As we saw earlier on the inflammation page, the immune system plays a large role in the fight (and promoting) of cancer growth. The fighting portion that comes from the cytotoxic T lymphocytes (CTL) can be destructive to the cancer. So what if the cancer could turn them off?
There are a few mechanisms in which cancer cells can turn off the immune system to prevent its own destruction. Here are a couple.
CTLA4. CTLA4 is a cell surface protein on CTLs that binds to another surface protein, called CD80 and CD86, that is on a cell that tells the T cell what the cancer cell looks like so it knows what to kill. This binding inhibits the function of CTLs, thus preventing cancer death.
PD-1 and PDL-1. PD-1 is another surface molecule that is on the CTLs. PDL-1 is a molecule that binds PD-1, thus inhibiting the CTLs function.
Currently, there are some therapies to help the immune system combat cancer. Here are a few.
Vaccines. Cancer vaccines are used to prime the immune system to locate and recognize cancer cells for destruction. Unlike the vaccines that we are given before we get the disease, these vaccines are given after the cancer has been detected.
Anti-PD-1, anti-PDL-1, and anti-CTLA4. These are molecules, usually special types of proteins called antibodies, that can specifically bind to PD-1, PDL-1, or CTLA4. The binding of these molecules will prevent their binding from their respective “binder”. For example, if one uses an anti-PD-1 molecule as a treatment, this molecule will bind to PD-1. Then, when it is time for PD-1 to bind to PDL-1, the binding cannot happen because anti-PD-1 is in the way. Thus, the CTLs will not receive the signal to stop killing cancer cells.
Sources: http://www.uky.edu/~hadleyr/PA2008/Harper.ppt
http://www.hegasy.de
https://reverehealth.com/live-better/brief-overview-immune-system/
Topics in Cancer Biology 