So what are some of the factors
that are going to influence cell division?
So there are multiple factors that
that will tell a cell it needs to divide.
There are some external factors such as growth factors
that trigger the production or stimulate cell division
and there are also factors such as
platelet-derived growth factor, or PDGF
which are going to stimulate
the production of platelets.
In all of these different things, what we want is
for the cells to divide and create a monolayer.
So one single layer from most cells,
and once we create that monolayer,
we don't want the cells to get overcrowded.
So we will also secrete factor that
tell the cells to stop dividing as well
Along with that, most of our cells with
the exception of things like red blood cells
which are gonna flow through our blood vessels
and through the plasma in our blood vessels.
Most of our cells are anchored down to
a medium, they are attached to something
and in order to divide, they must
remain attached to something.
And so with these two together, density-dependent
inhibition and anchorage-dependent cells
must grow at an optimal density and be
stuck to some type of layer or substratum.
When it comes to cancer,
this process is inhibited.
So in cancer cells, either they
lose their density-dependence
or they lose their anchorage-dependence.
This allows for tumor formation to
occur because the cells are now allowing
themselves to just start growing on top of
each other whereas they normally wouln't do that.
And as well, this allows for malignancy because now
cells are no longer required to be stuck to a substratum
and they can now flow to other parts of the body where
then they form tumors in other parts of the body.
And so here's just an
example of how this works.
Again, you have anchorage-dependents where
the cells must be in a surface in order to divide.
And you have density-dependents where the
cells do not not allow themselves to overcrowd.
They form a single layer and
after that, they say "stop dividing".
So cancer cells do not
actually follow these rules.
And your cancer cells instead of a
responding normally to these control mechanisms
such as density-dependents and anchorage-dependents,
they just do what they want to do.
On top of that, they also may not
need growth factors to grow and divide
so therefore they are able to
ignore these control mechanisms.
Sometimes cancer cells are able
to make their own growth factors,
or they're able to convey the signal of a growth
factor without the growth factor actually being present.
And then finally, sometimes they have
an abnormal cell cycle control system
So remember, back on the previous slide when I
said that we have that prep stage of the interface
where we prepare to divide,
Well, something happens there that even
when they proofread and realize it's wrong
instead of fixing it, they just keep going and allow the
wrong thing to be just replicated over and over and over
and therefore we continue
producing more and more cancer cells
So this is how tumors can be formed.
So a normal cell can be converted to a
cancer cell in a process known as transformation.
And then, if these cancerous cells are not removed,
recognized or removed by our immune system,
they can now form these tumors
in our otherwise normal tissue.
If the abnormal cells or
the tumor does not move,
if it just stays where it's growing
and just creates this lump in one place,
it is referred to as a benign tumor.
It is not until a tumor becomes
mobile or detaches from its original site
and moves to other parts of the body that
it's referred to as metastatic.
In metastasis, we are now
taking these abnormal cells
and they enter into the cardiovascular
system or the lymphatic system
and are able to move to other parts of
the body where they now are forming tumors
and places away from the original site.
And the more tumors that these formed, then
the more problems they begin to cause in the body.