Virology
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	Spring, 2004 Lecture Outline 5/11 TUMORIGENESIS AND TUMOR VIRUSES Intro: neoplasm = new tissue = tumor organized tumor c no potential to spread = benign disorganized tumor c potential to spread = malignancy spread to other sites = metastasize transformation: complex set of events- initiation, promotion, transformation- stable changes of chromosomes viral tumor formation: some viruses stim cell proliferation s other alterations = benign E.g.: warts by papilloma, some tumors by poxviruses malignant: cell proliferation + changes in cytoskeleton, membranes; chromosomal changes may occur as well tumor types- based on tissue of origin carcinomas = epithelial tissue sarcomas = connective tissue leukemias = circulating cells of lymphatic system lymphomas = solid tumors of lymphatic system signs of transformation in culture: surface changes; transcription; enzyme phosphorylation many transformed cell lines of many types of tissue study characteristics & differences from normal cells DNA tumor viruses: Papova; adeno; herpes; pox general characteristics: productive infection -> cell lysis nonproductive infection -> transformation inefficient ratio: 106-107 virions/transformation event contrasts c RNA viruses: productive infection & nonproductive -> transformation efficient ratio: 102-104 virions/transformation event **factors which limit DNA virus production -> incr. transformation UV; temp change; chemicals polyoma & friends: polyoma & SV40- non-oncogenic in normal host culture characteristics T-antigens: appear essential for stable transformation fxns of small t, middle T & large T antigens polyoma & SV40 may use different mechanisms of stimulating resting host cells into dividing & transforming adenoviruses: different types in relation to freq. of oncogenesis transform nonpermissive cells only part of viral genome found retained in transformed cells T antigens: 5 distinct proteins herpesviruses: cause of many human & animal tumors; transformation by defective virus, entire genome need not be present EBV- thought to cause Burkitt's lymphoma, nasopharyngeal carcinomas HSV-2 & cervical cancer: epidem assoc. HHV-8 assoc. c Kaposi's sarcoma- endothelial cell lining lymph vessels still debated- other viruses may be involved RNA tumor viruses: Retroviruses RNA viruses important in discovery of proto-oncogenes sarcoma viruses- form solid tumors leukemia viruses- transform blood cells integration required for transcription- true for most lentiviruses- integration not required avian sarcoma viruses: Rous sarcoma virus src- sequences required for transformation must be functional & must fxn continuously src protein- phosphokinase: tyr instead of ser or thr multistage transformation process for examples of other types of oncogenes: see Wagner, Table 20.1 murine sarcoma virus- Moloney strain: combination of viral promoter for transcription + cellular proto-oncogene -> transformation v-mos: protein-serine kinase tumor growth factors(TGF): removal of TGF reverses transformation leukemia viruses: acute vs. chronic acute: all are recombinants of cellular genes & retrovirus cause rapid & severe leukemias chronic: slow transformation; difficult to demonstrate means of transformation
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