Neoplasia Lec 3 Flashcards
what are the 6 hallmarks of cancer
- evading apoptosis
- sustained angiogenesis
- self-sufficiency in growth signals
- insensitivity to anti-growth signals
- tissue invasion and metastasis
- limitless replicative potential
what does G0/G1 in the cell cycle do
cell is quiescent or accumulating building blocks required for division
what does S in the cell cycle do
cell replicates DNA
what does G2 in the cell cycle do
cell assembling machinery for chromosomal segregation and cytokinesis
what is M in the cell cycle
mitosis
what is the cell cycle and what is it driven by
- Determines when cell moves from one phase to next
- Driven by cyclins paired with (CDKs)
- R point (restriction) is critical time point when cells decide to enter or not into cycle
what do checkpoints mean in the cell cycle
Block the passage into next cycle when cells not ready
what does hallmark 1 (self-sufficiency in growth signals) do
- Activation of kinase signal transduction that respond to mitogenic signals (GFs)
GF receptors are RTKs - Activation of RTK
–> Gain of function
—— EGFR in lung cancer
–> Amplification
—— HER2 in breast cancer
what does Hallmark 2 (resistance to growth inhibitory signals) do
- May arise through loff of expression of growth inhibitory proteins (tumor suppressors)
–> TGF-b, p53
–> p16(INK4a)
–> E2F (transcription factor in G1/S)
what does Hallmark 3 (evading apoptosis) do
- Disruption of apoptotic pathways preventing cell death upon DNA damage or cell cycle checkpoint activation
- Tumor suppressors
–> P53 - transcription factor
–> P21 - CDK inhibitor
–> BAX - pro-apoptotic regulator
what does Hallmark 4 (limitless replicative potential) do
- Normal cells can divide only 40-60x (Hayflick limit)
- Telomere shortening leads to chromosomal abnormalities and cell death
–> Loss of genes near end of chromosome - Tumor cells overexpress telomerase, leading to immortalization
what does Hallmark 5 (sustained angiogenesis) do
- Tumor cells can trigger angiogenesis (neovascularization)
- Solid tumors can’t grow beyond 1-2 mm without blood supply
–> Deficient in oxygen/nutrient
–> Unable to get rid of metabolic waste (lactic acid/CO2) - Tumor cells produce VEGF to promote angiogenesis
– HIFa
—> Transcription factor for hypoxia genes (VEGF)
– VHL - von hippel lindau
—> Tumor suppressor E3 ligase for HIFa
what does Hallmark 6 (tissue invasion and metastasis) do
- Adhesion and invasion of basement membrane
- Passage through extracellular matrix
- Invasion of vascular basement membranes and vascular ingress (intravasation)
- Travel via the vasculature
- Adhesion to basement membrane at destination
- Invasion of vascular basement membrane and vascular exit (extravasation)
- Metastatic deposit
- Angiogenesis and growth
what are the three steps in multistep carcinogenesis
- initiation
- promotion
- progression
what is the initiation step
- Exposure of cells to appropriate doses of carcinogenic agent
- Irreversible change in genome
- Amount of total exposure matters