We thank E. Sahai, P. Scaffidi (The Francis Crick Institute) and V. Sanz-Moreno (Barts Cancer Institute) for scientific discussions, critical reading of the manuscript and sharing cell lines and mouse strains; M. Izquierdo (CSIC, Madrid) for sharing the CD63–GFP plasmid; E. Nye and the pathologists G. Stamp and E. Herbert from the Experimental Histopathology Unit at the Francis Crick Institute for histological processing and analysis support; J. Bee from the Biological Resources Unit at the Francis Crick Institute for technical support with mice and mouse tissues; R. Goldstone and A. Edwards from the Advanced Sequencing Facility at the Francis Crick Institute for technical support; M. Llorian-Sopena from the Bioinformatics and Biostatistics Unit at the Francis Crick Institute for helping with the RNA sequencing analysis; the Flow Cytometry Unit at the Francis Crick Institute, particularly S. Purewal and J. Cerveira, for invaluable technical help; the Cell Services Unit at the Francis Crick Institute; C. Moore (The Francis Crick Institute) for intra-tracheal injections; and I. Pshenichnaya, P. Humphreys, S. McCallum and Cambridge Stem Cell Institute core facilities for technical assistance. We acknowledge support from the FLI Core Facility Proteomics, which is a member of the Leibniz Association and is financially supported by the Federal Government of Germany and the State of Thuringia. This work was supported by the Francis Crick Institute, which receives its core funding from Cancer Research UK (FC001112), the UK Medical Research Council (FC001112), and the Wellcome Trust (FC001112) and the European Research Council grant (ERC CoG-H2020-725492); and by the Wellcome Trust—MRC Stem Cell Institute, which receives funding from the Sir Henry Dale Fellowship from Wellcome, the Royal Society (107633/Z/15/Z) and the European Research Council Starting Grant (679411).