Why are some chemicals carcinogens and other aren’t?

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Why are some chemicals carcinogens and other aren’t?

In: Biology
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The term chemical is really broad. A lot of things are chemicals. Cancer is typically caused by damage to the DNA of a cell so that when the cell divides it produces damaged copies of itself that don’t function correctly, often continuing to produce many damaged cells which form a tumour. Some chemicals cause this type of damage due to how they interact with cellular DNA, due to the particular properties of that specific chemical molecule they can get into the cell and damage it in a way to cause cancer, and others don’t.

A carcinogen is anything that’s thought to increase risk of cancer, but that can happen by a lot of different mechanisms. Ultimately it’s about how the chemical effects mutation rate in DNA, but it can do that by damaging DNA directly, by disabling certain mutation-correcting mechanisms, by increasing cell reproduction rate or by all sorts of other methods. A non-carcinogen is simply any chemical that *doesn’t* do something like that.

Carcinogens are chemicals that interfere with the cells reproduction and death cycles. There are genes that tell cells to reproduce and there are genes that suppress this process. Normally the expression of these genes is in balance and cells reproduce when conditions are right and are prevented from doing so the majority of the time.

A carcinogen can affect this balance in several ways. One way is to cause damage to the DNA directly or by reacting with the proteins and products that are involved in this process. The carcinogen may be affecting the regions that code for proteins that either tell the cell it’s time to start splitting or the regions that code for products that suppress division. If a cells DNA is too damaged it breaks down because nothing is getting done, let alone mitosis/meiosis or the self-death pathways kick in and it undergoes apoptosis.

If the tumor suppressing regions of DNA are damaged then cells keep dividing as long as it’s getting resources and not recognized by the immune system. This uncontrolled division leads to exponential reproduction of the same broken cell line, growing out of the tissue and potentially breaking off and travelling elsewhere in the body. Some of these cancerous cells are destroyed before they are able to multiply but not always. Cancerous cells aren’t rare but the body catches it early usually and kills it. With carcinogen exposure those incidents happens more often, and are therefore statistically more likely to actually become cancer.