An undead city under siege, soldiers and police
ruthlessly shooting down waves of zombies that flood from infected streets, trying to escape
and infect more cities. This is what happens when your body fights cancer, more exciting than any
movie. How does this battle for survival unfold? 1. The Elimination Phase It all begins with a single corrupted cell. It
is no longer able to repair its genetic code, it can’t kill itself anymore and it is beginning
to multiply rapidly. At this point things are not great, not terrible – this cell is not yet
dangerous but if nothing happens, it soon will be. Over a few weeks the corrupted cell keeps making
copies of itself. One cell turns into dozens, hundreds, thousands. Because the
original was broken, its copies are breaking and mutating even more. They
turn into different genetic lineages, clans that are working together and competing.
Some mutate in a way that makes them weaker, others’ mutations don’t change anything,
while a few become fitter and better at survival. Together they now form a tiny, tiny
tumor. Not cancer yet, but getting there. The growing tumor needs a lot of resources.
If the cells don’t get food and oxygen, they will die and the problem just solves itself.
Unfortunately a few corrupted cells unlock a new mutation that saves them: The ability to
order the growth of new blood vessels. And so your body provides the supply they need to
survive. But as the tumor continues to grow, it starts causing damage – Neighbouring
healthy cells begin to starve and die, which attracts attention. In a sense
this tiny tumor is like a rogue town. Imagine a group of rebels in Brooklyn decided that
they were no longer part of New York but started a new settlement called Tumor Town, which happens to
occupy the same space. The new city wants to grow, so it orders tons of steel beams, cement
and drywall. New buildings follow no logic, are badly planned, ugly and dangerously crooked.
They are built right in the middle of streets, on top of playgrounds and on existing
infrastructure. The old neighborhood is torn down or overbuilt to make
room for new stuff. Many of the former residents are trapped in the
middle of it and begin to starve. This goes on for a while until the
smell of death finally attracts attention. Building inspectors and police show up. In your body, attracted by the stench of dead
cells your immune system is activated. First responder immune cells invade the tumor:
Macrophages and Natural Killer Cells, police forces that go right to work, killing
and eating tumor cells. They release chemical signals that let the whole immune system
know that there is cancer to be eradicated. Dendritic Cells, the intelligence
officers of your immune system, collect samples of dead tumor cells and begin
activating your heavy weapons: Helper and Killer T Cells. We explained these specialized super
weapons in another video, but all you really need to know is that they have a library listing
every bad thing that could come into your body. While each cancer is unique, there are
genetic corruptions that they can’t hide. And your T Cells know what to look for. They
are the deadliest cancer killers you have. By the time they arrive, the tumor has
grown to hundreds of thousands of cells, but this is about to change. T Cells
block the growth of new blood vessels, which starves thousands of tumor
cells and puts an end to their growth. Imagine the building inspectors, switching
off electricity and water and putting up roadblocks to cancertown so no more
food and materials can be delivered. With no way to hide from the carnage unfolding,
the tumor collapses as hundreds of thousands of tumor cells are massacred. Their carcasses are
cleaned up and consumed by Macrophages that then order healthy tissue to regenerate. Your body
has crushed the illegal Tumor Town without mercy. You will never know about this fight or how
many times this has happened inside your body. Except… in this case something
did not go as planned. 2. The Equilibrium Phase Unfortunately, natural selection spoils your
victory. By doing its best to destroy the tumor, your immune system accidentally selects
the fittest tumor cells. Remember, the tumor consists of different lineages
that keep growing and keep mutating. Most of these are eradicated. But just a few
are more resilient. One cell survives – it comes from the fittest tumor lineage and was
just a bit better at surviving the massacre than anyone else. It decides to do it
all over again. But better this time. This tumor cell is much stronger than any of
the thousands that were killed. Maybe it is better at hiding, or fighting back. Maybe
it grows faster or is better at stealing resources. Maybe it can survive with much
less oxygen. And so it all begins again. It's like the surviving rebels that started
Tumor Town have learned their lessons. Now they know the law better and how to break it,
what permits help them, how to avoid the police. And so the surviving tumor cell makes thousands
of copies that mutate and form new lineages, until once again a tumor has grown,
made up from more resilient cells. The immune system does not care though, and this
time it even has experience - instead of starting with police, swat teams go right in to tear Tumor
Town down, killing its inhabitants without mercy. But once again they don’t get everyone. One
of them survives: a fitter tumor Cell from an already fitter lineage. This time it gets
a cheap suit and studies the building code, pretending to be a lawyer to start Tumor Town all
over again. This struggle now repeats a few times, each time the rebels learn a bit more about
how to avoid the law. If at any point, the immune system gets all of the tumor cells,
the story ends. But in this case, it doesn’t. Finally, a tumor cell changes in a way
that makes it properly dangerous, cancer. The type that kills people. How? Immune cells have an off switch that deactivates
them before they can attack – which in principle is a good idea. The immune system is extremely
dangerous and in many cases it needs to be shut down, like around your central nervous
system. But this off switch can be exploited. The mutated tumor cell finds a way to switch the
immune system off by targeting inhibitor receptors on anti cancer cells. Inhibitor receptors
stop immune cells from, well, killing. This cell is the now powerful founder of a
new lineage of cancer cells and mass produces thousands of new copies that once again change and
mutate further. Building yet another Tumor Town. 3. The Escape Phase The new cancer cells have become immune to
the immune system and everything is different this time. Tumor Town has been rebuilt,
even uglier and stranger than before, but now the cancer city council
has forged all sorts of permits. As building inspectors come to shut
down construction, they get confused. Stunned they wander off, unable to order
the destruction of the sprawling buildings. Police try to enter the illegal city
to arrest the builders and execute inhabitants – but this time Tumor Town
has erected its own roadblocks that keep the law from entering. Confused
officers stand around helplessly. As Tumor Town slowly envelops the former
Brooklyn and more and more civilians die, T Cell swat teams arrive to end this travesty.
But things got worse – new lineages of Tumor Town officials have started to forge court documents
that order police to shoot at the Swat teams. What the cancer cells are doing at this
point is actively shutting down immune defenses by sending corrupt signals. The now
malignant tumor is no longer a pushover and has begun creating the Cancer Microenvironment.
A sort of borderland that is hard to cross. All avenues of attack have been shut down and
uncontrollable growth is the consequence.
This is a dangerous tumor. Cells
that are strong and able to fight, push your immune system back and expand further.
If more mutations happen, then some of the cancer cells will begin to explore the world and
expand into other tissues, to build new towns. And this is exactly what makes cancer
so harmful: it is taking up space and stealing so many nutrients that your true
self has no room to function anymore. If this goes on for too
long, organs will shut down. But this tactic is a dead end. The more
successful cancer gets, the more damage it does to its world. When the body dies, the cancer
dies too. It truly is a game without winners. Except, humanity is planning to win this game. At this moment hundreds of thousands of scientists
are working on new and better ways of killing cancer, to destroy and burn down Tumor Towns
for good. In recent years immunotherapy has made enormous progress – it is a relatively
new therapy in which your own immune cells are modified to kill cancer better than any medicine
can do. It's like giving your building inspectors machine guns and flamethrowers. But this is a
story another time – For now cancer is a battleground – but if human
ingenuity is to be trusted, then one day, maybe in the not too distant future, we
will eradicate it once and for all. This video was made possible in part
by direct viewer support and in part through a grant by Gates Ventures.
Thanks a lot for their support! Please check out our source document for
more background and in depth information!
