In mice.

The research, conducted in a mouse model, suggests how lifestyle and genetics converge. The researchers found that animals with an APC mutation, the most common genetic mutation found in humans with colorectal cancer, developed cancer faster when fed a high-fat diet.

The mice with APC mutations developed benign growths called adenomas. In humans, adenomas are common in the intestine and are routinely removed during colonoscopies. These growths normally take decades to turn into malignant adenocarcinomas. Yet the adenomas in these mice quickly turned cancerous when given high-fat diets.