Discarded rubbish from tumours could trigger nearby healthy cells to become malignant.

Many cells shed exosomes: membrane-bound packages of proteins, DNA and RNA that are thought to be a waste-management system. Raghu Kalluri at the University of Texas MD Anderson Cancer Center in Houston and his colleagues found that exosomes from cancer cells contain the building blocks for short RNA fragments that can shut off gene expression. Healthy cells that were exposed to cancer exosomes in culture caused tumours when the cells were later injected into mice, whereas cells exposed to normal exosomes did not.

Samples of exosomes from people with breast cancer also caused tumours in 5 out of 11 mice treated. This finding could aid the discovery of markers for disease progression, or even represent a route to new cancer therapies.

Cancer Cell http://doi.org/wkg (2014)