Culturing Human and Murine Cell Lines

K562 cells (provided by M. E. Hemler, Dana-Farber Cancer Institute, Boston, MA, USA) were cultured in RPMI 1640 medium supplemented with 10% (v/v) foetal calf serum (FCS; Lonza Bioscience) and 2 mM L-glutamine. Telomerase-immortalised HFF (provided by K. Clark, University of Leicester, Leicester, UK), conditionally immortalised MEF (generated in-house, see ref. ^{57 (link)}), A375-SM (provided by I. J. Fidler, MD Anderson Cancer Center, Houston, TX, USA) and osteosarcoma (U2OS; purchased from Sigma Aldrich, 92022711) cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% (v/v) FCS and 2 mM L-glutamine. MEF cells were supplemented with interferon-γ (Sigma-Aldrich). All cells were maintained at 37 °C in a humidified 5% (v/v) CO₂ atmosphere, except for MEF cells, which were maintained at 33 °C. All cell lines were frequently tested for mycoplasma and were negative. Cell lines were not authenticated and are not listed in the database of commonly misidentified cell lines maintained by ICLAC (http://iclac.org) and NCBI Biosample (http://www.ncbi.nlm.nih.gov/biosample).