[washadjeffmad]

Just for awareness, rodents used in research are genetically engineered to develop tumors whose rates and prevalence are well understood. When we do research, we study the changes and composition of the tumors, among other effects.

The rats will "get cancer" either way. How else would we know whether something has a positive or negative effect on tumor growth?

[willmadden]

I don’t see any reference to genetically engineering the rats to get cancer in the studies I linked. The results are terrifying in rodents.

[washadjeffmad]

A little more info on that: https://www.criver.com/eureka/evolving-mouse-model-cancer-re...

You might have to search for "transgenic" or other specific terminology to locate what model they used in the study, but they're assuredly not field mice or something you'd find in a pet store.

Here's a sample of a catalog: https://emodels.criver.com/search?term=*&species=Mouse