Inhoudsopgave
Tumor viruses .................................................................................................................................. 2
1. Oncogenesis ........................................................................................................................ 2
2. Transformation & immortalization ......................................................................................... 2
3. Cancer cells ......................................................................................................................... 3
4. Exosomes ............................................................................................................................ 3
5. Genes & cancer .................................................................................................................... 4
5.1 Proto-oncogenes................................................................................................................. 4
5.2 Viral oncogenes (v-oncogenes) ............................................................................................ 5
5.3 Tumor suppressor genes ...................................................................................................... 5
6. Human papillomavirus ......................................................................................................... 6
6.1 Classification ...................................................................................................................... 6
6.2 Genome organization .......................................................................................................... 6
7. HPV life cycle ....................................................................................................................... 7
8. Prevention ............................................................................................................................ 8
1
, Tumor viruses
Virus host infection outcome depends on virus, host cell & immune system
• Acute infection
• Subclinical infection The balance favors the host → virus is cleared from the host
• Persistent & chronic infection
• Latent infection Immune system cannot clear the virus from the host → long-lasting,
• Slowly progressive infection persistent infection
• Virus-induced tumors
Oncogenic viruses
• Virus can act as COFACTOR or accidental initiator of oncogenesis (altering control of cell proliferation)
• Normal cells infected with certain viruses → transformed into cancer cells
- Due to expression or activation viral oncogenes
- Integration of viral genes or genomes into the host
Cancer = multifactorial → virus infection is only one factor
DNA viruses causing cancer vary from RNA tumor viruses
• Different families of ds DNA viruses → transformation
• Oncogenic efficacy = low compared to retroviruses
Mutation may be inherited or arise because of exposure to environmental carcinogens of infected agents
• Malignancy = consequence of a side effect of viral infection or host respons to the virus.
1. Oncogenesis
Oncogenesis = development of cancer (disease of damaged genes)
• Genetic, multistep disease
• Caused by accumulation of mutations in ≠ genes in a single cell
- Natural mutations ↑ by mutagens
o Free radicals
o Ionizing radiation
o Chemical carcinogens
o Some viruses associated with cancer
Mutation in genes that encode proteins that regulate cell division
Infection by viruses → new genes encoding proteins that alter/inhibit cell proteins involved in cell cycle
regulation.
2. Transformation & immortalization
Transformation: abnormal growth parameters & behavior
• Immortality
• Reduced requirements for growth factor
• ↑ saturation density
• Loss of normal cell growth
• Loss of contact inhibition → can grow over one another (= clusters)
• Anchorage independent (grow without attachment)
• Altered morphology (rounded shape)
• ↑ transport glucose + tumorigenicity
Immortalization: often associated with telomerase activation (maintains telomere length)
• Cell gain ability to divide indefinitely
2
Tumor viruses .................................................................................................................................. 2
1. Oncogenesis ........................................................................................................................ 2
2. Transformation & immortalization ......................................................................................... 2
3. Cancer cells ......................................................................................................................... 3
4. Exosomes ............................................................................................................................ 3
5. Genes & cancer .................................................................................................................... 4
5.1 Proto-oncogenes................................................................................................................. 4
5.2 Viral oncogenes (v-oncogenes) ............................................................................................ 5
5.3 Tumor suppressor genes ...................................................................................................... 5
6. Human papillomavirus ......................................................................................................... 6
6.1 Classification ...................................................................................................................... 6
6.2 Genome organization .......................................................................................................... 6
7. HPV life cycle ....................................................................................................................... 7
8. Prevention ............................................................................................................................ 8
1
, Tumor viruses
Virus host infection outcome depends on virus, host cell & immune system
• Acute infection
• Subclinical infection The balance favors the host → virus is cleared from the host
• Persistent & chronic infection
• Latent infection Immune system cannot clear the virus from the host → long-lasting,
• Slowly progressive infection persistent infection
• Virus-induced tumors
Oncogenic viruses
• Virus can act as COFACTOR or accidental initiator of oncogenesis (altering control of cell proliferation)
• Normal cells infected with certain viruses → transformed into cancer cells
- Due to expression or activation viral oncogenes
- Integration of viral genes or genomes into the host
Cancer = multifactorial → virus infection is only one factor
DNA viruses causing cancer vary from RNA tumor viruses
• Different families of ds DNA viruses → transformation
• Oncogenic efficacy = low compared to retroviruses
Mutation may be inherited or arise because of exposure to environmental carcinogens of infected agents
• Malignancy = consequence of a side effect of viral infection or host respons to the virus.
1. Oncogenesis
Oncogenesis = development of cancer (disease of damaged genes)
• Genetic, multistep disease
• Caused by accumulation of mutations in ≠ genes in a single cell
- Natural mutations ↑ by mutagens
o Free radicals
o Ionizing radiation
o Chemical carcinogens
o Some viruses associated with cancer
Mutation in genes that encode proteins that regulate cell division
Infection by viruses → new genes encoding proteins that alter/inhibit cell proteins involved in cell cycle
regulation.
2. Transformation & immortalization
Transformation: abnormal growth parameters & behavior
• Immortality
• Reduced requirements for growth factor
• ↑ saturation density
• Loss of normal cell growth
• Loss of contact inhibition → can grow over one another (= clusters)
• Anchorage independent (grow without attachment)
• Altered morphology (rounded shape)
• ↑ transport glucose + tumorigenicity
Immortalization: often associated with telomerase activation (maintains telomere length)
• Cell gain ability to divide indefinitely
2
