Tumor viruses
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Tumor viruses. Tumor viruses. Viruses can cause beningn 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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Tumor viruses

Tumor viruses


Tumor viruses1

Tumor viruses

  • Viruses can cause beningn or malignant tumors in many species of animals

  • A few viruses are associated with human tumors


Malignant transformation of cells

Malignant transformation of cells

  • Altered morphology

  • Altered growth control

  • Altered cellular properties

  • Altered biochemical properties

    can be induced by tumor viruses


Tumorigenesis

Tumorigenesis

  • Provirus:thegenesenterthecellbyinfectionbytumorvirus

  • Oncogene: alreadypresent in thecell

    cellularoncogenes(c-onc) areactivatedbyvirusestooverproducethegrowthfactors

  • Tumorsupressor gene (p53):inactivation of this gene

  • Micro-RNA genes


Tumor viruses2

Tumor 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


Tumor viruses3

Tumor viruses

  • Humanpapillomavirus:

    • E6 and E7 genes

    • Encodeproteinsthatinterferewith p53 andRb(retinoblastom) tumorsupressorgenes

    • Mostlythe HPV(especiallyhighlyoncogenictypes 16 and 18) is integratedintocellular DNA


Tumor viruses4

Tumor viruses

  • EBV:

    • Ä°nduces 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.


Tumor viruses5

Tumor viruses

  • HBV:

    • Primer hepatocellular carcinoma:integration may activate an oncogen

  • HCV:

    • Chronic infection

  • HHV-8:

    • ?


Animal tumor viuses

Animal tumor viuses

  • DNA Viruses:

    • SV40

    • Adenovirus

    • Poxviruse

  • RNA viruses

    • Retroviruses

      No evidence that they cause tumors in humans


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