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Tumor genetics

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

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  1. Tumor genetics Minna Thullberg minna.thullberg@labmed.ki.se 08-585 87985

  2. 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

  3. 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

  4. Cancer is a genetic disease which develops stepwise

  5. 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

  6. Chernoff J

  7. Phenotypes of cells in a tumor Loss of Differentiation Increased Proliferation Heterogeneity All tumors seemto be different

  8. 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

  9. 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

  10. 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

  11. Parslow M

  12. Telomeres protect the end of chromosomes Telomere tandem Parslow M

  13. 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

  14. 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)

  15. Proto-oncogenes are: Growth factors Growth factor receptors Signal transduction proteins (kinases, G-proteins) Transcription factors Cell cycle proteins Inhibitors of apoptosis Telomerase?

  16. 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

  17. Proto-oncogenes are transformed into oncogenes by: Activating mutations Translocations Transactivation Gene amplification Integration of virus

  18. Genetic changes can be triggered by From living: DNA replication Metabolism creating reactive metabolites Stress from outside: UV light, smoking, chemicals

  19. A Tumor suppressor is normally controlling cell growth or apoptosis And is lost or inactivated in cancer

  20. Normal situation mother father 2 alleles functional proteins Tumor suppressor

  21. 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

  22. Mechanisms of tumor suppressor gene inactivation Inactivating mutations Gene deletions Viral oncogenes Promotor silencing

  23. 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

  24. 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

  25. 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

  26. The Cell Cycle G0 nucleus cell M chromosomes G1 G2 R X S

  27. 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

  28. -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

  29. 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

  30. 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

  31. 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

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