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Oncogenic viruses

Oncogenic viruses. Nehal Draz. They are viruses capable of inducing cell transformation. Characteristics of transformed cells. 1- Altered Growth Pattern. 2- Altered Cell Surface. Increase growth rate decrease cell adhesion Lack of contact inhibition Infinite in vitro life span.

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Oncogenic viruses

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  1. Oncogenic viruses NehalDraz They are viruses capable of inducing cell transformation

  2. Characteristics of transformed cells 1- Altered Growth Pattern 2- Altered Cell Surface • Increase growth rate • decrease cell adhesion • Lack of contact inhibition • Infinite in vitro life span Appearance of new surface Ags, most of them are virus specific 3- Altered Biochemichal Processes 4-Tumorigenicity (transplantability) Increased metabolic rate & glycolysis The ability to produce tumor when injected into appropriate test animal

  3. Mechanisms of cell transformation • All tumor viruses are either DNA or RNA viruses that generate DNA provirus after being integrated into the host cell chromosome • Integrated viral genes can use host cell transformation through: 1- Introduction of a new transforming gene into the cell called viral oncogene( v onc) 2- Alteration of expression of a cellular proto-oncogene. This can result from insertional mutation, translocation, or gene amplification

  4. Protooncogenes - represent complicated pathways responsible for regulating cell division & differentiation • Incorrect expression of these genes leads to interruption of regulation & uncontrolled cell growth, resulting in cancer 3- Viral proteins may inactivate a tumor suppressor gene as p53 tumor suppressor gene that is altered in 50% of human cancers

  5. The mode of virally-induced tumors • Acutely-transforming • The viral particles carry a gene that encodes for an overactive oncogene called viral-oncogene (v-onc) • The infected cell is transformed as soon as v-onc is expressed.

  6. Slowly-transforming • The virus genome is inserted, especially as viral genome insertion is an obligatory part of retroviruses, near a proto-oncogene in the host genome. • The viral promoteror other transcription regulation elements in turn cause overexpression of that proto-oncogene, • This in turn induces uncontrolled cellular proliferation. • Because viral genome insertion is not specific to proto-oncogenes and the chance of insertion near that proto-oncogene is low, slowly-transforming viruses have very long tumor latency compared to acutely-transforming viruses, which already carry the viral oncogene.

  7. Types of tumor viruses DNA Viruses 1- Papovavirus (papilloma) 2- Herpes viruses ( HSV-2 &EBV) 3- Hepatitis B virus 4- Pox virus (molluscumcontagiosum) 5- JC virus 1- Retrovirus family: HTLV-1 2- Flavivirus: HCV RNA Viruses

  8. Different tumors produced by DNA oncogenic viruses

  9. Different tumors produced by RNA oncogenic viruses

  10. Vaccine for cancer prevention • Advances in cancer research have made a vaccine designed to prevent cancer available. • In 2006, the US FDA approved a human papilloma virus vaccine, called Gardasil. The vaccine protects against four HPV types, which together cause 70% of cervical cancers and 90% of genital warts. • In March 2007, the US CDCAdvisory Committee on Immunization Practices (ACIP) officially recommended that females aged 11-12 receive the vaccine, and indicated that females as young as age 9 and as old as age 26 are also candidates for immunization.

  11. THANK YOU!

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