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Tumour pathology > Tumour Pathology 4 > Flashcards

Tumour Pathology 4 Flashcards

1
Q

What are the 2 main stages of the cell cycle?

A

Interphase

M phase

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2
Q

What are the 5 phases of cell cycle? (In order)

A 
G1 
DNA replication (S phase)
G2 
Mitosis 
Cytokinesis
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3
Q

What is the purpose of each stage of the cell cycle?

A

G1- All the cellular contents except from chromosomes are replicated
S- DNA replication/synthesis
G2- Double-checking of any chromosomal errors and repair if any are present
Mitosis - Division of genetic material within 2 nuclei in the same cell
Cytokinesis - Production of two daughter cells, each with one nucleus, through separation of cytoplasm.

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4
Q

How is the sequence of the cell cycle controlled?

A

Checkpoints
Activators
Breaks

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5
Q

What is the G1/S restriction point?

A

Cells that pass this point are committed to go through the S phase
Before the S point cells in cell cycle are controlled by external factors
After S point cells in cell cycle are autonomously controlled

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6
Q

What are the different points in the cell cycle at which there could be an arrest?

A

G1 to S phase / S
G2 to M phase / G2
G1
M

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7
Q

What controls the different phase arrest?

A

Checkpoints

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8
Q

Why would there be an arrest in S/G1 to S phase?

A

Unreplicated DNA

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9
Q

Why would there be an arrest in G2/G2 to M phase?

A

Unreplicated or damaged DNA

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10
Q

Why would there be an arrest in the M phase?

A

DNA misalignment/ deletion or tandem repeats

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11
Q

Why would there be an arrest in the G1 phase

A

Damaged DNA or inadequate nutrients

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12
Q

What are activators?

A

Active or inactive enzymes that act as switches in the cell cycle

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13
Q

What are activators composed of ?

A

cyclin and cyclin dependent kinase

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14
Q

Which is the regulatory component of activators?

A

cyclin

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15
Q

How do CDK/cyclin complexes work?

A

They operate in sequential stages
When cyclin -CDK complexes are active they phosphorylate target proteins.
Target proteins then become active or inactive and pass on to regulate the next phase of the cell cycle.

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16
Q

How does S phase preparation occur?

A

The G1 Cyclin/CDK complex become active

17
Q

What is an example of pro-mitotic signals?

A

G1 Cyclin-CDK complexes

18
Q

What is required for DNA replication?

A

enzymes and S cyclin

19
Q

How is S cyclin expression promoted?

A

Through G1 cyclin-CDK complex that becomes active and causes the cell to enter the S phase.

20
Q

What are family examples of CDK inhibitors?

A
  • INK4a

- CIP/KIP

21
Q

What are two examples of an INK4a inhibitors and what is its effect?

A

p161INK4a inhibitor that binds to CDK4 and stops cell cycle at G1
p14 which inhibits p53 degradation

22
Q

What are examples of CIP/KIP family inhibitors and what is their effect on the cell cycle?

A

p21
p27
p57
They bind to cyclin-CDK complexes and inactivate them causing cell cycle to stop at G1

23
Q

How is p21 activated?

A

By p53

24
Q

What is a powerful signal for cell cycle activation?

A

E2F

25
Q

What is an example of a break in the cell cycle?

A

Retinoblastoma

26
Q

How is retinoblastoma activated?

A

Through its hyperphosphorylation by the cyclin/CDK complex

27
Q

How else is Retinoblastoma written?

A

pRB

28
Q

Why can retinoblastoma act as a break for the cell cycle?

A

It is a tumour suppressor gene

29
Q

How does retinoblastoma affect the cell cycle?

A

It carries out its tumour suppressor role causing the cell cycle to stop at G1 phase.

30
Q

Why does inactivation of retinoblastoma inhibit cell cycle from progressing?

A

pRB loses its affinity to E2F transcription factor, which is a major signal for cell cycle activation

31
Q

What is Carcinogenesis?

A

Failure of cell cycle control?

32
Q

How is Carcinogenesis caused?

A
  • Inbalance of proliferation and cell apoptosis

- More than one mutations in genes regulating cell division, apoptosis and DNA repair.

33
Q

What are frequently disrupted pathways ?

A

p53 pathway

cyclin D - pRB - E2F

34
Q

How do malignant neoplasms come about?

A

Mutant p53 activation, where DNA damage does not cause cell cycle to stop or DNA repair to take place thus leading to proliferation of cells with damaged DNA

35
Q

How is cell repair accomplished?

A

activation of normal p53 which activates p21 which in turn inactivates cyclin-CDK complex and halts cell cycle at G1 at which stage DNA repair occurs

36
Q

Where are all cancer cells dysregulated?

A

G1-S phase

37
Q

What genes are most often mutated?

A

Cyclin D, CDK4, p16, pRB

Tumour pathology (5 decks)

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