Oncology Flashcards
What is cancer?
Canceris when abnormal cells divide in an uncontrolled way
The abnormal cells have the potential to:
Form tumours
Invade neighbouring tissues
Spread through the body to distant tissues (metastasise)
Describe the signals which stimulate or inhibit cell division
A cell receives positive signals telling it to divide e.g. Growth factors/hormones
There are also signals telling a cell not to divide. These are from:
Contact inhibition= you are surrounded by other cells- we don’t need new cells at the moment
DNA damage response=Something is wrong with your DNA, don’t divide until it’s repaired
How is cellular DNA constantly mutated?
It can be mutated internally by reactive oxygen species and ineffective DNA repair mechanisms
It can be mutated externally by UV light, ionising radiation, cigarette smoke and chemical consumption
Where do cancer mutations occur?
Germline: Present in the fertilised egg
Present in every cell in the body
Can be inherited from a parent and passed to offspring
Somatic: Occurs after division of the fertilised egg
Only present in a subset of cells
Not inherited from a parent, v occasionally passed to offspring
Briefly outline the 2 hit hypothesis
2 hits cause cancer. These hits come from random mutations in one copy of the gene as the cell divides. Once a mutation in the 2nd copy of the gene occurs the cell may get cancerous
Germline mutations mean that the first hit is already inherited
What are proto oncogenes?
Proto-oncogenes positively control of cell growth and division.
Main classes include:
Class I: Growth Factors
Class II: Growth Factor and Hormone receptors
Class III: Intracellular Signal Transducers
Class IV: Nuclear Transcription Factors
Class V: Cell-Cycle Control Proteins
What is oncogenesis?
•Mutations relax control of cell growth, allowing unregulated proliferation
– oncogenesis
•A mutation in only one copy of the gene is problematic so the mutation is dominant
How can problems in tumour surpressor genes cause cancer?
Two mutations (one on each allele) are required to inactivate tumor suppressor genes – i.e. mutations are RECESSIVE at the cellular level
What are DNA repair genes?
DNA is constantly damaged. DNA repair processes correct the damage.
Mutations in DNA repair genes = increased risk of mutations in
oncogenes/tumour suppressor genes
Example of DNA repair genes:
BRCA1/2 in hereditary breast and ovarian cancer
Mismatch repair genes in Lynch Syndrome (MLH1, MSH2, MSH6, PMS2)
