When you talk about cancer, is there a difference between tumor cells and host cells ? What is the role of immune cells ? in a nutshell ?

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    $\begingroup$ I think this is way too broad to be able to answer. There are many different type of tumor and "host" (normal body) cells, and they differ in a variety of ways. It sounds like you're pretty much asking to sum up all of cancer biology ... $\endgroup$ – Roland Nov 18 '15 at 17:19
  • $\begingroup$ In the comments of FrankyG's answer I posted a review of the hallmarks of cancer. For that reviews purpose, cancerous hallmarks can be subdivided 6 major ways. Consequently, you can subdivide either of those six hallmarks into multiple specific pathways, each of which could merit their own graduate-level course exploring. For SE's purpose, the scope of your question is very broad! Here's my recommendation: (1) Search the site, there are good answers buried somewhere, and (2) read up before you ask your question so it has some specificity! $\endgroup$ – CKM Nov 18 '15 at 19:35
  • $\begingroup$ This is far too broad. Asking "what is the role of immune cells?" in cancer is the subject of literally thousands of research papers every year. $\endgroup$ – MattDMo Nov 18 '15 at 20:27

This question is a bit broad but I'll try to narrow it to be specific in the terms of "tumor" vs "normal" cells.

enter image description here (Source)

Basically a tumor contains cells which have a part of the cell cycle regulation broken (very broad way of saying this). There are literally thousands of things that can cause this. Broad groups of things that cause this could be knockdown of a protein (of which many are involved in replication), mutation of a gene (most likely), etc etc. Basically any type of DNA damage can lead to cancer.

enter image description here (Source)

So what creates damaged DNA? Well here is a small list:

  • UV light (Can cause DSBs)
  • Carcinogenic chemicals (eg: Ethidium Bromide)
  • Replication proteins getting stuck or loosing function

enter image description here (Source)

Well how does that compare to a "normal" cell. Normal cells have a proper cell cycle with all the "checkpoints" working normally to essentially throw away any cells that detract from the cycle in any way. They also have mechanisms to fix DNA that has been damaged before it gets replicated. If none of that works they have mechanisms to basically commit suicide so they never replicated. When all of that fails you get cancer.

In summary, a cell becomes cancerous when the following things happen:

  • DNA is damaged by one of the above methods
  • The DNA damage repair mechanisms fail to fix the damage, or cause further problems by attempting to repair (NHEJ is a repair mechanism for DSBs that is implicated in causing cancer)
  • The DNA damage causes abnormalities in the cell cycle (replication)
  • The body fails to recognize the particular cell with abnormalities in order to kill it
  • The abnormal cell is allowed to replicate without hindrance from the body's checkpoint mechanism
  • You now have cancer

As for the role of immune cells that question is too broad as there are many different types of immune cells. Their "general" role is to clean the body of foreign agents but there are differences even in that role. There are many different types of them.

enter image description here (Source)

While I love teaching this stuff I do feel like you could find A LOT of this by doing google searches. Please try that next time.

EDIT: Updated with plenty of sources.

  • $\begingroup$ Nice answer. However it would have been way better if you could have added references to your points and images. $\endgroup$ – Dexter Nov 18 '15 at 18:35
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    $\begingroup$ True but to be fair a lot of this is found with simple google searches which is what I told him to do next time at the bottom. $\endgroup$ – FrankyG Nov 18 '15 at 18:39
  • $\begingroup$ I agree. But you should try to give scientific references if possible. And definitely image source. $\endgroup$ – Dexter Nov 18 '15 at 18:42
  • $\begingroup$ For these types of questions I feel Hallmarks of Cancer: The Next Generation is an informative survey of the differences between cancerous and healthy cells (It's also open access!). I suppose it also requires a little background in what constitutes "healthy," however. $\endgroup$ – CKM Nov 18 '15 at 19:20
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    $\begingroup$ @MattDMo I'm well aware of what scientists expect (am one myself). This was an oversight of mine, I apologize for that. Dexter already made me aware. As you can see I changed it. $\endgroup$ – FrankyG Nov 18 '15 at 20:57

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