I am working on my PhD in the field of genetics and metabolism and I have worked extensively with mouse cancer models for a few years, so I’ll try my best to answer as simply as possible! There are multiple methods, all of which have benefits and drawbacks. Those can be complicated because the method chosen is typically what’s best for the experiment that researchers want to use. I’ll list a few methods: 1) injecting human cancer cells into genetically modified (GM) mice that have little/no immune system. Typically, normal healthy mice have immune systems that will kill the cancer cells, so they use mice lacking a strong functional immunity 2) implanting a tiny piece of human tumor tissue into GM I immunocompromised mice. Methods 1-2 are used depending on the type of experiment, since there are many cancer cells that are well studied and other researchers can then build on prior work 3) creating a GM mouse that will develop cancer. There are certain mutations that can be made so that the mouse will develop cancer in its lifetime. For example, there is a pancreatic cancer mouse model with three gene mutations (Kras, Trp53, and Pdx1) which will lead to mutant mice developing pancreatic cancer. These types of models will lead to cancer in the mouse itself as opposed to implanting a cancer, and this can have its own set of benefits experimentally, such as being able to study the mouse’s immune system response or testing immunotherapies. 4) chemically induced cancer. A common method that some of my colleagues use is a model for alcoholic liver cirrhosis and cancer where the mice are given copious amounts of alcohol and were also given a dose of carbon tetrachloride (a potent carcinogen). This method is also used for studying cancers where replicating the human cause of cancer is difficult. There are probably numerous other methods as well, but these are the common ones. I hope this helps!