L06: Viruses And Cancer Flashcards
What are the characteristic features of a virus
DNA/RNA
Protein capsid
Membrane envelope
Why does viruses require a host cell
For translation of viral MRNA
Genome transcription
Genome replication
Give 3 examples of virus that are associated with cancer
Adenovirus
Herpes virus
Papillomovirus
In a tumour cell what happens to oncogenes and tumour suppressor genes
Oncogene is activated
Tumour suppressor gene is inacitved
What is the normal role of tumour suppressor genes
Inhibit cell division
What is the role of proto-oncogenes
Drive cell division and cell cycle
Which viruses in the IARC classification are considered to be carcinogenic
Epstein Barr virus Kaposi sarcoma associated virus Hepatitis C Hepatitis B Humans T cell lymphotrophic virus type 1 High risk human papilloma virus types Merkel cell polyomavirus HIV-1
Which bacteria in the IARC classification is considered to be carcinogenic
Helicobacter pylori
In what type of countries are infectious agents that cause cancer higher in
Developing countries due to better hygiene and better screening programs
What are the 2 ways viruses can behave as carcinogens
Direct
Indirect
What is a direct carcinogen
Viral oncogenes when expressed drive cell cycle and proliferation
What are indirect carcinogens
Viruses that cause cancer through chronic infection, inflammation and immunosuppression that lead to carcinogenic mutation in host
Is HIV-1 a direct or indirect carcinogen
Indirect carcinogen
In HIV what does persistent immune activation lead to in tissues
Chronic tissue damage
When there is cytokine release in HIV what happens to the micro-environment
Changes
What are the other roles of HIV
Increase angiogenesis
Accelerate fibrosis
How is fibrosis accelerated in HIV
By stimulation of extracellular matrix
If there is fibrosis what cancer is likely to occur
Liver cancer
In people with HIV what risk are they are
Increased proliferation of co-existing viruses
What co-existing viruses can occur in HIV patients
EBV
KSHV
Herpes
HBV/HCV
What is the Koch’s postulate useful for
Identifying an infectious as the cause of a specific disease
List the reasons why the Koch’s postulate fails in viral cancer
- Viral infection have a long latency period between primary and tumour development
- only small percent of individuals with the virus develop cancer
- cancer is not only due to the virus because there are other factors involved
- cancer only contains a part of the viral genome (not the whole)
- virus is only one part of the chain
Name a viral infection that shows latency
Herpes (EBV)
What cancer is herpes virus (EBV) associated with
Nasopharyngeal carcinoma
Burkkit lymphoma
Apart from the herpes virus what other factors contribute to burkitt lymphoma
Malaria
Chromosome translocation of c-myc (oncogene) to IG enhancer
Apart from herpes virus what others factors contribute to nasopharyngeal carcinoma
Salted fish