Oncogenic Viruses Flashcards
What is the difference between oncolytic vs oncogenic?
oncolytic used for cancer treatment
oncogenic is cancer causing virus
What are the causes of cancer?
carcinogen, UV radiation, viruses, genetic predisposition, environmental/occupational, random mutations
What are the molecular mechanisms of cancer?
Mutations
How can you prevent cancer?
sunscreen
limit carcinogen exposure
vaccination against oncogenic viruses (HPV, Hep B)
antivirals if no vaccination (Hep C)
How is cancer a multi-step process?
Cancer develops from cells that have acquired mutations.
These mutations ultimately lead to uncontrolled cell growth
What are the characteristics of cancer cells?
bypass apoptosis signals for cell death
circumvent the need for growth signals bypass growth signals needed for division so they can constantly divide
escape immunosurveillance bypass immune response
(tumors) command their own blood supply angiogenesis
may metastasize move to different body locations
lose tumor suppressor gene functions (example p53)
What is p53?
Tumor Suppressor Genes that controls when cells divide,
- cancer cells prevent p53 from functioning properly
-p53 acts at G1 to S phase checkpoint to ensure DNA is right before DNA replication
if irreparable then p53 initiates apoptosis
What is cancer?
a term for diseases in which abnormal cells divide without control.
What is an oncogene?
gene that has the potential to convert a normal cell to a cancerous or transformed cell
What is a Proto-oncogene?
cellular genes that promote the normal growth and division of cells (they can be converted to cancer causing oncogenes when dysregulated)
What is a Viral oncogene (v-onc)?
a viral gene responsible for the oncogenicity of the virus
What are Tumor suppressor genes?
genes that regulate and coordinate the cell cycle and cell division. These genes cause cancer when they are turned off.
What is Cell transformation?
changes in the morphological, biochemical, or growth properties of a cell.
What is a Benign tumor?
cease to grow in the body after reaching a certain size and generally do no harm
What is a Malignant tumor?
grow and divide indefinitely and impair the normal function of organs and tissues
What is Metastasis?
when a cell or clump of cells separates from a tumor and spreads to another location.
What are the Two main ways that viruses transform cells (1st step in cancer development)?
- By activation of cellular signal transduction cascades
2. Interference with the cell cycle controls
How do oncogenic viruses cause cancer?
by inducing changes that affect the processes that control cell proliferation
How can Proto-oncogenes be converted to oncogenes?
Movement of DNA within the genome: if it ends up near an active promoter, transcription may increase
Amplification of a proto-oncogene: increases the number of copies of the gene
Point mutations in the proto-oncogene or its control elements: causes an increase in gene expression
How can translocation convert a proto-oncogene to an oncogene?
movement of proto-oncogene so that it’s under influence of different promotor
How can gene amplification convert a proto-oncogene into an oncogene?
having multiple copies of proto-oncogene instead of just 1 = more protein made
How can point mutations convert a proto-oncogene into an oncogene?
mutation in gene = hyperactive protein production
mutation in promotor = normal growth stim hormone in excess = excess protein production
How can conversion of Ras proto-oncogene to an oncogene leads to uncontrolled cell growth?
Normal Cell Growth Process:
- Signal (growth factor)
- Transduction (relay proteins)
- Response (mitosis)
Relay protein RAS is G protein
- in normal cell it switches from on/off state
- usually in off state (bound by GDP)
Mutation in RAS causes RAS to be constantly bound by GTP (unable to bind GDP) = constant ON state
- constant binding by GTP causes constant transduction by relay proteins = constant gene expression for protein that stimulates cell cycle (mitosis)
- don’t need growth factor signalling at receptor
“Stepping on the gas”
What is an example of a tumor suppressor gene?
Tumor-suppressor proteins (p53)
- Repair damaged DNA
- Control cell adhesion
- Inhibit the cell cycle in the cell-signaling pathway
- Induce apoptosis if damage irreparable
Some of the DNA tumor viruses interfere with the functions of tumor
- suppressor proteins (p53 and Rb)
