[thedoc (OP)]

How does cancer evade the body? How does this escape the clutches of say, the immune system getting rid of cancerous cells? If genetics allow cells to replicate uncontrollably, why hasn’t genetics evolve to boot the cancer out?”
Asked by Les in Over


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[thedoc (OP)]

We answered this question on the show...

 Mark D. -   The truth is that the process of cancer is actually a very rare event.  Many of our cells are developing genetic abnormalities all the time and the immune system does a very good job [of clearing them out].  Also some of these genetic events actually are deleterious for the cell itself, so they end up dying of their own mutations.  Very, very rarely, you get this perfect storm really where you have a cell that is able to survive and grow uncontrollably and also evade the immune system.  And tumour surveillance or the study of cancer immunology is a huge field that is trying to understand this problem.

[2dogmom]

I think the reply should also have addressed a couple of other points  1)  as most cancer cells do not have proteins that would be considered "foreign", such as fusion proteins, there is no reason the immune system should see them as foreign and attack them.  2)  for something to affect evolution, it would have to provide a selective advantage that can be selected for.  As cancer is rare in young people and most cancers develop long after most of us have reproduced, and the very things that cause cancers (gene mutations, gene rearrangements) are also things that would be selected FOR, we only need to have the ability to block or detect cancers that would affect a large number of young people. 

[Ian]

@2dogmom
You’ve made very good points’ There is so much reference to so called Natural Killer Cells, etc -  yet seemingly so little clear evidence as to their unaided role in cancer, If they actually have a role at all in most cancers!
This also reminded me on a conversation I had a number of years ago with a very well known Nobel laureate who has served his time working with cells, While asking about the role of the immune system he replied with the following question ”How is our immune system supposed to know the difference in cancer cells & our own?”

So much has yet to be understood about the complexities of cellular signalling & behaviour. We desperately need a window into metastatic traffic at the cellular level as opposed to today’s crude approaches to monitoring.

[cheryl j]

I was taught the Natural Killer cells don't look for foreign or abnormal receptors on cells (the way that other white blood cells attack specific bacteria). Natural Killer cells look for normal receptors, and if a cell doesn't have it, it gets taken out.

There are also genes like gene P-53 that makes a protein that suppresses tumors, but if you are missing that gene, or it mutates, tumors develop more easily.