Researchers from the Spanish National Cancer Research Centre (CNIO) and the IDIBELL, led by Eva González-Suárez at the CNIO, have found that the hyperactivation of the RANK pathway plays a double function in breast cells: in the early stages of cancer, it activates senescence, which has a protective effect and delays the appearance of tumours; in more advanced stages, RANK-induced senescence favours the accumulation of stem cells, which promotes tumour growth and aggressiveness.