Pecorino Flashcards
(386 cards)
1
Q
Hallmarks of cancer
A
- Capability for autonomous growth signals 2. Evasion of growth inhibitory singals 3. Evasion of apoptotic cell death 4. Unlimited replicative potential 5. Angiogenesis 6. Invasion and metastasis
2
Q
Enabling characteristics of cancer
A
Crucial for acquiring the six hallmarks of cancer 1. Genome instability 2. Tumor promoting inflammation
3
Q
Emerging hallmarks of cancer
A
- Reprogramming energy metabolism 2. Avoiding immune destruction
4
Q
Oncogenes - dominant or recessive
A
Dominant - mutation in only one allele sufficient for an effect
5
Q
Tumor suppressor genes - dominant or recessive
A
Recessive - one intact allele generally enough to inhibit growth - Supports “two hit” hypothesis of carcinogenesis
6
Q
Haploinsufficiency
A
Idea that rather than tumor suppressor genes being recessive, only one mutated allele may be enough to induce cancer phenotype - Normal allele produces 1/2 the normal protein product which is not enough to suppress tumor formation
7
Q
Ras function
A
intracellular transducer protein - acts subsequently to binding of a growth factor to its receptor - Involved in transmitting the signal from the receptor through the cell
8
Q
Ras is a ___ protein
A
G protein - activated by exchange of GDP to GTP
9
Q
p53 normal role
A
Coordinates responses of the cell (cell cycle arrest, DNA repair, apoptosis) to different types of stress (DNA damage, hypoxia)
10
Q
p53 is a ___ and acts as a ___
A
- Tumor suppressor gene - Acts as a transcription factor - induces expression of genes required to carry out its function
11
Q
retinoblastoma gene (Rb) is a
A
Tumor suppressor gene
12
Q
Rb function
A
Central role in regulating the cell cycle - Inhibits cell proliferation by binding to and suppressing an essential transcription factor of cell cycle progression
13
Q
Rb activity regulated by
A
Phosphorylation by cyclin D and the cyclin-dependent kinases (4/6)
14
Q
Small localized areas of hypermutation
A
Kataegis
15
Q
One-off cell crisis that shatters chromosomes and result in 10-100’s of genomic rearrangements
A
Chromothripsis
16
Q
Transitions and transversions are what type of mutation?
A
Base substitutions
17
Q
Transitions substitute a ___ for a ___
A
Purine/Purine
18
Q
Transversions substitute ___ for ___
A
Purine/Pyrimidine
19
Q
What is “wobble” and “deceneracy” in the genetic code?
A
3rd nucleotide of a codon may be changed and new codon may code for same amino acid
20
Q
Alpha particles are made of
A
2 protons and 2 neutrons
21
Q
Beta particles are made of
A
electrons
22
Q
X-rays are ___ radiation vs alpha particles that are ___ radiation
A
- low-linear energy transfer (LET) 2. high-LET
23
Q
___-LET radiation more commonly causes DSBs and lead to chromosomal translocations and deletions
A
High
24
Q
Ionizing radiation therapy includes
A
- alpha and beta particles - gamma rays
25
How does ionizing radiation cause DNA damage?
1. Indirect - interacts with atoms, ejects e-, causes an ion to form, interacts with water (radiolysis) --\> ROS 2. DNA directly ionized
26
What are the 3 ROS formed by ionizing radiation therapy
Hyroxyl (OH) Hydrogen peroxide (H2O2) Superoxide (O2-)
27
Which type of UV radiation is the most effective carcinogen?
UVB`
28
\_\_\_ are responsible for the majority of UVB induced mutations
Cyclobutane pyrimidine dimers
29
UVA \_\_\_damages DNA via\_\_\_
- Indirectly - Free-radical mediated damage
30
\_\_\_ transversions are characteristic of UVA damage
G-T
31
Common MOA of chemical carcinogens
Electrophilic (electron-deficient) form reacts with nucleophilic sites (donate electrons) in purine and pyrimidine rings of nucleic acids
32
Example of polycyclic aromatic hydrocarbons (PAH)
Benzo(a)pyrene - major well-known carcinogen in cigarettes
33
Heterocyclic amines are
carcinogens produced by cooking meat
34
One-step DNA repair
- Direct reversal of DNA damage - Removal of alkyl group from the O6 atom of guanine after exposure of DNA to alkylating carcinogens
35
What DNA repair enzyme is involved in one-step DNA repair?
Alkyltransferase
36
What type of DNA damage does NER repair
Helix-distorting lesions - bulky DNA adducts induced by environmental agents (UVV, PAHs)
37
Two subpathways of NER
1. Global genome NER (for helix distortion) 2. Transcription-coupled repair (damage interfering with transcription)
38
Describe the process of repair by NER
1. Lesion + adjacent nucleotide excised by endonucleases 2. DNA polymerase delta/epsilon fills gap with opposite strand as template (proliferating cell nuclear factor is part of polymerase holoenzyme and physically forms ring that encircles and binds the damaged region
39
What DNA polymerase is used in NER
delta(δ )/epsilon(ε)
40
What does NER stand for?
Nucleotide excision repair
41
What genetic disease is characterized by a defect in NER?
Xeroderma pigmentosum (XP)
42
What does BER stand for?
Base excision repair
43
What does BER repair?
Targets chemically altered bases induced primarily by endogenous mechanisms - w/o BER, would cause a point mutation
44
Describe the steps of BER
- DNA damage-specific glycosylases (OGG1 and MUTYH) scan bases for 8-oxoguanine lesions - Lesion is flipped out of the helix and cleaved --\> abasic site - Endonuclease cleaves DNA strand at abasic site - DNA polymerase β replaces nucleotide, ligase fills gap
45
What does PARP stand for?
poly(ADP-ribose) polymerase
46
What role does PARP play in BER
Interacts with single strand break intermediates formed during BER --\> poly(ADP-ribose) chains --\> signals to other DNA repair proteins and leads to modification of histones --\> relaxed chromatin structure for increased DNA accessibility
47
What type of DNA damage does mismatch repair fix
Replication errors that have escaped editing by polymerases - includes repair of insertions and deletions produced as a result of slippage during repair of repetitive sequences and nucleotide mismatches
48
Describe the steps in mismatch repair
1. mismatch recognized by hMSH2/6 and hMSH2/3 2. hMLH1/hPMS2 and hMHL1/hPMS1 recruited 3. Endonucleases and exonucleases removed nucleotides around and including the mismatch DNA polymerases resynthesizes a newly replicated strand
49
What human cancer syndrome commonly has loss of mismatch repair
Hereditary non-polyposis colorectal cancer
50
What are the two types of recombinational DNA repair
Homologous repair and non-homologous end-joining
51
What type of DNA damage does recombinational repair fix
double-strand DNA breaks
52
What does homologous recombination require
The presence of sister chromatids formed during DNA synthesis - template for recombining severed ends
53
What kinase is activated by DSBs in HR?
ataxia telangiectasia mutated (ATM) kinase
54
What substrate does ATM act on
RAD50/MRE11/NBS1 complex --\> 5'-3' exonuclease activity creates 3' DNA ends
55
What aids in nuclear transport of RAD51
BRCA1/2
56
What does RAD51 do in HR
Binds to exposed 3' ends (facilitated by RAD52) --\> exchanges a homologous sequence from a single strand w/in a double stranded molecule (i.e. sister chromatid)
57
Junctions formed as a result of HR
Holliday junctions
58
Which form of recombinational repair is error prone and which is very unlikely to form errors?
1. Error prone = non-homologous end-joining 2. Rare errors = homologous recombination
59
What inherited disease causes defective HR and makes patients sensitive to x-rays?
Ataxia telangiectasia - mutation in ATM kinase
60
Clinically used antimetabolites
Methotrexate, 5-fluorourail (5-FU)
61
5-FU MOA
Antimetabolite Derivative of uracil -\> converted to fluorodeoxyuridylate (F-dUMP) - competes with natural substrate dUMP for catalytic site of thymidylate synthase (inactivates) --\> depletes dTMP and dTTP --\> dUMP and dUTP accumulate --\> DNA synthesis in rapidly dividing cells compromised
62
F-dUMP competes with ___ for catalytic site of \_\_\_\_\_
dUMP thymidylate synthase
63
Thymidylate synthase produces
deoxythymidylate (dTMP)
64
Methotrexate MOA
Antimetabolite Competitive inhibitor of dihydrofolate reductase
65
What does dihydrofolate reductase do?
Regenerates tetrahydrofolate which produces N5N10 methylenetetrahydrofolate that is required in thymidylate synthase reaction
66
Vincristine and Vinblastine bind to ____ and do what?
Tubulin Prevent microtubule assembly
67
Paclitaxel binds to ___ and does what?
Beta-tubulin subunit in polymers Stabilizes microtubules against depolymerization
68
What can assist in making radiation-induced damage permanent?
Oxygen Also, more DS breaks occur in cells irradiated in presence of oxygen than in those without
69
Mechanisms of chemotherapy resistance
Increasing drug efflux Decreasing intake of drug Increasing the number of target molecules within the cell Altering drug metabolism or DNA repair processes
70
MDR codes for \_\_\_\_?
P-glycoprotein (P-gp)
71
P-glycoprotein is\_\_\_\_ and its MOA is \_\_\_\_
Chloride ion efflux pump ATP hydrolyzed --\> conformational change of P-gp--\> drug released extracellularly
72
PARP inhibitors are used in tumors with ____ mutations
BRCA1/2
73
Inhibition of PARP causes impaired...
base excision repair and the accumulation of SS DNA breaks that can lead to DS breaks (normally repaired by homologous recombination pathways
74
BRCA1 or BRCA2 mutations cause deficiency in...
homologous recombination and DS repair
75
Four common types of DNA-binding domains
helix-turn-helix motif Leucine zipper helix-loop-helix motif zinc finger motif
76
T/F: misregulation of a single transcription factor can cause cancer
T
77
AP-1 transcription factor is important in
Processes of growth, differentiation and death --\> therefore plays a role in carcinogenesis
78
AP-1 binds:
12-O-tetradecanoylphorbol-13-acetate (TPA) response element or cAMP response element
79
AP-1 transcription factor is composed of ___ components and can be produced by dimers of proteins from the ___ and ____ families
two; Jun and Fos
80
Jun acts as \_\_1\_\_ of proliferation, Jun B acts as a \_\_2\_\_ in the presence of \_\_3\_\_
1. Positive regulator of proliferation 2. Negative regulator 3. Jun
81
Where in the cell do steroid hormones work?
Pass through cell membrane, bind intracellular receptors in cytoplasm
82
What makes up the histone core?
Two copies of histones H2A, H2B H3 and H4
83
What are the two main types of epigenetic mechanisms
1. Histone modifications
2. DNA methylation
84
What are the main post-translational modifications that can happen to histones?
Acetylation
Methylation
Phosphorylation
Ubiquination
85
What are the two families of enzymes that participated in acetylation of histones?
Histone acetyltransferases (HATs - add acetyl)
Histone deacetylases (HDACs - remove acetyl)
86
What does histone acetylation do?
Neutralizes positive charge on lysine residues --\> relaxes chronmatin --\> more transcription
87
What does histone deacetylation do?
Restores positive charge to lysine in histone tails --\> compacted chromatin --\> less transcription
88
What tumor suppressor gene works in part through acetyl modification of histones? Which enzyme does it recruit to do this?
RB
HDACs
89
Where does DNA methylation occur?
Position 5 of cytosine only at cytosine nucleotides that are situated 5' to guanine nucleotides (CpGs)
90
Where are CpG isloands commonly located? What is their methylation status?
Promoter region of genes
Usually non methylated --\> transcription can occur
91
What enzymes mediate DNA methylation?
DNA methyltransferases (DNMTs)
92
Are DNA methylation patterns inheritable?
Yesh.
93
Areas of chromatin that are relaxed are indicative of ___ and are associated with ____ mutation density.
active transcription
low
94
DNA hypo/hyper methylation has been observed in normally unmethylated/methylated CpG islands of gene promoters in cancer
hypermethylated
unmethylated
95
Gene silencing by ____ may be an important mechanism of carcinogenesis by which critical genes such as ____ are turned off
Methylation
Tumor Suppressor
96
Key genes affected by DNA methylation in cancer
Rb
p16INK4a (inhibits cell cycle)
pro-apoptotic death-associated protein kinase (DAPK)
97
What is a non-genotoxic carcinogen?
Agents that do not mutate genes but are rather epigenetic carcinogens
ex: phenobarbital in mice
98
Is the genome of a cancer cell generally hypo or hypermethylated?
Overall HYPOmethylated
Hypermethylation in specific gene promoters
99
What are microRNAs (miRNA) and what do they do?
small, non-protein coding RNAs
Regulate the expression of mRNA - powerful regulators of gene expression (repress genes)
100
What are telomeres composed of?
TTAGGG sequences bound by shelterin complex
101
What does telomerase do?
Maintains telomere length in certain cell types
Reverse transcriptase that has complementary base pairs to the TTAGG repeats in telomeres
102
Maintenance of ___ important for cancer cell immortality and tumor growth which is commonly accomplished by upregulating \_\_\_\_
Telomeres
Telomerase
103
What drugs are used to target DNA methyltransferases and what do they do?
5-azacytidine (5-azaC), 5-aza-2'-deoxycytidine
Bind DNA methyltransferases --\> significant demethylation
104
What are the four types of proteins involved in transduction of a growth factor signal
growth factors
growth factor receptors
intracellular signal transducers
nuclear transcription factors
105
Many growth factors are
tyrosine kinases
106
What are EGF receptors also called?
ErbB or HER (1-4)
107
What is unique about HER2 compared to other EGFRs
HER2 doesn't bind to a ligand but is a co-receptors for other EGFRs; other EGFRs are receptor tyrosine kinases
108
What are the six steps of EGF signalling
1. Binding of growth factor to receptor
2. Receptor dimerization
3. Autophosphorylation
4. Activation of intracellular transducers - includes RAS
5. Activation of a cascade of serine/threonine kinases (Raf, MEK, MAPK)
6. Regulation of transcription factors for gene expression
109
What does dimerization of EGFRs cause
Changes shape of receptor allowing access of ATP and substrate to the catalytic kinase domain --\> autophosphorylation from on dimer to the other
110
What activates RAS
Son of Sevenless (SOS)
Src homology (SH2 and SH3) domains on Grb2 recognize phosphyorylated EGFR --\> interact with son of sevenless (SOS) --\> activates RAS
111
What kind of molecule is RAS
GTP-binding protein
112
GTP-binding proteins are inactive when they are bound to ____ and active when bound to \_\_\_\_
GDP
GTP
113
What does son of sevenless (SOS) do?
Activates RAS by mediating exchage of GDP to GTP
114
What is farnesylation
Addition of C15 farnesyl isoprenoid lipid to RAS and is required for localizing RAS to the cell membrane
115
What does activated RAS (RAS-GTP) bind to
Raf
116
What kind of molecule is Raf?
Serine/threonine kinase
117
Raf is one of the main effectors of
RAS
118
Raf phosphorylates what?
mitogen-activated protein kinase kinase (MAPKK or MEK)
119
What kind of molecule is MAPKK
Dual tyrosine and serine/threonine kinase
120
What does activated MAPPKK (MEK) do?
Phosphorylates mitogen-activated protein kinases (MAPKs, aka ERKs)
121
What do MAPKs do
Provide cytoplasmic link between activated RAS on plasma membrane and regulation of gene expression because MAPKs can enter the nucleus
122
What is AP-1
Transcription factor - binds DNA and regulates expression of genes involved in growth, differentiation and death
Target of MAPK cascade
123
What does AP-1 bind to
cyclin D gene - critical regulator of the cell cycle
124
What gene families make up AP-1
jun and fos
125
What are the Myc family of molecules
Transcription factors - Myc, Max, Mad, Mxi
Targets of MAPK
126
What are some of the gene targets of Myc?
N-Ras, p53
127
What is phosphatidylinositol 3-kinase (PI3K)
Lipid kinase, effector protein downstream of RAS
128
Interaction of RAS with PI3K results in production of
a second messenger, PIP3
129
What does PIP3 recruite and what kind of molecule is it?
PDK-1
serine/threonine kinase
130
What does PDK-1 do
phosphorylates Akt
131
What is Akt and what does it do?
serine/threonine kinase
anti-apoptotic and survival roles by phosphorylating distinct target proteins; ex: m-TOR
132
What is SRC?
Intracellular tyrosine kinase
Roles in cell proliferation, regulation of cell adhesion, invasion and motility
133
What can activate SRC? What does activated SRC do?
EGF receptor; focal adhesion kinase (FAK)
Activation of SRC leads to disassembly of focal adhesions --\> increased cell motility
Inhibits E-cadherin (important for cell invasion)
134
Oncogenes are dominant or recessive?
Dominant
135
PDGF can act as a oncogene or tumor suppressor gene?
Oncogene - aberrant location in cytoplasm instead of secreted
136
what does the oncogene v-erbB do?
Makes mutated EGFR that triggers cell division w/o EGF binding
137
RAS as an oncogene
Loss of GTPase activity of RAS protein --\> constiutive activation of RAS
138
Most commonly mutated form of B-Raf? What does it do?
V600E
Causes constitutive kinase activity and insensitivity to feedback mechanisms --\> abnormal cell growth
139
How does BCR-ABL work as an oncogene
Fusion protein BCR-ABL maintained in cytoplasm --\> nuclear kinase constitutively activated where it shouldn't be and interferes with normal signal transduction pathways
140
How does Imatinib (Gleevec) work?
Binds ATP-binding pcoket w/in catalytic domain --\> preferential binding to inactive state of kinases
Works against PDGFR, ABL and c-Kit
141
Four stages of the cell cycle
1. G1
2. S phase
3. G2
4. M phase
142
What stages make up interphase
G1, S, G2
143
What is G0
G0 = quiescent state, outside cell cycle
144
Passage through the different phases of the cell cycle is regulated by
Cyclins and cyclin-dependent kinases
145
When cyclins bind to cdks, they ___ the cdk
activate
146
Which cyclins drive progression through G1
Cyclin D + cdk 4/6
147
What does cyclin D do?
regulates expression of cyclin E gene (product is important for G1 to S transition)
148
at cyclin-cdk is important for S phase progression
Cyclin A-cdk2
149
What cyclin-cdk directs G2 and the G2 to M phase transition
Cyclins A, B-cdk1
150
G1 check point leads to cell cycle arresnt in response to what?
DNA damage - ensures DNA isn't replicated in S phase
151
The G2 checkpoint leads to arrest of the cell cycle in response to what
Damaged and/or unreplicated DNA - ensures proper completion of S phase
152
M checkpoint leads to arrest of chromosomal segregation in response to what
misalignment of the mitotic spindle
153
How to cyclins/cdks exert their effects
Phosphorylating target proteins
154
What two processes predominantly control cell cycle progression?
1. protein phosphorylation and dephosphorylation by kinases and phosphatases
2. Specific proteolytic degradation targeted by the addtion of ubiquitin to the proteasome
155
cdks are what type of kinase
serine/threonine
156
What are the four ways cdks are regulated
1. association with cyclins (activates)
2. Associateion with cdk inhibitors
3. addition of phosphate groups that activate cdk activity
4. addition of phosphate groups that inhibit cdk activity
157
What does upiquitin do?
Targets protei for degradation by the proteasome
158
What enzyme catalyzes transfer of ubiquitin to target protein?
ubiquitin-protein ligase
159
What two families of inhibitors are involved in regulating cyclin-cdk activity?
p16ink4a (INK) family
p21 (Cip/Kip) family
160
What makes up the INK family of proteins
p16ink4a, p15ink4b, p18ink4c, p19ink4d
Bind cdks 4/6 and interfere with cdks 4/6 ability to bind cyclin D
161
What are the members of the p21 proteins and what do they do?
p21cip1, p27kip1, p57kip2
Inhibitors that interact with both cyclis and their associated cdks (mainly cdk2 and cycline E) and block the ATP-binding site --\> disables kinase activity
162
What two steps are needed for cdks to become active?
1. dephosphorylation of the inhibitory phosphate groups by cdc25 phosphatases
2. phosphorylation of a central threonine residue Thr161, by cdk-activating kinase (CAK)
163
What is the molecular link for the G1-S phase transition?
RB protein (tumor suppressor protein)
164
RB is a tumor suppressor or oncogene?
Tumor suppressor
165
What does RB regulate
Activity of E2F transcription factor family - physically interferes with the transactivation domain of E2Fs
166
What two main effector proteins bind to RB
HDAC and E2F transcription factor
167
What regulates the interactions b/w RB, E2F and HDACS?
serine/threonine phosphorylation by cyclin D and E families
168
In the absence of a growth signal, RB is in a _____ state and is bound to \_\_\_\_\_
hypophosphyorylated; E2F and HDAC
169
How is RB phosphorylated?
1. cyclin D-cdk4 phosphorylates RB when stimulated by growth factors --\> conformational change --\> releases HDAC
2. Cyclin E gene is expressed when HDAC released from RB --\> cyclin E-cdk2 phosphorylates RB (Ser567) --\> release of E2F
170
What genes are expressed when E2F is released from RB?
cyclin A, thymidylate synthase, dihydrofolate reductase (important for S phase)
171
What does the G2 check point do?
Blocks entry into M phase for cells with DNA damage or that have not correctly completed S phase
172
What does DNA damage activate in the G2 checkpoint?
ATR or ATM
173
What do ATR and ATM do in the G2 checkpoint?
Activated by DNA damage
ATR phsophorylates Chk1
ATM phosphorylates Ch2
174
Other than ATR, what else is needed for full Chk1 activation
claspin (mediator protein)
175
What does Chk1 target?
Cdc25
176
What does Cdc25 do?
Tyrosine phosphatase; regulates cdk activity by removing inhibitory proteins --\> activates cdks
177
What does inhibition of Cdc25 by Chk1 do and when does this happen?
Happens during G2 checkpoint
Blcoks removal of inhibitory phosphate on cdk --\> prevents mitosis
178
Activation of the G2 checkpoint activates ____ and inhibits \_\_\_\_
Chk1; Cdc25
179
What is Plk1 and what does it do?
Protein that targets claspin and Wee1 for degradation, directly inhibits Chk2; causes re-entry into cell cycle (check point recovery) in G2
180
What do unattache chromatid pairs recruit?
Inhibitors of the anaphase-promoting complex (this is a upiquitin-protein ligase that starts anaphase)
181
What are Aurora kinases
serine/threonine kinases
182
What do the Aurora kinases do?
Regulate mitosis - chromosome segregation and the spindle checkpoint
183
Where does Aurora kinase A localize?
Centromeres during interphase; spindle poles and spindle microtubules at beginning of mitosis
184
Where does aurora kinase B localize and when is it highest in activity
Location: first centrometeres, then middle of spindle to between dividing cells
Most active later in mitosis that A
185
Where does aurora kinase C localize and when is it highest activity
spindle poles; active during late mitosis
186
What is Knudson's two-hit hypothesis
The strict definition of a tumor suppressor gene is a gene in which a germline mutation predisposes an individual to cancer
187
BRCA1 and 2 are tumor suppressor genes or oncogenes?
Tumor suppressor
188
What is the primary function of BRCA2?
Recruitment of recombinase RAD51 to double strand DNA breaks
189
What is the function of BRCA1
Roles in homologous recombination including recruitment of RAD51
190
Mutations in BRCA genes can lead do defective ___ that destablizes the genome leading to ____ and \_\_\_\_\_
homologous recombination; chromosomal rearrangements; mutation
191
Most phosphatases are tumor suppressors or oncogenes?
Tumor suppressors
192
PTEN is an oncogene or a tumor suppressor gene?
Tumor suppressor
193
PTEN is what kind of molecule?
Phosphatase with dual specificity - lipid and protein
194
What does PTEN do?
Dephosphorylates PIP3 to form PIP2 --\> antagonizes PI3K activity
195
What is the net result of loss of function of PTEN
Loss of inhibitory dephosphorylation --\> constitutively active PI3K --\> activtes AKT and mTOR --\> induces cell proliferation and inhibits apoptosis
196
What is an example of a kinase that is not oncogenic?
ATM
197
Retinoblastoma is an oncogene or a tumor suppressor gene?
Tumor suppressor
198
What kind of molecule is retinoblastoma
multi-functional protein - transcriptional co-factor and inhibits or induces transcrtiption factor activity
199
What parts of the cell cycle does Rb have it's main role in?
Regulates cell cycle by inhibiting the G1 to S phase transition
200
What critical transcription factor does RB bind to and modulate the activity of
E2F
201
How can RB induce cell cycle arrest
RB stabalizes the Cdk inhibitor p27
202
RB inactivation causes promotion of ____ and _____ via increased expression of ______ target genes _____ and \_\_\_\_\_
chromosomal instability; angiogenesis; E2F; MAD2; VEGF
203
p53 is a tumor suppressor gene or oncogene
tumor suppressor
204
What happens to p53 in absence of cellular stress
Low levels of p53 induce antioxidant activity --\> decreased ROS --\> decreased DNA damage
205
What activates p53?
DNA damage, oncogene activation, cell stress (hypoxia, nucleotide depletion)
206
What are the downstream effects of p53 once activated?
transient or permanent cell cycle arrest, DNA repiar, apoptosis, inhibition of angiogenesis
207
\_\_\_\_\_ is the critical biological function mediating the tumor suppressor function of p53
Apoptosis
208
What is the main regulator of p53 & what type of molecule is it?
MDM2 - upiquitin ligase
209
What signals DNA damage cause by ionizing radiation to p53?
ATM and Chk2 (protein kinases)
210
What does phosphorylation of p53 cause?
Inability of MDM2 to bind to p53 (MDM2 can't inactivate it)
211
What signals cell stress to p53?
ATR and casein kinase II (both kinases)
212
What oncogenes can induce p53 activity?
Ras
213
How does Ras activate p53?
induces the activity of p14arf that sequesters MDM2 to the nucleolus of cells
214
What is the central function of p53?
Cause either transient cell cycle arrest or senescence in response to DNA damage
215
Transcriptional induction of _____ by p53 inhibits _____ and causes a pause in the _____ and _____ transitions of the cell cycle
p21 gene
several cyclin-cdk complexes
G1 to S and G2 to M
216
What are the p53-inducible apoptotic target genes that work via the intrinsic pathway
Bax
NOXA
PUMA
p53/AIP1
217
What are the p53-inducible apoptotic target genes that work via the extrinsic pathway?
FAS
IGF-BP3
DR5
PIDD
218
\_\_\_\_\_, an inhibitor of angiogenesis is transcriptionally regulated by p53
Thrombospondin
219
What tumor suppressor is nicknamed the guardian of the genome?
p53
220
Phosphorylation of ____ results in a preference of p53 to induce pro-apoptotic genes
Ser46
221
Oncogene activation is an upstream inducer of p53 that triggers \_\_\_\_\_
apoptosis
222
What syndrome is characterized by a germline mutation of the p53 gene?
Li-Fraumeni syndrome
223
Does p53 follow Knudson's two hit hypothesis?
No - reduced amounts (haploinsufficiency) of p53 can cause transformation
224
Unlike most tumor suppressor genes, some p53 mutation do not lead to \_\_\_\_\_
loss of function
225
Viral proteins from human adenovirus, papilloma virus and SV40 inactivate ____ and ____ as a common oncogenic mechanism
p53 and RB
226
What happens to a cell during apoptosis?
Shrinks, membrane blebs and buds, chromatin condenses and fragments precisely
227
What molecule is central to both the intrinsic and extrinsic apoptotic pathways?
Caspases (proteases)
228
What is the name caspase derived from?
**c**ysteine-rich **asp**artate prote**ases**
229
What are two examples of death factors that activate the extrinsic apoptotic pathway?
Fas ligand
Tumor necrosis factor (TNF)
230
What happens when ligands bind their death receptor?
Receptors undergo a conformational change --\> heterodimers that tranduce the signal to the cell
231
What does the conformation change in a death receptor expose?
Death domains on the cytoplasmic tail of the receptor
Ex: FADD (Fas-associated death domain protein) and TRADD (TNF receptor-associated death domain protein)
232
Once the death domain binds and adaptor protein in the extrinsic apoptotic pathway, what happens?
Signal transduced to caspases - first = caspase-8
233
What is the first caspase to be activated in the extrinsic pathway?
Caspase-8
234
What is the term for the death ligands + receptors + adaptors + the initiating caspase in the extrinsic pathway?
death-inducing singaling complex (DISC)
235
What are the executioner caspases in the extrinsic pathway?
Caspase 3, 6 and 7
236
What are the target proteins in the extrinsic apoptotic pathway that breakdown the cell?
Nuclear lamins, cytoskeletal proteins (actin and intermediate filaments), kinases, DNase
237
Cleavage of ______ is required for apoptosis induced by TNF
RB
238
What triggers the intrinsic apoptotic pathway?
Stimuli from inside the cell - DNA damage, oxidative stress
239
What family of proteins does the intrinsic apoptotic pathway work through?
Bcl-2 family
240
Anti-apoptotic members of the Bcl-2 family
Bcl-2
Bcl-xL
Bcl-w
A1
Mcl-1
Boo
241
Bax is a \_\_\_\_-apoptotic member of the Bcl-2 family
pro-
242
Bok/Mtd is a \_\_\_\_-apoptotic member of the Bcl-2 family
-pro
243
Bcl-x5 is a \_\_\_\_-apoptotic member of the Bcl-2 family
-pro
244
Bak is a \_\_\_\_-apoptotic member of the Bcl-2 family
-pro
245
Bcl-GL is a \_\_\_\_-apoptotic member of the Bcl-2 family
-pro
246
Bad is a \_\_\_\_-apoptotic member of the Bcl-2 family
-pro
Also BH3-only
247
Bik/Nbk/Blk is a \_\_\_\_-apoptotic member of the Bcl-2 family
pro-
Also BH3 only
248
Bid is a \_\_\_\_-apoptotic member of the Bcl-2 family
-pro
Also BH3-only
249
Hrk/DP5 is a \_\_\_\_-apoptotic member of the Bcl-2 family
-pro
Also BH3 only
250
Bim/Bod is a \_\_\_\_-apoptotic member of the Bcl-2 family
-pro
Also, BH3 only
251
Bmf is a \_\_\_\_-apoptotic member of the Bcl-2 family
Pro-
Also, BH3 only
252
Noxa is a \_\_\_\_-apoptotic member of the Bcl-2 family
Pro-
Also BH3 only
253
Puma/ Bbc3/BNIP3/BNIP3L is a \_\_\_\_-apoptotic member of the Bcl-2 family
Pro-
Also BH3-only
254
Bcl-2 is a \_\_\_\_-apoptotic member of the Bcl-2 family
Anti-
255
BclxL is a \_\_\_\_-apoptotic member of the Bcl-2 family
Anti-
256
Bcl-w is a \_\_\_\_-apoptotic member of the Bcl-2 family
257
A1 is a \_\_\_\_-apoptotic member of the Bcl-2 family
Anti-
258
Boo is a \_\_\_\_-apoptotic member of the Bcl-2 family
Anti-
259
Where are the apoptotic mediators stored for the intrinsic pathway?
Intermembrane space b/w the two mitochondrial membranes
260
What is MOMP?
Mitochondrial outer membrane permeablilization - release of apoptotic mediators from the mitochondrial compartment
261
When the intrinsic pathway is activated, which apoptotic factors are activated first?
BH3 only proteins - Bid and Bim
262
What do Bim and Bid activate in the intrinsic apoptotic pathway?
Bax
263
What does Bax do when it is activated in the intrinsic apoptotic pathway?
Transolcates from cytoplasm to outer mitochondrial membrane --\> increases the permeability of the outer membrane
264
What does Bcl-xL do?
Breaks apart Bax ogliomers
i.e. antiapoptotic
265
What are released from the mitochondrial into the cytoplasm during the intrinsic apoptotic pathway
cytochrome C, pro-caspase-9
266
What makes up the apoptosome in the cytoplasm of a cell
Cytochrome C, procaspase-9, dATP bound to Apaf-1
267
What activates procaspase-9
Apaf-1 (protein co-factor)
268
What is the first caspase activated in the intrinsic apoptotic pathway and what does it activate
Caspase-9 activates 3, 6 and 7
269
What are IAPs?
inhibitors of apoptosis proteins
270
Smac/DIABLO is a ____ and eliminates \_\_\_\_\_
Regulator of apoptosis released from mitochondria; eliminates inhibition of apoptosis by IAPs
271
NF-kB is a potent promotor/inhibitor of apoptosis and induces the transcription of\_\_\_\_\_
inhibitor; IAPs
272
XIAP directly binds to and inhibits the activity of ____ and \_\_\_\_
Caspase 3 and 7
273
\_\_\_\_\_ and _____ compete for binding to XIAP
Smac/DIABLO and caspase-9
274
Caspase-8 can activate ____ to also stimulate the intrinsic apoptotic pathway
275
p53 plays a role in apoptosis in both the nucleus and cytoplasm. These functions are linked by \_\_\_
PUMA (p53 upregulated modulator of apoptosis
276
Apoptotic signals stimulate ______ in normal cells while apopotitc signals stimulate _____ in cancer cells
Procaspase processing;
Cessation of IAP inhibition of processed caspases
277
What are the TRAIL receptors?
Subfamily of TNF receptors (aka death receptors)
278
What is TRAILR's ligand?
TNF-related apoptosis-inducing ligand
279
What does TRAIL do?
Stimulates apoptosis regarless of p53 gene profile in cancer cells but not most normal cells
280
Alterations in the intrinsic/extrinisic apoptotic pathway are more common during carcinogenesis
intrinsic
281
What is autophagy
recycling system for the cell - proteins and damage organelles targeted by lysosomes, cells reuse products of degradation
282
Mitotic catastrophe is caused by \_\_\_\_
aberrant mitosis
283
In the absence of Wnt, what complex is formed in the cell?
Degradation complex - axin + adenomatous polyposis coli (APC) protein + glycogen synthase kinase 3-beta (GSK3beta) + casein kinase I (CKI)
284
Without Wnt, what transcriptional cofactor is phosphorylated by the degradation complex in the cell?
β-catenin (which is also ubiquitinated --\> flags β- catenin for degredation by the proteasome
285
When Wnt binds to the 7-pass transmembrane receptor ____ and co-receptor \_\_\_\_\_\_, a conformational change is induced and the co-receptor is phosphorylated by \_\_\_\_\_
Wnt binds frizzled + LRP ---\> cytoplasmic tail of LRP is phosphorylated by CKI
286
When LRP is phosphorylated, what does it recruit and what is the result of this
recruits axin --\> disrupts assembly of the degradation complex --\> β catenin escapes degradation and moves to the nucleus
287
What family of transcription factors does β-catenin act as a co-activator for?
Tcf/LEF family
288
What are examples of target genes that Tcf/LEF transcription factors regulate
c-myc, cyclin D, genes that code for adhesion molecules from the ephrin (Eph\_ receptor family
289
Other than β-catenin, what other proteins are needed for activation of the target genes of the Tcf/LEF family of transcription factors
Bc19 (legless) and Pygopus
290
Mutations that result in the constitutive activation of the Wnt pathway are responsible for 90% of what human cancer
colorectal cancer
291
Loss of what tumor suppressor gene is considered the initiating event in most colorectal cancers in people and is sufficient to induce adenomas in mice?
APC
292
The Hedgehog signaling pathway plays important roles in what processes
embyronic development, tissue self-renewal and carcinogenisis
Mainly inactive in adults
293
What are the three members of the hedgehog proteins
Sonic, Desert and Indian
294
What two transmembrane proteins are responsible for signal transduction from hedgehog
patched and smoothened
295
In the absence of hedgehog, ____ is localized in the cilia and inhbitis ____ which prevents its localization to the cilia and supresses the pathway
patched localized in cilia, inhibits smoothened and prevents it from localizing to the cilia
296
Without hedgehog, what is sequestered by a protein complex in the cytoplasm that induces its cleavage by proteasomes? What type of molecule is this?
Gli
Zinc finger transcritpion factor
297
What does hedgehog bind to and what happens when it does
hedgehog binds patched --\> smoothened relocates to the cilia and transduces a signal into the cell --\> protein complex dissociates and releases Gli --\> nucleus to regulate expression of hedgehog target genes
298
What are examples of hedgehog target genes
Cyclin Ds, Bcl2, VEGF and Snail
299
Patched is a (tumor suppressor/oncogene); patients with mutated patched have what syndrome
tumor suppressor; Gorlin syndrome (predisposed to skin, cerebellar and mm tumors)
300
What group of proteins can repress the transcription of many developmental regulators and are therefore involved in maintenance (i.e. inducing and maintaing stem cell state) and repression of stem cells (including cancer stem cells)
polycomb group of proteins (PcG)
301
Cyclopamine inhibits what pathway by inhibiting what transmembrane protein?
(fun fact - what plant does this come from and what does it do to sheep?)
inhibits hedgehog pathway by inhibiting the transmembrane protein smoothened
comes from wild corn lilies - teragoen that causes cyclopia in lambs (hence the name cyclopamine)
302
What are the predominant extracellular matrix proteins that make up the basement membrane
laminins, type IV collagen and proteoglycans
303
What are the major steps of metastasis?
Intravasation, transport, extravasation and metastatic colonization
304
What are the characterizations of EMT
* loss in cell polarity
* deconstruction of epithelial cell-cell junctions
* changes in cell shape
* downregulation of epithelial markers (e-cadherin)
* upregulation of mesenchymal proteins (N-cadherin)
* secretion of specific proteases
* increased cell protrustions and motility
305
What signals from the tumor stroma induce EMT in neighboring tumor cells
hepatocyte growth factor (HGF) + MET receptor
EGF + EGFR
PDGF + PDGF-R
TGF-β + TGFR
All are receptors are TKRs
306
What signal transduction pathways are activated in EMT
MAPK and PI3K
307
What transcription factors are activated in EMT
Twist, Snail, slug, ZEB1, Goosecoid and FOXC2
308
What does Snail do?
Transcription factor involved in EMT
binds E-box sequences in epithelial genes (ex: promoter region of E-cadherin promoter) and recruits polycomb repressor complex --\> histone modifcation and epigenetic regulation to repress gene expression
309
What type of proteins are cadherins?
calcium dependent transmembrane glycoproteins
310
Who do cadherins interact with the cytoskeleton
via catenins
311
What is the predominant cell adhesion molecule (CAM) in epithelial cells? Is it a tumor suppressor or promoter?
e-cadherin
tumor suppressor - secures cell-cell adhesion and suppresses metastasis
312
What do integrins do?
mediate cell-ECM interactions and intracellular signal transduction
313
After binding ligand, what doe integrins do?
cluster in the membrane and affect the cytoskeleton through interaction with acting-binding proteins and specific kinases (ex: focal adhesion kinase (FAK))
314
What does focal adhesion kinase (FAK) do?
mediates cell motility through recruitment of Src and activation of the RAS pathway
315
What is anoikis and how do intergrins play a role in it?
anoikis = apoptosis triggered in response to lack of ECM ligand binding and loss of cell adhesion
integrins w/o suitable ECM ligans recruit caspase-8 to membrane and trigger apoptosis
316
What proteases are involved in EMT?
serine proteases and matrix metalloproteinases (MMPs)
317
What do matrix metalloproteinases (MMPs) do?
cleave the extracellular domain of e-cadherin --\> contribute to the loss of epithelial cell-cell junctions seen during emt
318
What is the usual source of MMPs
Some tumor cells can synthesize MMPs but more often tumor cells induce surrounding stromal cells to make MMPs
319
What protein can be upregulated on the membrane of tumor cells and induces production of MMPs in adjacent stromal cells?
extracellular matrix metalloproteinase inducer (EMMPRIN)
320
What regulates the function of MMPs
endogenous tissue inhibitors (TIMPs)
321
MMPs are what type of proteinase
zinc-dependent proteinases
322
What steps are needed for a tumor cell to undergo intravasation?
* attach to the stromal face of the vessel
* degrade the vessel basement membrane (absent if invading lymphatics)
* pass between endothelial cells (transendotheial migration)
323
What are selectins and how do they play a role in EMT?
selectins = calcium dependent transmembrane receptors that mediate interactions with cancer cells by binding glycoprotein ligands expressed on adhering cells
role in attachment of cancer cells to endothelium (esp. E-selectin)
324
What are disseminated tumor cells (DTCs)
cells that have spread but have not yet colonized
325
What role do exosomes play in cancer metastasis
carry protein and nucleic acid - may help to prepare the premetastatic niche for cancer cells to colonize (bone marrow cells do this, too)
326
What are examples of metastasis suppressor genes
NM23, mitogen-activated protein kinase kinase 4 (MKK4)
327
What are examples of miRNA that suppress metastasis
miR-335 and miR-126
328
What are Marimastat and Neovastat
metalloproteinase inhbitors (MPIs)
329
What is cabozantinib (Cometriq)?
TKI that targets c-MET and VEGFR (approved for treatment of thyroid cancer in people)
330
What are the anti-angiogenic factors
angiostatin, endostatin, prolactin, p53, thrombospondin-1 and -2
331
What are the pro-angiogenic factors
VEGF
FGF
HGF (hepatocyte-derived GF)
EGF
PDGF
332
What are the three families of endothelium-specific growth factors and their receptors
1. VEGF/VEGFR
2. angiopoietins and Tie receptors
3. ephrins and ephrin receptors
333
Which specific VEGF and receptor are responsible for the majority of angiogenic effects
VEGF-A + VEGFR-2
334
Which VEGF and receptor play a role in the development of the lymphatic vascular system
VEGF-C + VEGFR-3
335
What does VEGFR-1 do
Binds VEGF-A and restricts angiogenic response by VEGFR-2 (i.e. inhibitory)
336
Plasminogen can be cleaved by _____ to release the angiogenic inhibitor \_\_\_-.
proteinases (including MMPs); releases angiostatin
337
What is angiostatin's endothelial cell surface receptor and what is the effect on angiogensis of it binding to its receptor
receptor = annexin II
effect: inhibits angiogenesis
338
Endostatin is \_\_\_\_\_and is proteolytically released by \_\_\_\_\_
is a fragment of collagen XVIII;released by elastase and cathepsin
339
What does endostatin do?
blockes MAPK activation in endothelial cells and blocks MMPs
340
What is concomitant resistance?
primary tumor suppressing growth of dormant metastases
throught to be partly due to production of angiogenic inhibitors (angiostatin and endostatin) by primary tumors
341
In areas of low oxygen concentration, angiogenesis is induced via \_\_\_\_
hypoxia-inducible factor-1α (HIF-1α)
342
What regulates the activity of HIF?
Oxygen concentration - at normoxic levels (20%), HIF-1α is rapidly degraded (i.e. not regulated at level of mRNA expression)
343
\_\_\_\_\_ is an important regulator of HIF-1α degradation
von Hippel-Lindau (VHL)
344
What is the first step in targeting HIF-1α for degredation
under normoxic conditions, the enzyme prolyl 4-hydroxylase hydroxylates HIF-1α (enzyme directly binds and links molecular oxygen to specific proline residues on HIF-1α)
345
\_\_\_\_\_ binds hydroxylated HIF-1α and adds \_\_\_\_
VHL; adds upiquitin --\> targets it for proteosomal degradation
346
Why is HIF-1α not hydroxylated under hypoxic conditions
4-hydroxylase is inactivated
347
When HIF-1α is transported to the nucleus, what does it activate?
target genes via the hypoxia response element (HRE) - VEGF gene contains HRE in its promoter region
348
What oncogenic proteins have been shown to upregulate VEGF
RTKs - EGFR
intracellular TKs - Src
Intracellular transduers - Ras
Transcription factors - Fos, Jun
349
What is an example of a tumor suppressor gene that is involved in angiogensis? How do mutations in it cause angiogenesis to be favored?
p53
normally p53 activates the promoter for the angiogenic inhibitor thrombospondin-1 - mutations in p53 cause decreases in thrombospondin-1
350
What enhances the signal from VEGFR-2 after it binds VEGF-A and what transduces it to the nucleus?
neuropilin-1 (Nrp1) enhances signal
MAPK cascade transduces it
351
During angiogenesis, VEGFR-2 activation in the tip cells induces the expression and release of _____ which binds its receptor _____ on neighboring cells which is transported to the nucleus where it acts as a transcription factor to repress ____ and induce \_\_\_\_\_.
Delta-like 4 (DDL4) which binds the Notch receptor
represses VEGFR-2, induces VEGFR1
352
When VEGFR-1 is activated, what is its effect
acts as a VEGF trap - reduces the amount of VEGF that can bind VEGFR2 --\> growing BV sprout moves along the VEGF gradient
353
What is vasculogenic mimicry?
tumor cells act as endothelial cells and form vascular-like structures
354
what is vasculogenesis
differentiation and proliferation of endothelial cells from endothelial progenitor cells
355
Are drugs that target angiogenesis (i.e. anti-angiogenic therapy) cytotoxic or cytostatic?
Cytostatic - require long-term continuous admin
356
What is the recombinant humanized mAb that recognizes VEGF-A
bevacizumab (Avastin)
357
What drug acts as a soluble decoy for VEGF by expressing both VEGFR-1 and -2
Aflibercept (VEGF-trap)
358
What does Sorafenib (NExavar) target
TKI - VEGFR, PDGFR, FLT3, Kit and Raf
359
What does Sunitinib target (SU-11248)
TKI: VEGFR, PDGFR, FLT3 and Kit
360
T/F multiple drugs that directly targe HIF have been approved in human medicine
F - only durgs that indirectly target the HIF pathway have been approved (ex: bortezomib)
361
Herceptin is a therapeutic Ab targeted against ____ and has shown to be antiangiogenic by \_\_\_\_
targets ErbB2
inhibits the production of angiogenic inducers (TGF-α and angiopoietin-1) and upregulates angiogenic inhibitors (thrombospondin)
362
Depletion of ____ may contribute to tumor development by interfering with both nucleotide synthesis and DNA methylation
folate
363
\_\_\_\_\_ upregulates the expression of nearly all of the core enzymes of glycolysis and inhibits the expression of some enzymes involved in the Krebs cycle and oxidative phosphorylation; this indicates it participates in what in cancer cells?
HIF-1α; Warburg effect
364
The warburg effect describes what
increase in aerobic glycolysis that occurs in some tumor cells
365
how does Tamoxifen work?
selective estrogen receptor modulator (SERM) - blocks estrogen binding to its receptor
366
how do aromatase inhibitors work? what population of women with breast cancer may benefit most from these drugs?
inhbit the enzyme aromatase that converts androgens to estrogen
post-menopausal women - aromatase is their main source of estrogen
367
What is an example of an aromatase inhibitor
Aromasin (exemestane)
368
Most cancer cells do not epxress ____ and are therefore largely invisible to the immune system
B7 (aka CD86)
B7 is the ligand on the APC that interacts with CD28 on the T cell and is needed to activate the T cell
369
Programmed death 1 protein (PD-1) binds to \_\_\_\_\_on APCs and _____ on many cell types including tumor cells
PD-L2 on APCs
PD-L1 on many cells
370
Exposure to _____ produced by _____ induces PD-L1 expression on cells
IFNγ produced by activated T cells
371
What does the PD-1 axis interfere with
Signaling mediated by the t-cell antigen receptor
372
The interaction of PD-L1 on tumor cells and its receptor on activated effector T cells recruits ____ inactivates _____ blocking the production and secretion of molecules required for a cytotoxic response
recruits SHP-2 phosphatases, inactivates the PI3K cascade
373
What are the phases of immunoediting?
Elimination of the cancer
Equilibrium - selection of less immunogenic tumor cells during an anti-tumor response
Escape - tumor evades the immune system
374
What has a direct effect on CD4+ T cells (inhibits their proliferation and their production of cytokines)
IL-10
375
What dendritic cell vaccine was made for treatment of prostate cancer?
Provenge (sipuleucel-T)
376
What is the main disadvantage of dendritic cell vaccines?
labor-intensive and expensive
377
What theapeutic checkpoint blockade is a fully human mAb against CTLA-4
ipilimumab
378
CTLA-4 is what and is constitutively expressed on what cells?
protein receptor that functions as an immune checkpoint and downregulates immune responses. CTLA4 is constitutively expressed in regulatory T cells
379
What does CTLA-4 bind to?
Binds to CD80 (B7) on T cells with more affinity and avidity than CD28 on APCs does
(CTLA-4 causes inhibitory signals to T cells, CD28 causes stimulation of T cells)
380
Pembrolizumab (keytruda) targets what? What other drug also targets this?
PD-1
nivolumab (Opdivo)
381
What two important oncogenes can induce inflammatory cytokines?
RAS and c-myc
382
What are the key immune cells of chronic inflammatory responses
macrophages
383
Many inflammatory pathways involved in carcinogenesis lead to the activation (via inflammatory cytokines) of \_\_\_\_\_
transcription factors STAT and NF-κB
384
STAT is a transcription factor that promotes cell growth by _____ and increases survival by \_\_\_\_\_
induces the cyclin D, cyclin B and myc genes
increases survival by inducing anti-apoptotic genes such as Bcl-2
385
How does NF-κB inhibit apoptosis?
induces anti-apoptotic gene expression (induction of Bcl-XL, cellular inhbitor of apoptosis (c-IAP) and cFLIP)
386
NF-κB activates _____ and thus plays a role in regulating the cell cycle
cyclin D1 gene
