeres and induces unlimited life-span
What is an oncogene? Induces proliferation Induces transformation or Induces resistance to apoptosis Upregulated in human tumors A Proto-oncogene can become an oncogene by a genetic change Viral oncogenes (HPV)
Proto-oncogenes are: Growth factors Growth factor receptors Signal transduction proteins (kinases, G-proteins) Transcription factors Cell cycle proteins Inhibitors of apoptosis Telomerase?
Proliferation Growth stimulation Growth inhibition e.g. Growth factors e.g. Growth inhibitors Growth factor receptors Growth inhibitor receptors GTPases kinases Adhesion e.g. Extracellular matrix Cell-cell contact GTPases Signal transduction Contact receptors kinases Gene transcription Transcription factors Contact inhibition Cell-cell contact
Proto-oncogenes are transformed into oncogenes by: Activating mutations Translocations Transactivation Gene amplification Integration of virus
Genetic changes can be triggered by From living: DNA replication Metabolism creating reactive metabolites Stress from outside: UV light, smoking, chemicals
A Tumor suppressor is normally controlling cell growth or apoptosis And is lost or inactivated in cancer
Normal situation mother father 2 alleles functional proteins Tumor suppressor
Further genetic change in the second allele gene deletion NO functional proteins 2 genetic hits disease only defect proteins Tumor suppressor Inherited or spontaneous genetic change mother father mutation defect proteins functional proteins
Mechanisms of tumor suppressor gene inactivation Inactivating mutations Gene deletions Viral oncogenes Promotor silencing
Viral oncogenes e g in HPV express proteins which bind and inactivate p53 and pRb two guards of apoptosis and cell proliferation Changes in the structure of a gene’s promotor can lead to silencing of that gene and no protein will be expressed
Inherited cancer Inherited predisposition for tumor disease occurs typically through a mutation in a tumor suppressor gene The tumor develops when the second allele is also deleted or inactivated. In spontaneous developed tumors there need to be two hits in the tumor suppressor genes Which take longer time
Examples of inherited cancer ”syndromes” Retinoblastom(retina) pRb cell cycle control Polyposis Coli (colon) APC differentiation Ataxia Telangiectasi (general) ATM DNA repair Breast Cancer BRCA1, BRCA2 DNA repair Melanoma p16 cell cycle
The Cell Cycle G0 nucleus cell M chromosomes G1 G2 R X S
Cyclin B-CDC2 G0 M p16 Cyclin A-CDC2 G1 G2 Cyclin D-CDK4 Cyclin D-CDK6 X R S Cyclin E-CDK2 Cyclin A-CDK2
-Gene amplification -Gene deletion -Chromosomal rearrangement -Inactivating mutations - Proviral integration - Promotor silencing by -Protein stabilisation DNA methylation p16 P P -Gene deletion P -Loss of function mutations -Functional inactivation by viral oncoproteins cyclin D cdk 4/6 -Gene amplification -Loss of p16 binding Rb Rb
As for the geneticreprogramming of this integrated circuit in cancer cells, some of the genes knownto be functionally altered are highlighted in red. Hanahan and Weinberg, Cell, 2000
Summary Cancer develops stepwise through genetic changes Several genes are affected and it seems like all tumors are different An oncogene promote tumor growth A tumor suppressor normally control cell growth, or apoptosis but it is functionally lost in tumors
Common characteristics of cancer cells Increased cell proliferation due to * Growth without growth factors * Insensitivity to growth inhibitors Resistance to apoptosis (committed cell death) Indefinite lifespan= limitless replicative potential Genetic instability due to e.g. Protection against apoptosis or defect DNA repair Sustained angiogenesis In the invasive tumor Tissue invasion metastasis