Gene expression and cancer

Question 1

what is cancer

Answer 1

Uncontrolled cell division → tumour
* Not all tumours are cancerous

Question 2

what are the Main characteristics of benign and malignant tumours

Answer 2

Benign tumours
- Grow slowly
- Well differentiated / specialised
- normal, regluar neclei
- Well defined borders/boundary; cell
adhesion molecules stick cells together and
to a particular tissue
- Easy to treat - can normally be removed by
surgery, rarely returns

malignant
- Grow rapidly
- Cells become unspecialised / poorly
differentiated
- Irregular, larger/darker nuclei
- rregular / poorly defined borders and not
encapsulated, metastasis occurs
- Removed by radiotherapy / chemotherapy as
well as surgery; can be life threatening and
recurrence more likely

Question 3

what is the role Tumour suppressor genes in tumour development

Answer 3

Normal function
* Code for proteins involved in control of cell division
* In particular, stopping cell cycle (when DNA damage detected)
* Also involved in causing self-destruction of cell (apoptosis) (where damaged DNA
cannot be repaired)

Role in development of tumours
* Mutation alters amino acid sequence and tertiary structure of protein = non-functional protein
* Or increased methylation prevents transcription / expression of protein
* Damaged DNA not repaired / cells not killed; uncontrolled cell division
* Note – would need 2 mutated alleles

Question 4

what is the role of (Proto)- oncogenes in tumour development

Answer 4

Normal function
* Code for proteins involved in control of cell division
* In particular, stimulating cell division (when growth factors attach to receptors
on cell membrane, so cell division is required)

Role in development of tumours
* Mutation could turn it into permanently activated oncogene
* Decreased methylation / increased acetylation causes excess transcription
* Cell division permanently activated; rapid / uncontrolled cell division
* Note – only need 1 mutated allele

Question 5

what is The role of increased oestrogen concentrations in the development of some breast
cancers

Answer 5

• Areas of high oestrogen conc. such as adipose tissues in breasts, cell division
  uncontrolled
• Growth of cancer minimised with drugs blocking production / action of oestrogens in the
  breasts e.g. Tamoxifen prevents oestrogen binding to receptor