Special Topic: Cancer Flashcards
What is the definition for cancer?
When abnormal cells divide uncontrollably
What can the abnormal cells do?
- form tumours
- invade neighbouring tissues
- spread through the body to distant tissues= metastasis
In normal cell division, what signals does a cell receive?
- positive signals telling it to divide
- e.g. growth factors and hormones
What signals tell a cell not to divide?
Contact inhibition
-where there are enough cells so more cell division isn’t needed
DNA damage response
-something is wrong with the DNA, told not to divide until it’s repaired
What is the difference between passenger and driver mutations?
- passenger has no effect on the cancer cell
- driver causes clonal expansion
What is chemotherapy resistance mutation?
- causes relapse after chemotherapy
- these mutations predate the initiation of treatment
Where do the mutations occur?
Germline and Somatic
When do these mutations occur?
Germline -present in the fertilised egg -present in every cell of the body -inherited from parent -can be passed onto offspring Somatic -occurs after division of the fertilised egg -only present in subset of cells -not inherited from a parent -occasionally passed to offspring
What are the 3 genes involved in causing cancer?
Oncogenes
Tumour suppressor genes
DNA repair genes
What are proto-oncogenes involved in?
The positive control of cell growth and division
What are the 5 main classes of proto-oncogenes?
Class I: Growth Factors
Class II: Receptors for Growth Factors and Hormones
Class III: Intracellular Signal Transducers
Class IV: Nuclear Transcription Factors
Class V: Cell-Cycle Proteins
How many mutations are required to inactivate tumour suppressor genes and what does this mean?
- 2 mutations, one on each allele
- mutation is recessive at cellular level
What is the main cause of inherited cancer syndromes?
Tumour suppressor genes
What cancer inhibits tumour suppressor genes?
Retinoblastoma
What does mutations in DNA repair genes lead to?
An increased risk of mutations in oncogenes and tumour suppressor genes
Give examples of DNA repair genes?
- BRCA1 and BRCA2 in hereditary breast and ovarian cancer
- Mismatch repair genes in Lynch Syndrome
What are two types of epigenetic modifications and what do they do?
DNA Methylation and Histone Modification
-they both regulate gene expression
What is epigenetics?
The study of changes in gene expression caused by mechanisms other than changes in the underlying DNA sequence
What are the differences between sporadic and hereditary cancers?
Sporadic: -single tumour -unilateral -late onset Hereditary: -multiple tumours -bilateral -early onset
