7. Cellular proliferation Flashcards Preview

ESA 2 - Pathological Processes > 7. Cellular proliferation > Flashcards

Flashcards in 7. Cellular proliferation Deck (12)
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1
Q

What determines the size of a cell population in adults?

A
  • Depends on rate of:
    i) cell proliferation, regulated by proto-oncogenes
    ii) cell differentiation
    iii) cell death by apoptosis

(i.e. increased cell numbers seen with increased proliferation or decreased cell death)

2
Q

How is cell proliferation controlled?

A
  • Largely by chemical signals (e.g. hormones) from the microenvironment, which either stimulate or inhibit cell proliferation.
  • When a signalling signalling molecule binds to a receptor, it results in modulation of gene expression (proto-oncogenes).
  • Receptors usually in cell membrane but can be in cytoplasm or nucleus (e.g. steroid receptors).
3
Q

What can chemical signals make a cell do?

A
  1. survive - resist apoptosis
  2. divide - enter cell cycle
  3. differentiate - take on specialised form and function (permanent exit from cell cycle)
  4. die - undergo apoptosis
4
Q

How can increased tissue growth be promoted by modifying the cell cycle?

A
  1. shortening the cell cycle

2. conversion of quiescent (G0) cells to proliferating cells by making them enter cell cycle

5
Q

What are the phases of the cell cycle?

A

Interphase:

  • G1 - gap 1, cell growth and protein synthesis
  • S - DNA synthesis/replication
  • G2 - gap 2, preparation for division
6
Q

Can cells with damaged DNA replicate?

A

In physiological state, no, as cell cycle progression controlled by checkpoints which monitor DNA damage and level of DNA replication.

  • G1/S checkpoint: checks for DNA damage before replication
  • G2/M checkpoint: checks for DNA damage after replication
  • Restriction (R) point towards end of G1 is most critical checkpoint - point of no return.
7
Q

Which is the most commonly altered checkpoint in cancer cells?

A

R point

8
Q

What is the result of checkpoint activation?

A

Cell cycle is suspended and:

  • DNA repair mechanisms triggered
  • or apoptosis if DNA cannot be repaired

controlled by p53

9
Q

Which proteins regulate cell cycle progression?

A

Cyclins and cyclin-dependent kinase (CDK) enzymes -particularly regulate G1/S transition

  1. CDKs activated by binding to cyclins
  2. activated CDKs phosphorylate proteins (e.g. retinoblastoma susceptibility protein) that are critical for progression to next cell cycle stage
10
Q

How do some growth factors promote tissue proliferation via cyclin-CDKs?

A
  1. some stimulate cyclin production

2. some prevent production of CDK inhibitors (which tightly regulate activity of cyclin-CDK complexes)

11
Q

How many times can cells divide?

A

Hayflick limit (due to telomere degeneration from lack of telomerase) = 61.3 divisions

12
Q

During which phase of the cell cycle are cells responsive to mitogenic GFs and TGF-B?

A

G1 until R point