if our skin cells are constantly dying and being replaced by new ones, how can a bad sunburn turn into cancer YEARS down the line?
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Picture your skin as being made up of tons of little sheets of paper. When they get damaged and/or fall off, those gaps are filled by copying other pieces of paper until you have enough sheets to fill it in. Normally you only need a few copies at a time. When you get burned you have an immediate problem that leads to the later problem.
The immediate problem is that you need a lot of copies at once so you have to make a lot more copies than normal. So if there’s a problem on one or two sheets, all of a sudden that problem is on 30 sheets instead as you’re copying them so fast to make up the gap and this kinda jank copy is all you have available to make copies from.
The later problem is that life goes on. Cells die in general, you get more sunburns, anything that means more copies have to be made. Well now there’s 30 copies of the paper with a little scribble on the corner. If one of *those* copies gets a smudge in the middle and gets sent to the printer, all of a sudden you have 30 papers with a scribble and 30 papers with a scribble and a smudge. After that its a scribble, smudge, and weird glare that makes parts of it hard to read.
Now repeat this again and again and you have the basic idea of how cells accumulate damage. Yeah that one sunburn when you were 12 probably isn’t gonna cause cancer on its own. But if you keep having burns and irritation and such, you’re going to have more and more chances for problems to be copied over in that spot
You have basal stem cells which are the cells that all the other cells divide from. The sun damages the basal stem cells and that damage is included in every cell that comes from them forever. Damage those cells a bunch and eventually some of the cells will be cancerous.
It’s not really the sunburn .. it’s being exposed to UV light that long to cause a sunburn can damage your DNA itself
Something I haven’t seen brought up by anyone else yet:
Your skin has different layers, the outermost of which is a mesh of dead skin cells and fats and oils and things, and the living layer deeper down. At the very bottom though is the layer of cells that produces new skin cells, periodically growing, dividing, and pushing the cells above them up as the outer layers fall off. This bottom layer stays in place though, and doesn’t move, just keeps dividing to make new skin cells. So if *these* cells are damaged, they’re going to keep that damage without being pushed upward and dying naturally, and therefore they can turn cancerous far down the line.
Presumably could a sunburn you received when you were like four or five years old end up being the genesis of a skin cancer diagnosis when you’re 80? Or would a cell that divided and evaded the body’s natural defenses more than likely amass enough momentum for a skin cancer diagnosis to be made much earlier if it was going to escalate to that point?
Cells are programmed to die as part of their natural life cycle. Many types of cancers are caused by cells losing their programmed ability to die.
Your skin, like every tissue in your body, has cells which tend to be reside in deeper layers. They aren’t actually there to provide the functions that you usually think about regarding skin function. Instead their job is to produce those skin cells. Those cells are sometimes called progenitors or even ‘adult stem cells’. While these cells divide to give rise to cells that will become your outer skin layers, that eventually flake off, they also maintain their numbers (when one cell divides into 2, the daughter cells each have different roles in that sense).
If one of those progenitors gets damaged enough, they may produce cells that can’t regulate themselves well and usually aquire further damage to genes along the way. Mostly your body detects these but sometimes they get through
Think of skin like you think of hair. Your hair is “constantly being replaced” by new hair, but the follicles at the base of the hair are not constantly being replaced. Damage your hair, grow new hair. Damage the follicles, problems happen. The sun damage happens to skin cells that are not the ones that are replaced.
A game of cellular cat and mouse:
Our cells come with inbuilt safety systems that can stop cancer developing.
Some of these systems stop our precious DNA from becoming damaged in the first place. For example, the sun’s UV rays can cause a build-up of oxygen-containing molecules inside cells that can damage DNA. This is why our cells make antioxidants to mop them up.
But even with this safety system in place, genetic mistakes can still crop up and, in fact, do so relatively regularly. After all, each time a cell divides it copies the 3 billion DNA ‘letters’ that make up its genetic code – a mammoth task to do error-free. And if a cell is exposed to lots of a cancer-causing substance, such as tobacco smoke, then its defences can be overwhelmed and DNA damage becomes inevitable.
That’s why cells also have proofreading machines that scan our DNA code, looking for faults and calling on molecular repair teams to fix any damage that’s found.
These very effective systems have evolved over billions of years, but they’re not foolproof, and mistakes can slip through the net. Sometimes a subtle genetic change might go unnoticed, or there could be so much damage that the repair machinery can’t cope. But even if this happens, there are further checks in place to stop the damaged cell from dividing and potentially leading to a cancer. For example, the cell can be forced to commit suicide so that it can’t pass on its faulty DNA to new cells.
But even then, on rare occasions, some damaged cells can slip past these checks.
That’s when the immune system swoops in, spying on cells that appear out of the ordinary and wiping them out. Frustratingly, cancer cells have evolved their own ways to defend from immune attack, such as dressing up in molecules that form an invisibility cloak. Ultimately, these can allow cancerous cells to evade destruction and go on to develop into the disease. But researchers are turning these tricks around and using them to their advantage, in the form of the latest immunotherapy treatments that can target certain cancers
Telomerase activity! If your somatic cells (most types) don’t degrade, they become IMMORTAL aka cancerous.
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