"causes" is the troubling word there. From what I've read, in most people and animals tumors are growing all of the time due to cell replication defects, but normally the immune system gets rid of them. Cancer, as a disease, isn't "your body is making tumors", it's "your immune system isn't keeping up with your tumors".

From that point of view, anything which makes your immune system less effective "causes" cancer by making it harder for your immune system to kill tumor cells faster than they occur. Being cold all of the time, or being subjected to any type of chronic stress, certainly seems like it could do that.

This is a very good point. It is important for non-researchers to know that when you want to do a mouse (or rat, dog, or non-human primate) study, you have to decide what particular strain of mouse to buy. There are MANY options from Harlan, Charles River, etc, and each strain has its own genetic composition. Some of the strains are intentionally inbred, or intentionally outbred.

I think this variation might also be more important than some people are giving credit for. It is entirely possible to run a mouse study twice, confirming the results. Then, you can run the same protocol in a different strain and get no results or different results. Then, you have to try to understand which strain might be more applicable in a human population.