IVIS imaging

Images were acquired with a Xenogen IVIS Imaging System (Perkin Elmer, 200 Series) and Living Image software (RRID:SCR_014247), version 4.3.1 at a medium binning level and the field of view set at ‘E’. For in vivo imaging, mice were placed into the IVIS with front limbs taped above head and black shields used to block bioluminescence from the primary tumors to visualize metastases in vivo. Exposure time for photon flux quantification of primary tumors, a primary outcome measure, was 0.2 s. After in vivo imaging, dissected organs were imaged ex vivo to detect metastatic foci, a primary outcome measure. Images were taken at multiple exposures (0.2 s, 0.5 s, 1 s, 10 s, 20 s, 60 s, and 120 s) and used to manually quantify visible metastatic foci. Quantification was performed blinded to the cells the animals were injected with. Image files are available at https://osf.io/bq54u/.