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21 Cards in this Set
- Front
- Back
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What is a neoplasm?
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A neoplasm is an abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the normal tissue and persists in the same excessive manner after cessation of the stimuli which evoked the change. It is purposeless, preys on the host, and is virtually autonomous (not dependent on the host cell).
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What are the primary causes of cancer?
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1. carginogens
2. radiation 3. viral (RNA or DNA) 4. inherited predisposition |
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What characteristic is common among all tumor viruses?
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They have a common ability to cause cancer.
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What type of genome do most tumor viruses have?
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DNA or generate a DNA intermediate
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What is malignant transformation?
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the process by which cells acquire the properties of cancer (changes in the growth properties, altered morphology, cellular properties or biochemical properties)
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What is a proto-oncogene?
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A proto-oncogene is a normal gene that can become an oncogene due to mutations or increased expression. The resultant protein may be termed an oncoprotein. (e.g. VEGFR, myc, Ras protein)
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What is an oncogene?
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An oncogene is a gene that is responsible for the normal growth and differentiation of cells but with the potential to cause cancer. They are often mutated or expressed at high levels.
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What is the difference between direct transforming viruses and slow transforming viruses?
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Direct transforming viruses carry an oncogene with them.
Slow transforming viruses do not carry an oncogene. |
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What is the Provirus model?
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A concept of viral tumorigenesis that claims that the genes enter the cells at the time of infection by tumor virus. (e.g. SV40 virus encoded large T antigen is sufficient to induce transformation)
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What is the Oncogene model?
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A concept of viral tumorigenesis that claims that carcinogens like viruses activate cellular oncogenes to overproduce growth factors critical to developing cancer. (e.g. EBV induced B cell proliferation increases the likelihood of activation of cellular oncogene)
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What viral families do the tumor causing viruses belong to?
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–Papillomavirus (DNA)
–Herpesviridae (DNA) – Hepadnaviridae (DNA) – Retroviridae (RNA with DNA intermediate) – Flaviviridae (RNA) |
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What are the viral oncoproteins of human papalloma viruses? What are their cellular targets?
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E6 (p53) and E7 (Rb)
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What viral proteins are encoded by HTLV that play a critical role in the initiating oncogenesis?
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tax and rex
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What mechanisms does HCV use to induce oncogenesis?
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Slow Transforming mechanism; the constant regeneration of hepatic cells due to chronic inflammation in the liver results in hepatic cellular carcinoma.
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Can viruses cause cancer in animals and humans?
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Yes. (Adenoviruses can cause cancer in animals. Also Papovavirus, SV40 in monkeys. Many viruses result in cancer in humans.)
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What is the only requirement for transformation by a virus?
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Only viral gene expression, not replication of the viral genome or production of viral progeny, is required for transformation. (typically cancer forms in non-permissive cells)
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What is required to develop viral carcinogenesis? |
Mutation/increased expression of pronto-oncogene and mutation to the tumor suppression gene are both required at the same time to develop viral carcinogenesis. (one mutation is not enough, there needs to be at least 3-8 mutations) |
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What viruses are known to cause cancer? What forms of cancer do they cause? |
- EBV (HHV-4) Infectious mononucleosis, Hodgkin’s lymphoma, Burkitt’s lymphoma, nasopharyngeal carcinoma - KSHV (HHV-8) Kaposi’s sarcoma (KS), primary effusion lymphoma (PEL), multicentric Castleman disease (MCD) - HPV (cervical cancer) - HBV (Hepatocellularcarcinoma (hepatoma)) - HTLV (leukemia and lymphoma) - HCV (Hepatoma) |
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What are the oncoproteins of Herpesvirus EBV? What is its cellular target?
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LMP1 (TRAFs)
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Do animal viruses cause cancer in humans?
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No.
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What are some animal tumor causing viruses?
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Papovavirus (eg., SV40, JC virus)
adenovirus, herpesvirus (eg., Marek’s disease virus) retroviruses (avian sarcoma viruses, eg., Rous sarcoma virus; avian leukemia viruses; murine sarcoma viruses, feline leukemia virus) |
