Final Exam Flashcards
1
Q
How come we don’t carry thousands of tumors?
A
It is difficult to transform human cells.
We have caretakers, immune system, and our cells need to accumulate mutations to transform.
2
Q
Where would we find the cancerous mutations?
A
Stem cell compartment.
Because stem cells would retain cancerous mutations and pass to later generation of cells.
3
Q
How are stem cells protected from mutations/ harmful environment?
A
- They are isolated anatomically
- They divide, but not very often
- There are DNA repair systems that will either fix errors or call for cell cycle arrest/apoptosis.
- There are additional mechanisms to protect cells.
4
Q
True or False
One mutation is enough to cause cancer in human.
A
False.
Cancer requires accumulation of mutations
5
Q
True or False
A single tumor contains only 1 population of cells with the same mutations.
A
False.
A single tumor contains various populations of cells with different mutations.
6
Q
Why is it a challenge for scientists to effectively treat a tumor?
A
There are many different mutations within a tumor, and it is hard to find a drug that targets all kinds of mutations in a tumor.
7
Q
True or False
Every cancerous cell has tumorigenic capability.
A
False.
Only some, not all.
8
Q
What could have promoted the increased mutation rate?
A
Mutations in caretaker genes (ex: p53)
9
Q
What are the problems that can caused by chromosomal translocation?
A
- Cut off important genes
- Silencing tumor suppressor genes.
- Overexpressing oncogenic activity
10
Q
What is the property of chromosomes in cancer cells?
A
It accumulates abnormalities (translocation)
11
Q
What are two signals that activate p53? What are two outcomes of p53 activation?
A
Signals: DNA damage, hyperproliferative stress
Outcomes: cell cycle arrest, apoptosis.
12
Q
SV40 DNA virus can cause transformation of monkey kidney cells or murine cells into cancerous cells, what would be your approach to identify the protein that promote transformation?
A
- Design two groups: experimental group (infected with the virus) and control group (not infected).
- Collect blood serum from two groups. Experimental group should contain antibodies to viral proteins.
- Infect another cells with the virus and use blood serum from experimental group to identify the viral protein that causes transformation (immunoprecipitation)
- Perform western blot and see the different between two groups (differential display)
13
Q
Why is p53 firstly hypothesized as proto-oncogene?
A
It is expressed in low concentration in normal cells.
14
Q
What is the function of p53?
A
Transcription factor that acts to inhibit tumor progression.
15
Q
What effect does T antigen from SV40 virus have on p53?
A
T antigen sequesters p53.
16
Q
p53 is only active in what form?
A
homotetramer.
17
Q
A dominant-negative mutation of p53 can induce cancer in cell culture, does this mean that heterozygotes (+/-) do not need a second mutation for tumor progression?
A
There is still 1 functional p53 homotetramer out of 16 p53 homotetramer. Hence, it is enough to perform normal function which is inhibit tumor progression.
18
Q
Which type of mutation is the most common p53 mutations in cancer patients?
A
Missense mutations
19
Q
Which p53 domain region are highly mutated?
A
DNA binding domain
20
Q
True or False
Homozygote mutant p53(-/-) mice can complete embryogenesis.
A
True
p53 might not be needed during embryogenesis, and there are other tumor suppressor genes.
21
Q
What is the risk of inherited germ-line mutations in p53?
A
Cause predisposition for distinct cancer in variable ages, aka p53 is universal.
Li-Fraumeni syndrome.
22
Q
What is the expression of p53 in normal cells?
A
Low
23
Q
What effect does increasing exposure to UV on p53 protein levels?
A
p53 protein levels increase upon exposure to UV.
24
Q
Why would the T antigen sequester p53 if the cells behave normally upon viral infection.
A
Viral infection causes the cell to hyperproliferate by sequestering pRb (check point) by T antigen, therefore, hyperproliferation might cause activation of p53 which prevent the cell from proliferating. Therefore, T antigen also needs to sequester p53.
Achieve high proliferation in host cells.
25
How does the cell achieve low concentrations of p53 protein?
p53 is degraded very fast via the ubiquitine system.
26
# **TRUE** or **FALSE**
p53 is only needed occasionally, therefore, p53 is not always synthesized.
False.
p53 is always synthesized all the time
27
Synthesizing protein consumes a high amount of energy; however, p53 is constantly be made and degraded. Why might this be the case?
p53 plays such a critical role in the cell, so it needs to be present all the time to immediately response when the cell needs it.
Also, inhibiting degradation of p53 is easier than synthesizing new p53 proteins.
28
Which E3 ligase ubiquitinate p53 protein?
MDM2
29
What is transcriptional factor that drives the transcription of MDM2?
p53
| p53 activates its own downregulation pathway
30
If you have a missense mutant p53 (where it cannot bind to DNA efficiently). Do you expect to have a **higher/ same/ or lower** levels of p53 compared to wildtype?
**Higher** levels of p53 because it cannot bind to DNA therefore MDM2 cannot be made to degrade p53,
| MDM2 is regulated by p53, andd MDM2 degrades/ubiquitinate p53.
31
What are two agents induce p53 activity?
1. DNA damage
2. Hyperproliferative stress
32
What is the different between ATM and ATR?
ATM is responsible to fix the damage causes to both strands of DNA.
ATR is responsible to fix the damage causes to only one strand of DNA.
33
What are ATM and ATR classified as?
Ser/Thr kinases
34
How does ATR activate Chk1?
ATR bind to the damage site, then it recruits proteins, phosphorylates them and form a complex. The complex then recruits Chk1, and Chk1 is activated via phosphorylation by ATR.
| Do not need to know the name of some proteins
35
# True or False
Phosphorylation is required for p53 to be active.
False.
It is not needed.
36
What is the purpose of phosphorylating p53 by Chk1?
MDM2 cannot bind to phosphorylated p53, and p53 cannot be degraded.
37
What are two phosphorylation targets of Chk1?
p53 (prevent MDM2 from binding)
MDM2 (inactivate it)
38
Expression of which gene tells us that we have crossed the R point in the cell cycle?
E2F
39
Which protein induce the transcription of the ARF gene?
E2F
40
What is the function of ARF?
ARF binds to and sequesters MDM2
41
What does high activity of E2F tell you?
The cell is hyperproliferative.
42
What is a problem when both p16 and ARF are located in the same locus?
Mutation in that locus will disrupt the function of both genes.
43
How are cancer and evolution related to each other?
Mutation on oncogene and tumor suppressor gene reduce one's fitness (unable to reproduce). Therefore, evolution will work agains mutations by providing more genes to fight against cancer.
44
# Radiation used as a therapy treatment for cancer
The spleen is more radiosensitive than the intestine. What would you expect to see if we compare p53 stability between spleen and intestine?
Spleen would have better p53 stability since it is more susceptible to DNA damage caused by radiation.
45
# Radiation used as a therapy treatment for cancer
How could you "help" the intestine to have a more sustained p53 response?
Design a drug to inhibit the MDM2 => increase stability of p53
| block p53 inhibitor
46
Which CKI is regulated by p53?
CKI p21
47
Why does p53 regulate p21, but not p16 in the cell cycle?
p21 controls the part of the cell cycle where DNA damages highly occur.
48
CKI p21 belong to what CKI families?
Cip/Kip
49
Activation of CKI p21 leads to what?
Cell cycle arrest at any stage of the cell cycle.
50
What are the advantages of C.elegans in research studies? (3)
1. Transparent
2. Have few cells (<1000 cells)
3. Cell lineages are tracable, and cell lineage is invariant between worms.
51
# True or False
Cell death cannot be classified as cell fate.
False.
52
What is the difference between apoptosis and programmed cell death?
Programmed cell death is a phenomena
Apoptosis is the mechanism.
53
What is programmed cell death?
Specific cells die in a programmed manner.
A phenomena that kill cells intentionally.
54
What is the advantageous of apoptosis beside killing harmful cells?
Recycle nutrient from dead cells to neighbor cells.
55
Which gene promotes cell death in C.elegans? How does it do that?
Ced-3
Ced-3 encodes for protease which kill cells by degrading their protein
56
What protein does ced-3 encode?
Protease
57
What does it mean when we say apoptosis is an active process?
The cell kills itself by activating ced-3 gene.
58
What is ced-9 function? How does it do that?
Preventing apoptosis by sequestering ced-4
59
How is ced-4 activated?
Death signals come in and sequester ced-9. As a result, ced-4 is free and activates ced-3/
60
Human BCL-2 has the same function of what gene in C.elegans?
Ced-9
61
What do pro-apoptotic signals do?
Release cytochrome C from mitochondria.
62
What is bcl-2 classified as?
Anti-apoptotic
63
Describe the apoptosis signaling pathway.
Proapoptotic causes cytochrome C to release from mitochondria.
Cytochrome C binds to Apaf1.
Procaspase binds to Cyc C-Apaf1 complex, and together they are called apoptosome.
Apoptosome activates caspase, and activated caspase will degrade proteins.
64
What is similarity between apoptosis regulators (anti-apoptotic and pro-apoptotic)?
They are from the same protein family (containing BH domain)
65
What are properties of epithelial cells?
1. Polarized
2. Bound tightly to each other
3. Avascular
4. Immotile
66
What are two cell-cell anchoring junctions?
1. Adheren junction
2. Desmosome
67
What needs to happen in order for cancer to metastasize?
Cell needs to detach from neighboring cells.
67
How does the cancer cell detach from other cells?
Epithelial to Mesenchymal transition (EMT)
67
How can the process of EMT be followed?
Using molecular markers (epithelial markers and mesenchymal markers)
68
Why is there a reduction in Beta-catenin levels, and why not a total reduction when epithelial cells transition to mesenchymal cells?
Although, beta-catenin is involved in cell-cell adhesion, but it also acts as transcriptional factor in the nucleus to induce EMT. (dual function protein)
| EMT: epithelial to mesenchymal transition
68
What are the major molecular-driven changes during EMT?
1. Loss of E-cadherin
2. Cell shape changed driven by Rho GTPases
3. MMPs secretion (matrix metalloproteinases)
69
What are the purposes of N-cadherin?
1. Adhesion to stromal cells (connective tissue)
2. Inducing genes that promote migration
70
Which Rho family member involved in metastasis?
Rac
71
What does Rac do and how?
It promotes actin remodeling by creating an enrichment of actin cytoskeleton in the leading edge.
72
What does MMPs (matrix metalloproteinases) do?
1. It helps cancer cells to invade the ECM by breaking basal lamina and fibers.
2. It helps EMT by cleaving proteins (E-cadherin)
73
What are two ways cancer cell grow on blood vessels?
1. Cooptive growth (grow directly on preexisting blood vessels)
2. Angiogenic growth (grow its own network of blood vessels)
74
What is the Warburg effect?
All cancer cells decrease oxydative phosphorylation and increase glycolysis by 200 fold.
75
Why do cancer cells utilize high amount of glucose compared to normal cells?
Cancer cells use mainly **aerobic glycolysis** which only yield 4 ATP per mol glucose at the end product, therefore, it requires a high amount of glucose to produce more ATP.
76
Warburg observed that majority of cancer cells utilize aerobic glycolysis. What was his initial hypothesis?
Tumorigenesis is driven by an insufficient cellular respiration caused by mitochondrial damage.
77
What do cancer cells utilize aerobic glycolysis?
Allow cancer cells to survive in hypoxic (no oxygen) conditions.
78
# Lecture 19: Metastasis 2 (mitochondria pathway)
What oncogen that we have learned induce the activity of HIF1?
Ras
79
What induces the Wargburg effect?
Oncogenic signaling (Ras)
80
Why do they design drugs that promote recovery of oxidation in cancer cells? Wouldn't those drugs make the cancer cells to obtain more ATP?
The purpose of those drugs is to make cancer cells become dependent of oxygen again, so we can easily kill cancer cells by depriving oxygen.
81
How do cancer cells obtain nutrients (e.g amino acid) in glycolysis?
Modifying intermediate metabolites in glycolysis.
82
What is the role of M2PK (pyruvate kinase)?
Phosphorylating phosphoenolpyruvate to form pyruvate.
83
What are two forms of M2PK? Which form is normally exists in cancer cells?
Tetramer and Dimer.
Dimer form exists in cancer cells.
84
How can cancer cells generate its own nutrients?
Tumor M2PK blocks the reaction of phosphoenolpyruvate to pyruvate which create an accumulation of intermediate metabolites which contains phospholipids and amino acids.
85
What is the main take away from this graph?
Micrometastases are able to proliferate and grow into macrometastases.
86
What are two mechanisms of metastatic tropism? (the tendency to spread to other places/organs)
1. Circulation system
2. Friendly environment to support colonizing cells
87
What does the cancer cell require to perform its usual activities?
Tumor healthy microenvironment.
88
Which molecules help the cancer cells invade the basal membrane and move through the connective tissue?
MMPs. ( Matrix metalloproteinase)
89
# Need to know what MMP does in cancer.
What is the major source for MMP?
Stroma cells
90
TGF-Beta secreted from the stroma does what to the epithelial cancer cell?
Induces EMT
91
Cancer cells from primary tumor are capable of inducing angiogenesis, however, when it invades to a different place it does not immediately induce angiogenesis. Why?
New environment has different sets of signaling which require the cancer cells to take time to adapt, and then it will induce angiogenesis.
**It explains why some tumor have a longer time to colonize in one place (less friendly) compared to other place (more friendly)**
92
How can TGF-Beta function as both oncogene and tumor supressor gene?
At early stage of cancer, TGF-Beta inhibits cell proliferation (TSG).
At late stage of cancer, cancer cell requires TGF-Beta for metastasis (oncogene).
93
What are two types of immunity of the human immune system?
Innate and Adaptive
94
What are two polarized modes of macrophages? Which mode would you expect cancer cells "like" to see in their environment?
1. Pro-inflammatory (classic, M1)
2. Pro-tissue repair (alternative, M2)
Cancer cells prefer pro-tissue repair macrophages because it upregulates growth factors and less phagocytosis ability.
95
What does tumor-associated macrophages (TAMs) do?
Stimulate EMT in cancer cells (invasion, angiogenesism suppression of anti-tumor immune response)
96
How do M2 TAMs stimulate angiogenesis and other metastasis-promoting processes (e.g EMT)?
| TAM = tumor-associated macrophages
TGF-Beta
97
What are 4 cancer therapy?
1. Traditional therapy
2. Targeted therapy
3. Immunotherapy
4. Personalized therapy
98
What is the mysterious Wills factor present in Marmite product? What does it do when they use it to treat leukemia patients?
Folic Acid.
It is accelerating the rate of cancer in leukemia patients (worsen the conditions -> die faster)
99
What is the function of dihydrofolate reductase?
Reduce dihydrofolic acid to tetrahydrofolic acid.
100
Why does cell need folic acid? What does folic acid provide to the cell?
Proliferation.
Nucleotides (purines), amino acids (methionine).
101
What was the first designed drug to treat cancer? What does it do?
Methotrexate (MTX).
It acts as a folate antogonist by binding to dihydrofolate reductase with higher affinity.
102
**Methotrexate (MTX)** is a non-specific drug which will target both normal healthy cells and cancer cells. How does normal cell overcome the inhibition to proliferate induced by this drug?
Normal cell have an alternative route to produce necessities for proliferation, and it is sufficient for normal cell to survive. However, this alternative route is not sufficient for cancer cells to survive since it needs to proliferative rapidly.
## Footnote
Don't need to know the biosynthesis of folic acid
103
What causes poor prognosis in breast cancer patients?
Amplification of HER2 => Overexpression of HER2 receptors
104
# True or False
HER2 gene amplification happens inside the chromosome (DNA).
False.
It happens both inside and outside of the chromosome.
105
What is herceptin? What does it do?
Herceptin is a monoclonal antiobody that targets HER2.
It blocks dimerization of HER2 receptors.
106
What do they find in karyotype of Chromic Myeloid Leukemia patients?
Chromosome 22 is extremely short
107
What is the genetic mechanism that causes fusion of Abl and Bcr?
Reciprocal translocation
107
What is abelson kinase?
A fatty-acid modified and actin-binding non-receptor tyrosine kinase.
108
What inhibits the kinase activity of Abl?
Myristylation (C-terminus)
109
What is the role of Abl?
Phosphorylate focal adhesion proteins
110
How does bcr-abl fusion causes constitutively active abl kinase?
bcr replaces the c-terminus of abl, and abl kinase can no longer be inhibited by the c-terminus.
111
Why do leukemia patients have so much non-functional white blood cells?
Due to increased motility and decreased adhesion caused by overactivated abl => cells become less differentiated and become non-functional when release to blood stream.
112
What is the treatment for leukemia?
Gleevec.
it blocks the ATP binding site of the kinase of BCR-ABL
113
Why is blood a hostile environment to normal cells?
1. Cells are normally anchorage-dependent (anoikis)
2. Shear forces tear cells apart.
114
How do CTLs induce death in the target cell?
1. Perforin secretion
2. FasL secretion
115
What does perforin do?
Forming holes in the membrane and inserting vesicles filled with granzymes.
116
What is FasL? What does it do?
A death signal, triggering apoptotic machinery.
117
How can cancer cell evade the immune response (apoptotic signaling induced by CTLs)?
Cancer cells express death signal (e.g. FasL) on the membrane and kills the CTLs
118
What is CAR T-cell therapy?
Enginerring patients' immune cells to treat their cancers.
| CAR = chimeric antigen receptors
