Cell Cycle Checkpoints and Cancer- Lecture 53 Flashcards
(20 cards)
Define benign cells.
cells that are undergoing uncontrolled proliferation that do not result in any manifest human disease
Define malignant cells.
cells with unlimited cell renewal resulting in cancer
Define primary cells.
cells with a finite lifespan that are directly removed from the body
Define immortalized cells.
cells with an unlimited lifespan
Define transformed cells.
cells that have acquired certain properties
Define tumorgenic cells.
cells that are transformed and have the additional property of being able to form a tumor
Describe the the general characteristics that can identify a cancer cell.
morphology altered metabolism unlimited lifespan anchorage independence loss of contact inhibition no dependence on growth factors changes in ploidy angiogenisis invasive metastisis
How is metabolism altered in cancer cells?
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
Which cancer cells normally become anchorage independent and how do they do so?
epithelial carcinomas
loss of restriction point requiring adhesions (overcome 1st check-point)
Define contact inhibition.
the property found in normal cells where they do not grow upon contact with neighboring cells, resulting in a flat layer of cells
What can result in the lack of growth factor dependence in cancer cells?
Rb is lost
cyclin B expression increases
loss of p15 and p16
missense mutation in Cdk6 or Cdk4 enzyme preventing binding
What is the ploidy of cancer cells and how is it achieved?
anything other than diploid
results from deletions, gene amplification, chromosomal translocation
What is angiogenesis?
the recruitment of blood vessels to a tumor to provide nutrients as it grows
What happens when tumor cells become invasive?
they enter the bloodstream and travel to distant sites within the organism
What occurs when tumor cells metastasize?
they seed tissue at distant sites (secondary sites)
What morphology is consistent with a senescent cell?
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)
What is the difference between senescence and quiescence?
senescence is irreversible cell arrest whereas quiescence is regulated by growth factors, so it can be reversed by adding more
What is triggered when the cell can no longer form t-loops to protect the end of the DNA in normal cells?
cell perceives these as DNA damage and activates p53 –> senescence in normal cells
What is triggered when the cell can no longer form t-loops to protect the end of the DNA in cancer cells?
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
Describe the methods cancer cells have used to maintain telomeres.
- telomerase expression is re-activated (80% of cells)
- telomerase-independent mechanism called ALT uses homologous driven recombination of the telomeric DNA (10-20% of cells)
