chapter 20: cancer part 2 Flashcards
miRNA’s can act as both
proto-oncogenes or TSG
what is a miRNA that functions as TSG
miRNA Let-7: degrades RAS gene
when a cell is working properly, too much ______ is made, functional miRNA scales it back to appropriate levels
RAS
what could happen if there was a mutation with the miRNA Let-2
will amplify too much RAS, lead to an overactivity of adenylyl cyclase, and lose control of signal transduction
*activate too many proteins that move the cell cycle forward
describe the purpose of qRT-PCR
tell how many copies of a specific mRNA are being produced in a cell. ex. how much RAS is made with DNA.
describe the qRT-PCR process:
-take healthy cells and healthy cells with HeLA: immortal, telomerase, always copy
-open them and utilize mRNA
-RT step: change mRNA to DNA. use TTTT primer to match poly A tail. dNTPS: GATCS make DNA RNA hybrid, RNA self nicks and has OH groups that allow the strand to be synthesized
-set up PCR: determines how much RAS is made, amplify RAS only. denature, anneal, extent
-PCR doubles the amount every time.
describe the confounding variable in the qRT PCR reaction and what is executed.
-confounding variable: what if more cells were opened in the HeLA cell
-internal control: GAPDH; “on” at the same level in a cells gene.
-results: HeLA had 6 times less GAPDH than healthy cells. for every 6 cells opened, only one opened in there is not 4x more than RAS there is 24x more RAS.
miRNA 373/372 acts as a
proto-oncogene to oncogene
what are the normal conditions of a cell with p53 and LATS
healthy balance of p53 made as LATS ties up and inhibits action of p53 repressor.
LATS function
prevents p53 repressor from working
p53 repressor function
stops p53 from being made
describe miRNA 373/372 and what happens if it is too active
made in the nucleus, drosha, dicer, argo, RISC: chews up LATS
-if it is too active: chews up too much LATS mRNA, little LAT protein, no tie up of LAT with p53 repressor, binds silencer, downgrades p53.
small numbers of p53 cause (miRNA 373/372):
can’t act as an activator for WAF-1, no p21, CDK remain active, move the cell cycle forward
-premiscous DNA polymerase is turned on
-no BATS: no apoptosis, more likely to have cancer
mutator genes: TSG
-includes DNA repair systems
-proto oncs need to become oncogenic, loses ability to regulate
virus associated cancer
17 % of cancer
virus use
SS RNA
-RNA on + is recognized
- (-) needs to be converted
RNA tumor viruses
carry their own genes disrupt
-have retroviruses: take its RNA and convert to DNA
-can be cut and inserted infront of proto oncs Src or RAS
-or interrupt TSG
how many genes do viruses have
12
briefly describe tumor virsuses
-carry viral oncogenes of their own
-rarely integrate into host genome
-its a v-onc a viral gene that messes with a cells regulatory proteins.
what are the eukaryotic virus components? HIV
-phospolipid bilayer around virus particle
-protein capsid
-RNA inside capsid: has genes for virus proteins
-gp120: protein that sticks out on envelope of the virus. protein spike in hydrophobic region.
-gp41: protein on virus, comes with gp120
-integrase: enzyme transports
-reverse transcriptase: enzyme, reverts RNA to DNA
what do gp120 and gp41 bind with?
bind to CD4 protein on t-helper cells
what is on the surface of t helper cells?
CDK-4: on the surface of t helper cells, binding site #1
CCR-5: chemokine coreceptor-5, binding site #2
when the protein spikes of a virus binds to a t- cell the membranes…
fuse together
describe what happens after fusion during a lytic cycle with HIV
-viral capsid released into the cell
-capsid quickly breaks down and releases RNA (2 copies)
-preformed reverse transcriptase enzyme is released from capsid. performs DNA synthesis
-RNA to double stranded DNA
-very error prone, no proofreading
-since it is produced in large numbers, it can afford to mutate, natural selection support good viruses.
-mutated viruses = a lot of variety which leads to many small changes in proteins, antibodies made for the first infection may not be useful.
-integrase enzyme places DNA into random place in the gene
-since viruses are small, chromosomes dont recognize
-cells are tricked to make genes of the virus
-RVT, integrase, gp120 and 41 self-assemble due to chemistry. the virus spreads
discuss when the HIV virus leaves the cell; lytic cycle
-gp120 and 41 begin to assemble on the surface of the cell
-capsid protein starts to form with a copy of the RNA virus.
-buds off: 1 in 200 out
-steals too much membrane of the t helper cell+ leads to death
all retroviruses code for
RVT and integrase
retroviruses need to undergo a _____ phase to cause cancer
latent
HIV can undergo both
lytic and latent phases
lytic kills the
host cell, too much membrane is taken off from the virus
desribe latent phase with HIV
-cells are not killed they remain a provirus, not actively transcribed with their own regulatory proteins
- t cells remain active and reproduce with virus particles in chromosome. this allows more host cells
-maintain a population of viruses and hosts in a system
-after 4 years, new virus particles land in new genes which wipes enough genes out to lose cell cycle function and develop blood based cancer- leukemia: WBC
if a viral promotor or genes are disrupted it causes an increased risk of (latent phase)
cell cycle issues
an RNA based virus can only package……
their own genes
-cannot handle extra genes properly
-if they steal a gene from our genome they need to remove some of their own genes
discuss DNA based virus (HPV)
-starts as a envelope virus and fuses membranes
-has a capsid protein which breaks down once inside the host cell
-DNA stays outside of genome, still copied: genes are for affecting the cell cycle and have structural proteins.
-make E6 and E7. DNA is replicated, transcribed and translated
-if a cell is stressed it will want to turn on p53
-E6: binds to p53 which progresses the cell cycle, does not allow it to undergo apoptosis
-E7 binds to pRB, pRB can no longer bind to E2F
-if E2 is free: activator for helicase, ligase, polymerase
-move from S phase back and forth and is unregulated.
stress causes a cell to go from latent to
lytic
viral RNA transcribed with chromosome- RAS gene
-when there is a viral component in the genome sometimes part of the chromosome gets transcribed with RNA
-the virus produces a lot more RAS which increases RAS in the cell
-if the virus has 100% of viral genome on RNA and some of RAS, the virus cannot properly package that in a capsid.
-it will lose 20 % viral and gain 20 % RAS
-package into capsid, make a virus, then infect. the cell has RAS from mom, dad, the virus. and extra 30 % from the genome.
-transforming virus: brings extra proto on to the cell but not a replicating enitity.
what are the types of treatment available for cancer?
traditional, targeted, immunotherapy
traditional treatment methods
chemotherapy and radiation therapy
chemotherapy
-includes chemical therapy
-base analogs and base modifying agents (fake bases) are diluted into the body at a high dose
-healthy cells: take time to fix with base excision repair
-cancer cells: dont fix, mutations accumulate, broken proteins accumulate= cell death
radiation healthy cell vs cancer cell
healthy cell:
-hit with large amount of radiation: makes dimers
-p53 is used= pause, meaning that WAF-1 is transcribed, p21 protein is made, binds to CDK with Cyclin.
-cell does not continue to S phase, has time to detect and fix mutations using nucleotide excision repair; UvR system
-new DNA is put down okay
-patient does not feel healthy because cells dont function well.
cancer cell:
-hit with radiation
-no pause, moves to S phase, less DNA is fixed
-during replication, more errors are made ex. mismatch and frameshift
-more errors=broken proteins
-survival of the cell decreases
what type of cells does targeted therapy deliver? what does it use?
-instead of delivering to healthy cells, mainly delivers to cancer
-uses an antibody that is conjugated to a base modifying agent or low level radioactive materal
targeted therapy constructs antibodies for TAAs and TSAs
-TAA: tumor-associated antigens, cancer cells overexpress proteins that attract small blood vessels to them. leads to massive amount of blood flow to account for high growth in the tissues. associated with angiogenisis: triggers blood vessel development in the cell.
-TSA: tumor specific anitgens; cancer cells express surface proteins that healthy cells dont. due to fetal dev. growth genes.
use of the drug preceptin
-some breast cancers grow too fast because the cells are expressing more estreogen receptor which causes too much estrogen in the blood stream, or progesterone receptors, or Src
-candidate for targeted therapy
triple negative breast cancer
lack estrogen, progesterone and Src receptors
- cant use targeted therapy
macrophages are involved in
the blood system, travels easily
MHC-1
interacts with cytotoxic t cells through CD8. all cells produce an MHC-1
what is the function of cytotoxic t cells
active when they have the correct receptor for the MHC-1 that presents the TSA
-roams in the body in search for protein (TSA)
-if a cell has a MHC-1 that presents TSA on its surface, cytotoxic t cells interact and release toxins, killing the cell and some around it
MHC-II
interacts with helper t cells through CD4
helper t cell:
has a diverse receptor, less than 1 percent are activated in reactions.
-once activated, releases cytokines hormones
cytokines:
trigger inflammation or stimulate b cells
b cells need to receive what type of signals to replicate?
- b cells receive a cytokine signal and a signal from its antibody
which type of antigens do b cells stick to
stick to TSA’s, TAAs are already present in the bone marrow
describe what happens to b cells once they replicate
some stay as b cells with anitbody on its surface in the lymph nodes (memory B cells): ready to encounter the virus again
-some become plasma cells: release antibodies, coat anc overwhelm infection material, can come from B cells or memory B cells
when do natural killer cells come into play?
if there are two or more antibodies bound on the cancer cell with TSA’s
-releases toxics and kills
PDL-1
cancer cell turns on, and t cell interacts with and has PD-1 on the surface
-cancer cell will send a signal to stop fighting
keytruda and octevo:
antibody that bind to PD-1 on the t cell, block PDL-1 from binding, cause t cell to stay active longer
Yervoy anitbody
-blocks B7 (on tumor cell) from shutting off t cell with CTLA-4
CAR-T:
includes generating a cell line and inserting it back into the body to fight a specific tumor
-uses WBC
