Doctors have known
about checkpoint inhibitors for years, but when dealing with cancer and the
action and reaction of the body at the CELL level, it takes time and effort to
understand what is happening.
For starters, we
all know that cancer cells are ones that have started to grow uncontrollably,
creating a tumor. There are over a hundred different cancers that affect the
human body. Many of these can cause breast cancer. Even within the types that
cause breast cancer, there are other, even more specific types – it’s like
saying that you have DOGS. Within that kind of mammal, there are many kinds of
dogs. If you choose one type, say Retrievers, you have black labs, chocolate
labs, and golden labs t0 name a few. Breast cancer is like that.
What every cancer
cell of any type has in common with every other type, is the ability to fool
the body into thinking that it’s “just a normal cell”. When it does that, the
normal body response of sending T-cells to wipe out invaders is fooled. These
T-cells are strong. Very strong. If they get out of control, it can cause
horrific damage through a type of reaction called an “auto-immune disease”. The
best known of these is rheumatoid arthritis in which the body attacks itself.
So T-cells have very tough “leashes” to keep them under control.
A T-cell arrives
to attack an internal invader, but the skin of the cancer cell says, “Nobody
here but us fat cells! False alarm! Go away! We’re cool!” The cancer has fooled
the T-cell and gets off scot-free, continuing to grow out of control.
“Immune
checkpoints are molecules in the immune system that either turn up a signal
(co-stimulatory molecules) or turn down a signal. Many cancers protect
themselves from the immune system by inhibiting the T cell signal.”
What’s that mean?
Just that these “immune checkpoint molecules” are signals that tell the rest of
the T-cells what to do and where to do it. Cancer blocks or muffles the signal
so that the body doesn’t respond as strongly as it should, so the cancer keeps
growing.
So what City of
Hope is saying is that one of the future therapies may be to
“blockade [the]
immune checkpoints” of cancer cells. Your body has many ways to stop the
T-cells from getting out of control – checkpoints. You might imagine them as
similar to the old “Checkpoint Charlie”, the famous gate from the Cold War
through which people from East Berlin and West Berlin could pass from one city
to another.
“Immune
checkpoints refer to a plethora of inhibitory pathways hardwired into the
immune system that are crucial for maintaining self-tolerance and modulating
the duration and amplitude of physiological immune responses in peripheral
tissues in order to minimize collateral tissue damage.” In plain English? These
checkpoints keep your body from attacking itself as well as make NECESSARY
immune responses strong and clearly aimed at the invading cells.
“It is now clear
that tumours co-opt certain immune-checkpoint pathways as a major mechanism of
immune resistance”, in other words, cancer cells take over those checkpoints
and tell the T-cells that they’re OK. The body stops attacking and the tumor
grows out of control until it’s removed surgically, with radiation, or with
chemicals.
So, there’s LOTS
of research going on now to create a treatment that will boost the signal from
the T-cell that encounters a cancer cell in order to tell the rest of the body
that an invasion has begun. The treatment IS NOT READY, but the research is
promising!
Resources: http://www.cityofhope.org/blog/breast-cancer-dramatic-advances-create-revolution-in-treatment,
http://www.ncbi.nlm.nih.gov/pubmed/22437870
Image: https://image.shutterstock.com/image-photo/closeup-word-encore-painted-on-450w-1143919607.jpg
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