In mice
The migration from mouse models to human understanding is long and complex, and although it's a meme, "in mice" is a good shortcut for saying "This is a good start, but it's not ready to extrapolate into conclusions against the impact to human beings".
> "Mice smoke?"
The experiment summary: > "The team bred four strains of mice.
> They then exposed the mice to a single dose of the liver carcinogen diethylnitrosamine (DEN).
> DEN is found in tobacco smoke."
They simulated the "consequences" of smoking in mice.