Eli5 How does Chemotherapy work? Does it increase the oxygen in cancer cells? How does that kill them?


Eli5 How does Chemotherapy work? Does it increase the oxygen in cancer cells? How does that kill them?

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It depends. Chemotherapy is a generic term for any drug used to treat cancer, and each drug is going to work differently.

At a high level, the idea is that the drugs disrupt the cell’s ability to make copies of itself. As all cells have a life cycle, a cell that can’t make copies of itself will eventually die out without producing more cells. Eventually, this means that the cells will die off entirely.

Cancer cells are very fast-reproducing cells, so the idea is that you administer the chemotherapy drugs to disrupt their reproduction cycle, but stop before those drugs cause _too_ much damage to other, healthy cells. Bascially, you hope the cancer dies off before everything else. This is why chemotherapy causes hair loss and stomach issues – these are _also_ fast-reproducing cells that are strongly affected by the chemotherapy.

Chemotherapy is any chemical that treats cancer. The name was historically used to distinguish it from the cancer therapies used before the 1940’s which were surgery or radiation.

Chemotherapy drugs have many different mechanisms of action. But all of them kill cancer cells more than they kill healthy cells. For example they might target cells that are dividing which would affect both healthy and cancerous cells, but especially the cancerous cells since they divide more than healthy cells.

The first chemo drugs were actually dilute chemical weapons from WWI/II since they worked by damaging DNA in replicating cells, causing those cells to die. In small enough doses you could survive the treatment while killing many of the cancer cells. Many chemo drugs are still this brutal, but new more targeted treatments are also available like drugs that target specific proteins cancer cells use, or antibodies and modified immune cells that kill cancer cells using the immune system.

Chemotherapy is a broad term that is used to describe the practice of using drugs to treat cancer (as opposed to radiation and surgery). There are a ton of different ways that chemo works, including messing with DNA directly so cells can’t replicate, stopping tumors from creating new blood supplies, stopping tumors from being able to hide themselves from the immune system, blocking hormone signaling that would cause further tumor cell growth, stopping parts of the signaling pathway that would eventually cause more cell replication, and some other ways.

There is a ton of research being done in cancer drug development and new ones come out all the time.

Let me give you a few real world examples.

Temozolmide is a drug that attacks DNA. It cases direct DNA damage by adding some extra atoms to the “G” in DNA (remember DNA consists of nucleotides abbreviated as A, T, G and C). Cancer cells are dividing fast, so they need to copy their DNA very often, but now they are also busy fixing the damage. This damage is very bad for them but temozolmide damages the normal cells DNA too, that’s why you have severe side effects.

Paclitaxel attacks an important protein that is used by the cell while cell division. This protein (called tubulin) has an important role in pulling apart the two dividing cells. Paclitaxel makes tubulin rigid so it cannot do it’s function and thus cells cannot divide. As cancer cells are fast dividing, they are badly affected, but all good cells suffer too. That causes side effects.

Actinomycin D is sticking to the DNA and doesn’t allow the DNA copying mechanisms work, like a roadblock. As cancer cells are dividing fast, the rest you know…

Actually quite many chemotherapeutic agents attack DNA somehow. Either direct damage to the DNA (so the cells are busy fixing) or blocking a process that is needed for DNA replication (so they cannot divide).