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Tumor viruses

Tumor viruses. Tumor viruses. Viruses can cause bening or malignant tumors in many species of animals A few viruses are associated with human tumors. Malignant transformation of cells. Altered morphology Altered growth control Altered cellular properties Altered biochemical properties

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Tumor viruses

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  1. Tumor viruses

  2. Tumor viruses • Viruses can cause bening or malignant tumors in many species of animals • A few viruses are associated with human tumors

  3. Malignant transformation of cells • Altered morphology • Altered growth control • Altered cellular properties • Altered biochemical properties can be induced by tumor viruses

  4. Tumorigenesis • Provirus:thegenesenterthecellbyinfectionbytumorvirus • Oncogene: • Viralor • alreadypresent in thecell cellularoncogenes(c-onc) areactivatedbyvirusestooverproducethegrowthfactors • Tumorsupressor gene (p53):inactivation of this gene • Micro-RNA genes

  5. Human Tumor viruses • RNA viruses: • Human T-cell lymphotropic virus(HTLV-I): • Adult acute T-cell lymphocytic leukemia (ATLL) • No viral oncogene (different from animal tumor retroviruses) • Tax and rex regulatory genes (complex retrovirus) • Incubation period is long

  6. Tumor viruses • Humanpapillomavirus: • E6 and E7 genes • Encodeproteinsthatinterferewith p53 and Rb(retinoblastom) tumorsupressorgenes (inactivation) • Mostlythe HPV(especiallyhighlyoncogenictypes 16 and 18) is integratedintocellular DNA

  7. Tumor viruses • EBV: • Induces B cell proliferation • Activation of a cellular oncogene • Burkitt lymphoma: c-myc oncogene in chromosome 8 is translocated to14 chromosome where large amounts of c-myc RNA are synthesized.

  8. Tumor viruses • HBV: • Primer hepatocellular carcinoma:integration may activate an oncogen • HCV: • Chronic infection • HHV-8: • ?

  9. Animal tumor viuses • DNA Viruses: • SV40 • Adenovirus • Poxviruse • RNA viruses • Retroviruses: viral oncogene(highly oncogenic) No evidence that they cause tumors in humans

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