how does cancer work?


Let’s say someone is a cigarette smoker. Each time they light a cigarette, are they chancing the fact that it could contain the carcinogen that will start the cancer that will be an issue for them years later, or is it a gradual build up of carcinogens in the body eventually causing lung cancer? Like, could the hypothetical hot dog I’m eating right now be responsible for cancer years down the line?

In: 4

There is no way to know.

The correlation between cancer and cigarettes is statistical. If you smoke many cigarettes you are more likely to get cancer than if you don’t. It’s not like “these 3 cigarettes” were the lucky ones (unlucky ones?) that gave you cancer.

Cancer susceptibility is a function of genetics and the whole life of environment you’ve experienced.

A carcinogen is in every cigarette. If it causes the bad type of damage or not is random.

Cancer happens when a cell is damaged in a very specific way. It’s growth control must break, it’s self-destruct must break, and it must still be considered a healthy cell by your immune system.

Each time a cell is exposed to a carcinogen it causes random damages. But if only one or two of the things are true the cell will just die and be replaced by a healthy cell. But if all these things happen you have a cell that grows out of control and your immune system doesn’t recognize it as problematic I.E. a tumor grows.

So the more you’re exposed to carcinogens the higher the chance that something bad happens somewhere.

Biologist here, and my answer is similar to Luckbot’s.

All cigarettes have carcinogens. Carcinogens causes damages to cells, specifically to their DNA, which is like the blueprint for creating proteins. Some types of damage in particular regions of the cell’s DNA can cause unregulated growth and division (cancer). Organisms have a bunch of checkpoints that check for damaged DNA to prevent damaged DNA from being replicated and creating more cells with the same damaged DNA. When those checkpoints fail and that compromised cell divides, that’s when you risk cancer.

So, in general, all cigarettes have carcinogens that can damage DNA in cells. However, not every damaging incident will cause cancer. But the more you smoke, the more times you take that risk, and the more likely you are to develop cancer. Same for your hot dog—there’s a chance, but you’ll probably be fine, unless you eat a ridiculous amount of hot dogs. There are tons and tons of known carcinogens, you can’t avoid them all. All you can do is avoid taking unnecessary risks. UV light, aka the sun’s rays, is also a carcinogen. It damages DNA. That’s why it’s a bad idea to use tanning beds, and why you should wear sunblock when you’re going to be in the sun for extended periods of time. We can’t realistically avoid all UV radiation, but you have a far lesser chance of developing skin cancer if you wear sunblock and don’t lay in UV tanning beds.

At each point of cell devision a cell performs checks to ensure that all the DNA is still good and the cell is still capable of performing this function. If it fails these checks then the cell undergoes apoptosis or cell death.

However if those checks fail then the unhealthy cell reproduces and passes down its damaged mutations. If that mutation causes the signal to reproduce to remain on then you have a cancerous cell. (This is not ALWAYS a error in the go signal, some cells reproduce in response to deficiencies or injuries so sometimes it is an error in detecting these situations.)

Carcinogen is just a generic term for “any mutagen that can cause cancer-causing mutations.” And just because you have a cell with the cancer-causing mutation does not mean you will get cancer. Your body has specialized immune cells designed to hunt and kill cells that are not functioning correctly either due to mutations or viral infections and they tend to find cancer cells pretty quickly before they can reproduce, it is only when those cells reproduce to the point where the natural killer cells cannot remove them faster than they reproduce that tumors form.

My epidemiologist wife explained it to me (an engineer) so i think i can do a good ELI5 explanation.


Cells will naturally self destruct over time. Just a part of life and they are replaced by new cells.


Mitosis causes cell division. Every time that occurs, you chance making a cell without the ability to self destruct. That cell can still reproduce (mitosis) and now it makes more cells without the ability to self destruct.


Certain things (some known, some unknown) causes mitosis to occur more often. Smoking damages lung cells and causes more mitosis to replace those damaged cells.


The more frequent the mitosis, the more likely that eventually you make a cell that cannot self destruct. Those cells are cancer cells.


Apologies to the biologists if I just made your head explode by oversimplifying it.