Midterm 3 Flashcards
p53 is a ________
tumor suppressor
transcription factor
no cancer cell has an in tact p53 pathway
how is p53 induced?
stress signals such as hyperproliferative signals, dna damage, telomere shortening, and hypoxia induce stable, active p53 to induce cell-cycle arrest, senescence, and apoptosis
roles of p53
tumor supressor
prevents proliferation of damaged cells by enforcing cell cycle checkpoints
if DNA damage is detected it initiates the DNA repair pathway
if damage/stress is prolonged or severe it promotes programmed cell death (apoptosis)
p53 turns on gene that destroys itself, why?
so that in the absence of stress signals it is not present and doing its thing
mdm2
ubiquitin ligase protein product of gene that ubiquitilizes p53
what do stress signals do to keep p53 on?
they activate stress kinases that phosphorylate p53 which makes it so that mdm2 can’t ubiquitlate it
cells that are p53 null and experience DNA damage _____
survive. this is bad because you want to see them get killed so they do not spread their damage
In 50% of all human tumors, p53 is lost. What does this result in?
why are these cancers resistant to chemo?
There is no way to prevent damaged cells from proliferating because cell cycle arrest and apoptosis are p53 dependent
these cancers are resistant to chemotherapy and radiation because they are unable to stop replicating
in unstressed (wild type) cells p53 protein is maintained at _______
very low levels. won’t come up on a western blot
in stressed cells p53 protein _______
accumulates. stress kinases phosphorylate p53 which interferes with p53 binding to mdm2. it sends p53 into nucleus where it acts as a transcription factor and suppresses tumor
how does phosphorylating p53 prevent mdm2 from ubiquitylating it?
alters the 3D shape of the mdm2 binding domain so that mdm2 can’t promote its degradation
HCT 116
human colon cancer cell line. p53wt, mutant ras, and mutant B catenin
CPT
camptothecin inhibits DNA topoisomerase, induces DNA breaks, triggers apoptosis. It is plant-derived, and a common chemotherapeutic
it is the stressor in the western blot on the slides
alpha-Am
peptide toxin produced by mushrooms, it inhibits RNA polymerase which triggers p53 mediated apoptosis
in western blot it served as proof that p53 was phosphorylated in response to stress
p21
broadest cdk inhibitor – it can arrest progression of the cell cycle no matter where we are in the cell cycle
first thing p53 does
trans-activates p21, triggering cell cycle arrest
p53 and mdm2 have ________ ________ interactions
mutually inhibitory;
when stress no longer exists there needs to be at least a little bit of mdm2 to degrade p53 when it should no longer be stabilized (basically as one increases the other decreases)
most tp53 mutations are _________
missense mutations clustered in the DNA-binding domain
why are mutations in the DNA binding domain bad for p53 function?
since p53 cannot bind to the DNA effectively it cannot promote the expression of genes required for cell cycle withdrawal, DNA repair, or programmed cell death
what does it take to have a p53 mutant phenotype?
mutation in just one allele
p53 mutations are ________
dominant negative or interfering alleles
why are p53 mutations often dominant?
the odds that a tetramer contains on mutant subunit is extremely high. In a heterozygote only 1/16 of tetramers will have only wild type
Outcome when:
1) two normal p53 genes
2) homozygous recessive mutation
3) Heterozygous recessive mutation
4) Dominant negative mutation
1) both copies produce normal p53 protein chains that form the final protein
2) no p53 protein chains are produced
3) the normal copy produces normal protein chains that form a functional p53 protein
4) mutant gene produces abnormal protein chain that may assemble with normal p53 chains in a way that prevents a functional p53 chain from coming out
when you have overactive ras you also need ______ to form foci (bacterial cell transformation)
mutant p53
because you can’t just have an active oncogene to have its effect you need a defective tumor suppressor
Why do you need a mutant p53 (or more broadly tumor suppressor) to have successful oncogenic expression?
In wt cells oncogenic signaling up-regulates the transcription factor E2F which induces ARF.
ARF interferes with mdm2 so it leads to the stabilization of p53 and either arrest or apoptosis occurs
What is ARF induced by and what does it do?
induced by E2F and it interferes with mdm2 (sequesters it to the nucleolus) to stabilize p53 to cause arrest or apoptosis in defective cells
What does ARF stand for?
alternate reading frame
product of p16 gene which is a CDK inhibitor via an alternate reading frame
_____ and _____ tumor supressor proteins are produced by one gene because of _________
p16 & ARF
an alternate reading frame
p16
cdk inhibitor that prevents phosphorylation of Rb (which would not be able to restrain passage through the cell cycle)
how does oncogenic signaling promote p53 stabilization/cell cycle arrest/apoptosis? (pathway)
oncogenic signalling (c-myc ras or e1a) induces e2d which induces arf which stabilizes p53 which promotes oncogene induced apoptosis
when do tumors develop?
after a lag when ARF (or p53) is lost
arf ______ develop tumors much faster than _______
heterozygotes; homozygous wt
oncogenic pathways want to _______
stabilize mdm2
so that it will destroy p53
tumor suppressor pathways want to _________
stabilize p53
it wants to inhibit mdm2 from destroying p53
stress signals want to _________
stabilize p53
oncogenic signals want to _________
promote the interaction between p53 and mdm2
anything that antagonizes p53 promotes _______
survival! NOT proliferation (which is going through the cell cycle)
anoikis
epithelial cells that lose their attachment to the ECM undergo apoptosis
laddering
nuclease is activated and cuts genomic DNA at the linker region between nucleosomes, producing a ladder of fragments
happens during apoptosis (so do blebs)
found using FACS
FACS
treat cells with fluorescent dye that shows you amount of DNA per cell
shows you which are apoptotic because you will see that they have smaller pieces of DNA that will leak . The greater % of cells with sub G1 content of DNA the more apoptotic
apoptosis & phospholipid bilayer
membrane has negative charge on inside of cell (phosphotidyl serine)
when apoptosis happens the membrane breaks up and these negative charges will be on outside. the green flourescent dye hits this and lights up
just green early apop
green and red on mem end
cytochrome c
in intermembrane space huge death effector that activates hydrolytic enzymes
how is cyt c let out of the mitochondria?
the opening and closing of pores. they can oligermize
anti apoptotic keep the pores closed
pro keep them open
Bcl2 proteins
some antagonize p53. some are pro apoptotic. all have similar structure but can antagonize one another
not a classic oncogene but has oncogenic activities. it is a survival protein.
bcl2 and bclxl are ______
anti apop
bax and bak
pro apop
makes the pores want to open
bad, bim, bid and puma and noxa
pro apop bh3 only
_____ proteins are the crucial link between the apoptotic stimuli and mitochondrial cytochrome C release
BH3
they distract the anti apoptotic proteins by binding them. this allows the other pro apop (bax and bak) but not BH3 only ones to open the pores
______ and _____ open the pores to let cyt c out
bax and bak
caspases
they have a cysteine in their active site and cleave target proteins at aspartic acid
what cascade is in charge of the apoptosis program
caspase. they hydrolyze the cell in a controlled and irreversible fashion
describe flow of caspase cascade in apop
initiator caspase cleave and activate executioner caspases which cleave key proteins
the first initiator caspase step is the one most closely regulated. all have to be cleaved to become active
how is the initiator caspase activated?
cyt c! has to come out of mitochondria and form a complex with apaf1 = the apoptosome. this promotes apop by activating the first initiator caspase
apoptosome
apaf1 + cyt c
bcl2 apop mech
bh3 only bcl proteins distract the anti apop bcl proteins allowing for bax and bak to open the pore to let cyt c out into the cytosol. this binds with apaf 1 and forms a complex to become the apoptosome. this activates the initiator caspase
IAPs
inhibitors of apop inhibit caspases and some polyubiquinate them
T or F: any cell that sustains a mutation in one p53 allele becomes p53 inactive
T
what does E6 viral protein do?
expressed by hpv it binds to p53 and promotes its degradation
ways to inactivate p53
degradation sequestration deregulation of mdm2 deregulated "survival signaling" loss of stress kinases
sequestration
move the p53 to the cytoplasm/mess with its protein conformation so that it wont be let into the nucleus
cytoplasmic p53 is usually ______
wt
its just trapped where it cant do anything
nuclear p53 is usually ______
mutant
if you give a stressor like chemo it can kill cancer cells
why does deregulation of mdm2 inactivate p53?
it destroys p53
how does deregulated survival signaling inactivate p53?
messing with a piece of a pathway that impacts p53 in turn messes with p53
ex. if you delete PTEN, which down regulates the AKT pathway, you see an increase in AKT activity which increases mdm2 which impairs p53.
why would the loss of stress kinases impact the activity of p53?
p53 would not be active when there is a stress because mdm2 would be able to constantly degrade
ex no big brother to protect
mortal v immortal for cells
mortal = fixed number of growth cycles then they permanently stop dividing
immortal = infinite number of growth division cycle to acquire the successive genetic changes necessary for tumorigenesis
explain replicative potential at different stages of cell development
early in embryogenesis cells have unlimited replicative potential
when they commit to a cell lineage they get a pre-determined replicative potential
as organisms age their cells lose ____________
proliferative capacity
why is it that as organisms age their cells lose proliferative capacity?
it is a defense against cancer to ensure that a potentially neoplastic cell does not have enough replicative potential left to cause serious harm
Hayflick limit
he looked at cells from tissues from babies, adults, elderly and saw how long they would grow in the lab
what intuitively would be thought to happen happened
post serial passaging cells know when to stop dividing
primary cells vs cell lines
primary: direct from tissue
cell lines: meant to grow in lab. immortal but not normal cells because we selected for cells that grow regardless of stress
serial passaging
sub-confluent
reharvest cells and put them on fresh plate so that they aren’t contact inhibited
senescence
permanent non-dividing state
not even with a mitogen
what triggers senescence?
DNA damage, oxidative stress, chemotherapy, oncogenes
why is senescence good?
if you’ve been dividing for 60 years and so many fuck ups have happened its probably good that you dont replicate and pass on your shit
senescent cells still express __________ and need _____ to survive
growth factor receptors
growth factors
they just no longer proliferate in response to mitogenic signaling
Overexpression of CDKIs promote _________
CDKS _______ it
senescence
block
Stresses ______ CDKIs
upregulate
Explain how CDKIs promote senescence
stresses upregulate p16/p21 (CDKIs) which promote senescence
Levels of CDKIs _______ over time (aging)
increase
How do culture conditions of cells in the lab influence the onset of senescence?
epithelial cells grown on plastic see a dramatic increase in the amount of CDKI mRNA produced and stop dividing in comparison to epithelial cells grown on feeder fibroblasts
cells that have escaped/avoided senescence often have _________
overexpressed CDK 4 or inactivating mutations in p16 CDKI
what does the fact that cells that have avoided senescence often have overexpressed CDK4/inactivating mutations in p16 indicate?
senescence requires tumor suppressor activity
to avoid senescence ____ and ____ pathways must be inactivated
p53 and pRb
LT protein
DNA tumor virus protein that inactivates p53 and pRb
if you plate human kidney cells with LT protein, what happens?
cells continue to grow indefinitely
senescence associated beta galactosidase
can stain tissue with it and see how cells become more senescent over time
how does chromatin appear in growing versus senescent cells?
growing: chromatin is dispersed
senescent: chromatin is in discrete foci
SAHF
marker of senescene
stands for senescence associated heterochromatic foci. this requires Rb mediated chromatin remodeling of E2F target genes. Markers include H3K9me and Suv39h1 (histone methyl transferases
phenotype of senescent cells
increase lysosomal sa-B-galactosidase
chromatin structural changes SAHF
senescence associated secretory phenotype (SASP)
production of cytokines chemokines and growth factors
proteases that shed membrane bound receptors cleave or degrade signaling molecules and degrade or alter the ECM
why can senescence be bad for an organism?
when a cell becomes senescent it secretes cytokines chemokines and growth factors that can impact neighboring cells
autocrine and paracrine functions can occur that can be beneficial or detrimental
what autocrine and paracrine functions of a senescent cell are bad?
SASP of senescent cells can cause normal less to lose optimal function —> tissue degradation
SASP can cause premalignant cells to proliferate and adopt more malignant phenotypes, leading to full blown cancer
telomeres
preserve the chromosome ends
tandem hexanucleotides repeats (thousands of them) and associated proteins
- repeats are different in each species thats kinda fun!
structure of telomere
double stranded region of telomeric DNA (5-10 kbp long)
single stranded 3’ overhang of G-rich strand of telomeric DNA (several hundred bases long)
ss loops around into double stranded end. can be targeted in therapeutics
how do we know that telomeres shorten over cell proliferation?
we cut the DNA to be small enough to go into gel and do a southern blot. we see they get shorter as they divide
the end replication problem
telomeres shorten with each S phase
because of the whole okazaki fragment thing where we need the RNA primer to be put down lol so we lose 50-200 bp DNA at each 3 prime end
these aren’t coding regions so they don’t impact our actual genetic passing on in each division
what is the consequence of shortened telomeres?
eroded telomeres result in senescence which translates to aging in real life.
eventually when the telomores get so short and then we run out of telomeres they might do end to end fusion which causes senescence
what happens when telomeres shorten to the point of unprotection?
cell will try to fix this by fusing the ends of the sister chromatids together. BUT THIS IS BAD. because when you try to go through mitosis again the centromeres will split because now you essentially have two causing a second breakage. then a new nonhomologous chromsome can get nice and comfy and try to fuse with the weird crazy chromsome that results.
tldr these crazy weird chromosomes happen from breakage-fusion-bridge repeat cycles
dicentric chromsomes
when you have the fusion of the two ends to fix that the telomeres aren’t there and the centrosome is still in tact
cancer cells escape crisis by expressing ________
telomerase
telomerase
an enzyme which elongates and regenerates telomeres
in normal tissue we have it during early embryogenesis but then it gets silenced
telomerase is elevated in _____ of human cancers
85-90%
you can override senescence/evade crisis by expressing ______
telomerase
if you introduce a dominant negative telomerase (means that it will out-express native telomerase) into cancer cells, what happens?
telomeres start to shorten and they eventually stop dividing
lag time correlates with _____
telomere length
telomerase activity and prognosis in pediatric cancer
better outcome is telomerase activity is negative
converse also true
in pediatric neuroblastoma, myc __________ telomerase
upregulates
myc is a transcription factor
the hTERT promoter has a myc recognition site
DCIS
ductal carcinoma in situ
tldr 15% of these bois become cancer and scientists can’t tell which do. they have initiation but not completion of tumor development
details: larger number of pre malignant cells pass through results in considerable telomere erosion. they don’t upreg telomerase, they seem like they are done (went into senescence
PIN
prostatic intraepithelial neoplasia
this is a precursor to prostatic carcinoma but many of the luminal epithelial cells lining the duct have lost telomeres while underlying basal epithelial cells have strong telomeric DNA signal
shortening telomere length to a crucial length is detected as ______
DNA damage which creates stress response which could be senescence or apoptosis
telomerase subunits
hTERT = human telomerase reverse transcriptase. synthesizes DNA from RNA template. has myc consensus sites that make it a transcriptional target of myc
hTR = human telomerase-associated RNA. RNA template that is required for it to work. Transfected with anti-sense and cells will lose telomeric DNA and begin to die after ~25 divisions
.
Processed in the spliceosome, previously thought to only process pre-mRNAs
how does telomerase work?
replaces telomeres
it extends the end that already has the overhang and then DNA polymerase uses the extended part as a primer to start replicating so we don’t shorten
TRAP assay
measures telomerase activity. telomerase extends the existing hexanucleotide repeat which after pcr amplification gives the ladder of bands
trap = telomeric repeat amplification protocol
if telomerase is present then films/bands would appear
if telomerase isn’t present then they would not
what does seeing hTERT mRNA in a northern blot indicate?
that the telomerase genes are being expressed
senescence requires ____ and ___
p53 & Rb
karotypic chaos
due to breakage fusion bridge
when crazy combo chromosomes occur because of BFB
TERT expression patterns
can be repressed or depressed if there are mutations in the regulatory region for the gene.
in normal cells it is unmethylated which favors repressor binding.
what else besides telomere related things do telomerases do?
took metastatic melanoma cells from mice and downregulated telomerase expression. they stop proliferating and redifferentiate into melanocytes.
gene expression regulation, cell proliferation, apoptosis, wnt/b catenin signaling, nf-kb signaling, oncogenisis (myc driven), cell adhesion, cell migration, angiogenesis, epithelial mesenchumal transition (emt)
promoter and reporter genes
promoters drive expression of reporter genes
how does telomerase modulate WNT signaling?
tldr telomerase helps stabilize b catenin
the promoters for wnt targets such as cyclin D1 and myc drive expression of a reporter gene luciferase.
licl stabilizes b catenin by inhibiting gsk3b tert increases the activity of both promoters
licl means _______
stabilize b catenin
how does telomerase help stabilize b catenin?
by associating with brg1 a chromatin remodeler that is involved in WNT signaling
use CHIP
BRG1 is a chromatin remodeler known to be involved in WNT signaling and known to form a
protein complex with TERT
b catenin tert and brg1 all occupy myc and cyclin D promoters after b catenin is stabilized by licl
CHIP = chromatin immunoprecipitation
see if transcription factors are binding to promoters
which proteins occupy a particular promoter
what did chip analysis show about telomerase
myc and cyclin d have MORE occupation when you have TERT and BRG1 (chromatin remodeling protein)
hallmarks of cancer
1) self sufficiency in growth signals
2) insensitivity to antigrowth signals
3) evasion of apoptosis
4) limitless replicative potential
5) sustained angiogenesis
6) tissue invasion and metastatis
cancer metabolism: how is it a different strategy than our normal?
only 1% of glucose will be oxidated all the way down to ATP.
they basically do non-oxidative phosphorylation to make all of the other shit that is necessary for many cells like amino acids fatty acids etc.
cancer cells express more ____ and _____ in comparison to normal cells
GLUT1 (glucose) and Pk-M2 which diverts pyruvate to LDH rather than PDH to do oxidative phosphorylation
Pk-m2
different pyruvate isoform that allows for all of this stuff to go into non-aerobic metabolism
but back up happens like
traffic where it goes slower
cancer incidence increases as we ___
age
___ increase in lung cancer smokers compared to non smokers
10 fold
relationship between cancer incidence and carcinogen exposure
duration of exposure determines onset, regardless of age. exposure raises rate of tumor progression orders of magnitude above spontaneous rate
histopathology provides evidence of _______
multi step tumor formation
in situ
in place
cancer didn’t cross basal lamina yet and cannot infiltrate underlying tissue, enter bloodstream, or metastasize to distant sites
benign polyps are _______ to ________
precursors; dangerous invasive cancers
wide majority of cancers are result from ____
loss of apc
steps to colon cancer (apc pathway)
Loss of APC–>DNA hypomethylation–>activation of KRas—>loss of p53
how is cancer development like darwinian evolution (clonal succession)
first cell gets a mutation that starts cell toward hyperplasia. then it proliferates maybe more or faster. then another mutation happens etc. these mutations could provide an advantage and be selected for
creates large population
____ + _____ leads to tumor progression
mutations and epigenetic mechanisms
initiation –> promotion –> tumor progression
how do tumor cells complicate the darwinian evolution theory?
not all cells have same proliferative capacity
some tumors can contain small groups of cells that are cancer stem cells
only some eventually time out of division
means that some must revert back to stem cells for it to keep dividing indefinitely
explanation for how a cell could infinitely divide other than darwinian theory?
that differentiated (transit amplifying) cells revert back to stem cells in mutation
OR all mutations are in stem cells only
transit amplifying (progenitor) cell
committed to a particular differentiated state but continue to divide. descendents will be committed
FACS analyses to determine how tumors happen (and determine between theories post darwin)
fluorescence activating cell sorting (sort cells based on fluorescence
intratumor heterogeneity is the mixture of genetically distinct regions in a single tumor
intratumor heterogeneity suggests
not all cells within a tumor are as tumorigenic
how can we tell tumor formation is a multi step process
epidemiology –> population studies
pathology –> we can visualize cells when they are in each of the stages
genetics –> we can see different mutations correspond to different phases
what happens when activated ras gene is expressed in primary cells?
proliferation but not transformation
when we got taught about ras causing tumors in lab before it was because those were in cell lines that already lost their tumor suppressors
transformation usually requires _____
2 or more mutant genes collaborating
ex. focus formation and tumorigenicity required a ras like and a myc like oncogene in rodent cells
what does ras cause?
what does myc cause?
ras: anchorage independence, loss of contact inhibition, morphological changes
myc: immortalization, growth factor independence
mice experiments that show tumorigenicity in myc only ras only and the combo
the combo had tumor phenotype much more apparent much earlier. then loss of ras alone was bad then loss of myc.
LAG OCCURS DUE TO LOSS OF P53
What is the lag in the mice myc, ras, combo experiment caused by?
loss of p53
what are the 5 pathways needed to mess up to have cancer in humans?
ras pRb p53 telomeres PP2A
A. hTERT + SV40 LT
- Rb, p53 inactivation, = immortalization
2. Then Ras can transform them
PP2A
holoenzyme with multiple subunits (C catalytic, A scaffold, B substrate)
removes phosphates that kinase adds
(kinases tend to promote proliferation so these bois normally prevent prolif but if you fuck them up we get cancer)
what is the reason that rodents only need 2 mutations but humans need 5 mutations to get cancer?
because there must have been some evolutionary benefit to tumor suppression that we received because our life span is longer
tumor progression model: initiators and promoters
initiators are mutagens
promoters are non-mutagenic agents = mitogens, cytotoxins, and the inflammatory response
if cells sustain DNA damage but don’t proliferate rapidly, it will take a very long time to get them to be a tumor.
so initiators do the damage BUT promoters give you the conditions to proliferate
evidence for initiator promoter model
in mouse
DMBA is initiator
croton oil is the promoter
if you apply DMBA to mouse skin, you don’t see anything
if you apply croton oil you see irritation but no tumor
if you apply both you see tumors
*must be initiated and promoted in the SAME spot
example of initiator and promoter model in humans
smoking and drinking
both together lead to 100x increase of mouth and throat cancer
smoke = initiator alcohol = promoter it is a toxin which kills epithelial cells and promotes stem cells to regenerate in epithelium (this is for hard liquor
another example of initiator and promoter model in humans
hormones are mitogenic agents and can function as tumor promoters
the periodic stimulation of mammary epithelial cell proliferation under the control of progesterone prolactin and estrogen appears in breast cancer
chronic inflammation creates a _______
chronic proliferative environment
inflammation symptoms
redness
warmth
pain
swelling
because immune system cells charge the affected region in the acute phase
failure to resolve in the acute phase causes chronic inflammation
nf-kb & its pathway
transcription factor that is sequestered in the cytoplasm by its inhibitor (ikb).
Signaling promotes phosphorylation and degradation of the inhibitor which allows it to travel to the nucleus and transcribe target genes (similar to b catenin)
ikk is the kinase that phosphorylates the inhibitor (stimulated by all the immune factors like tnf-alpha il1beta lps ros)
targets of this pathway are anti apoptotic and pro proliferative
rarely mutated but often constitutively activated in cancer cells
-because it is more about sequestration than anything else
_____ is a key mediator of the inflammatory response
tnf-alpha
was one of the responses to irritants in the mouse example where we painted on the skin
people who took aspirin had ___________
reduced risk of cancer
animal model chronic inflammation example
mdr = multiple drug resistance pump, if upregulated cells become resistant to chemo, cells collect bile acids, and chronically inflame.
mdr pump is essential to protecting the hepatocytes from the bile acide
Mdr -/- is a mouse animal model with chronic liver inflammation, leading to hepatic dysplasia and HCC
-immune cells that infiltrate release tnfalpha and other hepatocytes are activated by paracrine actions –> nfkb pathway
mdr pump _____ hepatocytes from ______
protects; bile acids and chronic inflammation
in presence of ______ loss of nfkb signaling results in _______ of pre-neoplastic hepatocytes
inhibitors
apoptosis
what does the idea that in the presence of inhibitors loss of nfkb signaling resulting in apoptosis of pre-neoplastic hepatocytes indicate for inflammation’s role in cancer?
that tumor-promoting activity of inflammation is the suppression of apoptosis
chronic inflammation: _____ is always on/secreted which induces ___ pathway
tnf-alpha; nfkb
how do anti inflammatories work?
NSAIDs (non-steroidal anti inflammatories)
inhibit cox-2 by acetylating serine residue within enzymes catalytic cleft
cox2 is a transcriptional target of nf-kb
cox2
responsible for synthesizing prostaglandins
prostaglandins are lipids that are used in autocrine and paracrine mediators. signaling molecules
we will focus on PGE2
PGE2
key mediator of inflammation
cox 2 converts arachidonic acid into pge2
animals support a correlation between pge2 levels and cancerous lesions
associated with cancer phenotype (increased prolif but also all the things with ras activation)
- loss of ecadherin
- anchorage independent prolif
- loss of contact inhib
if you inhibit the cox enzyme
no inflamm response because no pge2 because no nfkb.
in presence of cox inhibitor you see increased apoptosis and decrease proliferation
cox2 is a ______ of nfkb pathway
transcriptional target
nfkb antagonizes ___ & ____
p53 and Rb
p53 by inhibiting apop
Rb by promoting things like cyclin D which will inactivate Rb
nfkb pathway produces:
tnf alpha
cyclin d1 (myc for prolif)
bclx (protection from apop)
tumor promotion is likely to be a determinant of ______
the rate of tumor progression (how fast we go from mutated weirdness to full send cancer)
all tumor promotes can enable clonal expansion and subsequent additional mutations
repeated cell division allows for replication errors
repeated prolif leads to telomere erosion (BFB)
inflamm cells such as macrophages and neutrophils deploy ROS and RNS which can function as mutagens
t or f: obesity is associated with increased cancer
yeah! true
expanding adipose tissue is ________
dysfunctional. it starts to secrete signalling molecules that normal wouldn’t. they secrete chemo-attractants that increase inflammation
obesity mimics ________
low grade inflammation
hypoxia within adipose tissues activates ______
hif 1 alpha which also increases macrophage infiltration ecm remodeling and angiogenesis
obesity is associated with _______
insulin resistance
which is also associated with pro-proliferative stuff
what are upregulated in obesity and what is it associated with?
associated with pro prolif and anti apop
leptin - regulates appetite and metabolism (resistance associated with obesity) MAPK and PI3K
PAI-1 - serine protease inhib
TNF a and IL6- pro inflam
what is downreg in obesity and what does it do?
adiponectin
anti-inflamm
insulin sensitizing
decreases ROS (which activates mapk)
inhibits angiongenesis by promoting apop
colon tumor progression
The loss of Apc gene is the first thing that happens, always
■ LOH 5q
■ The epithelial cells become hyperplastic because the B-catenin pathwayis always on
DNA hypomethylation means the genes that should be silenced by hypermethylation of their promoter regions might not be silenced
■ Also, the integrity of centromeres (heterochromatic; the genome is highly methylated and condensed in that area) is affected
● Mitosis can’t happen properly
Mutation of codon 12 in ras occurs ■ Intermediate adenomas form (pre-cancerous growths or polyps) ■ Three pathways of ras are activated ● MAPK ○ Cyclin D and phosphorylation of Rb, no R checkpoint ● PI3K ○ Anti-apoptotic signaling ● Ral-GEF ○ Cells become more invasive and mobile
LOH 18Q
AKA TSG (tumor suppressing gene) or DCC (deleted in colon cancer)
● Deletion contained a few different genes and scientists weren’t sure which gene loss led to cancer
■ Now, evidence points to Smad4
● This is a gene that’s part of a pathway that begins with the membrane receptor for TGF-B (anti-mitogen)
○ Normally Smads are sequestered in the cytoplasm, TGF-B signaling allows them into the nucleus
○ They are TFs that turn on CDKI genes for p21, p16 etc
p53 is the last loss before full-on carcinoma
■ Associated with LOH 17p
■ You lose the ability to perform apoptosis in the presence of stress, like
hypoxia, contact inhibition, anoikis, etc.
■ Once you lose p53, there’s nothing you can do to stop progression to
cancer
