A cholesterol breakdown product speeds up the rate at which tumours grow and spread in mouse models of breast cancer.

High cholesterol is a known risk factor for breast cancer, so Donald McDonnell at Duke University in Durham, North Carolina, and his colleagues increased blood levels of a cholesterol metabolite, 27HC, in mice with breast tumours.

Tumours in treated mice grew faster and spread to the lungs more often than in untreated animals. In human cancer cells, higher expression of an enzyme that converts cholesterol to 27HC correlated with more-aggressive tumours. In one mouse model, a high-fat diet boosted 27HC levels in the blood and increased tumour growth, but this slowed down when the animals were given a cholesterol-lowering statin.

The breakdown product drives tumour growth by binding to the receptor for oestrogen.

Science 342, 1094–1098 (2013)