8.1 Cell Cycle Control and Dysregulation

Question 1

What triggers cell division?

Answer 1

Mitogens
- proteins (e.g. EGF, FGF, VEGF, TGF-b)
- small molecules (e.g. ATP, adenosine)

Question 2

What are the three phases and three checkpoints of the eukaryotic cell cycle?

Answer 2

G1 phase (growth)
S phase (DNA synthesis)
G2 phase (prep for mitosis)
G1 restriction checkpoint
G2 checkpoint
Metaphase checkpoint

Question 3

What is cancer?

Answer 3

A group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body

Question 4

What are the main 5 types of cancer?

Answer 4

Carcinoma - epithelial cells
Sarcoma - connective tissue
Lymphoma - hematopoietic cells
Blastoma - immature precursor/embryonic cells
Germ cell tumour - pleuripotent cells

Question 5

What is carcinogenesis

Answer 5

Formation of a cancer

Question 6

Explain G0 and what regulates cell entry in G0

Answer 6

Non-proliferating cells are in G0
- terminally differentiated cells
- resting cells can exit

Regulated by:
- tumour supressor genes
- proto-oncogenes

Question 7

What happens to the regulators of proliferation for cancer to occur?

Answer 7

Must have a mutation in both oncogenes and tumour suppressor genes

Question 8

What do tumour suppressor genes do?

Answer 8

Encodes proteins that stop cells proliferating out of control (the brakes)

Question 9

What do proto-oncogenes/oncogenes do?

Answer 9

Encodes proteins that promote growth, inhibit apoptosis, or both (the accelerator)

Question 10

Proto-oncogene vs oncogene?

Answer 10

Proto-oncogene = normal gene that can become an oncogene

Oncogene = mutant form, results in lodd of regulation and ↑ protein expression

Question 11

Explain the MAP kinase signaling cascade and the mutant proteins

Answer 11

Receptor - mutant ↑ activity = ↑ signalling

RAS - mutant unable to lyse GTP = permanently activated

Raf - mutant constitutively activates downstream molecules

Question 12

What is p53 and what happens when it is mutated?

Answer 12

Part of G1 checkpoint
DNA damage = ↑p53 = halts cycle until repaired

Mutation = cells with damaged DNA proliferate and avoid apoptosis

Question 13

Other properties of cancer cells (4)?

Answer 13

• evades apoptosis
• tissue invasion and metastasis
• overcome replicative senescence
• angiogenesis

Question 14

Telomeres and cancer

Answer 14

Limit the number of times a cell can divide, cell senescence when telomeres are v short

Cancer cells express telomerase which adds telomeres back onto chromosomes for unlimited cell division

Question 15

Describe angiogenesis of cancer

Answer 15

Tumour secretes VEGF which promotes growth of blood vessels towards tumour so it has its own blood supply

Question 16

Describe metastasis of cancer

Answer 16

Metastasis = spread of cancer from primary tumour to secondary tumour

Certain tumour cells colonise distinct organs that have favourable conditions for the growth of that particular tumour