Tumour Pathology 5 Flashcards
List carcinogenesis factors
- Geographical and environmental
- Ages
- Heredity
Tumour suppressor genes (anti-oncogenes) function
Growth inhibiting genes that discourage growth or temporarily halt cell division to carry out DNA repair
Proto-oncogenes function
Genes that promote normal cell growth and mitosis
Key event in tumour formation
Uncontrolled cell proliferation via cell cycle dysregulation via loss of tumour suppressor gene function
Effect of mutation of CDKIs
Drive proliferation
Effect of mutational activation of Cyclin D or CDK4
Loss of ability to inhibit pRb allowing it to bind to E2F and stop the cell cycle
Two types of inheritance on oncogenes
- Inherited form
- Sporadic form
What is the ‘two hit hypothesis’ of oncogenesis?
More than one mutation necessary for carcinogenesis
Describe inherited form of retinoblastomas
- One defective inherited copy of pRb
- Somatic point mutation of other copy later in life
Develops earlier than sporadic as one requires 1 mutation
Describe sporadic form of retinoblastomas
-Both mutations occur in a single cell
Cancer develops later in life as individual must have 2 mutations
Proto-oncogenes function
Genes that code for proteins that regulate cell growth
How are oncogenes formed?
- Mutation in DNA coding for photo-oncogenes
- Dysregulation of photo-oncogene expression; over expression
Oncogene function
Uncontrolled cell proliferation
- Growth factors
- Signal transduction
Viral carcinogenesis mechanisms
- Virus genome inserts near host photo-oncogene
- Viral promoter cause porto-oncogene over expression
- Retroviruses insert oncogene into host DNA causing mitosis
List DNA viruses known to cause cancer in human
- HPV (cervical cancer)
- Hep B (liver cancer)
- EBV (burkitt lymphoma)
