Oh hello there!
Did you know that cancer is the second leading
cause of death globally after heart disease?
A lot of money has been poured into research
over finding possible treatments for this
deadly disease.
During this research, a lot of interesting
observations have been made.
One such observation was made by Richard Peto,
a statistical epidemiologist at Oxford university.
He discovered that large organisms get a lot
less cancer than they should be getting.
This is called Petos paradox.
But before i dive deeper into this paradox,
i would like to take a short detour and explain
what cancer actually is.
Cancer is caused due to an accumulation of
errors in the copying of DNA for cell division.
In general, these errors are quite harmless.
The cell fixes them quickly.
And if too many such errors, also known as
mutations occur, well then the cell simply
kills itself.
However, these "kill switches" are not fool
proof.
When mutations happen in certain genes called
proto-oncogenes, its very bad news.
The right mutation can cause the cell to lose
the ability to kill itself.
Another, and the cell gains the ability to
hide . Another, and the cells start dividing
rapidly.
Now, these mutations happen by chance.
So, one would obviously expect that if you
had a larger organism with more cells, and
if it lived longer, then there is a greater
chance that one of its cells would turn cancerous.
Indeed, within organisms of the same species,
this what you observe.
However, this relationship breaks down when
you compare organisms of different species.
Take the example of a human and a mouse.
No, not that mouse, this mouse.
A human has 1000 times more cells than a mouse,
and he usually lives 40 times longer.
However, the rates of cancer incidence in
humans and mice, are practically the same.And
blue whales? with over 2000 times more cells
than a human?
They practically don't get cancer at all.
This is Peto's paradox.
A lot of solutions have been proposed to petos
paradox, one of them being, that large organisms
are simply better at suppressing cancer.
Remember the proto oncogenes i talked about
before?
Well they have an antagonist.
Tumor suppressor genes(TSG).
Take the case of the TSG TP53.
Humans and mice have only one copy of this
gene in their genome.
Whereas elephants?
They have 20.
There is however another far more interesting
solution to this paradox: Hypertumors.
Hypertumors are named after hyperparasites,
which are the parasites of parasites.
In large organisms, tumors need to grow a
lot more in order to do any real harm.
As the tumor grows, the cells accumulate secondary
mutations.
And if enough of these mutations occur, some
of the cells may start a new tumor on top
of the original tumor, a hypertumor.
This hypertumor sucks nutrients from the original
tumor, causing it to starve and die.
As the hypertumor loses its own source of
nutrients, it also starts to starve and die.
It may be that large organisms are covered
in cancer, except none of the tumors get big
enough to do any real harm.
There is a lot we can learn from these phenomenon,
and how large animals deal with cancer.
Who knows?
maybe in the next 10 years, we might actually
have a cure for cancer.
The future is bright, and the sky is the limit.
Thanks for Watching!
