TBL 4 Carcinogenesis Flashcards
____ is regulated cell death that is not associated with inflammatory response, whereas ____ is unregulated cell death that is associated with inflammation.
Apoptosis is regulated cell death that is not associated with inflammatory response, whereas Necrosis is unregulated cell death that is associated with inflammation.
What are the two phases in apoptosis?
Latent phase: Death pathways are activated, but cell remains the same.
Execution phase: Apoptotic morphological structures begin to occur.
_____ is the enzyme used to tag DNA with an extra fluorescently-tagged base at the __ ends.
It is used to detect apoptotic cell death.
TUNEL is the enzyme used to tag DNA with an extra fluorescently-tagged base at the 3’ ends.
______ are enzymes which execute the apoptotic mechanisms directly.
Caspases
What is the amino acid on the catalytic site of Caspases?
Cysteine
_____ caspases trigger the cell death programmes and contain additional domains at their N-terminals.
Initiator
Caspase 2 and 9 contain _____ whereas Caspase 8 and 10 contain _____ domains.
2 and 9 – CARD
8 and 10 – DED
What cleaves and activates the effector caspases?
Initiator caspases
Effector caspases can activate enzymes known as _______ which breaks down DNA into regular fragments for apoptosis.
Caspase-activated DNase (CAD)
Fas is a death receptor found on many cells. It is (upregulated/downregulated) on infected cells. It is activated by its ligand, ____.
upregulated, FasL
FADD is an adaptor protein that recruits _____ to form the death-inducing signalling complex (DISC).
Proscaspase 8
The FLIP protein inhibites the death receptor activation of ______, by competitively binding to FADD on the trimerised receptor.
Caspase 8
Death by default refers to programmed cell death initiated by endogenous signals that are dependent on (organelle).
Mitochondria
The apoptosome is a large complex which contains Apaf-1, ATP, cyt-c and initiator procaspase __.
9
In the apoptosome, the Apaf-1 contains CARD which binds to _____; ATPase domain which binds to ____; WD-40 repeats which bind to ____.
Caspase 9; ATP; cyt-c
The binding of cytochrome-c to the ____ repeats on the Apaf-1 cause it to assemble into a wheel-like heptamer.
WD40
Seven procaspase 9 molecules are brought together to the centre of the wheel, binding to CARD domains on the Apaf-1, and this allows for _____ to occur.
transcleavage
Caspase 8, which is involved in the (extrinsic/intrinsic) pathway and Caspase 9, which is involved in the (extrinsic/intrinsic) pathway both activate Caspase _.
extrinsic; intrinsic; 3
Caspase 8 also cleaves ____ protein, which enhances the release of mitochondrial proteins.
(costimulation between both pathways)
Bid
The Bcl-2 family of proteins help to modulate the (organelle) intrinsic pathway of apoptosis.
mitochondrial
The domain that all Bcl-2 proteins have in common is ___, and they therefore use this as a protein-protein interaction domain between different members of the family.
BH3
(Anti/pro-apoptotic) Bcl-2 proteins include the Bcl-2, Bcl-xL.
(Anti/pro-apoptotic) Bcl-2 proteins include the Bid, Bax, Bad.
Anti; Pro
The PI3’-kinase pathway promotes cell survival and proliferation. It is therefore (anti/pro-apoptotic.)
Anti
Phosphatidylinositol 3’-kinase is a ___ kinase. It converts PIP2 to ___.
lipid; PIP3
PIP3 is recognised by the PH domain of the protein kinase ___/___, which is (anti/pro-apoptotic).
PFB/Akt, anti
PKB protein kinase phosphorylates Bad, which is then (activated/inactivated).
Bad is a (anti/pro-apoptotic) protein, hence inactivated Bad causes the cyt-c to (leave/remain) in the mitochondrial membrane.
Inactivated; pro; remain
PTEN is a ____ phosphatase, which dephosphorylates PIP3 back to ___, to counteract the effects of PI3-K signalling pathway.
lipid; PIP2
___ gene is a tumor suppressor gene, but unlike normal TS genes, it requires only ONE copy of the mutated gene to cause an effect. i.e. it acts in a dominant manner. This term is called haploinsufficiency.
p53
Inherited breast cancer is caused by inherited mutation in the ____ genes.
BRCA1/BRCA2
Chromosomal __________ occurs between chromosomes 9 and 22 in Chronic Myeloid Leukemia (CML).
This leads to a new fusion gene BCR-ABL1 on chromosome ___. This gene codes for a continually active ___________ (protein), leading to constant activation of downstream signalling cascades and overproduction of _______ (cells).
Chromosomal TRANSLOCATION occurs between chromosomes 9 and 22 in Chronic Myeloid Leukemia (CML).
This leads to a new fusion gene BCR-ABL1 on chromosome 22. This gene codes for a continually active TYROSINE KINASE RECEPTOR (protein), leading to constant activation of downstream signalling cascades and overproduction of GRANULOCYTES (cells).
Imatinib (Glivec) is a ___________ inhibitor, which is therefore used in the treatment of CML to prevent the overproduction of granulocytes.
Tyrosine Kinase
There are three methods to monitor disease progression of Leukemia:
1) Cytogenics; 2) FISH; 3) RT-PCR.
Amongst the three, _______ is the most accurate and sensitive, and is therefore used when the number of gene transcripts is greatly reduced.
RT-PCR
Chromosomal __________ occurs between chromosomes 15 and 17 in Acute Promyelocytic Leukemia (APML).
This leads to a new fusion gene PML-RARA. This gene codes for a protein which binds too (strongly/loosely) to DNA via enhanced interaction with co-repressors, (blocking/activating) transcription.
translocation; strongly; blocking
____ responds to all trans-retinoic acid (ATRA) therapy, which dissociates co-repressors, allowing for normal transcription and cell differentiation.
APML
Patients with K-ras mutation will lower the likelihood of response to _____ (drug) for colorectal cancer.
Cetuximab
Patients with EGFR mutation has a (greater/lower) likelihood of response to Geftinib for _______ (cancer).
greater; non-small cell lung cancer
Patients with _____ (gene) mutation is unlikely to respond to Dasatinib in CML.
BCR-ABL1
______ is the most vulnerable period of the cell cycle as cells are more easily killed, DNA damage cannot be repaired and gene transcription is silenced. (reduced metabolism)
Mitosis
___ phase occurs when the cell leaves the cell cycle and stops dividing.
G0
___ phase (10h) occurs after mitosis, and serves as a decision point whether the cell is to continue in the cell cycle.
G1
_ phase involves ______ ensuring that in the following mitotic division, the daughter cells possess the same amount of DNA as the parent cell originally had.
S; DNA Replication
In S phase, besides DNA replication, _____ synthesis is also increased. There is also replication of ______. In the case of mitochondria, the process needs to be coordinated with the replication of ____.
protein; organelles; mtDNA
___ phase (4h) occurs after DNA replication, and serves as a decision point.
G2
The centrosome consists of two ______ at right angles to each other. Each of them are made up of _______ microtubules.
centrioles; 9 triplets
The mother centriole and the daughter centriole are held together by ____________.
Interconnecting fibres
In the G1 phase, the mother and daughter centrioles ______, and ________ in the S phase, generating complete and new sets of centrioles by the time of mitosis.
separate; duplicate
The centrioles form a cloud of protein structures providing ________ sites for microtubules.
nucleation
In prophase, the ______ condenses to prevent DNA entanglement during segregation.
The duplicated ______ migrate to opposite poles of the nucleus and organise the assembly of ________.
chromatin; centrosomes; spindle microtubules
The DNA double helix first wraps around _____-charged _____ octamers with the presence of linker DNA.
positively; histone
The 10nm chromatin fibre further condenses around ___ histones and ______ DNA to form 30nm chromatin fiber.
H1; Linker
The 30nm chromatin fibre associates with ____ proteins and non-histone proteins to form ______ domains, which coil and condense further to form metaphase chromosomes.
scaffold; looped
____ are radial microtubule arrays which form around each centrosome, followed by meeting of radial arrays in prophase.
ASTERS
At _______ (stage), the nuclear membrane breaks down and the chromosomes attach to the mitotic spindle via _______ protein at the centromere region.
(Early) Prometaphase; kinetochore
At (early/late) Prometaphase, microtubule from opposite poles are captured by sister kinetochores. Chromosomes migrate to the equator of the cell.
Late
_______ senses when the kinetochore is bound to the microtubules.
CENP-E
At _______(stage), chromosomes are aligned singly at the equator of the spindle along the metaphase plate.
Metaphase
______ holds the sister chromatids together before segregation.
Cohesin
At Anaphase A, _____ is broken down, as kinetochore microtubules shorten, pulling the daughter chromosomes towards the opposite spindle poles.
Cohesin
At Anaphase B, daughter chromosomes migrate towards opposite poles, and the ________ migrate apart as the cell (elongates/shortens) due to the sliding of polar microtubules.
centrosomes; elongates
At ______ (stage), contractile ring of _____ and _____ filaments is assembled at the equator of the cell.
Telophase; actin and myosin
The M phase checkpoint occurs at _____ (stage), and checks for completion of chromosome alignment and spindle assembly.
Metaphase
The M phase checkpoint requires _____ and ____ protein kinases, which dissociate from kinetochore when chromosomes are properly attached to the spindle.
CENP-E and BUB
When all ____ kinases dissociate from the kinetochore, the cell is driven through the M checkpoint and anaphase proceeds.
BUB
Amphelic (normal) attachment of kinetochore to microtubules occurs when the kinetochore is attached to ___ microtubule from each centrosome.
one
Merotelic attachment occurs when one/both kinetochores are attached to _____ centrosomes.
both
Syntelic attachment occurs when BOTH kinetochores are attached to the ____ centrosome.
same
Monotelic attachment occurs when only ____ kinetochore is attached to a centrosome.
one
Taxanes and vinca alkaloids is a type of anti-cancer therapy that alter microtubule dynamics and produces unattached _______, causing long-term mitotic arrest.
kinetochores
Exit from G0 phase to enter mitosis and cell division is highly regulated, requiring ________ and ________ signalling cascades.
growth factors; intracellular
Some growth factors include _____ growth factor (EGF) and ______ growth factor (PDGF), which bind to and activate receptors.
epidermal; platelet-derived
Tyrosine phosphorylation on the RTK provide docking sites for ______ proteins which leads to protein-protein interactions.
adaptor
The transcription factor _____ plays a key role in the entry of quiescent cells into the cell cycle by stimulating the expression of cell cycle genes, and it peaks when _____ are present.
c-Myc; growth factors
Mitogenic growth factors bind to the transmembrane receptor _____. this leads to receptor activation by cross-________, activating ____ proteins.
RTK (Tyrosine Kinases); phosphorylation; adaptor
Anti-HER2 antibody (Herceptin) is a drug which targets the early stage of cellular signalling, by blocking the _______. (implicated in many breast cancers)
HER2 Receptor Tyrosine Kinase
Mitogenic growth factor pathway to stimulate mitosis:
_____ (ligand) binds to ______ (receptor), causing receptor to be cross-phosphorylated and activated. Adaptor protein ____ then binds to receptor and gets activated, associating itself with ____ (exchange factor), which can activate ____ (G protein).
Growth factors bind to RTK, causing receptor to be cross-phosphorylated and activated. Adaptor protein Grb2 then binds to receptor and gets activated, associating itself with SoS, which can activate Ras protein.
Ras protein must be bound to the ________ (organelle) to be activated. Many anti-cancer therapies are targeted at preventing Ras binding to _____.
plasma membrane
Ras is a _ protein. It is activated when bound to ____ and inactivated when bound to ____. It contains an internal _____ (enzyme) to hydrolyse the molecules.
GTP; GDP; GTPase
Internal GTPase of Ras might be a very slow process, hence the cell makes use of _____ proteins to promote the hydrolysis.
GTPase activating proteins (GAPs)
Ras mutations:
Mutation of glycine to _____ can result in steric hinderance preventing ____ binding.
valine; GAP
Ras mutations:
Mutation of ______ to leucine, which inhibits the GTPase activity and thus GTP hydrolysis.
glutamine-61
For growth-factor activated Ras transduction, the ____ cascade is used.
ERK (Extracellular signal-regulated kinase) cascade
Kinases specific to the ERK cascade (hence activated by Ras protein):
Kinase 1 - _____
Kinase 2 - _____
Kinase 3 - _____
Kinase 1 - Raf
Kinase 2 - MEK
Kinase 3 - ERK
The activated ___ protein may result in changes in gene expression of the ___ gene, resulting in cell proliferation.
ERK; Myc
The cyclin-Cdk complex (known as MPF) involved in the M phase is:
Mitotic cyclins A and B and Cdk1
To form active MPF,
- Cyclin A and B must activate Cdk_ to form (inactive/active) MPF.
- Requires activating phosphorylation by ___________.
- Removal of inactivating phosphorylation ____ by phosphatase Cdc25.
To form active MPF,
- Cyclin A and B must activate Cdk1 to form INACTIVE MPF.
- Requires activating phosphorylation by Cdk-activating kinase (CAK)
- Removal of inactivating phosphorylation (Wee1) by phosphatase Cdc25.
Phosphatase Cdc25 (which removes inactivating phosphorylation for MPF) is itself activated by phosphorylation by ____. (This is known as positive feedback.)
MPF
Cyclins activate Cdks and also alter _____.
substrate specificity
Cyclin D activates Cdk _ and _ to stimulate the synthesis of cyclin _.
Cyclin D activates Cdk 4 and 6 to stimulate the synthesis of cyclin E.
Rb gene is a _________ gene, and pRb is active in the (phosphorylated/unphosphorylated) state during G0, binding the inactive transcription factor ___, so that the target geen cannot be upregulated. (brake in the cell cycle)
tumor suppressor; unphosphorylated; E2F transcription factor
In proliferating cells, Cdk4/6-cyclinD / Cdk2-cyclinE (Start kinases) phosphorylates pRb and (activate/inactivate) it, (releasing/binding) E2F, allowing for the upregulation of target genes.
inactivate; releasing
______ act on active Cdk-cyclin complexes to inactivate them.
There are two families of inhibitors: ____ and ____.
CDK Inhibitors (CKI)
INK and KIP
INK family of CKIs are expressed during the __ phase of the cell cycle, act by competing for cyclin binding sites on Cdk____. This essentially displaces Cyclin D from the complex.
G1; Cdk4/6
CIP/KIP family of CKIs are expressed during the __ phase, and act by binding to the Cdk-cyclin complexes to inactivate the complex.
S
Cell-ECM adhesion will (increase/decrease) the chance of the cell entering S phase.
increase
(This is because cells require binding to the ECM to be fully competent to responding to soluble growth factors. This is known as ANCHORAGE DEPENDENCE.)
_____ (receptors) are heterodimer complexes of a and B subunits. They are the most important ECM receptors.
Integrins
Integrins recognise short specific peptide sequences.
E.g.: Fibronectin (glycoprotein) receptor binds the ____ motif.
RGD (arg-gly-asp)
Most integrins are linked via ____-binding proteins to the ____ cytoskeleton.
actin
Exception: a6B4 integrin complex is found in epithelial hemidesmosomes linked to the intermediate filament network instead.
Integrins cluster to form ________ involved in signal transduction.
focal adhesions
(Outside-in/Inside-out) signalling involves signal transduction using ECM receptors. Cells may receive information about its surroundings via its adhesion to the ECM.
Outside-in
(Outside-in/Inside-out) signalling involves signal generated inside the cell as the result of receptor-ligand binding can act on integrin complexes to alter their affinity for ECM binding.
Inside-out
The _____ (type/part) of the ECM is the most ideal for cellular differentiation.
Basal lamina/basement membrane
Both sets of signals - ________ dependence and _______ dependence must be present before the cell undergoes division.
There is cross-talk between the ECM and the growth factor signalling.
density (GFs) and anchorage (ECM) dependence
Long-term cell-cell contacts involve forming _______ between cells. These are specific to some cell types such as ______.
cell junctions; epithelial and endothelial cells
Cell-cell junctions are usually arrange either as _________ (zonula) or ________ (macula).
zonula - continuous belts
macula - discrete spots
The presence of cell-cell junctions (inhibits/activates) cell proliferation and division.
inhibits
Cell-cell junctions are affected by ___ (ion) concentration.
At high ___ (ion) concentration, cell-cell junctions are stable and there is (high/low) cell proliferation.
Ca2+; low
Cell-cell junctions are also affected by the presence of adhesion-blocking antibodies.
_____ junctions are cell-cell junctions which have cytoplasmic links to the actin cytoskeleton.
There are a few components:
E-cadherin; B-catenin and a-catenin.
Adherens
______ is an important junction-associated molecule which is regulated primarily by the Wnt signalling pathway.
B-catenin
The APC gene product (tumor suppressor) is a protein involved in the degradation of the ______.
B-catenin
Loss of APC function results in the accumulation of ______, which translocates into the nucleus and activates the ______ transcription factor complex, upregulating a large number of cell cycle control genes.
B-catenin; Tcf/Lef-1
Most human cancers are _______ (epithelial origins).
carcinomas
__ checkpoint checks for the presence of growth factors, DNA damage, cell size, sufficient nutrients.
G1
__ checkpoint checks if DNA is successfully replicated without damage.
G2
__ checkpoint that occurs at ____ checks if there is successful formation of spindle fibres and attachment of spindle fibres to the chromosome kinetochores. (BUB proteins)
M; metaphase
_______ genes code for essential proteins involved in the maintenance of cell growth, division and differentiation.
Proto-oncogenes
__________ mutation convert proto-oncogenes to oncogenes.
Gain-of-function
Oncogenes act in a _______ manner.
dominant
Philadelphia chromosome involves a chromosomal translocation between chromosomes __ and __.
This produces a fusion protein ______, which causes RTK to be continually turned on.
Commonly found in ____ (Cancer).
9 (ABL) and 22 (BCR); BCR-ABL1; CML
________ genes typically encode proteins regulating cellular proliferation and maintaining cell integrity.
Tumor suppressor
Tumor suppressor genes usually act in a ________ manner.
Exception: ____ protein
recessive; p53
_______ mutations occur in tumor suppressor genes, causing it to lose its original function
loss-of-function
Retinoblastoma is the malignant cancer of developing retinal cells due to mutation of both copies of ____________.
RB1 tumor suppressor gene
encodes a nuclear protein that is involved in the regulation of the cell cycle
p53 protein is usually kept in check by ____, which inhibits the activity of p53 via negative feedback.
(p53 transcriptionally upregulates this protein.)
MDM2
The ___ gene is an important tumor suppressor gene implicated in colorectal carcinoma.
APC
APC participates in the ___ signalling pathway, helping to regulate the activity of ______, thereby preventing uncontrolled growth.
WNT; B-catenin
(recall: gene product of APC will degrade B-catenin in the cytoplasm, preventing it from forming Tcf/Lef-1 complex which will upregulate transcription of cell cycle genes.)
In colorectal cancer, at least three ________ genes and one ______ gene must be mutated for an epithelial cell to become metastatic.
3 tumor suppressor genes and 1 proto-oncogene
- APC gene
- K-ras gene
- DCC gene
- p53 gene
Mutations may be inherited for (tumor suppressor/onco) genes.
tumor suppressor
