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?



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

Cancer cells result from mutations that disable the things that keep cell growth in check. Those mutations come from incorrect repairs to cell DNA, and those errors happen more frequently the more repairs take place.

Therefore things that cause damage that requires repairs increase the chances of developing cancer, stuff like cigarettes, asbestos, and sun exposure.

The cells in our body reproduce regularly and based off of a genetic map. That genetic map can naturally become distorted and cause cells to reproduce uncontrollably, becoming cancerous growths known as tumors.

A “carcinogen” is a substance (certain types of radiation, chemicals, etc.) that can basically screw up that genetic map much faster than would naturally occur in an otherwise healthy person. Cigarette smoke has a lot of carcinogens, both from radioactive sources and from certain chemicals. Energy from the sun is also radioactive – a lot of the more harmful light is filtered out in the atmosphere but you can still receive dangerous doses if you’re outside all the time without protection on.

Those things damage your DNA. Your DNA is an instruction set on how to build cells.

If the right bits of DNA are damaged, then your body will read the wrong instructions and build heaps of useless cells, and that is called Cancer

Every time your cells split theres a very small chance that something goes wrong and it becomes a cancerous cell instead of a healthy cell.

Those carcinogens damage cells, and force your body to get rid of them, and for another cell to split to replace it. Since they increase the number of cell splits, they increase your risk of cancer.

A lot of people are saying stuff like carcinogens are the cause and mutations and etc without actually answering the question

Sun releases ionizing radiation which can knock electrons out in the DNA, thus changing it

Chemicals can cause stuff like DNA methylation to happen where the transcription and translation process of the DNA get affected so new cells can get made incorrectly etc

Instead of a bunch of cells that don’t want to die, think of it more like a bunch of cells that have had their self-destruct button broken, or the wiring from the self-destruct button to the “reactor” broken. Because that self destruct signal either is not being received or not being carried out properly, the cells keep growing & replicating in an uncontrolled manner.

Carcinogens (or things that cause cancer) like smoking, UV radiation, etc., are the things breaking the self destruct.

Imagine you are told a long paragraph (it’s simple enough to remember but there exists no copy of it, written or otherwise) and I task you with writing down, over and over again. Each time you write it, the previous write ups cease to exist. You basically just keep writing. How much would you be willing to bet that after a year, the paragraph you write will be the exact same as the initial one given (ie exact word placement [frameshift mutations], properly spelled [nonsense/missense/silent mutation], etc)?

When a cell replicates, that’s basically what happens. The cell divides based off the DNA framework of the parental cell. The downstream effect are felt when the cell has to divide over and over and over again (DNApol has copy error rates). So after hundreds/thousands of replications, you begin getting accumulations of “cancer-like” cell health profiles.

So back to your original question. Certain things cause cells to die, and your body tends to have a homeostasis (basically a point of balance) drive to have certain cells in certain places. So when you take in some of these chemicals that kill cells, you are basically encouraging your body to divide cells in the affected regions (lungs for cigarettes, skin for sun, wiping to hard to colorectal, etc.), thus you are encouraging replication errors to occur more often than let’s say someone who does not do those behaviors.


In addition to the DNA damage aspect, these things cause irritation and inflammation. Inflammation helps promote cell replication thus allowing cells with damaged DNA to divide more.

Your body makes about 200 cancer cells per day, your immune system is really good at fighting those cells before they metastasize. When you are doing something damaging to your body that’s in bed of constant repair, your immune system is distracted by the extra work and those cancer cells slip by unnoticed. Smoking, drinking, inhaling impurities, stressing out, not getting enough rest are all things that cause damage that can be mostly avoided.

Generally, there’s a chance anybody can get any type of cancer. What causes development of cancer are mutations (mistakes) in the creation of new cells. Environmental factors like the ones you listed increase the probability of these mistakes occuring. This doesn’t mean that a smoker *will* or *will not* get lung cancer, it just statistically increases the odds of it happening.

I think the most confusing part about cancer for many people is the statistics that explain it and how environmental factors affect it’s probability, not certainty. Many sensational pieces like “x causes cancer” are products of a wrongful manipulation of statistics.


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.

I worked as a software developer for my best friend while he was doing his PhD studies at UT Southwestern for Nuclear Physics. His grant was on breast cancer research. His research was on cataloging various types of cancer, particularly on the breast tissue and then see if we could find alternate ways of treatment, including of course radiation therapy.

Our test subjects were various lab animals, for the most part lab rats.

Anyway, after 3 years working close to him in his research I developed a conclusion that seems to have some fundament on it.

Imagine you have a copy machine, it is of the best quality possible, makes as precise copies as you can imagine. You are asked to make copies with a caveat. You can never make copies using the same original. In fact, your copy has to be made from the latest copy, and the next copy from the latest copy and so on.

Lets call your original copy the “stem copy” and you will only get to use it once.

The first few copies look identical. There is no deviation from the original, but as you keep on making copies, small imperfections appear. Some dust got on the glass, and that made it to the copy, you cleaned the glass, but since you cant make a copy out of the original, all subsequent copies will have that little piece of lint or spec of dust that made it to the glass.

Then the paper shifts just so, so now the copy is shifted and with a spec of dust.
At some point the copies definitely look different from the original so you start shredding them.

Cancer is like this, our body cells are constantly regenerating due to various processes. In a normal lifecycle this is not a problem, but if tissue or an organ or anything has to be constantly regenerated due to an illness, the body will eventually start making bad copies and the own body defenses will start attacking the bad copies because now they look like foreign agents, like disease.

Asbestos is a good example. Asbestos fibers get incrusted deep into the lung tissue, the body tries to remove it but it cant. Minuscule damage is done to the tissue that the body is constantly trying to repair… until it makes a mistake.

The common denominator seems to be a wound that has to be constantly healed. Like cancer of the skin… overexposure to the sun… do this enough times and you get a melanoma.

Drinking for the liber, tobacco on the lungs and so on.

A more recent proposed mental model for understanding cancer comes from observing that cancer cells behave like much more primitive cells, and act in their own interest rather than in the interest of the organism. The idea is that harmful substances injure the cell to the point where instead of booting the cell’s assigned OS and operating accordingly, so to speak, it goes into kernel panic mode, and operates like a bacterium, having forgotten that it is supposed to operate as part of a larger organism. Those ultra primitive functions include proliferation and cell division, but lack the regulatory functions that make it participate in the over-all functioning of the organism. Part of that proper behavior is that certain cells trigger cell suicide when their continued activity harms the organism. There is evidence that supports this interpretation, but as with anything as complicated, it is controversial.

See this: [A New Theory on Cancer: What We Know About How It Starts Could All Be Wrong](https://www.newsweek.com/2017/07/28/cancer-evolution-cells-637632.html)


Let me try and really ELI5 this.

Let’s pretend a group of friends is building a neighborhood of houses. Each friend has got a huge book of instructions that tell them everything they need to know about building the houses, and how each of them should fit into the neighborhood. This book even tells them how many new friends you need to invite, and when.

The friends want to keep this neighborhood absolutely brand spanking new, so new in fact, that they demolish houses once they get old, and build new ones to make up for these old ones. The big book of instructions also explains how to do this so there’s always have the correct number of houses.

Each friend is responsible for building just one house, and then they live in it. Also, each friend gets their own big book of instructions. When the house is removed because it got old, and the friend is going to leave the neighborhood with their book, the book instructs them to invite a new friend to the neighborhood to build a house. The old friend is gong to keep his copy of the book, and so copies the book by hand, to give to the new friend.

cigarettes, asbestos, and the sun are like smudges and coffee stains in the big book of instructions. Often the friend can work out what the words or letters should be, and correctly copy them. But over time the errors slowly build up.

Eventually the book can become so incorrect that the friend reading it thinks it says, “Invite a new friend to build a house next to you, then DON’T remove you’re own house”. The DON’T is the error that has arrived over time.

So now not only do we have 2 houses where we should only have one, we’ve got 2 friends with a bad copy of the book! Both these friends will now invite 2 more friends, and not remove themselves. So now we’ve got 4 houses where there should only be one, and 4 friends with bad book copies! And so on.

These friends are now really stressed. They’ve got houses built all over each other, and this stress is causing them to copy the book badly. They’re making more mistakes than they normally would. The books are now telling them to invite a new friend every day. To build lots of roads to allow all these new friends to reach them. To order in takeaways constantly to feed all these friends. To tell the friend from the other side of town who’s come to help the situation, to get lost.

So now in the north-west corner of the neighborhood we’ve got a clump of houses and friends that aren’t doing what they are supposed to be doing. And this clump is growing rapidly.

Although dangerous, this clump of houses isn’t enough to destroy the neighborhood. However, if one of those friends living in the clump gets an error in his book that tells him to get in his car, and drive to a new area of the neighborhood, and how to avoid the friends trying to help on the way, we’ve got a big problem.

Everyone has cancerous cells all the time. Errors copying DNA, or damage to the copy and repair machinery cause it. Some damage triggers a self destruct for the cells, and some triggers rapid growth.

Our white blood cells can smell most of the unrepairable cells, but can only eat so many of them at once. Also, sometimes, the fast growing cells break loose and stick somewhere else, which takes a while to build up enough cancer smell for white blood cells to find.

Radiation, some chemicals, and some viruses greatly increase those problems. They can reduce WBC effectiveness and replication, increase cell damage, etc.

With enough random hits, some of those cancer cells cannot be smelled. Those can grow without being attacked by the body at all. We treat that by:

* targeted beams of radiation from many directions so only a central point gets a lethal dose, killing the core of a large tumor.
* drugs that cross-link DNA so your cells cannot replicate. It takes time for your cells to fix this. Any cell that needs to repair or replace itself before fixed will die. Cancer cells, stomach lining, and hair follicles need to do that way more often, and are more likely to die. Some good cells all over die too.
* newer drugs also can smell cancers and poison them more than normal cells.
* Custom made viruses can target some types of cancer cells
* there are some other drug types too

In all of those treatments, some cells can stay half broken and do not die, leading to more cancer years later.

I have always thought of this as winning the lottery. Just that the prize is something you don’t really want. The more unhealthy you live, the more bad habits that you have, the more entries you have in that lottery.

You don’t know which cell is going to one day get damaged enough to escape your body’s natural elimination system so it’s best that you maintain a healthy lifestyle.

In the end, it’s all probability and how badly the universe wants to fuck you. You cannot control the universe so try to control the probability.