our immune system is equipped with cells
that form an army that help our body
defend itself and fight foreign invaders
some of these immune cells called
t-cells and b-cells are programmed to
get rid of four invaders like viruses
and bacteria t-cells release toxins
against the foreign invaders and B cells
make antibodies to neutralize them we
have known for some time that our immune
cells can recognize cancer cells as
foreign invaders and attack them by
secreting special factors or weapons how
can our immune cells do this the organs
of our body are composed of billions of
cells these cells contain thousands of
proteins that act like worker bees and
are responsible for the function of our
cells
these proteins break into small parts
called peptides some of these travel to
the surface of ourselves and are
presented by molecules called MHC or HLA
t-cells continuously scan the surface of
these cells through the t-cell receptor
or TCR the TCR works as a barcode
scanning machine and the peptides
presented on the cells are unique
barcodes this function of the T cells is
called surveillance if T cells recognize
these peptides as normal then the T
cells move on but if the peptides come
from foreign invader proteins then the T
cells get activated to attack the
invader cell with weapons to eliminate
it the T cells secrete certain proteins
and chemicals called cytokines and
factors these molecules punch holes into
the cells that contain the invading
organisms proteins are your body's basic
building blocks they allow yourselves to
divide rest and function properly but
sometimes these proteins get changed or
mutated for example smoking leads to
mutations that make abnormal proteins in
our lung cells sometimes when these
proteins are changed they stop
functioning normally this makes the cell
become cancerous by making it grow and
divide to become cancer these mutated
proteins are also broken down into
smaller pieces and are presented as
peptides on the surface of the cancer
cell these abnormal peptides are
recognized by the TCR as foreign and
activate the T cells to kill the cancer
cells but if the immune system can
recognize and eliminate cancer then why
do people develop cancer sometimes the
immune system fails to do its job
the immune response against cancer may
not be strong enough or cancer cells may
evade the immune system tumors or a
group of cancer cells can build a
defense Network against our immune
system these defense mechanisms can
either prevent the immune army from
entering the tumor or can weaken and
inhibit the T cells for example tumors
can express attack molecules on their
surface that bind to the T cells and
inhibit their killing activity these
molecules are called checkpoints and
examples are P d1 and ctla-4 the tumor
can also secrete proteins factors and
cytokines that inhibit t-cells from
attacking and killing cancer cells and
can also turn the t-cells into friends
of the tumor these cells can then
deactivate other T cells these trader T
cells are called T regulatory cells and
are the enemy of the killer T cell army
the field of immunotherapy has shown
great progress toward a cure for cancer
after working at it for many years with
some major recent breakthroughs
immunotherapy is actually one of the
most important revolutions in the
history of medicine what are the
different types of immunotherapy
immunotherapy functions in two primary
ways by enhancing the immune system and
making them stronger and by using drugs
that help inhibit the suppressive immune
environment of the tumors
one enhancement method is to create
vaccines foreign antigens can be
identified by identifying mutated
proteins in the tumor these mutated
proteins called neo antigens can be
given as a cancer vaccine the cancer
vaccine is developed to activate the
patient's own t-cells against the
foreign antigens like the flu vaccine
fights against the viruses the tumor
vaccine fights against the foreign tumor
cells now that the T cells are trained
by the neo antigen vaccine they go
around the body to find those specific
mutated antigens and will locate them on
the tumors another enhancement approach
is adoptive t-cell transfer where
t-cells are taken out of the patient's
body grown in laboratory and educated to
recognize cancer or even modified to
become much stronger these fighter cells
are then transferred back into the
patient a third enhancement approach is
using stimulating factors called
cytokines cytokines are stimulating
proteins like interleukin 2 7 12 and 15
that cause the T cells to significantly
multiply and get stronger
a fourth enhancement approach uses
agonist antibodies such as anti Oxford
II anti GI TR and anti 4:1 BB and others
to cause the T cells to grow and
strengthen this allows the enhanced
t-cell to overwhelm the cancer cells a
second approach to immunotherapy
strategies have been developed to knock
down cancer defense mechanisms there are
antibodies that neutralize the
inhibitory factors and cytokines such as
anti il-10 and anti tgf-beta and ideal
inhibitors some of these approaches have
already been approved by the FDA like
anti pd-1 and anti ctla4 for example
patients in this clinical trial have
melanoma the kind of skin cancer
50% of people with advanced melanoma die
in 12 months until recently patients
were treated with antibodies against
both ctla-4 and pd1 growth of the
melanoma tumor in different patients was
recorded and plotted out in a graph the
growth lines show that targeting both
ctla-4 and pd1 encourages t-cells to
fight cancer with this combination
approach 70% of patients with advanced
melanoma continue to survive more than 3
years these therapies also have some
side effects that need to be monitored
very closely by the treating physician
although the side effects are not very
common they could be life-threatening if
not treated these side effects are
treatable
especially if discovered early which
include diarrhea because of inflammation
in the intestine include some endocrine
diseases that lead to weakness thyroid
dysfunction or diabetes and other side
effects that need to be discussed with
the treating team the future of
immunotherapy is in combining different
approaches to accomplish two goals to
create a trained army of cells to attack
the cancer and to break down the
defences of these cancers by unleashing
your own immune defense against cancer
to improve on the currently very
impressive results that immunotherapy is
already providing our patients
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