Transcript Slide 1

Cytokines
• Cytokines are small secreted proteins which
mediate and regulate immunity, inflammation,
and hematopoiesis.
• They generally (although not always) act
over short distances and short time spans
and at very low concentration.
• They act by binding to specific membrane
receptors, which then signal the cell via
second messengers, often tyrosine kinases,
to alter its behavior (gene expression).
• Responses to cytokines include increasing or
decreasing expression of membrane proteins
(including cytokine receptors), proliferation,
and secretion of effector molecules.
• Cytokines may act on the cells that secrete
them (autocrine action), on nearby cells
(paracrine action), or in some instances on
distant cells (endocrine action).
Cytokine Activities
• Cytokines are made by many cell populations, but the
predominant producers are helper T cells (Th) and
macrophages.
• The largest group of cytokines stimulates immune cell
proliferation and differentiation.
• This group includes
– Interleukin 1 (IL-1), which activates T cells;
– IL-2, which stimulates proliferation of antigen-activated T and B
cells;
– IL-4, IL-5, and IL-6, which stimulate proliferation and
differentiation of B cells;
– Interferon gamma (IFNg), which activates macrophages;
Q. What effect would a defect in the gene
that makes the gamma chain have?
Hypersensitivity
There are four different types of hypersensitivities that
result from different responses of the immune system:
• There are 3 types of immediate hypersensitivities that depend on the
interaction of antigens with antibodies : Type I, Type II, and Type
III.
• Type I (IgE-mediated or anaphylactic-type)
• Mechanism: This is the most common type of hypersensitivity, seen
in about 20% of the population. IgE is made in response to an
allergen .
• In allergic individuals, the levels of IgE may be thousands of times
higher than in those without allergies.
• Possibly this is due to a higher number of Th2 cells which produce
IL-4, a cytokine that can increase production of IgE, and a lower
number of Th1 cells that produce gamma-interferon, a cytokine that
decreases IgE production.
The Fc portion of IgE binds to the surface of mast cells and basophils
When the allergen cross-links the Fab portions of the mast cell-bound IgE, this
triggers histamine release by the mast cell, a process called degranulation, and the
synthesis of other inflammatory mediators such, leukotrienes, prostaglandins,
and cytokines that contribute to inflammation (these act as chemoattractants).
These agents cause the early phase of allergic reactions that appears within
minutes after exposure to the antigen.
Type I hypersensitivity is treated symptomatically with
such agents as:
• a. epinephrine. Epinephrine relaxes smooth
muscle, constricts blood vessels, and stimulates the
heart. It is used for severe systemic reactions.
• b. antihistamines . Antihistamines block the binding
of histamine to histamine receptors on target cells.
• Severity may be reduced by desensitization shots
(allergy shots). It is thought that when very dilute
allergen is given by injection, it stimulates the
production of IgG
• IgG then act as blocking antibodies to bind and
neutralize much of the allergen in secretions before
it can bind to the deeper cell-bound IgE on the mast
cells in the connective tissue.
• A new experimental approach to treating and
preventing Type-I hypersensitivity involves giving the
person with allergies injections of monoclonal
antibodies that have been made against the
Fc portion of human IgE.
IgE
IgG
Q. how could mothers and
children have the same
allergic reactions?
Type II (Antibody-dependent cytotoxicity)
• Mechanism: Either IgG or IgM is made against normal self
antigens
opsonization of the host cells whereby phagocytes stick to host
cells by way of IgG, and discharge their lysosomes and ;
activation of the classical complement pathway causing
MAC lysis of the cells
ADCC destructionof the host cells whereby NK cells attach to
the Fc portion of the antibodies. The NK cell then release poreforming proteins called perforins and proteolytic enzymes
called granzymes. Granzymes pass through the pores and
activate the enzymes that lead to apoptosis of the infected cell
by means of destruction of its structural cytoskeleton proteins
and by chromosomal degradation.
EX
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•
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MS
Lupus
Pernicious anemia
MS & MG
• Higher levels of Ab to the
myelin basic protein during
flare up
• Myelin BP (insulation around
nerve cells)
• Nerve cells become exposed
• Eventual destruction of the
nerve cell
• -------------------------------• Ab to achl receptors
• Ab comes in and blocks the
ability of AC to bind to the
muscle receptor
• Therefore the muscle cannot
function
Type III (Immune complex-mediated)
• Mechanism: This is caused when soluble antigen-antibody
(IgG or IgM) complexes, which are normally removed by
macrophages in the spleen and liver, form in large amounts and
overwhelm the body . These small complexes lodge in the
capillaries, pass between the endothelial cells of blood vessels especially those in the skin, joints, and kidneys - and become
trapped on the surrounding basement membrane beneath these
cells . The antigen/antibody complexes then activate the
classical complement pathway . This may cause:
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a. massive inflammation, due to complement protein
•
b. influx of neutrophils, due to complement protein , resulting in
neutrophils discharging their lysosomes and causing tissue
destruction and furthes inflammation
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c. MAC lysis of surrounding tissue cells, due to the membrane
attack complex,
Ex
• Rheumatoid Arthritis
• Lupus
Delayed Hypersensitivity (Type IV)
• Delayed hypersensitivity is cellmediated rather than antibodymediated.
• Mechanism: Delayed
hypersensitivity is the same
mechanism as cell-mediated
immunity. T8lymphocytes become
sensitized to an antigen and
differentiate into cytotoxic Tlymphocytes while Th1 type T4lymphocytes become sensitized
to an antigen and produce
cytokines . CTLs, cytokines,
and/or macrophages then cause
harm rather than benefit .
•
•
•
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MS
Scleroderma
Inflammatory bowel disease
(Th17)
Type 1 Diabetes
– MHC II
– T reg Failure
Regulatory T cells
• Regulatory T cells (also known as suppressor T cells) are a
specialized subpopulation of T cells that act to suppress activation of
the immune system and thereby maintain immune system
homeostasis and tolerance to self.
• Similar to other T cells, regulatory T cells develop in the thymus. The
latest research suggests that regulatory T cells are defined by
expression of the forkhead family transcription factor FOXP3
(forkhead box p3).
• Expression of FOXP3 is required for regulatory T cell development
and appears to control a genetic program specifying this cell fate.
The large majority of Foxp3-expressing regulatory T cells are found
within the major histocompatibility complex (MHC) class II restricted
CD4-expressing (CD4+) helper T cell population and express high
levels of the interleukin-2 receptor alpha chain (CD25).
Vitamin D
•
Vitamin D is a potent immune system modulator.
•
The VDR is expressed by most cells of the immune system, including T cells
•
T-helper cells are essentially in charge of modulating autoimmunity.
•
Th1 cells release pro-inflammatory cytokines that lead to tissue damage
associated with autoimmunity.
•
Th2 cells release anti-inflammatory cytokines that balance Th1 activity, so that
an appropriate immune response can occur.
T-regs are responsible for maintaining self-tolerance, so that our immune system
does not react against the body and drive an autoimmune condition.
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Researchers have recently determined that, with inadequate levels of vitamin D,
there is an over-expression of Th1 cells (Tc, TNF-alpha, IF gamma) and an
under-expression of Th2 cells and T-regs.3 Indeed, in vivo studies in the
laboratory have demonstrated that vitamin D therapy leads to a reduction in the
autoimmune Th1 response and a reduction of symptoms of experimental
inflammatory bowel disease, rheumatoid arthritis, type 1 diabetes, and multiple
sclerosis.
Treatments
1.
2.
3.
4.
Plasmaporesis
Drugs that inhibit mitosis (mexotrexate)
Removal of spleen
Blocking Ab
Human disease
Inducing Ag
NOD
Type 1 diabetes
Unknown
NZB
Lupus
Unknown
Expt Autoimmune MG
Myasthenia Gravis
Achl receptors
Expt autoimmune EM
MS
MBP/PLP
Animal Model
Mimicry ?
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Proteins show high levels of homology
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reduction in diet in animal models showed low levels of AID
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Leptin assoc with obesity
Leptin( high homology with IL-2)
Therefore it acts like a cytokine
Found in assoc with fats
Leptin higher in females
Therefore increase in T helper 1 cells, Tc, Mac, Neu, IF-gamma, TNF alpha
In females
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TH1 response (Tc etc)
•
most effective way of getting rid of infectious agents
In males
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Get TH2 response (IL4,IL5 Ab)
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high infections
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Low AI disease
Cancer
2006 Estimated US Cancer Cases*
Men
720,280
Women
679,510
Prostate
33%
31%
Breast
Lung & bronchus
13%
12%
Lung & bronchus
Colon & rectum
10%
11%Colon & rectum
Urinary bladder
6%
6%
Uterine corpus
Melanoma of skin
5%
4%
Non-Hodgkin
lymphoma
4%
Non-Hodgkin
lymphoma
4%
Melanoma of skin
Kidney
3%
3%
Thyroid
Oral cavity
3%
3%
Ovary
Leukemia
3%
2%
Urinary bladder
Pancreas
2%
2%
Pancreas
18%
22%
All Other Sites
All Other Sites
*Excludes basal and squamous cell skin cancers and in situ carcinomas except urinary bladder.
Source: American Cancer Society, 2006.
2006 Estimated US Cancer Deaths*
Lung & bronchus
31%
Colon & rectum
10%
Men
291,270
Women
273,560
26%
Lung & bronchus
15%
Breast
Colon & rectum
Prostate
9%
10%
Pancreas
6%
6%
Pancreas
Leukemia
4%
6%
Ovary
Liver & intrahepatic
bile duct
4%
4%
Leukemia
3%
Esophagus
4%
Non-Hodgkin
lymphoma
Non-Hodgkin
lymphoma
3%
3%
Uterine corpus
2%
Multiple myeloma
Urinary bladder
3%
2%
Brain/ONS
Kidney
3%
All other sites
23%
ONS=Other nervous system.
Source: American Cancer Society, 2006.
23%
All other sites
Cancer: Inside and Outside Factors
Age
Hormones
Diet
Age
Alcohol
Diet
Smoking
Carcinogens
Viruses
Cancer
Time
Age
Alcohol
Diet
Smoking
Obesity
Weak immune
system
Cancer
Breast Cancer Statistics
AGE IS the MOST
IMPORTANT RISK FACTOR
Median Age of Diagnosis is
Between 60-65
Cancer
General Ideas
• Epithelial in origin
•
Rapid proliferation of cells
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Cells found where they shouldn’t be
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Benign = ability to proliferate, but somewhat limited, no movement
•
Malignant= ability of growth to migrate and invade surrounding tissues
•
Tumor Ag very rare (ex PSA = prostate specific)
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Cancer is clonal in origin
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All cancers are heterogeneous
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Selection process sets up heterogeneity
Cancer Origins
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Cancer is clonal in origin
Combination of genetic and epigenetic events
Mutations arise due to deletions, duplications, inversions, translocations.
T
u
normal
What influences cancer?
Environment/lifestyle
•
Certain lifestyle choices are known to increase your risk
of cancer.
•
Smoking, drinking excessively, excessive exposure to
the sun or frequent blistering sunburns.
- U.S. smoking  lung cancer
- China smoked or pickled foods  stomach cancer
Your environment
•
•
•
The environment around you may contain harmful
chemicals that can increase your risk of cancer.
Even if you don't smoke, you might inhale secondhand
smoke if you go places where people are smoking or
you live with someone who smokes.
Chemicals in your home or work environment, such as
asbestos and benzene, also are associated with an
increased risk of cancer.
Heredity
•
Certain cancers run in families (<10%)
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Breast cancer
•
Retinoblastoma (cancer affecting the eye)
What causes cancer?
• Cancer begins with damage (mutations) in your DNA.
• Normal cells often develop mutations in their DNA, but they have the
ability to repair most of these mutations.
• Or, if they can't make the repairs, the cells often die (apoptosis).
However, certain mutations aren't repaired, causing the cells to grow
and become cancerous.
• Mutations also cause cancer cells to live beyond a normal cell life
span. This causes the cancerous cells to accumulate.
• The initial genetic mutation is just the beginning of the process by
which cancer develops. Scientists believe you need a number of
changes within your cells in order to develop cancer
Steps in cancer progression
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•
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An initiator to cause a genetic mutation. Sometimes
you're born with this initial genetic mutation. Other times a
genetic mutation is caused by forces within your body, such
as hormones, viruses and chronic inflammation. Genetic
mutations can also be caused by forces outside of your
body, such as ultraviolet (UV) light from the sun or cancercausing chemicals (carcinogens) in your environment.
Promotion to cause rapid cell growth. Promoters take
advantage of genetic mutations created by initiators.
Promotors cause cells to divide rapidly. This could lead to
a tumor. Promoters could be inherited, could come from
inside your body or could come from outside your body.
Progression to cause cancer to become aggressive and
spread. Progression involves genetic damage that results
in the conversion of benign tumors into malignant
neoplasms capable of invading adjacent tissues and
metastasizing to distant sites Without a progressor a tumor
may remain benign and localized.
Tom Slaga
•Sencar Mice (Sci Park)
•SENCAR is derived from
SENsitivity to CARcinogenesis
•Carcinogen (tobacco tar ) put
on backs of mice
•Didn't get cancer
•Added phorbol myristate
acetate (PMA)
•Became cancerous
Cancer is very heterogeneous
Because of: Large # of cells
Mechanism for selection is achieved by
having high levels of proliferation and
apoptosis occurring.
This will allow the more robust cells to
be selected for
Can survive acidic conditions
High CO2 Low nutrient
requirements (MEM)
These cells may be able to
make all factors that are
required for growth/progression
to occur
The cell is now autonomous to
its environment
HMEC’s (human mammary epithelial cells)
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•
•
•
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Senescent at G1 stage (G0)
Cells were undergoing rapid proliferation and apoptosis
Selection is going to occur here
For cells to start growing, they need to silence other genes (Tumor
supressor genes TSG’s)
Ex Rb, p53, p16
So what allows tumor cells
to form?
Mutation in proto-oncogenes
(oncogenes) gas pedal, cell
prolif
K.O. tumor suppressor genes,
removal of cell brake
Normal cell cycle = 18-24
hours
Tumor cell cycle = 6 hours
P16 methylation
HoxA9 downregulation
Brakes released allowing
Cells to proliferate
Tumor suppressor genes, or more precisely,
the proteins for which they code, either have a dampening
or repressive effect on the regulation of the cell cycle or
promote apoptosis, and sometimes do both. The functions
of tumor suppressor proteins fall into several categories
including:
– Repression of genes that are essential for the continuing of
the cell cycle. If these genes are not expressed, the cell cycle will
not continue, effectively inhibiting cell division.
– Coupling the cell cycle to DNA damage. As long as there is
damaged DNA in the cell, it should not divide. If the damage can
be repaired, the cell cycle can continue.
– If the damage can not be repaired, the cell should initiate
apoptosis, or programmed cell death, to remove the threat it
poses for the greater good of the organism.
P 53 Roles
– Most cancers (60%) have a defective p 53
– There is probably 100% defective p 53 pathways involved
– in cancer
Function of p53
– Checks integrity of the DNA that is about to be replicated.
– Is the DNA worth repairing if there are mutations
– If yes allows replication
– If not Apoptosis
– Rechecks integrity of replicated DNA at checkpoint 2
– Therefore the system is setup to stop tumor formation.
There are 3 major functions that it is involved with inside the
cell.
1. Blocks proliferation (p21 p16)
2. Transcribes DNA repair genes
3. Induced apoptosis
How does p53
exert its function?
• p21 = major block
for cyclin D
• p16 = blocks prolif
pathway ras---erk--akt
Tobacco
aminostilbene arsenic benz[a]anthracene benz[a]pyrene benzene benzo[b]fluoranthene
benzo[c]phenanthrene benzo[f]fluoranthene cadmium chrysene dibenz[a c]anthracene
dibenzo[a e]fluoranthene dibenz[a h]acridine dibenz[a j]acridine dibenzo[c g]carbazone
N-dibutylnitrosamine 2,3-dimethylchrysene indeno[1,2,3-c d]pyrene S-methylchrysene
S-methylfluoranthene alpha-naphthylamine nickel compounds N-nitrosodimethylamine
N-nitrosomethylethylamine N-nitrosodiethylamine N-nitrosonornicotine N-nitrosoanabasine
N-nitrosopiperidine polonium-210
Mutations in p53
• “Hotspots” are regions where mutations appear to occur more frequently
• In p53 sequenced from cancer cells, many mutations are in DNA binding
domain
Tumor Suppressors
Al Knudsen (Cal Tech)
Idea that there was a cancer causing gene proposed
Looked at 100 families for Rb (cancer of the eye)
•
R
L
• Family A
•
B
+
•
C
+
+
• Postulated that there was an element of inheritance
• ie the ability to not get Rblast was inherited in a dominant fashion
•
the ability to get Rb was inherited in a recessive fashion
Bob Weinberg
• 1985
• Isolated and cloned the Rb gene
• Showed that they problem was a result of a deletion
• Rb+ = wt
• Rb- = mutant (deletion)
• Rb is a tumor suppressor (act likes the brakes)
•
•
•
•
•
Note
Rb needs to be unattached for E2F to work
Therefore in the G1 phase E2F is off
Phos-ate Rb to release it from E2F
CDK/Cyclin D/Rb/E2F
PTEN as a tumor suppressor of AKT
Avian erythroblastosis virus
Bishop and Varmus
Looked at RNA virus
• Worked with chicken retrovirus (RNA) RSV
• Found to be harmless.
• One out of 10,000 developed cancer (leukemia)
• Isolated out the retrovirus from that chicken
• Infected 100 new chicks with the isolated “cancer causing strain”
• 100% of the chick got cancer
•
•
So how did this happen?
Idea that there was some sort of conversion from the previous, non-lethal strain to
this new “cancer causing strain”.LTR GAG Pol ENV LTR
Follow-up work showed:
• That Erb B section of cancer causing strain had high homology to EGFR (epidermal
growth factor receptor)
• Proposed that a previous normal gene making EGFR had now changed, mutated,
into this cancer causing oncogene
• The EGFR was regarded as a proto-oncogene (HER2 neu)
How Oncogenes Cause Cancer
• The change of an proto-oncogene from normal to
cancerous function (oncogene) can be caused by a
simple point mutation in the sequence of a gene.
• For example, a change in the ras oncogene,
• Because the signal delivered by the ras oncoprotein is
continuously delivered, the cell continues to grow and
divide. This unabated growth may lead to cancer
development
Microenvironment of cancer cells
T
Nu
Mac
Landscaper
Tu
B
Adipose
Nitric Oxide
Granzymes
Perforin
NK
There is an exchange of cytokines and growth factors between the Tu
cells and the surrounding cells
In the early stages, this support is needed but eventually the Tu cell
with become independent of its surroundings
Increasing # of genetic events will cause this independence
Gatekeeper
• Hereditary forms of cancer
• ex Rb
• If mutation in one allele, will lead to cancer state
• Ex BRCA 1/2 in breast cancer
• Single mutation gives rise to cancer
Caretaker
• P 53 as a caretaker
• Caretakers are normally DNA repair genes
• Therefore it is important for the tumor cell to knock out
these genes
Diet
Do Weight and Diet Affect Breast Cancer Recurrence?
fat tissue produces the hormone estrogen, and estrogen plays a role in the growth of
some breast cancers.
Dietary fat: Some studies did tie high levels of dietary fat to a higher risk of
recurrence.
•Sat Fat,
•Trans fats,
•Fatty red meat
•
•high-fiber diets, because fiber moves food, fluid, and potential toxins through the body
faster, reducing the chance that the body will absorb them.
•certain vitamins and other compounds in fruits and vegetables that might stop or slow
down the growth of cancer cells.
Antioxidants – Vitamin E removal of free radicals
Carcinogen
Water-soluble
carcinogen
Carcinogen
Water-soluble
carcinogen
Diet cont.
• Weight: Some studies showed that the risk of
recurrence in women who were overweight at diagnosis
increased by about a third (for example, the risk of
recurrence could go from 6% to 8%).
• Caloric reduction (40%) has been shown to reduce
incidence/growth of cancer
Possible Hypothesis
• Adiposites have high cytokine release causing high
macrophage /eisinophils presence may lead to the
formation of free radicals and subsequent DNA
damage.
• Problems
– Making people stick to a particular diet is easier said than done!!
ER Status in breast cancer cells
70% +
30% -
Aromatase inhibitors
• Aromatase inhibitors lower the amount of estrogen in post-menopausal
women who have hormone-receptor-positive breast cancer. The
hormone estrogen delivers growth signals to the hormone receptors.
• With less estrogen in the body, the hormone receptors receive fewer
growth signals, and cancer growth can be slowed down or stopped.
• Before menopause, the ovaries produce most of a woman's estrogen, so
reducing estrogen from other sources has little or no effect. But in postmenopausal women, most of the body's estrogen is made from another
hormone, androgen.
• Aromatase inhibitors stop the enzyme called aromatase from turning
androgen into (17 beta estradiol)-----estrogen, lowering the amount of
estrogen produced OUTSIDE the ovaries.
• That means less estrogen in the bloodstream, less estrogen
reaching estrogen receptors, and less cancer cell growth.
Immune System Evasion
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•
•
•
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release of immunosuppressive cytokines
Decoy Receptors
downregulation of MHC I expression
lack of costimulation (B7)
interference with apoptotic pathways
Trojan Horse’ Technology Destroys Blood
Supply to Cancer Tumors in Mice
• Dr. Michael Rosenblum, in mice demonstrated it could selectively
destroy blood vessels supplying human solid tumors without
harming the vasculature of normal tissue.
• “This is like a ‘Trojan horse’ approach to kill the blood vessels that
supply solid tumors.
• using the vascular endothelial growth factor (VEGF) as a carrier to
deliver a toxic agent selectively to the tumor’s blood supply – in
effect, starving the tumor.
• VEGF is one of the predominant factors responsible for
angiogenesis – the ability of a tumor to create new blood vessels to
maintain growth and metastasize.
• The researchers chose the genetically engineered toxin gelonin to
link to the VEGF “carrier” because it does not cause damage to
normal blood vessels as do other toxins that have been explored for
use in anti-tumor therapies,
T reg as a target
• CD25
• FOXP3
• CD4
• Target Treg cells via CD25 (IL-2 alpha chain)
• Tc cells not kept in check and can attack tumor cell
• Side effect is induction of Autoimmunity (T reg prevent this via maintenance
of tolerance)
• Transient application necessary to overcome this
Gene Therapy
• Attach FOXp3 promoter with gelonin to KO T reg's
Boosting the Immune System
• CTLA-4 functions as a negative regulator of Tc proliferation.
• B7 required for Tc stilumation
• Following stimulation transcritption of CTLA-4 occurs and begins to reduce
Tc proliferation
• Blockage of CTLA-4 allows increase in Tc proliferation and enhanced
response to tumors
Treatments
Surgery is used to remove a tumor that is localized in a tissue or organ. The surgeon
removes the cancer cells or the tumor completely. Some healthy cells may also be
removed to make sure that all the cancer is gone. Surgery is often combined with
chemotherapy and/or radiation to ensure all cancer cells are removed.
Radiation is one of the most common treatments for cancer. The radiologist aims a
beam of high-energy rays, such as X-rays and gamma rays, directly onto a tumor
using a radiotherapy machine. These beams of radiation are many times more
powerful than those produced in ordinary x-ray machines, in that they can damage
and destroy cancer cells causing the tumor to shrink and even remove it completely.
In order to focus the beam accurately onto the tumor, many X-rays films and
Computer Tomography (CT) scans are taken to identify the exact position of the
tumor.
Chemotherapy usually consists of a combination of several anti-cancer drugs.. It may be
given alone or in combination with radiation therapy.
Biological Therapy is a treatment that uses the body own natural defense system known
as the immune system. (TIL)
Biotherapy is designed to repair, stimulate, and improve the ability of the patient's
immune system to fight cancer.
Biological therapy uses substances such as antibodies which home in directly to the
site of the cancer.
It is used either alone, or in conjunction with other conventional treatments such as
surgery, radiation and chemotherapy.
Good Luck!!!!
Thanks for a great last semester