system
Given the following post, respond as if you're commenting on Reddit:
human
Why don't researchers introduce cancer to colonies of bacteria repeatedly until they evolve a way to defeat it? Then copy their solution?
gpt
(dumping it down a bit, this is just the major concepts, there are many exceptions)

Cancer is beneficial to the cell it affects, so single celled organisms are unaffected by it. Cancer is basically cells that have mutated to ignore all signals that would cause the cell to commit suicide (such as rapid growth in places it's not supposed to be). 

The problem occurs when that single cell is located in a complex multi-celled organism (all animals and plants). These organisms are characterized by having cells performing different functions, all dependent on each other. You have different cells in your skin, muscles, nerves, fat, liver etc. all performing different functions. There's at least 210 cell types in humans, and their location is crucial to their function too (you want lung cells in your lung and liver cells in your liver). 
Due to the complexity of this, there's multiple safeguards to prevent cells from growing places they are not supposed or if they start behaving in a way they are not supposed to, and to make them commit suicide if they do.

Problem with cancer is that ONE cell of one of these cell types mutate in a way so that it circumvents these safeguards.

It will keep growing, eventually suppressing all the normal cells. It might also have cells break off the tumor, travel with the blood to other parts of the body and then start a new tumor there. This causes the organism as a whole to cease functioning and then die.

Problem with your question is that bacteria colonies doesn't have this complexity. It's just a bunch of the same bacteria clumped together. There's no dependency on other cells or structure to the colony, so 1 rampant bacteria wont kill of the colony but rather make it stronger, leaving no evolutionary advantage to prevent it.