if cancer is basically a clump of cells that dont want to die, why/how do things like cigarettes, asbestos, and the literal sun trigger it?
In: Biology
Immuno-oncologist; I will try to make it as basic as I can but realize there are millions of minor facts that fit in the middle of this broad overview.
First off it is important to understand cells. Cells are the ultimate team players. They are programmed to kill themselves if there is something wrong with them and they are able to start the cycle of killing themselves. If they don’t grow up correctly, if they aren’t doing their job properly and when they get too old; boom suicide. This is called apoptosis. What is also important about cells it to realize that they communicate with their environment and their fellow cells all the time with chemicals. Next it is important to know that cells also have receptors on their surfaces that allow them to communicate as well. Some of these receptors are specific in that that have a “don’t kill me” sign. There are actually sometimes dozens of “don’t kill me” signs that they can have. Last, it is important to know that cells can, when damaged in the right way not kill themselves and they can also get screwy in their signs and display “don’t kill me” even if they really need to be killed. Those abnormal cells will still divide as normal if they have the ability to do so and the two cells that come from it will be identical to the first one. So one abnormal cell is now 2 identical abnormal cells. That process can repeat forever in a living organism. This is essentially that clump of cells you are referring to. Often these cells were all from the same parent cell, we call them clonal (from one colony).
Next its important to realize that there are factors outside of random chance that can increase the odds of making a lot of very bad abnormal cells. Some of those include UV and chemicals like those found in cigarettes or asbestos etc.
Next, the last major player to avoid absolute catastrophe is the immune system. Your immune system is amazing but it has limits. Your immune system functions a bit like the police of a dystopian state. They kill everything is foreign, everything that is not functioning properly (e.g. growing too fast or eating too much) and everything that is sick (e.g. virus infected). But I mentioned those “don’t kill me” signs that cells can have. Those are normal signs but abnormal cells can show them even if they should be killed. This means that your last natural chance to kill bad cells can miss them.
Finally, it is important to realize that this is also a numbers game. The sheer number of cells in your body and their crazy number of things about them that are different depending on where they are (think stomach vs skin vs brain), what they normally do and at what age, sex or random genetic mutations you have makes this whole system seem impossible to alter at our choosing. For reference a billion cells fit inside the tip of an adult pinky.
The field of immuno-oncology (cancer immunotherapy) cropped up hoping to hijack this system but its been a rough field to find success. We learn more and more that cells have so many ways to tell the immune system to leave them alone. We think we find that a breast cancer has a lot of one sign and we make a drug against it and more of other signs come up in its place. Some of it is basic chance and some of survival by mutation. The more mutations that are made the more likely abnormal cells proliferate. Cancerous chemicals and UV increase that mutational burden and really hurts your bodies natural ability to kill abnormal cells. Essentially this is how we get cancerous cells and when enough of those cells exist, the normal functions of whatever organ they are in goes down and we will eventually succumb to them. So in the instance of cigarettes, our lungs, esophagus and circulatory systems are all sensitive and we cant live without breathing and having oxygen passed around inside our body.
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