Cell Cycle Checkpoints and Cancer- Lecture 53

Question 1

Define benign cells.

Answer 1

cells that are undergoing uncontrolled proliferation that do not result in any manifest human disease

Question 2

Define malignant cells.

Answer 2

cells with unlimited cell renewal resulting in cancer

Question 3

Define primary cells.

Answer 3

cells with a finite lifespan that are directly removed from the body

Question 4

Define immortalized cells.

Answer 4

cells with an unlimited lifespan

Question 5

Define transformed cells.

Answer 5

cells that have acquired certain properties

Question 6

Define tumorgenic cells.

Answer 6

cells that are transformed and have the additional property of being able to form a tumor

Question 7

Describe the the general characteristics that can identify a cancer cell.

Answer 7

morphology
altered metabolism
unlimited lifespan
anchorage independence
loss of contact inhibition
no dependence on growth factors
changes in ploidy
angiogenisis
invasive
metastisis

Question 8

How is metabolism altered in cancer cells?

Answer 8

rely on glycolysis for ATP production (rather than the TCA cycle) because they use the TCA cycle to produce building blocks for replication
can be detected with PET scans

Question 9

Which cancer cells normally become anchorage independent and how do they do so?

Answer 9

epithelial carcinomas

loss of restriction point requiring adhesions (overcome 1st check-point)

Question 10

Define contact inhibition.

Answer 10

the property found in normal cells where they do not grow upon contact with neighboring cells, resulting in a flat layer of cells

Question 11

What can result in the lack of growth factor dependence in cancer cells?

Answer 11

Rb is lost
cyclin B expression increases
loss of p15 and p16
missense mutation in Cdk6 or Cdk4 enzyme preventing binding

Question 12

What is the ploidy of cancer cells and how is it achieved?

Answer 12

anything other than diploid

results from deletions, gene amplification, chromosomal translocation

Question 13

What is angiogenesis?

Answer 13

the recruitment of blood vessels to a tumor to provide nutrients as it grows

Question 14

What happens when tumor cells become invasive?

Answer 14

they enter the bloodstream and travel to distant sites within the organism

Question 15

What occurs when tumor cells metastasize?

Answer 15

they seed tissue at distant sites (secondary sites)

Question 16

What morphology is consistent with a senescent cell?

Answer 16

huge, flat, “fried-egg” appearance, and large cytoplasm compared to nucleus
express acidic form of beta-galactosidase that is detected using colorimeric assay (blue stain)

Question 17

What is the difference between senescence and quiescence?

Answer 17

senescence is irreversible cell arrest whereas quiescence is regulated by growth factors, so it can be reversed by adding more

Question 18

What is triggered when the cell can no longer form t-loops to protect the end of the DNA in normal cells?

Answer 18

cell perceives these as DNA damage and activates p53 –> senescence in normal cells

Question 19

What is triggered when the cell can no longer form t-loops to protect the end of the DNA in cancer cells?

Answer 19

p53 is absent so cells will continue to proliferate and their telomeres will continue to shorten
when telomeres disappear and cell loses coding capacity they undergo crisis

Question 20

Describe the methods cancer cells have used to maintain telomeres.

Answer 20

1. telomerase expression is re-activated (80% of cells)
2. telomerase-independent mechanism called ALT uses homologous driven recombination of the telomeric DNA (10-20% of cells)