Normally, if an epithelial cell is sloughed off and
accidentally enters the bloodstream it will die.
In the last section, we covered that and that form of cell death is known anoikis.
Other methods of death include immune cell destruction because
the immune cells undergoes surveillance of the circulation at all times.
And if there are foreign cells or
foreign bodies the immune system will clear them out by phagocytosis.
Another method in which a cell that gets in the circulation can die
is by shear blood pressure which can cause extreme cell lysis.
Especially, going from the venous system into the heart and
back out of the heart, so a cell must survive that as well.
So cancer cells or CTC evade all three of these forms of cell death.
That is anoikis, immune surveillance and shear blood pressure.
And they are able to enter the circulation, and
go undetected for a period of time.
And this is a active area of research right now, so
a CTC is short for a circulating tumor cell.
And it is a cell that has entered the bloodstream and, or lymphatics, and
has the ability to survive for a period of time while in the circulation.
CTCs have been shown to exist as a single cell or,
as a hetero-cellular cluster of cells that can travel throughout the human body.
On the left, you can see a breast cancer that is localized and upon magnification,
you can see that the primary tumor typically is hetero-cellular as well.
And these cells can enter into the bloodstream directly or
through the lymphatics and then into the bloodstream.
As a single cell or a CTC cluster And then metastasis to a distant
site such as the lungs as a single cell or as a hetero-cellular cluster.
Again, a circulating tumor cell has the ability to evade anoikis
as lost metastasis suppressed genes and
fit to withstand blood pressure to get to the lungs.