Why do cancer cells move to different parts of the body?

Question

How exactly do they move into the blood stream?

Answer 1

This is the subject of a LOT of research right now...

But basically...consider your whole body as pulsating fluid mass...which it basically is. ALL live cells require oxygen and need to get rid of waste products of metabolism. Therefore, all live cells have blood flowing to and from them. Tissues are immersed in this fluid...the drains throught the lymphatics, which collect all the fluid and return it to the blood stream. The blood is pumped along by the heart...through the lungs (exchanging oxygen for carbon dioxide) and through the kidneys (filtering out all the waste...which is urinated away).

Miraculously (it would seem), cells next to each other in tissues communicate and somehow obey certain rules...like not encroaching upon one another, yet adhering to each other. This is built into the genetic code...part of the way we are created.

When (like in a skin laceration or cut), a hole suddenly appears between cells, then this triggers those cells to divide...and divide...and divide again...until the hole is "plugged" up...and the cut is healed. Once "plugged" up...the cells next to each other recognize this...and stop dividing. Kind of like how people put up fences between yards in neighborhoods...and people respect the fences...and do not trespass...

In cancer...a mutation occurs (some defect in the dividing machinery of the cell, the DNA)...and cells no longer obey the rules. They don't get the signal to stop dividing...and they keep on dividing and dividing...in what is called "uncontrolled cell growth"...which is essentially what cancer is. It is kind of like your neighbors having tons of kids...that keep going under your fence into your yard...trespassing.

This rapid and uncontrolled cell growth makes a bunch of "extra" cells in the organ...forming a mass...a tumor.

These tumors are a group of live cells...growing very fast...and need a lot of oxygen, nutrients...and need a way to get rid of all the waste they make. Kind of like those neighbors' kids...who need food, drink..and make poop and pee.

So...these cells release chemicals into the area around them...which promote blood vessel growth. This is called "angiogenesis"...which basically means "growth of blood vessels". I guess, continuing the analogy, the neighbors' kids start screaming in hunger (the signal for angiogensis), so the neighbors keep feeding them and changing diapers, etc...perhaps even creating a conveyor belt (new blood vessel) to transport food and trash back and forth (as all the 1000+ kids no longer fit in their house)!

Getting to your question more specifically, as these rule-breaking cells grow more and more unruly, they are prone to more mutations...and break even more rules. Another mutation and with more blood flowing past the tumor, and the cells are likely not to adhere to one another as well (the normal rules). Then, a cell from the tumor floats away in the stream of pulsating blood that surrounds them. It is carried by fluid flow through the lymphatics...and into the bloodstream. This is like one of the kids running away.

It probably happens frequently in cancers that do not "officially" metastasize...as the cell floats away...but then dies, as it has no nutrients or way to live. Perhaps it gets chopped up in the spleen...or just breaks down in the bloodstream...with its remnants filtered through the kidney and urinated away. This is the child that runs away, but has no way to survive out in the wilderness...and dies.

However, some cells flowing throught the blood stream find a new home...as they get lodged in the liver...or lungs...or even into the brain. They land on a different tissue...but manage to get oxygen, nutrients...and their waste products are taken care of. They set up a new life...and keep on dividing. And so, you get a new tumor in a foreign organ (a metastasis) that keeps on growing and invading the other organ...until the other organ is overwhelmed...and malfunctions. This is like an older kid that runs away from home...finds a new life, living off some other person or family and starts to have a bunch of kids until it overwhelmes the other family...

So, basically, several mutations...and the cells stop obeying normal dividing and adhering rules, and they get wisked away in the pulsating blood supply all around them...into the lymphatics and on into the bloodstream...only to land in another part of the body...where they likely got lodged like a small twig that was in a mighty river and floated off into a smaller side stream...further and further into smaller streams...until it just stopped in a new place, in more stagnant water...

...or, well...something like that anyway...

Perhaps the link below would be more beneficial...