Cells that eventually give rise to tumours attract immune cells that help to shield them from the body's defences. This may be one of the earliest events in tumour formation.

Bin Zhao at Zhejiang University in Hangzhou, China, and his colleagues studied liver cancer in mice and found that tumour-initiating cells (TICs) turn on production of Yes-associated protein (YAP). This molecule promotes cell proliferation and attracts immune cells called macrophages, which boost tumour growth. The TICs began doing this at an early stage of tumour growth, when they existed as single cells.

Blocking macrophage recruitment prevented TICs from developing into tumours and caused the immune system to eliminate them rapidly. The team also discovered YAP activation and macrophage recruitment in a small sample of precancerous lesions from human livers, suggesting that similar mechanisms might be involved in some human cancers.

Targeting YAP or macrophages could be a therapeutic strategy for liver cancer, the authors suggest.

Genes Dev. http://doi.org/b2jc (2017)