Special Topic: Cancer

Question 1

What is the definition for cancer?

Answer 1

When abnormal cells divide uncontrollably

Question 2

What can the abnormal cells do?

Answer 2

• form tumours
• invade neighbouring tissues
• spread through the body to distant tissues= metastasis

Question 3

In normal cell division, what signals does a cell receive?

Answer 3

• positive signals telling it to divide

- e.g. growth factors and hormones

Question 4

What signals tell a cell not to divide?

Answer 4

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

Question 5

What is the difference between passenger and driver mutations?

Answer 5

• passenger has no effect on the cancer cell

- driver causes clonal expansion

Question 6

What is chemotherapy resistance mutation?

Answer 6

• causes relapse after chemotherapy

- these mutations predate the initiation of treatment

Question 7

Where do the mutations occur?

Answer 7

Germline and Somatic

Question 8

When do these mutations occur?

Answer 8

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

Question 9

What are the 3 genes involved in causing cancer?

Answer 9

Oncogenes
Tumour suppressor genes
DNA repair genes

Question 10

What are proto-oncogenes involved in?

Answer 10

The positive control of cell growth and division

Question 11

What are the 5 main classes of proto-oncogenes?

Answer 11

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

Question 12

How many mutations are required to inactivate tumour suppressor genes and what does this mean?

Answer 12

• 2 mutations, one on each allele

- mutation is recessive at cellular level

Question 13

What is the main cause of inherited cancer syndromes?

Answer 13

Tumour suppressor genes

Question 14

What cancer inhibits tumour suppressor genes?

Answer 14

Retinoblastoma

Question 15

What does mutations in DNA repair genes lead to?

Answer 15

An increased risk of mutations in oncogenes and tumour suppressor genes

Question 16

Give examples of DNA repair genes?

Answer 16

• BRCA1 and BRCA2 in hereditary breast and ovarian cancer

- Mismatch repair genes in Lynch Syndrome

Question 17

What are two types of epigenetic modifications and what do they do?

Answer 17

DNA Methylation and Histone Modification

-they both regulate gene expression

Question 18

What is epigenetics?

Answer 18

The study of changes in gene expression caused by mechanisms other than changes in the underlying DNA sequence

Question 19

What are the differences between sporadic and hereditary cancers?

Answer 19

Sporadic:
-single tumour
-unilateral
-late onset
Hereditary:
-multiple tumours
-bilateral
-early onset